1
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Tam B, Babacan O, Kafizas A, Nelson J. Comparing the net-energy balance of standalone photovoltaic-coupled electrolysis and photoelectrochemical hydrogen production. Energy Environ Sci 2024; 17:1677-1694. [PMID: 38449570 PMCID: PMC10913155 DOI: 10.1039/d3ee02814c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 01/12/2024] [Indexed: 03/08/2024]
Abstract
Photovoltaic-coupled electrolysis (PV-E) and photoelectrochemical (PEC) water splitting are two options for storing solar energy as hydrogen. Understanding the requirements for achieving a positive energy balance over the lifetime of facilities using these technologies is important for ensuring sustainability. While neither technology has yet reached full commercialisation, they are also at very different technology readiness levels and scales of development. Here, we model the energy balance of standalone large-scale facilities to evaluate their energy return on energy invested (ERoEI) over time and energy payback time (EPBT). We find that for average input parameters based on present commercialised modules, a PV-E facility shows an EPBT of 6.2 years and ERoEI after 20 years of 2.1, which rises to approximately 3.7 with an EPBT of 2.7 years for favourable parameters using the best metrics amongst large-scale modules. The energy balance of PV-E facilities is influenced most strongly by the upfront embodied energy costs of the photovoltaic component. In contrast, the simulated ERoEI for a PEC facility made with earth abundant materials only peaks at 0.42 after 11 years and about 0.71 after 20 years for facilities with higher-performance active materials. Doubling the conversion efficiency to 10% and halving the degradation rate to 2% for a 10-year device lifetime can allow PEC facilities to achieve an ERoEI after 20 years of 2.1 for optimistic future parameters. We also estimate that recycling the materials used in hydrogen production technologies improves the energy balance by 28% and 14% for favourable-case PV-E and PEC water splitting facilities, respectively.
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Affiliation(s)
- Brian Tam
- Department of Physics, Imperial College London South Kensington London SW7 2AZ UK
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London White City London W12 0BZ UK
| | - Oytun Babacan
- Grantham Institute - Climate Change and the Environment, Imperial College London South Kensington London SW7 2AZ UK
| | - Andreas Kafizas
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London White City London W12 0BZ UK
- Grantham Institute - Climate Change and the Environment, Imperial College London South Kensington London SW7 2AZ UK
| | - Jenny Nelson
- Department of Physics, Imperial College London South Kensington London SW7 2AZ UK
- Grantham Institute - Climate Change and the Environment, Imperial College London South Kensington London SW7 2AZ UK
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2
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Meng Z, Pastor E, Selim S, Ning H, Maimaris M, Kafizas A, Durrant JR, Bakulin AA. Operando IR Optical Control of Localized Charge Carriers in BiVO 4 Photoanodes. J Am Chem Soc 2023; 145:17700-17709. [PMID: 37527512 PMCID: PMC10436276 DOI: 10.1021/jacs.3c04287] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Indexed: 08/03/2023]
Abstract
In photoelectrochemical cells (PECs) the photon-to-current conversion efficiency is often governed by carrier transport. Most metal oxides used in PECs exhibit thermally activated transport due to charge localization via the formation of polarons or the interaction with defects. This impacts catalysis by restricting the charge accumulation and extraction. To overcome this transport bottleneck nanostructuring, selective doping and photothermal treatments have been employed. Here we demonstrate an alternative approach capable of directly activating localized carriers in bismuth vanadate (BiVO4). We show that IR photons can optically excite localized charges, modulate their kinetics, and enhance the PEC current. Moreover, we track carriers bound to oxygen vacancies and expose their ∼10 ns charge localization, followed by ∼60 μs transport-assisted trapping. Critically, we demonstrate that localization is strongly dependent on the electric field within the device. While optical modulation has still a limited impact on overall PEC performance, we argue it offers a path to control devices on demand and uncover defect-related photophysics.
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Affiliation(s)
- Zhu Meng
- Department
of Chemistry and Centre for Processible Electronics, Imperial College London, London W12 0BZ, United
Kingdom
| | - Ernest Pastor
- IPR−Institut
de Physique de Rennes, CNRS-Centre National
de la Recherche Scientifique, UMR 6251 Université de Rennes, 35000 Rennes, France
| | - Shababa Selim
- Department
of Chemistry and Centre for Processible Electronics, Imperial College London, London W12 0BZ, United
Kingdom
| | - Haoqing Ning
- Department
of Chemistry and Centre for Processible Electronics, Imperial College London, London W12 0BZ, United
Kingdom
| | - Marios Maimaris
- Department
of Chemistry and Centre for Processible Electronics, Imperial College London, London W12 0BZ, United
Kingdom
| | - Andreas Kafizas
- Department
of Chemistry and Centre for Processible Electronics, Imperial College London, London W12 0BZ, United
Kingdom
- London
Centre for Nanotechnology, Imperial College
London, London SW7 2BP, United Kingdom
| | - James R. Durrant
- Department
of Chemistry and Centre for Processible Electronics, Imperial College London, London W12 0BZ, United
Kingdom
| | - Artem A. Bakulin
- Department
of Chemistry and Centre for Processible Electronics, Imperial College London, London W12 0BZ, United
Kingdom
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3
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Nasser SMT, Rana AA, Doffinger R, Kafizas A, Khan TA, Nasser S. Elevated free interleukin-18 associated with severity and mortality in prospective cohort study of 206 hospitalised COVID-19 patients. Intensive Care Med Exp 2023; 11:9. [PMID: 36823262 PMCID: PMC9949911 DOI: 10.1186/s40635-022-00488-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 12/19/2022] [Indexed: 02/25/2023] Open
Abstract
BACKGROUND Divergence between deterioration to life-threatening COVID-19 or clinical improvement occurs for most within the first 14 days of symptoms. Life-threatening COVID-19 shares clinical similarities with Macrophage Activation Syndrome, which can be driven by elevated Free Interleukin-18 (IL-18) due to failure of negative-feedback release of IL-18 binding protein (IL-18bp). We, therefore, designed a prospective, longitudinal cohort study to examine IL-18 negative-feedback control in relation to COVID-19 severity and mortality from symptom day 15 onwards. METHODS 662 blood samples, matched to time from symptom onset, from 206 COVID-19 patients were analysed by enzyme-linked immunosorbent assay for IL-18 and IL-18bp, enabling calculation of free IL-18 (fIL-18) using the updated dissociation constant (Kd) of 0.05 nmol. Adjusted multivariate regression analysis was used to assess the relationship between highest fIL-18 and outcome measures of COVID-19 severity and mortality. Re-calculated fIL-18 values from a previously studied healthy cohort are also presented. RESULTS Range of fIL-18 in COVID-19 cohort was 10.05-1157.7 pg/ml. Up to symptom day 14, mean fIL-18 levels increased in all patients. Levels in survivors declined thereafter, but remained elevated in non-survivors. Adjusted regression analysis from symptom day 15 onwards showed a 100 mmHg decrease in PaO2/FiO2 (primary outcome) for each 37.7 pg/ml increase in highest fIL-18 (p < 0.03). Per 50 pg/ml increase in highest fIL-18, adjusted logistic regression gave an odds-ratio (OR) for crude 60-day mortality of 1.41 (1.1-2.0) (p < 0.03), and an OR for death with hypoxaemic respiratory failure of 1.90 [1.3-3.1] (p < 0.01). Highest fIL-18 was associated also with organ failure in patients with hypoxaemic respiratory failure, with an increase of 63.67 pg/ml for every additional organ supported (p < 0.01). CONCLUSIONS Elevated free IL-18 levels from symptom day 15 onwards are associated with COVID-19 severity and mortality. ISRCTN: #13450549; registration date: 30/12/2020.
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Affiliation(s)
- Syed M. T. Nasser
- grid.451052.70000 0004 0581 2008Intensive Care Department, Surrey and Sussex NHS Foundation Trust, Redhill, UK ,grid.416224.70000 0004 0417 0648Present Address: Intensive Care Department, Royal Surrey County Hospital, Egerton Road, Guildford, GU2 7XX UK
| | - Anas A. Rana
- grid.6572.60000 0004 1936 7486Centre for Computational Biology, Birmingham University, Birmingham, UK
| | - Rainer Doffinger
- grid.24029.3d0000 0004 0383 8386Department of Clinical Biochemistry and Immunology, Cambridge University Hospitals NHS Trust, Cambridge, UK
| | - Andreas Kafizas
- grid.7445.20000 0001 2113 8111The Grantham Institute for Climate Change and the Environment, Imperial College London, South Kensington, London, UK ,grid.7445.20000 0001 2113 8111Department of Chemistry, Molecular Science Research Hub, Imperial College London, White City, London, UK
| | - Tauseef A. Khan
- grid.17063.330000 0001 2157 2938Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Shuaib Nasser
- grid.24029.3d0000 0004 0383 8386Department of Allergy, Cambridge University Hospitals NHS Trust, Cambridge, UK
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4
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Anagnostopoulou M, Zindrou A, Cottineau T, Kafizas A, Marchal C, Deligiannakis Y, Keller V, Christoforidis KC. MOF-Derived Defective Co 3O 4 Nanosheets in Carbon Nitride Nanocomposites for CO 2 Photoreduction and H 2 Production. ACS Appl Mater Interfaces 2023; 15:6817-6830. [PMID: 36719032 DOI: 10.1021/acsami.2c19683] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
In photocatalysis, especially in CO2 reduction and H2 production, the development of multicomponent nanomaterials provides great opportunities to tune many critical parameters toward increased activity. This work reports the development of tunable organic/inorganic heterojunctions comprised of cobalt oxides (Co3O4) of varying morphology and modified carbon nitride (CN), targeting on optimizing their response under UV-visible irradiation. MOF structures were used as precursors for the synthesis of Co3O4. A facile solvothermal approach allowed the development of ultrathin two-dimensional (2D) Co3O4 nanosheets (Co3O4-NS). The optimized CN and Co3O4 structures were coupled forming heterojunctions, and the content of each part was optimized. Activity was significantly improved in the nanocomposites bearing Co3O4-NS compared with the corresponding bulk Co3O4/CN composites. Transient absorption spectroscopy revealed a 100-fold increase in charge carrier lifetime on Co3O4-NS sites in the composite compared with the bare Co3O4-NS. The improved photocatalytic activity in H2 production and CO2 reduction is linked with (a) the larger interface imposed from the matching 2D structure of Co3O4-NS and the planar surface of CN, (b) improvements in charge carrier lifetime, and (c) the enhanced CO2 adsorption. The study highlights the importance of MOF structures used as precursors in forming advanced materials and the stepwise functionalization of the individual parts in nanocomposites for the development of materials with superior activity.
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Affiliation(s)
- Maria Anagnostopoulou
- Institut de Chimie et Procédés Pour l'Energie, l'Environnement et la Santé, (ICPEES) UMR7515 CNRS, ECPM, University of Strasbourg, 25 rue Becquerel Cedex 2, Strasbourg 67084, France
| | - Areti Zindrou
- Department of Physics, University of Ioannina, Ioannina 45110, Greece
| | - Thomas Cottineau
- Institut de Chimie et Procédés Pour l'Energie, l'Environnement et la Santé, (ICPEES) UMR7515 CNRS, ECPM, University of Strasbourg, 25 rue Becquerel Cedex 2, Strasbourg 67084, France
| | - Andreas Kafizas
- Department of Chemistry, Molecular Science Research Hub, Imperial College London, White City, London W12 0BZ, United Kingdon
| | - Clément Marchal
- Institut de Chimie et Procédés Pour l'Energie, l'Environnement et la Santé, (ICPEES) UMR7515 CNRS, ECPM, University of Strasbourg, 25 rue Becquerel Cedex 2, Strasbourg 67084, France
| | | | - Valérie Keller
- Institut de Chimie et Procédés Pour l'Energie, l'Environnement et la Santé, (ICPEES) UMR7515 CNRS, ECPM, University of Strasbourg, 25 rue Becquerel Cedex 2, Strasbourg 67084, France
| | - Konstantinos C Christoforidis
- Institut de Chimie et Procédés Pour l'Energie, l'Environnement et la Santé, (ICPEES) UMR7515 CNRS, ECPM, University of Strasbourg, 25 rue Becquerel Cedex 2, Strasbourg 67084, France
- Department of Environmental Engineering, Democritus University of Thrace, Xanthi 67100, Greece
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5
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Bullen JC, Heiba HF, Kafizas A, Weiss DJ. Parasitic Light Absorption, Rate Laws and Heterojunctions in the Photocatalytic Oxidation of Arsenic(III) Using Composite TiO 2 /Fe 2 O 3. Chemistry 2022; 28:e202104181. [PMID: 35114042 PMCID: PMC9306794 DOI: 10.1002/chem.202104181] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Indexed: 11/08/2022]
Abstract
Composite photocatalyst‐adsorbents such as TiO2/Fe2O3 are promising materials for the one‐step treatment of arsenite contaminated water. However, no previous study has investigated how coupling TiO2 with Fe2O3 influences the photocatalytic oxidation of arsenic(III). Herein, we develop new hybrid experiment/modelling approaches to study light absorption, charge carrier behaviour and changes in the rate law of the TiO2/Fe2O3 system, using UV‐Vis spectroscopy, transient absorption spectroscopy (TAS), and kinetic analysis. Whilst coupling TiO2 with Fe2O3 improves total arsenic removal by adsorption, oxidation rates significantly decrease (up to a factor of 60), primarily due to the parasitic absorption of light by Fe2O3 (88 % of photons at 368 nm) and secondly due to changes in the rate law from disguised zero‐order kinetics to first‐order kinetics. Charge transfer across this TiO2‐Fe2O3 heterojunction is not observed. Our study demonstrates the first application of a multi‐adsorbate surface complexation model (SCM) towards describing As(III) oxidation kinetics which, unlike Langmuir‐Hinshelwood kinetics, includes the competitive adsorption of As(V). We further highlight the importance of parasitic light absorption and catalyst fouling when designing heterogeneous photocatalysts for As(III) remediation.
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Affiliation(s)
- Jay C Bullen
- Department of Earth Science and Engineering, Faculty of Engineering Imperial College London, London, SW7 2BX, UK.,Department of Chemistry, White City Campus Imperial College London, London, W12 OBZ, UK.,London Centre for Nanotechnology, London, SW7 2AZ, UK
| | - Hany F Heiba
- Department of Earth Science and Engineering, Faculty of Engineering Imperial College London, London, SW7 2BX, UK.,Department of Chemistry, White City Campus Imperial College London, London, W12 OBZ, UK.,London Centre for Nanotechnology, London, SW7 2AZ, UK.,Marine Chemistry Department, Environmental Division National Institute of Oceanography and Fisheries, NIOF), Egypt
| | - Andreas Kafizas
- Department of Chemistry, White City Campus Imperial College London, London, W12 OBZ, UK.,The Grantham Institute, Faculty of Natural Sciences Imperial College London, London, SW7 2AZ, UK
| | - Dominik J Weiss
- Department of Earth Science and Engineering, Faculty of Engineering Imperial College London, London, SW7 2BX, UK.,Civil and Environmental Engineering, E-Quad, Princeton University, Princeton, USA
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6
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Heiba HF, Bullen JC, Kafizas A, Petit C, Skinner SJ, Weiss D. The determination of oxidation rates and quantum yields during the photocatalytic oxidation of As(III) over TiO2. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2021.113628] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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7
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Moss B, Wang Q, Butler KT, Grau-Crespo R, Selim S, Regoutz A, Hisatomi T, Godin R, Payne DJ, Kafizas A, Domen K, Steier L, Durrant JR. Linking in situ charge accumulation to electronic structure in doped SrTiO 3 reveals design principles for hydrogen-evolving photocatalysts. Nat Mater 2021; 20:511-517. [PMID: 33432143 DOI: 10.1038/s41563-020-00868-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 11/03/2020] [Indexed: 05/14/2023]
Abstract
Recently, high solar-to-hydrogen efficiencies were demonstrated using La and Rh co-doped SrTiO3 (La,Rh:SrTiO3) incorporated into a low-cost and scalable Z-scheme device, known as a photocatalyst sheet. However, the unique properties that enable La,Rh:SrTiO3 to support this impressive performance are not fully understood. Combining in situ spectroelectrochemical measurements with density functional theory and photoelectron spectroscopy produces a depletion model of Rh:SrTiO3 and La,Rh:SrTiO3 photocatalyst sheets. This reveals remarkable properties, such as deep flatband potentials (+2 V versus the reversible hydrogen electrode) and a Rh oxidation state dependent reorganization of the electronic structure, involving the loss of a vacant Rh 4d mid-gap state. This reorganization enables Rh:SrTiO3 to be reduced by co-doping without compromising the p-type character. In situ time-resolved spectroscopies show that the electronic structure reorganization induced by Rh reduction controls the electron lifetime in photocatalyst sheets. In Rh:SrTiO3, enhanced lifetimes can only be obtained at negative applied potentials, where the complete Z-scheme operates inefficiently. La co-doping fixes Rh in the 3+ state, which results in long-lived photogenerated electrons even at very positive potentials (+1 V versus the reversible hydrogen electrode), in which both components of the complete device operate effectively. This understanding of the role of co-dopants provides a new insight into the design principles for water-splitting devices based on bandgap-engineered metal oxides.
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Affiliation(s)
- Benjamin Moss
- Department of Chemistry, Imperial College London, London, UK
- Centre for Processable Electronics, Imperial College London, London, UK
| | - Qian Wang
- Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan
- Department of Chemistry, University of Cambridge, Cambridge, UK
| | - Keith T Butler
- SciML, Scientific Computing Division, Rutherford Appleton Laboratory, Harwell, UK
| | | | - Shababa Selim
- Department of Chemistry, Imperial College London, London, UK
- Centre for Processable Electronics, Imperial College London, London, UK
| | - Anna Regoutz
- Department of Chemistry, University College London, London, UK
| | - Takashi Hisatomi
- Research Initiative for Supra-Materials, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, Nagano, Japan
| | - Robert Godin
- Department of Chemistry, Imperial College London, London, UK
- Department of Chemistry, University of British Columbia, Kelowna, British Columbia, Canada
| | - David J Payne
- Department of Materials, Imperial College London, London, UK
| | - Andreas Kafizas
- Department of Chemistry, Imperial College London, London, UK
- Grantham Institute, Imperial College London, London, UK
| | - Kazunari Domen
- Department of Chemistry, University of Reading, Reading, UK
- Office of University Professor, The University of Tokyo, Tokyo, Japan
| | - Ludmilla Steier
- Department of Chemistry, Imperial College London, London, UK.
| | - James R Durrant
- Department of Chemistry, Imperial College London, London, UK
- Centre for Processable Electronics, Imperial College London, London, UK
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8
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Alotaibi AM, Promdet P, Hwang GB, Li J, Nair SP, Sathasivam S, Kafizas A, Carmalt CJ, Parkin IP. Zn and N Codoped TiO 2 Thin Films: Photocatalytic and Bactericidal Activity. ACS Appl Mater Interfaces 2021; 13:10480-10489. [PMID: 33595295 DOI: 10.1021/acsami.1c00304] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We explore a series of Zn and N codoped TiO2 thin films grown using chemical vapor deposition. Films were prepared with various concentrations of Zn (0.4-2.9 at. % Zn vs Ti), and their impact on superoxide formation, photocatalytic activity, and bactericidal properties were determined. Superoxide (O2•-) formation was assessed using a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium sodium salt (XTT) as an indicator, photocatalytic activity was determined from the degradation of stearic acid under UVA light, and bactericidal activity was assessed using a Gram-negative bacterium E. coli under both UVA and fluorescent light (similar to what is found in a clinical environment). The 0.4% Zn,N:TiO2 thin film demonstrated the highest formal quantum efficiency in degrading stearic acid (3.3 × 10-5 molecules·photon-1), while the 1.0% Zn,N:TiO2 film showed the highest bactericidal activity under both UVA and fluorescent light conditions (>3 log kill). The enhanced efficiency of the films was correlated with increased charge carrier lifetime, supported by transient absorption spectroscopy (TAS) measurements.
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Affiliation(s)
- Abdullah M Alotaibi
- Materials Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
- The National Centre for Building and Construction Technology, King Abdulaziz City for Science and Technology (KACST), Riyadh, 11442-6086, Saudi Arabia
| | - Premrudee Promdet
- Materials Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Gi Byoung Hwang
- Materials Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Jianwei Li
- Materials Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Sean P Nair
- Department of Microbial Diseases, UCL Eastman Dental Institute, 256 Gray's Inn Road, London, WC1X 8LD, U.K
| | - Sanjayan Sathasivam
- Materials Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Andreas Kafizas
- Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, U.K
- The Grantham Institute, Imperial College London, South Kensington, London, SW7 2AZ, U.K
| | - Claire J Carmalt
- Materials Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Ivan P Parkin
- Materials Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
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9
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Iqbal A, Kafizas A, Sotelo-Vazquez C, Wilson R, Ling M, Taylor A, Blackman C, Bevan K, Parkin I, Quesada-Cabrera R. Charge Transport Phenomena in Heterojunction Photocatalysts: The WO 3/TiO 2 System as an Archetypical Model. ACS Appl Mater Interfaces 2021; 13:9781-9793. [PMID: 33595275 DOI: 10.1021/acsami.0c19692] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Recent studies have demonstrated the high efficiency through which nanostructured core-shell WO3/TiO2 (WT) heterojunctions can photocatalytically degrade model organic pollutants (stearic acid, QE ≈ 18% @ λ = 365 nm), and as such, has varied potential environmental and antimicrobial applications. The key motivation herein is to connect theoretical calculations of charge transport phenomena, with experimental measures of charge carrier behavior using transient absorption spectroscopy (TAS), to develop a fundamental understanding of how such WT heterojunctions achieve high photocatalytic efficiency (in comparison to standalone WO3 and TiO2 photocatalysts). This work reveals an order of magnitude enhancement in electron and hole recombination lifetimes, respectively located in the TiO2 and WO3 sides, when an optimally designed WT heterojunction photocatalyst operates under UV excitation. This observation is further supported by our computationally captured details of conduction band and valence band processes, identified as (i) dominant electron transfer from WO3 to TiO2 via the diffusion of excess electrons; and (ii) dominant hole transfer from TiO2 to WO3 via thermionic emission over the valence band edge. Simultaneously, our combined theoretical and experimental study offers a time-resolved understanding of what occurs on the micro- to milliseconds (μs-ms) time scale in this archetypical photocatalytic heterojunction. At the microsecond time scale, a portion of the accumulated holes in WO3 contribute to the depopulation of W5+ polaronic states, whereas the remaining accumulated holes in WO3 are separated from adjacent electrons in TiO2 up to 3 ms after photoexcitation. The presence of these exceptionally long-lived photogenerated carriers, dynamically separated by the WT heterojunction, is the origin of the superior photocatalytic efficiency displayed by this system (in the degradation of stearic acid). Consequently, our combined computational and experimental approach delivers a robust understanding of the direction of charge separation along with critical time-resolved insights into the evolution of charge transport phenomena in this model heterojunction photocatalyst.
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Affiliation(s)
- Asif Iqbal
- Materials Engineering, McGill University, 3610 University Street, Montréal Quebec H3A 0C5, Canada
| | - Andreas Kafizas
- Department of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom
- The Grantham Institute, Imperial College London, London SW7 2AZ, United Kingdom
| | - Carlos Sotelo-Vazquez
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Rachel Wilson
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Min Ling
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Alaric Taylor
- Department of Electronic & Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
| | - Chris Blackman
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Kirk Bevan
- Materials Engineering, McGill University, 3610 University Street, Montréal Quebec H3A 0C5, Canada
| | - Ivan Parkin
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Raul Quesada-Cabrera
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
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10
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Wilson AA, Corby S, Francàs L, Durrant JR, Kafizas A. The effect of nanoparticulate PdO co-catalysts on the faradaic and light conversion efficiency of WO 3 photoanodes for water oxidation. Phys Chem Chem Phys 2021; 23:1285-1291. [PMID: 33367408 DOI: 10.1039/d0cp06124g] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
WO3 photoanodes offer rare stability in acidic media, but are limited by their selectivity for oxygen evolution over parasitic side reactions, when employed in photoelectrochemical (PEC) water splitting. Herein, this is remedied via the modification of nanostructured WO3 photoanodes with surface decorated PdO as an oxygen evolution co-catalyst (OEC). The photoanodes and co-catalyst particles are grown using an up-scalable aerosol assisted chemical vapour deposition (AA-CVD) route, and their physical properties characterised by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and UV-vis absorption spectroscopy. Subsequent PEC and transient photocurrent (TPC) measurements showed that the use of a PdO co-catalyst dramatically increases the faradaic efficiency (FE) of water oxidation from 52% to 92%, whilst simultaneously enhancing the photocurrent generation and charge extraction rate. The Pd oxidation state was found to be critical in achieving these notable improvements to the photoanode performance, which is primarily attributed to the higher selectivity towards oxygen evolution when PdO is used as an OEC and the formation of a favourable junction between WO3 and PdO, that drives band bending and charge separation.
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Affiliation(s)
- Anna A Wilson
- Department of Chemistry and Centre for Plastic Electronics, Imperial College London, White City Campus, London, W12 0BZ, UK.
| | - Sacha Corby
- Department of Chemistry and Centre for Plastic Electronics, Imperial College London, White City Campus, London, W12 0BZ, UK.
| | - Laia Francàs
- Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Barcelona 08193, Spain.
| | - James R Durrant
- Department of Chemistry and Centre for Plastic Electronics, Imperial College London, White City Campus, London, W12 0BZ, UK.
| | - Andreas Kafizas
- Department of Chemistry and Centre for Plastic Electronics, Imperial College London, White City Campus, London, W12 0BZ, UK. and The Grantham Institute, Imperial College London, South Kensington, London, SW7 2AZ, UK and London Centre for Nanotechnology, Imperial College London, SW7 2AZ, UK
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11
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Vernardou D, Drosos C, Kafizas A, Pemble ME, Koudoumas E. Towards High Performance Chemical Vapour Deposition V 2O 5 Cathodes for Batteries Employing Aqueous Media. Molecules 2020; 25:molecules25235558. [PMID: 33256209 PMCID: PMC7730033 DOI: 10.3390/molecules25235558] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 11/22/2020] [Accepted: 11/25/2020] [Indexed: 11/16/2022] Open
Abstract
The need for clean and efficient energy storage has become the center of attention due to the eminent global energy crisis and growing ecological concerns. A key component in this effort is the ultra-high performance battery, which will play a major role in the energy industry. To meet the demands in portable electronic devices, electric vehicles, and large-scale energy storage systems, it is necessary to prepare advanced batteries with high safety, fast charge ratios, and discharge capabilities at a low cost. Cathode materials play a significant role in determining the performance of batteries. Among the possible electrode materials is vanadium pentoxide, which will be discussed in this review, due to its low cost and high theoretical capacity. Additionally, aqueous electrolytes, which are environmentally safe, provide an alternative approach compared to organic media for safe, cost-effective, and scalable energy storage. In this review, we will reveal the industrial potential of competitive methods to grow cathodes with excellent stability and enhanced electrochemical performance in aqueous media and lay the foundation for the large-scale production of electrode materials.
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Affiliation(s)
- Dimitra Vernardou
- Department of Electrical and Computer Engineering, School of Engineering, Hellenic Mediterranean University, 71410 Heraklion, Greece;
- Institute of Emerging Technologies, Hellenic Mediterranean University Center, 71410 Heraklion, Greece
- Correspondence: ; Tel.: +30-2810-379631
| | | | - Andreas Kafizas
- Department of Chemistry, Molecular Science Research Hub, Imperial College London, White City, London W12 0BZ, UK;
- Grantham Institute for Climate Change and the Environment, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Martyn E. Pemble
- School of Chemistry, University College Cork, T12 YN60 Cork, Ireland;
| | - Emmanouel Koudoumas
- Department of Electrical and Computer Engineering, School of Engineering, Hellenic Mediterranean University, 71410 Heraklion, Greece;
- Institute of Emerging Technologies, Hellenic Mediterranean University Center, 71410 Heraklion, Greece
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12
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Alqahtani M, Kafizas A, Sathasivam S, Ebaid M, Cui F, Alyamani A, Jeong HH, Chun Lee T, Fischer P, Parkin I, Grätzel M, Wu J. A Hierarchical 3D TiO 2 /Ni Nanostructure as an Efficient Hole-Extraction and Protection Layer for GaAs Photoanodes. ChemSusChem 2020; 13:6028-6036. [PMID: 32986913 DOI: 10.1002/cssc.202002004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 09/28/2020] [Indexed: 06/11/2023]
Abstract
Photoelectrochemical (PEC) water splitting is a promising clean route to hydrogen fuel. The best-performing materials (III/V semiconductors) require surface passivation, as they are liable to corrosion, and a surface co-catalyst to facilitate water splitting. At present, optimal design combining photoelectrodes with oxygen evolution catalysts remains a significant materials challenge. Here, we demonstrate that nickel-coated amorphous three-dimensional (3D) TiO2 core-shell nanorods on a TiO2 thin film function as an efficient hole-extraction layer and serve as a protection layer for the GaAs photoanode. Transient-absorption spectroscopy (TAS) demonstrated the role of nickel-coated (3D) TiO2 core-shell nanorods in prolonging photogenerated charge lifetimes in GaAs, resulting in a higher catalytic activity. This strategy may open the potential of utilizing this low-cost (3D) nanostructured catalyst for decorating narrow-band-gap semiconductor photoanodes for PEC water splitting devices.
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Affiliation(s)
- Mahdi Alqahtani
- Department of Electronic and Electrical Engineering, University College London, London, WC1E 7JE, United Kingdom
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
- King Abdulaziz City for Science and Technology (KACST), Riyadh, 12371, Saudi Arabia
| | - Andreas Kafizas
- Department of Chemistry, Imperial College London, London, W12 0BZ, United Kingdom
- The Grantham Institute, Imperial College London, London, SW7 2AZ, United Kingdom
| | - Sanjayan Sathasivam
- Department of Chemistry University College London London WC1H 0AJ (United Kingdom)
| | - Mohamed Ebaid
- Joint Centre for Artificial Photosynthesis (JCAP), Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA
| | - Fan Cui
- Department of Electronic and Electrical Engineering, University College London, London, WC1E 7JE, United Kingdom
| | - Ahmed Alyamani
- King Abdulaziz City for Science and Technology (KACST), Riyadh, 12371, Saudi Arabia
| | - Hyeon-Ho Jeong
- Max Planck Institute for Intelligent Systems, Heisenbergstraße 3, 70569, Stuttgart, Germany
| | - Tung Chun Lee
- Department of Chemistry University College London London WC1H 0AJ (United Kingdom)
- Institute for Materials Discovery, University College London, London, WC1E 7JE, United Kingdom
| | - Peer Fischer
- Max Planck Institute for Intelligent Systems, Heisenbergstraße 3, 70569, Stuttgart, Germany
| | - Ivan Parkin
- Department of Chemistry University College London London WC1H 0AJ (United Kingdom)
| | - Michael Grätzel
- Institute of Chemical Science and Engineering Faculty of Basic Science, Ecole Polytechnique Federale de Lausanne, 1015, Lausanne, Switzerland
| | - Jiang Wu
- Department of Electronic and Electrical Engineering, University College London, London, WC1E 7JE, United Kingdom
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
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13
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Bullen JC, Kenney JPL, Fearn S, Kafizas A, Skinner S, Weiss DJ. Improved accuracy in multicomponent surface complexation models using surface-sensitive analytical techniques: Adsorption of arsenic onto a TiO 2/Fe 2O 3 multifunctional sorbent. J Colloid Interface Sci 2020; 580:834-849. [PMID: 32731167 DOI: 10.1016/j.jcis.2020.06.119] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 06/17/2020] [Accepted: 06/28/2020] [Indexed: 11/17/2022]
Abstract
Novel composite materials are increasingly developed for water treatment applications with the aim of achieving multifunctional behaviour, e.g. combining adsorption with light-driven remediation. The application of surface complexation models (SCM) is important to understand how adsorption changes as a function of pH, ionic strength and the presence of competitor ions. Component additive (CA) models describe composite sorbents using a combination of single-phase reference materials. However, predictive adsorption modelling using the CA-SCM approach remains unreliable, due to challenges in the quantitative determination of surface composition. In this study, we test the hypothesis that characterisation of the outermost surface using low energy ion scattering (LEIS) improves CA-SCM accuracy. We consider the TiO2/Fe2O3 photocatalyst-sorbents that are increasingly investigated for arsenic remediation. Due to an iron oxide surface coating that was not captured by bulk analysis, LEIS significantly improves the accuracy of our component additive predictions for monolayer surface processes: adsorption of arsenic(V) and surface acidity. We also demonstrate non-component additivity in multilayer arsenic(III) adsorption, due to changes in surface morphology/porosity. Our results demonstrate how surface-sensitive analytical techniques will improve adsorption models for the next generation of composite sorbents.
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Affiliation(s)
- Jay C Bullen
- Department of Earth Science and Engineering, Faculty of Engineering, Imperial College London, London SW7 2BX, UK.
| | - Janice P L Kenney
- Department of Physical Sciences, MacEwan University, Edmonton, Alberta T5J 4S2P, Canada
| | - Sarah Fearn
- Department of Materials, Faculty of Engineering, Imperial College London, London SW7 2BX, UK
| | - Andreas Kafizas
- Department of Chemistry, White City Campus, Imperial College London, London W12 OBZ, UK; The Grantham Institute, Imperial College London, London, SW7 2AZ, UK
| | - Stephen Skinner
- Department of Materials, Faculty of Engineering, Imperial College London, London SW7 2BX, UK
| | - Dominik J Weiss
- Department of Earth Science and Engineering, Faculty of Engineering, Imperial College London, London SW7 2BX, UK; Civil and Environmental Engineering, E-Quad, Princeton University, Princeton, USA.
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14
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Abstract
In this work, the electrochemical performance of aerosol-assisted chemical vapour deposited vanadium pentoxide cathodes at 600 °C, is presented. The as-grown oxides indicate specific discharge capacity of 300 mA h g-1 with capacity retention of 92 % after 10000 scans, coulombic efficiency of 100 %, noble structural stability and high reversibility. The present study shows the possibility to grow large-area magnesium cathode material with extended cycle stability via utilization of an aqueous electrolyte under a corrosive environment. This enhanced performance may be a combination of electrode morphology and adherence, when compared to previous work employing electrode growth temperature at 500 °C.
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15
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Alotaibi A, Williamson BAD, Sathasivam S, Kafizas A, Alqahtani M, Sotelo-Vazquez C, Buckeridge J, Wu J, Nair SP, Scanlon DO, Parkin IP. Enhanced Photocatalytic and Antibacterial Ability of Cu-Doped Anatase TiO 2 Thin Films: Theory and Experiment. ACS Appl Mater Interfaces 2020; 12:15348-15361. [PMID: 32109038 PMCID: PMC7146757 DOI: 10.1021/acsami.9b22056] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 02/28/2020] [Indexed: 05/12/2023]
Abstract
Multifunctional thin films which can display both photocatalytic and antibacterial activity are of great interest industrially. Here, for the first time, we have used aerosol-assisted chemical vapor deposition to deposit highly photoactive thin films of Cu-doped anatase TiO2 on glass substrates. The films displayed much enhanced photocatalytic activity relative to pure anatase and showed excellent antibacterial (vs Staphylococcus aureus and Escherichia coli) ability. Using a combination of transient absorption spectroscopy, photoluminescence measurements, and hybrid density functional theory calculations, we have gained nanoscopic insights into the improved properties of the Cu-doped TiO2 films. Our analysis has highlighted that the interactions between substitutional and interstitial Cu in the anatase lattice can explain the extended exciton lifetimes observed in the doped samples and the enhanced UV photoactivities observed.
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Affiliation(s)
- Abdullah
M. Alotaibi
- Materials
Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
- The
National Centre for Building and Construction Technology, King Abdulaziz City for Science and Technology (KACST), Riyadh 11442-6086, Saudi Arabia
| | - Benjamin A. D. Williamson
- Department
of Chemistry, Christopher Ingold Building, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
- Thomas
Young Centre, University College London, Gower Street, London WC1E 6BT, U.K.
| | - Sanjayan Sathasivam
- Materials
Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - Andreas Kafizas
- Grantham Institute,
Imperial College
London, Exhibition Road, London SW7 2AZ, U.K.
| | - Mahdi Alqahtani
- Electronic
& Electrical Engineering, University
College London, Torrington
Place, London WC1E 7JE, U.K.
- Materials
Science Research Institute, King Abdulaziz
City for Science and Technology (KACST), Riyadh 11442-6086, Saudi Arabia
| | - Carlos Sotelo-Vazquez
- Materials
Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - John Buckeridge
- School
of Engineering, London South Bank University, 103 Borough Road, London SE1 0AA, U.K.
| | - Jiang Wu
- Electronic
& Electrical Engineering, University
College London, Torrington
Place, London WC1E 7JE, U.K.
- University
of Electronic Science and Technology of China, North Jianshe Road, Chengdu 610054, China
| | - Sean P. Nair
- Department
of Microbial Diseases, UCL Eastman Dental
Institute, 256 Gray’s
Inn Road, London WC1X 8LD, U.K.
| | - David O. Scanlon
- Department
of Chemistry, Christopher Ingold Building, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
- Thomas
Young Centre, University College London, Gower Street, London WC1E 6BT, U.K.
- Diamond Light Source Ltd., Diamond House, Harwell Science and
Innovation Campus, Didcot, Oxfordshire OX11 0DE, U.K.
| | - Ivan P. Parkin
- Materials
Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
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16
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Hwang GB, Huang H, Wu G, Shin J, Kafizas A, Karu K, Toit HD, Alotaibi AM, Mohammad-Hadi L, Allan E, MacRobert AJ, Gavriilidis A, Parkin IP. Photobactericidal activity activated by thiolated gold nanoclusters at low flux levels of white light. Nat Commun 2020; 11:1207. [PMID: 32139700 PMCID: PMC7057968 DOI: 10.1038/s41467-020-15004-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 02/11/2020] [Indexed: 12/29/2022] Open
Abstract
The emergence of antibiotic resistant bacteria is a major threat to the practice of modern medicine. Photobactericidal agents have obtained significant attention as promising candidates to kill bacteria, and they have been extensively studied. However, to obtain photobactericidal activity, an intense white light source or UV-activation is usually required. Here we report a photobactericidal polymer containing crystal violet (CV) and thiolated gold nanocluster ([Au25(Cys)18]) activated at a low flux levels of white light. It was shown that the polymer encapsulated with CV do not have photobactericidal activity under white light illumination of an average 312 lux. However, encapsulation of [Au25(Cys)18] and CV into the polymer activates potent photobactericidal activity. The study of the photobactericidal mechanism shows that additional encapsulation of [Au25(Cys)18] into the CV treated polymer promotes redox reactions through generation of alternative electron transfer pathways, while it reduces photochemical reaction type-ІІ pathways resulting in promotion of hydrogen peroxide (H2O2) production.
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Affiliation(s)
- Gi Byoung Hwang
- Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
| | - He Huang
- Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK
| | - Gaowei Wu
- Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK
| | - Juhun Shin
- Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
| | - Andreas Kafizas
- Department of Chemistry, Imperial College London, Molecular Science Research Hub, White City Campus, 80 Wood Lane, London, W12 OBZ, UK
- Grantham Institute, Imperial College London, Exhibition Road, London, SW7 2AZ, UK
| | - Kersti Karu
- Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
| | - Hendrik Du Toit
- Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK
| | - Abdullah M Alotaibi
- Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
| | - Layla Mohammad-Hadi
- UCL Division of Surgery and Interventional Science, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK
| | - Elaine Allan
- Department of Microbial Diseases, UCL Eastman Dental Institute, University College London, 256 Grays Inn Road, London, WC1X 8LD, UK
| | - Alexander J MacRobert
- UCL Division of Surgery and Interventional Science, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK
| | - Asterios Gavriilidis
- Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK
| | - Ivan P Parkin
- Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK.
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17
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Corby S, Francàs L, Kafizas A, Durrant JR. Determining the role of oxygen vacancies in the photoelectrocatalytic performance of WO 3 for water oxidation. Chem Sci 2020; 11:2907-2914. [PMID: 34122791 PMCID: PMC8157495 DOI: 10.1039/c9sc06325k] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Oxygen vacancies are common to most metal oxides, whether intentionally incorporated or otherwise, and the study of these defects is of increasing interest for solar water splitting. In this work, we examine nanostructured WO3 photoanodes of varying oxygen content to determine how the concentration of bulk oxygen-vacancy states affects the photocatalytic performance for water oxidation. Using transient optical spectroscopy, we follow the charge carrier recombination kinetics in these samples, from picoseconds to seconds, and examine how differing oxygen vacancy concentrations impact upon these kinetics. We find that samples with an intermediate concentration of vacancies (∼2% of oxygen atoms) afford the greatest photoinduced charge carrier densities, and the slowest recombination kinetics across all timescales studied. This increased yield of photogenerated charges correlates with improved photocurrent densities under simulated sunlight, with both greater and lesser oxygen vacancy concentrations resulting in enhanced recombination losses and poorer J–V performances. Our conclusion, that an optimal – neither too high nor too low – concentration of oxygen vacancies is required for optimum photoelectrochemical performance, is discussed in terms of the competing beneficial and detrimental impact these defects have on charge separation and transport, as well as the implications held for other highly doped materials for photoelectrochemical water oxidation. A medium concentration of oxygen vacancies (VO ≈ 2%) is critical to the performance of WO3 photoanodes for solar water oxidation, enhancing charge separation and reducing recombination across all timescales examined.![]()
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Affiliation(s)
- Sacha Corby
- Department of Chemistry, Centre for Plastic Electronics, Imperial College London White City Campus London W12 0BZ UK .,Grantham Institute for Climate Change, Imperial College London South Kensington London SW7 2AZ UK
| | - Laia Francàs
- Department of Chemistry, Centre for Plastic Electronics, Imperial College London White City Campus London W12 0BZ UK
| | - Andreas Kafizas
- Department of Chemistry, Centre for Plastic Electronics, Imperial College London White City Campus London W12 0BZ UK .,Grantham Institute for Climate Change, Imperial College London South Kensington London SW7 2AZ UK
| | - James R Durrant
- Department of Chemistry, Centre for Plastic Electronics, Imperial College London White City Campus London W12 0BZ UK
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18
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Selim S, Pastor E, García-Tecedor M, Morris MR, Francàs L, Sachs M, Moss B, Corby S, Mesa CA, Gimenez S, Kafizas A, Bakulin AA, Durrant JR. Impact of Oxygen Vacancy Occupancy on Charge Carrier Dynamics in BiVO4 Photoanodes. J Am Chem Soc 2019; 141:18791-18798. [DOI: 10.1021/jacs.9b09056] [Citation(s) in RCA: 104] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Shababa Selim
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
| | - Ernest Pastor
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
| | | | - Madeleine R. Morris
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
| | - Laia Francàs
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
| | - Michael Sachs
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
| | - Benjamin Moss
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
| | - Sacha Corby
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
| | - Camilo A. Mesa
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
| | - Sixto Gimenez
- Institute of Advanced Materials (INAM), Universitat Jaume I, 12006 Castelló, Spain
| | - Andreas Kafizas
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
- The Grantham Institute, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
| | - Artem A. Bakulin
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
| | - James R. Durrant
- Department of Chemistry and Centre for Plastic Electronics, MSRH, White City Campus, Imperial College London, London W12 0BZ, United Kingdom
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19
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Mesa CA, Francàs L, Yang KR, Garrido-Barros P, Pastor E, Ma Y, Kafizas A, Rosser TE, Mayer MT, Reisner E, Grätzel M, Batista VS, Durrant JR. Multihole water oxidation catalysis on haematite photoanodes revealed by operando spectroelectrochemistry and DFT. Nat Chem 2019; 12:82-89. [DOI: 10.1038/s41557-019-0347-1] [Citation(s) in RCA: 111] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 09/03/2019] [Indexed: 11/09/2022]
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20
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Corby S, Pastor E, Dong Y, Zheng X, Francàs L, Sachs M, Selim S, Kafizas A, Bakulin AA, Durrant JR. Charge Separation, Band-Bending, and Recombination in WO 3 Photoanodes. J Phys Chem Lett 2019; 10:5395-5401. [PMID: 31416313 DOI: 10.1021/acs.jpclett.9b01935] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In metal oxide-based photoelectrochemical devices, the spatial separation of photogenerated electrons and holes is typically attributed to band-bending at the oxide/electrolyte interface. However, direct evidence of such band-bending impacting upon charge carrier lifetimes has been very limited to date. Herein we use ultrafast spectroscopy to track the rapid relaxation of holes in the space-charge layer and their recombination with trapped electrons in WO3 photoanodes. We observe that applied bias can significantly increase carrier lifetimes on all time scales from picoseconds to seconds and attribute this to enhanced band-bending correlated with changes in oxygen vacancy state occupancy. We show that analogous enhancements in carrier lifetimes can be obtained by changes in electrolyte composition, even in the absence of applied bias, highlighting routes to improve photoconversion yields/performance, through changes in band-bending. This study thus demonstrates the direct connection between carrier lifetime enhancement, increased band-bending, and oxygen vacancy defect state occupancy.
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Affiliation(s)
- Sacha Corby
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
| | - Ernest Pastor
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
| | - Yifan Dong
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
| | - Xijia Zheng
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
| | - Laia Francàs
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
| | - Michael Sachs
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
| | - Shababa Selim
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
| | - Andreas Kafizas
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
- Grantham Institute for Climate Change , Imperial College London , South Kensington , London SW7 2AZ , United Kingdom
| | - Artem A Bakulin
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
| | - James R Durrant
- Department of Chemistry and Centre for Plastic Electronics , Imperial College London , White City Campus, London W12 0BZ , United Kingdom
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21
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Jiamprasertboon A, Kafizas A, Sachs M, Ling M, Alotaibi AM, Lu Y, Siritanon T, Parkin IP, Carmalt CJ. Heterojunction α-Fe 2 O 3 /ZnO Films with Enhanced Photocatalytic Properties Grown by Aerosol-Assisted Chemical Vapour Deposition. Chemistry 2019; 25:11337-11345. [PMID: 31241218 DOI: 10.1002/chem.201902175] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 06/23/2019] [Indexed: 11/06/2022]
Abstract
Type I heterojunction films of α-Fe2 O3 /ZnO are reported here as a non-titania based photocatalyst, which shows remarkable enhancement in the photocatalytic properties towards stearic acid degradation under UVA-light exposure (λ=365 nm), with a quantum efficiency of ξ=4.42±1.54×10-4 molecules degraded/photon, which was about 16 times greater than that of α-Fe2 O3 , and 2.5 times greater than that of ZnO. Considering that the degradation of stearic acid requires 104 electron transfers for each molecule, this represents an overall quantum efficiency of 4.60 % for the α-Fe2 O3 /ZnO heterojunction. Time-resolved transient absorption spectroscopy (TAS) revealed the charge-carrier behaviour responsible for this increase in activity. Photogenerated electrons, formed in the ZnO layer, were transferred into the α-Fe2 O3 layer on the pre-μs timescale, which reduced electron-hole recombination. This increased the lifetime of photogenerated holes formed in ZnO, which oxidise stearic acid. The heterojunction α-Fe2 O3 /ZnO films grown herein show potential environmental applications as coatings for self-cleaning windows and surfaces.
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Affiliation(s)
- Arreerat Jiamprasertboon
- School of Chemistry, Institute of Science, Suranaree University of Technology, 111 University Avenue, Muang, Nakhon Ratchasima, 30000, Thailand.,Material Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
| | - Andreas Kafizas
- Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, UK.,The Grantham Institute, Imperial College London, South Kensington, London, SW7 2AZ, UK
| | - Michael Sachs
- The Grantham Institute, Imperial College London, South Kensington, London, SW7 2AZ, UK
| | - Min Ling
- Material Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
| | - Abdullah M Alotaibi
- Material Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
| | - Yao Lu
- Department of Mechanical Engineering, University College London, London, WC1E 7JE, UK
| | - Theeranun Siritanon
- School of Chemistry, Institute of Science, Suranaree University of Technology, 111 University Avenue, Muang, Nakhon Ratchasima, 30000, Thailand
| | - Ivan P Parkin
- Material Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
| | - Claire J Carmalt
- Material Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
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22
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Sachs M, Park JS, Pastor E, Kafizas A, Wilson AA, Francàs L, Gul S, Ling M, Blackman C, Yano J, Walsh A, Durrant JR. Effect of oxygen deficiency on the excited state kinetics of WO 3 and implications for photocatalysis. Chem Sci 2019; 10:5667-5677. [PMID: 31293751 PMCID: PMC6563783 DOI: 10.1039/c9sc00693a] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 04/12/2019] [Indexed: 01/01/2023] Open
Abstract
Using WO3 as a model material, we investigate how different oxygen vacancy concentrations affect trapping of photogenerated charges and photocatalytic reactions in metal oxides.
Oxygen vacancies are widely used to tune the light absorption of semiconducting metal oxides, but a photophysical framework describing the impact of such point defects on the dynamics of photogenerated charges, and ultimately on catalysis, is still missing. We herein use WO3 as a model material and investigate the impact of significantly different degrees of oxygen deficiency on its excited state kinetics. For highly oxygen-deficient films, photoelectron spectroscopy shows an over 2 eV broad distribution of oxygen vacancy states within the bandgap which gives rise to extended visible light absorption. We examine the nature of this distribution using first-principles defect calculations and find that defects aggregate to form clusters rather than isolated vacancy sites. Using transient absorption spectroscopy, we observe trapping of photogenerated holes within 200 fs after excitation at high degrees of oxygen deficiency, which increases their lifetime at the expense of oxidative driving force. This loss in driving force limits the use of metal oxides with significant degrees of sub-stoichiometry to photocatalytic reactions that require low oxidation power such as pollutant degradation, and highlights the need to fine-tune vacancy state distributions for specific target reactions.
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Affiliation(s)
- Michael Sachs
- Department of Chemistry , Imperial College London , London , SW7 2AZ , UK . ;
| | - Ji-Sang Park
- Department of Materials , Imperial College London , London , SW7 2AZ , UK.,Department of Materials Science and Engineering , Yonsei University , Seoul 03722 , Korea
| | - Ernest Pastor
- Department of Chemistry , Imperial College London , London , SW7 2AZ , UK . ;
| | - Andreas Kafizas
- Department of Chemistry , Imperial College London , London , SW7 2AZ , UK . ; .,The Grantham Institute , Imperial College London , London , SW7 2AZ , UK
| | - Anna A Wilson
- Department of Chemistry , Imperial College London , London , SW7 2AZ , UK . ;
| | - Laia Francàs
- Department of Chemistry , Imperial College London , London , SW7 2AZ , UK . ;
| | - Sheraz Gul
- Molecular Biophysics and Integrated Bioimaging Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , USA
| | - Min Ling
- Department of Chemistry , University College London , 20 Gordon Street , London , WC1H 0AJ , UK
| | - Chris Blackman
- Department of Chemistry , University College London , 20 Gordon Street , London , WC1H 0AJ , UK
| | - Junko Yano
- Molecular Biophysics and Integrated Bioimaging Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , USA
| | - Aron Walsh
- Department of Materials , Imperial College London , London , SW7 2AZ , UK.,Department of Materials Science and Engineering , Yonsei University , Seoul 03722 , Korea
| | - James R Durrant
- Department of Chemistry , Imperial College London , London , SW7 2AZ , UK . ;
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23
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Crake A, Christoforidis KC, Gregg A, Moss B, Kafizas A, Petit C. The Effect of Materials Architecture in TiO 2 /MOF Composites on CO 2 Photoreduction and Charge Transfer. Small 2019; 15:e1805473. [PMID: 30716205 DOI: 10.1002/smll.201805473] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Indexed: 06/09/2023]
Abstract
CO2 photoreduction to C1 /C1+ energized molecules is a key reaction of solar fuel technologies. Building heterojunctions can enhance photocatalysts performance, by facilitating charge transfer between two heterojunction phases. The material parameters that control this charge transfer remain unclear. Here, it is hypothesized that governing factors for CO2 photoreduction in gas phase are: i) a large porosity to accumulate CO2 molecules close to catalytic sites and ii) a high number of "points of contact" between the heterojunction components to enhance charge transfer. The former requirement can be met by using porous materials; the latter requirement by controlling the morphology of the heterojunction components. Hence, composites of titanium oxide or titanate and metal-organic framework (MOF), a highly porous material, are built. TiO2 or titanate nanofibers are synthesized and MOF particles are grown on the fibers. All composites produce CO under UV-vis light, using H2 as reducing agent. They are more active than their component materials, e.g., ≈9 times more active than titanate. The controlled composites morphology is confirmed and transient absorption spectroscopy highlights charge transfer between the composite components. It is demonstrated that electrons transfer from TiO2 into the MOF, and holes from the MOF into TiO2 , as the MOF induces band bending in TiO2 .
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Affiliation(s)
- Angus Crake
- Barrer Centre, Department of Chemical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK
| | - Konstantinos C Christoforidis
- Barrer Centre, Department of Chemical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK
| | - Aoife Gregg
- Barrer Centre, Department of Chemical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK
| | - Benjamin Moss
- Department of Chemistry, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK
| | - Andreas Kafizas
- Department of Chemistry, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK
| | - Camille Petit
- Barrer Centre, Department of Chemical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK
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24
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Kafizas A, Xing X, Selim S, Mesa CA, Ma Y, Burgess C, McLachlan MA, Durrant JR. Ultra-thin Al2O3 coatings on BiVO4 photoanodes: Impact on performance and charge carrier dynamics. Catal Today 2019. [DOI: 10.1016/j.cattod.2017.11.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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25
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Selim S, Francàs L, García-Tecedor M, Corby S, Blackman C, Gimenez S, Durrant JR, Kafizas A. WO 3/BiVO 4: impact of charge separation at the timescale of water oxidation. Chem Sci 2019; 10:2643-2652. [PMID: 30996980 PMCID: PMC6419945 DOI: 10.1039/c8sc04679d] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Accepted: 12/19/2018] [Indexed: 01/16/2023] Open
Abstract
Unveiling the role of applied bias on the charge carrier dynamics in the WO3/BiVO4 junction during water oxidation.
The four hole oxidation of water has long been considered the kinetic bottleneck for overall solar-driven water splitting, and thus requires the formation of long-lived photogenerated holes to overcome this kinetic barrier. However, photogenerated charges are prone to recombination unless they can be spatially separated. This can be achieved by coupling materials with staggered conduction and valence band positions, providing a thermodynamic driving force for charge separation. This has most aptly been demonstrated in the WO3/BiVO4 junction, in which quantum efficiencies for the water oxidation reaction can approach near unity. However, the charge carrier dynamics in this system remain elusive over timescales relevant to water oxidation (μs–s). In this work, the effect of charge separation on carrier lifetime, and the voltage dependence of this process, is probed using transient absorption spectroscopy and transient photocurrent measurements, revealing sub-μs electron transfer from BiVO4 to WO3. The interface formed between BiVO4 and WO3 is shown to overcome the “dead-layer effect” encountered in BiVO4 alone. Moreover, our study sheds light on the role of the WO3/BiVO4 junction in enhancing the efficiency of the water oxidation reaction, where charge separation across the WO3/BiVO4 junction improves both the yield and lifetime of holes present in the BiVO4 layer over timescales relevant to water oxidation.
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Affiliation(s)
- Shababa Selim
- Imperial College London , Department of Chemistry , South Kensington , London , SW7 2AZ , UK .
| | - Laia Francàs
- Imperial College London , Department of Chemistry , South Kensington , London , SW7 2AZ , UK .
| | - Miguel García-Tecedor
- Institute of Advanced Materials (INAM) , Universitat Jaume I , 12006 , Castelló de la Plana , Spain
| | - Sacha Corby
- Imperial College London , Department of Chemistry , South Kensington , London , SW7 2AZ , UK .
| | - Chris Blackman
- University College London , Department of Chemistry , Gordon Street , London , WC1H 0AJ , UK
| | - Sixto Gimenez
- Institute of Advanced Materials (INAM) , Universitat Jaume I , 12006 , Castelló de la Plana , Spain
| | - James R Durrant
- Imperial College London , Department of Chemistry , South Kensington , London , SW7 2AZ , UK .
| | - Andreas Kafizas
- Imperial College London , Department of Chemistry , South Kensington , London , SW7 2AZ , UK . .,The Grantham Institute , Imperial College London , South Kensington , London , SW7 2AZ , UK
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26
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Corby S, Francàs L, Selim S, Sachs M, Blackman C, Kafizas A, Durrant JR. Water Oxidation and Electron Extraction Kinetics in Nanostructured Tungsten Trioxide Photoanodes. J Am Chem Soc 2018; 140:16168-16177. [DOI: 10.1021/jacs.8b08852] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sacha Corby
- The Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K
| | - Laia Francàs
- The Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K
| | - Shababa Selim
- The Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K
| | - Michael Sachs
- The Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K
| | - Chris Blackman
- The Department of Chemistry, University College London, Kings Cross, London WC1H 0AJ, U.K
| | - Andreas Kafizas
- The Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K
- The Grantham Institute, Imperial College London, South Kensington, London SW7 2AZ, U.K
| | - James R. Durrant
- The Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K
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27
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Mesa CA, Kafizas A, Francàs L, Pendlebury SR, Pastor E, Ma Y, Le Formal F, Mayer MT, Grätzel M, Durrant JR. Kinetics of Photoelectrochemical Oxidation of Methanol on Hematite Photoanodes. J Am Chem Soc 2017; 139:11537-11543. [PMID: 28735533 PMCID: PMC5594441 DOI: 10.1021/jacs.7b05184] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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The kinetics of photoelectrochemical
(PEC) oxidation of methanol, as a model organic substrate, on α-Fe2O3 photoanodes are studied using photoinduced absorption
spectroscopy and transient photocurrent measurements. Methanol is
oxidized on α-Fe2O3 to formaldehyde with
near unity Faradaic efficiency. A rate law analysis under quasi-steady-state
conditions of PEC methanol oxidation indicates that rate of reaction
is second order in the density of surface holes on hematite and independent
of the applied potential. Analogous data on anatase TiO2 photoanodes indicate similar second-order kinetics for methanol
oxidation with a second-order rate constant 2 orders of magnitude
higher than that on α-Fe2O3. Kinetic isotope
effect studies determine that the rate constant for methanol oxidation
on α-Fe2O3 is retarded ∼20-fold
by H/D substitution. Employing these data, we propose a mechanism
for methanol oxidation under 1 sun irradiation on these metal oxide
surfaces and discuss the implications for the efficient PEC methanol
oxidation to formaldehyde and concomitant hydrogen evolution.
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Affiliation(s)
- Camilo A Mesa
- Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2 AZ, United Kingdom
| | - Andreas Kafizas
- Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2 AZ, United Kingdom
| | - Laia Francàs
- Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2 AZ, United Kingdom
| | - Stephanie R Pendlebury
- Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2 AZ, United Kingdom
| | - Ernest Pastor
- Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2 AZ, United Kingdom
| | - Yimeng Ma
- Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2 AZ, United Kingdom
| | - Florian Le Formal
- Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2 AZ, United Kingdom.,Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne , Station 6, CH-1015 Lausanne, Switzerland
| | - Matthew T Mayer
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne , Station 6, CH-1015 Lausanne, Switzerland
| | - Michael Grätzel
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne , Station 6, CH-1015 Lausanne, Switzerland
| | - James R Durrant
- Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2 AZ, United Kingdom
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28
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Kafizas A, Ma Y, Pastor E, Pendlebury SR, Mesa C, Francàs L, Le Formal F, Noor N, Ling M, Sotelo-Vazquez C, Carmalt CJ, Parkin IP, Durrant JR. Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO2 Photoanode: A Rate Law Analysis. ACS Catal 2017. [DOI: 10.1021/acscatal.7b01150] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Andreas Kafizas
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Yimeng Ma
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Ernest Pastor
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Stephanie R. Pendlebury
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Camilo Mesa
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Laia Francàs
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Florian Le Formal
- Laboratory
for Molecular Engineering of Optoelectronic Nanomaterials, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Nuruzzaman Noor
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Min Ling
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Carlos Sotelo-Vazquez
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Claire J. Carmalt
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Ivan P. Parkin
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - James R. Durrant
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
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29
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Moss B, Lim KK, Beltram A, Moniz S, Tang J, Fornasiero P, Barnes P, Durrant J, Kafizas A. Comparing photoelectrochemical water oxidation, recombination kinetics and charge trapping in the three polymorphs of TiO 2. Sci Rep 2017; 7:2938. [PMID: 28592816 PMCID: PMC5462794 DOI: 10.1038/s41598-017-03065-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 04/21/2017] [Indexed: 11/13/2022] Open
Abstract
In this article we present the first comparative study of the transient decay dynamics of photo-generated charges for the three polymorphs of TiO2. To our knowledge, this is the first such study of the brookite phase of TiO2 over timescales relevant to the kinetics of water splitting. We find that the behavior of brookite, both in the dynamics of relaxation of photo-generated charges and in energetic distribution, is similar to the anatase phase of TiO2. Moreover, links between the rate of recombination of charge carriers, their energetic distribution and the mode of transport are made in light of our findings and used to account for the differences in water splitting efficiency observed across the three polymorphs.
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Affiliation(s)
- Benjamin Moss
- Imperial College London, Department of Chemistry, South Kensington Campus, London, SW7 2AZ, UK
| | - Kee Kean Lim
- Tunku Abdul Rahman University College, Department of Mathematics, Kampus Utama, Jalan Genting Kelang, 53300, Kuala Lumpur, Malaysia
| | - Alessandro Beltram
- Department of Chemical and Pharmaceutical Sciences and ICCOM Trieste Research Unit, University of Trieste, via L. Giorgieri 1, 34127, Trieste, Italy
| | - Savio Moniz
- University College London, Department of Chemistry, Gower Street, London, WC1H 0AJ, UK
| | - Junwang Tang
- University College London, Department of Chemistry, Gower Street, London, WC1H 0AJ, UK
| | - Paolo Fornasiero
- Department of Chemical and Pharmaceutical Sciences and ICCOM Trieste Research Unit, University of Trieste, via L. Giorgieri 1, 34127, Trieste, Italy
| | - Piers Barnes
- Imperial College London, Department of Chemistry, South Kensington Campus, London, SW7 2AZ, UK
| | - James Durrant
- Imperial College London, Department of Chemistry, South Kensington Campus, London, SW7 2AZ, UK
| | - Andreas Kafizas
- Imperial College London, Department of Chemistry, South Kensington Campus, London, SW7 2AZ, UK.
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30
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Chadwick NP, Kafizas A, Quesada-Cabrera R, Sotelo-Vazquez C, Bawaked SM, Mokhtar M, Al Thabaiti SA, Obaid AY, Basahel SN, Durrant JR, Carmalt CJ, Parkin IP. Ultraviolet Radiation Induced Dopant Loss in a TiO2 Photocatalyst. ACS Catal 2017. [DOI: 10.1021/acscatal.6b03170] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Nicholas P. Chadwick
- Materials
Research Centre, Chemistry Department, University College London, London WC1H 0AJ, U.K
- Bio Nano Consulting, The Gridiron Building, One Pancras Square, London N1C 4AG, U.K
| | - Andreas Kafizas
- Materials
Research Centre, Chemistry Department, University College London, London WC1H 0AJ, U.K
- Chemistry
Department, Imperial College London, London SW7 2AZ, U.K
| | - Raul Quesada-Cabrera
- Materials
Research Centre, Chemistry Department, University College London, London WC1H 0AJ, U.K
| | - Carlos Sotelo-Vazquez
- Materials
Research Centre, Chemistry Department, University College London, London WC1H 0AJ, U.K
| | - Salem M. Bawaked
- Chemistry
Department, Faculty of Science, King Abdulaziz University, Jeddah 23218, Saudi Arabia
- Surface
Chemistry and Catalytic Studies Group, King Abdulaziz University, Jeddah 23218, Saudi Arabia
| | - Mohamed Mokhtar
- Chemistry
Department, Faculty of Science, King Abdulaziz University, Jeddah 23218, Saudi Arabia
- Surface
Chemistry and Catalytic Studies Group, King Abdulaziz University, Jeddah 23218, Saudi Arabia
| | - Shaeel A. Al Thabaiti
- Chemistry
Department, Faculty of Science, King Abdulaziz University, Jeddah 23218, Saudi Arabia
- Surface
Chemistry and Catalytic Studies Group, King Abdulaziz University, Jeddah 23218, Saudi Arabia
| | - Abdullah Y. Obaid
- Chemistry
Department, Faculty of Science, King Abdulaziz University, Jeddah 23218, Saudi Arabia
- Surface
Chemistry and Catalytic Studies Group, King Abdulaziz University, Jeddah 23218, Saudi Arabia
| | - Sulaiman N. Basahel
- Chemistry
Department, Faculty of Science, King Abdulaziz University, Jeddah 23218, Saudi Arabia
- Surface
Chemistry and Catalytic Studies Group, King Abdulaziz University, Jeddah 23218, Saudi Arabia
| | - James R. Durrant
- Chemistry
Department, Imperial College London, London SW7 2AZ, U.K
| | - Claire J. Carmalt
- Materials
Research Centre, Chemistry Department, University College London, London WC1H 0AJ, U.K
| | - Ivan P. Parkin
- Materials
Research Centre, Chemistry Department, University College London, London WC1H 0AJ, U.K
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31
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Sachs M, Pastor E, Kafizas A, Durrant JR. Evaluation of Surface State Mediated Charge Recombination in Anatase and Rutile TiO 2. J Phys Chem Lett 2016; 7:3742-3746. [PMID: 27564137 PMCID: PMC5056403 DOI: 10.1021/acs.jpclett.6b01501] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 08/26/2016] [Indexed: 05/20/2023]
Abstract
In nanostructured thin films, photogenerated charge carriers can access the surface more easily than in dense films and thus react more readily. However, the high surface area of these films has also been associated with enhanced recombination losses via surface states. We herein use transient absorption spectroscopy to compare the ultrafast charge carrier kinetics in dense and nanostructured TiO2 films for its two most widely used polymorphs: anatase and rutile. We find that nanostructuring does not enhance recombination rates on ultrafast time scales, indicating that surface state mediated recombination is not a key loss pathway for either TiO2 polymorph. Rutile shows faster, and less intensity-dependent recombination than anatase, which we assign to its higher doping density. For both polymorphs, we conclude that bulk rather than surface recombination is the primary determinant of charge carrier lifetime.
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Affiliation(s)
- Michael Sachs
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K.
| | - Ernest Pastor
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K.
| | - Andreas Kafizas
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - James R. Durrant
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K.
- E-mail:
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32
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Kafizas A, Wang X, Pendlebury SR, Barnes P, Ling M, Sotelo-Vazquez C, Quesada-Cabrera R, Li C, Parkin IP, Durrant JR. Where Do Photogenerated Holes Go in Anatase:Rutile TiO2? A Transient Absorption Spectroscopy Study of Charge Transfer and Lifetime. J Phys Chem A 2016; 120:715-23. [DOI: 10.1021/acs.jpca.5b11567] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andreas Kafizas
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Xiuli Wang
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
- State
Key Laboratory of Catalysis, Dalian Institute of Chemical Physics,
Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Stephanie R. Pendlebury
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Piers Barnes
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
| | - Min Ling
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Carlos Sotelo-Vazquez
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Raul Quesada-Cabrera
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Can Li
- State
Key Laboratory of Catalysis, Dalian Institute of Chemical Physics,
Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Ivan P. Parkin
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - James R. Durrant
- Department
of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K
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33
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Ma Y, Le Formal F, Kafizas A, Pendlebury SR, Durrant JR. Efficient suppression of back electron/hole recombination in cobalt phosphate surface-modified undoped bismuth vanadate photoanodes. J Mater Chem A Mater 2015; 3:20649-20657. [PMID: 27358733 PMCID: PMC4894069 DOI: 10.1039/c5ta05826k] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 09/08/2015] [Indexed: 05/14/2023]
Abstract
In this paper, we compared for the first time the dynamics of photogenerated holes in BiVO4 photoanodes with and without CoPi surface modification, employing transient absorption and photocurrent measurements on microsecond to second timescales. CoPi surface modification is known to cathodically shift the water oxidation onset potential; however, the reason for this improvement has not until now been fully understood. The transient absorption and photocurrent data were analyzed using a simple kinetic model, which allows quantification of the competition between electron/hole recombination and water oxidation. The results of this model are shown to be in excellent agreement with the measured photocurrent data. We demonstrate that the origin of the improvement of photocurrent onset resulting from CoPi treatment is primarily due to retardation of back electron/hole recombination across the space charge layer; no evidence of catalytic water oxidation via CoPi was observed.
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Affiliation(s)
- Yimeng Ma
- Department of Chemistry , Imperial College London , South Kensington Campus , London , SW7 2AZ , UK .
| | - Florian Le Formal
- Department of Chemistry , Imperial College London , South Kensington Campus , London , SW7 2AZ , UK . ; Laboratory for Molecular Engineering of Optoelectronic Nanomaterials , Institute of Chemical Sciences and Engineering , École Polytechnique Fédérale de Lausanne (EPFL) , Station 6 , CH H4 565 , Lausanne 1015 , Switzerland
| | - Andreas Kafizas
- Department of Chemistry , Imperial College London , South Kensington Campus , London , SW7 2AZ , UK .
| | - Stephanie R Pendlebury
- Department of Chemistry , Imperial College London , South Kensington Campus , London , SW7 2AZ , UK .
| | - James R Durrant
- Department of Chemistry , Imperial College London , South Kensington Campus , London , SW7 2AZ , UK .
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Pendlebury SR, Wang X, Le Formal F, Cornuz M, Kafizas A, Tilley SD, Grätzel M, Durrant JR. Ultrafast charge carrier recombination and trapping in hematite photoanodes under applied bias. J Am Chem Soc 2014; 136:9854-7. [PMID: 24950057 PMCID: PMC4210134 DOI: 10.1021/ja504473e] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Transient absorption spectroscopy on subpicosecond to second time scales is used to investigate photogenerated charge carrier recombination in Si-doped nanostructured hematite (α-Fe2O3) photoanodes as a function of applied bias. For unbiased hematite, this recombination exhibits a 50% decay time of ~6 ps, ~10(3) times faster than that of TiO2 under comparable conditions. Anodic bias significantly retards hematite recombination dynamics, and causes the appearance of electron trapping on ps-μs time scales. These ultrafast recombination dynamics, their retardation by applied bias, and the associated electron trapping are discussed in terms of their implications for efficient water oxidation.
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Affiliation(s)
- Stephanie R Pendlebury
- Department of Chemistry, Imperial College London, South Kensington Campus , London, SW7 2AZ, United Kingdom
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Knapp CE, Manzi JA, Kafizas A, Parkin IP, Carmalt CJ. Aerosol-Assisted Chemical Vapour Deposition of Transparent Zinc Gallate Films. Chempluschem 2014. [DOI: 10.1002/cplu.201402037] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Sathasivam S, Kafizas A, Ponja S, Chadwick N, Bhachu DS, Bawaked SM, Obaid AY, Al-Thabaiti S, Basahel SN, Carmalt CJ, Parkin IP. Combinatorial Atmospheric Pressure CVD of a Composite TiO2/SnO2Thin Film. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/cvde.201307081] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sanjayan Sathasivam
- Materials Chemistry Research Centre, Department of Chemistry; University College London; 20 Gordon Street London WC1H 0AJ (U.K.)
| | - Andreas Kafizas
- Materials Chemistry Research Centre, Department of Chemistry; University College London; 20 Gordon Street London WC1H 0AJ (U.K.)
| | - Sapna Ponja
- Materials Chemistry Research Centre, Department of Chemistry; University College London; 20 Gordon Street London WC1H 0AJ (U.K.)
| | - Nicholas Chadwick
- Materials Chemistry Research Centre, Department of Chemistry; University College London; 20 Gordon Street London WC1H 0AJ (U.K.)
| | - Davinder S. Bhachu
- Materials Chemistry Research Centre, Department of Chemistry; University College London; 20 Gordon Street London WC1H 0AJ (U.K.)
| | - Salem M. Bawaked
- Chemistry Department; King Abdulaziz University; Abdullah Sulayman Jeddah 22254 (Saudi Arabia)
| | - Abdullah Y. Obaid
- Chemistry Department; King Abdulaziz University; Abdullah Sulayman Jeddah 22254 (Saudi Arabia)
| | - Shaeel Al-Thabaiti
- Chemistry Department; King Abdulaziz University; Abdullah Sulayman Jeddah 22254 (Saudi Arabia)
| | - Sulaiman N. Basahel
- Chemistry Department; King Abdulaziz University; Abdullah Sulayman Jeddah 22254 (Saudi Arabia)
| | - Claire J. Carmalt
- Materials Chemistry Research Centre, Department of Chemistry; University College London; 20 Gordon Street London WC1H 0AJ (U.K.)
| | - Ivan P. Parkin
- Materials Chemistry Research Centre, Department of Chemistry; University College London; 20 Gordon Street London WC1H 0AJ (U.K.)
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Wilkinson M, Kafizas A, Bawaked SM, Obaid AY, Al-Thabaiti SA, Basahel SN, Carmalt CJ, Parkin IP. Combinatorial atmospheric pressure chemical vapor deposition of graded TiO₂-VO₂ mixed-phase composites and their dual functional property as self-cleaning and photochromic window coatings. ACS Comb Sci 2013; 15:309-19. [PMID: 23688025 DOI: 10.1021/co400027p] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A combinatorial film with a phase gradient from V:TiO₂ (V: Ti ≥ 0.08), through a range of TiO₂-VO₂ composites, to a vanadium-rich composite (V: Ti = 1.81) was grown by combinatorial atmospheric pressure chemical vapor deposition (cAPCVD). The film was grown from the reaction of TiCl₄, VCl₄, ethyl acetate (EtAc), and H₂O at 550 °C on glass. The gradient in gas mixtures across the reactor induced compositional film growth, producing a single film with numerous phases and compositions at different positions. Seventeen unique positions distributed evenly along a central horizontal strip were investigated. The physical properties were characterized by wavelength dispersive X-ray (WDX) analysis, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV-visible spectroscopy. The functional properties examined included the degree of photoinduced hydrophilicity (PIH), UVC-photocatalysis, and thermochromism. Superhydrophilic contact angles could be achieved at all positions, even within a highly VO₂-rich composite (V: Ti = 1.81). A maximum level of UVC photocatalysis was observed at a position bordering the solubility limit of V:TiO₂ (V: Ti ≈ 0.21) and fragmentation into a mixed-phase composite. Within the mixed-phase TiO₂: VO₂ composition region (V: Ti = 1.09 to 1.81) a decrease in the semiconductor-to-metal transition temperature of VO₂ from 68 to 51 °C was observed.
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Affiliation(s)
- Mia Wilkinson
- Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London,
U.K. WC1H 0AJ
| | - Andreas Kafizas
- Department
of Chemistry, Imperial College London,
Exhibition Road, London, U.K. SW7 2AZ
| | - Salem M. Bawaked
- Chemistry Department, King Abdulaziz University, Jeddah, Saudi Arabia 21589
| | - Abdullah Y. Obaid
- Chemistry Department, King Abdulaziz University, Jeddah, Saudi Arabia 21589
| | | | | | - Claire J. Carmalt
- Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London,
U.K. WC1H 0AJ
| | - Ivan P. Parkin
- Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London,
U.K. WC1H 0AJ
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Kafizas A, A. Parry S, Chadwick AV, Carmalt CJ, Parkin IP. An EXAFS study on the photo-assisted growth of silver nanoparticles on titanium dioxide thin-films and the identification of their photochromic states. Phys Chem Chem Phys 2013; 15:8254-63. [DOI: 10.1039/c3cp44513e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kafizas A, Carmalt CJ, Parkin IP. Does a Photocatalytic Synergy in an Anatase-Rutile TiO2Composite Thin-Film Exist? Chemistry 2012; 18:13048-58. [DOI: 10.1002/chem.201201859] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Indexed: 11/08/2022]
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Crick CR, Bear JC, Kafizas A, Parkin IP. Superhydrophobic photocatalytic surfaces through direct incorporation of titania nanoparticles into a polymer matrix by aerosol assisted chemical vapor deposition. Adv Mater 2012; 24:3505-8. [PMID: 22706974 DOI: 10.1002/adma.201201239] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Revised: 05/17/2012] [Indexed: 05/24/2023]
Abstract
A new class of superhydrophobic photocatalytic surfaces that are self-cleaning through light-induced photodegradation and the Lotus effect are presented. The films are formed in a single-step aerosol-assisted chemical vapor deposition (AACVD) process. The films are durable and show no degradation on continuous exposure to UV-C radiation.
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Affiliation(s)
- Colin R Crick
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK
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Cabrera RQ, Latimer ER, Kafizas A, Blackman CS, Carmalt CJ, Parkin IP. Photocatalytic activity of needle-like TiO2/WO3−x thin films prepared by chemical vapour deposition. J Photochem Photobiol A Chem 2012. [DOI: 10.1016/j.jphotochem.2012.05.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Kafizas A, Parkin IP. Combinatorial atmospheric pressure chemical vapor deposition (cAPCVD): a route to functional property optimization. J Am Chem Soc 2011; 133:20458-67. [PMID: 22050427 DOI: 10.1021/ja208633g] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We demonstrate how combinatorial atmospheric pressure chemical vapor deposition (cAPCVD) can be used as a synthetic tool for rapidly optimizing the functional properties of thin-films, by analyzing the self-cleaning properties of tungsten doped anatase as an example. By introducing reagents at separate points inside the reactor, a tungsten/titanium compositional gradient was formed and a diverse range of film growth conditions were obtained. By partially mixing the metal sources, a combinatorial film with a compositional profile that varied primarily in the lateral plane was synthesized. A combinatorial thin-film of anatase TiO(2) doped with an array of tungsten levels as a solid solution ranging from 0.38-13.8 W/Ti atom % was formed on a single glass substrate. The compositional-functional relationships were understood through comprehensively analyzing combinatorial phase space, with 200 positions investigated by high-throughput methods in this study. Physical and functional properties, and their compositional dependencies, were intercorrelated. It was found that increases in photocatalytic activity and conductivity were most highly dependent on film crystallinity within the 0.38-13.8 atom % W/Ti doping regime. However, enhancements in photoinduced surface wetting were primarily dependent on increases in preferred growth in the (211) crystal plane.
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Affiliation(s)
- Andreas Kafizas
- Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London, UK WC1H 0AJ
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Dunnill CW, Page K, Aiken ZA, Noimark S, Hyett G, Kafizas A, Pratten J, Wilson M, Parkin IP. Nanoparticulate silver coated-titania thin films—Photo-oxidative destruction of stearic acid under different light sources and antimicrobial effects under hospital lighting conditions. J Photochem Photobiol A Chem 2011. [DOI: 10.1016/j.jphotochem.2011.04.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Kundu S, Kafizas A, Hyett G, Mills A, Darr JA, Parkin IP. An investigation into the effect of thickness of titanium dioxide and gold–silver nanoparticle titanium dioxide composite thin-films on photocatalytic activity and photo-induced oxygen production in a sacrificial system. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c0jm03492d] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Dunnill CW, Ansari Z, Kafizas A, Perni S, Morgan DJ, Wilson M, Parkin IP. Visible light photocatalysts—N-doped TiO2 by sol–gel, enhanced with surface bound silver nanoparticle islands. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm11557j] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kafizas A, Dunnill CW, Parkin IP. The relationship between photocatalytic activity and photochromic state of nanoparticulate silver surface loaded titanium dioxide thin-films. Phys Chem Chem Phys 2011; 13:13827-38. [DOI: 10.1039/c1cp20624a] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Knapp CE, Kafizas A, Parkin IP, Carmalt CJ. The use of combinatorial aerosol-assisted chemical vapour deposition for the formation of gallium-indium-oxide thin films. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm11606a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kafizas A, Crick C, Parkin IP. The combinatorial atmospheric pressure chemical vapour deposition (cAPCVD) of a gradating substitutional/interstitial N-doped anatase TiO2 thin-film; UVA and visible light photocatalytic activities. J Photochem Photobiol A Chem 2010. [DOI: 10.1016/j.jphotochem.2010.06.034] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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