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Seriani N, Delcompare-Rodriguez P, Pandey D, Adak AK, Mahamiya V, Pinilla C, El-Khozondar HJ. Quantitative Analysis of the Synergy of Doping and Nanostructuring of Oxide Photocatalysts. MATERIALS (BASEL, SWITZERLAND) 2024; 17:3460. [PMID: 39063753 PMCID: PMC11278242 DOI: 10.3390/ma17143460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2024] [Revised: 07/11/2024] [Accepted: 07/11/2024] [Indexed: 07/28/2024]
Abstract
In this paper, the effect of doping and nanostructuring on the electrostatic potential across the electrochemical interface between a transition metal oxide and a water electrolyte is investigated by means of the Poisson-Boltzmann model. For spherical nanoparticles and nanorods, compact expressions for the limiting potentials at which the space charge layer includes the whole semiconductor are reported. We provide a quantitative analysis of the distribution of the potential drop between the solid and the liquid and show that the relative importance changes with doping. It is usually assumed that high doping improves charge dynamics in the semiconductor but reduces the width of the space charge layer. However, nanostructuring counterbalances the latter negative effect; we show quantitatively that in highly doped nanoparticles the space charge layer can occupy a similar volume fraction as in low-doped microparticles. Moreover, as shown by some recent experiments, under conditions of high doping the electric fields in the Helmholtz layer can be as high as 100 mV/Å, comparable to electric fields inducing freezing in water. This work provides a systematic quantitative framework for understanding the effects of doping and nanostructuring on electrochemical interfaces, and suggests that it is necessary to better characterize the interface at the atomistic level.
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Affiliation(s)
- Nicola Seriani
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy (A.K.A.)
| | - Paola Delcompare-Rodriguez
- Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche (CNR-IOM), Via Bonomea 265, 34136 Trieste, Italy
| | - Dhanshree Pandey
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy (A.K.A.)
| | - Abhishek Kumar Adak
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy (A.K.A.)
| | - Vikram Mahamiya
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy (A.K.A.)
| | - Carlos Pinilla
- Departamento de Fisica y Geociencias, Universidad del Norte, Km 5, Via Puerto Colombia, Barranquilla 080020, Colombia
| | - Hala J. El-Khozondar
- Electrical Engineering and Smart Systems Department, Faculty of Engineering, Islamic University of Gaza, Gaza P.O. Box 108, Palestine
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2
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German E, Gebauer R. The Oxygen Evolution Reaction at MoS 2 Edge Sites: The Role of a Solvent Environment in DFT-Based Molecular Simulations. Molecules 2023; 28:5182. [PMID: 37446844 DOI: 10.3390/molecules28135182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 06/23/2023] [Accepted: 06/28/2023] [Indexed: 07/15/2023] Open
Abstract
Density functional theory (DFT) calculations are employed to study the oxygen evolution reaction (OER) on the edges of stripes of monolayer molybdenum disulfide. Experimentally, this material has been shown to evolve oxygen, albeit with low efficiency. Previous DFT studies have traced this low catalytic performance to the unfavourable adsorption energies of some reaction intermediates on the MoS2 edge sites. In this work, we study the effects of the aqueous liquid surrounding the active sites. A computational approach is used, where the solvent is modeled as a continuous medium providing a dielectric embedding of the catalyst and the reaction intermediates. A description at this level of theory can have a profound impact on the studied reactions: the calculated overpotential for the OER is lowered from 1.15 eV to 0.77 eV. It is shown that such variations in the reaction energetics are linked to the polar nature of the adsorbed intermediates, which leads to changes in the calculated electronic charge density when surrounded by water. These results underline the necessity to computationally account for solvation effects, especially in aqueous environments and when highly polar intermediates are present.
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Affiliation(s)
- Estefania German
- Department of Theoretical, Atomic and Optical Physics, University of Valladolid, 47011 Valladolid, Spain
| | - Ralph Gebauer
- The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, 34151 Trieste, Italy
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3
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Wang H, Zhou Z, Long R, Prezhdo OV. Passivation of Hematite by a Semiconducting Overlayer Reduces Charge Recombination: An Insight from Nonadiabatic Molecular Dynamics. J Phys Chem Lett 2023; 14:879-887. [PMID: 36661401 DOI: 10.1021/acs.jpclett.2c03643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Hematite (α-Fe2O3) is a promising photoanode material for photoelectrochemical water splitting. Surface-passivating layers are effective in improving water oxidation kinetics; however, the passivation mechanism is not fully understood due to the complexity of interfacial reactions. Focusing on the Fe-terminated Fe2O3 (0001) surface that exhibits surface states in the band gap, we perform ab initio quantum dynamics simulations to study the effect of an α-Ga2O3 overlayer on charge recombination. The overlayer eliminates surface states and suppresses charge recombination 4-fold. This explains in part the observed cathodic shift in the onset potential for water oxidation. The increased charge carrier lifetime is an outcome of two factors, energy gap and electron-vibrational coupling, with a positive contribution from the former but a negative contribution from the latter. This work presents an advance in the atomistic time-domain understanding of the influence of surface passivation on charge recombination dynamics and provides guidance for designing novel α-Fe2O3 photoanodes.
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Affiliation(s)
- Hua Wang
- Department of Chemical Engineering, School of Water and Environment, Chang'an University, Xi'an710064, China
| | - Zhaohui Zhou
- Department of Chemical Engineering, School of Water and Environment, Chang'an University, Xi'an710064, China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing100875, China
| | - Oleg V Prezhdo
- Deparment of Chemistry, University of Southern California, Los Angeles, California90089, United States
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Delcompare-Rodriguez PA, Seriani N. Ultrathin space charge layer in hematite photoelectrodes: A theoretical investigation. J Chem Phys 2021; 155:114701. [PMID: 34551523 DOI: 10.1063/5.0060417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The space charge layer in hematite photoelectrodes has been analyzed by means of Poisson-Boltzmann equations, the Stern model, and density functional theory, in view of its application for photoelectrochemical water oxidation. The width of the space charge layer can be smaller than ∼10 Å under experimental conditions. In this regime, a substantial part of the potential drop takes place in the Helmholtz layer, leading to important corrections to the Mott-Schottky behavior of the space charge layer capacitance. These results shed light on an unexpected regime of high photoelectrocatalytic efficiency, different from the classical picture of the electrochemical interface of a semiconducting photocatalyst, which is also amenable to direct study by quantum-mechanical atomistic simulations. Density functional theory has been used to calculate the band bending (BB) in the space charge layer in atomistic models of pristine stoichiometric and hydroxylated surfaces. These surface terminations display BBs of 0.14 and 0.49 eV, respectively, with an increasing width of the space charge layer, however still in the sub-nanometer regime. This work shows that, at high doping, the width of the space charge layer of a hematite photoelectrode can become comparable with interatomic distances.
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Affiliation(s)
| | - N Seriani
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
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5
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da Silva Alvim R, Ribeiro FN, Dalpian GM. Iron and oxygen vacancies at the hematite surface: pristine case and with a chlorine adatom. Phys Chem Chem Phys 2020; 22:25380-25389. [PMID: 33140776 DOI: 10.1039/d0cp03798b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Defect complexes play critical roles in the dynamics of water molecules in photoelectrochemical cell devices. For the specific case of hematite (α-Fe2O3), iron and oxygen vacancies are said to mediate the water splitting process through the localization of optically-derived charges. Using first-principles methods based on density-functional theory we show that both iron and oxygen vacancies can be observed at the surface. For an oxygen-rich environment, usually under wet conditions, the charged iron vacancies should be more frequent. As sea water would be an ideal electrolyte for this kind of device, we have also analyzed the effect of additional chlorine adsorption on this surface. While the chlorine adatom kills the charged oxygen vacancies, entering the void sites, it will not react with the iron vacancies, keeping them active during water splitting processes.
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Affiliation(s)
- Raphael da Silva Alvim
- Centro de Ciências Naturais e Humanas Universidade Federal do ABC Santo André, SP 09210-580, Brazil.
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6
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Ahamed I, Seriani N, Gebauer R, Kashyap A. Heterostructures of ε-Fe 2O 3 and α-Fe 2O 3: insights from density functional theory. RSC Adv 2020; 10:27474-27480. [PMID: 35516952 PMCID: PMC9055593 DOI: 10.1039/d0ra04020g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/17/2020] [Indexed: 02/04/2023] Open
Abstract
Many materials used in energy devices or applications suffer from the problem of electron-hole pair recombination. One promising way to overcome this problem is the use of heterostructures in place of a single material. If an electric dipole forms at the interface, such a structure can lead to a more efficient electron-hole pair separation and thus prevent recombination. Here we model and study a heterostructure comprised of two polymorphs of Fe2O3. Each one of the two polymorphs, α-Fe2O3 and ε-Fe2O3, individually shows promise for applications in photoelectrochemical cells. The heterostructure of these two materials is modeled by means of density functional theory. We consider both ferromagnetic as well as anti-ferromagnetic couplings at the interface between the two systems. Both individual oxides are insulating in nature and have an anti-ferromagnetic spin arrangement in their ground state. The same properties are found also in their heterostructure. The highest occupied electronic orbitals of the combined system are localized at the interface between the two iron-oxides. The localization of charges at the interface is characterized by electrons residing close to the oxygen atoms of ε-Fe2O3 and electron-holes localized on the iron atoms of α-Fe2O3, just around the interface. The band alignment at the interface of the two oxides shows a type-III broken band-gap heterostructure. The band edges of α-Fe2O3 are higher in energy than those of ε-Fe2O3. This band alignment favours a spontaneous transfer of excited photo-electrons from the conduction band of α- to the conduction band of ε-Fe2O3. Similarly, photo-generated holes are transferred from the valence band of ε- to the valence band of α-Fe2O3. Thus, the interface favours a spontaneous separation of electrons and holes in space. The conduction band of ε-Fe2O3, lying close to the valence band of α-Fe2O3, can result in band-to-band tunneling of electrons which is a characteristic property of such type-III broken band-gap heterostructures and has potential applications in tunnel field-effect transistors.
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Affiliation(s)
- Imran Ahamed
- School of Basic Sciences, Indian Institute of Technology Mandi Himachal Pradesh 175005 India
| | - Nicola Seriani
- The Abdus Salam International Centre for Theoretical Physics (ICTP) Strada Costiera 11 34151 Trieste Italy
| | - Ralph Gebauer
- The Abdus Salam International Centre for Theoretical Physics (ICTP) Strada Costiera 11 34151 Trieste Italy
| | - Arti Kashyap
- School of Basic Sciences, School of Computing and Electrical Engineering, Indian Institute of Technology Mandi Himachal Pradesh 175005 India
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8
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Huang Y, Yuan H, Chen H. Passivating Surface States on Water Splitting Cuprous Oxide Photocatalyst with Bismuth Decoration. Molecules 2019; 24:E4156. [PMID: 31744108 PMCID: PMC6891353 DOI: 10.3390/molecules24224156] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 11/09/2019] [Accepted: 11/12/2019] [Indexed: 01/01/2023] Open
Abstract
To enhance the visible light photocatalystic activity of Cu 2 O(100) surface, we performed first-principles calculations on the structural, electronic and optical properties of a bismuth (Bi)-decorated Cu 2 O(100) surface (Bi@Cu 2 O(100)). It is shown that the Bi prefer to be loaded to the hollow sites among four surface oxygen atoms and tend to individual dispersion instead of aggregating on the surface due to the lowest formation energy and larger distance between two Bi atoms at the surface than the Bi clusters; the coverage of around 0.25 monolayer Bi atoms can effectively eliminate the surface states and modify the band edges to satisfy the angular momentum selection rules for light excited transition of electrons, and the loaded Bi atoms contribute to the separation of photogenerated electron-holes. The relative positions between the band edges and the redox potentials are suitable for photocatalytic hydrogen production from the redox water, and moreover, the optical absorption spectrum indicates a positive response of the Bi 0 . 25 @Cu 2 O(100) to visible light, implying that the Bi 0 . 25 @Cu 2 O(100) is a promising visible light photocatalyst.
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Affiliation(s)
| | | | - Hong Chen
- School of Physical Science and Technology, Southwest University, Chongqing 400715, China; (Y.H.); (H.Y.)
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9
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Ulman K, Poli E, Seriani N, Piccinin S, Gebauer R. Understanding the electrochemical double layer at the hematite/water interface: A first principles molecular dynamics study. J Chem Phys 2019; 150:041707. [PMID: 30709242 DOI: 10.1063/1.5047930] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Kanchan Ulman
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
| | - Emiliano Poli
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
| | - Nicola Seriani
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
| | - Simone Piccinin
- CNR-IOM Democritos, c/o SISSA, Via Bonomea 265, 34136 Trieste, Italy
| | - Ralph Gebauer
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
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10
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Zhang Q, Wu QP, Zhang Y, Yan JT, Xue S, Wang HY. A facile surface passivation of hematite photoanodes with molybdate overlayers for efficient PEC water oxidation. CHINESE J CHEM PHYS 2018. [DOI: 10.1063/1674-0068/31/cjcp1806133] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Qi Zhang
- Tianjin Key Laboratory of the Design and Intelligent Control of the Advanced Mechanical System, School of Mechanical Engineering, Tianjin University of Technology, Tianjin 300384, China
- Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry & Chemical Engineering, Tianjin University of Technology, Tianjin 300384, China
| | - Quan-ping Wu
- Tianjin Key Laboratory of the Design and Intelligent Control of the Advanced Mechanical System, School of Mechanical Engineering, Tianjin University of Technology, Tianjin 300384, China
| | - Yue Zhang
- Tianjin Key Laboratory of the Design and Intelligent Control of the Advanced Mechanical System, School of Mechanical Engineering, Tianjin University of Technology, Tianjin 300384, China
| | - Ji-tong Yan
- Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry & Chemical Engineering, Tianjin University of Technology, Tianjin 300384, China
| | - Song Xue
- Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry & Chemical Engineering, Tianjin University of Technology, Tianjin 300384, China
| | - Hong-yan Wang
- Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry & Chemical Engineering, Tianjin University of Technology, Tianjin 300384, China
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11
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Grave DA, Yatom N, Ellis DS, Toroker MC, Rothschild A. The "Rust" Challenge: On the Correlations between Electronic Structure, Excited State Dynamics, and Photoelectrochemical Performance of Hematite Photoanodes for Solar Water Splitting. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1706577. [PMID: 29504160 DOI: 10.1002/adma.201706577] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 12/31/2017] [Indexed: 06/08/2023]
Abstract
In recent years, hematite's potential as a photoanode material for solar hydrogen production has ignited a renewed interest in its physical and interfacial properties, which continues to be an active field of research. Research on hematite photoanodes provides new insights on the correlations between electronic structure, transport properties, excited state dynamics, and charge transfer phenomena, and expands our knowledge on solar cell materials into correlated electron systems. This research news article presents a snapshot of selected theoretical and experimental developments linking the electronic structure to the photoelectrochemical performance, with particular focus on optoelectronic properties and charge carrier dynamics.
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Affiliation(s)
- Daniel A Grave
- Department of Materials Science and Engineering, Technion - Israel Institute of Technology, Haifa, 3200003, Israel
| | - Natav Yatom
- Department of Materials Science and Engineering, Technion - Israel Institute of Technology, Haifa, 3200003, Israel
| | - David S Ellis
- Department of Materials Science and Engineering, Technion - Israel Institute of Technology, Haifa, 3200003, Israel
| | - Maytal Caspary Toroker
- Department of Materials Science and Engineering, Technion - Israel Institute of Technology, Haifa, 3200003, Israel
| | - Avner Rothschild
- Department of Materials Science and Engineering, Technion - Israel Institute of Technology, Haifa, 3200003, Israel
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12
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Characterization of peroxo reaction intermediates in the water oxidation process on hematite surfaces. J Mol Model 2018; 24:284. [PMID: 30229320 DOI: 10.1007/s00894-018-3815-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 08/29/2018] [Indexed: 10/28/2022]
Abstract
We use density functional theory-based calculations to study structural, electronic, and magnetic properties of two key reaction intermediates on a hematite, [Formula: see text]-Fe2O3, photoanode during the solar-driven water splitting reaction. Both intermediates contain an oxygen atom bonded to a surface iron atom. In one case, the adsorbed oxygen also forms a peroxo bond with a lattice oxygen from hematite; in the second case no such bond is formed. Both configurations are energetically equivalent and are related to the overpotential-determining step in the oxygen evolution reaction. The calculated reaction path for the breaking of the peroxo bond shows a barrier of about 0.86 eV for the transformation between the two intermediates. We explain this high barrier with the drastically different electronic and magnetic structure, which we also analyze using maximally localized Wannier functions. Photo-generated electron holes are shown to localize preferentially close to the reaction center at the surface in both configurations. In the case of the oxo species, this localization favors subsequent electron transfer steps during the oxygen evolution cycle. In the case of the peroxo configuration, this fact together with the high barrier for breaking the oxygen-oxygen bond indicates a possible loss mechanism due to hole trapping. Graphical Abstract Calculated spin density at a hematite surface with peroxo intermediate.
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Cots A, Bonete P, Sebastián D, Baglio V, Aricò AS, Gómez R. Toward Tandem Solar Cells for Water Splitting Using Polymer Electrolytes. ACS APPLIED MATERIALS & INTERFACES 2018; 10:25393-25400. [PMID: 30024728 DOI: 10.1021/acsami.8b06826] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Tandem photoelectrochemical cells, formed by two photoelectrodes with complementary light absorption, have been proposed to be a viable approach for obtaining clean hydrogen. This requires the development of new designs that allow for upscaling, which would be favored by the use of transparent polymer electrolyte membranes (PEMs) instead of conventional liquid electrolytes. This article focuses on the photoelectrochemical performance of a water-splitting tandem cell based on a phosphorus-modified α-Fe2O3 photoanode and on an iron-modified CuO photocathode, with the employment of an alkaline PEM. Such a photoelectrochemical cell works even in the absence of bias, although significant effort should be directed to the optimization of the photoelectrode/PEM interface. In addition, the results reveal that the employment of polymer electrolytes increases the stability of the device, especially in the case of the photocathode.
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Affiliation(s)
- Ainhoa Cots
- Departament de Química Física i Institut Universitari d'Electroquímica , Universitat d'Alacant , Apartat 99 , E-03080 Alicante , Spain
| | - Pedro Bonete
- Departament de Química Física i Institut Universitari d'Electroquímica , Universitat d'Alacant , Apartat 99 , E-03080 Alicante , Spain
| | - David Sebastián
- Consiglio Nazionale delle Ricerche-Instituto di Tecnologie Avanzate per l'Energia "Nicola Giordano", CNR-ITAE , Via Salita Santa Lucia sopra Contesse 5 , 98126 Messina , Italy
| | - Vincenzo Baglio
- Consiglio Nazionale delle Ricerche-Instituto di Tecnologie Avanzate per l'Energia "Nicola Giordano", CNR-ITAE , Via Salita Santa Lucia sopra Contesse 5 , 98126 Messina , Italy
| | - Antonino S Aricò
- Consiglio Nazionale delle Ricerche-Instituto di Tecnologie Avanzate per l'Energia "Nicola Giordano", CNR-ITAE , Via Salita Santa Lucia sopra Contesse 5 , 98126 Messina , Italy
| | - Roberto Gómez
- Departament de Química Física i Institut Universitari d'Electroquímica , Universitat d'Alacant , Apartat 99 , E-03080 Alicante , Spain
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14
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Ahamed I, Ulman K, Seriani N, Gebauer R, Kashyap A. Magnetoelectric ϵ-Fe 2O 3: DFT study of a potential candidate for electrode material in photoelectrochemical cells. J Chem Phys 2018; 148:214707. [PMID: 29884044 DOI: 10.1063/1.5025779] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The metastable iron oxide ϵ-Fe2O3 is rare but known for its magnetoelectric properties. While the more common alpha phase has been recognized for a long time as a suitable material for photoelectrochemical cells, its use is limited because of the electron-hole recombination problem when exposed to light. The indirect bandgap of the epsilon phase with its spontaneous polarization may offer a better potential for the application in photoelectrochemistry. Here, we report a detailed study of the electronic and structural features of the epsilon phase of iron oxide, its stability in thin films, and possible water dissociation reactions. Our studies are performed using density functional theory with a Hubbard-U correction. We observe that the stable ϵ-Fe2O3 surfaces favor the dissociation of water. The average difference in the energies of the states when water is adsorbed and when it is dissociated is roughly found to be -0.40 eV. Our results compare with the available experimental results where the epsilon phase is reported to be more efficient for the release of hydrogen from renewable oxygenates when exposed to sunlight.
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Affiliation(s)
- Imran Ahamed
- School of Basic Sciences, Indian Institute of Technology, Mandi, Himachal Pradesh 175005, India
| | - Kanchan Ulman
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
| | - Nicola Seriani
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
| | - Ralph Gebauer
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
| | - Arti Kashyap
- School of Basic Sciences, Indian Institute of Technology, Mandi, Himachal Pradesh 175005, India
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15
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Hegner FS, Cardenas-Morcoso D, Giménez S, López N, Galan-Mascaros JR. Level Alignment as Descriptor for Semiconductor/Catalyst Systems in Water Splitting: The Case of Hematite/Cobalt Hexacyanoferrate Photoanodes. CHEMSUSCHEM 2017; 10:4552-4560. [PMID: 28967707 DOI: 10.1002/cssc.201701538] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 09/29/2017] [Indexed: 06/07/2023]
Abstract
The realization of artificial photosynthesis may depend on the efficient integration of photoactive semiconductors and catalysts to promote photoelectrochemical water splitting. Many efforts are currently devoted to the processing of multicomponent anodes and cathodes in the search for appropriate synergy between light absorbers and active catalysts. No single material appears to combine both features. Many experimental parameters are key to achieve the needed synergy between both systems, without clear protocols for success. Herein, we show how computational chemistry can shed some light on this cumbersome problem. DFT calculations are useful to predict adequate energy-level alignment for thermodynamically favored hole transfer. As proof of concept, we experimentally confirmed the limited performance enhancement in hematite photoanodes decorated with cobalt hexacyanoferrate as a competent water-oxidation catalyst. Computational methods describe the misalignment of their energy levels, which is the origin of this mismatch. Photoelectrochemical studies indicate that the catalyst exclusively shifts the hematite surface state to lower potentials, which therefore reduces the onset for water oxidation. Although kinetics will still depend on interface architecture, our simple theoretical approach may identify and predict plausible semiconductor/catalyst combinations, which will speed up experimental work towards promising photoelectrocatalytic systems.
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Affiliation(s)
- Franziska Simone Hegner
- Institute of Chemical Research of Catalonia (ICIQ), Av. Paisos Catalans, 16, Tarragona, 43007, Spain
| | | | - Sixto Giménez
- Institute of Advanced Materials (INAM), Universitat Jaume I, Castellon, 12006, Spain
| | - Núria López
- Institute of Chemical Research of Catalonia (ICIQ), Av. Paisos Catalans, 16, Tarragona, 43007, Spain
| | - Jose Ramon Galan-Mascaros
- Institute of Chemical Research of Catalonia (ICIQ), Av. Paisos Catalans, 16, Tarragona, 43007, Spain
- ICREA, Pg. Lluís Companys, 23., Barcelona, 08010, Spain
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16
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Seriani N. Ab initio simulations of water splitting on hematite. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:463002. [PMID: 29057752 DOI: 10.1088/1361-648x/aa84d9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In recent years, hematite has attracted great interest as a photocatalyst for water splitting, but many questions remain unanswered about the mechanisms and the main limiting factors. For this reason, density functional theory has been used to understand the optical, electronic and chemical properties of this material at an atomistic level. Bulk doping can be used to reduce the band gap, and to increase photoabsorption and charge mobility. Charge transport takes place through adiabatic polaron hopping. The stable (0 0 0 1) surface has a stoichiometric termination when exposed to oxygen, it becomes hydroxylated in water, and it has an oxygen-rich termination under illumination in a photoelectrochemical setup. On the oxygen-rich termination, surface states are present that might act as recombination centres for electrons and holes. On the contrary, on the hydroxylated termination surface states appear only on reaction intermediates. The intrinsic surface states disappear in the presence of an overlayer of gallium oxide. The reaction of water oxidation is assumed to proceed by four proton-coupled electron transfers and it is shown to involve a nucleophilic attack with the formation of an OOH group. Calculated overpotentials are in the range of 0.5-0.6 V. Open questions and future research directions are briefly discussed.
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Affiliation(s)
- Nicola Seriani
- The Abdus Salam ICTP, Strada Costiera 11, 34151 Trieste, Italy
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18
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Ulman K, Nguyen MT, Seriani N, Piccinin S, Gebauer R. A Unified Picture of Water Oxidation on Bare and Gallium Oxide-Covered Hematite from Density Functional Theory. ACS Catal 2017. [DOI: 10.1021/acscatal.6b03162] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kanchan Ulman
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
| | - Manh-Thuong Nguyen
- Center
for Computational Physics, Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan Street, Hanoi, Vietnam
| | - Nicola Seriani
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
| | - Simone Piccinin
- CNR-IOM DEMOCRITOS, c/o SISSA, Via Bonomea 265, 34136 Trieste, Italy
| | - Ralph Gebauer
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
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19
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Yatom N, Elbaz Y, Navon S, Caspary Toroker M. Identifying the bottleneck of water oxidation by ab initio analysis of in situ optical absorbance spectrum. Phys Chem Chem Phys 2017. [DOI: 10.1039/c7cp02404e] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Hematite's (α-Fe2O3) major limitation to efficiently splitting water using sunlight is the low rate of the oxygen evolution reaction (OER).
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Affiliation(s)
- Natav Yatom
- Department of Materials Science and Engineering
- Technion – Israel Institute of Technology
- Haifa 3200003
- Israel
| | - Yuval Elbaz
- Department of Materials Science and Engineering
- Technion – Israel Institute of Technology
- Haifa 3200003
- Israel
| | - Shelly Navon
- Department of Materials Science and Engineering
- Technion – Israel Institute of Technology
- Haifa 3200003
- Israel
| | - Maytal Caspary Toroker
- Department of Materials Science and Engineering
- Technion – Israel Institute of Technology
- Haifa 3200003
- Israel
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20
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Zhang X, Cao C, Bieberle-Hütter A. Enhanced electrochemical water oxidation: the impact of nanoclusters and nanocavities. Phys Chem Chem Phys 2017; 19:31300-31305. [DOI: 10.1039/c7cp06852b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Hematite surfaces with a nanocavity are more active for OER than surfaces with nanoclusters.
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Affiliation(s)
- Xueqing Zhang
- Electrochemical Materials and Interfaces
- Dutch Institute for Fundamental Energy Research (DIFFER)
- 5612AJ Eindhoven
- The Netherlands
| | - Chonglong Cao
- School of Physics and Technology
- University of Jinan
- Jinan
- People's Republic of China
| | - Anja Bieberle-Hütter
- Electrochemical Materials and Interfaces
- Dutch Institute for Fundamental Energy Research (DIFFER)
- 5612AJ Eindhoven
- The Netherlands
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21
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Zhang X, Bieberle-Hütter A. Modeling and Simulations in Photoelectrochemical Water Oxidation: From Single Level to Multiscale Modeling. CHEMSUSCHEM 2016; 9:1223-42. [PMID: 27219662 DOI: 10.1002/cssc.201600214] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Indexed: 05/11/2023]
Abstract
This review summarizes recent developments, challenges, and strategies in the field of modeling and simulations of photoelectrochemical (PEC) water oxidation. We focus on water splitting by metal-oxide semiconductors and discuss topics such as theoretical calculations of light absorption, band gap/band edge, charge transport, and electrochemical reactions at the electrode-electrolyte interface. In particular, we review the mechanisms of the oxygen evolution reaction, strategies to lower overpotential, and computational methods applied to PEC systems with particular focus on multiscale modeling. The current challenges in modeling PEC interfaces and their processes are summarized. At the end, we propose a new multiscale modeling approach to simulate the PEC interface under conditions most similar to those of experiments. This approach will contribute to identifying the limitations at PEC interfaces. Its generic nature allows its application to a number of electrochemical systems.
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Affiliation(s)
- Xueqing Zhang
- Photo-/Electrochemical Materials and Interfaces, Dutch Institute for Fundamental Energy Research (DIFFER), De Zaale 20, 5612 AJ, Eindhoven, The Netherlands
| | - Anja Bieberle-Hütter
- Photo-/Electrochemical Materials and Interfaces, Dutch Institute for Fundamental Energy Research (DIFFER), De Zaale 20, 5612 AJ, Eindhoven, The Netherlands.
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