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Xiao L, Spies JA, Sheehan CJ, Zeng Z, Gao Y, Gao T, Ehrlacher A, Zuerch MW, Brudvig GW, Mallouk TE. Electron Transfer Dynamics at Dye-Sensitized SnO 2/TiO 2 Core/Shell Electrodes in Aqueous/Nonaqueous Electrolyte Mixtures. J Am Chem Soc 2024; 146:18117-18127. [PMID: 38900942 DOI: 10.1021/jacs.4c05187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
The dynamics of photoinduced electron transfer were measured at dye-sensitized photoanodes in aqueous (acetate buffer), nonaqueous (acetonitrile), and mixed solvent electrolytes by nanosecond transient absorption spectroscopy (TAS) and ultrafast optical-pump terahertz-probe spectroscopy (OPTP). Higher injection efficiencies were found in mixed solvent electrolytes for dye-sensitized SnO2/TiO2 core/shell electrodes, whereas the injection efficiency of dye-sensitized TiO2 electrodes decreased with the increasing acetonitrile concentration. The trend in injection efficiency for the TiO2 electrodes was consistent with the solvent-dependent trend in the semiconductor flat band potential. Photoinduced electron injection in core/shell electrodes has been understood as a two-step process involving ultrafast electron trapping in the TiO2 shell followed by slower electron transfer to the SnO2 core. The driving force for shell-to-core electron transfer increases as the flat band potential of TiO2 shifts negatively with increasing concentrations of acetonitrile. In acetonitrile-rich electrolytes, electron injection is suppressed due to the very negative flat band potential of the TiO2 shell. Interestingly, a net negative photoconductivity in the SnO2 core is observed in mixed solvent electrolytes by OPTP. We hypothesize that an electric field is formed across the TiO2 shell from the oxidized dye molecules after injection. Conduction band electrons in SnO2 are trapped at the core/shell interface by the electric field, resulting in a negative photoconductivity transient. The overall electron injection efficiency of the dye-sensitized SnO2/TiO2 core/shell photoanodes is optimized in mixed solvents. The ultrafast transient conductivity data illustrate the crucial role of the electrolyte in regulating the driving forces for electron injection and charge separation at dye-sensitized semiconductor interfaces.
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Affiliation(s)
- Langqiu Xiao
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Jacob A Spies
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Colton J Sheehan
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Zichen Zeng
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Yunhan Gao
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Tianyue Gao
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Annika Ehrlacher
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Michael W Zuerch
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Gary W Brudvig
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Thomas E Mallouk
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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2
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Nedzbala HS, Westbroek D, Margavio HRM, Yang H, Noh H, Magpantay SV, Donley CL, Kumbhar AS, Parsons GN, Mayer JM. Photoelectrochemical Proton-Coupled Electron Transfer of TiO 2 Thin Films on Silicon. J Am Chem Soc 2024; 146:10559-10572. [PMID: 38564642 DOI: 10.1021/jacs.4c00014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
TiO2 thin films are often used as protective layers on semiconductors for applications in photovoltaics, molecule-semiconductor hybrid photoelectrodes, and more. Experiments reported here show that TiO2 thin films on silicon are electrochemically and photoelectrochemically reduced in buffered acetonitrile at potentials relevant to photoelectrocatalysis of CO2 reduction, N2 reduction, and H2 evolution. On both n-type Si and irradiated p-type Si, TiO2 reduction is proton-coupled with a 1e-:1H+ stoichiometry, as demonstrated by the Nernstian dependence of the Ti4+/3+ E1/2 on the buffer pKa. Experiments were conducted with and without illumination, and a photovoltage of ∼0.6 V was observed across 20 orders of magnitude in proton activity. The 4 nm films are almost stoichiometrically reduced under mild conditions. The reduced films catalytically transfer protons and electrons to hydrogen atom acceptors, based on cyclic voltammogram, bulk electrolysis, and other mechanistic evidence. TiO2/Si thus has the potential to photoelectrochemically generate high-energy H atom carriers. Characterization of the TiO2 films after reduction reveals restructuring with the formation of islands, rendering TiO2 films as a potentially poor choice as protecting films or catalyst supports under reducing and protic conditions. Overall, this work demonstrates that atomic layer deposition TiO2 films on silicon photoelectrodes undergo both chemical and morphological changes upon application of potentials only modestly negative of RHE in these media. While the results should serve as a cautionary tale for researchers aiming to immobilize molecular monolayers on "protective" metal oxides, the robust proton-coupled electron transfer reactivity of the films introduces opportunities for the photoelectrochemical generation of reactive charge-carrying mediators.
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Affiliation(s)
- Hannah S Nedzbala
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Dalaney Westbroek
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Hannah R M Margavio
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27603, United States
| | - Hyuenwoo Yang
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27603, United States
| | - Hyunho Noh
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Samantha V Magpantay
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Carrie L Donley
- Department of Chemistry, Chapel Hill Analytical and Nanofabrication Laboratory (CHANL), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Amar S Kumbhar
- Department of Chemistry, Chapel Hill Analytical and Nanofabrication Laboratory (CHANL), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Gregory N Parsons
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27603, United States
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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3
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Bruggeman DF, Detz RJ, Mathew S, Reek JNH. Increased solar-driven chemical transformations through surface-induced benzoperylene aggregation in dye-sensitized photoanodes. Photochem Photobiol Sci 2024; 23:503-516. [PMID: 38363531 DOI: 10.1007/s43630-024-00534-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 01/04/2024] [Indexed: 02/17/2024]
Abstract
The impact of benzo[ghi]perylenetriimide (BPTI) dye aggregation on the performance of photoelectrochemical devices was explored, through imide-substitution with either alkyl (BPTI-A, 2-ethylpropyl) or bulky aryl (BPTI-B, 2,6-diisopropylphenyl) moieties, to, respectively, enable or suppress aggregation. While both dyes demonstrated similar monomeric optoelectronic properties in solution, adsorption onto mesoporous SnO2 revealed different behavior, with BPTI-A forming aggregates via π-stacking and BPTI-B demonstrating reduced aggregation in the solid state. BPTI photoanodes were tested in dye-sensitized solar cells (DSSCs) before application to dye-sensitized photoelectrochemical cells (DSPECs) for Br2 production (a strong oxidant) coupled to H2 generation (a solar fuel). BPTI-A demonstrated a twofold higher dye loading of the SnO2 surface than BPTI-B, resulting in a fivefold enhancement to both photocurrent and Br2 production. The enhanced output of the photoelectrochemical systems (with respect to dye loading) was attributed to both J- and H- aggregation phenomena in BPTI-A photoanodes that lead to improved light harvesting. Our investigation provides a strategy to exploit self-assembly via aggregation to improve molecular light-harvesting and charge separation properties that can be directly applied to dye-sensitized photoelectrochemical devices.
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Affiliation(s)
- Didjay F Bruggeman
- Homogeneous, Supramolecular and Bioinspired Catalysis, van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Remko J Detz
- Energy Transition Studies, Netherlands Organization for Applied Scientific Research (TNO), Radarweg 60, Amsterdam, The Netherlands
| | - Simon Mathew
- Homogeneous, Supramolecular and Bioinspired Catalysis, van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Joost N H Reek
- Homogeneous, Supramolecular and Bioinspired Catalysis, van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
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4
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Mayer JM. Bonds over Electrons: Proton Coupled Electron Transfer at Solid-Solution Interfaces. J Am Chem Soc 2023; 145:7050-7064. [PMID: 36943755 PMCID: PMC10080693 DOI: 10.1021/jacs.2c10212] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
This Perspective argues that most redox reactions of materials at an interface with a protic solution involve net proton-coupled electron transfer (PCET) (or other cation-coupled ET). This view contrasts with the traditional electron-transfer-focused view of redox reactions at semiconductors, but redox processes at metal surfaces are often described as PCET. Taking a thermodynamic perspective, transfer of an electron is typically accompanied by a stoichiometric proton, much as the chemistry of lithium-ion batteries involves coupled transfers of e- and Li+. The PCET viewpoint implicates the surface-H bond dissociation free energy (BDFE) as the preeminent energetic parameter and its conceptual equivalents, the electrochemical ne-/nH+ potential versus the reversible hydrogen electrode (RHE) and the free energy of hydrogenation, ΔG°H. These parameters capture the thermochemistry of PCET at interfaces better than electronic parameters such as Fermi energies, electron chemical potentials, flat-band potentials, or band-edge energies. A unified picture of PCET at metal and semiconductor surfaces is presented. Exceptions, limitations, implications, and future directions motivated by this approach are described.
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Affiliation(s)
- James M Mayer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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5
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Peper JL, Gentry NE, Boudy B, Mayer JM. Aqueous TiO 2 Nanoparticles React by Proton-Coupled Electron Transfer. Inorg Chem 2021; 61:767-777. [PMID: 34967207 DOI: 10.1021/acs.inorgchem.1c03125] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Redox reactions of aqueous colloidal TiO2 4 nm nanoparticles (NPs) have been examined, including both citrate-capped and uncapped NPs (c-TiO2 and uc-TiO2). Photoreduction gave stable blue colloidal c-TiO2R NPs with 10-60 electrons per particle. Equilibration of these reduced NPs with soluble redox reagents such as methylviologen (MV2+) provided measurements of the colloid reduction potential as a function of pH. The potentials of c-TiO2 from pH 2-9 varied linearly with pH, with a slope of -60 ± 5 mV/pH. Estimates of the potential at pH 12 were consistent with extrapolating that line to high pH. The reduction potentials did not correlate with the zeta potentials (ζ) or the surface charge of the NPs across this pH range. Similar reduction potentials were observed for c- and uc-TiO2 at low pH even though they have quite different ζ potentials. These results show that the common surface-charging explanation of the pH dependence is not tenable in these systems. Oxidation of reduced c-TiO2R with the electron-transfer oxidant potassium triiodide (KI3) occurred with a significant drop in pH, showing that protons were released when the electrons were removed from the NPs. Smaller pH drops were observed for the proton-coupled electron transfer (PCET) reagents O2 (air) and 4-MeO-TEMPO (4-methoxy-2,2,6,6-tetramethylpiperine-1-oxy radical). The difference in the number of protons released with KI3 vs O2 and 4-MeO-TEMPO was roughly one proton per electron removed. Thus, the thermodynamically preferred reactivity of these colloidal TiO2 NPs is PCET over the pH 2-13 range studied. The measured redox potentials refer to the chemical process TiO2 + H+ + e- → TiO2·e-,H+; and therefore they do not correspond with an electronic energy such as a conduction band edge or flat band potential. The 1e-/1H+ stoichiometry means that the TiO2 reduction potentials correspond to a TiO2-H bond dissociation free energy (BDFE), determined to be 49 ± 2 kcal mol-1. The PCET description is consistent with the pH dependence of E(TiO2/TiO2·e-,H+), the release of protons upon oxidation, the lack of correlation with ζ potentials, the similarity of capped and uncapped NPs, and the small change in the potential and BDFE from the first to the last electron/proton pair (H atom) removed. This behavior is suggested to be the norm for redox-active oxide/water interfaces.
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Affiliation(s)
- Jennifer L Peper
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Noreen E Gentry
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Benjamin Boudy
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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6
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Dashtian K, Shahbazi S, Tayebi M, Masoumi Z. A review on metal-organic frameworks photoelectrochemistry: A headlight for future applications. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.214097] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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7
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Pati PB, Abdellah M, Diring S, Hammarström L, Odobel F. Molecular Triad Containing a TEMPO Catalyst Grafted on Mesoporous Indium Tin Oxide as a Photoelectrocatalytic Anode for Visible Light-Driven Alcohol Oxidation. CHEMSUSCHEM 2021; 14:2902-2913. [PMID: 33973386 DOI: 10.1002/cssc.202100843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/05/2021] [Indexed: 06/12/2023]
Abstract
Photoelectrochemical cells based on semiconductors are among the most studied methods of artificial photosynthesis. This study concerns the immobilization, on a mesoporous conducting indium tin oxide electrode (nano-ITO), of a molecular triad (NDADI-P-Ru-TEMPO) composed of a ruthenium tris-bipyridine complex (Ru) as photosensitizer, connected at one end to 2,2,6,6-tetramethyl-1-piperidine N-oxyl (TEMPO) as alcohol oxidation catalyst and at the other end to the electron acceptor naphthalenedicarboxyanhydride dicarboximide (NDADI). Light irradiation of NDADI-P-Ru-TEMPO grafted to nano-ITO in a pH 10 carbonate buffer effects selective oxidation of para-methoxybenzyl alcohol (MeO-BA) to para-methoxybenzaldehyde with a TON of approximately 150 after 1 h of photolysis at a bias of 0.4 V vs. SCE. The faradaic efficiency is found to be of 80±5 %. The photophysical study indicates that photoinduced electron transfer from the Ru complex to NDADI is a slow process and must compete with direct electron injection into ITO to have a better performing system. This work sheds light on some of the important ways to design more efficient molecular systems for the preparation of photoelectrocatalytic cells based on catalyst-dye-acceptor arrays immobilized on conducting electrodes.
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Affiliation(s)
- Palas Baran Pati
- Université de Nantes, CNRS, CEISAM UMR 6230, 44000, Nantes, France
| | - Mohamed Abdellah
- Department of Chemistry, Ångström Laboratories, Uppsala University, Box 523, SE75120, Uppsala, Sweden
- Department of Chemistry, Qena Faculty of Science, South Valley University, 83523, Qena, Egypt
| | - Stéphane Diring
- Université de Nantes, CNRS, CEISAM UMR 6230, 44000, Nantes, France
| | - Leif Hammarström
- Department of Chemistry, Ångström Laboratories, Uppsala University, Box 523, SE75120, Uppsala, Sweden
| | - Fabrice Odobel
- Université de Nantes, CNRS, CEISAM UMR 6230, 44000, Nantes, France
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8
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Peper JL, Gentry NE, Brezny AC, Field MJ, Green MT, Mayer JM. Different Kinetic Reactivity of Electrons in Distinct TiO 2 Nanoparticle Trap States. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:680-690. [PMID: 34178203 PMCID: PMC8232823 DOI: 10.1021/acs.jpcc.0c10633] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Electrons added to TiO2 and other semiconductors often occupy trap states, whose reactivity can determine the catalytic and stoichiometric chemistry of the material. We previously showed that reduced aqueous colloidal TiO2 nanoparticles have two distinct classes of thermally-equilibrated trapped electrons, termed Red/e - and Blue/e -. Presented here are parallel optical and electron paramagnetic resonance (EPR) kinetic studies of the reactivity of these electrons with solution-based oxidants. Optical stopped-flow measurements monitoring reactions of TiO2/e - with sub-stoichiometric oxidants showed a surprising pattern: an initial fast (seconds) decrease in TiO2/e - absorbance followed by a secondary, slow (minutes) increase in the broad TiO2/e - optical feature. Analysis revealed that the fast decrease is due to the preferential oxidation of the Red/e - trap states, and the slow increase results from re-equilibration of electrons from Blue to Red states. This kinetic model was confirmed by freeze-quench EPR measurements. Quantitative analysis of the kinetic data demonstrated that Red/e - react ~5 times faster than Blue/e - with the nitroxyl radical oxidant, 4-MeO-TEMPO. Similar reactivity patterns were also observed in oxidations of TiO2/e - by O2, which like 4-MeO-TEMPO is a proton-coupled electron transfer (PCET) oxidant, and by the pure electron transfer (ET) oxidant KI3. This suggests that the faster intrinsic reactivity of one trap state over another on the seconds-minutes timescale is likely a general feature of reduced TiO2 reactivity. This differential trap state reactivity is likely to influence the performance of TiO2 in photochemical/electrochemical devices, and it suggests an opportunity for tuning catalysis.
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Affiliation(s)
- Jennifer L. Peper
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Noreen E. Gentry
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Anna C. Brezny
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
- Department of Chemistry, Skidmore College, Saratoga Springs, New York 12866, United States
| | - Mackenzie J. Field
- Department of Chemistry and Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Michael T. Green
- Department of Chemistry and Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - James M. Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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9
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Wang D, Huang Q, Shi W, You W, Meyer TJ. Application of Atomic Layer Deposition in Dye-Sensitized Photoelectrosynthesis Cells. TRENDS IN CHEMISTRY 2021. [DOI: 10.1016/j.trechm.2020.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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10
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Lin Y, Yan Y, Peng W, Qiao X, Huang D, Ji H, Chen C, Ma W, Zhao J. Crucial Effect of Ti-H Species Generated in the Visible-Light-Driven Transformations: Slowed-Down Proton-Coupled Electron Transfer. J Phys Chem Lett 2020; 11:3941-3946. [PMID: 32353238 DOI: 10.1021/acs.jpclett.0c01196] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Despite the fact that proton-coupled electron transfer (PCET) has been hypothesized to play a pivotal role in the power conversion efficiency (PCE) of TiO2-based solar-energy applications, the specific relationship between the intrinsic nature of visible-light (Vis)-driven PCET reactions and limited PCE gains has not yet been well revealed. Here we studied the detailed kinetics of reactions between various alcohols and radicals (tBu3ArO•/TEMPO) on a TiO2 photocatalyst under dye-sensitization Vis irradiation versus direct ultraviolet (UV) irradiation. We found that the rates of Vis-driven reactions were much slower than those of UV-driven reactions under identical light intensity. A similar phenomenon was observed under the off-line dark-reaction conditions in which TiO2 was prereduced by alcohols. The rapid formation and difficult breakage of the stable "Ti-H" intermediate were proposed to account for the slowed-down PCET effect. This finding revealed an inherent bottleneck in Vis-driven energy conversion applications.
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Affiliation(s)
- Yuhan Lin
- Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Yan Yan
- Jiangsu University, Zhenjiang 212013, P. R. China
| | - Wei Peng
- Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Xiaofeng Qiao
- Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Di Huang
- Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Hongwei Ji
- Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Chuncheng Chen
- Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Wanhong Ma
- Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Jincai Zhao
- Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
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11
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Ortiz-Rodríguez JC, Santana JA, Méndez-Hernández DD. Linear correlation models for the redox potential of organic molecules in aqueous solutions. J Mol Model 2020; 26:70. [PMID: 32146589 DOI: 10.1007/s00894-020-4331-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Accepted: 02/23/2020] [Indexed: 01/11/2023]
Abstract
In this study, we use the molecular orbital energy approximation (MOEA) and the energy difference approximation (EDA) to build linear correlation models for the redox potentials of 53 organic compounds in aqueous solutions. The molecules evaluated include nitroxides, phenols, and amines. Both the MOEA and EDA methods yield similar correlation models, however, the MOEA method is less computationally expensive. Correlation coefficients (R2) below 0.3 and mean absolute errors above 0.25 V were found for correlation models built without solvent effects. When explicit water molecules and a continuum solvent model are added to the calculations, correlation coefficients close to 0.8 are reached, and mean absolute errors below 0.18 V are obtained. The incorporation of solvent effects is necessary for good correlation models, particularly for redox processes of charged molecules in aqueous solutions. A comparison of the correlation models from different methodologies is provided. Graphical abstract.
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Affiliation(s)
| | - Juan A Santana
- Department of Chemistry, University of Puerto Rico at Cayey, Cayey, PR, 00736, USA
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12
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Xu P, Gray CL, Xiao L, Mallouk TE. Charge Recombination with Fractional Reaction Orders in Water-Splitting Dye-Sensitized Photoelectrochemical Cells. J Am Chem Soc 2018; 140:11647-11654. [DOI: 10.1021/jacs.8b04878] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Pengtao Xu
- Departments of Chemistry, Physics, and Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Christopher L. Gray
- Departments of Chemistry, Physics, and Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Langqiu Xiao
- Departments of Chemistry, Physics, and Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Thomas E. Mallouk
- Departments of Chemistry, Physics, and Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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13
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Dye-sensitized photoelectrochemical water oxidation through a buried junction. Proc Natl Acad Sci U S A 2018; 115:6946-6951. [PMID: 29915092 DOI: 10.1073/pnas.1804728115] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Water oxidation has long been a challenge in artificial photosynthetic devices that convert solar energy into fuels. Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) provide a modular approach for integrating light-harvesting molecules with water-oxidation catalysts on metal-oxide electrodes. Despite recent progress in improving the efficiency of these devices by introducing good molecular water-oxidation catalysts, WS-DSPECs have poor stability, owing to the oxidation of molecular components at very positive electrode potentials. Here we demonstrate that a solid-state dye-sensitized solar cell (ss-DSSC) can be used as a buried junction for stable photoelectrochemical water splitting. A thin protecting layer of TiO2 grown by atomic layer deposition (ALD) stabilizes the operation of the photoanode in aqueous solution, although as a solar cell there is a performance loss due to increased series resistance after the coating. With an electrodeposited iridium oxide layer, a photocurrent density of 1.43 mA cm-2 was observed in 0.1 M pH 6.7 phosphate solution at 1.23 V versus reversible hydrogen electrode, with good stability over 1 h. We measured an incident photon-to-current efficiency of 22% at 540 nm and a Faradaic efficiency of 43% for oxygen evolution. While the potential profile of the catalyst layer suggested otherwise, we confirmed the formation of a buried junction in the as-prepared photoelectrode. The buried junction design of ss-DSSs adds to our understanding of semiconductor-electrocatalyst junction behaviors in the presence of a poor semiconducting material.
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14
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Grądzka I, Gierszewski M, Karolczak J, Ziółek M. Comparison of charge transfer dynamics in polypyridyl ruthenium sensitizers for solar cells and water splitting systems. Phys Chem Chem Phys 2018; 20:7710-7720. [PMID: 29498393 DOI: 10.1039/c8cp00258d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Standard ruthenium components of dye-sensitized solar cells (sensitizer N719) and dye-sensitized photoelectrochemical cells (sensitizer RuP and water oxidation catalyst RuOEC) are investigated in the same solar cell configuration to compare their photodynamics and charge separation efficiency. The samples are studied on time scales from femtoseconds to seconds by means of transient absorption, time-resolved emission and electrochemical impedance measurements. RuP shows significantly slower electron injection into a mesoporous titania electrode and enhanced fast (sub-ns) electron recombination with respect to those of N719. Moreover, RuOEC is found to be responsible for partial light absorption and electron injection with low efficiency. The obtained results reveal new insights into the reasons for the lower charge separation efficiency in water splitting systems with respect to that in solar cells. The important role of the initial processes occurring at the dye-titania interface within the first nanoseconds in this efficiency is emphasized.
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Affiliation(s)
- Iwona Grądzka
- Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University in Poznań, Umultowska 85, 61-614 Poznań, Poland.
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15
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Hoffeditz WL, Pellin MJ, Farha OK, Hupp JT. Determining the Conduction Band-Edge Potential of Solar-Cell-Relevant Nb 2O 5 Fabricated by Atomic Layer Deposition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:9298-9306. [PMID: 28499092 DOI: 10.1021/acs.langmuir.7b00683] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Often key to boosting photovoltages in photoelectrochemical and related solar-energy-conversion devices is the preferential slowing of rates of charge recombination-especially recombination at semiconductor/solution, semiconductor/polymer, or semiconductor/perovskite interfaces. In devices featuring TiO2 as the semiconducting component, a common approach to slowing recombination is to install an ultrathin metal oxide barrier layer or trap-passivating layer atop the semiconductor, with the needed layer often being formed via atomic layer deposition (ALD). A particularly promising barrier layer material is Nb2O5. Its conduction-band-edge potential ECB is low enough that charge injection from an adsorbed molecular, polymeric, or solid-state light absorber and into the semiconductor can still occur, but high enough that charge recombination is inhibited. While a few measurements of ECB have been reported for conventionally synthesized, bulk Nb2O5, none have been described for ALD-fabricated versions. Here, we specifically determine the conduction-band-edge energy of ALD-fabricated Nb2O5 relative to that of TiO2. We find that, while the value for ALD-Nb2O5 is indeed higher than that for TiO2, the difference is less than anticipated based on measurements of conventionally synthesized Nb2O5 and is dependent on the thermal history of the material. The implications of the findings for optimization of competing interfacial rate processes, and therefore photovoltages, are briefly discussed.
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Affiliation(s)
- William L Hoffeditz
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Michael J Pellin
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Material Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States
| | - Omar K Farha
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Department of Chemistry, Faculty of Science, King Abdulaziz University , Jeddah 21589, Saudi Arabia
| | - Joseph T Hupp
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Material Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States
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16
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Kirner JT, Finke RG. Sensitization of Nanocrystalline Metal Oxides with a Phosphonate-Functionalized Perylene Diimide for Photoelectrochemical Water Oxidation with a CoO x Catalyst. ACS APPLIED MATERIALS & INTERFACES 2017; 9:27625-27637. [PMID: 28727440 DOI: 10.1021/acsami.7b05874] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A planar organic thin film composed of a perylene diimide dye (N,N'-bis(phosphonomethyl)-3,4,9,10-perylenediimide, PMPDI) with photoelectrochemically deposited cobalt oxide (CoOx) catalyst was previously shown to photoelectrochemically oxidize water (DOI: 10.1021/am405598w). Herein, the same PMPDI dye is studied for the sensitization of different nanostructured metal oxide (nano-MOx) films in a dye-sensitized photoelectrochemical cell architecture. Dye adsorption kinetics and saturation decreases in the order TiO2 > SnO2 ≫ WO3. Despite highest initial dye loading on TiO2 films, photocurrent with hydroquinone (H2Q) sacrificial reductant in pH 7 aqueous solution is much higher on SnO2 films, likely due to a higher driving force for charge injection into the more positive conduction band energy of SnO2. Dyeing conditions and SnO2 film thickness were subsequently optimized to achieve light-harvesting efficiency >99% at the λmax of the dye, and absorbed photon-to-current efficiency of 13% with H2Q, a 2-fold improvement over the previous thin-film architecture. A CoOx water-oxidation catalyst was photoelectrochemically deposited, allowing for photoelectrochemical water oxidation with a faradaic efficiency of 31 ± 7%, thus demonstrating the second example of a water-oxidizing, dye-sensitized photoelectrolysis cell composed entirely of earth-abundant materials. However, deposition of CoOx always results in lower photocurrent due to enhanced recombination between catalyst and photoinjected electrons in SnO2, as confirmed by open-circuit photovoltage measurements. Possible future studies to enhance photoanode performance are discussed, including alternative catalyst deposition strategies or structural derivatization of the perylene dye.
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Affiliation(s)
- Joel T Kirner
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523, United States
| | - Richard G Finke
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523, United States
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17
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Yan Y, Shi W, Yuan Z, He S, Li D, Meng Q, Ji H, Chen C, Ma W, Zhao J. The Formation of Ti–H Species at Interface Is Lethal to the Efficiency of TiO2-Based Dye-Sensitized Devices. J Am Chem Soc 2017; 139:2083-2089. [DOI: 10.1021/jacs.6b12324] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Yan Yan
- Key
Laboratory of Photochemistry and State Key Laboratory for Structural
Chemistry of Unstable and Stable Species, Beijing National Laboratory
for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China 100190
- School
of Chemistry and Chemical Engineering, Jiangsu University, No. 301, Xuefu Road, Zhenjiang, P. R. China 212013
| | - Weidong Shi
- School
of Chemistry and Chemical Engineering, Jiangsu University, No. 301, Xuefu Road, Zhenjiang, P. R. China 212013
| | - Zhen Yuan
- Key
Laboratory of Photochemistry and State Key Laboratory for Structural
Chemistry of Unstable and Stable Species, Beijing National Laboratory
for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China 100190
| | - Shenggui He
- Key
Laboratory of Photochemistry and State Key Laboratory for Structural
Chemistry of Unstable and Stable Species, Beijing National Laboratory
for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China 100190
| | - Dongmei Li
- Key
Laboratory for Renewable Energy (CAS), Beijing Key Laboratory for
New Energy Materials and Devices, Beijing National Laboratory for
Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, P. R. China 100190
| | - Qingbo Meng
- Key
Laboratory for Renewable Energy (CAS), Beijing Key Laboratory for
New Energy Materials and Devices, Beijing National Laboratory for
Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, P. R. China 100190
| | - Hongwei Ji
- Key
Laboratory of Photochemistry and State Key Laboratory for Structural
Chemistry of Unstable and Stable Species, Beijing National Laboratory
for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China 100190
| | - Chuncheng Chen
- Key
Laboratory of Photochemistry and State Key Laboratory for Structural
Chemistry of Unstable and Stable Species, Beijing National Laboratory
for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China 100190
| | - Wanhong Ma
- Key
Laboratory of Photochemistry and State Key Laboratory for Structural
Chemistry of Unstable and Stable Species, Beijing National Laboratory
for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China 100190
| | - Jincai Zhao
- Key
Laboratory of Photochemistry and State Key Laboratory for Structural
Chemistry of Unstable and Stable Species, Beijing National Laboratory
for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China 100190
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18
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McCool NS, Swierk JR, Nemes CT, Schmuttenmaer CA, Mallouk TE. Dynamics of Electron Injection in SnO2/TiO2 Core/Shell Electrodes for Water-Splitting Dye-Sensitized Photoelectrochemical Cells. J Phys Chem Lett 2016; 7:2930-4. [PMID: 27414977 DOI: 10.1021/acs.jpclett.6b01528] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) rely on photoinduced charge separation at a dye/semiconductor interface to supply electrons and holes for water splitting. To improve the efficiency of charge separation and reduce charge recombination in these devices, it is possible to use core/shell structures in which photoinduced electron transfer occurs stepwise through a series of progressively more positive acceptor states. Here, we use steady-state emission studies and time-resolved terahertz spectroscopy to follow the dynamics of electron injection from a photoexcited ruthenium polypyridyl dye as a function of the TiO2 shell thickness on SnO2 nanoparticles. Electron injection proceeds directly into the SnO2 core when the thickness of the TiO2 shell is less than 5 Å. For thicker shells, electrons are injected into the TiO2 shell and trapped, and are then released into the SnO2 core on a time scale of hundreds of picoseconds. As the TiO2 shell increases in thickness, the probability of electron trapping in nonmobile states within the shell increases. Conduction band electrons in the TiO2 shell and the SnO2 core can be differentiated on the basis of their mobility. These observations help explain the observation of an optimum shell thickness for core/shell water-splitting electrodes.
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Affiliation(s)
| | - John R Swierk
- Department of Chemistry and Energy Sciences Institute, Yale University , 225 Prospect Street, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
| | - Coleen T Nemes
- Department of Chemistry and Energy Sciences Institute, Yale University , 225 Prospect Street, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
| | - Charles A Schmuttenmaer
- Department of Chemistry and Energy Sciences Institute, Yale University , 225 Prospect Street, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
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