Anisotropic Electron Transport Limits Performance of Bi2WO6Photoanodes

Benjamin Moss; Haonan Le; Sacha Corby; Kazuki Morita; Shababa Selim; Carlos Sotelo-Vazquez; Yunuo Chen; Alexander Borthwick; Anna Wilson; Chris Blackman; James R. Durrant; Aron Walsh; Andreas Kafizas

doi:10.1021/acs.jpcc.0c03539

Anisotropic Electron Transport Limits Performance of Bi₂WO₆Photoanodes

Benjamin Moss, Haonan Le, Sacha Corby, Kazuki Morita, Shababa Selim, Carlos Sotelo-Vazquez, Yunuo Chen, Alexander Borthwick, Anna Wilson, Chris Blackman, James R. Durrant, Aron Walsh, Andreas Kafizas

Department of Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

3 Citations (Scopus)

Abstract

Bi2WO6 is one of the simplest members of the versatile Aurivillius oxide family of materials. As an intriguing model system for Aurivillius oxides, BiVO4 exhibits low water oxidation onset potentials (â0.5-0.6 VRHE) for driven solar water oxidation. Despite this, Bi2WO6 also produces low photocurrents in comparison to other metal oxides. Due to a lack of in situ studies, the reasons for such poor performance are not understood. In this study, Bi2WO6 photoanodes are synthesized by aerosol-assisted chemical vapor deposition. The charge carrier dynamics of Bi2WO6 are studied in situ under water oxidation conditions, and the rate of both bulk recombination and water oxidation is found to be comparable to other metal oxide photoanodes. However, the rate of electron extraction is at least 10 times slower than the slowest kinetics previously reported in an oxide photoanode. First-principles analysis indicates that the slow electron extraction kinetics are linked to a strong anisotropy in the conduction band. Preferred or epitaxial growth along the conductive axes is a strategy to overcome slow electron transport and low photocurrent densities in layered materials such as Bi2WO6.

Original language	English
Pages (from-to)	18859-18867
Number of pages	9
Journal	Journal of Physical Chemistry C
Volume	124
Issue number	35
DOIs	https://doi.org/10.1021/acs.jpcc.0c03539
Publication status	Published - 2020 Sept 3

Bibliographical note

Funding Information:
B.M. thanks the EPSRC for a doctoral training partnership award. S.C. thanks the Imperial College London for a Schrödinger Scholarship. A.K. thanks the Imperial College for a Junior Research Fellowship, the EPSRC for a Capital Award Emphasising Support for Early Career Researchers, and the Royal Society for an Equipment Grant (RSG\R1\180434). For the CVD equipment used in this work, we thank Mr. Lee Tooley for design and construction and Mr. Steven Atkins for electrical work. We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which are partially funded by the EPSRC (EP/P020194/1). This research has been partially supported by the Keio University Research Grant for Young Researcher’s Program, the Yoshida Scholarship Foundation, the Japan Student Services Organization, and the Centre for Doctoral Training on Theory and Simulation of Materials at Imperial College London.

Publisher Copyright:
Copyright © 2020 American Chemical Society.

All Science Journal Classification (ASJC) codes

Electronic, Optical and Magnetic Materials
Energy(all)
Physical and Theoretical Chemistry
Surfaces, Coatings and Films

Access to Document

10.1021/acs.jpcc.0c03539

Cite this

@article{d0d0c0c2b6284c62809bceab9604cbb6,

title = "Anisotropic Electron Transport Limits Performance of Bi2WO6Photoanodes",

abstract = "Bi2WO6 is one of the simplest members of the versatile Aurivillius oxide family of materials. As an intriguing model system for Aurivillius oxides, BiVO4 exhibits low water oxidation onset potentials ({\^a}0.5-0.6 VRHE) for driven solar water oxidation. Despite this, Bi2WO6 also produces low photocurrents in comparison to other metal oxides. Due to a lack of in situ studies, the reasons for such poor performance are not understood. In this study, Bi2WO6 photoanodes are synthesized by aerosol-assisted chemical vapor deposition. The charge carrier dynamics of Bi2WO6 are studied in situ under water oxidation conditions, and the rate of both bulk recombination and water oxidation is found to be comparable to other metal oxide photoanodes. However, the rate of electron extraction is at least 10 times slower than the slowest kinetics previously reported in an oxide photoanode. First-principles analysis indicates that the slow electron extraction kinetics are linked to a strong anisotropy in the conduction band. Preferred or epitaxial growth along the conductive axes is a strategy to overcome slow electron transport and low photocurrent densities in layered materials such as Bi2WO6.",

author = "Benjamin Moss and Haonan Le and Sacha Corby and Kazuki Morita and Shababa Selim and Carlos Sotelo-Vazquez and Yunuo Chen and Alexander Borthwick and Anna Wilson and Chris Blackman and Durrant, {James R.} and Aron Walsh and Andreas Kafizas",

note = "Funding Information: B.M. thanks the EPSRC for a doctoral training partnership award. S.C. thanks the Imperial College London for a Schr{\"o}dinger Scholarship. A.K. thanks the Imperial College for a Junior Research Fellowship, the EPSRC for a Capital Award Emphasising Support for Early Career Researchers, and the Royal Society for an Equipment Grant (RSG\R1\180434). For the CVD equipment used in this work, we thank Mr. Lee Tooley for design and construction and Mr. Steven Atkins for electrical work. We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which are partially funded by the EPSRC (EP/P020194/1). This research has been partially supported by the Keio University Research Grant for Young Researcher{\textquoteright}s Program, the Yoshida Scholarship Foundation, the Japan Student Services Organization, and the Centre for Doctoral Training on Theory and Simulation of Materials at Imperial College London. Publisher Copyright: Copyright {\textcopyright} 2020 American Chemical Society.",

year = "2020",

month = sep,

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doi = "10.1021/acs.jpcc.0c03539",

language = "English",

volume = "124",

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AU - Moss, Benjamin

AU - Le, Haonan

AU - Corby, Sacha

AU - Morita, Kazuki

AU - Selim, Shababa

AU - Sotelo-Vazquez, Carlos

AU - Chen, Yunuo

AU - Borthwick, Alexander

AU - Wilson, Anna

AU - Blackman, Chris

AU - Durrant, James R.

AU - Walsh, Aron

AU - Kafizas, Andreas

N1 - Funding Information: B.M. thanks the EPSRC for a doctoral training partnership award. S.C. thanks the Imperial College London for a Schrödinger Scholarship. A.K. thanks the Imperial College for a Junior Research Fellowship, the EPSRC for a Capital Award Emphasising Support for Early Career Researchers, and the Royal Society for an Equipment Grant (RSG\R1\180434). For the CVD equipment used in this work, we thank Mr. Lee Tooley for design and construction and Mr. Steven Atkins for electrical work. We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which are partially funded by the EPSRC (EP/P020194/1). This research has been partially supported by the Keio University Research Grant for Young Researcher’s Program, the Yoshida Scholarship Foundation, the Japan Student Services Organization, and the Centre for Doctoral Training on Theory and Simulation of Materials at Imperial College London. Publisher Copyright: Copyright © 2020 American Chemical Society.

PY - 2020/9/3

Y1 - 2020/9/3

N2 - Bi2WO6 is one of the simplest members of the versatile Aurivillius oxide family of materials. As an intriguing model system for Aurivillius oxides, BiVO4 exhibits low water oxidation onset potentials (â0.5-0.6 VRHE) for driven solar water oxidation. Despite this, Bi2WO6 also produces low photocurrents in comparison to other metal oxides. Due to a lack of in situ studies, the reasons for such poor performance are not understood. In this study, Bi2WO6 photoanodes are synthesized by aerosol-assisted chemical vapor deposition. The charge carrier dynamics of Bi2WO6 are studied in situ under water oxidation conditions, and the rate of both bulk recombination and water oxidation is found to be comparable to other metal oxide photoanodes. However, the rate of electron extraction is at least 10 times slower than the slowest kinetics previously reported in an oxide photoanode. First-principles analysis indicates that the slow electron extraction kinetics are linked to a strong anisotropy in the conduction band. Preferred or epitaxial growth along the conductive axes is a strategy to overcome slow electron transport and low photocurrent densities in layered materials such as Bi2WO6.

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