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.
Bibliographical noteFunding 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.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films