Impact of oxygen vacancy occupancy on charge carrier dynamics in BiVO4 photoanodes
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
Oxygen vacancies are ubiquitous in metal oxides and critical to performance, yet the impact of these states upon charge carrier dynamics important for photoelectrochemical and photocatalytic applications, remains contentious and poorly understood. A key challenge is the unambiguous identification of spectroscopic fingerprints which can be used to track their function. Herein, we employ five complementary techniques to modulate the electronic occupancy of states associated with oxygen vacancies in situ in BiVO4 photoanodes, allowing us to identify a spectral signature for the ionisation of these states. We obtain an activation energy of ̴ 0.2 eV for this ionisation process, with thermally activated electron de-trapping from these states determining the kinetics of electron extraction, consistent with improved photoelectrochemical performance at higher temperatures. Bulk, un-ionised states however, function as deep hole traps, with such trapped holes being energetically unable to drive water oxidation. These observations help address recent controversies in the literature over oxygen vacancy function, providing new insights into their impact upon photoelectrochemical performance.
Date Issued
2019-11-27
Date Acceptance
2019-10-29
Citation
Journal of the American Chemical Society, 2019, 141 (47), pp.18791-18798
ISSN
0002-7863
Publisher
American Chemical Society
Start Page
18791
End Page
18798
Journal / Book Title
Journal of the American Chemical Society
Volume
141
Issue
47
Copyright Statement
© 2019 American Chemical Society.
Sponsor
The Royal Society
The Royal Society
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/31663329
Grant Number
RSG\R1\180434
UF130178
Subjects
Science & Technology
Physical Sciences
Chemistry, Multidisciplinary
Chemistry
PHOTOGENERATED HOLES
HEMATITE PHOTOANODES
ELECTRONIC-STRUCTURE
ABSORPTION-SPECTRA
STRONTIUM-TITANATE
MONOCLINIC BIVO4
WATER OXIDATION
SURFACE
RECOMBINATION
SEPARATION
General Chemistry
03 Chemical Sciences
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2019-10-30