WO3/BiVO4: impact of charge separation at the timescale of water oxidation

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Title: WO3/BiVO4: impact of charge separation at the timescale of water oxidation
Authors: Selim, S
Francàs, L
García-Tecedor, M
Corby, S
Blackman, C
Gimenez, S
Durrant, JR
Kafizas, A
Item Type: Journal Article
Abstract: The four hole oxidation of water has long been considered the kinetic bottleneck for overall solar-driven water splitting, and thus requires the formation of long-lived photogenerated holes to overcome this kinetic barrier. However, photogenerated charges are prone to recombination unless they can be spatially separated. This can be achieved by coupling materials with staggered conduction and valence band positions, providing a thermodynamic driving force for charge separation. This has most aptly been demonstrated in the WO3/BiVO4 junction, in which quantum efficiencies for the water oxidation reaction can approach near unity. However, the charge carrier dynamics in this system remain elusive over timescales relevant to water oxidation (μs–s). In this work, the effect of charge separation on carrier lifetime, and the voltage dependence of this process, is probed using transient absorption spectroscopy and transient photocurrent measurements, revealing sub-μs electron transfer from BiVO4 to WO3. The interface formed between BiVO4 and WO3 is shown to overcome the “dead-layer effect” encountered in BiVO4 alone. Moreover, our study sheds light on the role of the WO3/BiVO4 junction in enhancing the efficiency of the water oxidation reaction, where charge separation across the WO3/BiVO4 junction improves both the yield and lifetime of holes present in the BiVO4 layer over timescales relevant to water oxidation.
Issue Date: 7-Mar-2019
Date of Acceptance: 19-Dec-2018
URI: http://hdl.handle.net/10044/1/66199
DOI: https://doi.org/10.1039/c8sc04679d
ISSN: 2041-6520
Publisher: Royal Society of Chemistry (RSC)
Start Page: 2643
End Page: 2652
Journal / Book Title: Chemical Science
Volume: 10
Issue: 9
Copyright Statement: © 2019 The Royal Society of Chemistry. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (https://creativecommons.org/licenses/by/3.0/).
Sponsor/Funder: The Royal Society
Funder's Grant Number: RSG\R1\180434
Keywords: Science & Technology
Physical Sciences
Chemistry, Multidisciplinary
Chemistry
RATE LAW ANALYSIS
PHOTOGENERATED HOLES
CARRIER DYNAMICS
BIVO4 PHOTOANODES
ABSORPTION-SPECTROSCOPY
RECOMBINATION
SURFACE
TIO2
PHOTOSYNTHESIS
ELECTRODES
03 Chemical Sciences
Publication Status: Published
Online Publication Date: 2019-01-16
Appears in Collections:Chemistry
Centre for Environmental Policy
Faculty of Natural Sciences



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