Photoelectrochemical evaluation of SILAR-deposited nanoporous BiVO4 photoanodes for solar-driven water splitting

We report a photoelectrochemical investigation of BiVO4 photoanodes prepared by successive ionic layer adsorption and reaction (SILAR), a facile method that yields uniform nanoporous films. After characterization of the phase, morphology, composition, and optical properties of the prepared films, th...

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Bibliographic Details
Published in:	Nano materials science Vol. 2; no. 3; pp. 227 - 234
Main Authors:	Haji Yassin, Siti Nur'ain, Sim, Adrian Soong Leong, Jennings, James Robert
Format:	Journal Article
Language:	English
Published:	Elsevier B.V 01-09-2020 KeAi Communications Co., Ltd
Subjects:	Bismuth vanadate BiVO4 Charge collection efficiency Charge separation efficiency Electron diffusion length Solar water splitting Water oxidation efficiency Charge collection efficiency Electron diffusion length Water oxidation efficiency BiVO4 Solar water splitting Bismuth vanadate Charge separation efficiency
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Summary:	We report a photoelectrochemical investigation of BiVO4 photoanodes prepared by successive ionic layer adsorption and reaction (SILAR), a facile method that yields uniform nanoporous films. After characterization of the phase, morphology, composition, and optical properties of the prepared films, the efficiencies of charge separation (ηsep) and water oxidation (ηox) in solar water splitting cells employing these photoanodes were estimated following a previously reported procedure. Unexpected wavelength and illumination direction dependencies were discovered in the derived efficiencies, casting doubt on the validity of the analysis. An alternative approach using a diffusion–reaction model that explicitly considers the efficiency of electron collection resolved the discrepancies and explained the illumination direction dependence of the photocurrent. Electron diffusion lengths (Ln) of 0.45 μm and 0.55 μm were derived for pristine and cobalt phosphate (Co-Pi) modified BiVO4, respectively, which are much shorter than the film thickness of ~2.1 μm. The Co-Pi treatment also increased ηoxfrom 0.86 to ~1, which is the main reason for the overall performance enhancement caused by adding Co-Pi. These findings suggest that there is little scope for improving the performance of SILAR-deposited BiVO4 photoanodes by further catalyzing water oxidation, but enhanced performance is achievable if electron transport can be improved.
ISSN:	2589-9651 2589-9651
DOI:	10.1016/j.nanoms.2019.10.003