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Photocurrent of BiVO4 is limited by surface recombination, not surface catalysis

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Abstract

Bismuth vanadate is one of the most promising photoanode materials for photoelectrochemical water splitting. In order to achieve high photocurrents the surface of BiVO4 always has to be modified with water oxidation catalysts, such as cobalt phosphate (CoPi), FeOOH, or NiFeOx. While this has generally been attributed to the poor intrinsic catalytic activity of BiVO4, detailed insight into the fate of the photogenerated charge carriers at the surface is still lacking. We used intensity modulated photocurrent spectroscopy (IMPS) to investigate the surface carrier dynamics of bare and CoPi-modified spray-deposited BiVO4 films. Using a model developed by Peter et al., it was possible to distinguish the reaction rate constants for surface recombination and charge transfer to the electrolyte. We found that modification with CoPi reduced the surface recombination of BiVO4 with a factor of 10–20, without significantly influencing the charge transfer kinetics. Control experiments with RuOx, one of the best known OER electrocatalysts, did not affect surface recombination and led to an actual decrease of the photocurrent. These results show that the main role of the CoPi is to passivate the surface of BiVO4 and that, contrary to earlier assumptions, the photocurrent of BiVO4 is limited by surface recombination instead of charge transfer. The importance of surface recombination is well recognized for conventional semiconductors in the field of photovoltaics; these findings show that it may also play a crucial role in oxide-based semiconductors for photoelectrochemical energy conversion.

Graphical abstract: Photocurrent of BiVO4 is limited by surface recombination, not surface catalysis

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Publication details

The article was received on 24 Jan 2017, accepted on 09 Mar 2017 and first published on 09 Mar 2017


Article type: Edge Article
DOI: 10.1039/C7SC00363C
Citation: Chem. Sci., 2017, Advance Article
  • Open access: Creative Commons BY-NC license
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    Photocurrent of BiVO4 is limited by surface recombination, not surface catalysis

    C. Zachäus, F. F. Abdi, L. M. Peter and R. van de Krol, Chem. Sci., 2017, Advance Article , DOI: 10.1039/C7SC00363C

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