Factors affecting bismuth vanadate photoelectrochemical performance

Bismuth vanadate has recently emerged as a promising photoanode material for solar water splitting applications. Reports on unmodified BiVO_4 showed large variations in photocurrent generation. We prepd. BiVO_4 photoanodes with different chem. surface compns. and morphologies by electrodeposition and spin coating. We devised an electrodeposition procedure with iodide added to the plating bath; this way, we could obtain BiVO_4 films with matching thicknesses and control surface Bi/V ratios. Morphologies were quantified from scanning microscopy image anal. Smaller crystallites were synthesized by spin coating. We correlated chem. surface compn. and morphol. to photocurrent densities and obsd. trends only from bivariate data. Best photoelectrochem. performance required low surface Bi/V ratios, short distances to crystallites' edges, and crystallite areas that were small enough to provide good elec. contact to the FTO underneath yet sufficiently large to prevent mass transport limitations.