Bismuth vanadate is a promising photoanode material, but recent reports on undoped BiVO_4 without sublayers and co-catalysts showed large variations in photocurrent generation. We addressed this issue by correlating photoelectrochemical performance with physical properties. We devised a novel anodic electrodeposition procedure with iodide added to the aqueous plating bath, which allowed us to prepare BiVO_4 photoanodes with virtually identical thicknesses but different morphologies, and we could control surface Bi content. Morphologies were quantified from SEM images as distributions of crystallite areas and aspect-ratio-normalised diameters, and their statistical moments were derived. We could obtain clear photocurrent generation trends only from bivariate data analysis. Our experimental evidence suggests that a combination of low Bi/V ratio, small aspect-ratio-normalised diameters, and crystallites sizes that were small enough to provide efficient charge separation yet sufficiently large to prevent mass transport limitations led to highest photoelectrochemical performance
