Factors affecting bismuth vanadate photoelectrochemical performance

Abstract

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.

Recent Advances in the BiVO4 Photocatalyst for Sun-Driven Water Oxidation: Top-Performing Photoanodes and Scale-Up Challenges

“…BiVO 4 is known to suffer from poor electron mobility, and photon efficiency is therefore lost relatively easily to electron-hole recombination [33,34]. This phenomenon is reportedly due to the fact that the VO 4 tetrahedra are not connected to each other [35], thus making it hard for photogenerated electrons to flow towards the conducting support.…”

Textured nanoporous Mo:BiVO4 photoanodes with high charge transport and charge transfer quantum efficiencies for oxygen evolution

“…Our results agree with previous reports that conclude on the basis of XPS data that the BVO surface tends to be significantly vanadium deficient. 24,51,55,77,78 Table 2). The XPS and EDS data are consistent with a bismuthrich, vanadium-deficient surface layer on otherwise stoichiometric BVO grains.…”

Mixed‐Metal Tungsten Oxide Photoanode Materials Made by Pulsed‐Laser in Liquids Synthesis

“…The performance of photoelectrodes is not just governed by sunlight absorption, but band edge positions of the material in contact with the liquid electrolyte, material conductivity, carrier lifetimes, and charge recombination processes also matter; structure size critically affects the probability of a photogenerated carrier to reach the photoelectrode-electrolyte interface. [9,16] Since photocurrent generation of complex semiconductors depends on many factors, [46] simple correlations are rarely found, especially when comparing different materials as in this work. Table 1 for nomenclature.…”

“…[46] The incident photon flux was equivalent to 1 sun illumination, as verified by a calibrated Si photodiode (Thorlabs). We used three electrodes per material and observed good reproducibility.…”

“…Photoanodes were prepared by modifying a procedure reported elsewhere. [46] We used FTO-glass substrates purchased from Hartford Glass Co. (TEC 15, surface resistivity ~15 Ω/sq). FTO-glass slides were cut into ~ 1.0 cm × 2.5 cm pieces and (i) rinsed with water and patted dry with a Kimwipe, (ii) rinsed with a 1/1 (v/v) mixture of acetone and methanol (both EMD, HPLC grade) and patted dry with a Kimwipe, (iii) surface-etched by submerging for 3 seconds in concentrated hydrochloric acid (Macron), rinsed with water, and patted dry with a Kimwipe.…”