Scale‐Up of BiVO4 Photoanode for Water Splitting in a Photoelectrochemical Cell: Issues and Challenges

The monoclinic scheelite-type BiVO4 is recognized as one of the promising candidate materials for a photoanode because of its 9.1 % theoretical efficiency for half-cell solar-to-hydrogen conversion. Although significant research efforts have been devoted to improving the performance of the photoelectrochemical cell (PEC) of this material, they have mainly been in small anode areas with only a handful of studies on scaled-up sizes. Herein, a facile metal–organic decomposition synthesis method was used to produce scaled-up Mo-doped BiVO4 photoanodes. Multiple modifications were explored and incorporated to enhance the performance of the photoanode. A large-area (5 cm×5 cm) photoanode was successfully prepared with all modifications. The resulting photoanode gave rise to an initial photocurrent density of 2.2 mA cm−2 at 1.23 V versus reversible hydrogen electrode, under AM 1.5G illumination in a PEC, which remained at 79 % of this value after 1 h of operation. A deleterious effect of the increased anode surface area on the photocurrent density was observed, which we termed the “areal effect”. Understanding the reasons for the areal effect is indispensable for the development of large-scale PEC devices for water splitting.