Understanding the Roles of NiOx in Enhancing the Photoelectrochemical Performance of BiVO4 Photoanodes for Solar Water Splitting

Solar water oxidation is considered as a promising method for efficient utilization of solar energy and bismuth vanadate (BiVO4 ) is a potential photoanode. Catalyst loading on BiVO4 is often used to tackle the limitations of charge recombination and sluggish kinetics. In this study, amorphous nickel oxide (NiOx ) is loaded onto Mo-doped BiVO4 by photochemical metal-organic deposition method. The resulting NiOx /Mo:BiVO4 photoanodes demonstrate a two-fold improvement in photocurrent density (2.44 mA cm-2 ) at 1.23 V versus reversible hydrogen electrode (RHE) compared with the uncatalyzed samples. After NiOx modification the charge-separation and charge-transfer efficiencies improve significantly across the entire potential range. It is further elucidated by open-circuit photovoltage (OCP), time-resolved-microwave conductivity (TRMC), and rapid-scan voltammetry (RSV) measurements that NiOx modification induces larger band bending and promotes efficient charge transfer on the surface of BiVO4 . This work provides insight into designing BiVO4 -catalyst assemblies by using a simple surface-modification route for efficient solar water oxidation.