Surface Recombination Passivation of the BiVO₄ Photoanode by the Synergistic Effect of the Cobalt/Nickel Sulfide Cocatalyst

The photoelectrochemical (PEC) water splitting performance of BiVO4 is limited by its sluggish surface water oxidation kinetics, which could be addressed by surface modification with oxygen evolution catalysts (OECs) as cocatalysts. Here, an ultrathin layer of cobalt/nickel-based sulfide is successfully deposited on the pyramidal BiVO4 photoanode as a cocatalyst to improve its surface kinetics. An increased photocurrent density and negative shift of onset potential are achieved for this BiVO4/cocatalyst composite, with nearly 99% of surface hole injection yield. The kinetic data based on IMPS show that the presence of a cocatalyst brings about a great decrease in surface charge recombination rate from 150 to 22 s–1 at 0.8 V vs RHE, which reveals that the cobalt/nickel sulfide cocatalyst serves as a passivation layer to suppress recombination at surface states and consequently enhance surface water oxidation kinetics.