Boosting Photoelectrochemical Water Oxidation with Cobalt Phosphide Nanosheets on Porous BiVO4

Modification of the semiconductor surface by cobalt-rich catalysts is an effective strategy to improve the photoelectrochemical (PEC) water oxidation kinetics and migration of photogenerated electron and hole. In this study, cobalt phosphide (CoP) nanosheet was integrated on the nanoporous bismuth vanadate (BiVO4) electrode by using the hydrothermal method. The introduction of CoP significantly improved the PEC performance of the photoanode, with a photocurrent up to 4.0 mA cm–2 at 1.23 V (versus RHE) under simulated 100 mW cm–2 irradiation, a 3-fold enhancement over that obtained by the bare BiVO4. The BiVO4+CoP photoanode exhibited an impressive early onset of water oxidation, with a more than 220 mV cathodic shift of the onset potential, superior to the typical Co3O4 and Co–Pi cocatalysts-modified BiVO4 photoanode. Systematic studies show that the improvement in PEC performance by CoP is mainly due to the restraint of surface charge recombination and increase in photovoltage.