Engineering BiVO4 and Oxygen Evolution Cocatalyst Interfaces with Rapid Hole Extraction for Photoelectrochemical Water Splitting

Tailoring the oxygen evolution cocatalyst (OEC)/BiVO4 interfaces with a hole transfer layer (HTL) is expected to suppress the interfacial charge recombination, thus achieving highly efficient photoelectrochemical (PEC) water splitting. Herein, Co3O4 nanoparticles are inserted between the NiOOH OEC and BiVO4 as an HTL for the design of NiOOH/Co3O4/BiVO4 photoanodes. A champion photoanode achieves a photocurrent density of 6.4 mA cm–2 at 1.23 V versus the reversible hydrogen electrode (RHE) under AM 1.5 G illumination (100 mW cm–2). Stable PEC water splitting is realized for up to 90 h. Being highly dispersed at the surfaces of BiVO4, the p-type Co3O4 nanoparticles form p–n junctions with BiVO4, thus providing an extra driving force for the extraction of the photogenerated holes from BiVO4 to the NiOOH OEC, which efficiently suppresses charge recombination at the BiVO4/NiOOH interfaces and accelerates the surface water oxidation kinetics. A charge separation efficiency of 95.6% and a surface charge transfer efficiency of 97.7% are achieved at 1.23 V vs RHE. The strategy is applicable to other OEC (e.g., MnO x and FeOOH)/BiVO4 photoanodes. This work may inspire the rational design of high-performance photoanodes for feasible solar energy conversion.