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

Tailoring the oxygen evolution cocatalyst (OEC)/BiVO 4 interfaces with a hole transfer layer (HTL) is expected to suppress the interfacial charge recombination, thus achieving highly efficient photoelectrochemical (PEC) water splitting. Herein, Co 3 O 4 nanoparticles are inserted between the NiOOH OEC and BiVO 4 as an HTL for the design of NiOOH/Co 3 O 4 /BiVO 4 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 BiVO 4, the p-type Co 3 O 4 nanoparticles form p–n junctions with BiVO 4, thus providing an extra driving force for the extraction of the photogenerated holes from BiVO 4 to the NiOOH OEC, which efficiently suppresses charge recombination at the BiVO 4 /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)/BiVO 4 photoanodes. This work may inspire the rational design of high-performance photoanodes for feasible solar energy conversion.