Nanoporous MoO3−x/BiVO4 photoanodes promoting charge separation for efficient photoelectrochemical water splitting

Owing to the relatively short hole diffusion length, severe charge recombination in the bulk of bismuth vanadate (BiVO4) is the key issue for photoelectrochemical water splitting. Herein, we design a nanoporous MoO3−x/BiVO4 heterojunction photoanode to promote charge separation. The efficient electron transport properties of oxygen deficient MoO3−x and the nanoporous structure are beneficial for charge separation, leading to a significantly enhanced PEC performance. The optimized MoO3−x/BiVO4 heterojunction photoanode exhibits a photocurrent density of 5.07 mA·cm−2 for Na2SO3 oxidation. By depositing FeOOH/NiOOH dual oxygen evolution cocatalysts to promote surface kinetics, a high photocurrent density of 4.81 mA·cm−2 can be achieved for PEC water splitting, exhibiting an excellent applied bias photon-to-current efficiency of 1.57%. Moreover, stable overall water splitting is achieved under consecutive light illumination for 10 h. We provide a proof of concept for the design of efficient BiVO4-based heterojunction photoanodes for stable PEC water splitting.