Sluggish oxygen evolution kinetics are one of the key limitations of bismuth vanadate (BiVO 4 ) photoanodes for efficient photoelectrochemical (PEC) water splitting. To address this issue, we report a vanadium oxide (VO x ) with enriched oxygen vacancies conformally grown on BiVO 4 photoanodes by a simple photoassisted electrodeposition process. The optimized BiVO 4 /VO x photoanode exhibits a photocurrent density of 6.29 mA cm À 2 at 1.23 V versus the reversible hydrogen electrode under AM 1.5 G illumination, which is ca. 385 % as high as that of its pristine counterpart. A high charge-transfer efficiency of 96 % is achieved and stable PEC water splitting is realized, with a photocurrent retention rate of 88.3 % upon 40 h of testing. The excellent PEC performance is attributed to the presence of oxygen vacancies in VO x that forms undercoordinated sites, which strengthen the adsorption of water molecules onto the active sites and promote charge transfer during the oxygen evolution reaction. This work demonstrates the potential of vanadium-based catalysts for PEC water oxidation.

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.

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Sluggish oxygen evolution kinetics are one of the key limitations of bismuth vanadate (BiVO 4 ) photoanodes for efficient photoelectrochemical (PEC) water splitting. To address this issue, we report a vanadium oxide (VO x ) with enriched oxygen vacancies conformally grown on BiVO 4 photoanodes by a simple photoassisted electrodeposition process. The optimized BiVO 4 /VO x photoanode exhibits a photocurrent density of 6.29 mA cm À 2 at 1.23 V versus the reversible hydrogen electrode under AM 1.5 G illumination, which is ca. 385 % as high as that of its pristine counterpart. A high charge-transfer efficiency of 96 % is achieved and stable PEC water splitting is realized, with a photocurrent retention rate of 88.3 % upon 40 h of testing. The excellent PEC performance is attributed to the presence of oxygen vacancies in VO x that forms undercoordinated sites, which strengthen the adsorption of water molecules onto the active sites and promote charge transfer during the oxygen evolution reaction. This work demonstrates the potential of vanadium-based catalysts for PEC water oxidation.

No abstract