Suppressing photoinduced charge recombination at the BiVO||NiOOH junction by sandwiching an oxygen vacancy layer for efficient photoelectrochemical water oxidation.

Nickel oxyhydroxide (NiOOH) is regarded as one of the promising cocatalysts to enhance the catalytic performance of photoanodes but suffers from serious interfacial charge-carrier recombination at the photoanode||NiOOH interface. In this work, surface-engineered BiVO photoanodes are fabricated by sandwiching an oxygen vacancy (O) interlayer between BiVO and NiOOH. The surface O interlayer is introduced on BiVO by a chemical reduction treatment using a mild reducing agent, sodium hypophosphite. The induced O can alleviate the interfacial charge-carrier recombination at the BiVO4||NiOOH junction, resulting in efficient charge separation and transfer efficiencies, while an outer NiOOH layer is coated to prevent the O layer from degradation. As a result, the as-prepared NiOOH-P-BiVO photoanode exhibits a high photocurrent density of 3.2 mA cm at 1.23 V vs. RHE under the irradiation of 100 mW/cm AM 1.5G simulated sunlight, in comparison to those of bare BiVO, P-BiVO and NiOOH-BiVO photoanodes (1.1, 2.1 and 2.3 mA cm, respectively). In addition to the superior photoactivity, the 5-h amperometric measurements illustrate improved stability of the surface-engineered NiOOH-P-BiVO photoanode. Our work showcases the feasibility of combining cocatalysts with O, for improved photoactivity and stability of photoelectrodes.