Conformal BiVO4/WO3 nanobowl array photoanode for efficient photoelectrochemical water splitting

As one of the most promising photoanode candidates for photoelectrochemical (PEC) water splitting, the photocurrent density of BiVO4 still needs to be further improved in order to meet the practical application. In this work, a highly-matched BiVO4/WO3 nanobowl (NB) photoanode was constructed to enhance charge separation at the interface of the junction. Upon further modification of the BiVO4/WO3NB surface by NiOOH/FeOOH as an oxygen evolution cocatalyst (OEC) layer, a high photocurrent density of 3.05 mA cm−2 at 1.23 V vs. RHE has been achieved, which is about 5-fold higher than pristine BiVO4 in neutral medium under AM 1.5 G illumination. 5 times higher IPCE at 450 nm is also achieved compared with the BiVO4 photoanode, leading to about 95% faradaic efficiency for both H2 and O2 gas production. Systematic studies attribute the significantly enhanced PEC performance to the smaller BiVO4 particle size (< 90 nm) than its hole diffusion length (~100 nm), the improved charge separation of BiVO4 by the single layer WO3 nanobowl array and the function of OEC layers. Such WO3NB possesses much smaller interface resistance with the substrate FTO glass and larger contact area with BiVO4 nanoparticles. This approach provides new insights to design and fabricate BiVO4-based heterojunction photoanode for higher PEC water splitting performance.