Systematic engineering of BiVO₄ photoanode for efficient photoelectrochemical water oxidation

BiVO4 is one of the most promising photoanode materials for photoelectrochemical (PEC) solar energy conversion, but it still suffers from poor photocurrent density due to insufficient light-harvesting efficiency (LHE), weak photogenerated charge separation efficiency (f(Sep)), and low water oxidation efficiency (f(OX)). Herein, we tackle these challenges of the BiVO4 photoanodes using systematic engineering, including catalysis engineering, bandgap engineering, and morphology engineering. In particular, we deposit a NiCoOx layer onto the BiVO4 photoanode as the oxygen evolution catalyst to enhance the f(OX) of Fe-g-C3N4/BiVO4 for PEC water oxidation, and incorporate Fe-doped graphite-phase C3N4 (Fe-g-C3N4) into the BiVO4 photoanode to optimize the bandgap and surface areas to subsequently expand the light absorption range of the photoanode from 530 to 690 nm, increase the LHE and f(Sep), and further improve the oxygen evolution reaction activity of the NiCoOx catalytic layer. Consequently, the maximum photocurrent density of the as-prepared NiCoOx/Fe-g-C3N4/BiVO4 is remarkably boosted from 4.6 to 7.4 mA cm-2. This work suggests that the proposed systematic engineering strategy is exceptionally promising for improving LHE, f(Sep), and f(OX) of BiVO4-based photoanodes, which will substantially benefit the design, preparation, and large-scale application of next-generation high-performance photoanodes.