Rational Design of Ternary Composite Photoanode BiVO4/PW12/NiTsPc for Improved Photoelectrochemical Water Oxidation

Despite recent efforts to improve BiVO4 semiconductor photoanodes, the electron‐hole recombination in BiVO4 photoanodes is still a critical problem in efficient photoelectrochemical water oxidation. In this work, a dual modification of BiVO4 photoanodes is performed utilising the polyoxometalate compound H3PW12O40 (PW12), acting as electron shuttle (electron capture and transfer), and nickel (II) phthalocyanine tetrasulfonic acid (NiTsPc), acting as hole extractor (accelerating hole transport). As for the photoelectrochemical water oxidation, the BiVO4/PW12/NiTsPc photoanode displays a 5.4‐fold improvement in photocurrent density at 1.23 V (vs. RHE) as compared to the pristine BiVO4 photoanode, under illumination of simulated solar light. Furthermore, we demonstrate that the recombination of electron‐hole pairs could be remarkably suppressed in the dual modified BiVO4 photoanode, by means of the electrochemical impedance spectroscopy measurements together with hydrogen peroxide as the hole scavenger. Additionally, the energy band distributions among PW12, BiVO4, and NiTsPc allow the photoelectron to transfer from BiVO4 to PW12 and the hole from BiVO4 to NiTsPc, which is responsible for the improved photoactivity of BiVO4. This work provides a new insight into effectively improving BiVO4 photoanode by rational design of dual modification.