Architecture of a Long-Wavelength Visible–Light–Driven N-Doped WO3/BiVO4 Heterojunction Structure for Highly Efficient Photoelectrochemical Water Splitting

A nitrogen-doped tungsten oxide/BiVO4 (N-WO3/BiVO4) heterojunction structure was obtained utilizing ammonium paratungstate as the nitrogen source and Bi(NO3)3·5H2O as the bismuth source, exhibiting promising photoelectrochemical (PEC) performances and effectively obtaining a long photoresponse range into the visible light region. Notably, the UV–vis diffuse reflectance spectra of N-WO3/BiVO4 (566 nm, 2.19 eV) exhibited a notable red shift of the absorption edge compared to that of WO3/BiVO4 (516 nm, 2.47 eV). The N-WO3/BiVO4 photoanode demonstrated an excellent photocurrent density of 0.78 mA cm–2 at 0.68 V vs Ag/AgCl, which surpassed those of the WO3/BiVO4 (0.20 mA cm–2), pure WO3 (0.25 mA cm–2), and pure BiVO4 (0.03 mA cm–2) photoelectrodes. The improvement of the PEC performances was primarily due to the synergy of N doping and the involved heterojunction structure, suggesting that N doping increased the Vis-light response and the heterojunction structure promoted charge separation to improve the lifetime of photoinduced carriers.