Enhancing the charge transfer and photoelectrochemical performance of the BiVO4/WO3 heterojunction via gradient surface/interface Co–Mo doping

Abstract

In the field of photoelectrocatalytic (PEC) water splitting research, BiVO₄/WO₃ photoanodes exhibit excellent performance in facilitating the separation and transport of photogenerated electron–hole pairs. However, further improving charge transfer efficiency at the heterojunction interface and optimizing the kinetics of water oxidation reactions remain critical challenges. In this study, a Co–BiVO₄–Mo/WO₃ photoanode was successfully constructed by selectively introducing Mo at the interface and doping Co on the surface of the BiVO₄/WO₃ heterojunction, enabling precise control over the spatially graded distribution of the two dopants. The resulting photoanode achieved a photocurrent density of 3.423 mA cm⁻² at 1.23 V vs. RHE, representing an approximately 1.6 times enhancement compared to the unmodified BiVO₄/WO₃ heterojunction (2.157 mA cm⁻²), 2.3 times higher than pristine BiVO₄ (1.508 mA cm⁻²), and a nearly 3.8 times improvement over pristine WO₃ (0.916 mA cm⁻²). The results demonstrate that the reversible interconversion between Mo⁴⁺ and Mo⁶⁺ at the heterojunction interface effectively promotes interfacial charge transfer. Meanwhile, the formed CoOOH on the photoanode surface significantly enhances surface reaction kinetics and improves photoanode stability. The gradient co-doping of Co and Mo at the interface and surface effectively enhances interfacial charge transfer kinetics and significantly improves structural stability. This well-designed gradient doping strategy provides a viable technical pathway for the rational design and controllable fabrication of high-performance PEC photoanodes for water oxidation.