Optimization and Modulation Strategies of Zinc Oxide-based Photoanodes for Highly Efficient Photoelectrochemical Water Splitting

Using hydrogen as an energy source has gained broad interest because of its eco-friendly, renewable, high energy density, and sustainable nature. It is important to note that hydrogen generation by the photoelectrochemical water splitting (PEC-WS) system is demonstrated as an efficient pathway to address the future energy and environmental issues. Playing a critical role in a typical PEC-WS system, transitional metal oxides (such as ZnO, TiO2, SnO2, etc.) were usually applied as photoanodes in view of their excellent electron mobility, strong stability, and appropriate conduction band position, and so forth. In this review, various optimization and modulation strategies of photoanodes based on ZnO were comprehensively summarized, including morphology and architecture manipulation, crystallization kinetics modulation, doping engineering, other semiconductor coupling, cocatalyst loading, and piezoelectric/ferroelectric/pyroelectric effect integrating, metallic nanoparticle incorporation. Furthermore, the prospect and outlook of ZnO-based photoanodes and their optimization strategies were also presented. This review also affords a systematic roadmap for other metal oxide optimization and modulation strategies.