Rational design and performance parameter of direct Z-scheme heterojunction materials for efficient HER/OER photocatalytic water splitting

Despite proposing a direct way to convert solar energy into green hydrogen fuel, photocatalytic water splitting's practical use remains limited due to fundamental issues with capacity, robustness, and efficiency. The difficulties arise from the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), two multi-electron electrochemical reactions that, in real-world working conditions, need charge carriers that are photogenerated. Although significant advances have been made in the development of photocatalyst materials with better light absorption, band alignment, and co-catalyst integrability, overall system performances remain well below what is required for large-scale implementation. The multiplicative coupling of transport, electrochemical, and photophysical processes occurring over various time and length scales is the cause of this disparity. With a focus on the interaction of surface catalysis, charge creation, separation, and transport, we present a quantitative performance analysis and mechanistic framework for building photocatalysts for HER and OER in this study. By integrating knowledge from semiconductor physics, electrochemistry, and reaction engineering, we refer to materials system techniques—such as spectrum engineering, facet-specific co catalyst loading, hierarchy-based interfaces, and scalable reactor principles—that encourage advancement toward real-world solar hydrogen production.