Suitable photocatalysts and photoelectrodes for H₂ generation via water splitting: A comprehensive review

The rapidly increasing global energy demand and environmental concerns have created an urgent need for clean and sustainable energy sources. Hydrogen (H₂), a clean fuel, offers a promising alternative to fossil fuels. Solar-driven water splitting using photocatalysts and photoelectrodes is among the most effective approaches for sustainable H₂ production. This review outlines the fundamental principles of water splitting, emphasizing the roles of bandgap energy, band edge positions, and other key factors influencing H₂ generation. Recent progress in photocatalysts, photoanodes, and photocathodes is summarized, with particular focus on material design, surface modification, and heterojunction construction. Various material classes- including metal oxides, sulfides, nitrides, and two-dimensional (2D) semiconductors- are compared to identify efficient visible-light systems. Despite significant progress, challenges such as low efficiency, poor stability, and high cost still persist. Emerging strategies, including nanostructuring, co-catalyst loading, and interface engineering, are discussed as potential pathways toward scalable and stable solar hydrogen production.