Photocatalytic water splitting via two-electron pathway offers a more fascinating and kinetically favorable way to produce H₂ compared with traditional four-electron pathway. The review highlights the mechanism and advancements of photocatalytic H₂ production via a two-electron pathway. Additionally, it addresses the challenges and opportunities for the commercial application of photocatalytic water splitting via the two-electron pathway.

Abstract

In response to energy and environmental crises, solar-driven pure water splitting is a promising way to produce and store renewable energy sources without environmental pollution. Photocatalytic water splitting via two-electron pathway (2H₂O→H₂+H₂O₂) is a more kinetically favorable way to produce H₂ compared with traditional four-electron pathway. Although numerous efforts have been devoted to investigate the application of two-electron pathway water splitting, drawbacks still inhibit the efficiency of H₂ generation. This review discusses the mechanism and challenges of photocatalytic water splitting via a two-electron pathway. Then, recent developments in novel photocatalyst preparation and modification strategies for effective H₂ generation via two-electron pathway were discussed, such as morphology and structure modulation, elemental doping, co-catalyst loading, and heterostructure construction. In addition, the development of stepwise two-electron pathway which further decomposed H₂O₂ and release O₂ was also introduced. Appropriate co-catalyst with high H₂O₂ decomposition activity that is essential for stepwise process was discussed. Finally, challenges and opportunities for commercial application of photocatalytic water splitting via two-electron pathway were briefly outlined.