Binary Metal Oxide-Based Photocathodes for Green Hydrogen Production via Water Photoelectrolysis: A Survey and Future Perspectives

Photoelectrocatalytic water splitting represents a promising pathway for transforming solar energy into green hydrogen, a clean and sustainable energy source. This approach relies on the synergy between photocatalysis and electrocatalysis to split water into oxygen and hydrogen under ambient conditions. Nevertheless, the development of this technology remains limited by the lack of efficient electrode materials, especially photocathodes. In this context, binary metal oxides stand out as attractive alternatives thanks to their superior chemical stability and lower cost compared to other metallic materials. This paper first presents the fundamental principles of water photoelectrolysis to offer a comprehensive understanding of the photoelectrocatalysis process. It then offers a synthesis of recent studies focusing on the use of binary metal oxides (including CuO, Cu2o, NiO, and Co3O4) as photocathodes for photoelectrocatalytic (PEC) water splitting. Finally, several strategies aimed at improving their performance are discussed, including structural modification of the materials, integration of co-catalysts, doping techniques, and the formation of heterojunctions, which are identified as promising research directions.