Highly efficient nitrogen fixation over S-scheme heterojunction photocatalysts with enhanced active hydrogen supply.

Photocatalytic N fixation is a promising strategy for ammonia (NH) synthesis; however, it suffers from relatively low ammonia yield due to the difficulty in the design of photocatalysts with both high charge transfer efficiency and desirable N adsorption/activation capability. Herein, an S-scheme CoS/ZnS heterojunction with dual active sites is designed as an efficient N fixation photocatalyst. The CoS/ZnS heterojunction exhibits a unique pocket-like nanostructure with small ZnS nanocrystals adhered on a single-hole CoS hollow dodecahedron. Within the heterojunction, the electronic interaction between ZnS and CoS creates electron-deficient Zn sites with enhanced N chemisorption and electron-sufficient Co sites with active hydrogen supply for N hydrogenation, cooperatively reducing the energy barrier for N activation. In combination with the promoted photogenerated electron-hole separation of the S-scheme heterojunction and facilitated mass transfer by the pocket-like nanostructure, an excellent N fixation performance with a high NH yield of 1175.37 μmol g h is achieved. This study provides new insights into the design of heterojunction photocatalysts for N fixation.