Dual Near-Infrared-Response S-Scheme Heterojunction with Asymmetric Adsorption Sites for Enhanced Nitrogen Photoreduction.

Photocatalytic nitrogen reduction reaction (PNRR) holds immense promise for sustainable ammonia (NH) synthesis. However, few photocatalysts can utilize NIR light that carries over 50% of the solar energy for NH production with high performance. Herein, a dual NIR-responsive S-scheme ZnCoS/FeS heterojunction photocatalyst is designed with asymmetric adsorption sites and excellent PNRR performance. The heterojunction possesses a hollow-on-hollow superstructure: FeS nanocrystal-modified ZnCoS nanocages as building blocks assemble into spindle-shaped particles with a spindle-like cavity. Both FeS and ZnCoS are NIR active, allowing efficient utilization of full-spectrum light. Moreover, an S-scheme heterojunction is constructed that promotes charge separation. In addition, the Fe/Co dual-metal sites at the interface enable an asymmetric side-on adsorption mode of N, favoring the polarization and activation of N molecules. In combination with the promoted mass transfer and active site exposure of hollow superstructure, a superior PNRR performance is achieved, with a high NH evolution rate of 2523.4  µmol g h, an apparent quantum yield of 9.4% at 400 nm and 8% at 1000 nm, and a solar-to-chemical conversion efficiency of 0.32%. The work paves the way for the rational design of advanced heterojunction catalysts for PNRR.