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

Abstract

Photocatalytic nitrogen reduction reaction (PNRR) holds immense promise for sustainable ammonia (NH3) synthesis. However, few photocatalysts can utilize NIR light that carries over 50% of the solar energy for NH3 production with high performance. Herein, a dual NIR-responsive S-scheme ZnCoSx/Fe3S4 heterojunction photocatalyst is designed with asymmetric adsorption sites and excellent PNRR performance. The heterojunction possesses a hollow-on-hollow superstructure: Fe3S4 nanocrystal-modified ZnCoSx nanocages as building blocks assemble into spindle-shaped particles with a spindle-like cavity. Both Fe3S4 and ZnCoSx 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 N2, favoring the polarization and activation of N2 molecules. In combination with the promoted mass transfer and active site exposure of hollow superstructure, a superior PNRR performance is achieved, with a high NH3 evolution rate of 2523.4 µmol g−1 h−1, 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.