Isolated Iodine Single Atoms Regulating the in-Plane Electronic Structure of G-C₃N₄ for Enhanced CO₂ Photoreduction

Carbon nitride (CN) is a promising metal-free photocatalyst for carbon dioxide (CO₂) reduction, yet it remains challenging due to its instability under irradiation in vapor environments and low electron-hole separation efficiency. Here, we demonstrate that the decoration of iodine (I) single atoms on ultrathin CN (IUCN) benefit the formation of C═O during vapor-engaged photocatalytic processes, reduces the adsorption capacity of OH species, and strengthens the tri-coordinated bridging nitrogen atoms (C─N═C) linkages, preventing the self-decomposition of IUCN. The formed C─I covalent bond at the IUCN surface provides a direct channel for photogenerated hole transfer, improving the separation of the in-plane electron-hole pairs. Furthermore, orbital hybridization between the N-2p orbitals of IUCN and the C-2p orbitals of CO₂ lowers the energy of antibonding orbitals in CO₂, enhancing its activation and subsequent transformation. The optimal IUCN photocatalyst achieved CO and CH₄ yields of 181.09 and 16.27 µmol g^-1 h^-1 under simulated solar light irradiation, respectively. The CO and CH₄ yields are 90.29 and 17.92 µmol g^-1 h^-1 under visible light irradiation, respectively. This study expands the synthetic approaches for nonmetal single-atom catalysts and offers insights into the relationship between the configuration of single atoms and the reaction pathways.