Interface Engineering Triggered Electron Transfer Channels and Enhanced p–p Orbital Coupling: Boosting CO2 Electroreduction to Formate Over Heterostructured CuS@SnO2

Tin dioxide (SnO 2 ) has been demonstrated to convert CO 2 to formate in an electrocatalytic CO 2 reduction reaction (eCO 2 RR). However, suboptimal CO 2 activation and insufficient electrical conductivity pose formidable challenges to achieving desirable eCO 2 RR activity. Herein, a heterostructured CuS@SnO 2 catalyst was designed to realize efficient formate production in eCO 2 RR, which delivers a Faraday efficiency (FE) of 94.9% and partial current density of 243.5 mA cm −2 at −1.1 V versus RHE in alkaline conditions, coupled with excellent electrochemical stability. Systematic investigations reveal that CuS acts as an electron reservoir, and the directional electron transfer channels induce interfacial electron deficiency in SnO 2 , stabilizing Sn active sites during long-term eCO 2 RR operation. Furthermore, it confers dual effects for promoting formate conversion at the molecular level, which integrates optimized interface electronic structure and enhanced p–p orbital coupling between the key * OCHO intermediate and SnO 2 interface, rendering the enhanced * OCHO adsorption, decreased CO 2 hydrogenation energy barrier, and improved intrinsic formate activity. Beyond catalytic performance, CuS@SnO 2 was further utilized in a Li-CO 2 battery to enable integrated CO 2 conversion and energy storage functionality. This study provides a strategy to effectively regulate the formate selectivity of eCO 2 RR by heterointerface engineering, and meanwhile bridges rational catalyst design with practical CO 2 conversion technologies.