Cu Doping Activates SnS2 Basal Planes for Efficient CO2 Electroreduction to Formate

The electrocatalytic CO2 reduction reaction (CO2RR) to formate represents a promising pathway for CO2 utilization. However, pristine SnS2 catalysts are limited by poor selectivity, short lifetimes, and sluggish reaction kinetics. These issues are primarily correlated with the inertness of their basal planes. Inspired by density functional theory (DFT) calculations, we rationally designed a catalyst to activate these basal planes. DFT analyses, including electron localization function (ELF) and crystal orbital Hamiltonian population (COHP), reveal that the Cu-S bond possesses greater strength than the Sn-S bond. This suggests that copper can substitute tin in the SnS2 lattice, disrupt its ordered basal plane structure, and generate abundant defective sites with optimal adsorption strength for the key *OCHO intermediate. Guided by this theoretical prediction, we synthesized a Cu-doped SnS2 (Cu-SnS2) nanoflower catalyst via a room-temperature stirring process involving a CuSO4 solution and presynthesized SnS2. Comprehensive characterizations confirmed the uniform incorporation of Cu with a +1 oxidation state and a significant increase in sulfur vacancy concentration. The catalyst achieves a formate Faradaic efficiency of over 90% across a wide potential window, delivers a high current density of ∼280 mA cm-2 at -1.11 V vs RHE, and demonstrates stable operation for 60 h at 100 mA cm-2. Mechanism studies indicate that the synergistic effect of Cu doping and sulfur vacancies regulates the electronic structure of SnS2, accelerates charge transfer, suppresses the competing hydrogen evolution reaction, and alleviates tin dissolution during electrolysis. This work provides a strategy for designing high-performance CO2RR electrocatalysts through basal plane activation.