Se/S-Modulated SnSe–SnS Heterostructures toward High-Current-Density CO ₂ Electroreduction to Formate

Electrochemical CO 2 reduction to formic acid (HCOOH) represents an attractive route for simultaneously alleviating CO 2 emissions and producing value-added chemicals, for which Sn-based catalysts are particularly promising due to their inherent selectivity toward the *OCHO reaction pathway. Herein, we propose a synergistic non-metal Se/S co-doping strategy to regulate both the activity and selectivity of Sn catalysts. By independently tuning the Se:S ratio and the overall Sn:(SeS) composition, heterostructured SnSe-SnS catalysts with optimized surface chemistry and interfacial properties are successfully constructed. Comprehensive structural and electrochemical characterizations reveal that Se/S co-doping effectively increases the electrochemically active surface area, tailors surface reaction pathways, and suppresses the competing hydrogen evolution reaction. Consequently, the optimized SnSe-SnS catalyst delivers a high Faradaic efficiency for formic acid of 93.46% at -100 mA cm -2 , together with a remarkable formate partial current density of 243.15 mA cm -2 under alkaline conditions. This work highlights the effectiveness of synergistic non-metal co-doping in tuning Sn-based electrocatalysts and provides a viable strategy for developing efficient and selective CO 2 -to-formate conversion systems.