Steering carbon dioxide electroreduction toward formic acid by Sn-induced Cu0 stabilization and optimized *OCHO intermediate adsorption.

The electrochemical CO2 reduction reaction (eCO2RR) to HCOOH presents a sustainable route for carbon utilization, but faces low selectivity and poor stability on copper-based catalysts. The common strategy is modulating Cuδ+, while the role of the stable Cu0 in steering selectivity remains underexplored. The strategy of doping Sn into Cu by magnetron sputtering to stabilize Cu0 against electrochemical dissolution during long-term eCO2RR operation was proposed in this work. The results reveal that the Sn-stabilized Cu0 surface undergoes a significant electronic structure modification, which alters the CO2 adsorption configuration and preferentially strengthens the key intermediate *OCHO adsorption over *COOH. The tailored adsorption landscape lowers the kinetic barrier for the HCOOH pathway while suppressing competitive H2 and CO pathways. As a result, the optimized Cu50Sn20 catalyst achieves 81% Faradaic efficiency and -23 mA·cm-2 current density for HCOOH at -1.0 VRHE, with negligible degradation over 40 h continuous operation. This work highlights the importance of stabilizing metallic states and provides a novel doping strategy to design durable and selective copper-based catalysts for value-specific eCO2RR.