Steering carbon dioxide electroreduction toward formic acid by Sn-induced Cu(0) stabilization and optimized *OCHO intermediate adsorption.

The electrochemical CO reduction reaction (eCORR) 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 Cu, while the role of the stable Cu in steering selectivity remains underexplored. The strategy of doping Sn into Cu by magnetron sputtering to stabilize Cu against electrochemical dissolution during long-term eCORR operation was proposed in this work. The results reveal that the Sn-stabilized Cu surface undergoes a significant electronic structure modification, which alters the CO 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 H and CO pathways. As a result, the optimized CuSn catalyst achieves 81% Faradaic efficiency and -23 mA·cm current density for HCOOH at -1.0 V, 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 eCORR.