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

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 Cu^δ+, 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 V_RHE, 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.