Stable, active CO(2) reduction to formate via redox-modulated stabilization of active sites

Electrochemical reduction of CO(2) (CO(2)R) to formic acid upgrades waste CO(2); however, up to now, chemical and structural changes to the electrocatalyst have often led to the deterioration of performance over time. Here, we find that alloying p-block elements with differing electronegativities modulates the redox potential of active sites and stabilizes them throughout extended CO(2)R operation. Active Sn-Bi/SnO(2) surfaces formed in situ on homogeneously alloyed Bi(0.1)Sn crystals stabilize the CO(2)R-to-formate pathway over 2400 h (100 days) of continuous operation at a current density of 100 mA cm(−2). This performance is accompanied by a Faradaic efficiency of 95% and an overpotential of ~ −0.65 V. Operating experimental studies as well as computational investigations show that the stabilized active sites offer near-optimal binding energy to the key formate intermediate *OCHO. Using a cation-exchange membrane electrode assembly device, we demonstrate the stable production of concentrated HCOO(–) solution (3.4 molar, 15 wt%) over 100 h.