Tandem Electrocatalysis With Cu-Based Alloy Catalysts for Efficient Multi-Carbon Formation in Strongly Acidic Conditions.

Electrochemical CO reduction reaction (CORR) in acidic electrolyte enables high single-pass carbon efficiency (SPCE), while highly corrosive acidic electrolytes typically cause catalyst degradation. It is reported that the dealloying of Cu/Ag and Cu/Al alloys, as well as the increased C─C coupling energy barrier, are reasons that advances in neutral/alkaline electrolysis do not translate to acidic conditions. Detailed characterizations reveal the dynamic evolution of the alloy in acidic CORR, that is CuAg undergoes dealloying, re-deposition, and surface restructuration, ultimately forming the stable Ag/Cu interfacial structure. In situ Raman spectroscopy reveals the dynamic evolution of interfacial water structures on CuAg during acidic CORR and also indicates that the evolved interface structure enhances the proton activity for CORR. CuAg achieves a CO Faradaic efficiency (FE) of 93.1% with stable electrolysis of 45 h at 250 mA cm. Based on this stable, high CO-selective catalyst, a tandem electrode is designed by deploying it on the CuAl surface to act as a protective and CO overflow layer. The tandem configuration suppresses dealloying in CuAl and creates a localized alkaline environment, thereby promoting C─C coupling. This tandem electrode exhibits a multi-carbon FE of 81.2% at 648 mA cm, a SPCE of 70.4%, and stable electrolysis of 30 h.