Cu Infiltration-Driven Metal–Oxide Heterostructure Construction for Enhanced CO₂ Electrolysis via Coupled Ion–Electron Migration in SFM-GDC Cathodes

Solid oxide electrolytic cells (SOECs) show considerable potential for efficient CO2 conversion; however, the catalytic performance and durability of cathode materials remain critical challenges. In this study, a series of Cu-decorated composite cathodes (Cu@SFMGDC) with varying Cu loadings were fabricated via a simple wet infiltration method for direct CO2 electrolysis in SOECs. The electrocatalytic performance and long-term stability of the cathodes were systematically evaluated. The formation of a metal-oxide heterostructure between active Cu nanoparticles and the SFMGDC scaffold significantly enhanced CO2 chemisorption and activation by introducing abundant reaction sites for the CO2 reduction reaction (CO2RR) during CO2 electrolysis. The introduction of Cu significantly enhanced electronic conductivity and promoted cotransport dynamics of electrons and oxygen ions across the heterointerface, thereby optimizing interfacial charge-transfer kinetics. This synergistic effect yielded exceptional electrochemical performance in the 2 wt % Cu@SFMGDC cathode, achieving a current density of 2.929 A cm-2 at 1.6 V and 850 °C─a 1.58-fold enhancement over the unmodified SFMGDC cathode (1.846 A cm-2). The optimized electrode further exhibited sustained operational stability over 100 h and exceptional carbon deposition resistance under high-temperature CO2 electrolysis conditions. These results provide critical insights into the role of Cu-mediated heterointerfaces in advancing high-efficiency, durable cathodes for solid oxide electrolysis cells, with direct implications for scalable CO2-to-fuel conversion technologies.