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.