Interfacial Engineering Enables Highly Efficient CO2/H2O Co-electrolysis for Syngas Production.

Electrochemical co-electrolysis of CO2 and H2O in solid oxide electrolysis cells (SOECs) provides a promising pathway toward carbon-neutral fuel production and renewable energy storage, yet its efficiency and selectivity remain constrained by the limited reactivity of conventional cathodes. Here, we develop a CeO2/Ni-YSZ interfacial engineering strategy for regulating the reaction behavior of Ni-YSZ electrodes during high-temperature CO2/H2O co-electrolysis. A conformal CeO2 interfacial layer introduced through a scalable impregnation method enables the tubular Ni-YSZ-supported SOEC to achieve a current density of 1.1 A·cm-2 with a Faradaic efficiency of 99.7% and stable operation over 100 h. Beyond the performance enhancement associated with CeO2 incorporation, spectroscopic analyses reveal that CeO2 modification induces interfacial electronic redistribution involving Ce and Ni species and modifies the local oxygen environment, with the CeO2 surface exhibiting a more oxygen-deficient state. Combined with density functional theory calculations, these results further indicate that oxygen-deficient CeO2 provides favorable sites for CO2 adsorption and activation. The enhanced CO2 adsorption and activation facilitate the chemical conversion of CO2 toward CO through an RWGS-mediated pathway involving hydrogen-containing intermediates generated from electrochemical H2O reduction, thereby contributing to the improved overall co-electrolysis performance. This work highlights the role of interfacial regulation in promoting CO formation and overall co-electrolysis performance, with broader implications for the development of efficient high-temperature electrochemical energy conversion technologies.