Solid oxide electrolysis cell (SOEC) can perform CO2 electrolysis to produce CO feedstock. In this work, we show Sr2Fe1.5+xMo0.5O6-delta with exsolved Fe nanoparticles to enhance the activity to CO2 electrolysis. A single SOEC with a configuration of SF1.5+xM-SDC/LSCM/LSM-SDC shows a current density of 1.16 A cm(-2) at 1.8 V, which presents the CO production rate of 6.85 mL min(-1) cm(-2) and the current efficiency of up to 96.3% at 850 degrees C. We further demonstrate a stable electrolysis performance without obvious degradation being observed even after a long-time operation of 100 h. The exsolved metal-oxide interfaces function as three phase boundary which transports gas molecules, oxygen ions and electrons and therefore accommodate CO2 splitting in electrochemical process. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.