Promotion of Ca3Co4O9+δ oxygen electrode by in-situ exsolution of nanoparticles for solid oxide cells

Exsolution of active nanoparticles in oxide materials is an effective and feasible way to promote the catalytic activities of electrodes for solid oxide cells (SOCs). In this study, Ca-site deficient CaxCo4O9+δ (CCO-x, x = 1.5, 2, 2.5) materials are facilely prepared and studied as oxygen electrodes of SOCs. Co3O4 nanoparticles are in-situ exsolved and well embedded on the Ca3Co4O9+δ (CCO-3.0) surface by high-temperature annealing at 850 °C in ambient air. Results proves an effectively promotion of the ORR and OER kinetics with Ca deficiency. The polarization resistance of CCO-1.5 oxygen electrode reduces by 60% as compared with that of the CCO-3.0 electrode at 800 °C, from 0.23 to 0.09 Ω cm2. Both the peak power density and the electrolysis current density of the anode-supported SOC with CCO-1.5 oxygen electrode are more than 2 times that of the CCO-3.0 cell. The improved electrochemical kinetics is attributed to the exsolved Co3O4 nanoparticles with high redox reactivity and the enhanced oxygen vacancy concentration. Results make clear reliability of Ca-site deficient CaxCo4O9+δ as a promisingly oxygen electrodes for SOCs.