"Template-assisted synthesis" strategy to improve the bifunctional catalytic activity of oxygen electrode for reversible protonic ceramic electrochemical cell

Reversible protonic ceramic electrochemical cell (R-PCEC) is a new energy conversion device that can achieve efficient conversion between chemical energy and electrical energy. However, the oxygen electrode has poor activity towards oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which hinders the largescale application of R-PCEC. Therefore, in order to improve the catalytic activity of oxygen electrodes, La0.5Sr0.5Co0.2Fe0.8O3 (LSCF) is prepared using mesoporous silica SiO2 (SBA-15) and polymethyl methacrylate (PMMA) as templates, and it was combined with BaZr0.1Ce0.7Y0.2O3-delta (BZCY) to form a composite oxygen electrode for R-PCEC. Compared to the LSCF with solid-state reaction method, LSCF with hard-template method shows higher specific surface area and more oxygen vacancy, resulting in excellent ORR catalytic activity. In addition, LSCF prepared using PMMA as a template exhibits the best ORR catalytic activity, and the single cell with this composite oxygen electrode shows the highest maximum power density of 406 mW cm-2 in fuel cell (FC) mode with wet H2 (3%H2O) and air as the fuel and oxidant, respectively. Additionally, it demonstrates a current density of -973 mA cm- 2 at 1.3 V in electrolysis cell (EC) mode with wet air (10%H2O) as the oxidant. The single cell also shows good reversibility in FC mode and EC mode. This work provides a new strategy to improve the bifunctional activity of oxygen electrode in R-PCEC.