La_0.8Sr_0.2MnO₃ based perovskite with A-site deficiencies as high performance bifunctional electrocatalyst for oxygen reduction and evolution reaction in alkaline

In this work, the A-site cation deficient perovskites (La_0.8Sr_0.2)_1-xMnO₃(x=0, 0.02, 0.05)(LSM) and Fe doped perovskite (La_0.8Sr_0.2)_0.95Mn_0.5Fe_0.5O₃(LSMF) are prepared by sol-gel process assisted with chelating effect of citric acid. The structure, morphology and valence state of the prepared samples were characterized. Their catalytic activities toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated by rotating-disk electrode (RDE). As expected, appropriate introduce of A-site deficiency can enhance both ORR and OER activities. Among the A-site cation deficient perovskites studied, (La_0.8Sr_0.2)_0.95MnO₃ exhibited the highest ORR and OER activities and, hence, the best bifunctionality. After doping with Fe in the B-site, the (La_0.8Sr_0.2)_0.95Mn_0.5Fe_0.5O₃ perovskite exhibits even better electrochemical catalytic activity which is due to the increase of the concentration of oxygen vacancy as compared with (La_0.8Sr_0.2)_0.95MnO₃. Furthermore, (La_0.8Sr_0.2)_0.95Mn_0.5Fe_0.5O₃ showed superior durability than commercial 20wt% Pt/C catalyst. This work indicates that introduce of A-site deficiency and B-site Fe doping in perovskite oxides is an effective strategy to enhance ORR and OER activity for the applications in metal-air batteries.