Engineering of the A-site deficiency in La0.4Sr0.6Co0.7Fe0.2Nb0.1O3-delta perovskites for enhanced elelctrocatalytic oxygen reduction reaction

The development of efficient non-noble metal electrocatalysts for the oxygen reduction reaction (ORR) can aid the commercialization of fuel cells and metal-air batteries. Here, we developed a series of La0.4Sr0.6Co0.7Fe0.2Nb0.1O3-delta (LSCFN) perovskites by engineering A-site deficiency to enhance their electrocat-alytic activity for ORR in alkaline solutions. We found that LSCFN-0.90 with the highest amount of vacant A -sites has a highly oxidative oxygen species (O22-/O-) and an appropriate Co oxidation state -is a much better ORR catalyst in alkaline solutions compared to those with less vacant A-sites. The enhanced ORR kinetics enabled their use as the cathode catalyst in aluminum-air batteries, which also revealed better electrochemical performances for the catalyst with the highest A-site deficiency. Overall, the results demonstrate that an appro-priate A-site cation deficiency in perovskites can enhance the ORR electrocatalytic activity.