Intrinsically Conductive Perovskite Oxides with Enhanced Stability and Electrocatalytic Activity for Oxygen Reduction Reactions

The oxygen reduction reaction (ORR) is traditionally catalyzed by carbon-supported precious metals, heteroatom-doped carbons, and transition-metal-carbon hybrids. Despite their good electric conductivity and high catalytic activities, these carbon-containing catalysts suffer from electrochemical carbon corrosion which limits their utility in metal-air batteries and fuel cells. Here, we report a class of perovskite La_0.5Sr_0.5Mn_1-xNi_xO_3-δ nanocrystals that are intrinsically conductive with good electrocatalytic activity for the ORR. Among these perovskites, La_0.5Sr_0.5Mn_0.9Ni_0.1O_3-δ (δ = 0.06, LSMN) exhibited the highest electrocatalytic activity for ORR with an onset potential of 1.02 V, a half-wave potential of 0.80 V, and a Tafel slope of -68 mV decade^-1 in 0.1 M potassium hydroxide aqueous solution. Negligible degradation of oxygen reduction currents was observed after 300 cyclic voltammetry scans from 1.08 to 0.15 V. We demonstrated that the electrically conductive perovskites with transition-metal redox couples and oxygen vacancies are essential. Our work demonstrates the possibility of carbon-free oxygen electrocatalysis with widely promising applications.