Regulation of oxygen vacancies and electronic structures by substituting Ba2+ at A-sites of LaNi0.5Mn0.5O3 double perovskites enabling high-performance catalysts for Mg-air batteries

Abstract

The air cathodes impact the electrochemical performance of primary Mg-air batteries greatly, in which the activity of catalysts plays a decisive role. Perovskites attract significant attention for their high oxygen reduction reaction (ORR) catalytic activity, unique structure, simple synthesis, and low cost. Herein, a series of La1-xBaxNi0.5Mn0.5O3 (x = 0.1, 0.2, 0.3, 0.4, 0.5) catalysts fabricated by substituting Ba2+ for La3+ at the A-sites of LaNi0.5Mn0.5O3 are reported. As a result, the catalytic performance toward ORR exhibits a volcano curve with the increase of doping amount and the highest catalytic activity was achieved at 30 % of Ba2+ content. Importantly, the experimental and computational results explain the enhancement by the large O2 adsorption capacity, the formation of oxygen vacancies, the increase in the content of Mn3+ as an adsorption active site, and the upshift of the Mn-3d band center toward the Fermi level, thereby facilitating the O2 adsorption and reducing the energy barrier of the rate determining step of ORR. The Mg-air battery with the La0.7Ba0.3Ni0.5Mn0.5O3 catalyst displays a high discharge voltage of 1.37 V and a maximum power density of 65.224 mW·cm-2. Therefore, this new ORR catalyst presents great potential in practical Mg-air batteries.