Enhanced lanthanum-stabilized low crystallinity metal oxide electrocatalysts with superior activity for oxygen reactions

Abstract

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key electrochemical reactions for the development of rechargeable Zn-air batteries. However, due to the high cost of commercial noble metal-based catalysts and their limited bifunctionality, it is necessary the design of new electrocatalysts. In this study, stable electrocatalysts have been synthesized through a hydrothermal method and further low-temperature thermal treatment. The materials consist of La stabilized low crystallinity Mn and Co metal (hydro-)oxides. The electrocatalytic performance of these materials has been compared with counterparts calcined at higher temperatures. The findings demonstrate that materials synthesized at lower temperatures and with low crystallinity exhibit superior electrocatalytic activity for both ORR and OER. Moreover, the research highlights the favorable influence of the lanthanum cation, which enhances changes of surface morphology and oxidation states of other cations (Mn and Co). Additionally, the positive contribution of the carbon component to electrochemical activity and electrical conductivity has been elucidated. The best electrocatalyst was studied in a rechargeable Zn-air battery with a durability of up to 120 h. They exhibited better stability and performance than the commercial Pt/C + RuO2 catalyst currently used.