Solution combustion synthesis of LaMO3 (M = Fe, Co, Mn) perovskite nanoparticles and the measurement of their electrocatalytic properties for air cathode

In this work, nanoparticles of LaMO3 (M = Fe, Co, Mn) perovskite oxide catalysts were produced by facile solution combustion synthesis with glycine as the fuel and metal nitrates as the oxidizers. The electrocatalytic activities of the catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were evaluated using a three-electrode half-cell design and a full rechargeable Zn-air battery with a 6 M KOH electrolyte. Comprehensive study of combustion synthesis and characterization of synthesized products showed that LaFeO3 had been successfully prepared in a single step of combustion synthesis, while the synthesis of LaCoO3 and LaMnO3 required an extra calcination step. The effects of the glycine/nitrate ratio and the calcination temperature and duration on the particle size and crystallinity of the final products were evaluated. Electrochemical characterization showed that LaMnO3 exhibited the best catalytic activity for both ORR and OER during the initial discharge-charge cycles, especially for the ORR corresponding to the discharge of the Zn-air battery. The order of activity is as follows: LaMnO3 > LaCoO3 > LaFeO3 > CB (carbon black). However, cycling performance measurements showed that the LaMnO3 catalyzed air electrode degraded very quickly, whereas the LaCoO3 catalyzed electrode exhibited the best rechargeability and stability.