The optimization of LaMn2O5@GO by precursor solution pH for the oxygen reduction reaction in zinc-air batteries

At present, precious metal Pt-based catalysts are still the most widely used commercially efficient oxygen reduction reaction (ORR) catalysts. However, due to factors such as scarcity of earth content, high cost, and poor durability, they cannot be used on a large scale in industry. In this paper, Mn-based mullite-type oxides LaMn₂O₅ flake nanocrystals with large specific surface area were prepared as an effective substitute for noble metal-based catalysts by regulating the hydrothermal conditions, and introducing an appropriate amount of graphene oxide (GO) as the C source significantly improved the conductivity of the catalyst. Adjusting the pH range of the precursor solution changes the OH⁻ ion concentration in the hydrothermal environment, destroys the oxygen-containing group species in LaMn₂O₅@GO and promotes O₂ adsorption during ORR, resulting in a half-wave potential of 0.82 V (vs. RHE). The corresponding catalyst was used to assemble a zinc-air battery, achieving a higher open circuit voltage (1.57 V) and power density (160 mW cm⁻²) and demonstrating excellent cyclic stability with a reduction in overpotential of only 30 mV after 450 h of long-term charge-discharge measurement. This work represents a general method to improve the catalytic activity of Mn-based mullite-type oxides for zinc-air battery applications.