Unravelling Structural–Electronic Properties Correlation with Oxygen Evolution Reaction Activity of MnCo ₂ O ₄ and Its Performance in Aluminum–Air Batteries

A comprehensive understanding of parameters influencing the oxygen evolution reaction (OER) performance of electrocatalysts is crucial for energy applications, such as aluminum–air batteries (AABs). Herein, we investigated the effect of calcination temperature on the physicochemical and electrochemical properties of MnCo2O4 (MCO) electrocatalyst. Variation in the calcination temperature significantly impacts the crystallinity, morphology, particle size, electronic states, and surface characteristics, confirmed by various characterization techniques. Among the samples studied, MCO calcined at 700 °C (MCO-700) exhibited the best OER performance with only a 7 mV increase in overpotential after 2000 cyclic voltammetry cycles and stability over 20 h in chronoamperometry tests. Besides this, in oxygen reduction reaction (ORR) studies, MCO-700 delivered a half-wave potential of 0.72 V and sustained its activity after a 12 h stability test, indicating excellent stability. To assess high-current performance in AABs, a prolonged galvanostatic discharge at 160 mA/cm2 for ∼11.5 h was conducted and indicated a stable discharge voltage of 1.28 V and excellent rate capability, even under high current densities. This study highlights the critical role of calcination temperature optimization in simultaneously tuning the physical, chemical, and electrochemical properties of the MCO for high-performance AABs.