Mn-incorporated Co3O4 bifunctional electrocatalysts for zinc-air battery application: An experimental and DFT study

Manganese-incorporated Co3O4 catalysts were prepared via thermal pyrolysis of ZIF-67, and the effect of manganese incorporation and annealing temperature on their catalytic performances for oxygen reduction and evolution reactions (ORR, OER) were investigated. Notable crystalline distortion was induced by manganese insertion into Co3O4 lattice, resulting in smaller crystallite size, more abundant Co2+ and considerable oxygen vacancies. All these properties were regarded as the crucial origins for electrocatalytic activity elevation. The catalyst annealed at 450 °C (denoted as Mn/Co-450) exhibited the optimal catalytic activity with an ultra-low potential gap (0.83 V). Using Mn/Co-450 as an air cathode, the zinc-air battery delivered high power density (115.5 mW cm−2), competitive specific capacity (783.4 mAh g−1) and good cycling stability. The theoretical overpotentials of ORR and OER were respectively decreased by 0.18 V and 0.05 V by DFT calculation due to the weakened interaction between Co and OH group and the strengthened Co-OOH interaction.