Ternary MnO/CoMn alloy@N-doped graphitic composites derived from a bi-metallic pigment as bi-functional electrocatalysts

Abstract

Developing a highly efficient bifunctional electrocatalyst for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) remains significant for metal–air battery progress. Among all candidates, non-precious transition metal composite materials with the appropriate components and nanostructures are promising for the ORR and OER. Herein, a composite comprising a CoMn alloy coated with N-doped carbon and MnO is synthesized by a facile strategy involving the annealing of a Prussian blue analogue. The derived heterogeneous composite includes the benefits of a CoMn alloy, N-doped carbon and MnO, giving a low onset potential (0.91 V), positive half-wave potential (0.76 V) and large limiting current density (5.8 mA cm⁻²). The enhanced ORR activity can be attributed to the optimal surface electronic configuration of the alloy, which facilitates intermediate dissociation, in combination with heterojunctions, which favor charge transfer from the alloy and oxide. In addition, the electrocatalyst displays promising activity for the OER with an onset potential of 1.53 V and a low potential of 1.65 V at 10 mA cm⁻², highlighting its prospect as an efficient bifunctional electrocatalyst.