Synergistic Coupling Derived Cobalt Oxide with Nitrogenated Holey Two-Dimensional Matrix as an Efficient Bifunctional Catalyst for Metal–Air Batteries

Developing cost-effective, efficient bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the heart of metal–air batteries as a renewable-energy technology. Herein, well-distributed nanopolyhedron (NP) Co 3 O 4 grown on iron (Fe) encapsulated in graphitic layers on a nitrogenated, porous two-dimensional (2D) structure, namely, a C 2 N matrix, (NP Co 3 O 4 /Fe@C 2 N), presents an outstanding bifunctional catalytic activity with a comparable overpotential and Tafel slope to those of benchmark Pt/C and IrO 2 . The rationally designed atomic configuration of Co 3 O 4 on the C 2 N matrix has a well-controlled NP morphology with a (111) plane, leading to bifunctional activities for the ORR and OER. Interestingly, the specific interaction between the NP Co 3 O 4 nanoparticles and the C 2 N matrix introduces synergistic coupling and changes the electronic configuration of Co atoms and the C 2 N framework. Benefiting from the synergistic coupling of Co 3 O 4 with the C 2 N matrix, the NP Co 3 O 4 /Fe@C 2 N electrocatalyst exhibits exceptionally high stability and an even lower charge–discharge overpotential gap of 0.85 V at 15 mA cm –2 than that of the Pt/C+IrO 2 catalyst (1.01 V) in Zn–air batteries. This work provides insights into the rational design of a metal oxide on a C 2 N matrix for bifunctional, low-cost electrochemical catalysts.