Oxygen-Rich Cobalt-Nitrogen-Carbon Porous Nanosheets for Bifunctional Oxygen Electrocatalysis

Metal-nitrogen-carbon (M-N-C) materials have attracted much interest in bifunctional oxygen-involving electrocatalysis for rechargeable Zn-air batteries. Such M-N-C electrocatalysts with M-N-x sites show good activity for the oxygen reduction reaction (ORR) but moderate activity for the oxygen evolution reaction (OER). Herein, an oxygen-rich M-N-C material (O-Co-N/C) with a highly porous nanosheet structure is reported as a bifunctional oxygen electrocatalyst, which is prepared by the direct pyrolysis of ultrathin CoO nanosheets decorated with zeolitic imidazolate framework-8 nanoparticles under an inert atmosphere. Particularly, Co nanoparticles in the O-Co-N/C electrocatalyst contain both Co-N-x and Co-O-x coordination environments to provide intrinsic active sites for the ORR and OER, respectively. Furthermore, electrochemical studies show that the O-Co-N/C catalyst retains comparable ORR activity to common M-N-C materials with a half-wave potential of 0.85 V vs the reversible hydrogen electrode and better OER activity with an overpotential of 0.29 V at the current density of 10 mA cm(-2). This study provides insights into the development of effective oxygen-involving electrocatalysts with bifunctional metal active centers coordinated by both nitrogen and oxygen atoms.