Electronic Coupling of Cobalt Nanoparticles to Nitrogen‐Doped Graphene for Oxygen Reduction and Evolution Reactions

The rational design of nonprecious‐metal electrocatalysts with activities comparable to or greater than that of platinum is extremely valuable to the development of high energy density metal–air batteries. Herein, the two‐step preparation of a highly active oxygen electrocatalyst based on ultrasmall cobalt nanoparticles stabilized in a nitrogen‐doped graphene matrix is reported. The catalyst performs as well as the commercial Pt/C catalyst in the oxygen reduction reaction, and better than the Pt/C catalyst in the oxygen evolution reaction. This particular electrocatalyst could significantly lower the overpotentials of oxygen electrochemical reactions in aqueous lithium–air batteries to attain a round‐trip efficiency of about 79.0 % at a current density of 0.1 mA cm −2 , thereby surpassing the performance of the commercial Pt/C catalyst. The good performance may be attributed to strong metal–support interactions, maximized by a high dispersion of ultrasmall cobalt nanocrystals in a nitrogen‐doped graphene matrix, which yields electrocatalytic properties greater than the sum of its parts.