Controlling the Chemical Bonding of Highly Dispersed Co Atoms Anchored on an Ultrathin g-CN@Carbon Sphere for Enhanced Electrocatalytic Activity of the Oxygen Evolution Reaction.

Controlling the chemical bonding of an active atom and carbon support is an effective strategy for enhancing the electrocatalytic activity of a metal-nitrogen/carbon catalyst. Herein, highly dispersed Co atoms are successfully prepared by using an ultrathin g-CN@carbon sphere as the support, and subsequently the well-defined Co-N and Co-O bonds on the atomic level are controllably constructed by adjusting the calcination atmosphere. Results show that highly dispersed Co with Co-O and Co-N bonds exhibits excellent oxygen evolution reaction performance in alkaline media at low and high overpotentials, respectively, and outperform most single-atom catalysts reported to date. DFT calculation, coupled with high-angle annular dark-field scanning transmission electron microscopy and X-ray photoelectron spectrometry techniques, reveals that the high activities mainly originate from the precise O-Co-N and N-Co-N coordination in the ultrathin g-CN@carbon sphere support. The enhancement mechanism of chemical bonding provides guidance for the atomic exploration and design of electrocatalysts.