Coordination Engineering of Defective Cobalt–Nitrogen–Carbon Electrocatalysts with Graphene Quantum Dots for Boosting Oxygen Reduction Reaction

Developing efficient and robust metal–nitrogen–carbon electrocatalysts for oxygen reduction reaction (ORR) is of great significance for the application of hydrogen–oxygen fuel cells and metal–air batteries. Herein, a coordination engineering strategy is developed to improve the ORR kinetics and stability of cobalt–nitrogen–carbon (Co–N–C) electrocatalysts by grafting the oxygen-rich graphene quantum dots (GQDs) onto the zeolite imidazole frameworks (ZIFs) precursors. The optimized oxygen-rich GQDs-functionalized Co–N–C (G-CoNOC) electrocatalyst demonstrates an increased mass activity, nearly two times higher than that of pristine defective Co–N–C electrocatalyst, and retains a stability of 90.0% after 200 h, even superior to the commercial Pt/C. Comprehensive investigations demonstrate that the GQDs coordination can not only decrease carbon defects of Co–N–C electrocatalysts, improving the electron transfer efficiency and resistance to the destructive free radicals from H₂O₂, but also optimize the electronic structure of atomic Co active site to achieve a desired adsorption energy of OOH⁻, leading to enhanced ORR kinetics and stability by promoting further H₂O₂ reduction, as confirmed by theoretical calculations and experimental results. Such a coordination engineering strategy provides a new perspective for the development of highly active noble-metal-free electrocatalysts for ORR.