Nitrogen-Doped Graphitic Carbon-Supported Ultrafine Co Nanoparticles as an Efficient Multifunctional Electrocatalyst for HER and Rechargeable Zn-Air Batteries.

The construction of high-efficiency electrocatalysts for hydrogen evolution, oxygen reduction, and oxygen evolution reactions (HER/ORR/OER) is critical for the overall water splitting system, fuel cells, and rechargeable metal-air batteries. Here, we report a viable strategy for tuning the size of a Co-based zeolitic imidazolate framework (ZIF). As a result, a nitrogen-doped graphitic carbon-supported ultrafine Co nanoparticle electrocatalyst (Co/NGC-3) with multifunctional activity was developed. Owing to the smaller ZIF-67 polyhedrons with relatively uniform distribution, more effective active sites, and a strong coupling effect of Co-pyridinic-N, the proposed Co/NGC-3 catalyst exhibited an impressive HER activity. It also showed brilliant catalytic activity in both the ORR and OER, delivering a more positive half-wave potential and a lower overpotential than that of the Pt/C catalyst, respectively. Moreover, the Co/NGC-3 involved the Zn-air battery displayed satisfactory power density, excellent energy density, and superior stability. This approach provides an efficient strategy for the preparation of high-performance multifunctional electrocatalysts for energy-related applications.