High-Loading Co Single Atoms and Clusters Active Sites toward Enhanced Electrocatalysis of Oxygen Reduction Reaction for High-Performance Zn–Air Battery

The development of precious-metal alternative electrocatalysts for oxygen reduction reaction (ORR) is highly desired for a variety of fuel cells, and single atom catalysts (SACs) have been envisaged to be the promising choice. However, there remains challenges in the synthesis of high metal loading SACs (>5 wt.%), thus limiting their electrocatalytic performance. Herein, a facile self-sacrificing template strategy is developed for fabricating Co single atoms along with Co atomic clusters co-anchored on porous-rich nitrogen-doped graphene (Co SAs/AC@NG), which is implemented by the pyrolysis of dicyandiamide with the formation of layered g-C₃N₄ as sacrificed templates, providing rich anchoring sites to achieve high Co loading up to 14.0 wt.% in Co SAs/AC@NG. Experiments combined with density functional theory calculations reveal that the co-existence of Co single atoms and clusters with underlying nitrogen doped carbon in the optimized Co₄₀SAs/AC@NG synergistically contributes to the enhanced electrocatalysis for ORR, which outperforms the state-of-the-art Pt/C catalysts with presenting a high half-wave potential (E_1/2 = 0.890 V) and robust long-term stability. Moreover, the Co₄₀SAs/AC@NG presents excellent performance in Zn–air battery with a high-peak power density (221 mW cm⁻²) and strong cycling stability, demonstrating great potential for energy storage applications.