Single Co Atoms Anchored in Porous N‑Doped Carbon for Efficient Zinc−Air Battery Cathodes

Exploration of cheap, efficient, and highly durable transition-metal-based electrocatalysts is critically important for the renewable energy chain, including both energy storage and energy conversion. Herein, we have developed cobalt (Co) single atoms anchored in porous nitrogen-doped carbon nanoflake arrays, synthesized from Co-MOF precursor and followed by removal of the unwanted Co clusters. The well-dispersed Co single atoms are attached to the carbon network through N–Co bonding, where there is extra porosity and active surface area created by the removal of the Co metal clusters. Interestingly, compared with those electrocatalysts containing excess Co nanoparticles, a single Co atom alone demonstrates a lower oxygen evolution reaction (OER) overpotential and much higher oxygen reduction reaction (ORR) saturation current, showing that the Co metal clusters are redundant in driving both OER and ORR. Given the bifunctional electrocatalytic activity and mechanical flexibility, the electrocatalyst assembled on carbon cloth is employed as the air cathode in a solid-state Zn–air battery, which presents good cycling stabilities (2500 min, 125 cycles) as well as a high open circuit potential (1.411 V).