Enriched Sp2-Hybridized C Atoms Toward the Tradeoff Between Activity, Conductivity and Stability of Spherical Porous Metal–Nitrogen–Carbon Catalysts for Rechargeable Zinc–Air Batteries

Advances in high-performance transition-metal- nitrogen-carbon catalysts (M-N-Cs) for the oxygen reduction reactions (ORR) are high-profile efforts to realize the large-scale implementations of rechargeable zinc-air batteries. However, it is extremely desirable but challenging to achieve stable active sites and excellent electron transport capability for M-N-C catalysts. Herein, spherical porous M-N-Cs (denoted as NPCS-Fc) with tailoring of the sp(2)-C/sp(3)-C ratio in carbon shell were prepared from low-cost coal tar pitch (CTP) via an acid-treatment-introduced defect-assisted one-step pyrolysis strategy. Due to the tradeoff among activity, conductivity, and stability, NPCS-Fc exhibits excellent ORR performance with a half-wave potential (E-1/2) of 0.863 V, a low Tafel slope of 59 mV dec(-1), and long-cycle durability in alkaline media. As the air cathode, the assembled rechargeable zinc-air battery delivers a high OCV of 1.538 V and a specific capacity of 870 mAh gzn(-1). The enriched sp(2)-C atom strategy to give M-N-C materials opens up a facile way for developing high-performance catalysts in flexible, rechargeable zinc-air batteries.