Porphyrinic MOF-derived rich N-doped porous carbon with highly active CoN4C single-atom sites for enhanced oxygen reduction reaction and Zn-air batteries performance

Development of high-performance single-atom catalysts (SACs) for oxygen reduction reaction (ORR) has received extensive attention. However, unsatisfactory loading and utilization of metal single-atom sites largely limit the catalytic efficiency. Herein, two dimensional (2D) nanoporous Co single-atom decorated nitrogen-doped carbon catalyst (NP-CoSANC) was prepared by the pyrolysis of urea-adsorbed Co-TPyP MOF precursor. The adsorbed urea was proven to effectively inhibit metal ion agglomeration and create flourishing pore structures simultaneously. Benefit from the high-density CoN4C single-atom sites and porous structure, NP-CoSANC presents superior ORR performance with high E1/2 of 0.86 V and low Tafel slope of 62.4 mV dec−1 in 0.1 M KOH solution, surpassing most of advanced transition metal ORR catalysts and even commercial 20% Pt/C. The density functional theory calculations reveal that defect-edge and N-rich doped CoN4C sites in NP-CoSANC endow it with a lower free energy barrier to direct 4e− ORR pathway compared to traditional center CoN4C model. As a proof of concept, homemade aqueous primary and flexible quasi-solid-state Zn-air battery exhibit high peak power density as well as charge/discharge stability. This work proposes a facile and effective approach for constructing high-performance SACs electrocatalysts and provides a rational guidance in next-generation energy storage and conversion devices.