Single atom iron implanted polydopamine-modified hollow leaf-like N-doped carbon catalyst for improving oxygen reduction reaction and zinc-air batteries.

Metal-nitrogen-carbon (MNC) catalysts, especially FeNC catalysts, are considered promising candidates to replace Pt-based catalysts, but FeNC catalysts still present certain challenges in controlled-synthesis and energy device applications. In this paper, through the modification strategy of poly-dopamine (PDA) to maintain 2D leaf morphology to obtain more active sites and further adjust the N content, N-doped porous carbon monatomic iron catalyst (Fe/NPCs) with rich-nitrogen content was prepared. XPS analysis showed that compared with C-ZIF-Fe, the contents of graphite nitrogen and pyridine nitrogen increased in Fe/NPCs. The hollow structure with defects and Fe-N configuration of Fe single atom show more active sites for the catalyst, and positively promote the diffusion of reactants, oxygen exchange and electron transport, thus changing the reaction kinetics and promoting the improvement of ORR activity. Fe/NPCs electrocatalyst exhibits good half-wave potential and onset potential at low loading (E = 0.93 V, E = 1.0 V). In addition, the methanol tolerance, stability and Tafel slope are better than those of commercial Pt/C. Excitingly, the zinc-air cell with Fe/NPCs as cathode material achieves a power density of 223 mW cm and exhibits a long-term stability higher than 200 h. This work shows that nitrogen-doped porous carbon materials as well as iron monoatoms play important roles in improving electrocatalytic performance.