Graphite-N modified single Fe atom sites embedded in hollow leaf-like nanosheets as air electrodes for liquid and flexible solid-state Zn-air batteries

The oxygen reduction procedure requires the development of an extremely effective, easily fabricated, and non-noble metal electrocatalyst. In this paper, we offer an unique method for manufacturing a defect-rich Fe single-atom catalyst loaded on the N-doped porous carbon nanosheets carrier (Fe-N4@NC-PCSs) by in-situ pyrolysis of a double-layered leaf-like compound (ZIF-L@PDA-FePhen) using dopamine hydrochloride aided precursor ZIF-L. The Fe-N4@NC-PCSs catalyst exhibits exceptional oxygen reduction reaction (ORR) activity across the pH-universal range, particularly in alkaline electrolytes, with a prominent half-wave potential of 0.938 V, outperforming practically previously described non-noble electrocatalysts as well as the commercial Pt/C catalyst (0.84 V). At pH-universal, the Fe-N4@NC-PCSs catalyst exhibits exceptional half-wave potential and an impressive electron/proton transfer ability resulting from its rich iron nitrogen active sites and a significant number of metal defects. Furthermore, the liquid zinc-air battery, as well as the flexible solid-state battery based on Fe-N4@NC-PCSs work excellently, with open circuit voltage of 1.465 V, maximum peak power density of 207 mV cm−2, and good charge–discharge endurance and mechanical flexibility. Calculations using density functional theory show that graphitic nitrogen can improve the local electronic redistribution for active sites and give them a lower free-energy barrier to ORR. This work serves as motivation for the creation of nitrogen moiety regulation extremely reactive atomic metal catalysts.