Rational design of iron single atom anchored on nitrogen doped carbon as a high-performance electrocatalyst for all-solid-state flexible zinc-air batteries

Developing a cheap and high-efficiency oxygen reduction reaction (ORR) catalyst is vitally important for high-performance metal-air and full cell batteries. Non-noble iron-nitrogen-carbon materials (Fe-N-C) are reported with outstanding ORR property. However, most of them needs complex acid etching procedure during the fabrication process. Herein, we report a simple route to obtain a cost-effective Fe-N-C electrocatalyst via a facile two-step polymerization-pyrolysis process, and no acid etching is involved. Through a conjunction process of phthalocyanine iron (FePc) with polypyrrole (PPy) and a followed pyrolysis step, atomically evenly dispersed Fe-N-C species on nitrogen doped carbon can be easily obtained. Predictably, the obtained optimal catalyst delivers a half-wave potential of 0.83 V vs reversible hydrogen electrode (RHE) and better stability toward ORR test. Based on the optimal Fe single atomic catalyst as air cathode, an all-solid-state flexible Zn-air battery delivers a high open circuit voltage of 1.42 V, a high energy density of 833 Wh kg⁻¹ and a high power density of 70 mW cm⁻². The superior electrochemical energy storage properties demonstrated by the Fe-N-C electrocatalyst show a bright window for reasonable construction of cost-effective non-noble Fe single atom electrocatalysts for next-generation flexible energy storage devices.