Multi-level Porous Fe, Co, N, S Co-doped Three-Dimensional Graphene-like Catalyst as the Excellent Trifunctional Electrocatalyst for Liquid and Flexible All-Solid-State Zinc–Air Batteries

The porous structure engineering, as an easily overlooked part of the electrocatalyst, plays a crucial role for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) of the zinc–air battery (ZAB). Herein, a Fe, Co, N, and S co-doped three-dimensional (3D) porous graphene-like catalyst (FeCo–N,S-G) is prepared via the dual template strategy. CaCl2 is used as an inexpensive and readily available raw material to create pores. ZnCl2 evaporates and etches carbon substrates at high temperatures to further prepare multi-level pores and abundant defect structures. The porous structure is important for exposing high-density active sites and facilitates mass transfer. The prepared catalyst exhibits excellent ORR and OER activity. For ORR, the half-wave potential of FeCo–N,S-G is 0.88 V vs RHE. For OER, the overpotential of the catalyst is 350 mV at a current density of 10 mA cm–2 in 1 M KOH. Furthermore, FeCo–N,S-G exhibits enhanced hydrogen evolution reaction (HER) performance. The FeCo–N,S-G catalyst is applied to the air cathode of homemade aqueous ZAB and all-solid-state flexible ZAB, and the ZAB exhibits high peak power density and good charge/discharge stability performance.