Fe–N/P-co-Doped Three-Dimensional Graphene Bifunctional Oxygen Electrocatalysts for Rechargeable Zinc–Air Batteries

The evolution of highly active dual-functional catalysts is critical to zinc–air batteries (ZAB). Herein, three-dimensional Fe–N/P-co-doped graphene (3D Fe–N/P-G) materials with a high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) response are prepared by a molten salt protection method with KCl. The 3D Fe–N/P-G exhibits a large Brunauer–Emmett–Teller (BET) surface area and a dense network of pores for improved mass transfer efficiency. The addition of P atoms is able to produce a synergistic effect that improves the ORR catalytic activity of the 3D Fe–N/P-G catalyst. Regarding electrical efficiency, the ORR half-wave potential (E1/2) of 3D Fe–N/P-G catalytic is 0.860 V vs reversible hydrogen electrode (RHE) and the electron transfer number is 3.98 from 0.4 to 0.7 V vs RHE. The small overvoltage (ΔE = Ej = 10 – E1/2) of 3D Fe–N/P-G is 0.77 V. Additionally, the zinc–air battery with 3D Fe–N/P-G as a trigger for the cathode has high power density (170 mW cm–2), specific capacity (671 mAh g–1), small charge/discharge polarization, and outstanding prolonged stability. It is suggested that 3D Fe–N/P-G is a powerful bifunctional cathode ZAB catalyst.