Design and Facile Synthesis of Highly Efficient and Durable Bifunctional Oxygen Electrocatalyst Fe-Nx/C Nanocages for Rechargeable Zinc-Air Batteries.

Abstract

Looking for a high-efficiency, durabile, and low-cost dual-functional oxygen electrocatalyst as the air electrode catalyst in rechargeable zinc-air batteries (ZABs) is urgently desirable but faces many challenges. Herein, we propose the preparation strategy of effectively using a bifunctional electrocatalyst (Fe-Nx/C) based on the zeolite imidazole organic framework-8 (ZIF-8) as the template agent, with surface modification coated by ferrocene (Fc) molecules followed by pyrolysis at high temperature under inert atmosphere. Benefiting from the surface modification of ZIF-8 with Fc molecules, more abundant multiple catalytic Fe/Fe-Nx/FeCx sites with high intrinsic activity are derived, the resultant Fe-Nx/C exhibits excellent potential gap (ΔE = 0.63 V) and durability, which is obviously superior to the Pt/C + IrO2 benchmark (ΔE = 0.77 V) and other state-of-the-art electrocatalysts. Furthermore, the assembled rechargeable ZABs employing the Fe-Nx/C as an air-electrode show a reduced charging-discharging potential difference of 0.603 V, high power density of 214.8 mW cm-2, and long-term cycling stability of more than 290 h at 2.0 mA cm-2. Therefore, this work presents a feasible strategy to prepare a high-efficiency and durability ORR/OER bifunctional electrocatalyst toward high performance ZABs and next-generation energy storage devices.