CoFe/N doped biomass-derived carbon as multi-layer porous efficient bifunctional composite for zinc-air battery

Abstract

The development of bifunctional electrocatalysts to overcome the slow kinetics of the oxygen reduction reaction (ORR)/the oxygen evolution reaction (OER) is a significant challenge. Herein, Fe₈₀-ZIF-67@CN, a CoFe alloy nitrogen-doped multilayer porous carbon electrocatalysts is designed and successful prepared, natural eggshell membrane (ESM) as precursor, Graphitic carbon nitride (G-C₃N₄) as nitrogen source, and a small amount of iron and cobalt salts as non-noble metal sources. Due to the synergistic effect between the CoFe alloy and FeN_X, CoN_X sites, the Fe₈₀-ZIF-67@CN electrocatalysts display a half-wave potential (E_1/2) of 0.86 V (ORR), an overpotential (E_j10) of 339 mV (OER), and a potential difference (∆E) of 0.71 V. In addition, the Tafel slopes for the ORR and OER are 90.36 mV dec⁻¹ and 52.35 mV dec⁻¹, respectively. More importantly, the Zn-air battery assembled with Fe₈₀-ZIF-67@CN exhibits a large power density of 126.47 mW cm⁻², the open circuit voltage (OCP) of 1.54 V and excellent stability without significant voltage changes even after 176 h, which are superior to that of 20 % Pt/C + RuO₂. This work paves a new design option for oxygen electrocatalysts for zinc-air batteries.