Ionic liquid-derived FeCo alloys encapsulated in nitrogen-doped carbon framework as advanced bifunctional catalysts for rechargeable Zn-air batteries

Abstract

Developing bifunctional ORR&OER electrocatalysts with high activity and stability is challenging for practical application of rechargeable Zinc air batteries. Herein, an ionic liquid strategy is proposed for construction of FeCo alloys encapsulated in nitrogen-doped carbon as bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). By taking advantages of the unique properties such as solvent effect and low volatility, ionic liquid serves as solvent to disperse metal ions in the precursor preparation and nitrogen-containing carbon source during pyrolysis. The FeCo alloy nanoparticles encapsulated in the N-doped carbon matrix show a homogeneous distribution with average sizes of 50–100 nm. Such a core-shell structure endows the catalyst with both high ORR and OER activity and robust stability in alkaline environments. Especially, the half-wave potential (E 1/2 ) for ORR is 0.86 V and the overpotential (E over ) for OER to reach the 10 mA·cm −2 current density is only 280 mV. Furthermore, the obtained bifunctional electrocatalyst also displays high efficiency and great durability when applied in the rechargeable Zn-air battery. The specific capacity and energy density at the discharge current density of 10 mA·cm −2 reach up to 741.5 mAh·g −1 and 830.1 Wh kg −1 , respectively. It’s envisioned that this ultra-facile method would be applicable to synthesize highly efficient catalysts for other energy conversion systems. • The FeCo@NC electrocatalyst is prepared through a facile two-step method by employing the ionic liquid ([EMIM][DCA]). • The FeCo@NC electrocatalyst exhibits excellent ORR and OER activity and stability in alkaline environments. • The FeCo@NC based Zn-air battery displays high efficiency and good reversibility.