Hierarchical porous Fe/Ni-based bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries

Abstract

Developing sustainable and efficient bifunctional catalysts for oxygen reduction (ORR) and evolution (OER) reactions is challenging for energy conversion and storage. This work proposes a hierarchical carbon matrix decorated with nitrogen atoms (NC) as a support for obtaining high-performance electrocatalysts based on iron and nickel (Fe/Ni@N–C). The effect of different Fe:Ni ratios and the pyrolysis conditions on the catalyst performance were investigated by combining electrochemical tests, N2-adsorption-desorption, X-ray diffraction, Transmission Electron Microscopy, and X-ray photoelectron spectroscopy. Once optimized the pyrolysis conditions and the Fe:Ni ratio, the Fe/Ni@N–C catalyst showed high bifunctional OER/ORR activity in a three-electrode cell in an alkaline environment (KOH 1 M), with an overall ΔE for the ORR-OER reaction of 0.75 V. Fe/Ni@N–C was assembled in a rechargeable zinc-air battery, resulting in an excellent electrochemical performance in terms of power density (148.5 mWcm−2) and durability, outperforming the benchmark Pt/C–RuO2.