Hierarchical porous Fe/Ni-based bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries
Beatrice Ricciardi, Williane da Silva Freitas, Barbara Mecheri, Khair Un Nisa, Jorge Montero, Valerio C.A. Ficca, E. Placidi, Cinthia Alegre, Alessandra D’Epifanio
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.