High-performance transition metal nitride/carbon nanofiber composites as positive electrode in rechargeable Zn-air batteries

Rechargeable zinc-air batteries (ZABs) represent one of the most promising devices for future portable energy storage. However, bifunctional and cost-effective electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) need to be developed for practical real-world scenarios. This work presents a comprehensive optimisation of the simple and green hydrothermal method to synthesise metal (Co/Fe) nitrides integrated with carbon nanofibers (CNF). The prepared nanocomposites exhibit remarkable electrocatalytic performance in OER and ORR. The combination of both metals in the CoFe–Fe 3 N/CNF material induces the highest bifunctional activity, attributed to a synergistic effect between the metals and the presence of a thin layer of cobalt oxide at the surface. The CNF content in the composite material is optimised, revealing the favourable CNF concentration of 60 wt%. The electrocatalysts with the highest bifunctional activity were evaluated as positive electrodes in ZABs, achieving superior cycling stability compared to a commercial Pt/C–RuO 2 electrocatalyst, and sustaining stability up to 60 h at a current density of 5 mA/cm 2 . These results underline the significant potential of cobalt-iron nitride/carbon nanofiber composites as highly efficient catalysts for oxygen electrochemical reactions and as promising components for improving the performance of rechargeable Zn-air batteries, thus contributing to the advancement of clean energy technologies.