Mechanosynthesis of a bifunctional FeNi–N–C oxygen electrocatalyst via facile mixed-phase templating and preheating-pyrolysis

Abstract

Metal–air batteries (MABs) offer a promising solution to address the intermittent nature of renewable energy sources and facilitate the global transition to green energy, thereby mitigating climate issues. However, efficient and affordable bifunctional electrocatalysts are essential to overcome the kinetic limitations of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in MABs, ensuring optimal performance and accessibility of these devices. This study reports a template-assisted mechanosynthesis of a bifunctional FeNi–N–C electrocatalyst by employing low-cost and sustainable FeCl₃, NiCl₂, 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ), melamine and KCl. Facile liquid-assisted grinding was utilized to produce KCl-templated FeNi-TPTZ metal–organic material, enabling template-induced stability of the catalyst. A carefully tailored pyrolysis strategy allows near-melt preheating of FeNi-TPTZ, increasing the concentration of active sites. Furthermore, the pyrolysis protocol enables the phase transition of KCl, functionalizing it as a solid–liquid template to achieve a high porosity (S_BET = 570 m² g⁻¹). The produced catalyst – IroNi-3D exhibits impressive ORR (E_1/2 = 0.82 V, E_onset = 0.92 V) and OER (E_j=10 = 1.52 V) performance with a ΔE of 0.70 V. In zinc–air battery testing, IroNi-3D outperforms PtRu with a power density of 144 mW cm⁻². This cost-effective FeNi–N–C electrocatalyst presents great promise for widespread use in MABs, advancing renewable energy storage and contributing to global climate change mitigation.