Movable-type printing method to fabricate ternary FeCoNi alloys confined in porous carbon towards oxygen electrocatalysts for rechargeable Zn-air batteries†

Abstract

Transition metal-based carbon catalysts are a promising class of electrocatalysts to enhance the efficiency of energy conversion and storage devices. However, it remains a challenging task to develop multi-metal alloy catalysts. Herein, ternary FeCoNi alloy nanoparticles (NPs) confined in nitrogen-doped carbon (NC) catalysts were fabricated via a facile movable-type printing method, where a range of transition metals confined in NC catalysts was prepared using the same technique except for the adjustment of the metal precursors. Due to the unique electronic structure and significant active sites of the medium-entropy alloy, the FeCoNi-NC catalysts demonstrated highly efficient bifunctional electrocatalytic activities for the oxygen reduction (E_1/2 = 0.838 V) and evolution (E_{overpotential} = 330 mV, 10 mA cm⁻²) reactions, which were comparable to those of Pt/C and RuO₂. Moreover, the FeCoNi-NC-based liquid rechargeable ZABs displayed a substantial power density of 231.2 mW cm⁻², and the homemade flexible ZABs also exhibited outstanding activity and cycling durability. Thus, this movable-type printing method is suitable for constructing a variety of multi-metal-based catalysts for metal air batteries.