Molecularly engineered potential of d-orbital modulated iron-bridged delaminated MBene for rechargeable Zn–air batteries

Abstract

An air cathode with high catalytic activity and reversibility toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is designed using an engineered Fe d-orbital strategy through the typical coordinations of iron phthalocyanine molecule (Fe_Mc) crystals on delaminated MoAl_1−xB MBene sheets (Fe_Mc–MoAl_1−xB). The hybridization induces unique electronic guest–host interactions with significant charge donation by MoAl_1−xB, resulting in remarkable regulation of the Fe3d charge delocalization and spin-state Fe(II) ion transition, thereby optimizing the adsorption/desorption of oxygenated intermediates with a balanced *OOH–*O transformation for simultaneously boosting both ORR and OER kinetics with high reversibility. Fe_Mc–MoAl_1−xB achieves a remarkable OER overpotential of 0.356 V at 10 mA cm⁻² while exhibiting a favorable half-wave potential of 0.862 V for the ORR in an alkaline electrolyte. An aqueous Zn–air battery (ZAB) assembled with an Fe_Mc–MoAl_1−xB air cathode demonstrates a high peak power density of 168.2 mW cm⁻² and a long cycling durability of 800 h, overperforming the (Pt/C + RuO₂) counterpart. These findings highlight the significance of such novel efficient air–cathode catalysts by performing electronic structure engineering of Fe_Mc with MoAl_1−xB to develop rechargeable ZAB devices with enhanced performance and cost effectiveness.