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

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.