MIL-101(Fe)-derivatized cathode as an efficient oxygen electrocatalyst for rechargeable Zn-air battery

The exploration of multifunctional electrocatalysts with cost-effective and high kinetic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for the development of advanced energy conversion and storage equipment. Herein, a novel hierarchical mesoporous/macropores MIL-101(Fe) derivative carbon catalyst material was prepared by a simple molten ZnCl2-assisted synthesis route. Specifically, 1H-benzotriazole (BTA) organic ligands were intentionally introduced as nitrogen sources in order to induce the formation of charge-rich regions through an electronegative nitrogen doping control strategy, and most importantly, the lone pair electron-rich nature of element N could facilitate the separation and anchoring of iron species enchanted the utilization rate of active sites. Because of these properties, the as-prepared catalyst (denoted as FeSACs/NxC) possesses unrivalled bifunction electrocatalytic activity and durability for the ORR and OER. The FeSACs/N1.25C as working electrode exhibits a quite satisfactory electrochemical performance for the ORR (half-wave potential of 0.82 V) and OER (a small overpotential of 302 mV at 10 mA cm-2) in the classic three-electrode configuration. Moreover, the FeSACs/N1.25C-based air cathode imparts encouraging performance in a rechargeable Zn-air battery prototype with an open-circuit voltage of 1.45 V, a specific capacity of 792.16 mAh g-1, an energy density of 871.38 Wh kg-1, and excellent stability for 120 h. This work has opened the way for the development of low-cost, fast kinetic and stable non-noble metal multifunctional catalysts.