Bimetallic Metal-Organic-Framework/Reduced Graphene Oxide Composites as Bifunctional Electrocatalysts for Rechargeable Zn-Air Batteries

The most challenging issue in the development of metal air batteries is the insufficient catalytic activity of the cathode toward oxygen evolution and reduction reactions (OER/ORR). Metal-organic frameworks (MOFs) and MOF-based electrocatalysts have drawn considerable attention for the replacement of noble-metal electrocatalysts. Here, the rational design and synthesis of bimetallic CoNi-MOF nanosheets/reduced graphene oxide (rGO) hybrid electrocatalysts is reported. The CoNi-MOF nanosheets were in situ grown onto rGO assisted by the surfactant modulation. The newly developed CoNi-MOF/rGO hybrids, consisting of homogeneously distributed nanosheets encapsulated by rGO, display excellent electrocatalytic activities toward OER and ORR. The much improved bifunctional catalytic performance is ascribed to the synergy among the CoNi-MOF nanosheets and rGO, the abundant exposed active sites, and the enhanced electron conductivity. Moreover, the rechargeable Zn-air batteries with CoNi-MOF/rGO-based air electrodes display high energy density and cycling stability, demonstrating the great potential as advanced bifunctional electrocatalysis in electronic devices.