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

Abstract

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.

Ternary MOF-Based Redox Active Sites Enabled 3D-on-2D Nanoarchitectured Battery-Type Electrodes for High-Energy-Density Supercapatteries

“…In particular, the MOF-based materials with hierarchical nanostructures could provide a credible solution to accelerate the capacity and rate performance owing to the enriched redox active sites, rapid electrolyte diffusion channels, and multi-electron transportation paths [26]. The various mixed MOFs with one-dimensional (1D), 2D, and 3D nanostructures have been reported, such as Co-Ni-MOFs@ rGO hybrids, Ni-Co-MOF nanosheets, flower-like metallic MOFs (Co-Ni-MOFs), and porous Co-Mn-based MOF nanostructures, synthesized using various growth methods, which showed better energy storage properties and cycling stability [29,[31][32][33]. The time-consuming/high-temperature synthesis, limited electroactive sites, and rather poor redox chemistry of these solitary nanostructures have initiated researchers to develop rational combination of hierarchical redox-type MOFs with controlled geometries to enhance the energy density of supercapatteries.…”

Bimetallic Metal-Organic Framework-Derived Carbon Nanotube-Based Frameworks for Enhanced Capacitive Deionization and Zn-Air Battery

“…However, MOF-derived carbons are normally in powder form, which is difficult to form a firm interaction within a flexible electrode. Third, previous reports have shown that metallic content within MOF-derived carbons play an essential role in their catalytic properties (Liu et al, 2017b; Zhang et al, 2018a; Zheng et al, 2019). The effects of bimetallic MOF precursors on the performance of derived carbon materials are rarely investigated.…”

Metal–organic framework based bifunctional oxygen electrocatalysts for rechargeable zinc–air batteries: current progress and prospects

“…4F). 61 This introduction of the rGO structure greatly improves the conductivity of the composites. The pristine MOF nanosheets grown on rGO have a synergistic effect with rGO, and the active sites are exposed to a large extent.…”

“…[99][100][101] However, the conductivity of metal oxides limits their catalytic activity. 57,61,[102][103][104][105] It is worth noting that the use of metal oxides and metal nanoparticle composites, or xed metal oxides on a highly conductive carbon matrix and other reasonable strategies can effectively promote the internal and surface charge transfer and maximize the utilization of active sites, which can further improve the efficiency of ZABs. 102,106,107 The weak coordinate bond and uniform morphology of MOFs make them good precursors to prepare hollow nanostructures using the Kirkendall effect.…”