Synthesis of 2D bi-metallic Zn/Cu metal-organic framework integrated graphene nanocomposites for all-solid-state asymmetric supercapacitors

Abstract

In this work, a novel two-dimensional (2D) bi-metallic metal-organic frameworks (MOFs) consisting of zinc and copper metal centers with 1,3,5-tricarboxylic acid as a chief and efficient organic linker (Zn/Cu-BTC) and its composite with exfoliated graphene nanosheets (EGNSs) have been investigated for supercapacitor applications. The composites were synthesized via facile in-situ solvothermal process. Different spectroscopic, microscopic, and surface analyses confirmed the successful formation of porous electroactive composites, where 2D MOF nanosheets were vertically grown on the EGNS surfaces. In the two-electrode symmetric system, the as-synthesized Zn/Cu-BTC MOF@EGNS electrode achieved an enhanced specific gravimetric capacitance and equivalent volumetric capacitance of 1284.9 F/g and 813.3 F/cm3 at 0.5 A/g. It exhibits high-rate performance and prolonged cycling stability with >90 % retention after 8000 cycles. All-solid-state asymmetric supercapacitor (ASC) device was constructed with Zn/Cu-BTC MOF@EGNS composite and EGNS electrodes, where PVA-KOH membrane served as a separator-cum-electrolyte. The ASC device delivered a satisfactory energy density of 60.55 Wh kg−1 and a maximum power density of 10 kW kg−1 with an admirable cycling stability of 92 % after 10,000 charge-discharge cycles. In the future, this work can encourage manufacturing innovation.