Synthesis and Strategies to Improve Electrochemical Performance of Iron-Carboxylate MOF-based Electrodes for High-Performance Supercapacitors

Abstract

Metal-organic frameworks (MOFs) have been reported as promising electrode materials for high performance supercapacitors. Significant research has been conducted to prepare MOF composites using conductive additives such as graphene nanosheets. Furthermore, conductive redox-active metals such as Copper and Cobalt have also been incorporated into MOF structures to boost up the electrochemical performance. However, in this work we used graphene nanosheets to influence the crystallization and growth of iron-MOFs followed by the washing away of graphene. This in-situ synthesis protocol was carried out via a facile hydrothermal approach. Later, the conductive Copper was also added into the MOF to investigate its influence on the performance of electrode material. The synthesized materials (i.e., Fe-MOF, Fe-MOF/G, and FeCu-MOF/G) were tested against their electrochemical performance using a tri-electrode electrochemical system in 1M KOH solution. These MOF samples were characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and Raman spectroscopy. The electrochemical properties of the prepared samples were analysed using cyclic voltammetry (CV), galvanostatic charge and discharge (GCD), and electrochemical impedance spectroscopy (EIS). The in-situ growth of iron-MOFs using graphene resulted in enhanced specific capacitance and higher charge/discharge stability which validates the superiority of this in-situ synthesis approach. One of the developed electrode materials, FeCu-MOF/G, displayed a high specific capacitance of 1132 Fg−1 at current density of 3 A g −1 . Moreover, FeCu-MOF/G also showed a cyclic charge/ discharge stability of 85% for 6000 cycles at 10 A g−1 . The exceptional performance displayed by the developed MOFs in the presence of graphene are highlighted their potential as appropriate electrode materials for supercapacitors. The in-situ growth of iron-MOFs using graphene resulted in enhanced specific capacitance and higher charge/discharge stability which validates the superiority of this in-situ synthesis approach.