Partial Cu substitution in Ni-based metal-organic framework for aqueous supercapacitor cathodes

Abstract

Over the past few decades, due to the limited amount of fossil fuel, research into energy storage systems has been regarded as one of the important studies along with the study of developing renewable energy sources. Super capacitors materials, one of the various types of energy storage systems, have been studied as promising energy storage materials for the future. In this study, among the substances used as super capacitors, a nickel-based organic framework (MOF) was selected to improve electrical conductivity, a fatal disadvantage of this material. For this purpose, partial substitution of copper metal with four different proportions (0.5%, 1.0%, 3%, 5%) for nickel metal in the nickel-based MOF was conducted to synthesize Cu-substituted Ni MOF and this material was studied. The above four materials’ nanostructure and chemical characteristics were verified, and electrochemical performances of them were measured by using cyclic voltammetry and constant current charge discharge technique. In addition, to ensure that partial replacement with copper actually improves the electrical conductivity of metal organic framework, DFT simulation focused on the charge transfer was also conducted. Through the above analysis and simulation, we found that the metal organic framework with partial metal substitution showed a better capacitance value than the metal organic framework without the substitution, thus demonstrating its potential as an electrochemical energy storage electrode material.