Synergistic cobalt-MOF@rGO nanocomposites for high-performance supercapacitors and electrochemical detection of Cd2+ ions

Abstract

Metal–organic frameworks (MOFs) and carbon-based nanocomposites are becoming increasingly attractive porous materials for electrode fabrication and electrochemical energy storage owing to their enhanced electrical conductivity, substantial theoretical capacitance, and diverse range of applications. In this context, a new pseudocapacitive binary nanocomposite (PUC6@rGO), based on reduced graphene oxide (rGO) and a Co-MOF (PUC6), has been developed via a wet impregnation method. The unique structure–morphology relationship between the pseudocapacitive PUC6 MOF and highly conducting rGO favours rapid electrolyte-ion diffusion, resulting in improved electrochemical behaviour. At a current density of 1 A g⁻¹, the PUC6@rGO nanocomposite electrode delivered a considerable specific capacitance of 579 F g⁻¹. This material was further used to create a flexible symmetric supercapacitor device that achieved very high energy density and power density of 48.25 Wh kg⁻¹ and 250 W kg⁻¹, respectively. Furthermore, the device capacitance did not degrade even after 10 000 charge–discharge cycles, demonstrating superior cycling stability and long-term durability. Additionally, PUC6@rGO was employed as an electrochemical sensor for Cd²⁺ ion detection, achieving a low detection limit of 780 nM. The enhanced supercapacitor and sensing performance of this nanocomposite provides new opportunities for the design of multifunctional materials for a technologically sophisticated and ecologically responsible future.