Graphene Modified with Triruthenium Acetate Clusters as an Electrode for the Hybrid Energy Storage System

Electrodes combining battery and supercapacitor materials are an alternative to enhance energy and power densities in energy storage devices. Herein, a material of graphene modified with the triruthenium acetate coordination compound was synthesized through covalent functionalization of graphene. The structure and chemical composition of the material were characterized using scanning electron microscopy and infrared, Raman, and X-ray photoelectron spectroscopies. The electrochemical characterization through cyclic voltammetry and discharge curves revealed that triruthenium cluster-functionalized graphene has excellent charge–discharge capability with a cycling retention over 98% after 5000 cycles. Also, a synergistic effect was found at low specific discharge currents, with contributions of the triruthenium cluster Faradaic process and graphene double-layer capacitance to the storage capacity. At a specific discharge current of 0.25 A g^–1, the capacity of triruthenium cluster-functionalized graphene is 1.2 times that of graphene, reaching a specific capacitance of 11 F g^–1, but the capacity is limited by charge transport at high current densities and scan rates.