A comparative study of electrocapacitive properties of manganese dioxide clusters dispersed on different carbons

Manganese dioxide (MnO2) clusters were directly grown on different carbons, including reduced graphene oxide (RGO), multi-wall carbon nanotubes (CNTs), and carbon black (Vulcan XC-72), via a chelation-mediated aqueous solution method. The electrocapacitive properties of the composite materials were evaluated by using cycle voltammetry, electrochemical impedance spectroscopy (EIS), and charge/discharge techniques. The composite electrode consisting of RGO and MnO2 performed the best among the composite electrodes studied with a specific capacitance as high as 260 F/g at a current density of 0.3 A/g. EIS data revealed the smallest charge transfer resistance in electrode. The results suggest that two-dimensional (2D) RGO sheets are an excellent support for pseudocapacitive MnO2. This study provides fundamental insights into the role of a carbon support in carbon–transition-metal-oxide composite electrodes for supercapacitors.