Facile electrochemical preparation of a composite film of ruthenium dioxide and carboxylated graphene for a high performance supercapacitor

Ruthenium and carboxylated graphene (CG) were co-electrodeposited at -0.25 V vs. SCE on a quartz crystal microbalance (QCM) Au electrode in a stirred aqueous dispersion containing 0.6 mM RuCl3, 1 mg mL(-1) CG and 0.1 M H2SO4. The Ru-CG composite was electrooxidized by cyclic voltammetry in 0.5 M aqueous H2SO4 to yield a RuO2-CG/QCM electrode for supercapacitor research. In situ QCM technique and ex situ scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, and Raman spectroscopy were used for process monitoring and/or film characterizations. The RuO2-CG/QCM electrode exhibited an apparent specific capacitance of 756 F g(-1), an energy density of 101 W h kg(-1) at a power density of 2.5 kW kg(-1), and high stability. The specific capacitance is higher than those of similarly prepared RuO2/QCM, RuO2-multiwalled carbon nanotubes (MWCNTs)/QCM, RuO2-graphene oxide/QCM electrodes and a castcoated CG/QCM electrode, as well as many reported RuO2-based electrodes. The present method for the preparation of the RuO2-CG composite film only needs two simple electrochemical processes (solution-stirred composite electrodeposition and then a solution-quiescent anodic treatment), which is promising for the facile preparation of other similar nanocomposite films for wider applications.