Effect of annealing temperature on electrochemical characteristics of ruthenium oxide/multi-walled carbon nanotube composites

The preparation and characterization of high-surface-area ruthenium oxide (RuO2)/multi-walled carbon nanotubes (MWCNTs) composite electrodes for use in supercapacitors is reported in this work. The RuO2/MWCNTs composites were prepared by the polyol process of RuO2 into MWCNTs and by Ru annealing in air before mixed with MWCNTs. The chemically oxidized and annealed Ru nanoparticles contribute a pseudocapacitance to the electrodes and dramatically improve the energy storage characteristics of the MWCNTs. These composites annealed at 200 °C demonstrate specific capacitances in excess of 130 F/g in comparison to 80 F/g for pristine MWCNTs. The annealing temperature is found to play an important role, as it affects the electrochemical performance of annealed RuO2/MWCNTs composites critically due to its influence on the diffusion of protons into the structure.