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Abstract: The preparation of RuO2–Ta2O5/Ti electrodes, by dip-coating, for use in supercapacitors was investigated. The stability and specific capacitance of the electrodes annealed at various temperatures was examined. The results show that highly stable electrodes with a specific capacitance of 170FgRuO2 −1 were obtained at approximately 250°C, while electrodes with a lower capacitance (130FgRuO2 −1) were obtained at 300°C. The annealing time needed to obtain a stable RuO2–Ta2O5/Ti electrode at various temperatures correlates well with the Arrhenius’ law: with the activation energy (E) of the annealing reactions for the electrodes being estimated as 73.5kJmol−1. SEM images of the electrodes show the coating films to have rough surface morphology with cracks 2–6μm in width. XRD data indicate that the coating films obtained are composed of crystalline RuO2 and amorphous tantalum oxide. [ABSTRACT FROM AUTHOR]

Abstract: Hydrothermal treatment (HTT) of RuO2–Ta2O5/Ti electrode, as a method for improving their performance, for use in supercapacitors was investigated. The results show that HTT significantly enhances the stability of the electrodes. The specific capacitance of electrodes, subject to HTT in the temperature range 180–250°C remains unchanged after 1000 CV cycles between −0.2 and 1.1V vs. SCE; without HTT a decay to 97% of the initial is observed. The results also show that HTT decreases the activity of the electrodes for O2 and H2 evolution and increases the voltage window by 56–135mV for supercapacitors, but with a specific capacitance decrease of 7–27%. XPS analyses show the existence of more hydroxides after the HTT, which leads to a little increase in the interplanar distance as indicated in the XDR results. Contact angle measurements show the presence of a more hydrophilic surface after HTT. [Copyright &y& Elsevier]

Abstract: Anodic, cathodic and cyclic voltammetric (CV) deposition of ruthenium oxides from aqueous RuCl3 solutions have been investigated using stationary and rotating disk electrodes (RDE) in this work. The CV deposition behavior was examined using a RDE to differentiate the contribution of current from the reactions of ruthenium ions in the electrolyte and ruthenium oxides already adsorbed on the electrode. The results indicate that the CV growth of ruthenium oxides within the potential range of aqueous electrolyte decomposition is attributed to the anodic oxidation of ruthenium ions in the electrolyte. Cathodic deposition occurs only at potential negative than −0.30V versus saturated calomel electrode (SCE) when H2 evolves on the electrodes. Anodic deposition of ruthenium oxides can be obtained effectively in the potential range of ca. 0.9–1.1V versus SCE, depending on the pH value of the electrolyte. The optimum anodic and cathodic deposition potential for maximum deposition efficiency is 1.0 and −0.9V versus SCE, respectively, in the electrolyte solution of pH 2. [Copyright &y& Elsevier]