Effect of Electronic Resistance and Water Content on the Performance of RuO[sub 2] for Supercapacitors

Hydrous ruthenium oxide, , was prepared according to a sol-gel process and annealed at different temperatures. The importance of high electronic conductivity for high capacity in aqueous was revealed through two approaches. The electronic resistivity of measured in situ as a function of the electrode potential shows a marked increase toward low potentials. This trend is more pronounced for the low-temperature annealed oxide where it results in a limitation of the capacitance at vs reversible hydrogen electrode. This finding is in line with the steep rise of the electrochemical impedance in the same potential region. A possible way to overcome this limitation is to mix two differently heat treated oxides, one with high conductivity ( , Z300), the other with optimum capacity ( , Z150). The observed specific capacity increase of hydrous in the mixture from is attributed to an improvement of the electronic pathway along the particles of high-temperature-treated (Z300) toward the high-capacity Z150 particles.