Electrochemical impedance spectroscopy was conducted on a series of hydrous ruthenium oxides, RuO(2).xH(2)O, (x = 0.5, 0.3, 0) and a layered ruthenic acid hydrate (H(0.2)RuO(2.1).nH(2)O) in order to evaluate their protonic and electronic conduction. The capacitor response frequency was observed at lower frequency for RuO(2).xH(2)O with higher water content, which was suggested to be due to electrolyte exhaustion within the film and/or utilization of hydrated interparticle micropores that have high ionic resistance. Analysis of the impedance data indicated that the charge-transfer resistance through the film is not significantly affected by the water content in RuO(2).xH(2)O, and the capacitor frequency response is dominated by the protonic conduction. The capacitor response frequency of layered H(0.2)RuO(2.1).nH(2)O was comparable to RuO(2).0.5H(2)O. The high specific capacitance at low frequency for layered H(0.2)RuO(2.1).nH(2)O is attributed to the utilization of the expandable hydrous interlayer, which accounts for the ionic conduction. The present results demonstrate the importance of hydrous regions (either interparticle or interlayer) to allow appreciable protonic conduction for high energy and high power electrochemical capacitors.

The charge storage mechanism of nanostructured anhydrous and hydrous ruthenium-based oxides was evaluated by various electrochemical techniques (cyclic voltammety, hydrodynamic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy). The effects of various factors, such as particle size, hydrous state, and structure, on the pseudocapacitive property were characterized. The electric double layer capacitance (C dl), adsorption related charge (C ad), and the irreversible redox related charge (C irr) per unit mass and surface area of electrode material has been estimated and the role of structural water within the material either in micropores or interlayer are discussed.

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Ruthenic acid nanosheet colloids were prepared by dispersing a tetrabutylammonium-ruthenic acid intercalation compound in acetonitrile, or N,N-dimethylformamide. Nanosheet electrodes were fabricated on gold, indium-tin oxide (ITO)-coated glass, and ITO-coated PET electrodes by electrophoretic deposition using these colloids. Transparent or flexible electrodes could be fabricated by using ITO electrodes as the substrate. The deposited amount of material could easily be controlled by the extent of deposition, which was confirmed from the linear increase in specific capacitance as a function of the deposition time. The ruthenic acid nanosheet electrodes using Au substrates exhibited gravimetric capacitance of 620 F (g-RuO 2 ) -1 . Specific capacitance of 0.82 F cm -2 (geometric) was achieved at a scan rate of 2 mV s -1 with a film deposited at 5 V cm -1 for 1 h.

Rutile-type Ru 1-x V x O 2 nanoparticles possessing high surface area were prepared by a polymerizable-complex method and its electrochemical supercapacitor behavior was studied. X-ray diffractometry, energy-dispersive X-ray analysis, and N 2 adsorption/desorption measurements were used to characterize the structure of the products. The electrochemical supercapacitor behavior of thick and thin films was studied by cyclic voltammetry in various acidic, neutral, and alkaline electrolytes.Ru 1-x V x O 2 exhibited extremely enhanced supercapacitive properties compared to pure RuO 2 . The highest surface redox activity was achieved with an acidic electrolyte.Ru 1-x V x O 2 showed negligible surface redox activity in neutral electrolytes.

An ion-exchangeable ruthenate with a layered structure, K 0.2 RuO 2.1 , was prepared by solid-state reactions. The interlayer cation was exchanged with H

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