Hydrous Ruthenium Oxide as an Electrode Material for Electrochemical Capacitors

Abstract

The hydrous ruthenium oxide has been formed by a sol-gel process. The precursor was obtained by mixing aqueous solutions of RuC13 9 xH20 and alkalis. The hydrous ruthenium oxide powder was obtained by annealing the precursor at low temperatures. The crystalline structure and the electrochemical properties of the powder have been studied as a function of the annealing temperature. At lower annealing temperatures the powder is in an amorphous phase with a high specific capacitance. Specific capacitance as high as 720 F/g was measured for the powder formed at 150~ When the annealing temperature exceeded 175~ the crystalline phase was formed, and the specific capacitance dropped rapidly. The surface area of the powder and the resistivity of the pellet made from these powders have also been studied. The specific surface area and the resistivity decreased as the annealing temperature increased. A capacitor was made with electrodes comprised of hydrous ruthenium oxide and HzSO4 electrolyte. The energy density of 96 J/g (or 26.7 Wh/kg), based on electrode material only, was measured for the cell using hydrous ruthenium oxide electrodes. It was also found that hydrous ruthenium oxide is stable in H2SO4 electrolyte.

Redox and electrochemical water splitting catalytic properties of hydrated metal oxide modified electrodes

“…[55][56][57] More recently, attention has also focused on sol-gel techniques, which are reported to give fewer residual impurities and thus, enhanced service lifetimes. 50,[58][59][60][61] That said, the popularity of the thermal method is understandable given the ease with which oxide and, in particular, mixed oxide electrodes may be prepared. In this procedure a metal salt or a predetermined mix of metal salts in the desired stoichiometry are dissolved in a suitable solvent, often water or isopropanol, and the resulting solution is concentrated until a 'paste' consistency has been achieved.…”

Synthesis of ordered mesoporous ruthenium by lyotropic liquid crystals and its electrochemical conversion to mesoporous ruthenium oxide with high surface area

“…Such treatment would results in pore collapse, particle ripening, and loss of intra-particle water, in turn leading to smaller surface area and specific capacitance [43] [44]. The specific capacitance is unfortunately smaller than reported values for RuO 2 •nH 2 O prepared by sol-gel synthesis [25,26], most likely due to the larger primary particle size of RuO x (2 to 3 nm in diameter) constituting the walls and possible incomplete oxidation. Figure 1.…”

“…Takai et al have briefly reported on the synthesis of mesoporous Ru black with surface area of 62 m 2 g -1 via lyotropic crystal templating as the end member of the Pt-Ru alloy [23]. In addition to metallic Ru, high surface area ruthenium oxide is also an important material for various applications, including electrocatalysts for chlorine evolution [24], electrochemical capacitor electrodes [25][26][27][28][29], as well as fuel cell electrocatalysts [30][31][32][33][34][35][36][37][38][39]. The small particle size (1-2 nm) and the existence of appreciable pores are important requirements for the high capacitance [40][41][42].…”

“…The small particle size (1-2 nm) and the existence of appreciable pores are important requirements for the high capacitance [40][41][42]. The synthesis of high capacitance RuO 2 (~700 F g -1 ) have been conducted mainly by sol-gel synthesis, leading to materials with random micropores [25,26]. Surfactant assisted synthesis of ordered mesoporous RuO 2 have so far lead to material with substantially low capacitance values, i.e.…”

Hydrothermal synthesized porous Co(OH)2 nanoflake film for supercapacitor application

“…Pseudocapacitive materials, such as transition metal oxides/hydroxides and conducting polymers, are being explored for producing supercapacitors with increased specific capacitances (several times larger than those of carbonaceous materials) and high energy densities [2−6]. RuO 2 -base electrode materials are well studied as pseudocapacitive electrode materials with remarkable performance (760 F g −1 for a single electrode system) [7]. However, apart from being toxic, RuO 2 is quite expensive for extensive commercial applications.…”