Nanostructured amorphous RuO2 · xH2O/C composite materials are prepared via a modified sol-gel process using glycolic acid. The glycolate anion, which dissociates from glycolic acid at pH 7, behaves as a stabilizer by adsorbing onto the RuO2 · xH2O surface, thus resulting in particles with a size of about 2 nm. As evidenced by zeta potential measurements, the surface charge of RuO2 · xH2O becomes more electronegative as the amount of glycolic acid increases. After heat treatment at 160 oC to remove the stabilizer, RuO2 · xH2O/C is found to exhibit an amorphous structure. The specific capacitance of RuO2 · xH2O/C particles (40 wt% Ru) prepared in the presence of glycolic acid (0.3 g L-1) is 462 F g-1, which is 30% higher than that of the material prepared in the absence of glycolic acid. Both the nanosized particles and the amorphous structure mainly contribute to this increase in the specific capacitance.
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