Hydrous, crystalline, binary (Ru–Ti)O2·nH2O with compositions equal to the ratios of metallic ions in the precursor solutions are successfully synthesized by a mild hydrothermal process. The maximum utilization of RuO2·nH2O (ca. 793F/g) occurs at the composition of 60M% TiO2·nH2O although phase separation is clearly found for this TiO2-enriched binary oxides. The nano-structured architecture with a high BET surface area (ca. 253m2/g) of the hydrothermal-derived (Ru–Ti)O2·nH2O with annealing at 200°C favors the physical adsorption of water and maintains a high water content which is novel and never found before. Due to this novel nanostructure, the annealed (Ru–Ti)O2·nH2O synthesized by means of the hydrothermal process exhibits excellent performances (i.e., high utilization of RuO2, high power property, and long cycle life) for supercapacitors.