Synthesis of Hydrous Ruthenium Oxide Nanoparticles in Sub- and Supercritical Water and Their Capacitive Properties

Abstract

Hydrous ruthenium oxide (RuO2 center dot nH(2)O) nanoparticles with various particle sizes and water contents were synthesized in sub- and supercritical water in a very short reaction time of 15min. The particle size, surface area, morphology, crystalline structure, and electrochemical properties were analyzed and compared with those of commercial RuO2 particles. Ultrafine spherical RuO2 center dot 0.6H(2)O nanoparticles with an average size of 4.2nm were produced in subcritical water (250 degrees C, 300bar), while larger and more highly crystalline rod-shaped RuO2 center dot(0.3-0.5)H2O particles were produced in supercritical water (400 degrees C, 300bar). The use of NaOH under the supercritical water conditions resulted in a decrease in particle size. The hydrous RuO2 nanoparticles synthesized in subcritical water exhibited a much higher specific capacitance (255Fg(-1)) at a scan rate of 10mVs(-1) than those synthesized in supercritical water (77Fg(-1)) and commercial RuO2 (8Fg(-1)).