Coalescence inhibition of hydrous RuO2 crystallites prepared by a hydrothermal method

Coalescence of particulates accompanied with crystal growth upon annealing at/above 200°C, found for hydrous RuO2 (RuO2∙nH2O) prepared by a sol-gel process, is effectively inhibited by the formation of RuO2∙nH2O nanocrystallites in a hydrothermal process. This thermal stability, attributable to the barrier originated from the lattice energy of crystallites, maintains high water content, nanocrystalline structure, and porous nature of RuO2∙nH2O annealed at elevated temperatures from 200to400°C. A hydrothermal derived RuO2-based supercapacitor with high specific capacitance (ca. 200Fg−1 measured at 100mAcm−2) and a cycle lifetime longer than 40000cycles, resulting from thermal stability, is demonstrated.