Thermal-induced growth of RuO ₂ nanorods from a binary Ru–Ti oxide composite and alteration in supercapacitive characteristics

The growth of crystalline RuO2 nanorods has been thermally induced from a binary Ru–Ti oxide prepared by oxidative precipitation in an aqueous solution consisting of RuCl3·xH2O, TiCl3 and H2O2. X-ray diffraction results show the formation of RuO2 nanocrystals as the annealing temperature is above/equal to 250 °C. The examination of surface morphology by transmission electron microscopic analysis confirms that the growth of RuO2 nanorods takes place in the high annealing temperature region. X-ray absorption spectroscopy (XAS) demonstrates that a minor amount of Ti atoms have been incorporated into crystalline RuO2, which partially occupy Ru sites in the octahedral RuO6 structure. The electrochemical results show that the binary Ru–Ti oxide annealed at 200 °C exhibits a much higher specific capacitance (ca. 2.5-fold improvement) and better capacitance retention in comparison with RuO2. Introducing Ti into RuO2 not only facilitates RuO2 utilization, but also enhances capacitance retention for the high-rate charge–discharge process. A schematic model is proposed to describe the growth mechanism of RuO2 nanorods from the binary Ru–Ti oxide and the function of Ti atoms within such composites for promoting the capacitive characteristics.