Thermal-induced growth of RuO2nanorods from a binary Ru–Ti oxide composite and alteration in supercapacitive characteristics

Abstract

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.