Electrochemical performance of RuO2-TiO2nanotube hybrid electrode material

Electroactive ruthenium oxide is full filled into as-prepared TiO2 nanotube array to form ruthenium oxide-titania (RuO2-TiO2) nanotube hybrid for the energy storage application, which is well prepared through a controlled differential pulse voltammetry electrodeposition process. The microstructure characterization of RuO2-TiO2 shows that RuO2 nanoparticles are uniformly deposited on the TiO2 nanotube walls and keep an open pore mouth. Electrical conductivity is highly increased, meanwhile ohmic resistance and charge transfer resistance are highly decreased due to well-covering RuO2 nanoparticles on TiO2 nanotube array with ruthenium atom ratio of 6.26%. Electrochemical capacitance is accordingly enhanced from 0.19 mF cm−2 of TiO2 and 39.6 mF cm−2 of RuO2-TiO2 in sulfate acid electrolyte. Solid-state supercapacitor is also constructed using RuO2-TiO2 cathode, porous carbon anode and polymer gel electrolyte. It achieves superior specific capacitance of 16.06 mF cm−2 and energy density of 0.029 mW h cm−2 at the expanded potential window of 1.8 V. It also shows the capacitance retention of 78.9% after 1000 cycles, presenting high cycling stability. The utilization efficiency of electroactive RuO2 is intensively improved due to uniform deposition on TiO2 nanotube walls. RuO2-TiO2 nanotube hybrid with superior capacitance performance is ascribed to the increased conductivity and the promoted Faradic reaction of RuO2.