Carbon titania mesoporous composite whisker as stable supercapacitor electrode material

Abstract

Titania carbon composites were prepared via in situ carbonization on mesoporous titania whiskers. Their microstructures were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), showing that the composites, after carbonization, still retain the original morphology of the whiskers and the crystalline structure of titania. Based on N₂ sorption isotherms, the average pore sizes of the as-prepared composites were found to depend on the amount of filled carbon. The electrochemical capacitance performance of the as-prepared composites was investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge cycles. Although the specific surface area of the composite TiO₂/0.252C is moderate at 156 m² g⁻¹, its specific volumetric capacitance of 25 F cm⁻³ was much higher than the value of 10 F cm⁻³ for Vulcan XC-72, which has a specific surface area of 236 m² g⁻¹. This enhanced capacitance may come from the composite mesopores derived from porous titania whiskers. They provide readily accessible diffusion pathways for electrolyte ions. There is better conductivity with carbon in the composite. After 2000 cycles, we observed a change of −2.8%, −2.6% and −1.9% decrease in the specific volumetric capacitance compared to the values at the 100th cycle of the composites TiO₂/0.252C, TiO₂/0.143C and TiO₂/0.08C, respectively. This decrease is small and significantly less than the 10% decrease of capacitance in Vulcan XC-72 in the same period. The more consistent capacitance in the composite suggests a more stable interface between titania, carbon filling and electrolyte compared to that of Vulcan XC-72 without titania.