Electrochemical capacitance from carbon nanotubes decorated with titanium dioxide nanoparticles in acid electrolyte

摘要

The electrochemical activity of an electrode of carbon nanotubes (CNTs) attached with Ti0_2 nanoparticles was investigated. A chemical-wet impregnation was used to deposit different Ti0_2 particle densities onto the CNT surface, which was chemically oxidized by nitric acid. Transmission electron microscopy showed that each Ti0_2 nanoparticle has an average size of 30-50 nm. Nitrogen physisorption measurement indicated that the porosity of CNTs is partially hindered by some titania aggregations at high surface coverage. Cyclic voltammetry measurements in 1 M H_2SO_4 showed that (i) an obvious redox peak can be found after the introduction of Ti0_2 and (ii) the specific peak current is proportional to the Ti0_2 loading. This enhancement of electrochemical activity was attributed to the fact that Ti0_2 particles act as a redox site for the improvement of energy storage. According to our calculation, the electrochemical capacitance of Ti0_2 nanocatalysts in acid electrolyte was estimated to be 180 F/g. Charge-discharge cycling demonstrated that the Ti0_2-CNT composite electrode maintains stable cycleability of over 200 cycles.