Fabrication And Electrochemical Performance Of The TiO₂and Ccoarposite Nanostructure

Supercapacitors offer a novel alternative approach to store and deliver energy at high ratesmeet the increasing demands of energy storage devices and are widely used in mobileequipment power supply, hybrid electric vehicle and aerospace field because of their highpower density and excellent cycleability. The high accessible surface area, ordered porenetworks, chemical stability and controllable size of anodized titania nanotube array make it anexcellent substrate material for supercapacitors because they not only provide a favorable pathfor the movement of the electrolyte and transportation of the ions, but also for the modificationof other active materials with high specific capacitance. Although the semi-conduction nature ofTiO₂is crucial for many of these applications, the limited conductivity prevents an even broaderand efficient use in super capacitor applications that require a fast electron transport. In thisthesis, novel compsosite nanostructures based on TiO₂nanotube have been fabricated and theirelelctrochemical properties investigated. The main results are submamarized as following:（1）The C-doped TiO₂-NTAs （C-TiO₂NTAs） electrode was fabricated by quick annealingof the as-anodized TiO₂nanotube arrays in argon but in the absence of foreign carbonaceousprecursors. The residual ethylene glycol （EG） absorbed on the nanotube wall during anodizationserves as the carbon source and the C species are uniformly distributed along the entirenanotube forming the C-TiO₂NTAs which improve the specific capacitance and conductivity.PANI was loaded on the C-TiO₂NTAs template through cyclic voltammetry. Because of theimproved conductivity of C-TiO₂NTAs, PANI was loaded effectively and easily. In addation,by means of changing the concentration of aniline monomer and the scan cycles in the processof cyclic voltammetry, we obtained three different kinds of microstructure: C-TiO₂-PANInanotubes, nanorods and disordered nanowire networks. It can be demonstrated that the specificcapacitance of the electrode is greatly enhanced after the electropolymerization.（2） The coaxial TiO₂/C nanotube arrays have been fabricated by glucose solutionhydrothermal reaction and further carbonization. The effection of the concentrate of glucoseand the annealing temperature on the morphology and electrochemical properties has beeninvestigated. Moreover, manganese oxide （MnO₂） was introduced and decorated along thenanotube inner wall by electrodeposition. It is discovered that the capacitance of the MnO₂decorating TiO₂/C NTAs （MnO₂-TiO₂/C） is much higher than that of the TiO₂/C NTAs.