Synthesis, Modification And Electrochemical Properties Of Anodic TiO₂ Nanotube Arrays

As a electrochemical energy storage device, supercapacitors has attracted a great deal of interest in electrochemical energy storage fields for its fast and high power capability, long life, wide thermal operating range and low maintenance cost. TiO2 NTs has been widely used in supercapacitors for its high chemical stability, good electrochemical activity, cheap and environment friendly. However, TiO2 NTs has poor conductivity and low electrochemical activity which lead to small capacitance thereby restricting its applications in the construction of high performance supercapacitors. It is highly desirable to improve the conductivity and capacitive properties of TiO2 NTs. In this thesis, two-step anodization is employed to fabricate TiO2 NTs and the influences of theirs capactance in different anneal atmosphere are investigated. In addition, combination method of hydrogenated reduction,electrochemical polymerization and electrochemical deposition is employed to prepare polyaniline/black TiO2 nanotubes and reduced graphene oxide/polyaniline/black TiO2 nanotubes, thus greatly improve its electrical conductivity and electrochemical property. The details are presented as below:The influences of diferent anneal atmosphere on morphologies and structures of nanotubes and electrocehmical performance are studied.The result shows that annealed in H 2 atmosphere(H-TiO2 NTs), similar to annealed in O2 atmosphere(air-TiO2 NTs), can also convert the amorphous TiO2 NTs into anatase TiO2 NTs and that hydrogenation process does not damage its morphology. Compared with air-TiO2 NTs, H-TiO2 NTs has higher content of Ti3+ and hydroxyl groups thus improved electrical conductivity and electrocehmical activity.A combination method of hydrogenated reduction and electrochemical deposition is employed to prepare polyaniline/black TiO2 nanotubes(PANI/H-TiO2 NTs) and the influences of morphologies and structures of nanotubes and electrocehmical performance are studied. The result show that PANI/H-TiO2 NTs shows capacitance of 999 F/g at the current density of 0.6 A/g which is much higher than that of PANI/air-TiO2 NTs(189 F/g). Moreover, PANI/H-TiO2 NTs also shows remarkable long-term cycling stability with only 29.8 % reduction of the initial capacitance at a current density of 24.0 A/g after 2000 charge-discharge cycles.Reduced graphene oxide/polyaniline/black TiO2 nanotubes(RGO/PANI/H-TiO2 NTs) is prepared by combination method of hydrogenated reduction and electrochemical deposition and the influences of morphologies and structures of nanotubes and electrocehmical performance are studied. The results show that the capacitance of RGO/PANI/H-TiO2 NTs is as high as 1481 F/g. RGO/PANI/H-TiO2 NTs also shows remarkable long-term cycling stability with only 16.7 % reduction of the initial capacitance after 2000 charge-discharge cycles.The result of Electrochemical impedance spectroscopy shows that the charge-transfer resistance of RGO/PANI/H-TiO2 NTs is low, thus high conductivity.