Modification And Electrochemical Properties Of Tio2 Nanostructure Materials Research

Titanium dioxide （TiO₂） is one of the widely investigated materials for solar cells,photonic crystals, photocatalysis, gas sensors, electrochromic and self-cleaning devicesbecause of its unique physical and chemical properties. The major obstacles to theireffective utilization lie in poor photo-generated charge separation and inefficient use ofsunlight. To date, a variety of strategies have been utilized to improve TiO₂photoelectrochemical performance, such as coupling with secondary semiconductors,photosensitization of dyes, modification by metal and carbon nanoparticles, and dopingwith transition metals （Au, Pd, Pt, Rh, etc.） or nonmetal elements （N, S, I, F, etc.）.However, most of them still suffer from the unstable nature and lack of furthermodification and functionalization abilities. A promising solution is to control or tune theTiO₂photoelectrochemical properties via dimensional control instead of modification anddoping by heterogenous species. Another promising solution is to construct newnanosystem. Considering what mentioned above, in the present work, a TiO₂combined-nanostructure of small-sized nanoring and nanotube （R/T combined-structure）and carbon quantum dots （CQDs） loaded TiO₂nanotubes system were prepared and wellcharacterized. Additionally, the SrTiO₃film evoluted from the TiO₂nanotubes wasdeveloped. Meanwhile, the photoeleetroehemical and photoelectrocatalytic properties wereinvestigated. In this dissertation, some works were carried out as follows:（1） The TiO₂nano-ring/-tube （R/T） combined-structure was obtained by a simpletwo-step anodization. The as-prepared samples were characterized by X-ray diffraction,Raman, scanning electron microscopy, photoluminescence spectra, UV-vis absorptionspectroscopy and photoelectrochemical measurements. The photoelectrochemicalmeasurements demonstrate that the combined-structure shows high photo-to-currentconversion efficiency, fast charge transfer speed, and surface dominantphotoelectrochemical response. The behavior of photoelctrochemical activity in TiO₂R/T combined-structure and pure nanotubes （NTs） has been investigated throughelectrochemical impedance spectroscopy and photo-to-current conversion efficiencymeasurement. It is demonstrated that the formation of heterojuction structure in R/Tcomposite plays an important role in the kinetic behaviors （including charge separationefficiency and transport capability） of photogenerated charges. The TiO₂R/Tcombined-structure greatly increases charge separation efficiency and photoconversioncapability. Related work has been published in Journal of Physical Chemistry C.（2） CQDs particle were successfully loaded to the inner and outer wall surface of TiO₂nanotubes （TNTs） by impregnation deposition for the first time, which effectively improvethe light absorption range of TiO₂nanotubes and photoelectric conversion effect. Here weshow a bias-mediated electron/energy transfer process at the CQDs/TiO₂interface for thedynamic modulation of opto-electronic properties. Different energy and electron transferstates have been observed in the CQDs/TNTs system due to the up-conversionphotoluminescence and the electron donation/acceptance properties of the decorated-CQDs.Related work has been published in Nanoscale.（3） The SrTiO₃films were synthesized by a hydrothermal method using TiO₂nanotube arrays as precursor. The photoanode of SrTiO₃film decorated by CQDs iscapable of converting near IR photon energy to photocurrent. The efficient carrier transferand high electron/hole separation rate of the hetero-junction between the CQDs and SrTiO₃was achieved. Related work has been published in New Journal of Chemistry.According to these results, TiO₂nano-ring/-tube combined-structure array electrode,bias processing under the CQDs modified TiO₂nanotube array electrode and the CQDsmodified SrTiO₃nanofilm array electrodes, not only extend the optical response of TiO₂nanotube array electrode and application capabilities, but also improve the separationefficiency of photo-generated electron-hole pairs. The results are beneficial for furtherpromoting the development of photocatalytic technology towards practical application.