The Preparation And Catalytic Performances Of TiO₂ And TiO₂-Carbonaceous Composites

TiO2 nanomaterials have attracted particular attention due to its fascinating properties, such as high surface area, photoinduced activities and good biocompatibility for their uses in the fields such as in enzyme immobilization, photocatalysis and photovoltaics. Nevertheless, few papers involved the improved electrochemical activity of TiO2 film with special nanostructure and the immobilization of enzyme on it have been reported. On the other hand, when TiO2 nanomaterial was used as a photocatalyst, its photocatalyic efficiency is usually very low and easily subjected to the loss of TiO2 nanomaterial and the difficulty in the recovery of TiO2.Based on these problems, we have prepared SDS-doped TiO2 film,CNTs-TiO2 and graphene oxide-TiO2 composite with the liquid phase deposition and applied these composite in the field of electrocatalysis and phtotocatalysis.With the surfactant sodium dodecyl sulfonate (SDS) as a dopant and structure director and (NH4)2TiF6 as the TiO2precursor, SDS-doped TiO2 film has been fabricated at room temperature. The SEM characterization showed that the TiO2 film was composed of two layers:the bottom layer with TiO2 grains and the top layer consisted of nanosheets, which are aggregated to a flower-like shape. The SDS concentration played a key role on the shape evolution of TiO2:a lower SDS concentration resulted in the formation of only TiO2 grains, and a higher SDS concentration was favorable to the growth of TiO2 nanosheets. And the optimum temperature was found to be 30 (?) for the growth of TiO2 nanosheets. After being doped with SDS, the reduction peak, being attributed to the reduction of hydroxylated titanium(Ⅳ) species, in the cyclic voltammograms of TiO2 films was siglifictantly enhanced. The varied surface structure of the SDS-doped TiO2 film provided a biocompatible platform for immobilizing hemoglobin, and the hemoglobin-immobilized film electrode exhibited good electrocatalytic activity to the reduction of H2O2. As a sensor for the determination of H2O2, the hemoglobin-immobilized film electrode yielded an excellently linear range from 0.003 to 1.5 mM H2O2 in the correlation between reduction peak current and H2O2 concentration, with a low detection limit of 1.0μM.Composite films of TiO2 and carbon nanotubes (CNTs) were prepared on titanium sheets with a dip-coating and liquid phased deposition and the photoelectrocatalytic (PEC) properties of the films were investigated through the degradation of methyl orange. It was demonstrated that CNTs in the TiO2 film significantly decreased the charge transfer resistance and increased the anodic photocurrent response of the film under UV light irradiation. The PEC performance of the CNTs-based composite film could be tuned by controlling the preparation parameters including the deposition time and calcination temperature. The deposition time and calcination temperature were optimized at 1 h and 450 (?), respectively. On the TiO2/CNT film prepared under the optimized conditions, 95% of the initial 10 mg/L methyl orange was degraded within 90 min, which was much higher than the 60% removal seen on the pure TiO2 films.Based on liquid phased depositon, a simple method to synthesize graphene oxide/TiO2 composites as a highly efficient photocatalyst by in situ depositing TiO2 nanoparticles on graphene oxide nano-sheets was developed. There are several advantages for this method. TiO2 nanoparticles are assembled onto the graphene oxide sheet to form larger particle s in the microscale, which could be easily separated by the filtration. Additionally, SEM and BET characterization showed the two-dimensional porous graphene oxide/TiO2 composites had specific surface area of 80 m2 g"1 being considerably larger than that of P25 and the similarly prepared neat TiO2 particles without using graphene oxide. The composites exhibited excellent photocatalytic activity, being influenced by post-calcination temperature, graphene oxide content and solution pH. Under optimal conditions (the concentration of graphite oxide was 75 mg/mL and calcination temperature was 200 (?)), the photo-oxidative degradation rate of methyl orange and the photo-reductive conversion rate of Cr(Ⅵ) over the composites were as high as 7.4 and 5.4 times that over P25, respectively. The excellent enhancing effect of graphene oxide nano-sheets on the photocatalytic properties of TiO2 was attributed to a thin two-dimensional sheet support, a large surface area and much increased adsorption capacity, and the strong electron transfer ability of the thermally treated graphene oxide in the composite.