Preparation And Performance Of TiO₂in Ionic Liquid

Titanium dioxide(TiO2) has been a photocatalytic material in common because of its low cost, stability of the physicochemical properties and wide availability. The valence band electrons from the TiO2are excited to the transition to the conduction band under visible light illumination, and the formation of free electrons could be reacts with oxygen to product superoxide free radical. Meanwhile, the electron hole in the valence band with water or hydroxide ion reaction generation the hydroxyl radicals. However, the application of TiO2is limited because the electron-hole pairs should be composit again easily which lead to reduce the efficiency of TiO2photocatalytic. Many studies show that TiO2with high crystallinity and large surface area has the higher photocatalytic efficiency.The mesoporous anatase TiO2material are prepared by an ionic liquid modified sol-gel method using tetrabutyl titanate as a titanium source. The prepared TiO2is characterized by N2-physisorption, X-ray diffractometer, Fourier transform infrared spectroscope and transmission electron microscope, respectively. The results showes that the mesoporous sample TiO2prepare with the addition of ionic liquid of2.5ml and calcined at300℃exhibite large specific surface area (178.1m2·g-1), and particles of the sample TiO2was approximately20nm, The photocatalytic degradation experiment of methyl orange indicated that the sample TiO2prepared added ionic liquid of2.5ml exhibit a higher photocatalytic activity. Product of calcined at700℃is still anatase crystal phase, indicating that the product has good thermal stability.In order to improve TiO2photocatalytic activity and extend the light response range, the samples of Co-doped mesoporous TiO2and Fe-doped mesoporous TiO2photocatalyst are prepared by an ionic liquid modified sol-gel method using tetrabutyl titanate as titanium source, Co(NO3)2-6H2O as cobalt source, FeC2O4-2H2O and Fe(NO3)3-9H2O as iron source. The mesoporous Co/TiO2and Fe/TiO2photocatalytic materials have large surface areas, high thermal stability and visible light avtivity. The samples are characterized by TG-DSC, XRD, XPS, BET, UV-Vis and TEM, respectively. TG-DSC and XRD results showes that the samples exhibite high thermal stability, and the samples calcined at650℃indicated well-crystallized anatase structure. XPS spectra prove the CO3O4structure of Co in Co-doped mesoporous samples, and Fe3-in the TiO2surface. Large specific surface area was shown from the BET analysis, and the largest specific surface areas are obtained when the Co-doping amount is0.3%and Fe-doping amount is0.1%. UV-Vis DRS spectra showed that all of the samples exhibited obvious absorption in the visible light range. Photocatalytic activity of Co/TiO2and Fe/TiO2samples was evaluated by photodegradation of MB under visible light (λ>420nm). Co-doped mesoporous TiO2and Fe-doped mesoporous TiO2exhibite high photocatalytic activity for MB oxidation, and the0.3%Co/TiO2and0.1%Fe/TiO2sample showes the highest visible light activity. Compare to Fe-doped TiO2, photocatalytic activity of Co/TiO2could be improved further by Co-doping.The paper research the structure and visible light catalytic mechanism of Co-doped TiO2and Fe-doped TiO2photocatalytic material is investigated combining characterization technique of XPS、UV-Vis、BET with the visible light photocatalytic reaction results of Co/TiO2and Fe/TiO2. The results showes that doping Co and Fe ions could changing the spectral absorption range and enhance the solar energy utilization of TiO2. Co, Fe-doped less Co2+and Fe3+into the TiO2lattice could replace Ti4+of TiO2which can be decrease the oxygen content of TiO2. Energy level and oxygen vacancy can be easily introduced to improve the TiO2catalytic activity and utility rate of luminous energy effectively. With the doping amount increasing, some Co, Fe may form the Co3O4and Fe2O3attache on the surface of the samples, witch lead to the samples specific surface area decrease.