Research Of Carbon Doped Mesoporous TiO₂ And Its Visible Light Photocatalytic Activity

TiO₂ is a promising photocatalytic material which has been widely used in various fields such as water-splitting for hydrogen production and purification of air and water,due to its excellent chemical stability,low-cost and nontoxicity.However,its application is restricted since it has a wide band gap?3.2 eV?.It only shows photocatalytic activities under ultraviolet irradiation.Therefore,developing visible light responsive TiO₂ photocatalysts has become a hot research topic.In this thesis,TiO₂ photocatalysts with visible light photocatalytic activity were prepared by carbon doping.The TiO₂ grain size was effectively controlled by adjusting the calcination temperature.The mesoporous structure increases the specific surface areas and the photocatalytic active sites,thereby the photocatalytic activity was enhanced.The main results are summarized as follows:?1?Carbon doped mesoporous anatase TiO₂ powders?CT?were prepared by hydrolyzing tetrabutyl titanate in ammonia,without adding any external carbon source,followed by calcinating at different temperatures.The grain size,surface morphology,mesoporous structure,light responsive range and visible light catalytic properties were investigated as a function of the calcination temperature.The existential form of carbon was also investigated.The optimal calcination temperature was found to be 350?.The corresponding sample was designated as CT-350.The grain size of CT-350 is as small as 10.8 nm,which is conducive to the transport and diffusion of photo-induced carriers and decrease of the recombination rate of photoinduced electron-hole pairs.The number of photocatalytic active sites increases due to a higher specific surface area(281.3 m²g^-1).The substitution of C at Ti site in TiO₂ lattice narrows the band gap to 2.8 eV and therefore extends light absorption to visible light range.CT-350 shows superior photocatalytic activity under visible light irradiation with a wavelength>420 nm in the degradation of rhodamine B?RhB?,which is fourfold higher than that of P25,and excellent photocatalytic stability as well.?2?Mesoporous carbon doped anatase TiO₂ microspheres?MPCTMS?were prepared by a modified hydrolysis method.The grain size,surface morphology,mesoporous structure,light responsive range and visible light catalytic properties of MPCTMS were investigated as a function of the calcination temperature.The existential form of carbon was also investigated.The microsphere size is about 500 nm.The optimal calcination temperature was found to be350?.The corresponding sample was designated as MPCTMS-350.The grain size of MPCTMS-350 is as small as 8.1 nm,which was conducive to the transport and diffusion of photo-induced carriers and decrease of the recombination rate of photoinduced electron-hole pairs.The number of photocatalytic active sites increases due to a higher specific surface area(269.8 m²g^-1).The substitution of C at O site in TiO₂ lattice narrows the band gap to 2.75 eV and extends light absorption to visible light range.Compared with CT-350,MPCTMS-350has smaller grain size and narrower band gap and therefore shows better photocatalytic stability and higher photocatalytic activity under visible light irradiation,which is sevenfold higher than that of P25.