Synthesis And Photocatalytic Properties Of Multielement Doped Porous TiO₂

TiO₂was considered as an important semiconducting oxide photocatalyst due to itshighly efficient, chemically stable, nontoxic, relatively inexpensive and long service life.Researchers were attracted by advantages of TiO₂. However, TiO₂also has somedefects such as its large band gap, and recombination rates of photogenerated electronsand holes are very quickly. To overcome the shortcomings, doping control technologywas considered as one of the effective means. At present, non-metallic doping havealready been the hot spot in the study field of doping control. Non-metallic elementboron was mainly used in this paper to improve TiO₂photocatalysis performance.In this paper, B-TiO₂, Al-B-TiO₂and La-B-TiO₂were prepared via sol-gel methodand solvothermal method. The effects of boron doping content and calcinationtemperature on the structural properties of B-TiO₂were investigated by powder X-raydiffraction （XRD）, scanning electron microscope （SEM）, Raman spectrum, FT-IR,X-ray photoelectron spectrum （XPS） and N2-adsorption and desorption, andphotocatalytic performance of B-TiO₂was evaluated by degradation of methyl orange（MO） solution. The effects of Al-B and La-B co-doping on pore size distribution andphotocatalytic performance of TiO₂were preliminary analyzed by N2-adsorption anddesorption and degradation of MO solution, respectively.There are some conclusions as follows.1) B-TiO₂was prepared by sol-gel methodand solvothermal method, respectively. The optimal boron doping content of B-TiO₂prepared by both methods was as same as3%. Boron doping inhibited growth of TiO₂crystal and had no apparent impact on surface morphology of TiO₂particles. B-TiO₂prepared via different methods had different crystallite size, BET surface area and poresize distribution. Different preparation methods resuled in differnet forms of boron existing in TiO₂. In B-TiO₂prepared by sol-gel method, the doped boron mainlyoccupied the internal space of TiO₂crystalline structure existing in the form of B-O-Tistructure. In B-TiO₂prepared by solvothermal method, the doped boron mainlyincorporated into the TiO₂lattice through occupying O sites as O–Ti–B form. Whencomparing photocatalytic degradation efficiency of methyl orange, B-TiO₂prepared bysolvotheral method was better than B-TiO₂made by sol-gel method.2) B-TiO₂preparedby both methods had same optimal calcining temperature at400°C. With risingcalcination temperature, crystallite sizes and average pore sizes of B-TiO₂increased, butBET surface area decreased. Calcination temperatures had no apparent impact onsurface morphology of B-TiO₂. However, Calcination temperature affected the boronexisting state so that the B-O-Ti structure in B-TiO₂prepared by sol-gel was reducedwith the increases of calcination temperature.3) Al-B-TiO₂and La-B-TiO₂wereprepared by sol-gel and solvothermal method. MO photocatalytic degradation on bothAl-B-TiO₂and La-B-TiO₂were lower than that of B-TiO₂, but adsorption of Al-B-TiO₂and La-B-TiO₂were higher than that of B-TiO₂.