Synthesis And Properties Of Multielement Photocatalytic Materials Based On Titanium

As a important semiconductor material, TiO₂can treat lots of environmentalpollutants under solar light, it has attracted many researchers’ attention for its excellentperformance such as low cost, nontoxic and no secondary pollution. However, TiO₂alsohas some defects such as its large band gap, low light utilization rate and highrecombination probability of photo-generated carriers. Ions doping have been reportedto be one of the effective means for enhancing the photocatalytic activity of TiO₂.In order to solve the problems, single-doping and co-doping were used in theexperiment to modify TiO₂to enhance its photoactivity in the UV light. Powder X–raydiffraction （XRD）, scanning electron microscope （SEM）, FT–IR, and N₂adsorption-desorption were employed to analyze morphology and structure of thematerials. Photocatalytic degradation of methyl orange under UV-light irradiation on thematerials was also examined. The main work is composed of four parts:Using tetrabutyl orthotitanate （TBOT） as Ti source, In （NO₃）₃·4.5H₂O as In source,In doped TiO₂nano-material was prepared by sol-gel method. The results indicate thatall the samples presented anatase TiO₂phase, In ions mainly occupy the sites of Ti incrystal lattice by isomorphous replacement, existing in the form of In_xTi_1-xO₂.In dopinginhabited growth of TiO₂crystal, increasing the special surface area of the TiO₂.Withincreasing calcination temperature, TiO₂crystalline and average pore size increasedgradually, while the special surface area decreased. The largest special surface area was94.4m²/g for the3%In-TiO₂sample calcinated at400oC. Meanwhile, the sample alsoperformed the optimal photocatalytic degradation activity, so that methyl orangedegradation rate was compeletly discolored after70min of UV-light irradiation, whilemethyl orange degradation rate was62.3%with TiO₂.Using CTAB as a template, effect of different CTAB extents and calcinationtemperature on the structure and activity of In-TiO₂photocatalyst was examined. Theresults indicate that the addition of CTAB enhances the crystallization and dispersion ofIn-TiO₂, increasing crystallinity sizes and special surface area. Significantly, theaddition of CTAB led to the lattice expansion of TiO₂. After surfactant was removed byproper calcination temperature, In-doped sample exhibited larger surface area and less pore size. After60min of UV-light irradiation, methyl orange degradation rate was91.8%for the3%In-TiO₂sample, which was prepared with CTAB concentration of0.12mol/L calcinated at500oC. The photocatalytic activity was mainly affected by thespecific surface area and lattice expansion.Using tetrabutyl orthotitanate （TBOT） as Ti source, In （NO₃）₃·4.5H₂O as In source,AlCl₃·6H₂O as Al source, In and Al co-doped TiO₂nano-material was firstly prepared bysol-gel method. The results indicate that all the samples presented anatase TiO₂phase,Al doping inhabited growth of TiO₂crystal, increasing the special surface area of theIn-TiO₂.With increasing calcination temperature, TiO₂crystalline and average pore sizeincreased gradually, while the special surface area decreased. The largest special surfacearea was108.9m²/g for the0.5%Al-3%In-TiO₂sample calcinated at400oC. Al ionsmainly substituteTi⁴⁺in the TiO₂lattice to cause the distortion of lattice,and increasethe surface hydroxyl group, restraining the recombination of photo-excited chargecarriers. Meanwhile, the0.5%Al-3%In-TiO₂sample also performed the optimalphotocatalytic degradation activity, so that methyl orange was compeletly discoloredafter40min of UV-light irradiation.Using tetrabutyl orthotitanate （TBOT） as Ti source, In （NO₃）₃·4.5H₂O as In source,LaCl₃·9H₂O as La source, In and La co-doped TiO₂photocatalyst was firstly synthesizedusing sol-gel method. The results indicate that all the samples were in anatase TiO₂phase, La ions mainly have been incorporated into the TiO₂lattice to result in thedistortion of lattice, promoting the sapretion of the eclecron-hole pairs. La dopingembarrassed TiO₂crystal growth, resulting in the increase of the special surface area.With increasing calcination temperature, TiO₂crystalline size increased gradually,resulting in the partical agglomeration and the decrease of the special surface area. Thespecial surface area was129.8m²/g for the0.3%La-3%In-TiO₂sample calcinated at400oC. Meanwhile, the sample also performed the optimal photocatalytic degradationactivity, so that methyl orange was compeletly discolored after40min of UV-lightirradiation. The UV-Vis analysis result showed that the photocatalytic degradationprocess of MO changed after La doping.