Study On Preparation Of Pt/TiO₂ As Photocatalyst Driven By Visible Light And Activity For Degradation Of Phenol

The photocatalytic oxidation technique of TiO₂ has been paid more andmore attention for the advantage of less energy cost, mild reaction condition,easy operation and less secondary pollution. However TiO₂ may showphotocatalytic activity only by irradiation of ultra violet(UV)light for its wideband gap(Eg=3.2eV). But the proportion of UV light to the sun light is very small.Furthermore, UV light decays so fast in water that the availability of solar energybecomes very less. In addition, easy recombination of photo-induced electronsand holes makes the efficiency of photoquantum lower. Those unfavorablefactors have the photocatalytic oxidation technique of TiO₂ limited in practice.Considering the problems above, the scheme that TiO₂ photocatalyst isdoped with platinum ions is presented after the photocatalytic mechanism andelectronic structure character of TiO₂ are analyzed. And Pt doped TiO₂nanoparticles as well as its film photoeatalysts are prepared by sol-gel method.Besides, photocatalytic activity (PCA) is also studied by degrading phenolsolution.In addition, TG-DTA, XRD, TEM, XPS and UV-VIS analysis are made forprepared photocatalysts. The effects of calcining temperature and content ofplatinum ions on crystal structure, crystal size and property of modified TiO₂nanoparticles are investigated. Besides, the effects of calcining temperature andcontent of platinum ions on the photocatalytic activity are also studied bydecomposing phenol. Meanwhile, inactivation and reactivation of photocatalyst are also discussed in the paper.The study shows that the introduction of Pt ions can improve the phasetransformation process of TiO₂ from amorphous phase to anatase and fromanatase to rutile. Two main factors that affect crystal structure, crystalcomposition and crystal grain size of modified TiO₂ nanoparticles are sinteringtemperature and platinum ions content. The responsive area of platinum ionsmodified TiO₂ samples to light is enlarged to visible light area, and theabsorption strength becomes bigger with the increase of platinum ions content.The appearance of prepared TiO₂ nanoparticles looks like balls and the particlesize is even.The state of Pt ions appears complicated in the samples. Pt ions appear asPtCl₄ in Pt doped TiO₂ sample calcined at 300℃,while they appear as PtCl₂ andPrO2 in the sample calcined at 400℃and as PtO₂ in the sample calcined at 500℃.The result of photocatalytic degradation for phenol shows the photocatalyticactivity of 3 mol% Pt doped TiO₂ sample calcined at 300℃is the highest of Ptdoped TiO₂ photocatalysts. The result of photocatalytic degradation for phenolwith Pt/TiO₂/ITO film shows that the times of coating layer have important effecton photocatalytic activity of the prepared catalysts.In the experiment condition,Pt/TiO₂/ITO film catalyst with 3 coating layers shows the highest photocatalyticactivity of the samples prepared.