Study On The Controlled Preparation And Photocatalytic Properties Of Titanium Dioxide Photocatalyst

Solar water splitting for hydrogen production is a challenging research topic. TiO₂is considered to be the best photocatalyst due to its high efficiency, non-toxicity,low-cost and stability, and has been widely studied in the field of photocatalysis. In thisthesis, TiO₂photocatalysts with different morphologies have been synthesized bychanging the titanium source and preparation conditions. TiO₂photocatalysts werecharacterized by SEM, EDS, XRD and XPS analysis. The photocatalytic performancefor hydrogen evolution from water splitting was tested. Moreover, the influence factorson photocatalytic hydrogen production were studied, such as calcination temperature,morphology, and surface modification. The specific research contents and results aresummarized as follows:1. TiO₂microspheres were synthesized by hydrothermal reaction using Ti（OBu）4as the precursor. SEM analysis shows that the TiO₂microspheres have smooth surfaceand uniform size, and the diameter of TiO₂microspheres is around5-10μm. In order toenhance the efficiency of water splitting by the TiO₂microspheres, the synthesizedsamples were treated by loading noble metal Pt and calcination. The result shows thatthe photocatalytic activity of the TiO₂microspheres is remarkably enhanced by loadingPt. The optimal Pt loading is1.2wt%. The hydrogen production rate of1.2wt%Pt/TiO₂microspheres is2.585mmol/g/h. The photocatalytic stability of the Pt/TiO₂microspheres was estimated. The experimental results demonstrate that the Pt/TiO₂microspheres exhibit a stable photocatalytic activity. In addition, the effect ofcalcination temperature on photocatalytic activity of the TiO₂microspheres was alsostudied. The TiO₂microspheres calcined at500℃have the highest photocatalyticactivity due to the improvement of crystallinity and the synergy of anatase and rutilephase.2. TiO₂nanosheets with exposed {001} faces were fabricated by a simplehydrothermal route in a Ti（OBu）4and HF mixed solution. The analysis of SEM andTEM shows that TiO₂nanosheets is rectangle, about50-60nm in length, and about6-10nm in thickness. To enhance the photocatalytic activity of TiO₂nanosheets under visible light, Au-modified TiO₂nanosheets were prepared by the impregnation-reductionmethod. DRS analysis shows that Au loaded TiO₂nanosheets appear a wide absorptionband in the visible region. The effect of Pt loading on the rates of photocatalytichydrogen production was investigated. The result shows that the0.2wt%Au/TiO₂nanosheets have highter hydrogen production rate, the hydrogen production rate is61.6μmol/g/h. The photocatalytic activity of photocatalyst was improved significantly.3. TiO₂flower-like microspheres were synthesized by hydrothermal reaction usingTi foil as the precursor. We explored the effects of the reaction temperature, reactiontime, and hydrofluoric acid concentration on the TiO₂morphology. SEM analysis showsthat the low temperature and the short reaction time are favorable to the formation of theflower-like microspheres. The structure of the flower-like microspheres is destroyedwith the increase of temperature and time. In addition, the photocatalytic hydrogenevolution from water splitting of TiO₂flower-like microspheres prepared at differenttemperature was tested, The result shows that the hydrogen production rate firstincreases and then decreases with increasing temperature. The hydrogen production rateof TiO₂flower-like microspheres prepared at140℃is0.2599mmol/m²/h, which isattributed to the combined action of the morphology and crystallinity.