Investigation On Performance Of Titanium Dioxide Photocatalysts For Hydrogen Production Via Water Splitting

Environmental pollutions and energy crisis are the two problems confronted with the world nowadays.Photocatalytic hydrogen production has been widely regarded as a promising solution towards the two problems.Nanostructured TiO₂ is the most promising material used for cost-efficient and environmental friendly solar hydrogen production due to its excellent advantages of favorable electronic band structure,high photo-chemical stability,large specific surface area,and abundant availability.In this thesis,TiO₂ mixed crystal nanocomposites were prepared by hydrothermal method.The effects of preparation conditions on mixed phase synthesizing,morphology,microstructure,luminescence and hydrogen production with Pt were studied.The main contents of this thesis are as follows:（1）Effect of twice-hydrothermal-process on microstructure and hydrogen production of mixed TiO₂.Anatase and rutile TiO₂ nano-powder has been synthesized by hydrothermal method with different acidity and temperature using tetrabutyl titanate（TBOT）,hydrochloric acid and sulfuric acid as the source materials.A twice-hydrothermal-process has been adopted in the preparation of anatase or rutile powder,influence of the twice hydrothermal process on the photocatalytic hydrogen production performance of TiO₂ was investigated.Hydrogen production performance of the synthesized TiO₂ photocatalyst was characterized via water splitting.The results show that,after experienced the twice hydrothermal process,the H₂production rate of anatase has been improved about five times comparing to that of the first process,while the H₂ production rate of rutile is reduced to 2/5 of the first process.The results offer new insight of producing high efficient photocatalyst for water splitting by the simple twice hydrothermal process to anatase TiO₂ photocatalyst.（2）Effect of once-hydrothermal-process on microstructure and hydrogen production of mixed TiO₂.TiO₂ based heterojunction photocatalyst,which is consisted of rutile nanorods and anatase nanoparticles,was systematically studied by controlling the HCl concentration in hydrothermal process.With the help of loaded Pt,an interesting two-peak feature was observed in the HCl-dependent H₂ production efficiency.The peak values are 54.3 mmolh^-1g^-1and 74.4 mmolh^-1g^-1corresponding to 83.9%and 12%anatase phase,respectively.A detailed analysis based on the microstructure and photoluminescence（PL）spectra indicated that the two-peak feature is directly linked to the HCl-controlled interface area.Moreover,an unexpected zero interface area was revealed at an intermediate HCl concentration.In terms of homogeneous and heterogeneous nucleations,an interface growth mechanism was proposed to clarify its HCl-sensitive character.This work provided a route to enhance the photocatalytic activity in TiO₂ based photocatalyst via increasing the interface area.