Efficient Hydrogen Production By Modified TiO₂ Photocatalysis

Photocatalytic hydrogen production by water splitting is an important branch of photocatalytic researches. In recent years, this issue is made significant progesses through a series of deep studies. In this thesis, the traditional TiO2 is modified by loading metallic Pt and compounding with Ag2S. The photocatalytic activities of modified catalysts were tested based on the performances of hydrogen production.In the first part of this thesis, the H2PtCl6·6H2O was used as the Pt source and commercial P25 as the Ti source to prepare Pt/TiO2 by four methods, including three traditional ways called impregnation, precipitation, photodeposition and one improved way called precipitate-photodeposition. The photocatalytic activities of the catalysts prepared by these four methods were compared by the performances of hydrogen productions. All the samples were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS) and transmission electron microscopy (TEM). The microstructures of Pt/TiO2 prepared by these four methods were analyzed in details by characterizations. The results show that when added the same amounts of H2PtCl6·6H2O at the beginning of the preparation, Pt/TiO2 catcalysts prepared by precipitate-photodeposition have the highest loading amount and best dispersion of metallic Pt. In addtions, the other reaction variables in this experiment were optimized. The results show that the highest hydrogen production was 1.6 mmol/h under the optimum preparation conditions, which is twice than that of Pt/TiO2 prepared by traditional photodepositon at the same amounts of H2PtCl6-6H2OIn the second part of this thesis, the hydrogen production was improved by constructing a new composite semiconductor material, which is composed of Ag2S and TiO2. Ag2S/TiO2 was prepared by complexes-deposition. Diethyldithiocarbamate, AgDTC, is used as Ag source and ethylenediamine as complexes and acetone as the solvent. The preparation can effectively avoid the hydrolyzing of traditional Ag salt in aqueous solutions and make Ag2S nanoparticles disperse on P25 uniformly by AgDTC complexing with ethylenediamine smoothly. The influences of factors of the preparations such as the proportions of AgDTC and P25, the amounts of ethylenediamine and prepared temperatures et al were investigated to optimize the preparation of Ag2S/TiO2. All the samples were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). The results show that Ag2S/TiO2 exhibits the highest hydrogen productions when the n (AgDTC):n (TiO2)=1:25 and complex with 10 mL ethylenediamine at 60℃for 8 h.