| Metal ions and non-metallic elements single doped and co-doped nano-particle TiO2catalysts were successfully synthesized by alcohol-thermal method in this work. Metal ions (Fe, Ni, and Ag) and non-metal elements (N) were used to dope TiO2respectively in order to improve its properties. The prepared TiO2nano-particles were applied to the field of hydrogen (H2) evolution by water splitting under light irradiation, and then, the property of hydrogen evolution catalytic activity was also evaluated. Finally, the mechanism and reaction kinetics of photo-catalytic H2evolution from water were also preliminary studied.The prepared TiO2nano-particles were characterized by X-ray powder diffraction (XRD), N2adsorption and desorption (BET method), UV-visible absorption spectroscopy (UV-vis), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to study their structures, properties and morphology. The results showed that pure TiO2prepared by alcohol-thermal method using ethanol as solvent was pure anatase, its average particles size was about22nm and it owned a uniform particle size.In this work, metal ions and non-metallic elements doped TiO2nano-particles were successfully prepared through alcohol-thermal method. The results showed that single doped and co-doped TiO2had a large specific surface area with pure anatase. And then, co-doped TiO2owned a larger surface area and a smaller particle size than that of single doped TiO2, co-doping can further suppress TiO2crystal growth seriously than that of single doping. Compared with pure anatase TiO2, the light absorption edges of doped TiO2moved remarkably with a red shift from UV range to visible range. The optimal single doping molar of N, Fe, Ni and Ag to Ti was3.5%,4.0%,4.5%and4.5%, respectively, and the recombination of photo-electrons and holes was greatly suppressed by doping. At last, co-doped TiO2can further improve their light absorption edges to visible light region than that of single doping, and the absorption intensity of visible light was also greatly enhanced.4.5%Fe-4.5%Ag/TiO2showed best absorption of light among those samples prepared, its light absorption edge shifted remarkably to610nm. In contrast to single element doped TiO2, the recombination of the excited electrons and holes in those co-doped samples was also further restrained, and the efficiency of separation between electrons and holes was improved.Under UV light irradiation, their (TiO2) photo-catalytic activities were estimated through H2evolution by water splitting. The average rate of H2evolution was up to399.96μmol·gcat-1·h-1(the reaction time was6h), their oders of rates of H2evolution were as following:4.5%Fe-4.5%Ag/TiO2>5.0%Fe-4.0%Ni/TiO2>5.0%N-2.0%Fe/TiO2>3.5%N-4.5%Ni/TiO2>4.5%N-4.5%Ag/TiO2>5.0%Ni-4.0%Ag/TiO2>4.5%Ni/TiO2>4.0%Fe/TiO2>3.5%N/TiO2>4.5%Ag/TiO2>TiO2. Fe and Ag co-doped showed highest rate of H2evolution under UV light irradiation.Their visible light (TiO2) photo-catalytic activities were also estimated through H2evolution by water splitting (λ>400nm). The average rate of H2evolution was up to515.74μmol·gcat-1·h-1(the reaction time was6h), their orders of rates of H2evolution were as following:4.5%Fe-4.5%Ag/TiO2>4.5%N-4.5%Ag/TiO2>5.0%Ni-4.0%Ag/TiO2>5.0%Fe-4.0%Ni/TiO2>5.0%N-2.0%Fe/TiO2>3.5%N-4.5%Ni/TiO2>4.5%Ag/TiO2>4.0%Fe/TiO2>4.5%Ni/TiO2>3.5%N/TiO2>TiO2. Fe and Ag co-doped showed highest rate of H2evolution under visible light irradiation, which was a good kind of catalyst of H2evolution by water splitting.In this work, the mechanism and reaction kinetics of photo-catalytic H2evolution from water were also preliminary studied finally. In the initial photo-reaction of about70min, the rate of absorption light on TiO2catalysts was almost equivalent to the rate of H2evolution by water splitting, and which determined the rate of H2evolution. After reaction of about70min, the adsorption-desorption balance of various kinds of substances including reactants, intermediates and products on catalysts determined the rate of H2evolution by water splitting, in other words, the surface properties of catalysts could decide the rate of H2evolution. |
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