| As a new energy resource,More and more about the hydrogen energy has been attracted.The hydrogen production from water splitting by sunlight has been known as an economic and clean technology and a process with prominent prospect for application.The progress in studies about water photocatalytic splitting was reviewed involving photocatalysts species,photoreaction system and effective visible light harvest for water photolysis.Because of the low rate of oxygen evolution and difficult to match the rate of hydrogen evolution in photocatalytic splitting water system,modified rutile TiO2 with oxygen vacancies was synthesised using donor metal doped,rare-earth doped and improving preparation method.With Fe3+ as electron acceptor under UV irradiation and visible radiation,the photocatalytic activities for oxygen evolution using modified rutile TiO2 with oxygen vacancies were studied.Work has been done as follows:1.TiO2 was prepared by sol-gel method and low-temperature ultrasonical hydrolysis method.The influence of preparation method on the activity of TiO2 splitting water for oxygen evolution was studied.The results show that the photoactivity of anatase TiO2 was poorer than that of rutile TiO2.Under the ultraviolet irradiation,when the initial concentration of Fe3+ was 8.0 mmol·L-1 and the pH value of the solution was 2.0,the maximun speed of O2 evolution for rutile TiO2 prepared by hydrolysis method was 93.2μmol·L-1·h-1.The oxygen evolution ratio of rutile TiO2 prepared by hydrolysis method is 10.6%higher than that of rutile TiO2 prepared by a sol-gel method.The oxygen production rate under ultraviolet irradiation and visible light irradiation was 113.8μmol·L-1·h-1 and 62.1μmol·L-1·h-1 when rutile TiO2 with oxygen vacancies prepared by ultrasonical hydrolysis method and calcined at 700℃under Ar atmosphere,respectively.Ultrasonical treatment can improve the photocatalytic activity of TiO2.2.The water photocatalytic splitting activity of rutile TiO2 prepared by hydrolysis method under air,Ar and H2 atmosphere The results show that rutile TiO2 has higher photocatalytic activity for water splitting prepared under Ar and H2 atmosphere than that prepared under air atmosphere.The oxygen production rates under ultraviolet irradiation were 106.6 and 103.2μmol·L-1·h-1 when TiO2 was prepared under Ar and H2 atmosphere as photocatalyst,respectively.And the oxygen production ratios compared to the rate of futile TiO2 prepared under air atmosphere(93.2μmol·L-1·h-1).The oxygen production rates under visible light irradiation were 51.6 and 33.8μmol·L-1·h-1 when TiO2 was prepared under Ar and H2 atmosphere as photocatalyst,respectively,compared to the rate of futile TiO2 prepared under air atmosphere(18.8μmol·L-1·h-1).3.The effects of rare earth metal(2.0%)La,Nd,Sm,Eu,Gd,Er, Yb doping rutile TiO2 on the photocatalytic activity of splitting water with oxygen evolution were investigated systematically.The results shows that under UV-light irradiation,Yb,Eu or Er doping rutile TiO2 can improve the photocatalytic activity of rutile TiO2,and La,Sm,Nd doping can not infuence the photocatalytic activity of rutile TiO2 obviously,and Gd rutile TiO2 doping can reduce the photocatalytic activity of rutile TiO2.Under the visible-light irradiation only Yb and Eu rutile TiO2 doping can improve the photocatalytic activity of rutile TiO2. The rare earth metal doping rutile TiO2 can cause oxygen vacancies,which can influence the photocatalytic activity of rutile TiO2.4.The donor metals(V,Nb,Ta and W) were firstly used to modify rutile TiO2 with oxygen vacancies.The results show that TiO2 doped with V,Nb,Ta and W exhibites higher photocatalytic activity of splitting water for oxygen evolution.TiO2 doped with V and W exhibites the highest photocatalytic activity of oxygen evolution.When the photocatalytic activity of rutile TiO2 splitting water for oxygen evolution can be enhanced,there was an optimum doping concentration.The optimum doping concentration of V,Nb,Ta and W were 1.0～2.0%,1.0%,1.0%, 2.0%,respectively.The oxygen production rate of rutile TiO2 with oxygen vacancies doped with V,Nb,Ta and W under ultraviolet irradiation were 160.0μmol·L-1·h-1,138.1μmol·L-1·h-1,130.4μmol·L-1·h-1 and 148.8μmol·L-1·h-1;and the oxygen production rate of rutile TiO2 with oxygen vacancies were 105.2μmol·L-1·h-1,80.4μmol·L-1·h-1, 69.6μmol·L-1·h-1 and 102.9μmol·L-1·h-1,respectively.The trend of photocatalytic activity of V,Nb,Ta and W-doped TiO2 splitting water for oxygen evolution was consistent with its photoluminescence strength. The oxygen production rates of rutile TiO2 doped with donor elements V, Nb,and W under visible light irradiation were higher than that reported in the literatures.5.Rutile TiO2 doped with the donor metals(V,Nb,Ta and W) have been analyzed by the first principles calculations with the density functional theory.The results show that:(1)The band gap of futile TiO2 was 1.9eV.(2)The fermi energy level of rutile TiO2 moved to the conduction bands when doping content of V,Nb,Ta and W was elevated.The band gap decreased,the surface barrier raised,space charge district narrowed.The Eg of rutile TiO2 was reduced and photoproduced electrons and holes were easily excited with lower energy compare with the undoped rutile TiO2,which was advantage to the excitation of low-frequency photons and the separation of photoproduced electrons and holes.New levels between the conduction and valence bands occured when TiO2 was doped with V and W.Thus,the doped TiO2 can easily excited photoproduced charges.The photocatalytic effects of oxygen evolution as TiO2 doped with V and W were better than that doped with Nb and Ta.(3)The calculation results indicate that the photocatalytic activity of splitting water for oxygen evolution can improved after TiO2 was doped with V,Nb,Ta and W,respectiely.
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