Simultaneous Synthesis,Photocatalytic Activity and Characterization of Biomass Multi-elements Co-doped TiO2

Author:Zhao Lin

Supervisor:diao yong


Degree Year:2019





As a photocatalyst,titanium dioxide can directly utilize solar energy.It can not only catalyze the decomposition of water to generate hydrogen,but also decontaminate by catalytic oxidation.Because of its stability,non-toxicity and low cost,it is called the most promising semiconductor photocatalyst.Therefore,the research and development of titanium dioxide has been a hot spot in the field of photocatalysis.In this paper,natural biomass such as starch,sugar and oil were used as doping elements.A series of C,N,P and other multi doped TiO2 photocatalyst,which has visible-light photocatalytic activity,were prepared by modified sol-gel method.The results of this paper can provide a useful direction for the strategy of modification of titanium dioxide,lay a theoretical and technical foundation for biomass modification of titanium dioxide,and expand the practical application of titanium dioxide in the field of photocatalysis.1.Firstly,the defect formation energy and band structure of C and N co-doped titanium dioxide were calculated by first principles,and compared with the experimental results.The defect formation energy of C and N respectively substituting for Ti and O doping is lower than that of C and N both substituting for O doping.When C and N are co-doped,it is easier to replace Ti and O respectively.Compared with pure anatase TiO2,C-doped,N-doped and C,N co-doped can all reduce the band gap of TiO2,but the band gap narrowing of multi-elements co-doped TiO2 is more than solo-element-doped TiO2.2.Using tea oil as doping elements source,a series of composite TiO2 photocatalyst were prepared by sol-gel method,and the preparation process was optimized.By X-ray diffraction(XRD),UV-Vis diffuse reflectance spectroscopy(UV-Vis),PL(fluorescence spectroscopy),field emission scanning electron microscopy(FESEM),electrochemistry means analysis and elemental analysis,the composite catalyst prepared were characterized.The results show that there are rutile and anatase phases in the samples,and they have honeycomb-like porous structure;after tea oil modification,with the increase of photocurrent density,the recombination efficiency of photogenerated carriers decreases;under visible light irradiation,using tea oil modified TiO2 as photocatalyst,the degradation ratio of methylene blue is up to 92.6% in 2 h.3.Using soluble starch as doping elements source,a series of composite TiO2photocatalyst were prepared by sol-gel method.The samples were analyzed by various characterization methods.Compared with the pure TiO2,in the synergistic effects of multi-element,the composite catalyst of soluble starch doped TiO2 posses higher specific surface area,wider scope of visible light absorption.The optimum preparation process of composite materials is that:the amount of soluble starch added is 6 g,calcination temperature is 400℃ and calcination time is 2 h.After 80 min,the degradation ratio of methylene blue in the soluble starch modified TiO2 can reach as high as 98%.4.Using navel orange extract as doping elements source,the multi-elements co-doped TiO2 was synthesized simultaneously by ultrasonic irradiation assisted sol-gel method,and the preparation process was optimized.The characterization results showed,multiple elements,C,N,P,Cl and K,were doped in the composite TiO2;Compared with pure TiO2,the band gap of the composite catalyst was narrowed by 0.21eV,and possessed more surface hydroxyl radical and active sites,lower recombination rate of photo-generated carriers,higher crystallinity and higher specific surface area.After 120 min,the degradation ratio of methylene blue in the modified TiO2 can reach as high as 98%..5.A series of Japonica rice extract modified composite nano TiO2 were prepared by sol-gel method,and the preparation process was optimized.The experimental results show that the composite catalyst realizes the simultaneous doping of C,N,S,P,K and other elements.The reaction rate constants of composite titanium dioxide and pure titanium dioxide are 0.4990 h-1 and 0.0305 h-1,respectively.Compared with pure titanium dioxide,the specific surface area of composite titanium dioxide increases,the crystallinity increases,the recombination rate of photogenerated carriers decreases,the absorption sideband redshifts,and the band gap narrows by 0.09 eV.