Preperation And Properties Of V And Co Co-doped Nano-TiO₂ Semiconductor

Environmental pollution and destruction,as well as the severe shortage of clean and natural energy,are serious challenges facing the world today.Studying green,sustainable new environmental and energy materials and technologies is one ofthe most important issues today.Titanium dioxide(TiO2)is favored for its important applications in environmental pollution control and clean energy because of its chemical stability,non-toxicity,high reactivity and low price.However,due to its wide forbidden band width(Eg = 3.2 eV),it can only absorb ultraviolet light with a wavelength less than 387 nm.Therefore,the utilization efficiency of sunlight is very low,and the photogenerated electron-hole pairs generated by TiO2 under illumination are easily recombined,which reduces the light quantum efficiency,which leads to the limitation of practical application.Researchers have found through a large number of studies that the doping modification of TiO2 by metal ions can broaden its response to visible light and reduce the recombination rate of its photogenerated electron-hole pairs.Therefore,metal ion doping has become a hot spot in the research field of TiO2 modification and its properties.In this thesis,nano-TiO2 semiconductor was used as the main research object.The transition metal ions V and Co were used for doping modification.The preparation and synthesis of nano-TiO2 semiconductor were completed by sol-gel method.The(V,Co)-TiO2 nano-semiconductor photocatalysts have excellent visible light degradation properties of dye,and its use as a porous layer of perovskite solar cell can improve photoelectric conversion efficiency.Based on the experimental results,the morphology,spectral properties and catalytic mechanism of(V,Co)-TiO2 nano-semiconductor were investigated.The specific contents and results of this work are listed as below:1.Preparation and characterization of V,Co co-doped nano-TiO2 semiconductor.Using distilled water as solvent,NH4VO5,Co(NO3)3·6H2O,as a source of transition metal elements,(V,Co)-TiO2 nano-semiconductor was prepared by solvent-gel method.The crystal structure,morphology,specific surface area and spectral characteristics of pore structures were obtained by XRD,TEM,XPS BET UV-vis and PL.According to the orthogonal experimental results,V-doped TiO2 with a molar ratio of n(V):n(Ti)=0.3%,Co-doped TiO2 with a molar ratio of n(Co):n(Ti)= 0.1%,and V and Co co-doped TiO2 with a molar ratio of n(V):n(Ti)= 0.3%and n(Co):n(Ti)= 0.1%prepared at pH 1.5 and sintered at 500 ? show the best photocatalytic activity,the percentage of degradation is 87.91%,78.75%.and 92.12%,respectively.And V and Co co-doped TiO2 with a molar ratio of n(V):n(Ti)= 0.3%and n(Co):n(Ti)= 0.1%showed the best photoelectric conversion efficiency2.The experimental results show that the TiO2 nano-semiconductor photocatalyst prepared under the optimal preparation conditions is anatase and rutile mixed crystal nano-TiO2.Due to the incorporation of V and Co elements,the absorption range is red-shifted from 405 1m to 475 nm compared with pure TiO2.and the fluorescence intensity of the(V,Co)-TiO2 photocatalyst is significantly reduced.Under the irradiation of ordinary fluorescent lamps,the photocatalytic degradation rate of MB by(V,Co)-TiO2 nano-semiconductor photocatalyst reached 92.12%for 60 min,which was obviously better than the catalytic efficiency of 56.55%for P25.3.By assembling different TiO2(pure TiO2,V-TiO2,Co-TiO2,(V,Co)-TiO2)as the porous layer(FTO/TiO2 dense layer/porous layer TiO2/CH3NH3Pbl3/C)calcium titanium Mineral solar cells,and studied their photovoltaic characteristics,found that V,Co ion doped TiO2 semiconductor as a porous layer of perovskite solar cells,the filling factor increased,and thus its photoelectric conversion efficiency has been improved.Especially,the conversion efficiency of the solar cell using the(V,Co)-TiO2 semiconductor as a porous layer was increased from 8.29%to 10.18%.