Preparation Of TiO₂ Nanowires And Synthesis Of Methanol From CO₂ And H₂O Under Visible Light Irradiation

Today,human beings are facing with two major problems of environmental deterioration and one-off energy depletion.The greenhouse gas CO2 is generated by traditional energy sources poses a serious threat to the environment.So using sustainable solar energy to convert surplus atmospheric CO2 into fuel resources such as methanol has become the focus of scientists.In this paper,a new method of preparing TiO2 nanowires was adopted.Mesoporous SiO2 spheres were used as templates to prepare TiO2 nanowires with diameter of 8?10nm.The nanowires had large specific surface area and good dispersibility.In the catalytic synthesis of methanol reaction by CO2 under the simulated visible light,it shows better catalytic performance than P25.In order to further improve the catalytic activity of TiO2 nanocatalyst for the synthesis of methanol under visible light,nitrogen was successfully doped into the TiO2 lattice by introducing ammonia in the hydrolysis atmosphere of TiCl4,the titanium source(TiCl4)was mixed with the modifiers in the gas phase and achieve the uniform mixing at the molecular level.Doping with N narrowed the band gap of the TiO2 nanofibers and enhanced the absorption of the visible light,reduced the fluorescence intensity and photo-electron-hole recombination rate.Under the irradiation of 300W xenon lamp for 2 h,the yield of methanol was increased to 1390.10 umol/g-cat.On the basis of Nitrogen doped TiO2(N-TiO2),amorphous oxide semiconductor(Ni-Mo-B-O)was loaded on the surface of TiO2 nanowires to form heterojunction catalyst.We found that when the amorphous oxide semiconductor's chemical composition was Ni1.92Mo6.42B021.74,its band gap was only 1.8 V(vs RHE),which could absorp the full spectrum of visible light and had a high leading position(-1.3 V vs RHE).After forming a heterojunction catalyst with TiO2 nano wires,not only the absorption the full spectrum of visible light can be realized,but also the fluorescence intensity is further reduced.under the irradiation of 300W xenon lamp for 2 h,the yield of methanol synthesized under visible light was greatly increased to 7174.81?mol/g-cat.In addition,by changing the chemical composition of this amorphous oxide semiconductor could modulat its band gap and conduction band position.SEM,TEM,XPS,UV-Vis,XRD,PL,SPS and UPS etc.characterization methods were used to test the crystal structure,morphology,the element valence,visible absorption intensity,electron-hole recombination rate and band structure performance of catalysts...