Preparation Of CuO/TiO₂ Nanofibers And Synthesis Of Methanol Through CO₂ Reduction Under Visible Light Irradiation

Reducing greenhouse gas CO₂ and searching for green energy to solve the problem of energy deficiency have been the purpose of all mankind.Photocatalytic reduction of CO₂ and H₂O to methanol is one of the most promising technologies at present.Attribute to low cost and high stability,TiO₂ has been favored by photocatalyst researchers,however,it is not widely used due to its fast electron-hole recombination and low utilization rate of sunlight.In this paper,TiO₂ nanofibers with a diameter of 8-10 nm were successfully prepared by vapor-phase growth with mesoporous SiO₂ spheres as templates and TiCl₄ as precursor.Compared to anatase TiO₂ nanoparticles and P25,TiO₂ nanofibers showed much lower fluorescence intensity,which meant better stability of electron-hole,the yield of methanol over TiO₂ nanofiber was 310?mol/g-cat under the irradiation of 300 W xenon lamp for 4h,which was 84.2%higher than over TiO₂ nanoparticles and 38.4%higher than P25.In order to enhance TiO₂ nanofibers' absorption of visible light,CuO was loaded on TiO₂ nanofibers to form heterogeneous structure,and CuO/P25 was also prepared for comparison,after loading CuO,the absorption of visible light of two catalysts was improved,the fluorescence intensity was also further reduced,which indicated the rate of electron-hole recombination decreased.Under the irradiation of 300W xenon lamp for 4h,yield of methanol was 597?mol/g-cat over CuO/P25,2.3 times higher than over P25,while the yield of methanol increased to 1674?mol/g-cat,4.4 times higher than over pure TiO₂ nanofibers.For further improving the catalytic activity of TiO₂ nanofibers in the synthesis of methanol,erbium and ytterbium was successfully co-doped into the TiO₂ nanofibers through vapor growth method,Er-Yb-TiO₂ nanofibers could transfer infrared light to visible light through up-conversion,after loading CuO on Er-Yb-TiO₂ nanofibers,thus,catalyst was able to absorb the infrared light and visible light,utiliztion of xenon lamp was improved,luorescence intensity was also further reduced.Under the irradiation of 300W xenon lamp for 4h,yield of methanol increased to 2523.5?mol/g-cat,7.4 times higher than over pure TiO₂ nanofibers.Characterization methods like SEM,TEM,XPS,UV-Vis,XRD,PL were used to test the crystal structure,morphology,the element valence,visible absorption intensity,electron-hole recombination rate and up-conversion performance.