Photoreduction Of CO₂ Property Of Copper Modified TiO₂ Nano-particles

The copper modified TiO₂ nano-particles catalysts were synthesized by sol-gel method in this article. The crystal structure, crystal morphology and chemical component were characterized using X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed that by doping of copper not only restrain the growth in size and aggregation of the TiO₂ nano-particles, but also inhibit phase transformation from anatase phase to rutile effectively. When the copper modifying ratio was less than 2.0 wt.%, copper mainly played the role of mental ions doping, but when the copper doping concentration more than 20 wt.%, the catalysts converted to CuO and TiO₂ compound semiconductor. The Cu+ and Cu²⁺ were detected on the surface of Cu/TiO₂ catalysts.Photocatalytic reduction CO₂ reaction was operated in methanol, acetonitrile and isopropyl organic solvents, and the activities of Cu/TiO₂ catalysts were evaluated by the yield of methyl formate and formic acid in the reaction system. The different copper adding amount, irradiation time, light wavelength and the kinds of organic solution all affected the photocatalytic reduction process and the photoreduction efficiency could be improved through optimization of reaction condition. Cu/TiO₂ catalysts got the highest activity when the addition of copper to TiO₂ reached 2.0 wt.%, producing 704.8μmol/g·cat. of methyl formate during 8 h reaction under the irradiation of 365nm UV light in methanol solvent. 20 wt.% Cu/TiO₂ also possessed better catalytic activity. Polarity of organic solvent affected the CO₂ reduction efficiency, and along with the increase of polarity of organic solvent, the yield of formic acid in reaction system was methanol > acetonitrile > isopropyl alcohol. Mechanism of CO₂ photocatalytic reduction on Cu/TiO₂ catalyst was proposed at last.