Photocatalytic Reduction of CO₂ Over Sol-Gel Derived Copper-Doped Titania Catalysts

Different doping concentration of copper-doped titania was synthesized by sol-gel method, and the samples were characterized by X-ray diffraction (XRD); Field emission scanning electron microscope (FSEM-EDX); Specific surface area and Pore size analyzer (BET); Thermo gravimetric-differential thermal analyzer (TG-DTA) respectively. The photocatalytic reduction of CO₂ experiments was carried out in a photocatalytic reactor. CO₂ was discharged into a quartz reactor with catalyst suspended in NaHCO₃ solution, and illuminated under UV irradiation at the wavelength of 253.7 nm for 10 h continuously. The results confirmed that in the copper modified TiO₂ samples, the crystalline form of TiO₂ exists as anatase; only on the high CuO loading sample (>10%), the CuO peaks appears obviously; the grain size of all the sol-gel derived CuO-TiO₂ samples were nearly 30 nm, and the copper particles were consistent and dispersed on the surface of TiO₂. CO₂ can be reduced into methanol in the presence of NaHCO₃ solution over CuO-TiO₂ catalyst. The doping concentration of 5% CuO-TiO₂ performed best catalytic effect, with the methanol yield of 27 mg (g-cata)⁻¹ in 10 h. With increasing reaction time, yield of methanol was promoted.