Copper and iodine co-modified TiO 2 nanoparticles (Cu-I-TiO 2) were synthesized through a combined hydrothermal and wet-impregnation process. The structures and properties of the catalysts were characterized by XRD, BET, SEM/EDX, XPS, and UV-vis diffuse reflectance spectroscopy. Iodine ions were doped in the TiO 2 lattice by replacing Ti 4+ and, consequently, Ti 3+ was generated to balance the charge. Iodine doping reduced the TiO 2 crystal size and was responsible for visible light absorption. Cu species were found to deposit on the surface of TiO 2 and resulted in a slightly increased particle size. The activity of the Cu-I-TiO 2 catalyst was investigated by the photocatalytic reduction of CO 2 with water vapor, and CO was found to be the major reduction product with trace amounts of CH 4 generated. Under UV-vis irradiation, the activity of the co-modified catalyst (Cu-I-TiO 2) was higher than that of the single ion-modified catalysts (Cu-TiO 2 or I-TiO 2). Under visible light irradiation, the addition of Cu to I-TiO 2 did not lead to significant improvements in CO 2 reduction. Methyl chloride (CH 3Cl) was detected as a reaction product when CuCl 2 was used as the precursor in the synthesis, thus suggesting that methyl radicals are reaction intermediates. When CuCl 2 was used as the Cu precursor, a three-fold increase in CO 2 photoreduction activity was observed, as compared to when Cu(NO 3) 2 was used as the Cu precursor. These differences in activities were probably due to enhanced Cu dispersion and the hole-scavenging effects of the Cl ions. However, the formation of by-products (e.g., CH 3Cl) may be undesirable.
- CO reduction
- Solar energy
ASJC Scopus subject areas
- Environmental Science(all)
- Process Chemistry and Technology