Photoreduction of copper ions using silica–surfactant hybrid and titanium (IV) oxide under sulfuric acid conditions

Photoreduction of Cu 2+ ions to Cu metal by titanium (IV) oxide (TiO 2 ) was conducted in the presence of silica-surfactant hybrid under a sulfuric acid condition. After irradiation, the dark-red color, reflections due to Cu metal in the X-ray diffraction pattern, and peaks due to Cu 2 p 1/2 and 2 p 3/2 in the X-ray photoelectron spectrum revealed the precipitation of Cu metal in the product. In addition, an increase in the BET surface area of 591 m 2 /g for the product from those of 36 and 45 m 2 /g for the silica-surfactant and TiO 2 as well as a decrease in the intensities of C-H stretching band in the Fourier-transform infra-red spectra implied the removal of surfactants during the reaction. These characteristics were never obtained using TiO 2 solely. Therefore, this study indicated that photoreduction of Cu 2+ ions to Cu metal by TiO 2 was facilitated under sulfuric acid conditions, where the surfactants extracted from silica–surfactant hybrids by protons in the acidic condition were successfully photo-oxidized by TiO 2 . Thus, this study presented a new usage of the conversion of silica-surfactant hybrid into mesoporous silicas.