PHOTOCATALYTIC SYNTHESIS OF CH4 AND CH3OH FROM CO2 AND H2O ON HIGHLY DISPERSED ACTIVE TITANIUM-OXIDE CATALYSTS

UV-irradiation of the highly dispersed titanium oxide catalysts in the presence of CO2 and H2O at 275 K led to the formation of CH4, CH3OH, C-2-compounds, CO and O-2. The yields of the photocatalytic reaction strongly depended on the types of catalysts, the ratio of CO2/H2O and the reaction temperature. The photocatalytic reduction of CO2 with H2O is linked to the much higher reactivity of the charge transfer excited state, i.e., (Ti3+-O-)* of the tetrahedral coordinated titanium oxide species formed on the surfaces. Based on the detection of the reaction intermediate species such as Ti3+, H atoms, and C radicals, a molecular scale reaction mechanism has been proposed.