Photocatalytic reduction of carbon dioxide using sol-gel derived titania-supported CoPc catalysts.

CoPc loaded titania was synthesized by an improved sol-gel method using a homogeneous hydrolysis technique. The grain size of TiO2 and CoPc-TiO2 was uniform and average diameters were less than 20 nm. Both catalysts had two crystal phases, of which rutile accounted for about 28%. When they were used for the photoreduction of CO2 in NaOH solution under ambient conditions, the formate yield was significantly higher than that of the others, such as formaldehyde, methanol and so on. In order to increase the activity of the photocatalysts some factors were optimized, including the quantity of CoPc-TiO2 catalyst, concentration of Na(2)SO(3) hole scavenger, concentration of the NaOH solution and irradiation time. Under the optimal conditions, the gross photocatalytic reduction of CO2 was 1032 micromol (g cat)(-1). Furthermore, the yield of CH4 did not increase in the presence of CH(3)OH or HCHO, showing that the generation of CH4 from CO2 did not proceed via methanol as an intermediate under these conditions.