Photocatalytic reduction of CO2 using TiO2 powders in liquid CO2 medium

The photocatalytic reduction of CO2 was investigated using TiO2 powders in liquid CO2 medium. The TiO2 powders with liquid CO2 medium were illuminated in a stainless steel vessel. After reducing CO2 pressure to the ordinary state, purified water was added to the vessel containing the TiO2 powders without air contamination. No gaseous reduction products were observed and formic acid was exclusively obtained in the aqueous solution. It seems that formic acid is produced through the protonation of the reaction intermediates on the TiO2 powders with purified water