Mitigation of CO2 greenhouse effect, combined disposal and utilisation by photocatalysis

The two options of mitigating CO2 Greenhouse Effect: disposal/storage and fixation/utilisation, can be simultaneously achieved by photocatalysis. CO2 captured in alkali solution gives carbonate. The latter can be reduced to C (for storage) and methanol (for utilisation) using a semiconductor photocatalyst and a light source. In this process C is directly produced unlike the HYDROCARB process. Methanol is also directly and simultaneously obtained in contrast to its production using H-2 or CH4 as reductants. Using Pt/TiO2 as a catalyst, the rate of formation: MeOH>C increased with [CO32-] and with [catalyst] but gradually decreased with time. An increase in pH from 9.7 to 12.2 produced a small increase in [MeOH]. The rate of formation: C>MeOH was found with Pt/TiO2, MoS2 or ZnTe under visible light irradiation but the latter catalyst gave nearly equal rates under U.V./visible illumination.