PHOTO-ASSISTED CATALYTIC REDUCTION OF CO2 WITH PREADSORBED AMMONIA ON SILICA-SUPPORTED IRON

Carbon dioxide has been photoreduced at 5-degrees-C using pre-adsorbed ammonia on silica-supported iron as a reducing agent, and the major product was CO, with smaller amounts of CH4. The reduction was attributed neither to photolysis via ammonium carbamate nor to that of the gas mixtures in the volume, but rather to photo-assisted catalysis through an intermediate formed by the reaction of adsorbed NH3 and CO2. The quantum yield of CO formation was less than 0.5. A model for the reaction pathway of the photoreduction of CO2 was proposed in which the essential steps involve the split of two N-H bonds due to the absorption of two photons.