Photocatalytic conversion of CO2 and H2O to useful fuels by nanostructured composite catalysis

Abstract Cu-TiO2 nano-catalysis were successfully prepared using sol-gel method and used for solar photo-reduction of CO2 in gas and liquid phase. Adding Cu to TiO2 matrix modify its crystalline structure, improved its optical property and increased the photo-catalytic activity toward CO2 reduction. Incorporating Cu at an oxidation state of 2+ into TiO2 matrix generated a mixture of Anatase and Rutile structure with high surface area, increased oxygen vacancies and enhanced atomic mobility which improved CO2 photo-reduction in both phases. The highest CO2 photoreduction rate was observed to occur for Cu-TiO2 nano-catalyst with Cu loading of 1.5 wt%. Methanol was the most produced hydrocarbon amongst the products with a production rate of 4.0 μmol·g-cat−1·h−1, followed by methane. Gas phase solar CO2 photo-reduction was effective and dependent on the gas relative humidity. CO2 and H2O mixture with relative humidity (%RH) ≤ 30% generated CH4 and CO as the main products. At higher %RH, the main products were methane, hydrogen, methanol, ethanol, and acetaldehyde. Gas phase solar CO2 photoreduction is more effective than liquid phase in terms of hydrocarbons production rate, space yield, and quantum efficiencies. Results showed that solar photo-catalytic reduction can be successfully applied to reduce CO2 from the atmosphere.