Reduction of carbon dioxide with water under concentrated sunlight using photocatalyst combined with Fe-based catalyst

The reduction of CO2 with water into valuable organic compounds under concentrated sunlight was investigated for the first time over a hybrid catalyst, in which a Pt-loaded K2Ti6O13 photocatalyst was combined with a Fe-based catalyst supported on a dealuminated Y-type zeolite (Fe-Cu-K/DAY). In this reaction system, the Pt/K2Ti6O13 catalyst decomposes water to produce H2 and the Fe-Cu-K/DAY catalyst reduces CO2 with the resulting H2 into organic compounds. When only the Pt/K2Ti6O13 photocatalyst was used, organic compounds such as CH4, HCOOH, and HCHO were formed together with H2, indicating that CO2 can also be directly reduced over Pt/K2Ti6O13. On the contrary, when the hybrid catalyst was used, CH3OH and C2H5OH were produced in addition to the above products, depending on the reaction temperature and catalyst composition. The reaction temperature significantly increased by concentrating the solar irradiation, reaching 600 K and increasing the product yields. It is suggested that such a high reaction temperature facilitates both the photoreduction and hydrogenation of CO2 over Pt/K2Ti6O13 and Fe-Cu-K/DAY, respectively.