Converting of CO₂ into low-molecular-weight organic compounds with the TiO₂/ZrO₂ composites under solar irradiation

The preparation of a specially modified titanium dioxide/zirconium oxide (TiO₂/ZrO₂) composite and its subsequent application using a unique method are described. Specifically, after the whole surface of the composite was covered with a very thin layer of water, solar light was irradiated onto it. This method is unique because the reduction of CO₂ was performed in air (gas phase). The light source was real solar light. In this study, novel composites comprising nanometre-sized TiO₂ and micrometre-sized zirconium oxide (ZrO₂) increased the amount of reduced CO₂. And, suitable weight ratio of TiO₂/ZrO₂ was 6/4-5/5. Thin water layer on the composite offered catalytic-reaction medium, and, catalytic-reaction cite existed at interface of TiO₂ and ZrO₂ particles, and, this reaction was catalytic reaction enhanced by photocatalytic effect. A large amount of reduced products (maximum: approximately 300 μmol/(g·300 s) of formaldehyde and methanol)was obtained under only 300 s of irradiation of solar light.