Sonophotocatalysis of water in a CO2–Ar atmosphere

A system combining photocatalysis and sonolysis, named a sonophotocatalysis system, was carried out. Sonophotocatalysis means simultaneous irradiation of ultrasound and light with a photocatalyst (TiO2 powder). As one of possibilities for this system, the resemblance between the reaction of this combined system and photosynthesis was discussed. The overall process of photosynthesis can be divided into two parts: reduction of CO2 and generation of oxygen from water. In this study, sonophotocatalysis was performed in a CO2–Ar atmosphere, resulting in reduction of CO2 to CO and continuous generation of O2 from water. Thus, photosynthesis-like reactions can be achieved using this combined system, though incident light energy does not accumulate. Further development of this system in the future is discussed in this paper.