Toshihiko Yoshimura, Kentaro Shiraishi, Tatsuhiro Takeshima, Motonori Komura and Tomokazu Iyoda Pages 69 - 78 ( 10 )
Titanium oxide is known as a photocatalytic material that promotes the generation of hydrogen and oxygen from water by sunlight irradiation. In the present study, titanium oxide particles were treated by water jet cavitation generated using an ejector nozzle. Sub-stream suction occurs in small-sized high-pressure ejector nozzles because of the dynamic high pressure. The water containing titanium oxide powder or a mixed powder of titanium oxide and platinum enters the high-pressure water flow as a sub-stream. In the ejector nozzle, generation, growth, and collapse of cavitation are repeated with the particles of titanium oxide and platinum. Because the cavitation has an extremely high collapse pressure, the surface of the titanium oxide particles is processed by the microjets of cavitation in a so-called reactor comprising the ejector nozzle. The titanium oxide particles subjected to ejector cavitation (EC) processing were investigated for improvements to their photocatalytic properties under ultraviolet irradiation. It was found that noted that nano-level roughness is formed by EC processing. The TiO2 particles or TiO2 particles supported by Pt particles as a cocatalyst containing water were introduced into a vacuum chamber and the gases such as hydrogen and oxygen from the particle surfaces were measured by quadrupole mass spectrometry under ultraviolet irradiation. The EC processing was found to increase the amount of gases generated, including hydrogen and oxygen. Moreover, the amount of hydrogen in particular increases remarkably when both EC processing and support of platinum as a co-catalyst are used. It was also found that the titanium TiO2 particles were supporting minute platinum particles that detached from the original Pt particles during EC processing.
Cavitation, co-catalyst, ejector nozzle, photocatalyst, platinum.
Department of Mechanical Engineering, Tokyo University of Science, Yamaguchi, 1-1-1 Daigaku-dori, Sanyo-Onoda, Yamaguchi 756-0884 Japan.