Use of visible light. Second-generation titanium oxide photocatalysts prepared by the application of an advanced metal ion-implantation method

Titanium oxide catalysts were implanted with various transition-metal ions by a high-voltage acceleration technique, then calcined in O-2 at around 723 K to produce photocatalysts capable of absorbing visible light, the extent of the red shift depending on the amount and kind of metal ions implanted. Such metal ion-implanted titanium oxide photocatalysts, specifically using Cr or V ions, were successful in carrying out various photocatalytic reactions such as the decomposition of NO into N-2, O-2, and N2O at 293 K, significantly under irradiation with visible light longer than 450 nm. In outdoor field tests, these Cr and V ion-implanted titanium oxide photocatalysts showed three to four times higher photocatalytic reactivity for the decomposition of NO under solar beam irradiation, as compared with the original unimplanted titanium oxide photocatalyst.