Design and development of unique titanium oxide photocatalysts capable of operating under visible light irradiation by an advanced metal ion-implantation method

The metal ion-implantation of titanium oxide catalysts with various transition metal ions highly accelerated by high voltage and the subsequent calcination in O-2 at around 723 K enable a large shift in the absorption spectra toward visible light regions, its extent depending on the amount and the kind of metal ions implanted. Such metal ion-implanted titanium oxide catalysts were successful in carrying out various photocatalytic reactions such as the decomposition of NO into N-2, O-2, and N2O at 275 K under irradiation with visible light longer than 450 nm. In outdoor field tests, the Cr and V ion-implanted titanium oxide catalysts showed three and four times higher photocatalytic reactivity for the decomposition of NO under solar beam irradiation of 38.5 mW/cm(2), respectively, as compared with the unimplanted original titanium oxide catalyst.