The design and development of second-generation titanium oxide photocatalysts which absorb
UV-visible light and work as efficient photocatalysts under irradiation of light in the UV-visible light
regions were successfuly carriedout by applying advancedmetal ion-implantation techniques. Titanium oxide
catalysts were implanted with various transition-metal ions by a high-voltage acceleration technique,
then calcined in O2 at around 723–823 K to produce photocatalysts capable of absorbing visible light, the
extent of such redshift depending on the kind and amount of metal ion implanted. The transition-metal ion implanted titanium
oxide photocatalysts, specifically using V, Mn, or Cr ions, were successful in carring out
various photocatalytic reactions such as the decomposition of NOX and the reaction involving the decomposition of H2O at 295 K, significantly under irradiation with visible light longer than 450 nm. In outdoor field
reactivity tests, these V or Cr ion-implanted titanium oxide photocatalysts showed four to three times higher
photocatalytic reactivity for those photocatalytic reactions under solar beam irradiation, as compared with
the original unimplanted titanium oxide photocatalyst. The advantages and possibilities of utilizing such
second-generation titanium oxide photocatalysts are the only way to address environmental pollution on a
large andglobal scale.
