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 carried out by applying advanced metal 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 red shift 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 earring 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 and global scale.
Anpo, M., & Takeuchi, M. (2001). Design and development of second-generation titanium oxide photocatalysts to better our environment - Approaches in realizing the use of visible light. International Journal of Photoenergy, 3(2), 89–94. https://doi.org/10.1155/S1110662X01000101