Ion engineering techniques for the preparation of the highly effective TiO2 photocatalysts operating under visible light irradiation

The successful application of ion engineering techniques for the development of TiO2 photocatalysts operating under visible and/or solar light irradiations has been summarized in this review article. First, we have physically doped various transition metal ions within a TiO2 lattice on an atomic level by using an advanced metal ion implantation method. The metal ion implanted TiO2 could efficiently work as a photocatalyst under visible light irradiation. Some field tests under solar light irradiation clearly revealed that the Cr or V ions implanted TiO2 samples showed 2-3 times higher photocatalytic reactivity than the un-implanted TiO2. Second, we have developed the visible light responsive TiO2 thin film photocatalyst by a single process using an RF-magnetron sputtering (RF-MS) deposition method. The vis-type TiO2 thin films showed high photocatalytic reactivity for various reactions such as reduction of NOx, degradation of organic compounds, and splitting of H2O under visible and/or solar light irradiations.