Visible-light-induced oxidative removal of nitrogen oxides in air by metal chloride-modified titanium (IV) oxide nanoparticles

Abstract

Various metal chloride-modified titanium(IV) oxide (TiO2) (MCMT) samples were prepared by loading metal chloride on commercial TiO2 nanoparticles (Ishihara ST-01) having a large specific surface area and used for photoinduced oxidative removal of nitrogen oxides (NO x ) in air under irradiation of visible light and/or ultraviolet (UV) light. The NO x removal activity of MCMT samples under photoirradiation from a blue fluorescent lamp (BFL) with a UV cut filter decreased in the following order: RhCl3/ST-01>H2PtCl6/ST-01>RuCl3/ST-01>ST-01>IrCl4/ST-01>HAuCl4/ST-01, indicating that RhCl3. H2PtCl6 and RuCl3 fixed on TiO2 effectively worked as photosensitizers for NO x removal. NO x was almost quantitatively fixed as nitrate on RhCl3/ST-01 photoirradiated with BFL or blue light-emitting diodes. Under irradiation of both visible light and UV light from a white fluorescent lamp, RhCl3/ST-01 exhibited a higher level of removal of NO x and a much lower level of release of nitrogen dioxide than did bare ST-01, indicating that RhCl3/ST-01 effectively utilized both visible light and UV light and that two types of reaction (photosensitization by fixed RhCl3 and photocatalysis by TiO2) occurred over RhCl3/ST-01.