Abstract
This study has been undertaken to investigate the roles of PtO and PtO 2 deposits in photocatalytic oxidation of NO over Pt-modified TiO 2 catalysts. These photocatalysts were prepared by neutralization method and characterized by XRD, BET, XPS, TEM and FTIR. It was found that Pt dopant existed as PtO and PtO 2 particles in as-prepared photocatalysts. And these Pt dopants would change their oxidation states during the photocatalytic oxidation reaction. An in situ XPS study indicated that a portion of PtO 2 on the surface of Pt/TiO 2 was reduced to PtO under UV irradiation. The migration of electrons to PtO 2 particles could separate the electrons and holes, resulting in the improvement of photocatalytic activity. And the depletion of PtO 2 by electrons could lead to the deactivation of Pt/TiO 2 catalyst. Moreover, PtO particles could be corroded to form Pt 2+ ions by HNO 3, which was one of the products of photocatalytic oxidation of NO. NO would adsorb on Pt 2+ related sites to form Pt n+ –NO nitrosyls, retarding photocatalytic oxidation of NO to NO 2.
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