Preparation of Visible-Light-Responsive TiO2-xNx Photocatalyst by a Sol−Gel Method: Analysis of the Active Center on TiO2 that Reacts with NH3
journal contributionposted on 16.08.2005 by Yasushige Kuroda, Toshinori Mori, Kazunori Yagi, Naoko Makihata, Yoichiro Kawahara, Mahiko Nagao, Shigeharu Kittaka
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Active reaction centers for ammonia on titanium oxyhydroxide were explored to direct the search for an efficient sol−gel method for the synthesis of a titanium oxynitride (TiO2-xNx) sample with an efficient responsiveness to the visible light constituting a main part of the solar spectrum. The results lead to the conclusion that the site giving IR bands at around 2195 cm-1 for the adsorbed CO molecules at 300 K is a reactive site and behaves as Lewis acid site in the coordination environment of distorted five-coordinate Ti4+ ions. Ammonia molecules are adsorbed on such a site to form −NH2 and −OH species during the heat treatments at a temperature above 373 K, and they are ultimately incorporated into the TiO2 lattice as nitride through the dehydration at higher temperatures of up to 723 K, resulting in the formation of an anatase type of TiO2-xNx.