Effect of the activation temperature on the state of gold supported on titania: An FT-IR spectroscopic study

• Published in: Applied catalysis. A, General General, 2006-02, Vol.301 (1), p.106-114
• Main Authors: Venkov, Tz, Fajerwerg, K., Delannoy, L., Klimev, Hr, Hadjiivanov, K., Louis, C.
• Format: Article
• Language: English
• Subjects: Adsorption; Carbon monoxide; Catalysis; Chemical Sciences; Chemistry; Coordination chemistry; Exact sciences and technology; General and physical chemistry; Gold; Infrared spectroscopy; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2005.11.019

The effect of the pre-treatment conditions on the evolution of gold species on an Au/TiO 2 sample prepared by deposition–precipitation with urea has been followed by FT-IR spectroscopy of adsorbed CO. Gold is in the form of Au 3+ species on the as-prepared sample and is not affected by evacuation at ambient temperature. However, the Au 3+ species are readily reduced by CO at ambient temperature giving rise immediately to Au + cations (the corresponding carbonyls displaying a band at 2168 cm −1), which are then slowly converted into metallic gold (carbonyl band at around 2106 cm −1). The Au 3+ species are reduced to metal gold (respective carbonyl bands in the 2135–2100 cm −1 region) when a fresh sample is heated at T ≥ 473 K. Water was found to affect CO adsorption on metal gold sites only slightly. Oxidation of Au 0/TiO 2 by oxygen failed to produce cationic gold species. However, metallic gold was oxidized by heating the sample in a NO + O 2 mixture even at 573 K.