Effect of redox treatments on activation and deactivation of gold nanospecies supported on mesoporous silica in CO oxidation

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• 作者：N. Bogdanchikova^a ; A. Pestryakov^b ; ^{pestryakov2005@yandex.ru} ; I. Tuzovskaya^c ; T.A. Zepeda^a ; M.H. Farias^a ; H. Tiznado^a ; O. Martynyuk^a
• 关键词：Gold ; Silica ; CO oxidation ; Clusters ; Nanoparticles
• 刊名：Fuel
• 出版年：2013
• 出版时间：August, 2013
• 年：2013
• 卷：110
• 期：Complete
• 页码：40-47
• 全文大小：492 K

文摘

The influence of pretreatments with He, O₂ and H₂ on the physicochemical and catalytic properties of gold supported on hexagonal mesoporous silica (HMS) has been studied by a variety of methods including: XPS, TPR, N₂ sorption, UV-visible spectroscopy, FTIR and catalytic testing. The investigations show supported gold to form different states under redox treatments: Au³⁺ and Au⁺ ions, neutral and partly charged gold clusters and metal nanoparticles of different sizes. Reducing pretreatments increase the catalytic activity of the samples; while oxidative treatments deactivate the catalyst. Catalytic tests show several regions of the reduced samples with various catalytic behaviours: 20-200 ¡ãC, 200-400 ¡ãC and >400 ¡ãC; this situation is explained by the co-existence of gold active sites of different types. A comparative analysis among spectroscopic and catalytic data allows suggesting clusters to be responsible for the activity in the low-temperature region (<200 ¡ãC); neutral Au_n clusters are active in the range 200-400 ¡ãC; and gold nanoparticles may catalyze high-temperature CO oxidation. Au³⁺ ions are inactive in this process.