Analysis of the Promoted Activity and Molecular Mechanism of Hydrogen Production over Fine Au鈥揚t Alloyed TiO2 Photocatalysts

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• 作者：Fenglong Wang ; Yijiao Jiang ; Douglas J. Lawes ; Graham E. Ball ; Cuifeng Zhou ; Zongwen Liu ; Rose Amal
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：July 2, 2015
• 年：2015
• 卷：5
• 期：7
• 页码：3924-3931
• 全文大小：413K
• ISSN：2155-5435

文摘

Fine metal nanoparticles (2鈥? nm; Au, Pt, and alloyed Au鈥揚t) with a narrow size distribution were deposited on active TiO₂ through a facile chemical reduction method. Compared to the bare TiO₂, a remarkable enhancement of up to 10-fold for photocatalytic hydrogen evolution was achieved on the alloyed nanocomposites. By using core level and valence band XPS analysis, two electronic properties are shown to contribute to the promoted photocatalytic activity: stronger metal鈥搒upport interaction between the alloyed structures and TiO₂ and higher electron population on the Au鈥揚t/TiO₂ photocatalysts in comparison with the bare TiO₂. Moreover, an improved charge separation over TiO₂ using Au鈥揚t nanoparticles was clearly evidenced by the significant increase of photocurrent responses obtained from the photoelectrochemical measurements. For the first time, in situ ¹³C and ¹H NMR spectroscopy was applied to monitor the gas鈥搇iquid鈥搒olid photocatalytic reactions under real working conditions. Via a two-electron oxidation pathway, the surface-adsorbed methanol was first oxidized to formaldehyde, followed by spontaneous hydrolysis and methanolysis to methanediol and methoxymethanol, rather than methyl formate and formic acid that have been previously reported in gaseous CH₃OH photocatalysis. The in situ monitoring also revealed that deposition of metal NPs would not alter the reaction pathways while making the reaction faster compared to the bare TiO₂.