Colloidal Counterpart of the TiO2-Supported V2O5 System: A Case Study of Oxide-on-Oxide Deposition by Wet Chemical Techniques. Synthesis, Vanadium Speciation, and Gas-

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• 作者：Mauro Epifani ; Ra眉l D铆az ; Carmen Force ; Elisabetta Comini ; Teresa Andreu ; Reza R. Zamani ; Jordi Arbiol ; Pietro Siciliano ; Guido Faglia ; Joan R. Morante
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：October 10, 2013
• 年：2013
• 卷：117
• 期：40
• 页码：20697-20705
• 全文大小：537K
• 年卷期：v.117,no.40(October 10, 2013)
• ISSN：1932-7455

文摘

TiO₂ anatase nanocrystals were surface modified by deposition of V(V) species. The starting amorphous TiO₂ nanoparticles were prepared by hydrolytic processing of TiCl₄-derived solutions. A V-containing solution, prepared from methanolysis of VCl₄, was added to the TiO₂ suspension before a solvothermal crystallization step in oleic acid. The resulting materials were characterized by X-ray diffraction, transmission electron microscopy (TEM), Fourier transform infrared, Raman, and magic angle spinning solid-state ⁵¹V nuclear magnetic resonance spectroscopy (MAS NMR). It was shown that in the as-prepared nanocrystals V was deposited onto the surface, forming Ti鈥揙鈥揤 bonds. After heat treatment at 400 掳C, TEM/electron energy loss spectroscopy and MAS NMR showed that V was partially inserted in the anatase lattice, while the surface was covered with a denser V鈥揙鈥揤 network. After heating at 500 掳C, V₂O₅ phase separation occurred, further evidenced by thermal analyses. The 400 掳C nanocrystals had a mean size of about 5 nm, proving the successful synthesis of the colloidal counterpart of the well-known TiO₂鈥揤₂O₅ catalytic system. Hence, and also due to the complete elimination of organic residuals, this sample was used for processing chemoresistive devices. Ethanol was used as a test gas, and the results showed the beneficial effect of the V surface modification of anatase, with a response improvement up to almost 2 orders of magnitude with respect to pure TiO₂. Moreover, simple comparison of the temperature dependence of the response clearly evidenced the catalytic effect of V addition.