Interaction Mechanisms of Ammonia and Tin Oxide: A Combined Analysis Using Single Nanowire Devices and DFT Calculations

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• 作者：Feng Shao ; Martin W. G. Hoffmann ; Joan Daniel Prades ; Joan Ramon Morante ; N煤ria L贸pez ; Francisco Hern谩ndez-Ram铆rez
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：February 21, 2013
• 年：2013
• 卷：117
• 期：7
• 页码：3520-3526
• 全文大小：414K
• 年卷期：v.117,no.7(February 21, 2013)
• ISSN：1932-7455

文摘

Tin oxide (SnO₂) represents a major fraction of research for developing solid-state gas sensors. Nevertheless, a detailed insight into the chemical-to-electrical transduction mechanisms between ammonia (NH₃) molecules and this metal oxide is still limited. Here, the adsorption of NH₃ on SnO₂ was examined by density functional theory (DFT) calculations and confronted to experimental data obtained with individual nanowire devices. It was concluded that under real working conditions nonlattice oxygens (O_5c) adsorbed on SnO₂ exhibit a more basic character than lattice bridging oxygens (O_2c), and consequently, they play a key role in the dehydrogenation of NH₃ on SnO₂, with N₂ and H₂O as the main resulting products. The sensing process of ammonia on tin oxide nanowires not only involves physical mechanisms but also has a concomitant chemical nature that requires two molecules of NH₃ for the reaction to take place. Our theoretical modeling reveals why ammonia sensing is competitive to the adsorption of water molecules. As a result, interfering effects in monitoring traces of NH₃ intrinsically occur in humid conditions.