Adsorption and Desorption of Hydrogen by Gas-Phase Palladium Clusters Revealed by In Situ Thermal Desorption Spectroscopy

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• 作者：Masato Takenouchi ; Satoshi Kudoh ; Ken Miyajima ; Fumitaka Mafun茅
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：July 2, 2015
• 年：2015
• 卷：119
• 期：26
• 页码：6766-6772
• 全文大小：359K
• ISSN：1520-5215

文摘

Adsorption and desorption of hydrogen by gas-phase Pd clusters, Pd_n⁺, were investigated by thermal desorption spectroscopy (TDS) experiments and density functional theory (DFT) calculations. The desorption processes were examined by heating the clusters that had adsorbed hydrogen at room temperature. The clusters remaining after heating were monitored by mass spectrometry as a function of temperature up to 1000 K, and the temperature-programmed desorption (TPD) curve was obtained for each Pd_n⁺. It was found that hydrogen molecules were released from the clusters into the gas phase with increasing temperature until bare Pd_n⁺ was formed. The threshold energy for desorption, estimated from the TPD curve, was compared to the desorption energy calculated by using DFT, indicating that smaller Pd_n⁺ clusters (n 鈮?6) tended to have weakly adsorbed hydrogen molecules, whereas larger Pd_n⁺ clusters (n 鈮?7) had dissociatively adsorbed hydrogen atoms on the surface. Highly likely, the nonmetallic nature of the small Pd clusters prevents hydrogen molecule from adsorbing dissociatively on the surface.