Compensation Effect in H2 Permeation Kinetics of PdAg Membranes

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• 作者：Gaofeng Zeng ; Andreas Goldbach ; Lei Shi ; Hengyong Xu
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：August 30, 2012
• 年：2012
• 卷：116
• 期：34
• 页码：18101-18107
• 全文大小：369K
• 年卷期：v.116,no.34(August 30, 2012)
• ISSN：1932-7455

文摘

Knowledge about the (inter)dependence of permeation kinetic parameters on the stoichiometry of H₂-selective alloys is still rudimentary, although uncovering the underlying systematic correlations will greatly facilitate current efforts into the design of novel high-performance H₂ separation membranes. Permeation measurements with carefully engineered, 2鈥? 渭m thick supported Pd_100鈥?i>xAg_x membranes reveal that the activation energy and pre-exponential factor of H₂ permeation laws vary systematically with alloy composition, and both kinetic parameters are strongly correlated for x 鈮?50. We show that this permeation kinetic compensation effect corresponds well with similar correlations in the hydrogen solution thermodynamics and diffusion kinetics of PdAg alloys that govern H₂ permeation rates. This effect enables the consistent description of permeation characteristics over wide temperature and alloy stoichiometry ranges, whereas hydrogen solution thermodynamics may play a role, too, as a yet unrecognized source of kinetic compensation in, for example, H₂-involving reactions over metal catalysts or hydrogenation/dehydrogenation of hydrogen storage materials.