Pneumatochemical Immittance Spectroscopy for Hydrogen Storage Kinetics

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• 作者：Eui-Chol Shin ; Young-Hun Kim ; Sun-Jung Kim ; Choong-Nyeon Park ; Jaekook Kim ; Jong-Sook Lee
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：October 3, 2013
• 年：2013
• 卷：117
• 期：39
• 页码：19786-19808
• 全文大小：2239K
• 年卷期：v.117,no.39(October 3, 2013)
• ISSN：1932-7455

文摘

Frequency domain analysis of the hydrogen storage kinetics was performed by Fourier transformation of the point relaxation data monitored for a pressure鈥揷omposition isotherm (PCI) of Mg/MgH₂ system at 325 掳C. The correlated hydrogen flux and the pressure relaxation under constant-volume conditions in a typical Sievert鈥檚 type setup leads to the presence of the characteristic inductive loop, the size of which corresponds to R parameter for RC transmission line model for diffusion in the spherical geometry, while the theoretical dc limit resistance may not indicate the diffusion contribution only. The kinetic information was shown equivalent to that of time-domain analysis based on the diffusion problem of a solute in a limited amount into solid state from a well-stirred medium [J. Phys. Chem. C 2013, DOI: 10.1021/jp401286b]. The spectra further develop into the oscillating trajectories originating from the truncation in the sampling. The essential experimental features can be simulated by a RL two-rail transmission line model. A parametric analysis of the preoscillation spectral range using ideal lumped elements provided information on the exponential relaxation constants, nucleation/surface reaction in the two-phase region, and the sampling periods as well as the diffusivity. The pneumatochemical immittance spectroscopy (PnIS) developed in the present work allows a fully automated hydrogen storage kinetic analysis with visualized R and C parameters for the estimation of chemical diffusivity as a function of storage state using the relaxation data measured for PCI by conventional Sievert鈥檚 apparatuses.