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Open AccessArticle

A Heterothermic Kinetic Model of Hydrogen Absorption in Metals with Subsurface Transport

1
Department of Chemical Engineering, Kyoto University, Nishikyo, Kyoto 615-8510, Japan
2
Department of Chemical Engineering, University of Manchester, Oxford Rd, Manchester M13 9PL, UK
3
Graduate School of Advanced Integrated Studies in Human Survivability, Kyoto University, Sakyo, Kyoto 606-8306, Japan
*
Author to whom correspondence should be addressed.
Metals 2019, 9(10), 1131; https://doi.org/10.3390/met9101131
Received: 30 September 2019 / Revised: 18 October 2019 / Accepted: 20 October 2019 / Published: 22 October 2019
(This article belongs to the Special Issue Metals in Hydrogen Technology)
A versatile numerical model for hydrogen absorption into metals was developed. Our model addresses the kinetics of surface adsorption, subsurface transport (which plays an important role for metals with active surfaces), and bulk diffusion processes. This model can allow researchers to perform simulations for various conditions, such as different material species, dimensions, structures, and operating conditions. Furthermore, our calculation scheme reflects the relationship between the temperature changes in metals caused by the heat of adsorption and absorption and the temperature-dependent kinetic parameters for simulation precision purposes. We demonstrated the numerical fitting of the experimental data for various Pd temperatures and sizes, with a single set of kinetic parameters, to determine the unknown kinetic constants. Using the developed model and determined kinetic constants, the transitions of the rate-determining steps on the conditions of metal-hydrogen systems are systematically analyzed. Conventionally, the temperature change of metals during hydrogen adsorption and absorption has not been a favorable phenomenon because it can cause errors when numerically estimating the hydrogen absorption rates. However, by our calculation scheme, the experimental data obtained under temperature changing conditions can be positively used for parameter fitting to efficiently and accurately determine the kinetic constants of the absorption process, even from a small number of experimental runs. In addition, we defined an effectiveness factor as the ratio between the actual absorption rate and the virtually calculated non-bulk-diffusion-controlled rate, to evaluate the quantitative influence of each individual transport process on the overall absorption process. Our model and calculation scheme may be a useful tool for designing high-performance hydrogen storage systems. View Full-Text
Keywords: hydrogen; hydride; metal; palladium; absorption; adsorption; diffusion; storage; modelling; heat hydrogen; hydride; metal; palladium; absorption; adsorption; diffusion; storage; modelling; heat
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Ono, S.; Uchikoshi, T.; Hayashi, Y.; Kitagawa, Y.; Yeh, G.; Yamaguchi, E.; Tanabe, K. A Heterothermic Kinetic Model of Hydrogen Absorption in Metals with Subsurface Transport. Metals 2019, 9, 1131.

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