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Overpotential_Manuscript_V2.pdf (1.54 MB)

On the Common Ground of Thermodynamics and Kinetics: How to Pin Down Overpotential to Reversible Metal Hydride Formation and the Complete Ideal Gas Theory of Reversible Chemical Hydrogen Storage

revised on 13.12.2020, 20:40 and posted on 15.12.2020, 08:39 by Roland Hermann Pawelke
Ti-doped NaAlH4 requires at 125 °C for [AlH4] formation more than twice the equilibrium pressure; while it is straightforward to relate this conditional surplus in hydrogenation pressure respective chemical potential to kinetic hindrance, it appears strange that this matter has not been duly theoretically addressed in literature to this day. The interest in identifying such overpotentials is not of purely academic interest but touches a problem of very practical significance as the maximum applied pressure is an important threshold to metal hydride tank design. A theory-based tool would be a resource-efficient complement or even alternative to PCI measurements. This paper tracks the formation overpotential issue down to its root and outlines a simple yet accurate general method based on Arrhenius and van’t Hoff data. Rather unexpectedly, the result is also the final missing piece towards a comprehensive understanding of reversible chemical hydrogen storage with regard to attainable hydrogen storage capacity.


European Space Agency grant 4000105330/12/NL/CLP

European Defence Agency contract A-1341-RT-GP


Email Address of Submitting Author


FOTEC Forschungs- und Technologietransfer GmbH



ORCID For Submitting Author


Declaration of Conflict of Interest

No conflicts to declare.

Version Notes

V2, second revised version: 1.) Corrections in equations 10a and 10b and 11: an error occurred during the in silico transfer from paper, the eventual calculation in section 3 is correct but the equations leading there were not consistent. This has been corrected. 2.) The manuscript has been revised with regard to clarity and reading flow. Content-wise, no relevant changes were made.