Metal hydrides are attractive as an economical low-pressure alternative to high-pressure tanks in fuel cell electric vehicles. However, key thermodynamic and kinetic limitations continue to inhibit their widespread development. In an effort to overcome the slow reaction kinetics, reduce the high dehydrogenation temperature, and enhance the hydrogen storage capacity, an increasingly common strategy has been to synthesize metal hydrides in a nanoscale form or as heterogeneous composites. Such nano-confinement and heterogenization are expected to alter the thermodynamics and kinetics of the reactions and thus hydrogen storage performance as the role of interfaces becomes an increasingly important contribution, especially during (de)hydrogenation as the nucleation of intermediate compounds occurs.<br/><br/>As a part of the new DOE Hydrogen Storage Materials —Advanced Research Consortium (HyMARC), we have been investigating how interfaces affect the thermodynamics and kinetics of metal hydrides using multiscale combinatorial computations ranging from atomistic <i>ab initio</i> calculations to meso-scale phase field modeling and analytical isotherm modeling. In this talk, we will present some highlights from our recent computational activities, which include i) investigation of thermodynamic stability and nucleation kinetics of fully (de)hydrogenated metal hydrides and their reaction intermediates, ii) energetics of interfaces, iii) microstructure-dependent phase evolution during (de)hydrogenation, iv) modeling of isotherm absorption/desorption kinetics, v) and interface chemistry and transport. We consider the role of temperature, hydrogen pressure, and chemical composition to mimic the various environmental effects of metal hydrides in real use. Our predictions are combined with experimental measurements including X-ray spectroscopy and uptake isotherms to verify our approaches and provide a more complete analysis of the thermodynamics and kinetics of the underlying mechanisms.

Thermodynamics and kinetics at interfaces of metal hydrides for hydrogen storage

253rd National Meeting (2017)

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