Size and stress dependent hydrogen desorption in metastable Mg hydride films

• Published in: International journal of hydrogen energy Vol. 39; no. 6; pp. 2597 - 2607
• Main Authors: Ham, B., Junkaew, A., Arróyave, R., Park, J., Zhou, H.-C., Foley, D., Rios, S., Wang, H., Zhang, X.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 14.02.2014; Elsevier
• Subjects: Alternative fuels. Production and utilization; Applied sciences; Columnar structure; Destabilization; Energy; Exact sciences and technology; Fuels; Hydrides; Hydrogen; Hydrogen storage; Magnesium; Mg pillars; Morphology; Orthorhombic Mg hydride; Porous Mg films; Size effect; Solvents; Sorption; Stress effect; Stresses; Stress effect; Mg pillars; Destabilization; Porous Mg films; Size effect; Orthorhombic Mg hydride; Hydrogen; Desorption; Hydrides
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2013.12.017

Mg is a promising light-weight material that has superior hydrogen storage capacity. However H2 storage in Mg typically requires high temperature, ∼500–600 K. Furthermore it has been shown that there is a peculiar film thickness effect on H2 sorption in Mg films, that is thinner Mg films desorb H2 at higher temperature [1]. In this study we show that the morphology of DC magnetron sputtered Mg thin films on rigid SiO2 substrate varied from a continuous dense morphology to porous columnar structure when they grew thicker. Sputtered Mg films absorbed H2 at 373 K and evolved into a metastable orthorhombic Mg hydride phase. Thermal desorption spectroscopy studies show that thinner dense MgH2 films desorb H2 at lower temperature than thicker porous MgH2 films. Meanwhile MgH2 pillars with greater porosity have degraded hydrogen sorption performance contradictory to general wisdom. The influences of stress on formation of metastable MgH2 phase and consequent reduction of H2 sorption temperature are discussed. •Emphasizes the significance of stress on destabilization of Mg hydride.•Reveal the reduction of H sorption temperature in thinner Mg films.•Provide a forward step towards understanding the significance of stress (from rigid substrate) on destabilization of Mg hydride (orthorhombic MgH2).•Porosity reduces stress-induced during hydrogenation, and thus degrades the performance of Mg hydride.