Decrease of hydrogen desorption temperature of metal hydride through elastic constraints by surface oxide

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Magnesium hydride (MgH2) has attracted great attention as a hydrogen storage material because of its high hydrogen density of 7.6 mass%. However, its hydrogen absorption and desorption is too slow and the absorption and desorption temperature is too high for practical applications. Recently, Mg thin film capped with a metallic layer was reported to absorbed hydrogen at relatively moderate temperature. The hydrogen absorption temperature of Mg film depends on the Mg layer thickness and the surface layer thickness. This phenomena was interpreted as effects of the elastic clamping of the surface layer, which inhibits volume expansion of the Mg layer during hydrogen absorption. The elastic constraints theory is expected to be applicable to MgH2 or Mg with a surface layer of oxide. Therefore, in this study, effect of surface oxidation on of Mg thin film and MgH2 fiber on their hydrogen storage properties were investigated.