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

氢化镁（MgH2）具有7.6%的高氢密度，是一种备受关注的储氢材料。但其吸氢解吸速度太慢，吸氢解吸温度过高，不利于实际应用。最近有报道称，覆盖金属层的镁薄膜在相对温和的温度下吸收氢。镁膜的吸氢温度取决于镁层厚度和表层厚度。这一现象被解释为表面层的弹性夹紧效应，它抑制了氢吸收过程中Mg层的体积膨胀。弹性约束理论有望适用于表面有一层氧化物的MgH2或Mg。因此，本研究考察了Mg薄膜和MgH2纤维表面氧化对其储氢性能的影响。

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.