Influence of surface barriers on hydrogen storage in MgAl films on permeable stainless steel membranes

Abstract

The behavior of hydrogen in the plasma hydrogenated MgAl films on stainless steel membranes, in particular, the effect of surface and interface properties on the efficiency of hydrogenation and kinetics of hydrogen effusion were investigated. The paper aims at optimizing the processes of hydrogen retention and its thermal release on the basis of a model based on the "trapping" of hydrogen between the symmetric and asymmetric potential walls on the boundaries of the inlet and outlet sides of samples. The efficient retention of hydrogen was observed in the MgAl films protected by thin Al2O3 barrier layers on both film surfaces. The hydrogen effusion temperature dropped from 650 K for hydrogen trapped in the symmetric potential well down to 450 K for hydrogen trapped in the asymmetric one. The structural modifications and formation of hydrides were identified in the plasma hydrided MgAl films using X-ray diffraction. The hydrogen distribution profiles were investigated in the MgAl films and stainless steel membranes employing glow discharge optical emission spectroscopy. Thermal desorption analysis revealed the hydrogen effusion kinetics.