XPS study of influence of exposure to air on thermal stability and kinetics of hydrogen decomposition of MgH2 films obtained by direct hydrogenation from gaseous phase of metallic Mg

Mechanism of influence of exposure to air on thermal stability of MgH2 obtained by direct hydrogenation from the gas phase, the nature of the hydride sensitivity to the negative impact of air and the role of its surface chemical state have not been studied enough. The present article presents data of X-ray photoelectron spectroscopy (XPS) measurements of the Mg 2s, O 1s, C 1s core-level spectra of surface of hydride MgH2 films derived by gas phase hydrogenation of model samples of metallic Mg, and the evolution of changes in the chemical state of the surface of the hydride films depending on the time of exposure to air and formation conditions (hydrogen pressure and hydrogenation regime). Based on results of XPS, X-ray diffraction (XRD), and thermodesorption spectroscopy (TDS), the existence of a relationship (correlation) between chemical surface condition of hydride MgH2 films obtained at different hydrogen pressures (3.0 MPa and 11.5 MPa) and their thermal stableness and temperature of the beginning of hydride decomposition has been established.