The interaction of hydrogen with oxidic promoters of hydrogen storage in magnesium hydride

The present work is devoted to monitor the reactivity with hydrogen of various oxide systems (Nb2O5, WO3 and a mixed Mg/Nb/O oxide) in the aim of understanding the role of oxides as promoters for hydrogen storage in MgH2. The reactivity of the oxides has been tested using either molecular hydrogen or “nascent” hydrogen produced by reaction of zinc with hydrochloric acid. Thermal desorption-mass spectrometry experiments indicate that hydrogen adsorbed in Nb2O5 and Mg/Nb/O mixed oxides is, in part, reversibly released and, for a second fraction, released as water. By contrast, water is the only product desorbed by WO3 after contact with hydrogen. This could explain the higher performances of Nb2O5 as kinetic promoter of hydrogen storage in comparison with WO3.