Interaction of zirconia with magnesium hydride and its influence on the hydrogen storage behavior of magnesium hydride

Abstract

This study demonstrates how zirconia additive transforms to zirconium hydride and substantially lowers the dehydrogenation temperature of magnesium hydride. We prepared MgH2+xZrO2 (x = 0.125 and 0.5) powder samples reacted for 15 min, 1 h, 5 h, 10 h, 15 h, 20 h and 25 h, and monitored the phase changes at each stage of the reaction. Differential scanning calorimetry (DSC) study provides the first crucial evidence regarding the chemical transformation of zirconia. Subsequently, detailed additional sample testing by X-ray diffraction (XRD), energy dispersive x-ray spectroscopy and confocal Raman microscopy provide strong supports that low temperature dehydrogenation of magnesium hydride is a result of formation of an active in situ product (zirconium hydride). This observation is validated by the negative Gibbs free energy values obtained for the formation of zirconium hydride over a broad working temperature range of 0–600 °C. Scanning electron microscopy (SEM) results prove the high dispersion of tiny nanoparticles all across the surface after the chemical interaction between MgH2 and ZrO2 and atomic force microscopy (AFM) study further proves that objects with grain sizes of ∼10 nm are abundant throughout the scanned surfaces. These observations reiterate that better metal oxide additives interact with MgH2 and results to the evolution of highly active insitu nanocatalysts.