Study on the effects of titanium oxide based nanomaterials as catalysts on the hydrogen sorption kinetics of magnesium hydride

Full text: Magnesium hydride is highly attractive for hydrogen storage in solid state in reason of its high gravimetric capacity (7,6 wt% of H₂) and low density (1,7 g/cm³), making it a promissory candidate for mobile applications [1]. However, its low sorption kinetics and desorption temperature are the main obstacles for its application. In the present study the catalytic role of TiO₂ based nanomaterials with different morphologies on the sorption kinetics of MgH₂ was evaluated. The additions consisted on titanate nanotubes (TTNT-Low), TiO₂ nanorods (TTNT-550) and nanoparticles (KA-100, TTNT-ACID). Transmission and Scanning Transmission Electron Microscopy (S/TEM) associated with X-ray Energy Dispersive Spectroscopy (XEDS) mapping was used to characterize the catalysts' morphology and crystalline structure and their dispersion within magnesium hydride, altogether with other characterization techniques such as X-ray diffraction (XRD) and BET technique for structure and surface area analysis. The sorption kinetics were evaluated by means of a volumetric gas absorption/desorption (Sievert-type) apparatus. The results indicated that all additives improved the sorption kinetics of MgH₂, but the samples with TTNT-550 (TiO₂ nanorods) and TTNT-ACID (TiO₂ nanoparticles) presented the best and the second best performances, respectively, suggesting that the 1D morphology may promote a slightly superior kinetics than particulate catalysts. (author)