Hydrogen sorption kinetics of ball-milled MgH2–TiO2 based 1D nanomaterials with different morphologies

• TiO2 based nanomaterials morphology plays an important role in improving MgH2 abs/des.
• The TTNT-550C (nanorods) showed the most significant enhancements.
• The sample with TTNT-550C absorbed 5.5 wt% of H2 in 10 min at 350 °C.

The main purpose of this work was to compare the addition of two different TiO2 based one dimensional catalysts to verify which one enhances more the hydrogen uptake by using magnesium hydride (MgH2). Titanate nanotubes (TTNT-Low) were synthesized by alkaline hydrothermal treatment and TiO2 nanorods (TTNT-550C) were produced through the TTNT-Low heat treatment conducted at 550 °C. Afterwards, 5 wt% of each catalyst, TTNT-Low and TTNT-550C, was ball milled with MgH2. The samples were analyzed by means of X-ray diffraction (XRD) to evaluate the phase composition. A study was performed on the hydrogen absorption/desorption properties of the MgH2-TTNT samples using a Sievert's apparatus. The dehydrogenation process was also studied in a differential scanning calorimeter (DSC) from the DSC non-isothermal curves. Transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray energy-dispersive spectroscopy (XEDS) analyses of as milled samples played an important role to help elucidate the effect of mechanical milling on the TiO2 based nanomaterials morphology and dispersion in MgH2. The MgH2 + 5wt.% TTNT-550C sample exhibited the best performance for hydrogen absorption/desorption kinetics. At 350 °C it absorbed 5.5wt% of hydrogen after 10 min and desorbed, in 5 min, around 100% of the total that was absorbed.