Carbon-wrapped Ti-Co bimetallic oxide nanocages: Novel and efficient catalysts for hydrogen storage in magnesium hydride

Abstract

Carbon-wrapped Ti and Co bimetallic oxide nanocages (Ti-CoO@C) were successfully synthesized through a regulated hydrothermal method and then doped into magnesium hydride (MgH2) by mechanical ball milling to enhance its de/rehydrogenation performance. The hydrogen desorption of MgH2 with 5 wt% Ti-CoO@C started at 185.6 ºC, 160.2 ºC lower than that of pure MgH2. At 275 ºC, the composite rapidly released 6.3 wt% hydrogen within 5 min. The activation energy of hydrogen desorption/absorption of MgH2 + 5 wt%Ti-CoO@C composite was dropped from 169.19 kJ/mol and 83.61 kJ/mol of MgH2 to 137.76 kJ/mol and 35.17 kJ/mol, respectively. In addition, no significant performance degradation was observed in 20 cycles, indicating the excellent stability of the composite. The excellent hydrogen storage performance can be attributed to the homogeneous distribution of the catalyst and in situ generated titanium and MgO, as well as the promoting effect of Mg2Co/Mg2CoH5 as a hydrogen pump. Meanwhile, carbon played a key role in realizing catalyst nanosizing and weakening the Mg-H bond of MgH2, thus enabling the MgH2 + 5 wt%Ti-CoO@C composite to possess an excellent hydrogen storage property.