Influence of Nanosized CoTiO 3 Synthesized via a Solid-State Method on the Hydrogen Storage Behavior of MgH 2 .

Magnesium hydride (MgH 2 ) has received outstanding attention as a safe and efficient material to store hydrogen because of its 7.6 wt.% hydrogen content and excellent reversibility. Nevertheless, the application of MgH 2 is obstructed by its unfavorable thermodynamic stability and sluggish sorption kinetic. To overcome these drawbacks, ball milling MgH 2 is vital in reducing the particle size that contribute to the reduction of the decomposition temperature. However, the milling process would become inefficient in reducing particle sizes when equilibrium between cold-welding and fracturing is achieved. Therefore, to further ameliorate the performance of MgH 2 , nanosized cobalt titanate (CoTiO 3 ) has been synthesized using a solid-state method and was introduced to the MgH 2 system. The different weight percentages of CoTiO 3 were doped to the MgH 2 system, and their catalytic function on the performance of MgH 2 was scrutinized in this study. The MgH 2 + 10 wt.% CoTiO 3 composite presents the most outstanding performance, where the initial decomposition temperature of MgH 2 can be downshifted to 275 °C. Moreover, the MgH 2 + 10 wt.% CoTiO 3 absorbed 6.4 wt.% H 2 at low temperature (200 °C) in only 10 min and rapidly releases 2.3 wt.% H 2 in the first 10 min, demonstrating a 23-times-faster desorption rate than as-milled MgH 2 at 300 °C. The desorption activation energy of the 10 wt.% CoTiO 3 -doped MgH 2 sample was dramatically lowered by 30.4 kJ/mol compared to undoped MgH 2 . The enhanced performance of the MgH 2 -CoTiO 3 system is believed to be due to the in situ formation of MgTiO 3 , CoMg 2 , CoTi 2 , and MgO during the heating process, which offer a notable impact on the behavior of MgH 2 .