Superior de/hydrogenation performances of MgH2 catalyzed by 3D flower-like TiO2@C nanostructures
Magnesium hydride has been seen as a potential material for solid state hydrogen storage , but the kinetics and thermodynamics obstacles have hindered its development and application. Three-dimensional flower-like TiO 2 @C and TiO 2 were synthesized as the catalyst for MgH 2 system and great catalytic activities are acquired in the hydrogen sorption properties. Experiments also show that the flower-like TiO 2 @C is superior to flower-like TiO 2 in improving the hydrogen storage properties of MgH 2 . The hydrogen desorption onset and peak temperatures of flower-like TiO 2 doped MgH 2 is reduced to 199.2 °C and 245.4 °C, while the primitive MgH 2 starts to release hydrogen at 294.6 °C and the rapid dehydrogenation temperature is even as high as 362.6 °C. The onset and peak temperatures of flower-like TiO 2 @C doped MgH 2 are further reduced to 180.3 °C and 233.0 °C. The flower-like TiO 2 @C doped MgH 2 composite can release 6.0 wt% hydrogen at 250 °C within 7 min, and 4.86 wt% hydrogen at 225 °C within 60 min, while flower-like TiO 2 doped MgH 2 can release 6.0 wt% hydrogen at 250 °C within 8 min, and 3.89 wt% hydrogen at 225 °C within 60 min. Hydrogen absorption kinetics is also improved dramatically. Moreover, compared with primitive MgH 2 and the flower-like TiO 2 doped MgH 2 , the activation energy of flower-like TiO 2 @C doped MgH 2 is significantly decreased to 67.10 kJ/mol. All the improvement of hydrogen sorption properties can be ascribed to the flower-like structure and the two-phase coexistence of TiO 2 and amorphous carbon . Such phase composition and unique structure are proved to be the critical factor to improve the hydrogen sorption properties of MgH 2 , which can be considered as the new prospect for improving the kinetics of light-metal hydrogen storage materials.
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