Superior de/hydrogenation performances of MgH2 catalyzed by 3D flower-like TiO2@C nanostructures

Abstract

Abstract 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 TiO2@C and TiO2 were synthesized as the catalyst for MgH2 system and great catalytic activities are acquired in the hydrogen sorption properties. Experiments also show that the flower-like TiO2@C is superior to flower-like TiO2 in improving the hydrogen storage properties of MgH2. The hydrogen desorption onset and peak temperatures of flower-like TiO2 doped MgH2 is reduced to 199.2 °C and 245.4 °C, while the primitive MgH2 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 TiO2@C doped MgH2 are further reduced to 180.3 °C and 233.0 °C. The flower-like TiO2@C doped MgH2 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 TiO2 doped MgH2 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 MgH2 and the flower-like TiO2 doped MgH2, the activation energy of flower-like TiO2@C doped MgH2 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 TiO2 and amorphous carbon. Such phase composition and unique structure are proved to be the critical factor to improve the hydrogen sorption properties of MgH2, which can be considered as the new prospect for improving the kinetics of light-metal hydrogen storage materials.