Jin Guo

Catalytic action of Y2O3@graphene nanocomposites on the hydrogen-storage properties of Mg–Al alloys

An Y2O3@rGO nanocomposite was synthesized via an impregnation method and the catalytic effect of the nanocomposite on the hydrogen-storage properties of a Mg–Al alloy was investigated. The pressure composition isotherm measurement results revealed that the Mg–Al–Y2O3@rGO composite underwent a reversible hydrogenation/dehydrogenation process at 250 °C. Furthermore, the onset temperatures of hydrogenation and dehydrogenation were significantly (i.e., 102 °C and 122 °C, respectively) lower than the respective values corresponding to the Mg–Al alloy. The Y2O3@rGO nanocomposite enhanced the hydriding kinetic properties of the alloy. The hydrogenation kinetic parameter of the Mg–Al alloy increased from 0.008 to 0.195 at 300 °C with 5 wt% of the Y2O3@rGO composite. The values of 162.6 kJ mol−1 H2 and 145.9 kJ mol−1 H2 were obtained for the dehydrogenation energy barrier (evaluated by means of a Kissinger plot) of the Mg–Al alloy and the Mg–Al–Y2O3@rGO hydride, respectively. The reaction enthalpy of hydrogenation/dehydrogenation (determined from a vant Hoff plot) of the alloy decreased with the addition of the Y2O3@rGO nanocomposite. For example, the values of 70.7 kJ mol−1 H2 and 54.3 kJ mol−1 H2 were obtained for the reaction enthalpy of hydrogenation associated with the Mg–Al alloy and the Mg–Al–Y2O3@rGO composite, respectively. Therefore, the addition of the Y2O3@rGO nanocomposite is conducive for improving the thermodynamic and kinetic properties of hydrogenation/dehydrogenation of the Mg–Al alloy.

The effect of La addition on optical transmittance spectra of hydrogenated Mg–La thin films

This paper reported that the transmission of hydrogenated Mg–La films is influenced by the content of La dissolved in Mg. With the increase in La:Mg atomic ratio, the transmission decreases and the short wavelength limit of the transmission spectra shifts toward the long wavelength side. This phenomenon is well explained by using the Lambert–Beer law according to the band gap change, which was calculated using CASTEP module caused by dissolving of La.

Hydrogen Storage Properties of LiNH2/MgH2 Complex Materials with Ti Catalyst by Mechanical Alloying

A LiNH2/MgH2 (1:1) complex was prepared by mechanical alloying and the effects of Ti and TiF3 on the characteristics of hydrogen storage were investigated. It was found that LiMgN and Li2NH phases exist as the main phases in the LiNH2/MgH2 (1:1) complex and that Mg (NH2)2 and NH4HF2 phases appear when TiF3 is added. The onset temperature of hydrogen desorption was reduced with increasing mill time, and the hydrogen saturation absorption temperature for the LiNH2/MgH2 complex decreased about 30°C with the addition of Ti and TiF3. Ti and TiF3 as catalysts are favorable for reducing the dehydrogenation temperature. The addition of TiF3 can also facilitate the increase of hydrogen desorption for the LiNH2/MgH2 (1:1) complex.