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The 2NaBH4+MgH2 and 2NaBH4+MgH2+0.1MFx (M＝Ni, Ti, Zr;x＝2, 3, 4) hydrogen storage composites were prepared by ball milling. The morphology, element distribution, and crystal structure of the composites were detected by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), respectively. In addition, the hydrogen release thermodynamic properties of the materials were tested by differential scanning calorimetry (DSC) and temperature-programmed desorption (TPD). The results show that the peak temperature of the first hydrogen release process for 2NaBH4+MgH2 is decreased by 8.9, 35.7 ℃ and 54.5 ℃ by the addition of NiF2, TiF3 and ZrF4, respectively. In addition, the NaMgF3 phase that appeared during the hydrogen release process changes the reaction path of the first hydrogen release process, and catalyzes the second hydrogen release process of 2NaBH4+MgH2, which reduces the peak temperature of the second dehydrogenation process by 18.0 ℃, 31.1 ℃ and 34.1 ℃, respectively. The quantity ratio of hydrogen release for 2NaBH4+MgH2 reaches 91.7%, 91.9% and 98.7% by the addition of NiF2, TiF3 and ZrF4, respectively. In these three catalysts, ZrF4 shows the best catalytic effect on the entire hydrogen release process of 2NaBH4+MgH2. Therefore, 2NaBH4+MgH2+0.1ZrF4can be used as a potential application system of fuel cell hydrogen supply system.

To reveal the relationship between the crystal structure and the hydrogen desorption activity of MgH2, magnesium-based materials doped with anthracite, molybdenum disulfide, and cobalt were prepared by mechanical ball milling. The relationship between the cell parameters of β-MgH2 and the corresponding dehydrogenation peak temperature was investigated by x-ray diffraction and temperature-programmed desorption. The results show that the unit cell lattice constant a of β-MgH2 is the most critical parameter to determine the dehydrogenation temperature with a negative correlation. With identical material composition, a larger a value leads to a lower dehydrogenation temperature of β-MgH2. The catalytic effect of the three substances on β-MgH2 hydrogen desorption is in the order of Co > anthracite > MoS2. The initial temperature of β-MgH2 hydrogen desorption by cobalt doping is as low as 175 °C. [ABSTRACT FROM AUTHOR]

In this paper, fuel composition and efficiency of solid oxide fuel cell with different methanol pretreating technologies are investigated. High concentrations of H2 and CO can be produced by methanol pretreatment at high temperature, whereas high concentration of methane can be produced at low temperature under the thermodynamic equilibrium condition. For steam reforming of methanol, high cell efficiency can be obtained, whereas for partial oxidation of methanol, the cell efficiency decreases most obviously compared with other pretreating technologies with the increase of O/C ratio. When the O/C ratio is 1.5, the cell efficiencies are 55.89% for steam reforming of methanol, 50.83% for autothermal reforming of methanol, and 45.77% for partial oxidation of methanol at 80% equivalent fuel utilization and 1073 K. When the O/C ratio increases to 2.5, the cell efficiency decreases slowly to 52.01% for steam reforming of methanol, whereas rapidly to 21.68% for partial oxidation of methanol at 80% equivalent fuel utilization and 1073 K. According to the calculated results under the thermodynamic equilibrium condition, suitable pretreating technology and O/C ratio for methanol pretreatment can be selected for the operation of solid oxide fuel cell, which can lead to the high efficiency and good stability of solid oxide fuel cell. [ABSTRACT FROM AUTHOR]