Thermodynamic performance of 2NaBH4+MgH2 hydrogen storage system improved by transition metal fluoride

Abstract

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.

Keywords

• metal fluoride
• 2nabh4+mgh2
• mechanical ball milling method
• thermodynamic stability