Hydrogen release: In-situ calorimetry studies of NaBH4+2MgH2 doped by ZrF4
In this work, NaBH 4 +2MgH 2 doped by ZrF 4 was prepared by the ball-milling method. The structure and the morphology of different systems were characterized by X-ray diffraction and scanning electron microscopy. The thermodynamic properties of hydrogen release were determined by temperature-programmed desorption and differential scanning calorimetry . Hydrogen desorption kinetic properties and hydrogen content were investigated by pressure composition isothermal method. The main objective of this work was to study the relationship between the heat of hydrogen release and the quantity of hydrogen released by In-situ calorimetry measurement. The NaBH 4 +2MgH 2 +0.1ZrF 4 can release about 7.4 wt.% H 2 by two steps. Firstly, the heat of hydrogen release of the first and the second steps were lower by 480.82 J·g −1 and 430.8 J·g −1 than that of NaBH 4 +2MgH 2 , respectively. And the dehydrogenation enthalpy of NaBH 4 +2MgH 2 went from −243.81 kJ·mol −1 to −191.2 kJ·mol −1 . Secondly, the addition of ZrF 4 can improve the hydrogen release kinetic property of NaBH 4 +2MgH 2 , which can release 5 wt.% H 2 in 2.5 h at 385 °C under 0.01 MPa hydrogen pressure. Therefore, NaBH 4 +2MgH 2 +0.1ZrF 4 will be a potential candidate as a fuel cell hydrogen supply system.
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