Влияние механического синтеза на десорбцию водорода в композитах на основе гидрида магния и металл-органических структур MIL-101

Abstract

Hydrogen energy is an alternative to the current energy scenario based on fossil fuel consumption, which creates huge economic and environmental problems. In this context, the development of a safe, efficient and economical way to store hydrogen is a necessary step in order to become more competitive with other fuels. Metal hydrides, in particular magnesium hydride MgH2, are a promising method for storing hydrogen, but magnesium hydride has a high desorption activation energy, and a lot of energy must be applied to extract hydrogen. Therefore, it is necessary to develop a technique to reduce this energy. One such method is the synthesis of magnesium hydride with MIL-101 metal-organic framework structures, which makes it possible to lower the activation energy of hydrogen desorption. In the experimental part of the work, composite materials based on MgH2-5 wt % MIL-101(Cr) were obtained. The mechanical synthesis of the MgH2-5 wt. % MIL-101(Cr) composite was carried out in a planetary ball mill with the following parameters: the mass ratio of balls to powder was 20:1, the duration was 60 minutes, and the rotation frequency was 15 Hz. The peak temperature of desorption from magnesium hydride MgH2 is 719 K at a heating rate of 283 K/min. To evaluate the efficiency of hydrogen desorption from the MgH2+MIL-101(Cr) composite, ln(β/Tp2) versus 1000/Tp was plotted (where β is the heating rate and Tp is the temperature of the hydrogen yield peak) for pure MgH2 and the MgH2-5 wt % MIL-101 composite (Cr). The activation energy of hydrogen desorption for the MgH2-5 wt % MIL-101(Cr) composite is 36% lower than for pure magnesium hydride and is (120 ± 2) kJ/mol. This is how a technique for obtaining a composite based on magnesium hydride and MIL-101(Cr) metal-organic framework structures is being developed