Cycling hydrogen desorption properties and microstructures of MgH ₂ –AlH ₃ –NbF ₅ hydrogen storage materials

Abstract

Abstract Magnesium hydride (MgH 2 ) is a candidate material for hydrogen storage. MgH 2 –AlH 3 composite shows superior hydrogen desorption properties than pure MgH 2 . However, this composite still suffers from poor cycling performance. In this work, NbF 5 was utilized to improve the cycling properties of the MgH 2 –AlH 3 composite. Cycling hydrogen desorption studies show that NbF 5 significantly improves the cycling stability of MgH 2 –AlH 3 . The MgH 2 –AlH 3 –NbF 5 composite can release about 2.7 wt% of hydrogen at 300 °C for 1 h and the hydrogen desorption capacity can maintain at 2.7 wt% for more than 100 cycles. In comparison, the hydrogen desorption capacity of the MgH 2 –AlH 3 composite is decreasing with the cycle number increasing. The capacity is reduced from a maximum value of 3.3 wt% to about 1.0 wt% after 40 cycles. Brunauer–Emmett–Teller (BET) surface area measurements show that the particle size of MgH 2 –AlH 3 composite decreases after cycling, which means pulverization of the composite. NbF 5 can to some extent suppress the pulverization of the composite during cycling, which partially contributes to the improvement of the cycling hydrogen desorption properties of the material.