Enhanced hydrogen absorption and desorption properties of MgH2 with graphene and vanadium disulfide

Abstract

Magnesium hydride (MgH2) is the most prominent carrier for storing hydrogen in solid-state mode. However, their slow kinetics and high thermodynamics become an obstacle in hydrogen storage. The present study elaborates on the catalytic effect of graphene (Gr) and vanadium disulfide (VS2) on MgH2 to enhance its hydrogen sorption kinetic. The temperature-programmed desorption study shows that the onset desorption temperature of MgH2 catalyzed by VS2 and MgH2 catalyzed by Gr is 289 °C and 300 °C, respectively. These desorption temperatures are 87 °C and 76 °C lower than the desorption temperature of pristine MgH2. The rapid rehydrogenation kinetics for the MgH2 catalyzed by VS2 have been found at a temperature of 300 °C under 15 atm H2 pressure by absorbing ∼4.04 wt% of hydrogen within 1 min, whereas the MgH2 catalyzed by Gr takes ∼3 min for absorbing the same amount of hydrogen under the similar temperature and pressure conditions. The faster release of hydrogen was also observed in MgH2 catalyzed by VS2 than MgH2 catalyzed by Gr and pristine MgH2. MgH2 catalyzed by VS2 releases ∼2.54 wt% of hydrogen within 10 min, while MgH2 catalyzed by Gr takes ∼30 min to release the same amount of hydrogen. Furthermore, MgH2 catalyzed by VS2 also persists in the excellent cyclic stability and reversibility up to 25 cycles.