Abstract
NaMgH3 perovskite hydride and NaMgH3–carbon nanomaterials (NH-CM) composites were prepared via the reactive ball-milling method. To investigate the catalytic effect of CM on the dehydriding kinetic properties of NaMgH3 hydride, multiwall carbon nanotubes (MWCNTs) and graphene oxide (GO) were used as catalytic additives. It was found that dehydriding temperatures and activation energies (ΔE1 and ΔE2) for two dehydrogenation steps of NaMgH3 hydride can be greatly reduced with a 5 wt. % CM addition. The NH–2.5M–2.5G composite presents better dehydriding kinetics, a lower dehydriding temperature, and a higher hydrogen-desorbed amount (3.64 wt. %, 638 K). ΔE1 and ΔE2 can be reduced by about 67 kJ/mol and 30 kJ/mol, respectively. The results suggest that the combination of MWCNTs and GO is a better catalyst as compared to MWCNTs or GO alone.
Highlights
Perovskite-type hydride, NaMgH3, as a potential candidate for on-board applications, has received considerable attention for its high gravimetric and volumetric hydrogen densities (6 wt. %and 88 kg/m3, respectively), as well as its reversible hydriding and dehydriding reactions [1,2,3,4,5,6,7].NaMgH3 is characterized by an orthorhombic perovskite structure comprising [MgH6 ] octahedra and [NaH12 ] cubo-octahedra, which is analogous to GdFeO3 -type perovskite.This space group is typical for low-tolerance-factor oxide perovskites, where the singly chargedNa cation occupies eight-fold coordinated voids [8]
The are peaks of the catalysts are absent, because were added to the composites, and these additives were appeared in the form of an amorphous only a small amount of carbon nanomaterial (CM) were added to the composites, and these additives were appeared in the phase after
NaMgH3 perovskite hydride and NH-CM composites were prepared via the reactive ball-milling method under a H2 atmosphere
Summary
Perovskite-type hydride, NaMgH3 , as a potential candidate for on-board applications, has received considerable attention for its high gravimetric and volumetric hydrogen densities NaMgH3 is characterized by an orthorhombic perovskite structure comprising [MgH6 ] octahedra and [NaH12 ] cubo-octahedra, which is analogous to GdFeO3 -type perovskite (space group Pnma). This space group is typical for low-tolerance-factor oxide perovskites, where the singly charged. Sheppard et al [9] reported the desorption enthalpy and entropy are 86.6 ± 1.0 kJ/(mol·H2 ) and 132.2 ± 1.3 kJ/(mol·H2 ) for the decomposition of NaMgH3 into NaH and Mg, respectively, indicating that NaMgH3 is thermodynamically more stable than magnesium hydride (MgH2 ). The effects of different additives on the structure, thermal stability, and dehydriding kinetic properties of NaMgH3 hydride were investigated
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