Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7706578 | International Journal of Hydrogen Energy | 2018 | 10 Pages |
Abstract
This paper presents a comparative study of H2 absorption and desorption in MgH2 milled with NbF5 or NbH0.9. The addition of NbF5 or NbH0.9 greatly improves hydriding and dehydriding kinetics. After 80 h of milling the mixture of MgH2 with 7 mol.% of NbF5 absorbs 60% of its hydrogen capacity at 250 °C in 30 s, whereas the mixture with 7 mol.% of NbH0.9 takes up 48%, and MgH2 milled without additive only absorbs 2%. At the same temperature, hydrogen desorption in the mixture with NbF5 finishes in 10 min, whereas the mixture with NbH0.9 only desorbs 50% of its hydrogen content, and MgH2 without additive practically does not releases hydrogen. The kinetic improvement is attributed to NbH0.9, a phase observed in the hydrogen cycled MgH2 + NbF5 and MgH2 + NbH0.9 materials, either hydrided or dehydrided. The better kinetic performance of the NbF5-added material is attributed to the combination of smaller size and enhanced distribution of NbH0.9 with more favorable microstructural characteristics. The addition of NbF5 also produces the formation of Mg(HxF1-x)2 solid solutions that limit the practically achievable hydrogen storage capacity of the material. These undesired effects are discussed.
Related Topics
Physical Sciences and Engineering
Chemistry
Electrochemistry
Authors
Santiago A. Pighin, Bruno Coco, Horacio Troiani, Facundo J. Castro, Guillermina Urretavizcaya,