Microstructural and Kinetic Investigation of Hydrogen Sorption Reaction of MgH₂/Nb₂O₅ Nanopowders

Abstract

MgH₂/Nb₂O₅ composite is one of the most promising candidates for the hydrogen delivery. The performances of these materials are usually improved by mechanical milling because a finer distribution of the catalyst and the induction of defects on the particles accelerate the hydrogen sorption kinetic of the powders. Aiming at elucidating the factors responsible for this improvement, the effect on the reaction kinetics induced by nanometric and micrometric Nb₂O₅ powders has been investigated by a Sievert type apparatus. Nanometric additive imparts excellent performances in comparison to the micrometric one. The activation of the sample by sorption cycling has been investigated. In order to elucidate the role of the catalyst, a metallographic study of partially desorbed MgH₂/Nb₂O₅ composite has been applied for the first time. The powders have been also characterized by X-ray diffraction and thermal gravimetric analysis.

Keywords:

• Hydrogen storage
• Kinetics
• Magnesium hydride
• Mechanical milling
• Niobium oxide
• Scanning electron microscopy

ACKNOWLEDGMENTS

The financial support from the Italian Ministry of Research through the project TEPSI is gratefully acknowledged.