Jump to main content
Jump to site search
PLANNED MAINTENANCE Close the message box

Scheduled maintenance work on Wednesday 27th March 2019 from 11:00 AM to 1:00 PM (GMT).

During this time our website performance may be temporarily affected. We apologise for any inconvenience this might cause and thank you for your patience.


Issue 26, 2012
Previous Article Next Article

Enhanced reversibility of H2 sorption in nanoconfined complex metal hydrides by alkali metal addition

Author affiliations

Abstract

Complex metal hydrides, containing up to 18 wt% H2, are attractive candidates for on-board hydrogen storage. However, only limited reversibility of H2 desorption is achieved under mild conditions, especially in the absence of catalysts. Nanoconfining the materials in porous matrixes facilitates rehydrogenation, but still full reversibility has been rarely achieved. We reveal the factors that limit the reversibility using NaAlH4 in a porous carbon matrix as a model system. Relatively large Al crystallites (>100 nm) are formed after desorption, migrating out of the mesopores of the matrix. However, their formation does not fundamentally limit the reversibility, as these crystallites react with Na(H) and H2 reforming nanoconfined NaAlH4 under relatively mild conditions. We show for the first time that the main limiting factor for the decayed cycling capacity is the loss of active alkali metal species. Evaporation losses are minor, even when dehydrogenating at 325 °C in vacuum. Significant losses (30–40%) occur upon the first hydrogen desorption run, and are attributed to the reaction of Na species with impurities in the carbon matrix. A one-time addition of extra Na compensates for this loss, leading to close to full reversibility (>90%) at 150 °C under 55 bar H2 pressure. A similar effect is found when adding extra Li species to nanoconfined LiBH4. For nanoconfined complex metal hydrides irreversible loss of the reactive alkali metal species due to reaction with impurities can act as a major loss mechanism. However, the one-time addition of extra alkali metal species is very effective in resolving this issue, leading to close to full cycling reversibility under relatively mild conditions even in the absence of catalysts.

Graphical abstract: Enhanced reversibility of H2 sorption in nanoconfined complex metal hydrides by alkali metal addition

Back to tab navigation

Supplementary files

Publication details

The article was received on 20 Feb 2012, accepted on 01 May 2012 and first published on 01 May 2012


Article type: Paper
DOI: 10.1039/C2JM31064C
Citation: J. Mater. Chem., 2012,22, 13209-13215

  •   Request permissions

    Enhanced reversibility of H2 sorption in nanoconfined complex metal hydrides by alkali metal addition

    J. Gao, P. Ngene, I. Lindemann, O. Gutfleisch, K. P. de Jong and P. E. de Jongh, J. Mater. Chem., 2012, 22, 13209
    DOI: 10.1039/C2JM31064C

Search articles by author

Spotlight

Advertisements