The effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride
MgH2 is considered to be one of the most promising options for a solid state hydrogen storage material. For practical use it is still imperative to find a convenient means of overcoming its slow kinetics and high stability. In this investigation, a range of binary and ternary metal oxides of alumini...
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| Format: | Thesis (University of Nottingham only) |
| Language: | English |
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2007
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| Online Access: | https://eprints.nottingham.ac.uk/12320/ |
| _version_ | 1848791476461371392 |
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| author | Croston, Deborah Louise |
| author_facet | Croston, Deborah Louise |
| author_sort | Croston, Deborah Louise |
| building | Nottingham Research Data Repository |
| collection | Online Access |
| description | MgH2 is considered to be one of the most promising options for a solid state hydrogen storage material. For practical use it is still imperative to find a convenient means of overcoming its slow kinetics and high stability. In this investigation, a range of binary and ternary metal oxides of aluminium, silicon, titanium, and zirconium, as well as Pd-modified Ti02 samples, were prepared and characterised. The prepared oxides were ball milled with MgH2, and the hydrogen sorption behaviour of the ball milled mixtures was investigated using DSC-TGA-MSS, Sieverts and IGA. Thermodynamic parameters including enthalpies and entropies of hydrogen desorption were determined from experimental data, and activation energy calculations along with modelling of the kinetics were used to understand the mechanism and rate-limiting step of dehydrogenation.
Oxide components, calcination temperature, and surface area were found to have a significant impact on the hydrogen sorption behaviour of MgH2 in the ball milled mixtures. Of the prepared binary and ternary oxides, Ti02 and mixed oxides with a Ti02 component were found to lower the dehydrogenation onset temperature by as much as 100°C, while additions of Pd-modified Ti02 resulted in the lowest dehydrogenation onset temperature of 205°C, compared to 360°C for ball milled MgH2. In addition, rates of hydrogen desorption and absorption were significantly increased as a result of the Ti02 and Ti02 - Pd additives. Dehydrogenation of 90 % of the full H2 capacity took 6 min at 300°C, compared to 230 min for milled MgH2 at 350°C.
It was found that a reduction of the Ti02 oxide resulted in the active species responsible for the enhanced dehydrogenation behaviour. Through analysis of the reaction kinetics, the mechanism of dehydrogenation was found to change from a surface controlled, contracting volume model for ball milled MgH2 to one of a Johnson-Mehl-Avrami model of two - dimensional nucleation and growth upon addition of Ti02 and Ti02 - Pd. |
| first_indexed | 2025-11-14T18:29:07Z |
| format | Thesis (University of Nottingham only) |
| id | nottingham-12320 |
| institution | University of Nottingham Malaysia Campus |
| institution_category | Local University |
| language | English |
| last_indexed | 2025-11-14T18:29:07Z |
| publishDate | 2007 |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | nottingham-123202025-02-28T11:18:39Z https://eprints.nottingham.ac.uk/12320/ The effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride Croston, Deborah Louise MgH2 is considered to be one of the most promising options for a solid state hydrogen storage material. For practical use it is still imperative to find a convenient means of overcoming its slow kinetics and high stability. In this investigation, a range of binary and ternary metal oxides of aluminium, silicon, titanium, and zirconium, as well as Pd-modified Ti02 samples, were prepared and characterised. The prepared oxides were ball milled with MgH2, and the hydrogen sorption behaviour of the ball milled mixtures was investigated using DSC-TGA-MSS, Sieverts and IGA. Thermodynamic parameters including enthalpies and entropies of hydrogen desorption were determined from experimental data, and activation energy calculations along with modelling of the kinetics were used to understand the mechanism and rate-limiting step of dehydrogenation. Oxide components, calcination temperature, and surface area were found to have a significant impact on the hydrogen sorption behaviour of MgH2 in the ball milled mixtures. Of the prepared binary and ternary oxides, Ti02 and mixed oxides with a Ti02 component were found to lower the dehydrogenation onset temperature by as much as 100°C, while additions of Pd-modified Ti02 resulted in the lowest dehydrogenation onset temperature of 205°C, compared to 360°C for ball milled MgH2. In addition, rates of hydrogen desorption and absorption were significantly increased as a result of the Ti02 and Ti02 - Pd additives. Dehydrogenation of 90 % of the full H2 capacity took 6 min at 300°C, compared to 230 min for milled MgH2 at 350°C. It was found that a reduction of the Ti02 oxide resulted in the active species responsible for the enhanced dehydrogenation behaviour. Through analysis of the reaction kinetics, the mechanism of dehydrogenation was found to change from a surface controlled, contracting volume model for ball milled MgH2 to one of a Johnson-Mehl-Avrami model of two - dimensional nucleation and growth upon addition of Ti02 and Ti02 - Pd. 2007-07-13 Thesis (University of Nottingham only) NonPeerReviewed application/pdf en arr https://eprints.nottingham.ac.uk/12320/1/442309.pdf Croston, Deborah Louise (2007) The effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride. PhD thesis, University of Nottingham. Metallic oxides Hydrogen sorption behaviour Ball milled mixtures Dehydrogenation Hydrogen storage |
| spellingShingle | Metallic oxides Hydrogen sorption behaviour Ball milled mixtures Dehydrogenation Hydrogen storage Croston, Deborah Louise The effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride |
| title | The effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride |
| title_full | The effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride |
| title_fullStr | The effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride |
| title_full_unstemmed | The effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride |
| title_short | The effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride |
| title_sort | effect of metal oxide additives on the hydrogen sorption behaviour of magnesium hydride |
| topic | Metallic oxides Hydrogen sorption behaviour Ball milled mixtures Dehydrogenation Hydrogen storage |
| url | https://eprints.nottingham.ac.uk/12320/ |