Hydrogen sorption improvement of NaAIH₄ catalysed by k₂SiF₆ for solid state hydrogen storage

Zarina Omar, . and Anis Nabilah Zuridi, . and Nurul Shafikah Mohd Mustafa, . and Muhammad Syarifuddin Yahya, . and Mohammad Ismail, . (2024) Hydrogen sorption improvement of NaAIH₄ catalysed by k₂SiF₆ for solid state hydrogen storage. Journal of Sustainability Science and Management (Malaysia), 19 (4). pp. 36-45. ISSN 2672-7226

Sodium alanate (NaAlH₄) has been recognised as a complex metal hydride that is frequently used as a hydrogen storage material. However, dealing with its poor kinetic characteristics and high decomposition temperatures becomes challenging. This research added potassium hexafluorosilicate (K₂SiF₆) as a catalyst to reduce the dehydrogenation temperature and improve sorption kinetics compared to the undoped NaAlH₄. The dehydrogenation temperature of the NaAlH₄ composite with 10 wt.% K₂SiF₆ addition was determined to be 145 °C, a decrease of about 31% compared to 210 °C for the undoped NaAlH₄. The 10 wt.% K₂SiF₆-added NaAlH₄ samples released roughly 1.77 wt.% hydrogen at 200 °C after 60 minutes of dehydrogenation, representing faster dehydrogenation kinetics, but the milled NaAlH₄ only produced around 1.39 wt.% of hydrogen. According to Kissinger’s analysis, the apparent activation energy, Eₐ for the decomposition of NaAlH₄ was 87.74 kJ/mol in 1st stage and for NaAlH₄-10 wt.% K₂SiF₆ composite, lowered by 30.45 kJ/mol or 25.8% than as-milled NaAlH₄ (118.19 kJ/mol). The enhancement of the dehydrogenation performance of the NaAlH₄-K₂SiF₆ composite can be attributed to the formation of the new phases of KAlF₄. These findings might alter the reaction pathway of the composite system and improve its thermodynamic properties. The improvement of dehydrogenation performance and the discovery of the role played by KAlF₄ in the dehydrogenation process of the NaAlH₄-K₂SiF₆ composite give us valuable insights for developing and optimising future hydrogen storage materials.

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Abstract

Sodium alanate (NaAlH₄) has been recognised as a complex metal hydride that is frequently used as a hydrogen storage material. However, dealing with its poor kinetic characteristics and high decomposition temperatures becomes challenging. This research added potassium hexafluorosilicate (K₂SiF₆) as a catalyst to reduce the dehydrogenation temperature and improve sorption kinetics compared to the undoped NaAlH₄. The dehydrogenation temperature of the NaAlH₄ composite with 10 wt.% K₂SiF₆ addition was determined to be 145 °C, a decrease of about 31% compared to 210 °C for the undoped NaAlH₄. The 10 wt.% K₂SiF₆-added NaAlH₄ samples released roughly 1.77 wt.% hydrogen at 200 °C after 60 minutes of dehydrogenation, representing faster dehydrogenation kinetics, but the milled NaAlH₄ only produced around 1.39 wt.% of hydrogen. According to Kissinger’s analysis, the apparent activation energy, Eₐ for the decomposition of NaAlH₄ was 87.74 kJ/mol in 1st stage and for NaAlH₄-10 wt.% K₂SiF₆ composite, lowered by 30.45 kJ/mol or 25.8% than as-milled NaAlH₄ (118.19 kJ/mol). The enhancement of the dehydrogenation performance of the NaAlH₄-K₂SiF₆ composite can be attributed to the formation of the new phases of KAlF₄. These findings might alter the reaction pathway of the composite system and improve its thermodynamic properties. The improvement of dehydrogenation performance and the discovery of the role played by KAlF₄ in the dehydrogenation process of the NaAlH₄-K₂SiF₆ composite give us valuable insights for developing and optimising future hydrogen storage materials.

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Item Type:	Article
AGROVOC Term:	hydrogen
AGROVOC Term:	catalysts
AGROVOC Term:	thermal analysis
AGROVOC Term:	solid state fermentation
AGROVOC Term:	research data
Geographical Term:	Malaysia
Uncontrolled Keywords:	Hydrogen storage, Metal hydrides, Potassium hexafluorosilicate (K2SiF6)
Depositing User:	Mr. Khoirul Asrimi Md Nor
Date Deposited:	10 Mar 2025 03:36
Last Modified:	10 Mar 2025 03:36
URI:	http://webagris.upm.edu.my/id/eprint/2482

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