HYDROGEN SORPTION IMPROVEMENT OF NaAlH4 CATALYSED BY K2SiF6 FOR SOLID STATE HYDROGEN STORAGE

• Published in: Journal of Sustainability Science and Management
• Main Author: Omar Z.; Zuridi A.N.; Mustafa N.S.M.; Yahya M.S.; Ismail M.
• Format: Article
• Language: English
• Published: Universiti Malaysia Terengganu 2024
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85193467048&doi=10.46754%2fjssm.2024.04.004&partnerID=40&md5=0878d7ee1a9305105ea4cd27ccdf6021

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. © UMT Press