Electroless chemical synthesis of magnesium nanomaterials for hydrogen storage: Properties and alternative light activation

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Copyright: Sun, Yahui
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Abstract
Magnesium has been intensively investigated as a promising hydrogen storage material owing to its high storage capacity (7.6 mass%, 110 g L-1), good reversibility and relatively mild operating conditions. Research has been focusing on improving the thermodynamics and kinetics towards practical application via alloying, catalysis and nanosizing. Various synthetic approaches have been developed. In this thesis, investigation was conducted regarding the design and synthesis of magnesium nanomaterials based on the defined research gap. Furthermore, an alternative solution (i.e. light-activated hydrogen storage) has been validated, providing higher potential towards practical application. Initially, basic synthetic methods for magnesium were established, with the identification of the effects of synthetic parameters on the physical properties of the materials. The poor linkage between the particle size/morphology and the hydrogen storage properties suggests the necessity of further reducing the particle size for significant hydrogen storage property improvement. Nanosizing through the introduction of surfactants and matrix/support materials was implemented. Mg nanoparticles of 2-20 nm were obtained in various cases with universally observed hydrogen storage property improvement. However, when stabilised by surfactant (i.e. 1-dodecanethiol), the nanoparticles showed poor stability at elevated temperature. In contrast, superior stability was achieved for magnesium nanoparticles supported on nickel nanobelt and naphthalocyanine (TTBNc), which meanwhile showed higher magnesium loading efficiency as compared to the conventional carbon materials. Significantly improved thermodynamics (H < 53 kJ mol-1 H2) and kinetics (Ea < 70 kJ mol-1 H2) were observed coupling the nanosizing effect and interface interaction. However, the properties of the material still do not fulfil the requirements for practical application, mainly low capacity and still relatively high temperature (~200 C). To avoid the common problems for nanosizing, light-activated hydrogen storage was tested as an alternative solution. The feasibility and universality were proven by the phase transition observed for various hydrides. Further research work is still required to improve the effectiveness of light activation. The research carried out in this thesis provides novel approaches for the design and synthesis of a hydrogen storage system. Through a combination of different solutions (i.e. catalysis, nanosizing and light activation), there is higher potential leading to practical and wide application.
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Author(s)
Sun, Yahui
Supervisor(s)
Aguey-Zinsou, Kondo-Francois
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Publication Year
2018
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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