Atomistic Modelling of Materials for Clean Energy Applications : hydrogen generation, hydrogen storage, and Li-ion battery

Abstract: In this thesis, a number of clean-energy materials for hydrogen generation, hydrogen storage, and Li-ion battery energy storage applications have been investigated through state-of-the-art density functional theory.As an alternative fuel, hydrogen has been regarded as one of the promising clean energies with the advantage of abundance (generated through water splitting) and pollution-free emission if used in fuel cell systems. However, some key problems such as finding efficient ways to produce and store hydrogen have been hindering the realization of the hydrogen economy. Here from the scientific perspective, various materials including the nanostructures and the bulk hydrides have been examined in terms of their crystal and electronic structures, energetics, and different properties for hydrogen generation or hydrogen storage applications. In the study of chemisorbed graphene-based nanostructures, the N, O-N and N-N decorated ones are designed to work as promising electron mediators in Z-scheme photocatalytic hydrogen production. Graphene nanofibres (especially the helical type) are found to be good catalysts for hydrogen desorption from NaAlH4. The milestone nanomaterial, C60, is found to be able to significantly improve the hydrogen release from the (LiH+NH3) mixture. In addition, the energetics analysis of hydrazine borane and its derivative solid have revealed the underlying reasons for their excellent hydrogen storage properties. As the other technical trend of replacing fossil fuels in electrical vehicles, the Li-ion battery technology for energy storage depends greatly on the development of electrode materials. In this thesis, the pure NiTiH and its various metal-doped hydrides have been studied as Li-ion battery anode materials. The Li-doped NiTiH is found to be the best candidate and the Fe, Mn, or Cr-doped material follows.