Abstract
Establishing a viable hydrogen economy can help reduce the dependence on finite fossil fuels and unstable non-conventional energy sources. Safe and efficient methods to store hydrogen is critical to this. Storing hydrogen in the form of solid metal hydrides is better in terms of volume and energy efficiency compared to gaseous or liquid hydrogen storage methods. Aotearoa New Zealand has substantial titanomagnetite ore deposits rich in Ti and Fe intermetallic compounds, which show great potential for hydride-based storage. However, the presence of impurities in these natural ores raises important questions about how they impact hydrogen storage behaviour and performance. Notably, several studies have shown that recycled hydrogen storage alloys containing dopants can exhibit comparable or even enhanced hydriding performance. To fully understand the potential benefits and implications of such impurities in TiFe alloys, the nanoscale processes involved in the hydrogenation and dehydrogenation of these doped materials must be studied. This requires extensive computational modelling, as existing models often overlook impurities and assume ideal behaviour, limiting their applicability to real situations. This study focuses on the computational modelling of iron-titanium hydride doped with impurities, specifically silicon. We employ the calculation of phase diagrams (CALPHAD) approach, supported by density functional theory (DFT), to investigate the hydrogenation behaviour of Si-doped TiFe. By optimizing alloy composition and processing requirements through such modelling, we aim to enhance hydrogen storage performance and leverage the potential benefits of impurities in these materials.
