Abstract
The shift toward a sustainable hydrogen economy is critical for reducing dependence on both finite fossil fuels and the unpredictability of renewable energy sources. A significant obstacle in
this transition is the creation of safe and efficient hydrogen storage technologies. Solid-state hydrogen storage using metal hydrides, such as TiFe alloys, provides notable advantages in both energy and space efficiency when compared to gaseous or liquid forms. Aotearoa New Zealand’s abundant
titanomagnetite ore deposits, rich in titanium and iron compounds, offer great potential for hydride-based storage solutions. However, naturally occurring impurities in these ores bring forth essential questions regarding their impact on storage performance:
· How do these impurities influence the material's hydrogen storage capacity?
· What degree of purity is required in TiFe alloys to strike a balance between cost-effectiveness
and performance efficiency?
To explore these questions, we focus on the nanoscale mechanisms governing hydrogenation and dehydrogenation in silicon-doped TiFe alloys. Using the Effective Bond Energy Formalism (EBEF)
within a CALPHAD framework, supplemented by density functional theory (DFT), we investigate the effects of silicon and other impurities on the hydrogen storage properties of TiFe alloys. The EBEF model simplifies the computational load by concentrating on binary interactions, enabling a deeper
understanding of complex systems, including the critical Laves phases found in Si-doped TiFe alloys. The presence of Laves phases, with their unique structures, imposes kinetic limitations on the hydrogenation process, making them pivotal to understanding hydrogen storage behavior. In this study, we present the behavior of these Laves phases in TiFeSi systems, as calculated through EBEF/CALPHAD methodologies, and compare their thermodynamics to that of pure TiFe alloys. This work provides valuable insights into how silicon and other impurities affect the hydrogen storage capabilities of TiFe alloys, contributing to the development of cost-efficient, high-performance metal
hydrides for hydrogen storage applications, and potentially utilizing naturally occurring impurities as a resource.
