A sustainable economy built on renewable energy relies on hydrogen for storing energy and replacing fossil fuels. An efficient way to store hydrogen is to keep it in the solid state by binding it chemically in a metal hydride, such as TiFe-Hydride, which is particularly useful for seasonal energy storage or for applications where safety is a concern. TiFe, which forms an interstitial metal hydride, is one of the very few alloys that have made it to commercial application as a hydrogen storage material. Since experimental studies with hydrogen can be challenging and time-consuming, computational tools are extremely valuable for gaining a deeper understanding of the processes underlying the (de-)hydrogenation reaction.
In this contribution, I will present the results of a trilateral collaboration between researchers in Germany, New Zealand, and the USA, that delivered insights into TiFe for hydrogen storage from first-principles modelling. Calculations based on density functional theory (DFT) allowed us to decouple the chemical and mechanical contributions to the interface energy, accurately predicting the morphology of the nucleating hydride phase.[1] DFT calculations also provided us with preferential substitution sites for alloying elements,[2] which we used to build thermodynamic models that explain the loss in storage capacity with different impurities.[3] Finally, calculated defect formation energies in the associated oxides help us to understand the barriers to activating TiFe as well as the pathway to producing TiFe from ilmenite sands.[4] Overall, this work shows how first-principles modelling can inform the design of metal hydrides for hydrogen storage, complementing and sometimes replacing more time-consuming experimental research.