An overview of TiFe alloys for hydrogen storage: Structure, processes, properties, and applications

Hydrogen-based energy systems offer potential solutions for replacing fossil fuels in the future. However, the practical utilization of hydrogen energy depends partly on safe and efficient hydrogen storage techniques. The development of hydrogen storage materials has attracted extensive interest for decades. Solid-state hydrogen storage systems based on metal hydride materials provide great promises for many applications. Recently, in-terest has been revived in TiFe alloys as a prime candidate for stationary hydrogen storage material. The ad-vantages of TiFe alloys over some of the other solid metal hydrides include that it can hydrogenate and dehydrogenate at near room temperature under near atmospheric pressures and that it is a low-cost material because there are abundant supplies of Fe and Ti on the earth's crust. However, the TiFe alloy must be activated at relatively high temperatures (400-450 degrees C) and high pressure of hydrogen (65 bar) before it can be hydro-genated, which is a hindrance to the industrial-scale application of TiFe alloys. The materials science community on hydrogen storage materials has conducted and reported considerable amounts of studies on TiFe-based alloys. In this work, we provided a comprehensive review of TiFe-based alloys. The fundamentals and synthesis ap-proaches of TiFe-based alloys were summarized. The activation properties of TiFe-based alloys including the understanding of the activation mechanisms and the methods for improving the activation kinetics were reviewed. Moreover, the cycle stability and anti-poisoning ability were discussed. Finally, the potential appli-cations and the perspective of TiFe-based alloys were introduced.