Structure, Microstructure and Hyperfine Interactions in Hf- and Ni-Substituted TiFe Alloy for Hydrogen Storage

Hydrogen storage in metallic materials is of utmost importance for hydrogen energy applications. In this paper, we address the issue of finding cost-effective materials for large-scale usage. One such material is TiFe, which requires high H2 pressure and temperature above 400°C to activate and start reversibly absorbing/desorbing hydrogen. To facilitate the aforementioned processes, the alloy must be subjected to doping by other elements. We report research on the Ti1-xHfxFe1-yNiy compounds and their hydrides investigated by means of X-ray diffraction, electron microscopy, and Mössbauer spectroscopy. The data show that for Ti0.9Hf0.1Fe0.9Ni0.1, the activation temperature is reduced to 200°C, with a slightly reduced total hydrogen absorption. According to Mössbauer spectroscopy results, hydrogenation of the synthesized alloys leads to a significant decrease in the electronic state of the compounds, as could be expected for hydrides. It also proves the existence of structural disorder introduced to facilitate the activation of the alloys, complementary to X-ray diffraction and electron microscopy.