| Summary: | Titanium iron (TiFe) alloy is a room-temperature hydrogen-storage material, and it absorbs hydrogen via a two-step process to form TiFeH and then TiFeH<sub>2</sub>. The effect of V addition in TiFe alloy was recently elucidated. The V substitution for Ti sublattice lowers <i>P</i><sub>2</sub>/<i>P</i><sub>1</sub> ratio, where <i>P</i><sub>1</sub> and <i>P</i><sub>2</sub> are the equilibrium plateau pressure for TiFe/TiFeH and TiFeH/TiFeH<sub>2</sub>, respectively, and thus restricts the two-step hydrogenation within a narrow pressure range. The focus of the present investigation was to optimize the V content such that maximum usable storage capacity can be achieved for the target pressure range: 1 MPa for absorption and 0.1 MPa for desorption. The effect of V substitution at selective Ti or Fe sublattices was closely analyzed, and the alloy composition Ti<sub>46</sub>Fe<sub>47.5</sub>V<sub>6.5</sub> displayed the best performance with ca. 1.5 wt.% of usable capacity within the target pressure range. At the same time, another issue in TiFe-based alloys, which is a difficulty in activation at room temperature, was solved by Ce addition. It was shown that 3 wt.% Ce dispersion in TiFe alloy imparted to it easy room-temperature (RT) activation properties.
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