Ternary phase diagram observations revealed that most of the elemental substitutions (e.g., Mn, Co, Cr, Ni, and Zr) resulted in the formation of secondary phases dispersed uniformly in the TiFe-based primary phase, which was unavoidable because of the narrow single-phase region of the TiFe phase. Īvailable studies emphasized the characterization of the TiFe alloy, and only a few attempted to optimize the operation pressure range. The ratio of equilibrium pressure for each step, P 2/ P 1 ( P 1 and P 2 are the equilibrium plateau pressure for TiFe/TiFeH and TiFeH/TiFeH 2, respectively), should be minimized to ensure large usable capacity in a narrow pressure range. Hydrogenation of TiFe proceeds in two steps, sequentially forming TiFeH monohydride and TiFeH 2 dihydride. Second, usable capacity under a practical operation pressure range, e.g., 1 MPa for hydrogen absorption and 0.1 MPa for desorption, must be increased. A high-temperature activation procedure was usually involved for activating pure TiFe. First, the initial hydrogenation, or activation, should be carried out at room temperature.
The two major bottlenecks must be overcome to commercialize TiFe alloy as a room-temperature hydrogen-storage material. The room-temperature hydrogen-storage alloy TiFe is the forerunner in the quest for a suitable medium owing to the abundance of constituting elements and appreciable hydrogen-storage capacity of 1.9 wt.% H near ambient temperature and pressure. The increasing demand for an alternative to fossil fuel has stimulated hydrogen-storage research. It was shown that 3 wt.% Ce dispersion in TiFe alloy imparted to it easy room-temperature (RT) activation properties. At the same time, another issue in TiFe-based alloys, which is a difficulty in activation at room temperature, was solved by Ce addition. 1.5 wt.% of usable capacity within the target pressure range. The effect of V substitution at selective Ti or Fe sublattices was closely analyzed, and the alloy composition Ti 46Fe 47.5V 6.5 displayed the best performance with ca. 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 V substitution for Ti sublattice lowers P 2/ P 1 ratio, where P 1 and P 2 are the equilibrium plateau pressure for TiFe/TiFeH and TiFeH/TiFeH 2, respectively, and thus restricts the two-step hydrogenation within a narrow pressure range. The effect of V addition in TiFe alloy was recently elucidated. 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 2.