Keynote
HOW TO REDUCE COST OF METAL HYDRIDES FOR INDUSTRIAL APPLICATIONS

Metal hydrides are considered to be excellent candidates for hydrogen storage applications because of their high hydrogen volumetric density (sometimes higher than in liquid hydrogen) and the possibility to absorb and desorb hydrogen with a small change of hydrogen pressure. One or the main problem to be solved for utilization of metal hydrides in practical applications is cost of the material. In this presentation we will discuss three ways to reduce cost of metal hydrides: element substitution, addition of a second phase, and use of severe plastic deformation techniques.

The Ti-V-Cr compounds usually have are body-centred cubic (BCC) phase and could absorb hydrogen near-room temperature. However, use of pure vanadium makes the cost too prohibitive. We studied the effect of replacing vanadium by low-cost ferrovanadium on the crystal structure and hydrogen storage properties.

Magnesium-based alloys have a high hydrogen storage capacity but their temperature of operation is too high for most applications. Another main problem of these alloys is the slow first hydrogenation, the so-called activation step. We will show that severe plastic deformation (SPD) could make the activation step faster.

The TiFe alloy has a much lower hydrogen capacity than magnesium-based compounds but its temperature of operations is near-room temperature. The activation of this alloy is slow and has to be performed at high temperature thus increasing the production cost. We will show that by doping TiFe with transition metals elements the activation is very fast at even room temperature. For these three systems (Ti-V-Cr, magnesium-based, and TiFe) we will discuss the crystal structures and hydrogen storage properties and assess the hydrogen absorption/desorption mechanism.