EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In the framework of the European project HyCARE, supported by FCH-JU, the TiFe0.85Mn0.05 alloy has been selected to store ≈ 45 kg of H2 as metal hydride carrier (MH). The aim of the project is to store H2 produced by renewables for large-scale smart-grid applications, including the use of Phase Change Material for the heat management of the MH-tanks.
In this work, results obtained by different laboratories on the characterization of the hydrogen carrier are reported. First, GKN produced a batch of 5 kg of TiFe0.85Mn0.05 in powder, by crushing. A distribution of particle sizes was obtained, with values < 420µm. For this sample, beside the main TiFe0.85Mn0.05 cubic phase, Ti4Fe2O0.4, β-Ti80(FeMn)20 and a Fe-rich phase are also present as secondary phases. An activation method, suitable to be performed on site in the final plant, has been developed. The alloy can be activated by one hydrogen sorption cycle in mild conditions (< 100 °C and 50 bar of H2). From thermodynamic and kinetic studies, it has been determined that the alloy can display a reversible capacity of 1.0 - 1.1 H2 wt.% H2 at 55 °C in the pressure range 2 to 25 bar. The H2 sorption kinetic is rather fast, requiring less than 10 min to absorb/desorb 90% of the entire capacity. A good cycle stability was observed since, within 250 cycles, no changes in the storage capacity and kinetic performances were detected. The alloy was also cycled with H2 containing 50 ppm in volume of water, together with oxygen (< 100 ppm) and nitrogen (< 3000 ppm). In this latter case, the H2 capacity is maintained stable over cycling, as with pure hydrogen, but the sorption kinetic is slightly slower, with about 80% of the capacity absorbed/desorbed in 10 min.