An effective activation method for industrially produced TiFeMn powder for hydrogen storage

Influence of near-surface oxide layers on TiFe hydrogenation: mechanistic insights and implications for hydrogen storage applications

“…From these results, it can be concluded that most of the oxygen molecules are only rather weakly physically adsorbed on the air-exposed surface and can potentially be easily removed by low-temperature activation methods, such as those mentioned by Dreistadt et al 23 or Patel et al 83 Moreover, this shows that the three oxide layer thicknesses considered in this study offer a suitable primary depiction of air-exposed TiFe for the intended technical purpose as a room-temperature hydrogen storage material. Therefore, we proceeded to assess the stability and chemical environment of the near-surface oxides using the obtained AIMD data.…”

“…However, we want to note that oxygen-rich lms of up to 20 nm thickness can be generally observed on the material surface according to other studies. 23,82 Starting from DFT optimized structures in Section 3.1.2, the simulation temperatures were increased in steps of 150 K beginning from 300 K (room temperature) up to 600 K for a time duration of 5 and 10 ps at each temperature to obtain thermally calibrated oxide phases.…”

“…The different types of surface oxides may also expand with different thermal expansion coefficients, which can facilitate H transport through cracks as shown in other studies by some of us. 23 (4) H penetration through sub-surface oxide layers is kinetically hindered under standard conditions and requires either higher thermal energies to overcome multiple activation barriers and/or utilization of catalytically active dopants to reduce the respective barrier heights.…”

“…One way of achieving this is by adding elements such as Mn, Zr or Cr to the TiFe alloy that were found to be able to enhance the ability of hydrogen to penetrate the oxide and activate the storage material. 22,23 Substitutional elements are also thought to enhance initial hydrogenation rates at the surface by selectively forming oxides and secondary phases. 9,24 However, substitution may also lead to a capacity loss and the surface activated by heat treatment is again prone to deactivation upon air exposure.…”

Developing sustainable FeTi alloys for hydrogen storage by recycling

“…In recent years, many attempts to enhance the FeTi hydrogen storage properties have been carried out mostly by elemental substitution. By adding A-type (Ti) elements like Nb, Zr, and V into the system, the strength of the hydrogen-metal bonds can be modified, while the addition of B-type (Fe) elements such as Cu, Ni, Co, Mn, and Al can improve the electrocatalytic activity, thus facilitating the activation process 11,12 . Additionally, alloying with elements such as Mn and V allows reducing the hydrogenation/dehydrogenation plateau pressure slope [13][14][15] .…”