Hydrogenation properties of (V_0.85Fe_0.15)_100−xM_x–Ce BCC solid solution alloys with M = Cr, Mo, Al

The structure and hydrogenation properties of (V_0.85Fe_0.15)_100−xM_x–Ce (x = 0, 1, 3, 5; at%) alloys with M = Cr, Mo, Al were investigated. All the alloys show the same phase composition consisting of BCC matric and CeO₂ phases which distribute along the grain boundary. The hydrogen capacities of (V_0.85Fe_0.15)_100−xM_x–Ce change little with M, and none of them exceeds 2.0 wt%. But the plateau pressure shows remarkable linearly variation with the amount of M and the lattice parameter of BCC matric. The additions of Cr, Mo and Al raise the plateau, but the linear relation of plateau versus BCC lattice parameter of Mo/Al-added alloys is opposite to that of Cr-added alloys and many other conventional hydrogen storage alloys. The radius of hydrogen site is introduced to explain the inconsistent. The plateau pressure of (V_0.85Fe_0.15)_100−xM_x–Ce with any kind of M added increases with the contraction of the hydrogen site. The plateau pressure of (V_0.85Fe_0.15)_100−xM_x–Ce can also be reflected by the stability of hydride which is judged by the enthalpy change during the dehydrogenation.