  The present study investigates the partial substitutions of Mn and Cu for Fe
in the TiFe-system to gain better understanding of the role of elemental
substitution on its hydrogen storage properties. The TiFe0.88-xMn0.02Cux (x =
0, 0.02, 0.04) compositions were studied. From X-Ray Diffraction (XRD) and
Electron Probe Micro-Analysis (EPMA), it was found that all alloys are
multi-phase, with TiFe as a major phase, together with \b{eta}-Ti and
Ti4Fe2O-type as secondary precipitates, of all them containing also Mn and Cu.
Increasing the Cu content augments the secondary phase amounts. Low quantity of
secondary phases helps the activation of the main TiFe phase for the first
hydrogen absorption, but on increasing their amounts, harsher activation
occurs. Both Mn and Cu substitutions increase the cell parameter of TiFe, thus
decreasing the first plateau pressure. However, Cu substitution rises the
second plateau pressure revealing the predominancy of electronic effects
associated to this substitution. All samples have fast kinetics and high
hydrogen capacity making these substituted compounds promising for large scale
stationary applications.
