Electrolytic hydrogen storage in recluctant intermetallic systems

Composite electrodes were prepared by mixing, in the ratio 60/40 by weight, the powder of an electrochemically inhibited intermetallic compound (IMC), e.g. TiFe 50/50, TiNi 70/30 or TiNi 40/60 (alloy precursor grade) with Fe powder and pressing the mixture on to a Ni foam support. The charge capacity achieved in these composites was then compared with the capacity of "blank" electrodes in which the IMC had been replaced by an inactive metal (Ti or Ni). The blanks attained capacities in the range 150-200 mA h g-', although these values were largely exceeded by some IMC + Fe composites due, presumably, to storage on hydrogen. The electrocatalytic properties of Fe are probably not sufficient to explain the activation of hydrogen absorption in the inhibited IMC, since X-ray and energy-dispersive analysis (EDAX) of activated samples did reveal that deep modifications occurred in some composites, in which the formation of new phases may have been induced by charging-discharging cycles.