Comparative study of hydrogen electrosorption from alkali metals electrolytes and hydrogen sorption from gas phase in AB5 alloy

•Determination of maximum hydrogen capacity of the alloy using PCT Sievert's method.•Determination of electrochemical capacity of the alloy in 1 M and 6 M alkali metal hydroxide electrolytes.•Design of an optimum alkali metal hydroxide electrolyte giving the highest possible electrochemical capacity of the alloy.•Investigation of temperature influence

AB5-type metal alloy (LaMm-Ni4.1Al0.3Mn0.4Co0.45) was investigated in alkali metal hydroxide electrolytes (LiOH, NaOH, KOH, RbOH, CsOH) at various temperatures (0-30 °C) with no binding materials used. Limited volume electrode approach (LVE) was used in all electrochemical measurements. PCT Sievert's method was used to determine maximum hydrogen capacity of the alloy to be 4.7 at.H/f.u. (289 mAh/g). The highest electrochemical hydrogen capacity, nearly reaching the maximum value, was obtained in 6 M KOH solution at 30 °C (275.1 mAh/g) and in mixed 6 M LiOH/KOH solution at 30 °C (276.1 mAh/g). Temperature influence on electrochemical capacity of the alloy was investigated. In the temperature range of 0-30 °C the capacity is high and stable in 6 M KOH solution and mixed 6 M LiOH/KOH and 6 M NaOH/KOH solutions. It is possible to improve the capacity of the alloy by designign mixed alkali metal hydroxide solutions.