Influence of Fe contamination and temperature on mechanically alloyed Co–Ni–Mo electrodes for hydrogen evolution reaction in alkaline water

Ni–Co–Mo–Fe solid solutions, such as Co30Ni70, Co30Mo70, Ni30Mo70, Co10Ni20Mo70, Fe10Co25Ni65, Fe20Co20Ni60 and Fe30Co15Ni55 wt.% alloys, have been produced by mechanical alloying using commercial Ni, Co, Mo and Fe powders. The electrocatalytic properties of these nanocrystalline materials have been studied for hydrogen evolution reaction (HER) in 30 wt.% KOH aqueous solution at three different temperatures (308, 323 and 343 K) to determine the effect of Fe contamination. The methods employed were cyclic voltammetry, steady-state polarization (Tafel) techniques and ac impedance. For comparison, it was found that iron improved electrocatalytic activity for the hydrogen evolution reaction. Important changes in the activity were obtained when the temperature was increased. The electrocatalytic effect of Mo became important at high overvoltages and temperatures. The MA Fe30Co15Ni55 and Co10Ni20Mo70 alloyed powders showed the best catalytic activities for HER.