Electrocatalytic properties of Fe-R (R = rare earth metal) crystalline alloys as hydrogen electrodes in alkaline water electrolysis

The electrocatalytic properties of some Fe-R crystalline alloys, Fe(90)Ce(10), Fe(90)Sm(10), Fe(90)Y(10) and Fe(90)MM(10) (MM = mischmetal), were studied for the hydrogen evolution reaction (HER) in 1 M NaOH solution at 298 K. The microstructure of the electrodes was examined by optical microscopy, scanning electron microscopy (SEM) coupled with electron probe microanalysis and X-ray diffraction (XRD) measurements. The performances towards the HER were investigated by dc polarization and ac impedance techniques. The results were compared with the G14 (Fe(60)Co(20)B(10)Si(10)) amorphous alloy, which is a good electrocatalyst material for the HER. The steady-state polarization curves and electrochemical impedance spectroscopy data showed that high catalytic efficiencies for the HER were achieved on the Fe(90)Ce(10) and Fe(90)MM(10) electrodes, the latter being a better catalyst as compared with the G14 alloy. Based on the Brewer-Engel valence bond theory, the improvement of the electrocatalytic performances of the Fe(90)Ce(10) and Fe(90)MM(10) electrodes as compared with the Fe(90)Y(10) and Fe(90)Sm(10) ones was attributed to synergetic composition effects of the alloys. (c) 2005 Elsevier B.V. All rights reserved.