Electrocatalytic behavior of the Co33Zr67 metallic glass for hydrogen evolution

Amorphous CO33Zr67 alloy, prepared by rapid solidification of its component s (Co, Zr) in an argon atmosphere, was investigated in view of its possible application as electrocatalytic material for the hydrogen evolution reacti on (h.e.r.). Electrocatalytic efficiency was evaluated on the basis of elec trochemical and impedance measurements carried out in deaerated 1 M NaOH so lution. The results were compared with polycrystalline Co and Zr metals. The Tafel slope, b(c) and the value of exchange current density, j(0) confirmed rathe r good electrocatalytic properties of Co; on the contrary, pure Zr exhibite d very poor activity for the h.e.r. which was influenced by the presence of a ZrO2 surface layer due to high affinity of Zr for oxygen. Improved electrocatalytic performances were obtained after the as quenched Co33Zr67 samples were chemically pretreated in HF solution. The true kineti c parameters of these electrodes for the hydrogen evolution reaction resemb led that of Co, but the stability and activity in the highest state exceede d those of pure polycrystalline Co electrode. Experimental results of hydrogen evolution kinetics on the Co33Zr67 alloy w ere discussed using known electronic structure of Co-Zr amorphous alloys, i onicity difference between Co and Zr, as well as the free energy of adsorpt ion and the bond strength of hydrogen adsorbed on Co. (C) 2001 Elsevier Sci ence B.V. All rights reserved.