engleski

Electrocatalytic behavior of the Co_33 Zr_67 metallic glass for hydrogen evolution

Amorphous Co_33 Zr_67 alloy, prepared by rapid solidification of its components (Co, Zr) in an argon atmosphere, was investigated in view of its possible application as electrocatalytic material for the hydrogen evolution reaction (h.e.r). Electrocatalytic efficiency was evaluated on the basis of electrochemical and impedance measurements carried out in deaerated 1 M NaOH solution. The results were compared with polycrystalline Co and Zr metals. The Tafel slope, b_c and the value of exchange current density, j_o confirmed rather good electrocatalytic properties of Co ; on the contrary, pure Zr exhibited very poor activity for the h.e.r. which was influenced by the presence of a ZrO_2 surface layer due to high affinity of Zr for oxygen. Improved electrocatalytic performances were obtained after the as quenched Co_33 Zr_67 samples were chemically pretreated in HF solution. The true kinetic parameters of these electrodes for the hydrogen evolution reaction resembled that of Co, but the stability and activity in the highest state exceeded those of pure polycrystalline Co electrode. Experimental results of hydrogen evolution kinetics on the Co_33 Zr_67 alloy were discussed using known electronic structure of Co-Zr amorphous alloys, ionicity difference between Co and Zr, as well as the free energy of adsorption and the bond strength of hydrogen adsorbed on Co.

Co ; Zr ; Co-Zr alloys ; metallic glasses ; electrocatalysis ; hydrogen evolution ; electronic structure

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