engleski

Electrocatalytic behaviour of Ni-Zr metallic glasses as hydrogen electrodes

The amorphous alloys or metallic glasses consisting of an early and a late transition metal can often be obtained in a broad range of concentrations. This makes a systematic investigation of their physical properties possible. As a result, a considerable amount of data is available on the electronic structure ; thermodynamic and electronic transport properties of amorphous Zr-based transition metal glasses containing Fe, Co, Ni, Cu, Rh, and Pd. These and other similar glassy alloys posses a rather high d-like electronic density of states at the Fermi level (E_F) which strongly affects their thermodynamic properties. Compositional flexibility allows the tailoring of alloys according to the requirements of a given application. This possibility has been explored to optimise the properties of certain glasses for application in catalysis, electrocatalysis and corrosive environments. In this paper, we report the results regarding the hydrogen evolution reaction (h.e.r.) on Ni-Zr amorphous alloy electrodes as well as on polycrystalline Ni and Zr electrodes, in order to characterise their electrocatalytic activity, efficiency and stability. Both polarisation and impedance studies clearly show that the electrode process is controlled by one reaction (Heyrovsky step). Electrocatalytic activity for hydrogen evolution decreases in the order: Ni, Ni_60 Zr_40, Ni_33 Zr_67, Zr. The high energy of hydrogen adsorbance on zirconium influences the overall h.e.r. process in two ways. It facilitates the adsorption of hydrogen, and at the same time the strength of this bond makes the adsorption reaction at the active centres irreversible which lessens the overall active surface and rate of the h.e.r. Our results support the view that d-like states at E_F strongly mark almost all properties of Ni-Zr systems.

amorphous metals; Ni-Zr alloys; alcaline water electrolysis; hydrogen evolution; metal hydride; energy conversion

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