The elecrocatalytic activity of Ni-Zr based crystalline and amorphous alloys has been tested for the hydrogen evolution reaction. Ni36Zr64 and Ni27Zr48Al25 amorphous alloys have been produced in ribbon form by rapid solidification. The amorphous-to-crystalline transformation has been followed by DSC, XRD and TEM. The various samples have been subjected to electrochemical tests by means of cathodic polarization curves in 1 M KOH at 25°C and the obtained exchange current density has been taken as a measure of catalytic efficency. Surface activation treatments have been performed by chemical etching in HF or by leaching in KOH and a morphological and compositional analysis of the surfaces has been performed by SEM/EDS. The electrochemical behaviour of pure elements (Ni and Zr) has also been considered for comparison. All the samples need a chemical pre-treatment in order to become active. A higher electrocatalytic activity has been observed for amorphous with respect to crystalline alloys with the same composition. For a nanocrystalline microstructure, obtained by partial crystallization of amorphous Zr64Ni36, an electrocatalytic efficiency comparable to that of the amorphous phase has been observed. Treatments with concentrated HF solutions enhance the electrocatalytic activity and this effect has been related to the formation of nanocrystalline Ni at the surfaces. The leaching of Zr48Ni27Al25 produces also small Ni particles owing to the dissolution of Al.
Electrocatalytic properties of Ni-Zr based amorphous and nanocrystalline alloys
BARICCO, Marcello;ANTONIONE, Carlo
1997-01-01
Abstract
The elecrocatalytic activity of Ni-Zr based crystalline and amorphous alloys has been tested for the hydrogen evolution reaction. Ni36Zr64 and Ni27Zr48Al25 amorphous alloys have been produced in ribbon form by rapid solidification. The amorphous-to-crystalline transformation has been followed by DSC, XRD and TEM. The various samples have been subjected to electrochemical tests by means of cathodic polarization curves in 1 M KOH at 25°C and the obtained exchange current density has been taken as a measure of catalytic efficency. Surface activation treatments have been performed by chemical etching in HF or by leaching in KOH and a morphological and compositional analysis of the surfaces has been performed by SEM/EDS. The electrochemical behaviour of pure elements (Ni and Zr) has also been considered for comparison. All the samples need a chemical pre-treatment in order to become active. A higher electrocatalytic activity has been observed for amorphous with respect to crystalline alloys with the same composition. For a nanocrystalline microstructure, obtained by partial crystallization of amorphous Zr64Ni36, an electrocatalytic efficiency comparable to that of the amorphous phase has been observed. Treatments with concentrated HF solutions enhance the electrocatalytic activity and this effect has been related to the formation of nanocrystalline Ni at the surfaces. The leaching of Zr48Ni27Al25 produces also small Ni particles owing to the dissolution of Al.
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