Electrochemical modification of Cu-Zr amorphous alloys for catalysts

This paper presents the authors' attempts to use some strictly controlled electrochemical processes of dissolution/redeposition of Cu (including disproportionation of Cu+ to Cu metal and Cu2+) to modify its surface, as well as surfaces of Cu base amorphous alloys (AA), to produce active substrates for Various phenomena of adsorption and catalytic reactions. New methods of activation of the Cu substrate have been developed for in situ investigations of adsorbates with surface enhanced Raman spectroscopy (SERS). The method consisting in fast dissolution/redeposition produces a clean and large specific surface area substrate, which results in high quality SERS spectra. This method appeared also useful for a modification of the surface activity of partially devitrified Cu-Zr amorphous alloys. Energy dispersive spectrometry (EDS)/X-ray electron microprobe investigations of both AA ribbon surface and its cross-section revealed a peculiar structure of the devitrified material. some multilayer sandwiches of Cu/ZrO2 were formed locally. Their fractal edges formed certain 'flowers' of Cu clusters supported by ZrO2. The electrochemical pre-treatment was eventually applied after this partial devitrification. The catalytic efficiency of dehydrogenation of 2-propanol at such a pre-treated Cu-Zr substrate increased up to a factor of 2. It has been found that the increase in the SERS activity of an electrochemically pretreated Cu-Zr substrate and the enhancement of its catalytic efficiency are of the same morphological and compositional origin. A tentative mechanism of the surface activation is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.