Electrochemical modification of Cu-Zr amorphous alloys for catalysts

This paper presents the authors' attempts to use some strictly controlled e lectrochemical processes of dissolution/redeposition of Cu (including dispr oportionation of Cu+ to Cu metal and Cu2+) to modify its surface, as well a s surfaces of Cu base amorphous alloys (AA), to produce active substrates f or Various phenomena of adsorption and catalytic reactions. New methods of activation of the Cu substrate have been developed for in situ investigatio ns of adsorbates with surface enhanced Raman spectroscopy (SERS). The metho d consisting in fast dissolution/redeposition produces a clean and large sp ecific 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 spectro metry (EDS)/X-ray electron microprobe investigations of both AA ribbon surf ace 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. Th e electrochemical pre-treatment was eventually applied after this partial d evitrification. The catalytic efficiency of dehydrogenation of 2-propanol a t 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 p retreated Cu-Zr substrate and the enhancement of its catalytic efficiency a re of the same morphological and compositional origin. A tentative mechanis m of the surface activation is discussed. (C) 2000 Elsevier Science Ltd. Al l rights reserved.