APPLICATION OF TRANSMISSION MOSSBAUER-SPECTROSCOPY TO THE SURFACE STUDY OF NI(II)-FE(III) HYDROXIDE ELECTROCATALYSTS - COMPARISON WITH AES DATA

Transmission Mossbauer spectra of binary coprecipitated nickel(II)-iro n(III) hydroxides (molar ratios 9:1 and 4:1) are analysed and compared with the results of AES analyses of their surface composition. A corr elation between the data of the above techniques has been noted, indic ating a redistribution of the components (i.e. Ni and Fe) in the surfa ce layers, the latter being enriched with iron(III) as compared to the bulk. The results obtained are in good agreement with an excellent el ectrocatalytic activity of composite Ni-Fe hydroxide systems towards a nodic oxygen evolution in alkaline electrolytes, taking into account a distinctly exhibited 'surface' electrocatalytic effect of ferric spec ies on the nickel hydroxide electrode in the anodic oxygen evolution p rocess revealed previously. Transmission Mossbauer spectroscopy has be en shown to be a highly effective probe sensitive both to various bulk and surface effects related to the solid phases studied.