A comparison of electrochemical and Auger analysis of the surface composition of platinum-rhodium alloys

Values of the surface composition of platinum-rhodium alloys determined electrochemically, utilizing the potential of the oxygen desorption peak on cyclic voltammograms, have been compared with those obtained by Auger electron spectroscopy (a.e.s.). This comparison confirms that the electrochemical method is applicable to analysis of the surface of cycled as well as untreated homogeneous noble metal alloys. The composition profile in the surface region of cycled electrodes was determined by sputtering of the surface followed by a.e.s. measurements. The rhodium content was found to increase linearly with depth. The depth scale was established from analyses of the metal dissolved during potential cycling. Consideration of the differences between data obtained from the electrochemical and a.e.s. studies leads to the conclusion that the surface zone involved in chemisorption extends over a few atomic layers.