COADSORPTION, NONREACTIVE DISPLACEMENT AND CATHODIC DESORPTION OF ETHENE PREADSORBED ON PD AND PT ELECTRODES

From both Pd and Pt electrodes, ethene is desorbed at low potentials u nder hydrogenation as shown by differential electrochemical mass spect rometry (DEMS). The deposition of Cu on the ethene-covered Pt surface leads to the desorption of only 10% of the adsorbate as ethene itself, contrary to the case of benzene, which can be almost completely displ aced. The same amount of desorbing ethene is found when adbsorbing I- or CO onto the ethene-precovered surface. In the case of Pd, such a pa rtial displacement is only observed when using I-as the displacing age nt; CO and CU2+ lead to coadsorption. (C) 1998 Elsevier Science B.V.