REACTIONS OF HALOGENATED HYDROCARBONS AT PT-GROUP METALS .2. ON THE ADSORPTION RATE AT PT AND PD ELECTRODES

DEMS studies on the adsorption of halogenated methane derivates led to the conclusion that those compounds adsorb as = CH2 or equivalent to CH species on Pt and Pd. Apart from those structures on Pt, a GO-like adsorbate which results from addition of water molecules or OH- ions i s formed. The adsorbate can partially be desorbed at negative potentia ls by the formation of methane, ethane and a little butane. At anodic potentials the adsorbate is oxidized to CO2. The adsorption rate incre ases with the number of halogen atoms in the molecule. Moreover, it is dependent on the charge of the electrode or the competitive adsorptio n OH- anions. The transfer of the electrons during adsorption reaction was found not to be the rate-determining reaction step. (C) 1997 Else vier Science Ltd.