CL-36 LABELING AND ELECTROCHEMICAL STUDY OF CHLORIDE ADSORPTION ON A GOLD ELECTRODE FROM PERCHLORIC-ACID MEDIA

We present experimental data on adsorption of chloride anions on a smo oth polycrystalline gold electrode using the Cl-36 radioactive labelli ng method. Owing to weak signal from the Cl-36 radiation source, previ ous radiochemical studies had been done with rough substrates. The rad iochemical procedure includes the evaluation of a 'squeezing efficienc y' and a contribution from secondary X-radiation, as well as a new cal ibration scheme vis-a-vis our previous efforts. Using this new radioch emical approach in combination with cyclic voltammetry, we studied the potential dependence of adsorption and surface-bulk exchange processe s, and compared chloride and sulfate adsorption. In the double layer p otential range, the already reported chloride surface concentration (G amma)-electrode potential relationships were confirmed. The Gamma vs. E profiles taken in the oxidation range reflected a rich surface chemi stry of gold in chloride media in terms of sorption properties of gold oxides and formation of gold complexes with chloride. An integrated u nderstanding of chloride electrosorption and reactivity in the full el ectrode potential range accessible to investigations in aqueous soluti on is outlined based upon the experimental material obtained in this s tudy.