Adsorption of camphor on Au(111) and its effect on the electroreduction of periodate (IO₄^-)

The potential-controlled physisorption of camphor on Au(111) single-crystalline bulk as well as thin film electrodes and its influence on the electroreduction of IO₄^- to IO₃^- is studied. Besides cyclic voltammetry (CV), we use second-harmonic generation (SHG) to study electronic and structural properties of the surface and surface-plasmon resonance (SPR) shift measurements to probe the interfacial dielectric function, which is influenced by adsorption. Emphasis is placed on the interplay of surface reconstruction with the adsorption of neutral and ionic species and the reaction dynamics. Independent of the presence of the electroactive species IO₄^-, a 2D-condensed layer of camphor forms in a certain potential range and tends to preserve the structure of the surface. The film inhibits the electroreduction of IO₄ ^- at negative potentials and is displaced from the surface by periodate-derived anions at more positive potentials, whereupon the reaction is resumed. The anion adsorption causes a fast lifting of the reconstruction which is not fully restored on the reversed potential sweep owing to the re-formation of the condensed camphor film.