We report stationary, nonequilibrium potential and adsorbate patterns with an intrinsic wavelength that were observed in an electrochemical system with a specific type of current/electrode-potential (I-phi(DL)) characteristic. The patterns emerge owing to the interplay of a self-enhancing step in the reaction dynamics and a long-range inhibition by migration currents rather than by diffusion. Theoretical analysis revealed that this self-structuring of the electrode occurs in all electrochemical systems with an S-shaped I-phi(DL) characteristic in wide and well-accessible parameter ranges. This unusual pattern-forming instability in electrochemical systems has all the characteristics of the mechanism proposed by Turing in 1952 in the framework of an early theory of morphogenesis. Our finding might account for structure formation in certain biological systems that have gradients in the electric potential and may open new paths for fabricating patterned electrodes.

Using HPLC technique, two different pathways were found for the oxidation of bromomalonic acid by Ce 4+ . One route is dominant when the Ce 4+ concentration is low compared to that of bromomalonic acid (BrMA). The end products of this reaction route are bromoethenetricarboxylic acid (BrEETRA), CO 2 , and Br -. For this route two slightly different mechanisms (both are based on radical-radical recombination reactions) are proposed, which can explain the formation of BrEETRA. The other pathway is dominant when Ce 4+ is in excess. This route leads to a complete oxidation of BrMA to CO 2 . No intermediates of this route were found, however.

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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.