Studies On Several Typical Electrochemical Oscillatory Systems

The profound study on electrochemical oscillations has important scientific meaning for recognizing the oscillatory phenomena, developing the electrode processes and richening the research content of the non-equilibrium and nonlinear dynamic. From the viewpoint of electrode processes, several typical electrochemical oscillatory systems have been studied in this paper, including electrochemical reactions coupled with surface ad/desorption, phase transition and liquid mass transfer.1.Potential oscillatory behaviors on antimony-modified and bismuth-modified platinum electrodes for the electrocatalytic oxidation of one-carbon organic molecules.Electrochemical behaviors and oscillatory characteristics for the oxidation of one-carbon organic molecules on Pt/Sb electrodes are investigated. We found that with the increase of sb, the electrocatalytic activity increases for the oxidation of HCOOH and HCHO, but decreases for the oxidation of CH3OH. No a positive correlation was found between oscillation and electrocatalytic activity. A plausible explanation is given here. The presence of Sb adatom affects the dual path parallel reactions on Pt in different extents, and thus changes the relative strength of the positive and negative feedbacks on the Pt, leading to the change of oscillatory characteristics. CV criterion explains the experimental results well. The results of formic acid oxidation on. Bi-modified electrodes are similar to those on Pt/Sb electrodes.2.In situ Raman spectroscopic studies on the current oscillations during gold electrodissolution in HC1 solutionRaman spectroscopy has been used for investigating the gold oscillatory electrodissolution processes in a 2 mol dm-3HCl solution. Thespatial profile of AuCl4- concentration in the diffusion layer, and the temporal evolution of AuCl4- during the current oscillations have all been measured in situ by a confocal Raman spectroscope. These experimental results indicate that the transition between active and passive states of gold accounts for the current oscillations in a very narrow potential range. A crossing cycle in the cyclic voltammogram that means a pair of overlapping positive and negative feedbacks corresponds to the active-passive transition. The electrodisslotion of Au is a typical example of oscillations system generating from the coupling of electrochemical reactions with surface phase transition.3. In situ monitoring of potential oscillations in the reduction of IO3-by electrochemical quartz crystal microbalance The new experimental results that were obtained by in situ EQCM monitoring clearly demonstrate the all key steps involved in the oscillation: the diffusion-limited depletion of IO3- by reduction, the formation, growth and departure of hydrogen bubbles on the surface, and the convection-induced replenishment of IO3- by the hydrogen evolution, our study shows that simultaneous frequency responses to the changes of density and viscosity in the diffusion layer during the oscillation can also provide meaningful and even decisive information on the oscillatory mechanism for the oscillators involving the coupling of electrochemical reactions with diffusion and convection mass transfer.