E Herrero

Publications (3)40.2 Total impact

• Source

  Available from: 210.45.114.81

  Article: Underpotential deposition at single crystal surfaces of Au, Pt, Ag and other materials.

  E Herrero, L J Buller, H D Abruña
  Chemical Reviews 08/2001; 101(7):1897-930. · 40.20 Impact Factor
• Article: Anion Effects on the Kinetics of Mercury Underpotential Deposition on Au(111) Electrodes

  E. Herrero, H. D. Abruña
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  ABSTRACT: The kinetics and mechanism of mercury underpotential deposition (UPD) on Au(111) electrodes have been investigated in the presence and absence of strongly interacting anions including bi-sulfate, chloride, and acetate. In the absence of strongly interacting anions, i.e. in perchloric acid, the mercury UPD process is largely controlled by mercury−gold surface interactions. The presence of sulfuric acid in the supporting electrolyte alters the kinetics of the initial and final stages of mercury deposition/dissolution. The presence of two well-ordered structures at potentials below (a mercurous sulfate √3×√19 structure) and above (a √3×√7 bi-sulfate structure) mercury deposition leads to the appearance of two pairs of sharp spikes in the cyclic voltammogram. Analysis of the current transients obtained for deposition and dissolution processes reveals that three different processes are taking place during the adsorption/desorption of the mercury bi-sulfate layer:  adsorption/desorption processes governed by Langmuir kinetics, a nucleation and growth process linked to an order/disorder transition to form the mercury bi-sulfate adlayer, and an order/disorder transition related to the formation/disruption of the √3×√7 bi-sulfate layer. In chloride medium, the voltammetric profile is very similar to that obtained in sulfuric acid solution, with the presence of two sharp spikes. However, no nucleation and growth kinetics mechanism was found linked to the process of formation/disruption of the mercury chloride adlayer. The transients show a clear deviation from the ideal Langmuir behavior, probably associated with the presence of attractive interactions in the mercury chloride adlayer. The kinetics of mercury UPD in acetate media are significantly slower than in the previous media, as revealed by voltammetric and chronoamperometric measurements. The slow kinetics appear to be related to the formation of Hg2+−acetic acid complexes in solution. Although ordered structures are formed at potentials below the main UPD peak, no nucleation and growth mechanism was observed.
  01/1998;
• Article: Underpotential Deposition of Mercury on Au(111):  Electrochemical Studies and Comparison with Structural Investigations

  E. Herrero, H. D. Abruña
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  ABSTRACT: Electrochemical studies of the UPD of mercury on Au(111) electrodes have been carried out in sulfuric acid and in perchloric acid alone as well as in the presence of sulfate and chloride anions and in acetate/acetic acid buffer with emphasis on the processes taking place in the presence of (bi)sulfate anions. These voltammetric studies have been compared to recent in-situ AFM, STM, and surface X-ray scattering studies in an effort to correlate voltammetric features with surface structures and their transitions. The different processes taking place during mercury UPD on A(111) in sulfuric acid can be summarized as follows:  (i) At potentials higher than the first mercury UPD peak, there exists an ordered (bi)sulfate adlayer. The onset of mercury deposition triggers an order/disorder transition that gives rise to the first set of UPD peaks; C1/A1. (ii) Mercury deposition is governed mainly by mercury−gold interactions. As monolayer deposition reaches completion a disorder/order transition takes place giving rise to the peaks C2/A2. The adlayer is likely composed by Hg2SO4 with the coadsorption of additional H3O+ cations, as an analysis of the coulometric charges appears to indicate. (iii) At +0.816 V there appears a small voltammetric feature (peak C3) which corresponds to the disappearance of the ordered coadsorbed structure. (iv) Reduction of Hg2+ to in solution occurs at +0.54 V. (v) The final process is the completion of the mercury monolayer (peak C5) followed by the formation of a mercury−gold amalgam at +0.50 V that leads to the roughening of the electrode surface. These interpretations are consistent with both voltammetric and recent in-situ surface X-ray results as well as with previous electrochemical and STM investigations and provide a very detailed microscopic picture of the processes taking place.
  08/1997;