Anion Adsorption and Adsorption/Desorption Kinetics onto/from Au(111) Electrodes Studied Using the Indirect Laser-Induced Temperature Jump Technique

摘要

We demonstrate that the potential dependence of the initial change (A/ΔT_(eq)) in the open-circuit potential of Au(111) | (nonelectroactive) electrolyte solution interfaces (effected by the temperature perturbation (ΔT_(eq)) induced by the indirect laser-induced temperature jump (ILIT) technique) is sensitive to the presence of the anion components of the electrolyte adsorbed onto the electrode surfaces for a wide variety of anions. Analysis of the potential dependence of A/ ΔT_(eq) for the ClO4~- and SO4~(2-)- anions, therefore, is used to ascertain (for ClO4~-) or estimate (for SO4~(2-)) the temperature derivative of the dipole potential (i.e., (dVD)/(dT)) associated with the relevant Au(111) | electrolyte solution interface. The value and any potential dependence of (dV_D)/(dT) are suitable probes of the structure of the pertinent electrode j electrolyte interface. The negative value determined here for the (dV_D)/(dT) associated with a complete (saturated) layer of ClO4~- ions adsorbed onto a Au(111) electrode surface (i.e., -(0.51 ± 0.08) mVK~(-1)) is, for example, consistent with a picture of this layer where the hydrogen atoms of the water molecule constituents of this layer originally (before the temperature perturbation) point, as should be expected, are toward the adsorbed CI04 ions. Additionally, we demonstrate that studies of the potential dependence of the adsorption/ desorption kinetics of adsorbate ions may also be used as a structural probe of the electrochemical double layer containing the adsorbed ion. Accordingly, as the result of a study of the adsorption/desorption kinetics of Cl~- ions adsorbed onto a Au( 111) electrode, we speculate that the first layer of water molecules in contact with this surface is compressed.