Abstract
We present an in situ surface x-ray diffraction study on the structuring impact of an anion-modified electrode surface on the near-surface liquid electrolyte. This templating effect of the so-called inner Helmholtz layer of specifically adsorbed anions affects not only the interfacial structure parallel to the surface normal by layering the liquid in the near-surface regime but induces moreover a lateral ordering of water dipoles and solvated counter ions in the so-called outer Helmholtz layer. In this respect, we observe a symmetry transfer from the inner Helmholtz layer into the liquid electrolyte next to the electrode surface. Our prototypical model system is a Cu(100) surface on which chloride adsorbs under the formation of a simple adlayer phase (this notation refers to the fcc unit cell of Cu) that serves as structural template for the coadsorption of monovalent potassium and hydronium cations from the acidified supporting electrolyte. A layer of interfacial water is interpreted as a part of the remaining solvation shell of potassium cations in the outer Helmholtz layer.
- Received 21 September 2010
DOI:https://doi.org/10.1103/PhysRevB.82.245425
©2010 American Physical Society