Competitive Anion/Water and Cation/Water Interactions at Electrified Copper/Electrolyte Interfaces Probed by in Situ X-ray Diffraction

Abstract

The full 3D structure of a copper/electrolyte interface is studied by means of in situ surface X-ray diffraction (SXRD) methods. Chloride anions chemisorb on Cu(100) in 10 mM HCl at high potentials under formation of a p(1 × 1)-Cl adlayer. This anionic chemisorption layer serves as a structural template for the lateral ordering of water molecules and hydronium cations in the near-surface liquid electrolyte. Evidence for this interfacial geometry is mainly derived from the intensity distribution of surface-sensitive X-ray diffraction data along the (10L)-adlayer rod. The characteristic oscillating intensity distribution along the (10L) rod is due to a centered bilayer system consisting of the anionic inner Helmholtz layer (IHL) of chemisorbed chloride and the cationic outer Helmholtz layer (OHL). The latter is constituted in the present case by hydronium cations that preferentially populate 4-fold hollow sites of the underlying chloride lattice. IHL and OHL are separated by an extra interfacial water layer. Anions and cations in the IHL and OHL compete for these water species as part of their solvation shell. The Cl/water/hydronium bilayer can be considered as a prototypical model system where the anions and cations in the coupled bilayer system are sharing the interfacial water as part of their solvation shell. In this respect, the Cl − /water/hydronium bilayer considerably differs from the previously studied Cl − /water/K + system where the interfacial water was clearly assigned to the solvation shell of the alkali metal cation in the OHL. The absence of strongly solvated alkali metal cations in the OHL leads to an increase in the in-plane and out-of-plane exchange dynamics of water and hydronium cations as manifested by an isotropic atomic displacement parameter that is notably higher for the Cl − /water/hydronium than for the more static Cl − /water/K + system. A comprehensive comparison of our results with other state-of-the-art SXRD studies strongly suggests that the adsorption of partly solvated cations on-top of an anionmodified metal electrode surface has to be considered as a specif ic cation adsorption phenomenon since the particular structure of the formed bilayer system as well as the involved interfacial dynamics clearly depend on the chemical nature of the anions and cations involved in the structure formation.

Effect of Non‐Specifically Adsorbed Ions on the Surface Oxidation of Pt(111)

“…The d OÀPt value of adsorbed OH ad was found to be 2.1 by low-energy electron diffraction, [32] which is consistent with that (14) at 0.9 V. At 1.2 V, the IR band intensity of OH ad decreases. The charge density of anodic peak II (132 mC cm À2 ) is lower than that of peak I.…”

“…[5,6] Doublelayer studies were extended to single-crystal electrodes by using voltammetry and capacitance measurements, [7] and the atomic-level structure and electrochemical properties of chemisorption layers have been widely studied by using scanning probe microscopy, vibrational spectroscopy and X-ray diffractometry. [9][10][11][12][13][14][15] We determined the structure of the non-adsorbed Cs + cation above Br adsorbed on Ag(100) and revealed that formation of the Br adlayer was promoted by the attractive non-covalent interaction between hydrated Cs + and Br ad . Recently, the detailed structures of some non-specifically adsorbed ions have been determined by using the surface Xray diffraction (SXRD) method.…”

“…Recently, the detailed structures of some non-specifically adsorbed ions have been determined by using the surface Xray diffraction (SXRD) method. [9][10][11][12][13][14][15] We determined the structure of the non-adsorbed Cs + cation above Br adsorbed on Ag(100) and revealed that formation of the Br adlayer was promoted by the attractive non-covalent interaction between hydrated Cs + and Br ad . [11,15] Non-covalent interactions with surface and adsorbed species also affect the activity of industrially important reactions such as those in fuel cells.…”

Nitrate reduction pathways on Cu single crystal surfaces: Effect of oxide and Cl−

“…Cl -is known to form overlayer arrays on Cu over a potential region starting at -300 mV vs. RHE (roughly -500 mV vs. Ag/AgCl) and through the anodic potential range. [47][48][49] Cl -has also been demonstrated to poison the nitrate reduction process on copper and cause a negative nitrate reduction potential shift. Figure 6.…”

Solvent effects on ion–receptor interactions in the presence of an external electric field

“…The mechanism of the interaction between the solvated ions and surfaces has been an intriguing question for researchers. [75][76][77][78][79][80] Here we aim to verify minimum requirements for a precise theoretical description of the ion-receptor interaction by comparing our theoretical results with experimental data. The potential of implicit and cluster-continuum solvent models for dealing with this issue is examined in detail.…”