Charge-induced equilibrium dynamics and structure at the Ag(001)–electrolyte interface

Abstract

The applied potential dependent rate of atomic step motion of the Ag(001) surface in weak NaF electrolyte has been measured using a new extension of the technique of X-ray Photon Correlation Spectroscopy (XPCS). For applied potentials between hydrogen evolution and oxidation, the surface configuration completely changes on timescales of 10(2)-10(4) seconds depending upon the applied potential. These dynamics, directly measured over large areas of the sample surface simultaneously, are related to the surface energy relative to over or under potential. Concurrent specular X-ray scattering measurements reveal how the ordering of the water layers at the interface correlates with the dynamics.

In Situ and Operando X-ray Scattering Methods in Electrochemistry and Electrocatalysis

“…While the water layering and orientation reversal are undisputed, the strongly enhanced water density was not found in other X-ray surface scattering studies and molecular dynamics (MD) simulations of water at metal surfaces. For Ag (100) in NaF electrolyte 289 and Au (111) in halide solutions, 163 the CTRs were well described with water layers that corresponded to the bulk water density. MD simulations as well as more recent AIMD simulations of water at Ag, Hg, and Pt electrodes also found water layers with bulk-like density at the interface.…”

“…While the water layering and orientation reversal are undisputed, the strongly enhanced water density was not found in other X-ray surface scattering studies and molecular dynamics (MD) simulations of water at metal surfaces. For Ag(100) in NaF electrolyte and Au(111) in halide solutions, the CTRs were well described with water layers that corresponded to the bulk water density. MD simulations as well as more recent AIMD simulations of water at Ag, Hg, and Pt electrodes also found water layers with bulk-like density at the interface. − Furthermore, the interfacial water at multilayer graphene on SiC was studied by SXRD. , Although the electron density contrast between water and the solid is more favorable here than in the case of metals, the intrinsic heterogenity of these electrodes leads to additional difficulties in the data analysis.…”