Stripping off of the Hydration Shells in the Double Layer Formation: Water Networks Matter

Abstract

<div><br></div><div><p>The double layer at the solid/electrolyte interface is a key concept in electrochemistry. Here, we present an experimental study combined with simulations, which provides a molecular picture of the double-layer formation in operando processes. By THz spectroscopy we are able to follow the stripping off of the cation/anion hydration shells for a NaCl electrolyte at the Au surface when decreasing/increasing the bias potential. While Na<sup>+</sup> is attracted toward the electrode already at the smallest applied negative potentials, stripping-off of the Cl<sup>-</sup> hydration shell is observed only at higher potential values. These phenomena are directly measured by in operando THz spectroscopy with ultra-bright synchrotron light as a source and rationalized by accompanying molecular-dynamics simulations and electronic-structure calculations. </p></div>

Electrochemistry under confinement

“…122,123 By analogy to the solvated ions, the molecular dipoles can orient along the electric field, 124 leading to local changes in polarity and thus in free energy of solvation or adsorption. Especially the effect of the latter impede the predictability of the EDL structures under biased potentials as shown by Alfrano et al 125 Unusual alignment of single molecules and formations of ice-like networks from solvent molecules 126 under confinement might facilitate these deviations even further and will be introduced in the next section.…”