Stripping away ion hydration shells in electrical double-layer formation: Water networks matter
Serena Rosa Alfarano, Simone Pezzotti, Christopher J. Stein, Zhou Lin, Federico Sebastiani, Sarah Funke, Claudius Hoberg, Inga Kolling, Chun Yu, Katja Mauelshagen, Thorsten Ockelmann, Gerhard Schwaab, Li Fu, Jean‐Blaise Brubach, P. Roy, Martin Head‐Gordon, Kristina Tschulik, Marie‐Pierre Gaigeot, Martina Havenith
Abstract
Significance For centuries the double layer at the solid/electrolyte interface has been a central concept in electrochemistry. Today, it is still crucial for virtually all renewable energy storage and conversion technologies. Here, the double-layer formation is probed by THz spectroscopy with ultrabright synchrotron light as a source. Our results capture the molecular details of double-layer formation at positively/negatively charged Au electrodes for an NaCl electrolyte. We reveal a contrasting response applying positive versus negative bias, which is dictated by the interfacial water network and rationalized by accompanying molecular dynamics simulations and electronic-structure calculations. While Na + is directly attracted toward the negatively charged electrode, stripping of the Cl − hydration shell is observed only at larger potential values.