Double Layer at the Pt(111)–Aqueous Electrolyte Interface: Potential of Zero Charge and Anomalous Gouy–Chapman Screening

Abstract

We report, for the first time, the observation of a Gouy–Chapman capacitance minimum at the potential of zero charge of the Pt(111)‐aqueous perchlorate electrolyte interface. The potential of zero charge of 0.3 V vs. NHE agrees very well with earlier values obtained by different methods. The observation of the potential of zero charge of this interface requires a specific pH (pH 4) and anomalously low electrolyte concentrations (<10−3 m). By comparison to gold and mercury double‐layer data, we conclude that the diffuse double layer structure at the Pt(111)‐electrolyte interface deviates significantly from the Gouy–Chapman theory in the sense that the electrostatic screening is much better than predicted by purely electrostatic mean‐field Poisson–Boltzmann theory.

Molecular origin of negative component of Helmholtz capacitance at electrified Pt(111)/water interface

“…These models cover a potential window ranging from −0.93 to 0.84 V with respect to the PZC of Pt(111) [i.e., 0.2 to 0.3 V versus SHE (25,(37)(38)(39)(40)], which enables us to investigate the water structure and capacitance of the Helmholtz layer on Pt(111). It is worth mentioning that, in this work, we ignore the specific adsorption of H and OH, which amounts to the pH conditions when specific adsorption is insignificant, and the experimental capacitances we compare against are removed with pseudo-capacitances due to specific adsorption (41)(42)(43).…”

Stripping away ion hydration shells in electrical double-layer formation: Water networks matter

“…This requires new experimental techniques that are able to selectively probe the EDL and simultaneously provide molecular-level information, under operando (i.e., operating or reaction) electrochemical conditions. In the past two decades, a number of theoretical (12)(13)(14)(15)(16)(17) and experimental (18)(19)(20)(21)(22)(23)(24)(25)(26)(27) studies have been performed to explore the microscopic structure of the electrochemical double layer. It is still an experimental challenge to probe interfaces under operando conditions, due to difficulties in regulating all the variables involved in electrochemical reactions (28,29), such as controlling surface structure and mass transport.…”

Electric double layer structure in aqueous electrolyte and its electrocatalytic importance

“…Thus, a concentrated electrolyte is essential to manifest a camel shape in the Kornyshev model, and in the dilute limit, the results of this model approach those of Gouy 25 -Chapman 26 model. Therefore, the Kornyshev model is suitable for explaining the camel-shaped capacitance measured in a dense Coulomb system such as an ionic-liquid electrolyte 34,[43][44][45][46][47][48] , whereas our mechanism explains the camel-shaped capacitance measured in a dilute aqueous electrolyte [15][16][17][18][19] .…”

“…Instead of explaining the peaks from photon-based spectroscopy, we herein demonstrate that our molecular simulation accurately reproduces the characteristic peaks from an electrochemical impedance spectroscopy -the famous camel-shaped curve [15][16][17][18][19] of the capacitance in dilute aqueous electrolyte -without the requirement of empirical adjustment in the simulation. To reliably compute the differential capacitance, 𝐶𝐶, using its definition of 𝐶𝐶 = 𝜕𝜕𝜕𝜕 𝜕𝜕𝜕𝜕 ⁄ (where 𝜕𝜕 is a surface charge density, and 𝜕𝜕 is an electrode potential), the sensitive changes in the potential must be captured that require an extremely fine sampling of the data points, which is practically impossible using a full ab initio approach 20 .…”