Effect of Electrolyte Concentration on the Stern Layer Thickness at a Charged Interface

• Published in: Angewandte Chemie International Edition 2016-03, Vol.55 (11), p.3790-3794
• Main Authors: Brown, Matthew A., Goel, Alok, Abbas, Zareen
• Format: Article
• Language: English
• Subjects: Charge density; Charging; Chemical Sciences; Chemistry; Conductivity; Density; Electric charge; electrical double layer; Electrolytes; Fysikalisk kemi; Interfaces; Ions; Kemi; liquid microjets; Nanoparticles; Photoelectron spectroscopy; Physical Chemistry; Physics; potential drop; Silica; Silicon dioxide; Sodium chloride; solid-liquid interface; Spectroscopic analysis; Spectroscopy; Stern Layer; Stern layer capacitance; Surface charge; Thickness; X ray photoelectron spectroscopy
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201512025

The chemistry and physics of charged interfaces is regulated by the structure of the electrical double layer (EDL). Herein we quantify the average thickness of the Stern layer at the silica (SiO2) nanoparticle/aqueous electrolyte interface as a function of NaCl concentration following direct measurement of the nanoparticles’ surface potential by X‐ray photoelectron spectroscopy (XPS). We find the Stern layer compresses (becomes thinner) as the electrolyte concentration is increased. This finding provides a simple and intuitive picture of the EDL that explains the concurrent increase in surface charge density, but decrease in surface and zeta potentials, as the electrolyte concentration is increased. The electrical double layer (EDL) is presented in a simple and intuitive picture that explains the concurrent increase in surface charge density, but decrease in surface and zeta potentials, as electrolyte concentration is increased.