Unravelling the electrochemical double layer by direct probing of the solid/liquid interface

• Published in: Nature communications Vol. 7; no. 1; p. 12695
• Main Authors: Favaro, Marco, Jeong, Beomgyun, Ross, Philip N., Yano, Junko, Hussain, Zahid, Liu, Zhi, Crumlin, Ethan J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 31-08-2016; Nature Publishing Group; Nature Portfolio
• Subjects: 140/146; 639/301/119/544; 639/638/161; 639/638/542/971; electrochemistry; Electrodes; Electrolytes; Electrons; Energy storage; Humanities and Social Sciences; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Laboratories; MATERIALS SCIENCE; multidisciplinary; Science; Science (multidisciplinary); Spectrum analysis; surface spectroscopy; surfaces, interfaces and thin films; X-rays; South Korea; California; United States > US; China
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms12695

The electrochemical double layer plays a critical role in electrochemical processes. Whilst there have been many theoretical models predicting structural and electrical organization of the electrochemical double layer, the experimental verification of these models has been challenging due to the limitations of available experimental techniques. The induced potential drop in the electrolyte has never been directly observed and verified experimentally, to the best of our knowledge. In this study, we report the direct probing of the potential drop as well as the potential of zero charge by means of ambient pressure X-ray photoelectron spectroscopy performed under polarization conditions. By analyzing the spectra of the solvent (water) and a spectator neutral molecule with numerical simulations of the electric field, we discern the shape of the electrochemical double layer profile. In addition, we determine how the electrochemical double layer changes as a function of both the electrolyte concentration and applied potential.
The electrochemical double layer is a key concept in chemistry, but its properties are hard to probe experimentally. Here, the authors use ambient pressure X-ray photoelectron spectroscopy to probe the electrochemical double layer potential profile at the solid/liquid interface, under polarization conditions.