Spotlight on the Effect of Electrolyte Composition on the Potential of Maximum Entropy: Supporting Electrolytes Are Not Always Inert

• Published in: Chemistry : a European journal Vol. 27; no. 39; pp. 10016 - 10020
• Main Authors: Ding, Xing, Garlyyev, Batyr, Watzele, Sebastian A., Kobina Sarpey, Theophilus, Bandarenka, Aliaksandr S.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 12.07.2021; John Wiley and Sons Inc
• Subjects: Alkali metals; Batteries; Cations; Chemistry; Communication; Communications; Composition effects; electrocatalysis; Electrochemistry; electrolyte influence; Electrolytes; Electrolytic cells; Entropy; Fuel cells; Fuel technology; gold electrodes; laser-induced current transient; Maximum entropy; Metal ions; pH effects; Potassium sulfate; potential of maximum entropy; Sodium sulfate
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202101537

The influence of electrolyte pH, the presence of alkali metal cations (Na+, K+), and the presence of O2 on the interfacial water structure of polycrystalline gold electrodes has been experimentally studied in detail. The potential of maximum entropy (PME) was determined by the laser‐induced current transient (LICT) technique. Our results demonstrate that increasing the electrolyte pH and introducing O2 shift the PME to more positive potentials. Interestingly, the PME exhibits a higher sensitivity to the pH change in the presence of K+ than Na+. Altering the pH of the K2SO4 solution from 4 to 6 can cause a drastic shift in the PME. These findings reveal that, for example, K2SO4 and Na2SO4 cannot be considered as equal supporting electrolytes: it is not a viable assumption. This can likely be extrapolated to other common “inert” supporting electrolytes. Beyond this, knowledge about the near‐ideal electrolyte composition can be used to optimize electrochemical devices such as electrolyzers, fuel cells, batteries, and supercapacitors. Gold standards: By determining the potential of maximum entropy (PME) with the laser‐induced current transient technique, the influence of the electrolyte composition on polycrystalline gold has been systematically investigated. Increasing the electrolyte pH and purging O2 shift the PME to more positive potentials. The electric double‐layer structure for Aupc in solutions containing Na+ and K+ ions is vastly different when electrolyte pH reaches six or higher. This method enables another approach for the interpretation of interfacial electrocatalytic processes.