Ubiquitous preferential water adsorption to electrodes in water/1-propanol mixtures detected by electrochemical impedance spectroscopy

TL;DR

This study investigates the double-layer capacitance at aluminum-electrolyte interfaces in water/1-propanol mixtures, revealing that water preferentially adsorbs on electrodes regardless of electrolyte type, affecting electrochemical device performance.

Contribution

It demonstrates that water exhibits ubiquitous preferential adsorption on electrodes in water/1-propanol mixtures, independent of electrolyte composition, using electrochemical impedance spectroscopy.

Findings

Double-layer capacitance is similar in water and mixture solutions.

1-Propanol-only solutions have significantly smaller capacitance.

Water preferential adsorption is independent of electrolyte type.

Abstract

The electric double layer is an important structure that appears at charged liquid interfaces, and it determines the performance of various electrochemical devices such as supercapacitors and electrokinetic energy converters. Here the double-layer capacitance of the interface between aluminum electrodes and water/1-propanol electrolyte solutions is investigated using electrochemical impedance spectroscopy. The double-layer capacitances of mixture solvents are almost the same as those of water-only electrolyte solutions, and the double-layer capacitance of 1-propanol-only solutions are significantly smaller than those of other volume fractions of water. The qualitative variation of the double-layer capacitances with the water volume fraction is independent of the electrolyte types and their concentrations. Therefore, these results can be explained by ubiquitous preferential water adsorption caused by the hydrophilicity of the electrode surface.