(571c) Electrochemical Synthesis of Sound: ‘Tuning’ the Electrochemical Double Layer

The electrochemical double layer (EDL) governs the function of batteries, fuel cells, electrolyzes, sensors and all other electrochemical devices crucial to modern life and to enabling the transition to an electrified chemical industry. Understanding and tuning the EDL is crucial in engineering selective and efficient electrochemical reactions. However, the EDL is inherently challenging to understand because there are no methods to make its configuration and behavior perceptible in ways that are immediately intuitive to humans. Herein we demonstrate a new method of analyzing the behavior of the EDL by employing an electrochemical interface as the capacitor in an astable multivibrator circuit and thereby bringing the EDL into resonance. When the circuit is connected to a speaker, the resonant charging and discharging frequency of the double layer resulting from the movement and structuring of electrolyte ions and their interaction with the electrode can be becomes audible, allowing for unprecedented intuitive insight into EDL behavior.

The resonance frequency is strongly influenced by electrode and electrolyte properties, with some dynamics accurately described by the Guy-Chapman-Stern EDL model, while others highlight the complex interactions occurring at electrochemical interfaces. Beyond making EDL properties audible, we found our system to allow the analysis of time-dependent EDL rearrangements which occur upon the application of a voltage. As the interest in electrochemical technologies keeps growing, while fundamental understanding of the behavior of the underlying science remains scarce, we expect our electrochemical oscillator circuit to provide improved and valuable insight into the fundamental electrochemical principles governing chemical transformations.