Giving voice to the electrochemical interface

Sometimes engineers just want to have fun. And that fun can yield useful insights. In an elegant example, researchers have translated the motion of ions and molecules at the interface between an electrode and electrolyte into audible sound (ACS Cent. Sci. 2024, DOI: 10.1021/acscentsci.3c01253).

Electrode-electrolyte interfaces are the work center of batteries, electrolyzers, and electrochemical sensors. The molecular interactions at these interfaces are invisible, says Marcel Schreier, a chemical and biological engineering professor at the University of Wisconsin–Madison. Giving voice to the interface yields a “direct, quick, and intuitive probe into its behavior,” he says.

Schreier and colleagues started with a sound-generating electronic circuit. Capacitors in the circuit charge and discharge, producing a waveform that speakers convert to sound. The electrode-electrolyte interface has a capacitance that depends on the configuration of its ions and molecules. So the team swapped the circuit’s capacitor with an electrode placed in an electrolyte solution. “Now the dynamics of the system are controlled by what happens at the metal-solution interface,” Schreier says, “and we can start playing with it.”

The researchers found that changing the voltage across the interface, the electrode material, or the type and concentration of electrolyte changed the sound from the circuit. The method could in theory be used to monitor electrochemical performance. For now, Schreier says, the team plans to use it as a fun educational outreach project. “The beauty is it’s a ludicrously simple circuit: it’s one chip and a few resistors.”