Does power ultrasound affect Nafion® dispersions?

Area of Science:

• Materials Science
• Chemical Engineering
• Electrochemistry

Background:

• Nafion® ionomer is crucial for fabricating proton exchange membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs).
• Optimizing catalyst ink viscosity is essential for efficient electrode fabrication in PEMFCs and PEMWEs.

Purpose of the Study:

• To investigate the impact of low-frequency power ultrasound on Nafion® ionomer dispersions.
• To evaluate changes in viscosity, thermal degradation, and glass transition temperature of Nafion® dispersions after ultrasonic treatment.

Main Methods:

• Nafion® dispersions (10, 5, and 2.5% w/v) were subjected to low-frequency power ultrasound (42 kHz, >2 W) for varying durations.
• Viscosity, thermal degradation (TGA), and glass transition temperature (DSC) were measured and compared to untreated samples.
• Experiments were conducted under controlled and unregulated bulk solution temperatures.

Main Results:

• Power ultrasound significantly lowered the viscosity of all tested Nafion® dispersion samples.
• Ultrasonic irradiation resulted in negligible overall polymer degradation and no obvious change in glass transition temperature.
• Both acoustic and hydrodynamic cavitation were identified as key factors in viscosity reduction.

Conclusions:

• Low-frequency power ultrasound is an effective method for reducing Nafion® dispersion viscosity without compromising thermal stability.
• The findings suggest potential for improved catalyst ink formulation for PEMFCs and PEMWEs.
• Acoustic cavitation may induce depolymerization followed by polymerization initiation during ultrasonication.