The electrochemical reduction of carbon dioxide (CO₂) represents a promising strategy to mitigate anthropogenic emissions while producing high-value chemicals and fuels. Membrane electrode assembly (MEA) electrolyzers employing anion exchange membranes are among the most industrially relevant configurations for CO production^[1]. However, their large-scale deployment remains constrained by limited operational stability, with salt formation in the cathode compartment representing one of the most critical bottlenecks^[2]. Under applied negative potentials, alkali metal cations migrate from the anode to the cathode. There, they react with CO₂ and hydroxide ions to form carbonate and bicarbonate salts. These deposits progressively accumulate within the gas diffusion electrode and microporous layer, obstructing CO₂ transport, promoting the hydrogen evolution reaction, and ultimately leading to electrolyzer failure.

In this work, we present a novel mitigation strategy based on the integration of tuned low-frequency ultrasound into a zero-gap MEA CO₂ electrolyzer (Sono-MEA). The ultrasonic probe (26 kHz) is mechanically coupled to the cathode side and operated to induce controlled acoustic cavitation while minimizing temperature variations. Acoustic cavitation and microstreaming disrupt salt nucleation and growth, while promoting the continuous detachment and removal of crystalline deposits during operation.

The approach was validated using a 5 cm² MEA electrolyzer operating at industrially relevant current densities (300 mA cm⁻²) under ambient conditions. To rigorously assess its effectiveness, experiments were deliberately conducted under challenging, salt-promoting conditions using potassium-based electrolytes. Compared to conventional MEA operation, pulsed ultrasound leads to improved stability, maintaining CO selectivity over extended operation and delaying performance degradation. Elemental analysis, combining inductively coupled plasma measurements and EDX-FESEM characterization, confirms a reduced accumulation of alkali cations within the cathode compartment and enhanced transport of salt-forming species toward the outlet stream.

These findings demonstrate that ultrasound-assisted operation provides a continuous and non-invasive cleaning mechanism, directly addressing a key bottleneck in CO₂ electrolyzers without requiring system interruption. This approach complements existing mitigation strategies and offers a scalable pathway to improve the durability and long-term performance of MEA-based CO₂ electrolyzers.