Bubble Formation in the Electrolyte Triggers Voltage Instability in CO₂ Electrolyzers

Area of Science:

• Electrochemistry
• Greenhouse Gas Mitigation
• Catalysis

Background:

• Electrochemical reduction of carbon dioxide (CO2) is a key technology for mitigating greenhouse gas emissions.
• High current densities are necessary for commercial viability but are limited by voltage instabilities.
• Bubble formation is a known phenomenon in water electrolysis but its impact on CO2 electrolyzers is not well understood.

Purpose of the Study:

• To identify the root cause of voltage instabilities in CO2 electrolyzers.
• To investigate the unique role of product gas bubbles in CO2 electrolysis performance.
• To provide insights for designing more stable and commercially viable CO2 electrolyzers.

Main Methods:

• Operando electrochemical measurements.
• Gas diffusion electrode (GDE) characterization.
• Analysis of bubble dynamics at the electrode/electrolyte interface.

Main Results:

• Product syngas bubble accumulation at the GDE-electrolyte interface directly causes voltage instability in CO2 electrolyzers.
• Approximately 10% bubble coverage on the GDE surface led to significant voltage oscillations (60 mV).
• Syngas bubbles physically disrupt the two-phase reaction interface, leading to performance degradation.

Conclusions:

• Voltage instability in CO2 electrolyzers is uniquely attributed to product gas bubble accumulation.
• Understanding and managing bubble behavior is critical for achieving high current densities.
• This research provides essential insights for the rational design of next-generation CO2 electrolyzers.