Pure-Water-Fed Forward-Bias Bipolar Membrane CO₂ Electrolyzer

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Electrochemical reduction of carbon dioxide (CO2) using renewable electricity is a sustainable route for chemical fuel production.
• Reactor design and operational stability challenges, including CO2 crossover and salt precipitation, hinder widespread CO2 electrolyzer deployment.

Purpose of the Study:

• To design and optimize a zero-gap CO2 electrolyzer that addresses CO2 crossover and salt precipitation.
• To achieve high efficiency and stability in CO2 electroreduction for sustainable chemical feedstock production.

Main Methods:

• Development of an asymmetrical bipolar membrane-based zero-gap CO2 electrolyzer.
• Optimization of anion-exchange-layer thickness, cathode differential pressure, and cell temperature.
• Investigation of catalyst and ionomer degradation mechanisms through postmortem analysis.

Main Results:

• Achieved over 80% CO faradic efficiency and over 200 mA cm-2 partial current density at < 3.0 V.
• Demonstrated negligible CO2 crossover and low decay rates (0.61 and 2.1 mV h-1 at 150 and 300 mA cm-2).
• Identified catalyst structural change and ionomer degradation as key decay mechanisms.

Conclusions:

• The asymmetrical bipolar membrane design effectively solves critical challenges in CO2 electrolyzer operation.
• Optimized electrolyzer performance shows a promising pathway for large-scale industrial CO2 utilization.
• Understanding decay mechanisms provides direction for future research and development of durable CO2 electrolyzers.