Continuous Electrochemical Carbon Capture via Redox-Mediated pH Swing─Experimental Performance and Process Modeling

Area of Science:

• Electrochemistry
• Chemical Engineering
• Environmental Science

Background:

• Carbon dioxide (CO2) capture is crucial for mitigating climate change.
• Existing CO2 capture methods often face challenges with energy efficiency and scalability.
• Electrochemical methods offer a potential alternative for CO2 capture with tunable performance.

Purpose of the Study:

• To investigate a continuous electrochemical pH-swing method for CO2 capture.
• To analyze the impact of key process parameters on CO2 capture efficiency and energy consumption.
• To develop a theoretical framework for system design and optimization.

Main Methods:

• Utilized a single cation-exchange membrane (CEM) electrochemical cell.
• Employed a recirculating solution of salt and phenazine-based redox-active molecules.
• Operated in absorption and desorption steps with controlled pH swings.
• Investigated effects of redox molecule concentration, current density, and recirculation rate.

Main Results:

• Achieved a low energy consumption of 32 kJ/mol of CO2.
• Reported a high CO2 capture rate of 39 mmol/m2/min.
• Developed a theoretical framework that accurately describes experimental data.
• Demonstrated effective CO2 release through electrochemical pH reduction.

Conclusions:

• The electrochemical pH-swing method is a viable and efficient technology for CO2 capture.
• The developed theoretical model aids in optimizing the process for practical applications.
• This method presents a competitive alternative to existing carbon capture technologies regarding energy efficiency.