Water-soluble pyridinium redox mediators for pH-swing CO₂ capture

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Science

Background:

• Electrochemical pH-swing processes are a promising avenue for energy-efficient carbon dioxide (CO2) capture.
• The development of robust and effective redox mediators is crucial for the success of these processes.

Purpose of the Study:

• To report and evaluate novel water-soluble 4-substituted pyridinium redox mediators for electrochemical pH-swing CO2 capture.
• To establish molecular design principles for optimizing pyridinium-based mediators for energy-efficient carbon management.

Main Methods:

• Synthesis of three water-soluble pyridinium redox mediators: BzM, BzSP, and AcSP.
• Performance evaluation using H-cell and flow cell configurations.
• Assessment of CO2 capture efficiency and capacity.

Main Results:

• Highly water-soluble mediators with a propylsulfonate group were synthesized in a single step on a 20 g scale.
• A benzoyl group at the 4-position was found to be critical for high current densities.
• The zwitterionic BzSP mediator demonstrated approximately 90% CO2 capture efficiency and an optimal capacity of 102 kJ molCO2-1 in a flow cell.

Conclusions:

• Pyridinium-based redox mediators can be effectively designed for electrochemical pH-swing CO2 capture.
• Molecular modifications, such as the inclusion of benzoyl and propylsulfonate groups, significantly impact mediator performance.
• These findings provide valuable insights for developing next-generation mediators for energy-efficient carbon capture technologies.