A Resonance Hybrid Design for Stable Aqueous Organic Redox Flow Batteries

Area of Science:

• Energy Storage
• Materials Science
• Electrochemistry

Background:

• Organic molecules are attractive for aqueous organic redox flow batteries (AORFBs) due to sustainability and tunability.
• Water-induced degradation and unwanted restructuring reactions limit the stability of organic redox-active materials.

Purpose of the Study:

• To introduce a novel resonance hybrid molecule, 2,3-dihydroxyl substituted phenazine dication (HSPC), for enhanced stability in AORFBs.
• To investigate the electrochemical properties and stability of HSPC in aqueous environments.

Main Methods:

• Electrochemical synthesis and characterization of HSPC.
• Spectroscopic analysis and theoretical studies to understand resonance structures.
• Performance evaluation in a 1.4 M electron concentration AORFB cell.

Main Results:

• HSPC exhibits a unique resonance hybrid structure distributing electron density between phenazine and quinone forms.
• The molecule demonstrates efficient reversible electron transfer in aqueous solutions.
• The AORFB cell using HSPC showed exceptionally low capacity decay rates (0.0009% per cycle, 0.006% per day).

Conclusions:

• The resonance hybrid design is a viable strategy for developing stable organic redox-active materials.
• HSPC shows significant potential for advancing sustainable energy storage solutions in AORFBs.
• This approach could be extended to other energy storage applications requiring stable redox materials.