Proton Selective Nanoporous Atomically Thin Graphene Membranes for Vanadium Redox Flow Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Proton exchange membranes (PEMs) are crucial for Vanadium Redox Flow Batteries (VRFBs).
• Current PEMs like Nafion 212 exhibit significant vanadium ion crossover, reducing VRFB efficiency.
• Atomically thin 2D materials offer new possibilities for high-performance PEMs.

Purpose of the Study:

• To develop a novel layered PEM using 2D materials for enhanced proton selectivity and reduced ion crossover.
• To achieve high areal proton conductance and low vanadium ion permeability for improved VRFB performance.
• To explore atomic-scale defect engineering in 2D materials for scalable PEM fabrication.

Main Methods:

• Fabrication of a layered PEM comprising graphene with Angstrom-scale pores, a polybenzimidazole (PBI) layer, and Nafion layers.
• Introduction of proton-selective pores in graphene via Ar plasma treatment.
• Characterization using transport experiments and resistance-based modeling to analyze ion transport and membrane properties.

Main Results:

• The engineered layered PEM demonstrated exceptionally low vanadium ion crossover (selectivity ≈6709 × 10^6 S min cm^-4).
• Achieved high areal proton conductance exceeding 8 S cm^-2, over 671 times improvement in selectivity compared to Nafion 212.
• Layered architecture and defect isolation strategies effectively mitigated ion crossover and enhanced membrane performance.

Conclusions:

• Atomic-scale proton-selective defect engineering in 2D materials is a viable strategy for advanced PEMs.
• Facile stacking and layering of materials enable scalable fabrication of high-performance membranes.
• This approach holds potential for significant advancements in PEMs for energy storage and other electrochemical applications.