Highly Stable Polybenzimidazole Composite Membrane with a Durable Separation Layer by Interfacial Polymerization

Area of Science:

• Materials Science
• Chemical Engineering
• Polymer Chemistry

Background:

• Thin-film composite (TFC) membranes are crucial for separations but polyamide-TFC membranes lack stability.
• Hydrolysis of amido bonds limits the application of polyamide membranes in acidic or alkaline environments.

Purpose of the Study:

• To develop a highly stable polybenzimidazole (PBI)-TFC membrane.
• To enhance the permeability, selectivity, and stability of TFC membranes for demanding applications.

Main Methods:

• Interfacial condensation between 3,3'-diaminobenzidine (DAB) and benzene-1,3,5-tricarbaldehyde (BTA) to form PBI.
• Controlled pH to optimize DAB dispersity and PBI film formation.
• Characterization of PBI-TFC membrane properties and performance in vanadium flow batteries.

Main Results:

• A dense and thin PBI film (approx. 296 nm) was formed via optimized interfacial condensation.
• The PBI-TFC membrane exhibited excellent permeability (2.27 × 10⁻⁶ cm²/h) and selectivity (area resistance: 0.11 Ω cm²).
• The membrane maintained structural integrity in strongly acidic and oxidizing conditions.

Conclusions:

• The PBI-TFC membrane offers superior stability, permeability, and selectivity compared to conventional polyamide membranes.
• The PBI-TFC membrane demonstrated high energy efficiency (>80% at 160 mA cm⁻²) and stability (>300 cycles) in acidic vanadium flow batteries.
• This study presents an effective strategy for designing robust TFC membranes.