Asymmetric Bipolar Membrane for High Current Density Electrodialysis Operation with Exceptional Stability

Bipolar membranes (BPMs) enable isolated acidic/alkaline regions in electrochemical devices, facilitating optimized catalytic environments for water electrolysis, CO2 reduction, and electrodialysis. For economic feasibility, BPMs must achieve stable, high current density operation with low overpotentials. We report a graphene oxide (GrOx) catalyzed, asymmetric BPM capable of electrodialysis at 1 A cm-2 with overpotentials < 250 mV. Experiments and continuum modeling demonstrate that the low overpotentials for water dissociation are achieved by deprotonation at GrOx catalyst sites located within the high electric field BPM junction region. The asymmetric nature of the BPM allows it to overcome water transport limitations due to its thin anion exchange layer, while maintaining near unity Faradaic efficiency for acid and base generation. Additionally, the asymmetric BPM exhibits voltage stability exceeding 1100 hours at 80 mA cm-2 and 100 hours at 500 mA cm-2 and its freestanding architecture implemented in an electrodialysis cell stack demonstrates its real-world applicability.