Comparing Advanced Bipolar Membranes for High-Current Electrodialysis and Membrane Electrolysis

Advanced bipolar membranes (BPMs) with low water-dissociation overpotential (η_wd) may enable new electrochemical technologies for electrolysis, fuel cells, acid–base synthesis, brine remediation, lithium-battery recycling, and cement production. However, these advanced BPMs have only been demonstrated in BPM water electrolysis (BPMWE) configurations where the BPM is under static compression by the porous-transport layers. It is important to study these BPMs in applications like electrodialysis where large degrees of static compression are not possible. We present a BPM electrodialysis (BPMED) platform to measure water-dissociation overpotential (η_wd) and compare BPMWE and BPMED systems. We show advanced BPMs with half the η_wd compared to commercial BPMs for BPMED while maintaining ∼90% current efficiency from 0.05–0.5 A cm^–2. The BPMED η_wd values are, however, about 0.2 V higher at 0.5 A cm^–2 than those for BPMWE. Regardless, these results show that BPMs developed and optimized in BPMWE applications are well-suited for next-generation high-current-density BPMED technologies.