Review on high-performance polymeric bipolar membrane design and novel electrochemical applications

Electrochemical devices allow the conversion and storage of renewable energy into high-value chemicals to mitigate carbon emissions, such as hydrogen production by water electrolysis, carbon dioxide reduction, and the electrochemical synthesis of ammonia. Independent regulation of the electrode pH environment is essential for optimizing the electrode reaction kinetics and enriching the catalyst species. The in situ water dissociation (WD, H2O -> H++OH-${{{\mathrm{H}}}_2}{\mathrm{O}} \to {{{\mathrm{H}}}<^> + } + {\mathrm{O}}{{{\mathrm{H}}}<^> - }$) in bipolar membranes (BPMs) offers the possibility of realizing this pH adjustment. Here, the design principles of high-performance polymeric BPMs in electrochemical device applications are presented by analyzing and connecting WD principles and current-voltage curves. The structure-transport property relationships and membrane durability, including the chemical and mechanical stability of the anion- and cation-exchange layers as well as the integrality of the interfacial junction, are systematically discussed. The advantages of BPMs in new electrochemical devices and major challenges to break through are also highlighted. The improved ion and water transport in the membrane layer and the minimized WD overpotential and ohmic loss at high current densities are expected to facilitate the promotion of BPMs from conventional chemical production to novel electrochemical applications. Bipolar membranes have great potential in the field of electrochemistry, especially in water electrolysis and CO2 electroreduction. This review focuses on the design principles of high-performance polymer bipolar membranes, especially for membrane material synthesis and interface regulation, aiming to provide guidance for the large-scale application of bipolar membranes. image