All-in-One Bipolar Membrane Electrode Assembly for Water Electrolysis

Water dissociation (WD, H₂O → H⁺ + OH^-) occurring at the bipolar membrane (BPM) junction can be leveraged in water electrolyzers for green hydrogen production, enabling the anode and cathode reactions to operate in kinetically favorable pH environments. However, practical application of BPM-integrated membrane electrode assemblies (BPMEAs) in electrolyzers faces formidable challenges due to the sluggish WD efficiency and insufficient stability at the bipolar junction. Here, we develop a convenient serial spraying approach to fabricate an all-in-one BPMEA. This approach endows the BPMEA with a wrinkled bipolar junction and integrated membrane/electrode interfaces, expanding the active interfaces and thereby enhancing WD efficiency and mass transport within BPMEA. As a result, the BPMEA exhibits competitive pure water and asymmetric acid/alkali electrolyzer voltages of 3.25 and 2.69 V at a high current density of 3000 mA cm^-2, achieving 32% and 23% savings in energy consumption. Moreover, the wrinkled architecture imparts physical reinforcement to the bipolar junction and membrane/electrode interfaces, leading to an appropriate durability at current densities of 500-1000 mA cm^-2. This work provides insights into the performance degradation mechanisms of BPM electrolyzers, and the proposed all-in-one approach is applicable to a broader range of electrochemical applications beyond water electrolysis.