Perfluorosulfonic Acid Membrane with Engineered Ionic Cluster Channels and Pore‐Filling Structure for Efficient Alkaline Water Electrolysis

A novel separator for alkaline water electrolysis (AWE) is developed by structurally engineering a pore‐filling perfluorosulfonic acid (PFSA) membrane, effectively mitigating the energy inefficiency and hydrogen crossover challenges associated with conventional AWE separators. A pore‐filling PFSA membrane with an extended polytetrafluoroethylene matrix is heated in a high‐boiling‐point polar organic solvent to generate enlarged phase‐separated nanoscale ionic cluster channels, yielding a swollen membrane with improved ionic conductivity. This swollen pore‐filling PFSA membrane demonstrates enhanced selectivity for OH − transport over H 2 permeability under electrolysis conditions. An AWE with a zero‐gap electrode configuration comprising this membrane and nonprecious metal electrodes is operated in 1 M KOH at 80 °C, exhibiting a current density of 1.0 A cm −2 at a cell voltage of 1.76 V, a corresponding energy efficiency of 84%, and a low H 2 crossover rate (0.9% H 2 in the anode gas stream at 1.0 A cm −2 ). The integration of a high‐performance cathode catalyst within a pore‐filling swollen‐PFSA membrane‐based membrane–electrode assembly further enhances the performance (1.0 A cm −2 at 1.68 V with an energy efficiency of 88%). These findings emphasize the potential of this membrane as a next‐generation separator for AWE, a compelling combination of ionic conductivity, low gas‐crossover, and efficiency.