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 H2 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 H2 crossover rate (0.9% H2 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 enhanced 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, compelling combination of ionic conductivity, low gas-crossover, and efficiency.