In-Situ Gradient Cross-Linking in Anion Exchange Membranes for Water Electrolyzers

Anion exchange membrane water electrolyzers (AEMWEs) have emerged as a promising method for the efficient and cost-effective production of hydrogen, widely seen as the ideal energy source. However, the practical application of AEMWEs is hindered by the challenge of maintaining both high conductivity and dimensional stability in anion exchange membranes (AEMs), particularly after prolonged exposure to alkaline solution. Herein, we propose a gradient cross-linking strategy to improve the dimensional stability of AEMs while preserving high conductivity. The gradient self-cross-linked AEMs are developed by implementing a slow ring-opening cross-linking of epoxides in alkaline environments. This strategy can gradually compensate for the physical failure induced by water absorption expansion while maintaining high conductivity. The tensile stress of gradient cross-linked AEMs did not decrease but instead gradually increased even after a 30 day aging treatment. The extent of tensile stress improvement has been demonstrated to be effectively regulated by the alkaline concentration. The gradient cross-linking strategy shows potential in addressing the conductivity-dimensional stability trade-off often observed in AEMs.