Abstract
A series of end-group cross-linked membranes (Az-XESPSN) were prepared by click reaction to investigate the effects of cross-linking on the morphology and proton transport properties of proton exchange membranes. The morphological transformations resulting from thermal annealing and cross-linking were observed by means of atomic force microscopy (AFM) and transmission electron microscopy (TEM). Compared to the non-cross-linked ESPSN membranes, the Az-XESPSN membranes exhibited lower water uptake and improved mechanical and chemical stabilities. In addition, the Az-XESPSN membranes exhibited higher proton conductivities (0.018–0.028 S cm−1) compared to those of the ESPSN membranes (0.0044–0.0053 S cm−1) and Nafion 212 (0.0061 S cm−1), particularly in conditions of elevated temperature (120 °C) and low relative humidity (35%). Such enhancements can be attributed to a synergistic effect of well-defined hydrophilic ionic clusters and triazole groups that function as proton carriers under anhydrous conditions. Furthermore, the Az-XESPSN membranes exhibited significantly enhanced single cell performance and long-term stability compared to those of ESPSN membranes.
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•The end-group cross-linked membranes were prepared by click reaction.•The membranes showed excellent proton conductivity and single cell performances.•The cross-linked membrane exhibited much improved long-term durability.