In this study, a super acid with impressive hygroscopicity, 1-[3-(methacryloyloxy)propylsulfonyl]-1-(triﬂuoromethanesulfonyl)imide (MPTI), is exploited to improve the proton conductivity of PEMs at low humidity. Importantly, MPTI can deliquesce into an aqueous solution by capturing moisture from air at a considerable rate. Investigation of the hygroscopicity of MPTI and the corresponding mechanism by molecular dynamics simulation show a total interaction energy between MPTI and water of −368.13 kJ mol−1, which greatly exceeds those of model derivatives with other typical hygroscopic groups. To apply MPTI in PEMs and prevent leakage, MPTI is incorporated into a semi-interpenetrating polymer network via in situ polymerization, and Nafion-based composite membranes are fabricated. The water uptake of the obtained hybrid membranes is substantially increased by up to 66.61% at 40% RH and 90.04% at 95% RH. This optimization of the water environment facilitates the dissociation of protons and the formation of hydrogen bond networks for high-speed proton conduction. As a result, the proton conductivity of the membranes increases by up to two orders of magnitude at low humidity. Notably, this composite membrane enhanced the performance of a single fuel cell at 60% RH by 41.9%.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We are grateful for support from the Tsinghua University Initiative Scientific Research Program (52302300119). In addition, we thank Dr. Ying Li at the Tsinghua University Branch of China National Center for Protein Sciences (Beijing) for technical assistance with preparing the ultramicrocuts. We also thank HEOWNS Biochem Technologies LLC for customizing MPTI.