Enhancing proton conduction of high temperature proton exchange membranes based on carbon dots doped polyvinyl chloride nanofibers

Carbon dots (CDs) as the easy-to-get and cheap carbon nanomaterials exhibited the great potential in various high-performance electrolytes. In this research, we constructed high temperature proton exchange membranes with multilayered microstructures through a couple of polyvinyl chloride (PVC) nanofibers layers wrapping a thin CDs layer. In the prepared (PVC/CDs/PVC)es membrane, the CDs provided a mount of sites to anchor phosphoric acid (PA) molecules with the formation of the (PVC/CDs/PVC)es/PA membrane. The proton conduction was accelerated by the continuous proton conduction channels consisting of the CDs layer and PA molecular chains. Notably, the proton conduction behavior was guided by the PVC nanofibers in the (PVC/CDs/PVC)es/PA membrane. Furthermore, a large number of hydrophilic oxygenated functional groups surrounding CDs facilitated the proton conduction process owing to the reduced proton conduction resistance in the hydrophilic membrane. For the PVC/ImCDs/PA membrane, the imidazolium groups could enhance proton conductivity. From our perspective, the imidazolium groups grafted CDs (ImCDs) participated into the proton conduction process through providing imidazolium groups for ameliorating proton conduction network. The enhanced proton conduction was achieved through constructing multilayered structure. Specifically, the (PVC/CDs/PVC)es/PA membrane exhibited the proton conductivity of 5.61 × 10-3 S/cm at 150 °C, which was higher than 7.73 × 10-4 S/cm of the PVC/CDs/PA membrane. Notably, the PA doped membrane could retain the mechanical strength without microstructure expansion.