β-Cyclodextrin modified silica nanoparticles for Nafion based proton exchange membranes with significantly enhanced transport properties

In the current study, a composite proton exchange membrane (PEM) was prepared by incorporating beta-cyclodextrin (beta-CD) modified silica nanoparticles (SN-beta-CD) into a Nafion matrix. Due to the decoration of beta-CD on the SN surface, SN-beta-CD possesses excellent compatibility with the Nafion polymer, resulting in a good dispersibility inside the membrane matrix. SN-beta-CD brings a better water retention capability for the composite PEM and hence significantly improves the proton conductivity of the composite PEM. Simultaneously, the barrier effect of SN-beta-CD which increases the tortuosity of transport channels for bulk methanol leads to an evident reduction in methanol permeability. Herein, a nearly two-order-of-magnitude promotion in membrane selectivity (i.e. the ratio of proton conductivity to membrane permeability) was achieved even under crucial conditions at elevated temperatures or high methanol concentrations.