Composite membranes anchoring phosphotungstic acid by β-cyclodextrins modified halloysite nanotubes

Anchoring phosphotungstic acid (HPW) on insoluble inorganic fillers is a facile and effective approach to suppress its leakage in the proton exchange membrane. In this work, we introduced beta-cyclodextrin (beta-CD) on halloysite nanotubes (HNTs) with the aid of polydopamine coating to prepare water-insoluble beta-CD-DHNTs, which was dispersed in the SPEEK matrix to anchor HPW. Both HPW and beta-CD-DHNTs are well dispersed in the SPEEK matrix because of the hydrogen bonding complexation between [PW12O40](3-) and beta-CD. For the SPEEK/beta-CD-DHNTs/HPW composite membranes, the proton conductivity increased with the increase of HPW content, reaching the maximum of similar to 120% increase relative to that of the SPEEK membrane. The HPW immobilized by the beta-CD and polydopamine on the nanotubes could provide more active sites, resulting in the construction of more continuous proton transfer pathways. Therefore, as compared to the SPEEK membrane, lower activation energy for the proton transport was observed for the composite membrane, which also exhibited stable proton conductivity during the water immersion test for 30 days.

Automated summary

Anchoring phosphotungstic acid (HPW) on insoluble inorganic fillers is an effective approach to suppress leakage in proton exchange membranes. Introducing beta-cyclodextrin (beta-CD) on halloysite nanotubes (HNTs) with polydopamine coating dispersed in SPEEK matrix anchors HPW and results in enhanced proton conductivity by providing more active sites for continuous proton transfer pathways.