Advancing ionomer design to boost interfacial and thin-film proton conductivity via styrene-calix[4]arene-based ionomers

Authors

Shyambo Chatterjee, University of Nebraska–Lincoln
Oghenetega Allen Obewhere, University of Nebraska–Lincoln
Ehsan Zamani, University of Nebraska–Lincoln
Rajesh Keloth, University of Nebraska–Lincoln
Seefat Farzin, University of Nebraska–Lincoln
Martha D. Morton, University of Nebraska–Lincoln
Anandakumar Sarella, University of Nebraska–Lincoln
Shudipto Konika Dishari, University of Nebraska–LincolnFollow

Date of this Version

2-15-2023

Document Type

Article

Citation

Cell Reports Physical Science 4, 101282, February 15, 2023

doi:10.1016/j.xcrp.2023.101282

Comments

This is an open access article under the CC BY-NC-ND license

Abstract

Sub-micrometer-thick ion-conducting polymer (ionomer) layers often suffer from poor ionic conductivity at the substrate/catalyst interface. The weak proton conductivity makes the electrochemical reaction at the cathode of proton-exchange-membrane fuel cells sluggish. To address this, here we report on a class of polystyrene-based ionomers having sub-nanometer-sized, sulfonated macrocyclic calix[4]arene-based pendants (PS-calix). In films with thickness comparable to that of ionomer-based binder layers, the conductivity of PS-calix film (∼41 mS/cm) is ∼13 times higher than that of the current state-of-the-art ionomer, Nafion. We observe a similar improvement in proton conductivity when PS-calix interfaces with Pt nanoparticles, demonstrating the potential of PS-calix in catalyst ink. Leveraging a favorable interfacial chemical composition, PS-calix enhances proton conduction at the film-substrate interface, a shortcoming of Nafion. Moreover, the water in PS-calix films diffuses faster than bulk water and the water confined in Nafion films, suggesting an important role played by sub-nanometer-sized calix[4]arene cavities in creating unique water/ion transport pathways.