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.