Visualization of Ion Channels in Membranes using Electrochemical Strain Microscopy

TL;DR

This study employs electrochemical strain microscopy and conductive atomic force microscopy to visualize and analyze ion channels in Nafion-based polymer electrolytes, revealing their structure and interaction with additives.

Contribution

It introduces a combined microscopy approach to visualize buried and surface ion channels in polymer electrolytes, advancing understanding of ionic conduction mechanisms.

Findings

Hydrophilic ion channels are visualized without topography changes.

Ion channels are formed by water, sulfonic groups, and PWA interactions.

Buried and surface ion channels are simultaneously probed.

Abstract

Polymer composite electrolytes of Nafion and phosphotungstic acid (PWA) are fabricated and analyzed using electrochemical strain microscopy (ESM) and conductive atomic force microscopy (C-AFM) to visualize hydrophilic ion channels near the surface, which are composed of water and sulfonic acid groups. The results indicate that the fibrillar objects in ESM image, without significant changes in topography, are hydrophilic ion channels and additional ion channels formed by interaction between PWA and sulfonic groups in Nafion. In this study, the buried ion channels lying under the surface are probed as well as the inlet and outlet of the channels on the surface through combined use of ESM and C-AFM. The results further enhance the understanding of ionic conduction in composite polymer electrolytes in various fields.