Issue 5, 2020

Cross-correlated humidity-dependent structural evolution of Nafion thin films confined on a platinum substrate

Abstract

Nanometer thin films of Nafion ionomer interfaced with platinum form the functional electrodes in many electrochemical devices including fuel cells and electrolyzers. To impart facile proton conduction in a Nafion ionomer, sufficient hydration of the Nafion ionomer is necessary to create a percolating network of water-filled nanometer-sized hydrophilic domains that manifest as macroscopic swelling. This hydration behavior of the ionomer thin films is poorly understood especially for films confined on electrochemically relevant Pt substrates. In this work, we present the evolution of hydration-dependent microscopic hydrophilic domains and macroscopic expansion of a 55 nm thin Nafion film on a Pt substrate. The cross-correlation among the film macro-expansion from ellipsometry, the micro-expansion from GISAXS, and the water distribution from neutron reflectometry (NR) explains the observed non-affine behavior of the film which can be attributed to the randomly and spatially non-uniform distribution of water domains. A correlation between the macroscopic factor (ε/τ) for protonic conductivity, and the domain size and swelling is presented for the first time. In addition, interfacial water between Pt and the ionomer interface is estimated at 75% and 84% RH, and an increase in domain size with RH is discussed to explain the increased activity and oxygen diffusivity with RH.

Graphical abstract: Cross-correlated humidity-dependent structural evolution of Nafion thin films confined on a platinum substrate

Supplementary files

Article information

Article type
Paper
Submitted
26 अगस्त 2019
Accepted
16 दिसम्बर 2019
First published
16 दिसम्बर 2019

Soft Matter, 2020,16, 1190-1200

Cross-correlated humidity-dependent structural evolution of Nafion thin films confined on a platinum substrate

U. N. Shrivastava, K. Suetsugu, S. Nagano, H. Fritzsche, Y. Nagao and K. Karan, Soft Matter, 2020, 16, 1190 DOI: 10.1039/C9SM01731C

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements