|
|
|
Current Understanding of Proton Conduction in Confined Ionomeric Systems
|
|
|
|
|
|
|
|
|
|
|
|
|
Shudipto Dishari
|
|
|
|
The Pennsylvania State University
|
Chemical Engineering, Penn State, University Park, Pennsylvania 16802, USA
|
|
skd19@psu.edu
|
|
|
|
|
|
|
|
|
|
|
|
Ion containing polymers (or ionomers), when confined into several nm to several hundreds of nm thick films, behave very differently from bulk membranes. Understanding the proton transport mechanism in thin ionomer layers coated over catalysts is crucial for further improvement of proton exchange membrane fuel cell (PEMFC) performance. This review paper summarizes the current understanding of proton conduction properties of supported thin ionomer (mainly Nafion) films. In thin films, the proton conduction properties may not be governed by the amount of water sorbed. Water molecules in such systems experience strong confinement, behave like bound immobilized water and fail to create percolated active proton conduction pathways. Therefore, in confined ionomeric systems, some factors other than water uptake need consideration to clearly understand the observed proton transport. These factors include solvation of ionic groups of polymer, local concentration of proton (H+hydrophilic domains, and, orientational relaxation dynamics of water.
|
|
|
|
|
|
|
|
|
|