Modification of Nafion's Nanostructure for the Water Management of PEM Fuel Cells

Published

April 15, 2023

Author(s)

Yuanchao Li, Natalie Schwab, Robert M. Briber, Joseph A. Dura, Trung Van Nguyen

Abstract

A PEM fuel cell with the Nafion® ionomer phase of the cathode catalyst layer (CL) that was exposed to dry gas during the annealing process showed improved performance over the whole current density range and 220% peak power increase with humidified air at 70oC. This enhanced performance is attributed to the modified structure of the perfluorosulfonic acid (PFSA) ionomer layer in the CL during the annealing process. The dry gas exposure above the glassy transition temperature (Tg) results in the formation of ionic-group-rich domains that aggregate the ionic groups to retain the residue water and ionic-group-sparse domains that create a hydrophobic surface and ionomer region with less water and thus increased oxygen solubility. Accordingly, the water-unsaturated ionomer and its surface hydrophobicity enhance both kinetic-controlled and mass-transfer-affected regions of the fuel cell polarization curve, respectively. The surface hydrophobicity of the ionomer layer is studied by the contact angle measurement and XPS. The durability of the hydrophobic effect below Tg is demonstrated by the boiling of the treated material. Re-treating the hydrophobic sample with humidified gas exposure while above Tg, which eventually exhibits a hydrophilic feature, further proves the manipulability of the ionic group distribution.

Citation

Journal of Polymer Science

Volume

61

Issue

8

Pub Type

Journals

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DOI Link

Keywords

PEM Fuel Cell, PFSA polymer, water flooding of cathode, nanostructure of PFSA

Citation

Li, Y. , Schwab, N. , Briber, R. , Dura, J. and Van Nguyen, T. (2023), Modification of Nafion's Nanostructure for the Water Management of PEM Fuel Cells, Journal of Polymer Science, [online], https://dx.doi.org/10.1002/pol.20220774 (Accessed December 3, 2024)