Preparation of Polybenzimidazole-Based Membranes and Their Potential Applications in the Fuel Cell System

Kyungho Hwang,Jun-Hyun Kim,Sung-Yul Kim,Hongsik Byun

doi:10.3390/en7031721

Kyungho Hwang, Jun-Hyun Kim + Show 2 more

Open Access

https://doi.org/10.3390/en7031721

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Journal: Energies	Publication Date: Mar 24, 2014
Citations: 48	License type: CC BY 3.0

Affiliation: Keimyung University, Illinois State University

Abstract

Various polybenzimidazole (PBI)-based ion-exchange films were prepared and thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, proton conductivity, and water uptake for possible use as fuel cell membranes. Upon the increase in the flexibility of the PBI-based polymer films (e.g., poly(oxyphenylene benzimidazole) (OPBI) and sulfonated OPBI (s-OPBI)), the membranes exhibited slightly improved proton conductivity, but significantly increased dimensional changes. To reduce the dimensional changes (i.e., increase the stability), the cross-linking of the polymer films (e.g., cross-linked OPBI (c-OPBI) and sulfonated c-OPBI (sc-OPBI)) was accomplished using phosphoric acid. Interestingly, the sc-OPBI membrane possessed a greatly increased proton conductivity (0.082 S/cm), which is comparable to that of the commercially available Nafion membrane (0.09 S/cm), while still maintaining slightly better properties regarding the dimensional change and water uptake than those of the Nafion membrane.

Highlights

The proton exchange membrane fuel cell (PEMFC), which possesses the ability to withstand high operating temperatures and is energy efficient, is a promising device for resolving both energy and environmental concerns [1,2]
The OPBI membrane is further sulfonated by sulfuric acid and/or cross-linked by phosphoric acid to improve the proton conductivity and maintain a good stability at high operating temperatures, which could surpass the limitations of current proton conductive membranes
As the successful sulfonation of the PBI film was examined by Fourier transform infrared (FT-IR), we analyzed the OPBI film and the series of cross-linked OPBI (c-OPBI)-based films as a function of the degree of sulfonation

Summary

Introduction

The proton exchange membrane fuel cell (PEMFC), which possesses the ability to withstand high operating temperatures and is energy efficient, is a promising device for resolving both energy and environmental concerns [1,2]. Acid doping into aromatic polymer materials is one of the more interesting approaches in designing proton conductive films with good thermal and chemical stabilities for alternative fuel cell membranes (e.g., polyimides, polysulfones, polybenzoxazoles, poly(ether ether ketones), and polybenzimidazoles (PBIs)) [2,4,5,6,8,9,10,11,12,13]. The OPBI membrane is further sulfonated by sulfuric acid and/or cross-linked by phosphoric acid to improve the proton conductivity and maintain a good stability at high operating temperatures, which could surpass the limitations of current proton conductive membranes.

Materials

FT-IR of PBI and s-PBI Membranes

Conclusions