Omkar S. Kushwaha; C. V. Avadhani; R. P. Singh
Abstract
Acid doped polybenzimidazole membranes have emerged as an efficient electrolyte for high temperature polymer electrolyte membrane fuel cells (HTPEMFCs). The long term stability of polybenzimidazole membranes has been recognized as an important issue for commercial applications. Here, we report the oxidative ...
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Acid doped polybenzimidazole membranes have emerged as an efficient electrolyte for high temperature polymer electrolyte membrane fuel cells (HTPEMFCs). The long term stability of polybenzimidazole membranes has been recognized as an important issue for commercial applications. Here, we report the oxidative degradation of polybenzimidazole membranes. The photoirradiation of poly(2,2'-ethylene-5,5'-bibenzimidazole) (PBIE) under accelerated photodegradation conditions was carried out by ultraviolet (UV) rays (λ > 300 nm) and characterized by Fourier transform infra red (FT-IR) spectroscopy, scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and contact angle measurements (CAM). The thermal properties of PBIE membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) which revealed a lowering in thermal stability after photodegradation. FT-IR spectra revealed high absorbance in the carbonyl region in photoirradiated membranes whereas SEM showed nano structures / defects on the polymer film surface. CAM results showed enhancement in hydrophilic behavior and WAXD revealed increase in amorphous nature upon irradiation.
Omkar S. Kushwaha; C. V. Avadhani; R. P. Singh
Abstract
High temperature polymer electrolyte membrane fuel cells (HTPEMFCs) are energy efficient systems with the potential to address all energy issues of present and future generations. Polybenzimidazole (PBI) based high temperature fuel cells are subject of high importance because PBI membranes are proved ...
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High temperature polymer electrolyte membrane fuel cells (HTPEMFCs) are energy efficient systems with the potential to address all energy issues of present and future generations. Polybenzimidazole (PBI) based high temperature fuel cells are subject of high importance because PBI membranes are proved to be one of the best candidates for high temperature fuel cell applications. The stability of PBI membranes has been identified as crucial issue for the long-term durability under oxidative conditions of fuel cells. The present investigation highlights the photo-oxidative degradation studies accomplished on polybenzimidazole based poly(2,2'-butylene-5,5'-bibenzimidazole) (PBIB) membranes. The PBIB polymer membranes are found suitable for both in high temperature fuel cells as well as other high temperature applications. In this research article, PBIB membranes were photoirradiated under polychromatic UV rays (λ > 290 nm). The photo-oxidative degradation of membranes was characterized by Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscopy (SEM). FT-IR results showed significant amount of photo-oxidation and chemical degradation in fuel cell membranes which is proposed to be initiated by free radical mechanism. SEM images revealed development of nano-dimensional cracks and holes on surface of membranes which indicate structural and morphological degradation. The present study showed better results of accelerated photo-degradation as compared to the oxidative degradation results already reported in literature obtained chemically and thermally. Hence, the proposed photo-oxidative degradation method may be useful in determining stability, life time expectancy and degradation mechanism of fuel cell and other high performance membranes.