Photo-oxidative degradation of polybenzimidazole derivative membrane

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 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. © 2013 VBRI press.