Advances in perfluorosulfonic acid-based proton exchange membranes for fuel cell applications: A review

Among all fuel cells, proton exchange membrane fuel cells (PEMFCs) are appealing energy conversion devices in portable and transportation applications because of their higher efficiency, excellent ability to reduce air pollution, lightweight, generation of less noise due to the absence of mechanical components, quick start-up time and non-involvement in the combustion process. This review article emphasizes the importance of perfluorosulfonic acid (PFSA) polymer-based proton exchange membranes (PEMs) for fuel cell applications and their recent achievements, difficulties, and prospects. The most widely used PEMs for low-temperature PEMFCs are PFSA polymer-based membranes and some non-fluorinated polymers such as sulfonated poly(ether ketone) (SPEEK), sulfonated polysulfone (SPSF), sulfonated polyimide (SPI), and sulfonated polystyrene (SPS). Among these PEMs, PFSA membranes (such as Nafion) are the most often utilized low-temperature PEM for fuel cell applications because of their outstanding chemical, mechanical, and thermal stability with higher proton conductivity under-hydrated conditions. Due to some limitations of PFSA membranes, such as poor conductivity in anhydrous conditions, high manufacturing costs, and degradation of their properties at higher temperatures, research on low-temperature PEM has been shifted to the development of polymer electrolyte composite membranes incorporating various multifunctional organic, inorganic, and hybrid fillers. The PFSA polymer composite membranes show better chemical, thermal, and oxidative stability with higher proton conductivity and fuel cell performance than pristine PFSA membranes. In addition, the PFSA polymer composite membranes maintain proton conductivity and fuel cell performance in low humidity conditions. These findings show that developing suitable PFSA polymer composite membranes could enhance the possibility of commercial applications of PEMFCs.