Abstract:
Low-temperature proton exchange membrane fuel cells (PEMFCs) share many significant challenges in the performance, life-span, and industrial use of these membranes because of their degradation. This review synthesizes the current state of knowledge of the dominant degradation mechanisms acting on PEMs, namely mechanical stress, thermal degradation, and chemical attacks by reactive oxygen species (ROS). It is concluded that although mechanical degradation brought about by varying pressure and hydration cycles, membrane reinforcement with materials such as expanded polytetrafluoroethylene (ePTFE) and diverse composite membranes has somewhat mitigated the structural strength and toughness. Thermal and chemical degradation remains as principal challenges which are most often hastened by elevated temperatures and formation of reactive free radicals such as hydroxyl and hydrogen peroxide. Hence, to counteract chemical degradation, the addition of radical scavengers like cerium oxide (CeO2) and manganese-based additives can scavenge the destructive species even before this cause significant damage. Other new materials for PEM such as perfluorosulfonic acid (PFSA) composites have demonstrated enhanced resistance in chemical environments and a longer life. This includes research on innovative approaches such as introducing ionomers with improved thermal stability and evaluating hybrid organic-inorganic membranes in fighting the degradation mechanism of thermal degradations. This review brings out the need to understand the degradation mechanisms and advance mitigation strategies to ensure elongation of PEMFCs' life, thus paving a way for their reliability and feasibility as clean energy.