Performance optimization by antioxidant strategies for proton exchange membrane fuel cells: Recent progress and future

• Reactive oxygen species generation and destruction mechanisms are introduced. • Free radical scavengers and deactivation mechanisms in PEMFCs are underscored. • Material design and scavenging mechanisms for free radical scavengers are reviewed. • Advantages and limitations of free radical scavengers are highlighted. • The significance of in-situ detection techniques is emphasized. Although proton exchange membrane fuel cells (PEMFCs) have become a potential replacement for traditional energy sources because of their minimal environmental impact and superior efficiency, their vulnerability to degradation caused by in situ generated peroxide and oxygen radical species has seriously hindered their widespread application. To mitigate the negative effects of chemical attack on components of PEMFCs, especially on proton exchange membranes (PEMs), there has been significant efforts devoted in employing antioxidant strategies as the preferred solution, which can directly eliminate and remove harmful peroxide and oxygen radical species. However, due to the rigorous operating conditions, such as low pH, electric potential, water flow, and ion exchange/concentration gradient, undesirable degradation occurred for antioxidant additives. Moreover, the diminished activity and capability of antioxidants resulting from alterations in the physical state, such as migration, agglomeration, and dissolution, are also crucial factors to be taken into account. In this review, we mainly focus on the recent advancements in antioxidant therapy in enhancing the durability of PEMs, especially offering a comprehensive overview of advanced techniques for designing synthetic compounds and conducting thorough analyses of antioxidants to enhance activity-stability factors, aiming to inspire further advancements in this exciting field.