Towards high-performance and robust anion exchange membranes (AEMs) for water electrolysis: Super-acid-catalyzed synthesis of AEMs

The increasing demand for hydrogen energy to address environmental issues and achieve carbon neutrality has elevated interest in green hydrogen production, which does not rely on fossil fuels. Among various hydrogen production technologies, anion exchange membrane water electrolyzer (AEMWE) has emerged as a next-generation technology known for its high hydrogen production efficiency and its ability to use non-metal catalysts. However, this technology faces significant challenges, particularly in terms of the membrane durability and low conductivity. To address these challenges, research efforts have focused on developing membranes with a new backbone structure and anion exchange groups to enhance durability and conductivity. Notably, the super-acid-catalyzed condensation (SACC) synthesis method stands out due to its user convenience, the ability to create high molecular weight (MW) polymers, and the use of oxygen-tolerant organic catalysts. Although the synthesis of anion exchange membranes (AEMs) using the SACC method began in 2015, and despite growing interest in this synthesis approach, there remains a scarcity of review papers focusing on AEMs synthesized using the SACC method. The review covers the basics of SACC synthesis, presents various polymers synthesized using this method, and summarizes the development of these polymers, particularly their building blocks including aryl, ketone, and anion exchange groups. We systematically describe the effects of changes in the molecular structure of each polymer component, conducted by various research groups, on the mechanical properties, conductivity, and operational stability of the membrane. This review will provide insights into the development of AEMs with superior performance and operational stability suitable for water electrolysis applications.