Innovative integration of MXenes in ion-conductive polymer membranes: synthesis, properties, and applications

Water purification and a variety of electrochemical energy conversion and storage devices, such as fuel cells, electrolyzers, and redox flow batteries, depend heavily on ion-conductive polymer membranes. When the polymers are functionalized with ionic groups (e.g., sulfonic acid, amine, carboxylate) to impart fixed charges, this enables their use as polyelectrolyte membranes (PEMs). To increase the overall effectiveness and robustness of these devices, high-performance PEM development is crucial. Because of their special qualities, MXenes, a category of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides, have become attractive fillers for PEMs in recent times. This article focuses on introducing the fundamental properties of MXenes; their types, properties, and methods of synthesis, including the widely used etching and delamination techniques, are discussed to highlight their compatibility with PEM fabrication processes. Reported interactions between MXenes and various polyelectrolytes such as sulfonated and other functionalized polymers are discussed to illustrate the role they play in composite membrane formation and their impact on membrane properties. The effects of MXene incorporation on key performance indicators, including electrical conductivity, mechanical strength, and chemical stability, are analysed. Additionally, the influence of loading levels, dispersion methods, and surface modifications on membrane performance is highlighted. This review summarizes recent advancements, provides insights for the design of MXene-based PEMs, and outlines future directions for their practical deployment.