A facile method for the preparation of poly(vinylidene fluoride) membranes filled with cross-linked sulfonated polystyrene

Enhanced Performance and Durability of Pore-Filling Membranes for Anion Exchange Membrane Water Electrolysis

Four distinct pore-filling anion exchange membranes (PFAEMs) were prepared, and their mechanical properties, ion conductivity, and performance in anion exchange membrane water electrolysis (AEMWE) were evaluated. The fabricated PFAEMs demonstrated exceptional tensile strength, which was approximately 14 times higher than that of the commercial membrane, despite being nearly half as thin. Ion conductivity measurements revealed that acrylamide-based membranes outperformed benzyl-based ones, exhibiting 25% and 41% higher conductivity when using crosslinkers with two and three crosslinking sites, respectively. The AEMWE performance directly correlated with the hydrophilicity and ion exchange capacity (IEC) of the membranes. Specifically, AE_3C achieved the highest performance, supported by its superior IEC and ionic conductivity. Durability tests showed that AE_3C outlasted the commercial membrane, with a delayed voltage increase corresponding to its higher IEC, confirming the importance of increased ion-exchange functional groups in ensuring longevity. These results highlight the critical role of hydrophilic monomers and crosslinker structure in optimizing PFAEMs for enhanced performance and durability in AEMWE applications.

Ionic Mobility in Ion-Exchange Membranes

Membrane technologies are widely demanded in a number of modern industries. Ion-exchange membranes are one of the most widespread and demanded types of membranes. Their main task is the selective transfer of certain ions and prevention of transfer of other ions or molecules, and the most important characteristics are ionic conductivity and selectivity of transfer processes. Both parameters are determined by ionic and molecular mobility in membranes. To study this mobility, the main techniques used are nuclear magnetic resonance and impedance spectroscopy. In this comprehensive review, mechanisms of transfer processes in various ion-exchange membranes, including homogeneous, heterogeneous, and hybrid ones, are discussed. Correlations of structures of ion-exchange membranes and their hydration with ion transport mechanisms are also reviewed. The features of proton transfer, which plays a decisive role in the membrane used in fuel cells and electrolyzers, are highlighted. These devices largely determine development of hydrogen energy in the modern world. The features of ion transfer in heterogeneous and hybrid membranes with inorganic nanoparticles are also discussed.

Selectivity of Transport Processes in Ion-Exchange Membranes: Relationship with the Structure and Methods for Its Improvement

Nowadays, ion-exchange membranes have numerous applications in water desalination, electrolysis, chemistry, food, health, energy, environment and other fields. All of these applications require high selectivity of ion transfer, i.e., high membrane permselectivity. The transport properties of ion-exchange membranes are determined by their structure, composition and preparation method. For various applications, the selectivity of transfer processes can be characterized by different parameters, for example, by the transport number of counterions (permselectivity in electrodialysis) or by the ratio of ionic conductivity to the permeability of some gases (crossover in fuel cells). However, in most cases there is a correlation: the higher the flux density of the target component through the membrane, the lower the selectivity of the process. This correlation has two aspects: first, it follows from the membrane material properties, often expressed as the trade-off between membrane permeability and permselectivity; and, second, it is due to the concentration polarization phenomenon, which increases with an increase in the applied driving force. In this review, both aspects are considered. Recent research and progress in the membrane selectivity improvement, mainly including a number of approaches as crosslinking, nanoparticle doping, surface modification, and the use of special synthetic methods (e.g., synthesis of grafted membranes or membranes with a fairly rigid three-dimensional matrix) are summarized. These approaches are promising for the ion-exchange membranes synthesis for electrodialysis, alternative energy, and the valuable component extraction from natural or waste-water. Perspectives on future development in this research field are also discussed.