Emerging Polybenzimidazole Membranes for Green Energy Conversion Devices (2nd Edition)

Dear Colleagues, 

The introduction of the third decade of the emerging green energy revolution, and hydrogen-based energetics in particular, has increased the use of electrochemical devices for energy conversion such as hydrogen fuel cells, co-generation systems, water and low-alcohol electrolyzers, and flow batteries, among others. In all these devices, a core component is the solid polymer electrolyte separation membrane, where the thermally and chemically robust aromatic polybenzimidazoles (PBIs) and their ionomeric derivatives are a significant material of choice since the pioneering discovery of the peculiar and promising proton conductivity properties of amphoteric PBI membranes doped with ortho-phosphoric acid (PBI/PA) by R. F. Savinell et al. in the mid-1990s. Since then, PBI-based membranes doped with either mineral acids (H+ conductive), alkali bases (OH- conductive), ionic liquids, or ion-exchange derivatives with their intrinsic ionic conductivity have not only gained great popularity among the research community but have also, most significantly, found their way into real commercialization as a close rival of perfluorinated super acid ionomeric membrane-based technology. During this time, two main groups of PBI membrane emerged: (i) the so-called ion-solvating PBI membranes, where the PBI matrix is solvated by an excess number of low-electrolyte molecules with predominantly ionic interactions within the free electrolyte media; and (ii) the ion-exchange derivative PBI membranes with significantly expressed hydrated form self-conductivity, where the main chain PBI is chemically modified with ion-exchange side groups. In both cases, factors such as reaching highly concentrated forms of electrolyte doping for the ion-solvating, high ionomeric density and, particularly, high alkaline concentration stability for the ionomeric-based PBI membrane are still challenging. Here, the ion-enhancing and mechanical reinforcing properties of different inorganic fillers (e.g., natural and synthetic (alumo)silicates, carbon-based micro- and nanofillers such as graphene and carbon nanotubes, etc.) play a significant intermediate role in PBI membranes’ property tuning. 

This Special Issue on emerging polybenzimidazole membranes for green energy conversion devices in the Membranes journal seeks contributions to assess state-of-the-art and conceptual developments in the field of PBI separation membranes for fuel cells, electrolyzers, and flow batteries. Topics include, but are not limited to, new PBI membrane developments, composite membranes, chemical modification and cross-linking, manufacturing/stabilization techniques, characterization, fuel cell/electrolyzers and ox-red flow battery application, industrial exploitation, and perspectives. Authors are invited to submit their latest results—both original papers and reviews are welcome.

Dr. Hristo Penchev
Guest Editor

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• PBI membrane developments
• composite membranes
• chemical modification and cross-linking
• manufacturing/stabilization techniques
• fuel cell/electrolyzers and ox-red flow battery application
• industrial exploitation and perspective