High performance polymer electrolyte membrane with efficient proton pathway over a wide humidity range and effective cross-linking network

Deep eutectic solvent-supported poly(vinyl) alcohol electrospun anion-exchange membrane for potential application in alkaline fuel cells

This research introduces a new method to synthesize poly(vinyl) alcohol (PVA)-based deep eutectic solvent (DES)-supported anion-exchange membranes (AEMs) for alkaline fuel cell (AFC) applications. The fabrication method involved the modification of a PVA-based crosslinked nanofiber mat with DES prepared by mixing choline chloride (ChCl) and ethylene glycol (EG) in a 1:3 molar ratio. Various concentrations of glutaraldehyde (GA) solution were used to cross-link of the PVA fibers. The composite AEM developed using DES was designated as DES3@PVA4 and showed improved performance with a high hydroxide conductivity of 1.05 mS/cm at 60 °C, which is higher than that of the unmodified AEM (0.77 ± 0.01 mS/cm at 60 °C). The absence of swelling, enhanced elongation at break, and improved alkaline stability were further confirmed for the DES-modified AEM; the ionic conductivity remained stable after one month of soaking in 1 M potassium hydroxide solution. These results demonstrate that DES-enhanced PVA-based AEMs can be used for AFCs with improved conductivity, flexibility, mechanical strength, and alkaline stability compared to conventional AEMs.

Highly proton-conductive and low swelling polymeric membranes achieved by hydrophilic covalent cross-linking

Proton exchange membranes (PEMs) applied in fuel cell technology suffer from the trade-off between fast proton conduction and durable operation involving dimensional stability, mechanical strength, and oxidative resistance. To address this issue, a novel branched polybenzimidazole (brPBI) was synthesized, covalently cross-linked with (3-chloropropyl)triethoxysilane (CTS), and doped with a novel proton conductor FeATMP to prepare brPBI-CTS/FeATMP membranes. The branching degree of brPBI was optimized to achieve high molecular weight while the branching structure offered high free volume, abundant end-groups, and self-cross-linking moiety that enhanced proton conduction and dimensional/mechanical/oxidative stability. Covalent cross-linking with CTS enhanced the dimensional, mechanical, and oxidative stability while improving the water-assisted proton conduction owing to the hydrophilic nature of siloxane structure formed. At 180 ℃, the proton conductivity of the brPBI3-CTS/FeATMP composite membrane reached 0.136, 0.073, and 0.041 S cm-1 at 100 % RH, 50 % RH, and 0 % RH, respectively, while its swelling ratio after immersion in water at 90 ℃ for 24 h was 4.69 %. The performance of the membranes demonstrated that construction of hydrophilic structure by covalent cross-linking was a successful strategy to break the trade-off effect for PEMs.

Construction of Highly Conductive Cross-Linked Polybenzimidazole-Based Networks for High-Temperature Proton Exchange Membrane Fuel Cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) are of great interest to researchers in industry and academia because of their wide range of applications. This review lists some creative cross-linked polybenzimidazole-based membranes that have been prepared in recent years. Based on the investigation into their chemical structure, the properties of cross-linked polybenzimidazole-based membranes and the prospect of their future applications are discussed. The focus is on the construction of cross-linked structure of various types of polybenzimidazole-based membranes and their effect on proton conductivity. This review expresses the outlook and good expectation of the future direction of cross-linked polybenzimidazole membranes.