Metal-Salt Enhanced Grafting of Vinylpyridine and Vinylimidazole Monomer Combinations in Radiation Grafted Membranes for High-Temperature PEM Fuel Cells

Abstract

Proton exchange membranes were prepared and characterized for utilization in high-temperature proton exchange membrane fuel cells, HT-PEMFCs. 1-vinylimidazole (1-VIm) and 4-vinylpyridine (4VP) monomers were simultaneously grafted onto pre-irradiated ETFE (ethylene-co-tetrafluoroethylene) films which were prepared using γ-rays with a dose of 100 kGy, as a robust substrate to prepare acid−base composite membranes. The grafting reaction was performed at 60°C for 24 h followed by protonation via phosphoric acid doping in the subsequent step. The effect of adding ferrous salts as promoters in grafting was investigated by characterization of resultant membranes via thermal gravimetric analysis and mechanical tests. The fuel cell tests were conducted under different relative humidities (RHs) and applied temperatures. Membranes prepared with salt addition exhibited superior proton conductivities. Results including up to 80 mS cm −1 conductivity at 110°C in 60% RH and excellent thermal stability, even at 300°C, suggest these membranes are promising for HT-PEMFC applications.

Composite Proton-Conducting Membrane with Enhanced Phosphoric Acid Doping of Basic Films Radiochemically Grafted with Binary Vinyl Heterocyclic Monomer Mixtures

“…Moreover, the performance of the membranes was found to be rather unsatisfactory and reports addressing their acid-leaching resistance and stability were not published. To further improve these membranes, RIG of comonomers (adding a second monomer to the main grafting monomer) was used to enhance the acid doping level by incorporating more basic characters and improving the stability of the membrane [ 34 , 35 ]. However, grafting binary monomer mixtures with a basic nature, such as 4-VP and 1-Vim, is challenging and requires understanding key issues, such as the effect of monomer reactivity ratio and its impact on the copolymer composition relative to the monomer mixture content and the sequence of alternation of individual monomer units in the copolymer, together with its impact on the acid doping level in the final composite membranes.…”

Monolithic Macromolecule Membrane Based on Polybenzimidazole: Achieving High Proton Conductivity and Low Fuel Permeability through Multiple Cross-Linking

“…The H 3 PO 4 -doped polybenzimidazole (PBI) membrane (PA/PBI) exhibits high proton conductivity at low relative humidity (RH) and high temperatures (above 100 °C). − In the membranes, the hydrogen-bond networks are constructed by the interaction between basic sites ( N ) on imidazole groups of PBI and strong acid groups, which can assist proton transfer. , The doping level and the intrinsic properties of acids significantly influence the proton conductivity of these membranes. The excellent properties of PA/PBI still have several drawbacks: (i) the water-soluble acids leach from the membrane under elevated hydration level; , (ii) high acid doping leads to PBI main-chain-separated and deteriorated mechanical properties of membranes. , …”

Scalable, safer and greener syntheses of vinylimidazoles via reactive distillation of hydroxyethylimidazole intermediates

“…HCO 3 − ) or carbamate forms. Polymers formed from 1‐vinylimidazole (and related derivatives such as 1‐vinyl‐2‐methylimidazole) have been extensively researched within homo‐ or copolymers for use in applications including gas separation, 11, 12 gene delivery, 13 metal binding and removal, 14–19 hydrogels, 12 flame retardation, 20 wearable technology 21 and for grafting or surface modification of other materials 22, 23 as well as the various applications for poly(ionic liquid)s formed from vinylimidazolium salts.…”