Novel Pyridine-Based Poly(ether sulfones) and their Study in High Temperature PEM Fuel Cells

Abstract

Novel pyridine-based aromatic copolymers containing 4,4′-biphenol or hydroquinone groups in the main chain were synthesized and characterized as polymer electrolytes for proton exchange membrane fuel cells (PEMFCs). Depending on the copolymer composition and pyridine monomer content in most cases soluble and high molecular weight copolymers were obtained. Flexible membrane films were prepared by casting N,Ndimethylacetamide (DMA C ) solutions of copolymers. 1 H NMR and size exclusion chromatography were used to characterize the structures of the copolymers. High glass transition temperatures (T g s) and decomposition temperatures (T d s) were observed using dynamic mechanical analysis and thermogravimetry, respectively. The oxidative stability of the membranes was examined with Fenton′s test. The doping ability and the proton conductivity of the membranes were also studied and the new copolymers can be potential candidates as new polymeric electrolyte materials for proton exchange membrane fuel cells. Finally, membrane electrode assemblies (MEAs) were constructed and tested in 25 cm 2 single cell at different temperatures showing promising performance.

Fully Aromatic Copolyethers for High Temperature Polymer Electrolyte Membrane Fuel Cells

“…As is presented in this work, see Figure 8, in the case of copolymer II, conductivity values slightly increase as its doping level increases from 80 to 270 wt.-%. Comparing with our previous work [26], copolymers with more linear structure (bearing sulfone groups instead of phosphinoxide) show slightly better conductivity. A factor that seems to be of interest is the introduction of aliphatic side groups like methyl groups in the tetramethyl biphenol monomer used in the case of copolymer I.…”

“…TGA measurements of copolymer I doped at levels ranging between 150 and 200% showed that, probably due to a plasticisation that takes place upon acid doping, at temperatures above 130°C the material starts to exhibit a viscoelastic behaviour while retaining its mechanical integrity. This phenomenon does not reflect to materials that bear the sulfone group instead of the phosphinoxide one, as clearly shown in our previous work [25][26][27]. Furthermore, a difference in the chain conformation or the phase separation in the presence of phosphoric acid could result to this differentiation in the behaviour of the copolymers studied in this work in comparison to previously studied copolymers.…”

“…An alternative approach is based on the use of pyridinecontaining aromatic polyethers [23][24][25][26] that are able to be doped with phosphoric acid and produce membranes with proton conductivities in the range of 10 -2 S cm -1 . At the same time the oxidative stability of the membranes is exceptionally good and they have been effectively used in polymer electrolyte fuel cells operating at up to 200°C [27].…”

H3PO4-imbibed three-dimensional polyacrylamide/polyacrylamide hydrogel as a high-temperature proton exchange membrane with excellent acid retention

“…Therefore, the membranes are imbibed in the highly concentrated H 3 PO 4 solution for high H 3 PO 4 loading. In previous H 3 PO 4 -doped PBI studies, 11 to 14 M solutions are always employed as the optimal concentrations of H 3 PO 4 solutions, [28][29][30][31] However, the results shown in Fig. 3 are in apparent disagreement with this empirical rule of thumb.…”

Catalyst, Membrane, Free Electrolyte Challenges, and Pathways to Resolutions in High Temperature Polymer Electrolyte Membrane Fuel Cells

“…Pyridine based membranes such as Advent Technologies TPS membrane have also been investigated for HT-PEMFC applications [10][11][12][13][14][15][16]. These membranes exhibit glass transition temperatures of~270 …”