Properties of SPEEK based PEMs for fuel cell application

Abstract

Comparative studies of membranes prepared using different solvents, have shown that the casting solvent plays a significant role, affecting their proton conductivity and mechanical strength. It has been found that using DMF strongly decreases the membrane conductivity in comparison with other solvents studied. The 1 H NMR results yield an insight into the mechanism of this effect, evidencing the formation of the strong hydrogen bonding of sulfonic acid groups with DMF. This can explain the large discordances of more than an order of magnitude existing between the conductivity results for sulfonated polyetheretherketone (PEEK) in some previous studies and in this work. It is also found that residual sulphuric acid, which is very difficult to eliminate from highly sulfonated polyetheretherketone (SPEEK), also affects its conductivity and under high temperature treatment, enters into reaction with both DMF and N,N-dimethylacetamide (DMAc), causing their degradation. As discussed in the present contribution, the conductivity measurement technique may also be a reason for discrepancy in the reported conductivity characteristics of SPEEK.

High temperature (HT) polymer electrolyte membrane fuel cells (PEMFC) – A review

“…This includes choice of solvent, extrusion versus casting and thermal post-treatment [56,76]. When inorganic additives are used, the preparation of the additive as well as the composite membrane materials are crucial to the performance of the materials Table 5 summarises data on promising high temperature membrane materials and the entries that are highlighted have met DoE targets for 2015.…”

Surface orientation of hydrophilic groups in sulfonated poly(ether ether ketone) membranes

“…The post sulfonation of PEEK (Victrex PLC) was run using concentrated sulfuric acid according to the procedure described elsewhere [9,18]. The process was detailed in supporting information.…”

Proton conducting membranes based on cross-linked sulfonated poly(ether ether ketone) (SPEEK)

“…It is apparent that cross-linking is blocked by the competing reaction of sulfonic acid groups with DMAc or NMP. Recently it has been shown that DMAc and especially DMF form strong hydrogen bonding with sulfonated PEEK [11,12]. Moreover, both solvents have been found to be prone to thermally activated decomposition, accelerated by sulfonic acid functions and the produced dimethylamine also forms strong bonding with SPEEK [11,12].…”

“…Recently it has been shown that DMAc and especially DMF form strong hydrogen bonding with sulfonated PEEK [11,12]. Moreover, both solvents have been found to be prone to thermally activated decomposition, accelerated by sulfonic acid functions and the produced dimethylamine also forms strong bonding with SPEEK [11,12]. It is therefore preferable to avoid these solvents for membrane casting, replacing them wherever possible (SPEEK with DS > 0.8) by water or water-acetone mixtures.…”