Blend Membranes Consisting of Sulfonated Poly(ether ether ketone) and 1H-Perimidine Tethered Polysulfone for Direct Methanol Fuel Cells

Acid–base blend membranes consisting of sulfonated poly(ether ether ketone) and 5-amino-benzotriazole tethered polysulfone for DMFC

“…The SPEEK was synthesized by a sulfonation reaction using concentrated sulfuric acid as both a solvent and a sulfonating agent, and the detailed procedure has been reported elsewhere [23]. The degree of sulfonation was controlled by changing the reaction time.…”

“…In this study, SPEEK with an IEC of 1.42 meq/g was used. The polysulfones tethered with different heterocycles (BIm, ABIm, NBIm, PImd) were synthesized using CPSf-158 as a precursor and following the procedure reported before [20][21][22][23].…”

“…Since there is a greater number of sulfonic acid groups compared to the number of heterocycle groups in the blend membranes, the vehicle-type proton conduction mechanism is predominant, while the Grotthuss-type mechanism involving the nitrogen atoms on the heterocycles may provide an enhancement in the proton conduction by providing additional proton transfer "bridges". Moreover, the insertion of the heterocycles into the ionic clusters formed by the sulfonic acid groups could broaden the proton transfer channels [22,23], resulting in an enhancement in the vehicle mechanism. The longer side chains of PSf-BTraz and the higher number of nitrogen sites (four) in the 5-amino-benzotriazole groups may facilitate easier proton hopping in the SPEEK/PSf-BTraz blend membranes compared to that in the SPEEK/PSf-BIm; in fact, the latter exhibits lower proton conductivity compared to the former with the same [-SO 3 H]/[heterocycle] ratio as shown in Table 3.…”

“…It is worth mentioning that although using oxygen versus air at the cathode will have an influence on the absolute values of the power density in DMFC, by increasing the flow rate and back pressure of the air supply, DMFC performances similar to that obtained with oxygen as an oxidant could be achieved in a DMFC for the blend membrane [37,38]. Nevertheless, to investigate the effect of oxygen versus air on the performance of the acid-base blend membranes in DMFC, we have presented a comparison of similar blend membranes (SPEEK/PSf-PImd blend membranes) with oxygen and air as oxidants [23]. The performance of the acid-base blend membrane with air feeding to cathode is lower compared to that with oxygen feeding due to the lower oxygen concentration in the cathode side.…”

“…Because of this reason, more attention is being directed towards the development of ionomer networks containing ionically cross-linked blend systems such as SPPO (poly(2,6-dimethyl-1,4-phenylene oxide))/PBI (polybenzimidazole respectively), SPEEK/PBI, and SPSf/aminated PSf, which are more flexible [16][17][18][19]. Our group reported recently [20][21][22][23] that blend membranes based on acid-base interactions between the sulfonic acid groups of SPEEK and the N-heterocycle groups (benzimidazole (BIm), amino-benzimidazole (ABIm), nitrobenzimidazole (NBIm), and 1H-perimidine (PImd)) tethered to PSf show improved DMFC performance compared to plain SPEEK membranes due to both suppressed methanol crossover and enhanced proton conductivity. This blend membrane concept is based on industrially available, inexpensive polymer precursors like PEEK and PSf, which are compatible with each other due to their similar aromatic backbones.…”