Synthesis of a proton exchange membrane from SEBS copolymer and natural latex modified with V2O5 for fuel cells

Abstract

In the present work, proton exchange membranes were prepared from SEBS copolymer and natural latex modified with vanadium pentoxide (V2O5) to evaluate its performance as an electrolyte in a fuel cell through the characterization of its physicochemical and mechanical properties. The results show that the 0.5% V2O5 addition was favorable for the water absorption test due to its hydrophilic character. The ion exchange capacity had a similar behavior since water is the means for the main mechanisms of protons to occur inside the membrane. The stretching properties and maximum effort decrease with increasing the V2O5 load, but it boosted the Young's modulus. With the FTIR analysis, the presence of V2O5 was verified in the loaded membranes. Therefore, it is necessary to improve ion exchange capacity and mechanical properties to apply this membranes as an electrolyte in a fuel cell.

Effect of the sulfonation on membranes synthetized from SEBS and natural latex

“…For the loaded and sulfonated membranes, a solution similar to that used for the sulfonated membrane 1 hour was prepared. Once the sulfonated polymer was dissolved in 80 mL of toluene, 0.5 mL of latekoll was added to the solution for 2 hours with continuous stirring [5], then 0.01 g of V2O5 corresponding to the 0.5% load was added and 4 hours later the solution was allowed to reach a level of 25 mL to start the drying stage in a Petri dish and obtain the membrane loaded 0.5% and sulfonated 1 hour. A similar procedure was repeated substituting the load amount for 0.02 g of V2O5 to obtain the membrane loaded 1.0% and sulfonated for 1 hour.…”

“…The signals in 1124 cm -1 and 1164 cm -1 are appreciated in the sulfonated membranes, corresponding to vibrations of the sulfonic acid groups in the aromatic rings, while the wide absorbance peak in 3200-3600 cm -1 is attributed to the O-H bond vibrations [16]. Finally, the presence of vanadium pentoxide is evidenced by a peak near 1000 cm -1 corresponding to the vibration mode of terminal oxygen bond V=O and in 829 cm -1 with the vibration of the V-O-V bond [5].…”

“…The water uptake was obtained by immersing samples of each membrane in distilled water for 24 hours, the samples were weighed before (Ws) and after immersing (Wh), they were superficially dried with absorbent paper and then the percentage of water absorption calculated through weight variation [5]. The ion exchange capacity was calculated by applying the titration method, in which the samples were immersed in a 1 M HCl solution for 24 hours, then placed in a 1 M NaCl solution for a further 24 hours, finally the samples were extracted and a titration was carried out with 0.01 NaOH [4].…”

“…The sulfonated membranes have higher values than the unmodified membrane, highlighting the sulfonated membrane 2 hours, which has the largest Young's modulus of all the synthesized membranes, it has the best resistance to stretching, that is attributed to the sulfonation increases the polarity of the polymer and improves the mechanical properties through the hydrogen bond between the chains of the polymer [12]. The loaded and sulfonated membranes have the lowest values compared to the unmodified membrane and the sulfonated membranes, attributed to the fact that the presence of excess inorganic load can cause a non-uniform dispersion in the polymer matrix, leading to a poor response of the membrane when this is subjected to the action of external forces [5].…”