Different cationic functionalized epichlorohydrin modified polyvinyl alcohol based anion exchange membrane

Abstract

Low ionic conductivity and poor alkali resistance have long been the problems of the anion exchange membrane (AEM) of alkaline fuel cell. Herein, epichlorohydrin functionalized by three different cations (piperidine cation, imidazole cation and trimethylammonium cation) are respectively used to modify polyvinyl alcohol (PVA) to prepare a series of PVA based AEMs, and the AEMs are cross‐linked by p‐phthalaldehyde. 1H NMR and FT‐IR spectroscopy confirm the successful functionalization of epichlorohydrin and the successful preparation of the AEMs. The ion exchange capacity, water uptake, swelling ratio, mechanical properties, thermal stability, OH− conductivity, morphology and alkaline stability of the AEMs are assessed and compared. The experimental results suggest that the AEM modified by piperidine cation owns continuous ion channels and obvious microphase separation structure, resulting in an OH− conductivity of 94.13 mS cm−1 at 80°C. And its alkali resistance is also relatively good (87.16%, 360 h). Besides, crosslinking by p‐phthalaldehyde effectively lowers the swelling ratio, increases the thermal stability and improves the mechanical properties of the AEMs.

In-Situ Gradient Cross-Linking in Anion Exchange Membranes for Water Electrolyzers

“…The FT-IR spectrum demonstrates the presence of epoxy, with a distinctive peak at approximately 902 cm –1 (C–O stretching vibration), indicating the successful coupling of epoxy groups in the side chain (see Figure S9). The decline in the 1630 cm –1 (CC stretching vibration) peak in Figure S10 indicates the effective in-situ cross-linking reaction of the PNTP-IC membrane . All three ionomers, containing either an epoxy group or a vinyl group, have thermal decomposition temperatures above 170 °C, meeting the operating conditions for water electrolyzers (Figure S11).…”

“…Figure 1 illustrates the synthesis strategy for poly(naphthol− triphenyl−piperidone) (PNTP) functionalized with Br-epoxy, (see Figure S9). 57 The decline in the 1630 cm −1 (C�C stretching vibration) peak in Figure S10 indicates the effective in-situ cross-linking reaction of the PNTP-IC membrane. 15 All three ionomers, containing either an epoxy group or a vinyl group, have thermal decomposition temperatures above 170 °C, meeting the operating conditions for water electrolyzers (Figure S11).…”

“…The gradient self-cross-linking reaction of PNTP-GC, catalyzed by hydroxide ions (OH − ), follows the mechanism illustrated in the dotted box (Figure 3f). 57 The OH − ion, as a nucleophilic reagent, attacks carbon atoms with low site resistance, undergoing S N 2 nucleophilic substitution reactions. Finally, an alkyl ether cross-linking structure is formed over time.…”

“…Besides, the gradual decrease of the infrared absorption peaks at 902 cm –1 is attributed to the open ring of epoxy and also proves the occurrence of gradient cross-linking, , as shown in Figure S21. The gradient self-cross-linking reaction of PNTP-GC, catalyzed by hydroxide ions (OH – ), follows the mechanism illustrated in the dotted box (Figure f) . The OH – ion, as a nucleophilic reagent, attacks carbon atoms with low site resistance, undergoing S N 2 nucleophilic substitution reactions.…”

Preparation and Properties of Poly(Vinyl Alcohol)-Based Anion-Exchange Membranes with Different Cross-Linked Structures

“…To investigate the effect of cross-linking on the membrane properties, piperidine-functionalized PVA (PVA-MP) was prepared in this study as a non-cross-linking AEM, in which the reaction ratio of piperidine cation to PVA was 3:1, and the specific synthesis steps were according to to previous reports. 29 The molecular structure of PVA-MP is shown in Figure 1.…”