Enhanced Proton Transfer in Proton‐Exchange Membranes with Interconnected and Zwitterion‐Functionalized Covalent Porous Material Structures

Abstract

Excellent proton‐conductive accelerators are indispensable for efficient proton‐exchange membranes (PEMs). Covalent porous materials (CPMs), with adjustable functionalities and well‐ordered porosities, show much promise as effective proton‐conductive accelerators. In this study, an interconnected and zwitterion‐functionalized CPM structure based on carbon nanotubes and a Schiff‐base network (CNT@ZSNW‐1) is constructed as a highly efficient proton‐conducting accelerator by in situ growth of SNW‐1 onto carbon nanotubes (CNTs) and subsequent zwitterion functionalization. A composite PEM with enhanced proton conduction is acquired by integrating CNT@ZSNW‐1 with Nafion. Zwitterion functionalization offers additional proton‐conducting sites and promotes the water retention capacity. Moreover, the interconnected structure of CNT@ZSNW‐1 induces a more consecutive arrangement of ionic clusters, which significantly relieves the proton transfer barrier of the composite PEM and increases its proton conductivity to 0.287 S cm−1 under 95 % RH at 90 °C (about 2.2 times that of the recast Nafion, 0.131 S cm−1). Furthermore, the composite PEM displays a peak power density of 39.6 mW cm−2 in a direct methanol fuel cell, which is significantly higher than that of the recast Nafion (19.9 mW cm−2). This study affords a potential reference for devising and preparing functionalized CPMs with optimized structures to expedite proton transfer in PEMs.

Construction of Surface Sulfonic and Amino Acid–Base Pair Modified Graphene Oxide for Effectively Promoting the Selectivity of the Proton Exchange Membrane

“…For BAGO/RN-1.8, its SRs reduce to 20.1 from 29.4% of RN under 40 °C and to 28.8 from 36.6% of RN under 80 °C. The reduced SRs can be attributed to that electrostatic interaction between Nafion and BAGO combined with the steric effect of BAGO restricting the chain movement of Nafion . IEC values are shown in Figure S7.…”

“…Proton conductivities (40–90 °C, 95% RH) of (a) RN, BAGO/RN-0.6, BAGO/RN-1.2, and BAGO/RN-1.8 and (b) RN, GO/RN-1.2, and BAGO/RN-1.2.…”

“…(a) Anhydrous proton conductivities (120 °C) of RN, GO/RN-1.2, and BAGO/RN-1.2 and (b) proton conductivities (95% RH, 90 °C) of RN and BAGO/RN-1.2 during 1550 min of test.…”

“…The reduced SRs can be attributed to that electrostatic interaction between Nafion and BAGO combined with the steric effect of BAGO restricting the chain movement of Nafion. 19 IEC values are shown in Figure S7. BAGO/RN membranes exhibit slightly lower IEC values than those of RN.…”

“…Its nanoscopic and microscopic ductility can induce long-range ionic channels . In addition, its barrier effect, modulated nanophase separation and decreased the void volume of the membrane by the interaction between GO and host polymers can increase the resistance of methanol crossover. ,, Therefore, it possesses grand promise for boosting proton conduction and restraining methanol permeation of PEMs. For example, sulfonated organosilane functionalized GO (SSi-GO)/SPEEK, sulfonated imidized GO (SIGO)/sulfonated poly­(imide) (SPI), sulfonated GO (SGO)/sulfonated CS (SCS)/CS, GO/sulfonated polyvinylidene fluoride (SPVDF), PA functionalized GO (PGO)/Nafion, polyaniline decorated GO (PANI-GO)/SPEEK, and phosphorous acid and sulfanilic acid modified GO (PS-MGO)/sulfonated polyethylene grafted polystyrene (PE-PS) composite PEMs were successfully fabricated.…”