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

Abstract

AbstractExcellent 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.