▎ 摘　　要

It is a challenge to simultaneously improve proton conductivity, methanol resistance and physicochemical stability of polymer electrolyte membranes (PEMs) used in direct methanol fuel cell (DMFC). In response to this situation, the crosslinked nanocomposite membranes are prepared by introducing polyorganosilicon with various functional groups and sulfonic groups functionalized graphene oxide (SFGO) to the sulfonated poly (ether ether ketone ketone) in this paper. Based on our knowledge, no such PEM materials have been designed and prepared by this method. Scanning electron microcopy images demonstrate that there are good compatibility and connectivity between the matrix and fillers. The combination of polyorganosilicon and SFGO significantly improves the comprehensive performance of membrane, including mechanical property, dimensional stability, proton conductivity, methanol resistance, selectivity, oxidative and hydrolytic stabilities, cell performance, etc. Especially, the nanocomposite membrane with 3 wt% SFGO shows the highest conductivity (0.074 S cm(-1) at 25 degrees C) and lowest methanol diffusion coefficient (3.56 x 10(-7) cm(2) S-1), which result in the optimal selectivity (2.08 x 10(5) Ss cm(-3)). In addition, the maximum power density (73.76 mW cm(-2)) of the membrane with 3wt% SFGO is higher than that of commercial Nafion (R) 117 (61.59 mW cm(-2)) under identical experimental conditions. These results indicate that the crosslinked nanocomposite membranes will be new alternative to substitute the expensive Nafion (R) 117 for DMFC application. (C) 2021 Elsevier Ltd. All rights reserved.