Ultra-thin h-BN doped high sulfonation sulfonated poly (ether-ether-ketone) of PTFE-reinforced proton exchange membrane

Abstract The high proton conductivity of proton exchange membrane under low humidification must be maintained. In this work, an ultra-thin reinforced membrane was prepared by using hexagonal boron nitride nanosheets (h-BN), high sulfonated poly (ether-ether-ketone) (sPEEK, DS = 81.4%), and expanded polytetrafluoroethylene (ePTFE) for low-humidification proton exchange membrane fuel cell (PEMFC). A sPEEK/PTFE-reinforced membrane was prepared using reasonable designing and processing methods without requiring special treatment for ePTFE. The BN@sPEEK/ePTFE-reinforced membrane showed good proton conductivity, low hydrogen permeation current, and high cell performance. SEM confirmed the uniform h-BN dispersion in the ePTFE matrix membrane. Among the prepared samples, 0.5%-BN@sPEEK/PTFE-reinforced membrane exhibited the highest proton conductivity with 0.283 S/cm at 60 °C. Its peak power density was 567.7 mW/cm2, which was 16.6% higher than that of Nafion 212 (486.7 mW/cm2) under the same testing condition. All these results indicate that the BN@sPEEK/PTFE composite membrane prepared with ultra-high sulfonation degree sPEEK has broad application potential in low-humidity PEMFC.