Sulfonated graphitic carbon nitride nanosheets as proton conductor for constructing long-range ionic channels proton exchange membrane

Abstract

Incorporating hydrophilic nanofiller into membrane has been proven to be a simple and effective strategy to enhance the performance of proton exchange membranes (PEMs). In this work, sulfonic acid functionalized graphitic carbon nitride (SCN) nanosheets were explored as nanofillers to prepare composite PEM for the first time. In this composite system, acid-base pair effect between SCN and sulfonated poly(aryl ether)s facilitated the dissociation of sulfonate groups and the formation of hydrogen-bonding networks. Meanwhile, the desirable interfacial interaction acting as a “zipper” motivated the formation of nano-phase separation morphology and built long-range ionic channels at the interface significantly. Consequently, the obtained nanocomposite membranes exhibited a significant improvement in proton conductivity. At the SCN content of 0.5 wt%, the SPFAE/SCN-0.5 membrane showed a proton conductivity of 204 mS cm-1 at 90 °C, which was 26% higher than the original membrane. The interfacial interaction was also capable of reinforcing the mechanical property and dimensional stability. Due to the overall performance improvement, the SPFAE/SCN-0.5 membrane displayed an excellent H2/O2 fuel cell performance of 717 mW cm-2 at 100 %RH and 80 °C, which was comparable to the Nafion 112 membrane.