Reinforced proton conductivity through imidazole-loaded cellulose nanofibers for proton exchange membranes

Abstract

The strategy of implanting some functional groups with proton-conducting into proton exchange membranes (PEMs) provide more proton transfer sites is beneficial to enhance proton conductivity. In this work, imidazole is loaded onto solution blown cellulose nanofibers (Cell/Im NFs) under the function of acid-base pair. Then, Cell/Im NFs are introduced into Sulfonated Poly (ether sulfone) (SPES) polymer matrix and act as quasi-one dimensional proton-conducting pathways for nanofiber hybrid proton PEMs. The acid-base pair formed by electrostatic interaction can promote the protonation/deprotonation and the subsequent proton-hopping. The structure of Cell/Im NFs and properties of the hybrid PEMs are examined. The results show that the introduction of Cell/Im NFs can significantly improve proton conductivity, and the PEMs with Cell/Im-30 NFs can reach the best value of 0.123 S cm−1 at 80 °C and 100% RH. Besides, the structure of three-dimensional hydrophilic network of Cell/Im NFs exhibit significant effect on the performance of water uptake, methanol permeability and thermal stability of the hybrid PEMs. The prepared hybrid PEMs exhibit high potential for developing PEMs in direct methanol fuel cells (DMFCs).