Biomass composite anion exchange membranes based on quaternized chitosan incorporated with imidazole ionic liquid-functionalized cellulose nanocrystals

Anion exchange membranes (AEMs) are the core components of fuel cells, playing a dual role in blocking anode/cathode and conducting OH- ions. In order to address the trade-off between ion conductivity and mechanical property of AEMs, imidazole ionic liquid-grafted cellulose nanocrystals (IL@CNC) was prepared and used as a novel one-dimentional nanofiller to modify quaternized chitosan (QCS) and polyvinyl alcohol (PVA) blend polymer matrix to obtain IL@CNC/QCS-PVA composite membranes. The uniform dispersion of IL@CNC and the strong interaction between nanofillers and polymer matrix significantly increased the tensile strength and toughness. Moreover, with the help of 1D shape of CNC together with the grafted imidazole groups, highly-effective ion transport channels were formed inside the membrane, and ion exchange capacity was also increased, thereby sharply improving the ionic conductivity of the composite membranes. The membrane containing 4% IL@CNC demonstrated the ionic conductivities of as high as 29.3 and 76.5 mS cm-1 at room temperature and 80 degrees C, respectively, which were 4.0 times and 3.6 times higher than those of the pure membrane under the same condition. The as-prepared composite membranes containing the biopolymer and functionalized natural nanocellulose are expected to be used as a novel type of biomass-based AEMs.Highlights Imidazole IL grafted CNC was used as a novel 1D nanofiller to modify QCS-PVA. The membrane had high ionic conductivity and mechanical properties. Providing a new way to design biomass-based AEMs with high performance.