Facile Synthesis of Cellulose Whisker from Cotton Linter as Filler for Polymer Electrolyte Membrane (PEM) of Fuel Cell

Hybrid membrane is one of the most promising solutions in developing alternative membrane material for different applications. It is composed of the continuous polymer phase and the dispersed filler phase which produced synergistic effects to attain desired functionalities. The filler as additive should have well-defined structure and unique properties that enable them to serve multiple functions. Moreover, these fillers must be sourced from renewable and biodegradable materials to make it sustainable. This study examined the potential of utilizing cellulose-based renewable material in synthesizing a filler for the preparation of hybrid membrane as polymer electrolyte membrane (PEM) of fuel cell. Cellulose whiskers (CW), a class of cellulosic material that exhibits high crystallinity and elastic modulus, were effectively produced through a facile synthesis process involving sequential alkali treatment and acid hydrolysis with optimized acid concentration and reaction time. This was confirmed by the structural composition using ATR-FTIR and XRD with considerably high crystallinity, and presence of functional groups namely, sulfate and hydroxyl groups which made CW chemically reactive for further modification. Functionalization was carried out by using a green modifying agent to improve its reinforcing property. Morphological analysis revealed that crosslinked-structured CW induced a denser and more compact microstructure which was found to be correlated with enhancement of its mechanical properties. The ATR-FTIR spectrometry confirmed that carbonyl groups (C=O) were endowed onto surfaces of the material but remained highly hydrophilic. These properties also contributed to the enhanced ion exchange capacity (IEC) and proton conductivity compared to unmodified CW. Initial trials determined that CW added as filler in polymer solution showed its compatibility to form a hybrid membrane for fuel cell application.