Tuning the Performance of Nanofiller Reinforced Phosphorylated Chitosan-Based Proton Exchange Membrane

Abstract

In this study, a one-step method was enforced for the phosphorylation of chitosan (CS) using ATMP, and later amino functionalized multiwalled carbon nanotubes (MWCNTs-NH2) were used for the fabrication of PCS/N-MWCNTs membranes. The phosphorylation of CS and later PCS/N-MWCNTs nanocomposite membranes were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). They were also evaluated for their mechanical properties, water uptake, area swelling ratio, ion-exchange capacity (IEC), and proton conductivity. Interfacial interaction among an -NH2 group of MWCNTs and -phosphonic acid as well as the -NH2 group of PCS provided extra sites for proton transfer, thus improving the proton conductivity of PCS/N-MWCNTs membranes. These results revealed that the incorporation of N-MWCNTs into PCS chains lowers PCS chain mobility and ultimately improved the thermal and mechanical properties of the composite membranes. The proton conductivity of the composite membrane with 5 wt.% of N-MWCNTs at 80 °C was 0.045 S.cm−1. Thus, PCS/N-MWCNTs nanocomposite membranes as a PEM can be used in fuel cells. With this advantage, the N-MWCNTs-filled hydrogen fuel cell outperforms compared to PCS filled membrane.