Synthesis and characterization of a novel poly (vinyl alcohol)-based zinc oxide (PVA-ZnO) composite proton exchange membrane for DMFC

Abstract

Electrolyte polymeric membranes were synthesized by impregnating zinc oxide (ZnO) nanoparticles (NPs) in a cross-linked PVA matrix for Direct Methanol Fuel Cell (DMFC) applications. The novel membranes consist of PVA as the support while zinc oxide nanoparticles serve as inorganic ion exchangers. The fabricated composite proton exchange membranes exhibit a wide variety of advantages which include good thermal and chemical stability. The synthesized membranes demonstrate a high percentage of water uptake (85%–105%) and a low percentage of methanol uptake (17%–21%). Other important properties such as transport number (0.88) and ion exchange capacity (0.78 meq.g−1) were also determined, and they were found comparable to Nafion®117. Ionic conductivity (3.9 mS/cm) of the composite membranes was determined and found comparable to other PVA based composite membranes reported in literature. Characterization of the membranes was carried out using Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDX) and Thermogravimetric analysis (TGA). These characterizations revealed the structural interaction between the support and the ion exchanger, crystalline nature, surface morphology, elemental analysis and the thermal stability (upto 280 °C) of the membranes, respectively. The mechanical characterization of the membranes was also carried out on a Universal Testing Machine (UTM), revealing satisfactory mechanical stability. The results demonstrate the possibility of synthesis of a low-cost proton exchange membrane for DMFC applications.