Investigation of physical properties and cell performance of Nafion/TiO 2 nanocomposite membranes for high temperature PEM fuel cells

Abstract

Synthesis and characterization of Nafion/TiO 2 membranes for proton exchange membrane fuel cell (PEMFC) operating at high temperatures were investigated in this study. Nafion/TiO 2 nanocomposite membranes have been prepared by in-situ sol–gel and casting methods. In the sol–gel method, preformed Nafion membranes were soaked in tetrabutylortotitanate (TBT) and methanol solution. In order to compare synthesis methods, a Nafion/TiO 2 composite membrane was fabricated with 3 wt.% of TiO 2 particles by the solution casting method. The structures of membranes were investigated by Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Analysis (EDXA). Also, water uptake and proton conductivity of modified membranes were measured. Furthermore, the membranes were tested in a real PEMFC. X-Ray spectra of the composite membranes indicate the presence of TiO 2 in the modified membranes. In case of the same doping level, sol–gel method produces more uniform distribution of Ti particles in Nafion/TiO 2 composite membrane than the ones produced by casting method. Water uptake of Nafion/TiO 2 membrane with 3 wt.% of doping level was found to be 51% higher than that of the pure Nafion membrane. EIS measurements showed that the conductivity of modified membranes decreases with increasing the amount of doped TiO 2. Finally, the membrane electrode assembly (MEA) prepared from Nafion/Titania nanocomposite membrane shows the highest PEMFC performance in terms of voltage vs. current density (V–I) at high temperature (110 °C) which is the main goal of this study.