Functionalized titania nanotube composite membranes for high temperature proton exchange membrane fuel cells

Abstract

In this study, functionalized titania nanotubes (F-TiO 2-NT) were synthesized by using 3-mercaptopropyl-tri-methoxysilane (MPTMS) as a sulfonic acid functionalization agent. These F-TiO 2-NT were investigated for potential application in high temperature hydrogen polymer electrolyte membrane fuel cells (PEMFCs), specifically as an additive to the proton exchange membrane. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results confirmed that the sulfonic acid groups were successfully grafted onto the titania nanotubes (TiO 2-NT). F-TiO 2-NT showed a much higher conductivity than non-functionalized titania nanotubes. At 80 °C, the conductivity of F-TiO 2-NT was 0.08 S/cm, superior to that of 0.0011 S/cm for the non-functionalized TiO 2-NT. The F-TiO 2-NT/Nafion composite membrane shows good proton conductivity at high temperature and low humidity, where at 120 °C and 30% relative humidity, the proton conductivity of the composite membrane is 0.067 S/cm, a great improvement over 0.012 S/cm for a recast Nafion membrane. Based on the results of this study, F-TiO 2-NT has great potential for membrane applications in high temperature PEMFCs.