Effect of TiO[sub 2] Surface Properties on Performance of Nafion-Based Composite Membranes in High Temperature and Low Relative Humidity PEM Fuel Cells

Abstract

Nafion∕10% (mass % is used in this paper) composite membranes were studied in a proton exchange membrane (PEM) fuel cell over a range of relative humidity (RH) from 26 to 50% at temperatures of 80 and . According to the scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) structural analysis, the composite membranes had a two-layer structure, one layer enriched with particles, and the other dominated by the Nafion polymer. Although the particles were mainly concentrated on one side of the composite membrane, sufficient hydration was apparently achieved for the whole membrane. Two (rutile) powders used for the preparation of the composite membranes differed in specific surface area (SSA), surface zeta potential, and particle morphology. A powder with five times higher SSA, higher zeta potential (at the low-pH limit), and distinctly different individual particle and particle aggregate morphologies resulted in a four-times increase of current density (at ) when the composite membranes were made and tested in PEM fuel cell at temperature of and relative humidity of 26%. We speculate that a greater number of protonated sites per unit mass of powder in the membrane and a higher density of the protonated sites contribute to the enhanced fuel cell performance.