Abstract
A composite membrane based on a Nafion polymer matrix incorporating a non-stoichiometric calcium titanium oxide (CaTiO3−δ) additive was synthesized and characterized by means of thermal analysis, dynamic mechanical analysis, and broadband dielectric spectroscopy at different filler contents; namely two concentrations of 5 and 10 wt.% of the CaTiO3−δ additive, with respect to the dry Nafion content, were considered. The membrane with the lower amount of additive displayed the highest water affinity and the highest conductivity, indicating that a too-high dose of additive can be detrimental for these particular properties. The mechanical properties of the composite membranes are similar to those of the plain Nafion membrane and are even slightly improved by the filler addition. These findings indicate that perovskite oxides can be useful as a water-retention and reinforcing additive in low-humidity proton-exchange membranes.
Highlights
Nafion is the archetypical membrane for use in the proton exchange membrane fuel cell (PEMFC), a clean technology suitable for both transport and stationary applications [1,2]
In PEMFCs operating at temperatures above 80 ◦ C, Nafion experiences a severe decrease in proton conductivity due to water evaporation, which is reflected in an increase of the electrolyte’s ohmic resistance [4]
The scope of the present study is to investigate the impact of the additive on thermomechanical and proton-conduction properties of membranes by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and broadband dielectric spectroscopy (BDS) studies, in order to evaluate the interplay of the transition/relaxation phenomena in Nafion membranes at high temperatures and under humidified conditions
Summary
Nafion is the archetypical membrane for use in the proton exchange membrane fuel cell (PEMFC), a clean technology suitable for both transport and stationary applications [1,2]. To be more efficient electrical power generators, fuel cells should operate at low relative humidity (RH) conditions and at temperatures higher than 80 ◦ C. At these conditions, the kinetics of the electrode reactions, the tolerance to fuel contaminants, such as carbon monoxide, and the ions’ transport properties are all improved. One strategy to develop PMFC electrolytes suitable for high-temperature operation is to modify the polymer matrix with inorganic additives that are able to improve the water retention capacity of Nafion membranes. These additives, which can be metal oxide nanoparticles, such as SiO2 , TiO2 , and
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