Abstract
Nafion composite membranes, containing different amounts of mesoporous sulfated titanium oxide (TiO2-SO4) were prepared by solvent-casting and tested in proton exchange membrane fuel cells (PEMFCs), operating at very low humidification levels. The TiO2-SO4 additive was originally synthesized by a sol-gel method and characterized through x-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and ion exchange capacity (IEC). Peculiar properties of the composite membranes, such as the thermal transitions and ion exchange capacity, were investigated and here discussed. When used as an electrolyte in the fuel cell, the composite membrane guaranteed an improvement with respect to bare Nafion systems at 30% relative humidity and 110 °C, exhibiting higher power and current densities.
Highlights
Fuel cells are electrochemical devices with high-energy conversion efficiency, minimized pollutant emission and other advanced features
The major issue for this membrane is the decrease of its conductivity under desirable operating conditions, i.e., low relative humidity (RH) and temperature higher than 80 ◦ C [6,7]
Taking advantage of the properties of TiO2 -SO4, we demonstrate the applicability of the proposed composite membranes in proton exchange membrane fuel cells (PEMFCs) at high temperature and low relative humidity
Summary
Fuel cells are electrochemical devices with high-energy conversion efficiency, minimized pollutant emission and other advanced features. Among the different types of fuel cells, including alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), direct-methanol fuel cell (DMFC), molten carbonate fuel cell (MCFC) and solid oxide fuel cell (SOFC), the proton exchange membrane fuel cell (PEMFC) is attractive both for automobile and stationary applications [1,2]. The most used as a proton exchange membrane for these devices is Nafion (Du Pont), a perfluorosulfonic acid polymer [3], thanks to its high proton conductivity, suitable mechanical properties, chemical and electrochemical stability, low fuel permeability and electronic insulation [4,5]. The major issue for this membrane is the decrease of its conductivity under desirable operating conditions, i.e., low relative humidity (RH) and temperature higher than 80 ◦ C [6,7]. At low RH the water management will be simpler with respect to devices working fully humidified [8]
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