| 초록 |
Nafion/clay nanocomposite membranes were prepared to reduce methanol crossover through ionomer membrane. As nano-dispersed clay particles caused a tortuous path for methanol molecules, Nafion/clay composite membrane (ca. 30 ㎛) containing 5 wt% clay filler displayed significantly lower methanol permeability, around 1.2×10-8mol/sec cm2 than that of commercial Nafion 117 membranes, ∼1×10-6 mol/sec cm2. The exfoliation of clay sheets in Nafion were characterized by X-ray diffraction and TEM images. Membrane-electrode assembly(MEA) were fabricated by spray-brushing platinum black (E-Tek Inc.) catalysts on the composite membrane, and mounted into a unit cell (3×3 cm2) connected to a load (Scribner 890B). Polarization curves were monitored at cell temperature of 70 ℃ while 2 M Methanol fuel and high purity O2 oxidant were fed to the cell. The current density reached 200 mA/cm2 at 0.5 V for Nafion 117, but it was increased upto 250 mA/cm2 for Nafion/clay composite membrane.
|
