After single-cell testing, a potentiostat (Autolab, Eco Chemie)
was used to further characterize the MEAs by electrochemical
impedance spectroscopy (EIS) and cyclic voltammetry (CV).
Cell temperature was maintained at 60 C during all the
electrochemical measurements. Cell EIS spectra were recorded
in a galvanostatic mode at a load current of 1.0 A while
anode EIS was measured in a potentiostatic mode at 0.4 V. The
EIS analyses were conducted in a frequency range of
0.1e1000 Hz. To record the cell EIS spectra, a 1.0 M methanol
(1 ml min1) solution was fed to the anode while dry air was
supplied to the cathode (100 sccm). Dry air was replaced by
humidified hydrogen (100 sccm) at the cathode side during
anode EIS measurement. CV scans were utilized to compare
the electrochemically active surface areas (ECSAs) of the
cathodes. The details of the procedure for the CV measurements
are given elsewhere [22]. The values of cathode ECSAs
were calculated in a potential range of 0.05e0.4 V corresponding
to the hydrogen desorption region. Proton conductivities
of Nafion 115 membranes were measured by fixing