Influence of hot-pressing temperature on the performance of PEMFC and catalytic activity

The influence of hot-pressing temperature on catalytic activity and the performance of proton exchange membrane fuel cells (PEMFCs) was investigated using current-voltage (I-V) polarization, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). EIS provided detailed information on the contribution, from high to low frequencies, of internal impedance (R(s)), interfacial impedance (R(if)) and reaction impedance (R(rxn)). The ohmic resistance of the cell (R(Omega)) was estimated from the I-V diagram for comparison with the R(s) and R(if) impedances. The Rif is useful for diagnosing catalytic activity and interpreting PEMFC performance. A cell was hot-pressed at 125 degrees C (near the transition temperature of Nafion), an optimum temperature for lowest ohmic resistance and total impedance in response to a maximal catalyst-specific activity.