Polymer electrolyte membrane fuel cells (PEMFCs) are electrochemical systems that
produce electricity from the oxidation of hydrogen (H2) gas, and are becoming increasingly
studied as an alternative energy source for many industrial and consumer applications. In this
study, the effects of total reactant flowrate, H2 concentration, and flow configuration on the
performance of a 25 cm2 NafionTM membrane-equipped PEMFC were investigated. Cell
performance was evaluated on the basis of polarization curves, power density curves, and
maximum energy efficiency at fuel flowrates ranging between 19.4 to 95.0 mL H2/min, H2
concentrations between 100 and 50 mol%, and either serpentine or open flow configurations at
the cathode. Potential losses due to activation polarization decreased with increasing total feed
flowrate in the serpentine configuration, likely due to improved reactant saturation at the
electrodes. Increasing the total reactant flow caused an increase in power density but no
appreciable change in overall energy efficiency, which was consistently between 0.625 and
0.645. Cell performance did not change significantly when the H2 flowrate and concentration
alone were varied in the presence of excess oxygen (O2), but increased when both the H2 and air
flowrates were increased. This behaviour suggests that at the low/moderate temperatures and low
current densities tested herein, cell potential and polarization behaviour are dependent primarily
on the cathode-side conditions. Overall energy efficiency was consistently greater with the
serpentine flow configuration than with the open configuration by a small (2.5 – 2.6%) but
statistically significant margin. The results of this study provide insight into the complex
interactions between operating conditions and polarization effects during PEMFC operation
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