Performance of a polymer electrolyte membrane fuel cell (CHG 4116)

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