Investigation of the Effect of Operating Conditions on the Polarization Process of Proton Exchange Membrane Fuel Cells Based on the Distribution of Relaxation Times Using Orthogonal Test Method

Proton exchange membrane fuel cell (PEMFC) performance is significantly influenced by different operating conditions. In this study, the effects of temperature, cathode back pressure, cathode relative humidity (RH), and air stoichiometry on the mass and charge transfer processes within the electrochemical reaction are investigated using orthogonal test methodology. Polarization curves and electrochemical impedance spectra (EIS) are analyzed, and the distribution of relaxation times (DRT) method is employed to separate and quantify different polarization processes. A 3rd-order RC equivalent circuit model is constructed, and the DRT-based method identifies three peaks within the frequency spectrum to represent the cathodic mass transfer process, cathodic catalytic layer oxygen reduction reaction (ORR) process and anodic process, respectively. The influence weight of each operating factor is investigated using the range analysis method. The experimental results demonstrate that air stoichiometry has the dominant influence on mass transfer resistance throughout the entire current density range, with the most significant effect found at low and high current densities. The impact of temperature on activation resistance dominates at low and medium current densities, especially at low current densities. In contrast, for high current densities (> 1 A cm−2), the influence of air stoichiometry on charge transfer processes outweighs that of temperature.