The ionomer content in the catalyst layer is a crucial design factor that affects the performance of polymer electrolyte membrane fuel cells (PEMFCs). However, the optimal ionomer content can vary based on the surrounding humidity levels. This study systematically evaluated the influence of the ionomer-to-carbon (I/C) ratio (0.00, 0.55, and 0.91) on PEMFC performance under fully humidified (RH 100%) and low-humidity (RH 25%) conditions. Membrane-electrode assemblies (MEAs) were fabricated using a spray coating technique, and their electrochemical properties were analyzed through polarization curves and electrochemical impedance spectroscopy (EIS). Under RH 100%, the MEA with an I/C ratio of 0.55 achieved the highest peak power density of 519.8 mW/cm², indicating a successful balance between proton conductivity and gas transport. Conversely, under RH 25%, the best performance of 203.9 mW/cm² was observed at an I/C ratio of 0.91. This shift is attributed to improved water retention at higher ionomer content, which reduced membrane dehydration and lowered both ohmic and Faradaic resistances. These findings highlight the dual role of the ionomer in facilitating proton transport and managing water balance, emphasizing the necessity of optimizing the I/C ratio according to operating conditions for stable and high-performing PEMFC operation.

In this study, we developed and evaluated a simple device for removing ionic impurities that affect the performance of a polymer electrolyte membrane fuel cell (PEMFC) in a marine environment. In such environments, PEMFCs may experience performance degradation due to the presence of Na+ and Cl- in the air. To address this issue, the decontamination device was designed with both heating and cooling components. This device was positioned between a humidifier containing NaCl solution and a humidifier containing deionized water, both connected on the cathode side. The decontamination device effectively removed impurities (Na+ and Cl-) during experiments. As a result, the electrochemical performance of the fuel cell with the decontamination device improved compared to that of the fuel cell without it. Notably, the activation resistance and electrochemical surface area were significantly enhanced, and the ohmic resistance also improved when compared to the fuel cell without the decontamination device.