Hydrophilic microporous layer coatings for polymer electrolyte membrane fuel cells operating without anode humidification

In this study, a hydrophilic microporous layer (MPL) coating was applied to a commercial hydrophobic bi-layer gas diffusion layer (GDL). We investigated the effect of the hydrophilic MPL coating on membrane hydration and liquid water distribution within the GDLs during fuel cell operation without anode humidification, using fuel cell performance monitoring and simultaneous synchrotron X-ray visualization. The application of the hydrophilic coating was found to enhance performance of the fuel cell. Specifically, the application of the hydrophilic MPL coating led to an increase in cell potential of up to 14% (0.07 V at 1.5 A/cm2) and a decrease in fuel cell membrane resistance. The decrease in membrane resistance was attributed to improved membrane hydration. This improvement in membrane hydration was caused by the increase in liquid water retention at the catalyst layer-MPL interfaces. At high current densities, the application of the hydrophilic MPL coating led to increased liquid water accumulation within the cathode GDL, which subsequently led to increased oxygen transport resistance. Our study demonstrates that the wettability of the GDL can be tailored to enhance fuel cell performance for a desired range of operating conditions by balancing membrane hydration and oxygen transport.