Determination of oxygen mass transport resistance in proton exchange membrane fuel cells with an open flow field architecture

In this work, we demonstrate the applicability and validity of our novel method in determining the oxygen mass transport resistance of proton exchange membrane fuel cells (PEMFCs) using a commercially relevant open flow field design. The method is based on the measurements of the limiting current when a cathode is fed by highly diluted O-2 mixtures. Mass transport resistance originating from Knudsen diffusion and dissolution through liquid and ionomer films in a cathode catalyst layer (R-K+(film)) can be separated from molecular diffusion in the gas phase (R-m, (N2)) by varying the diluent molecular weight. The performance and mass transport properties of the single cell open field (SCOF) design were evaluated and compared with a serpentine land/channel architecture under subsaturated and oversaturated conditions. Analysis of the SCOF under subsaturated conditions showed that R-K+(film) and R-m(, )N2 were 74.85 and 35.65 s m(-1), respectively. These values were found to be lower than those for the serpentine cell and explained the superior performance of the SCOF. The SCOF demonstrated better performance under oversaturated conditions as well due to the low R-m(, )N2, which compensated for the high RK+film. The results indicated that the open flow field architecture ensured good transport in the gas phase, uniform humidification of the catalyst layer and efficient oxygen diffusion through the ionomer. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study demonstrates the applicability and validity of a novel method for determining oxygen mass transport resistance in proton exchange membrane fuel cells. The method is based on measuring the limiting current when a cathode is fed with highly diluted O-2 mixtures, allowing for separation of different sources of mass transport resistance. Evaluation and comparison of different cell designs under varied conditions reveal the importance of gas phase transport and efficient oxygen diffusion through the ionomer.