Mass Transfer through the Interface between Catalyst Layer and Separator in PEMFCs under flooding/drying conditions

The stability of proton exchange membrane fuel cell (PEMFC) is significantly influenced by the structure, water content, and interfacial component transport of the cathode catalytic layer. Therefore, it is crucial to pay attention to and control these factors during the design and optimization process. However, there has been a lack of comprehensive research on the component transport and structural evolution at the interface between the cathode catalytic layer and separator under conditions of flooding/drying. Thus, the molecular dynamics model of the interface between the separator and cathode catalytic layer has been established to reflect the flooding/drying state of PEMFC by varying water content. The transport characteristics of water, hydrogen hydrate ions, and oxygen are analyzed at room temperature (303K), while also examining the structural evolution of the interface between the separator and catalytic layer. The results indicate that the diffusion coefficients of water molecules, hydronium ions, and sulfonic acid groups increase with increasing model water content due to competition between substances and dilution of high water content. However, oxygen diffusion coefficients gradually decrease due to reduced space and oxygen dissolution. Meanwhile, the radial distribution function of various substances is analyzed to verify the accuracy of the diffusion coefficient.