Molecular analysis of hydrogen-bond structures in polymer electrolyte membrane in polymer electrolyte fuel cells below freezing temperatures

The PEFC has been attracted to achieve carbon neutralization with using of cars and so on. Unclearness of the internal state of the polymer electrolyte membrane (PEM) below freezing temperature is one of the biggest problems toward expansion of operating temperature. Our final objective is to reveal the internal state of PEM and transport mechanism in such environment. We performed the reactive force field molecular dynamics to analyze the internal structure of PEM because under such environment chemical reaction is the key transport mechanisms. A radial distribution function (RDF) was performed to analyze the structure in PEM. Our RDF was in good agreement with other simulation results. We found the increase of water molecules in the overlapped solvation area with the decrease in temperature. The water molecules hardly move in the overlapped area, indicating that proton diffusivity decreases.