Structural characteristics, diffusion mechanism and mechanical behaviour of cathode catalyst layer

C Feng and Y Li and K Song and PF He, COMPUTATIONAL MATERIALS SCIENCE, 177, 109572 (2020).

DOI: 10.1016/j.commatsci.2020.109572

The cathode catalyst layer (CL) is an important part of proton exchange membrane fuel cells (PEMFCs), and its performance directly determines the durability and lifetime of PEMFCs, therefore it is necessary and significant to understand its basic properties. In this study, the structural characteristics, diffusion mechanism, and mechanical behaviour of the CL are studied by molecular dynamics. The interaction between Pt and graphene, Pt and oxygen, and sulfonic groups and hydronium ions increases when the water content rises, however, oxygen has little effect on the interaction between particles. Increasing oxygen content can improve the uniformity of self-distribution. The diffusion of oxygen occurs at the interface of different phases and in the water region, the former takes precedence. The change of diffusion mode from interphase form to solution form will cause the change of diffusion coefficient. Compared with water, oxygen has a little effect on the mechanical properties of CL. During stretching deformation, holes are formed initially in the hydrophilic region, causing the structure to be broken with large deformation, and Pt/graphene particles are always encapsulated by ionomers. In addition, the corresponding properties of anode CL, including hydrogen and water effects, has been discussed and compared with those of cathode CL. This work provides theoretical understanding and prediction of the microstructure and physical properties of CL, the results are helpful for designing and optimizing its structure.

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