Speaker
Description
Polymer electrolyte fuel cells (PEFCs) consist of a gas diffusion layer (GDL) and an electrode on each side, and a polymer electrolyte membrane (MEA) between the electrodes. The main components of the MEA are catalysts, electrolyte membranes and electrodes. In this study, the local atomic structures of catalytic nanoparticles in MEA were investigated by high-energy X-ray diffraction and reverse Monte Carlo (RMC) modeling. The purpose of this study is to show guidelines for improving the performance of the PEFCs that contribute to industry by clarifying the differences in each catalyst structure and linking them with catalyst performance such as catalytic activity and catalyst durability.
In this conference, we report the structural work on the platinum-cobalt alloy nanoparticles-supported carbon catalyst TEC36F52 (manufactured by TANAKA KIKINZOKU KOGYO K.K.). Although this sample is a commercial product, it is important to investigate its structure because it can be used as a standard sample for evaluating various catalyst samples in the future.
RMC modeling based on the structure factor S(Q) obtained from high-energy X-ray diffraction is suitable to determine the 3-dimensional (3D) atomic structures of nanoparticles. High-energy X-ray diffraction measurements were performed using a two-axis diffractometer at the beamline BL04B2 in SPring-8; the energy was used 61.4 keV corresponding to 0.202 Å in wavelength. For the PtCo nanoparticle studied here, the initial configuration for the RMC modeling is a spherical shape with 2315 particles (Pt: 1744, Co: 571) and about 4 nm in diameter based on the fcc bulk crystal structure. RMC fittings for the experimental S(Q) profiles were performed to obtain the 3D structural models using RMC_POT software. The obtained structural model shows that the average interatomic distance is larger on the surface than in the interior, and the distribution of Co atoms is also altered. These structural features might be involved in the differences in catalytic activity.
This research approach is expected to accelerate the creation of new catalysts for fuel cells by providing local atomic-scale structural information. It is also important to create the database of atomic arrangement structure data that is the basis of material design and material research.
In this conference, the data recorded from the other commercial catalyst samples and the actual catalyst samples which is used in the fuel cell vehicle (FCV) will also be presented.
This work was performed under the NEDO FC-Platform project.
