| Summary: | 碩士 === 元智大學 === 先進能源研究所 === 99 === Pt/C catalysts are widely used in PEM fuel cell. In this study, the first part was focused on the dispersion characterization for the commercial E-Tek Pt/C catalyst by H2 chemisorption, X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Experimental parameters such as Pt loading (20 and 40 wt%), H2-tritration, H2-desorption at T = 100, 200 and 300 oC prior to H2 chemisorption were included. The results showed that the dispersion of the catalysts decreased with the Pt loading. Surprisingly, carbon-supported Pt particles were easily to be sintered during H2-tritration and H2-desorption treatments, making H2 chemisorption measurement difficult. Based on the amount of H2 consumption for the reduction behavior of PtOx of the catalyst measured by cryogenic temperature programmed reduction (TPR), the dispersion obtained by H2 chemisorption was calibrated successfully, which is in agreement with that obtained by XRD and TEM.
The second part was the reduction characterization of Pt oxide for commercial Johnson Matthey Pt/C catalysts (Pt loading = 10, 20, 40, 50, 60 wt%) by X-ray photoelectron spectroscopy (XPS) and cryogenic TPR. XPS results indicate that PtsO and PtsO2 species occur on the surface of the specimens. However, the ratio between PtsO and PtsO2 was not regularly changed with the Pt loadings. The variation of the ratio measured by XPS is very close to that characterized by cryogenic TPR based on the reaction of PtsOx + xH2 → Pts + xH2O . For all of the specimens, both PtsO and PtsO2 were reduced below 0 ℃.
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