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Catalyst degradation indicated

Contact angle measurements on the CL may also be useful in the characterization of catalyst layer degradation in a fuel cell. Yu et al. [19] found that the contact angle of a degraded CL became smaller compared to that of an unused catalyst layer, indicating more hydrophilic behavior accompan3dng degradation. [Pg.69]

Qi et al. [32] tested autothermal reforming of n-octane over a ruthenium catalyst, which was composed of 0.5 wt.% ruthenium stabilized by ceria and potassium on y-alumina. It showed full conversion of n-octane for 800 h. However, the selectivity moved from carbon dioxide and methane toward carbon monoxide and light hydrocarbons, which has to be regarded as an indication of catalyst degradation during long-term tests despite the fact that full conversion was achieved. After 800 h the catalyst consequently showed incomplete conversion. Tests performed on the spent catalyst revealed losses of specific surface area and of 33 wt.% of the noble metal. [Pg.334]

This has to be regarded as an indication of catalyst degradation during long-term tests performed at full conversion. After 800 h the catalyst showed incomplete... [Pg.91]

The high operation temperature and the presence of phosphoric acid in HT-PEMFC MEAs are reported to accelerate the catalyst degradation [48, 55, 58, 60]. The reported values of the fraction of remaining active surface area (SA/SAo) after cell operation are summarized in Table 16.3. The table indicates that the most influential factor in loss of the surface area is the operation temperature. The 3D KMC simulation results indicated that the fraction of the remaining Pt surface area after 15,500 h at 150 °C was 0.79, and the value decreased to 0.60 when the operation temperature increased to 190 °C despite the considerably shorter cell operation time of... [Pg.344]

It shows that without gas recycle, the first bed exit gas temperature is 910 K. This is confirmed by Fig. 12.8, which also indicates that exit gas temperatures above 900 K can cause catalyst degradation. [Pg.315]

As the data in Table XIV indicate, over platinum demethylation of a ring is slow compared to C—C bond rupture within a ring. On the other hand, it is well established [e.g., Kochloefl and Bazant (161) that if one uses a supported nickel catalyst which is known to favor stepwise alkane degradation, reaction with an alkylcycloalkane is largely confined to the alkyl group (s) which are degraded in a stepwise fashion and are finally removed entirely from the ring. [Pg.70]

From the above experimental results, it can be seen that the both PtSn catalysts have a similar particle size leading to the same physical surface area. However, the ESAs of these catalysts are significantly different, as indicated by the CV curves. The large difference between ESA values for the two catalysts could only be explained by differences in detailed nanostructure as a consequence of differences in the preparation of the respective catalyst. On the basis of the preparation process and the CV measurement results, a model has been developed for the structures of these PtSn catalysts as shown in Fig. 15.10. The PtSn-1 catalyst is believed to have a Sn core/Pt shell nanostructure while PtSn-2 is believed to have a Pt core/Sn shell structure. Both electrochemical results and fuel cell performance indicate that PtSn-1 catalyst significantly enhances ethanol electrooxidation. Our previous research found that an important difference between PtRu and PtSn catalysts is that the addition of Ru reduces the lattice parameter of Pt, while Sn dilates the lattice parameter. The reduced Pt lattice parameter resulting from Ru addition seems to be unfavorable for ethanol adsorption and degrades the DEFC performance. In this new work on PtSn catalysts with more... [Pg.321]


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