Total-OSC

From these results, we may conclude that the higher the OSC of the catalyst, the higher its activity for CO oxidation. However, it is likely that a limited number of oxygen species stored on the catalyst (those just in the vicinity of metal particles) may intervene in the catalytic process. More than the total OSC, the local concentration of sites for O2 adsorption would be a determining factor in CO oxidation. A close correlation between OSC and catalytic activity may however be found since a high concentration in anionic vacancy is a prerequisite for a high OSC value of sample. 

Fig. 24. Ratio of dynamic-to-total-OSC measured over Ce02 and NM/Ce()2 (surface area 10 m2 g (Yao and...

Both of these vacancies were believed to provide a practical way to increase the OSC of Ce02. This is true if the oxygen anion mobility is considered. Solid Ce02-based electrolytes show indeed an increased ionic mobility when doped with low-valent cations (Tuller and Nowick 1975). However, the doping may lead to a decrease of the total-OSC. 

As we will see, the differences in OSC are not solely influenced by thermodynamic factors. Depending on the temperature at which the OSC is measured and also on the nature of the reducing agent (H2,C0), other surface-related processes may have a significant influence on the measured OSC values. Kinetic factors and, in connection with them, the surface structure of the oxides have a relevant role. In general, the interplay between surface and bulk structure determines the observed total OSC values. As with the OSC differences between ceria and ceria-zirconia metal-loaded catalysts, a more in-depth analysis is required in order to fully understand the redox response of thermally aged oxides. 

Ultimate, or total, OSC data measured after reduction in Hg at increasing temperatures, gathered in Table 2.1 and also plotted in Fig. 2.5, allow us to make comments on the influence of kinetic factors. If it is assumed that the ultimate OSC values determined in the Rh-loaded systems represent the thermodynamic limit of reducibility, it is clear that, as suggested in Wang et this thermodynamic reducibility of the SR-MO oxide is higher than that of the SR-SO one over the whole temperature range, even at 1173 K, a temperature at which a significant difference in OSC between the two oxides is still... 

The total Hamiltonian is the sum of the two terms H = H + //osc- The way in which the rate constant is obtained from this Hamiltonian depends on whether the reaction is adiabatic or nonadiabatic, concepts that are explained in Fig. 2.2, which shows a simplified, one-dimensional potential energy surface for the reaction. In the absence of an electronic interaction between the reactant and the metal (i.e., all Vk = 0), there are two parabolic surfaces one for the initial state labeled A, and one for the final state B. In the presence of an electronic interaction, the two surfaces split at their intersection point. When a thermal fluctuation takes the system to the intersection, electron transfer can occur in this case, the system follows the path... 

Further, the total excess charge Osc in a depletion layer may be given approximately by the product of the impurity concentration N and the layer thickness dx in Eqn. 5-76 ... 

Oxygen storage capacity (OSC) was measured at 400°C under atmospheric pressure. A 20 mg sample was continuously purged with helium (30 cm. min ). Successive or alternate pulses (0.265 cm ) of O2 (Air Liquide, < 5 ppm total impurities) and CO (Air Liquide, N20) were injected every minutes in order to simulate lean and rich operating conditions as those encountered in an Otto engine coupled with a three-way catalytic converter. The Oxygen Storage Capacity (OSC) was calculated from the CO consumption after stabilization of the sample in alternate pulses condition. 

Using the QA/QC Objective As the QA/QC Objective reflects the importance of and the intended use of the data, it also can be used to assist the OSC in the determination of the sampling methodology and the total number of field and control samples. In addition, it is also useful in the determination of the analytical methodology and the data validation criteria. 

Nevertheless, as will be shown in subsequent sections, there is a clear evidence for a strong relationship between the total/dynamic-OSC and the catalyst efficiency of the TWCs. 

The simple multiscale approach can be seen as a subset of the optimal scale combination (OSC) method. In OSC the total number of possible scale combinations is generated. In the simple multiscale approach, scales were increased in a systematic fashion 0, 0 1, 0 1 2, 0 1 2 3, ... In OSC all possible combinations of the J + 1 scales are generated and tested. The combination that gives rise to a regression or classification model with the lowest number of coefficients and the lowest prediction error will be selected. Assume i is the number of scales to be selected from a total of K scales. There... 

An interesting variant on the deltahedron of F ure 22.1 are the capped structures of 22.26. The capping group simj y utilizes the existing outward pointing orbitals presented by the face and no new orbital requhements are made on the deltahedron. Such R-beavy atom eies are then stable for a total of n skeletal electrons. So Osc(CO)i8 (22.26) 1ms a total of six skeletal pairs and six metal atoms and exhibits die capped structure but Co4(CO)]5 with seven skeletal pairs and six metal atoms exhibits the chso octahedral structure. 

The numerical results in Table 3 and Fig- 26 call for some discussion. First, one sees that the contribution of the oscillatory structural force, /os to the total surface free energy, /, is the greatest one cf. Eq. (227). Moreover, the magnitude of /osc (the depth of the first minimum in Fig. 26) increases with the decrease of the electrolyte concentration because of the increase of the micelle effective volume fraction cp. As a result, the contact angle, 6, increases with the decrease of electrolyte concentration. This tendency is exactly the opposite of that in the absence of micelles, when oscillatory structural forces are missing. 

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