Metal oxide bulk doping incorporation

By doping a primary catalyst component with lower-valent metal cations, additional oxygen vacancies will be created which facilitate the incorporation of electrophilic oxygen species chemisorbed on the surface into the bulk where they will not oxidize adsorbed methyl radicals. Also, the promoter oxide should be basic, not be reducible, oxidizablc, or easily volatiz-ablc. It should form a mixed oxide with the main component which may be possible if the ionic radii arc similar. According to these rules, the expert system proposes as potential catalyst components combinations of substances with appropriate chemical and physico-chemical properties (Table 2). Many of these systems already have been described in the literature... 

Perovskites form the matrix for the next paperthere is ample evidence for the catalytic activity of Pt in this structure. When incorporated in p.p.m. in (La,Pb)Mn03 there were doubts about the ionic or metallic nature of the Pt. The extent to which Pt was in the surface or in the bulk was also in question. This field has been investigated by Johnson et al. who applied XPS and identified Pt and Pt species. Activities in catalysis were compared for Pt and Pt by synthesizing another perovskite, BaPtOa. Then for CO oxidation Pt turned out to be twice as active as metallic Pt. The very high catalytic activity of the Pt-doped Lao. Pbo.3 MnOa perovskite was then attributed to surface enrichment e.g. 70-fold) of Pt ". ... 

Bulk semiconductor nanostructured networks of CdS have been prepared in L and Hi phases [33,34]. The L phase was formed by a polyol amphiphile shown in Fig. 6. This LLC phase was doped with Cd2+ ions and then CdS was precipitated by diffusion of H2S into the gel. This nanocomposite was found to incorporate the amphiphile and metal in alternating layers (Fig. 6), closely resembling the structure of biominerals (e.g., mother of pearl). Similarly, Hi phases were prepared from an oligo(ethylene oxide) oleyl ether amphiphile (Fig. 7) mixed with a solution of Cd2+. Again, H2S was added to precipitate CdS and the resulting composite preserved the hexagonal symmetry (Fig. 7). 

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