Chemisorption suppression explained

TRe signi ficance o TiOx-overlayer formation extends beyond the question of bonding between metals and titania. It suggests that the suppression of H2 and CO chemisorption in metal/ titania systems can be explained as simple site blockage due to the overlayer. Despite the appealing simplicity of this model the question is still open and evidence can be cited that points to a more complicated situation. Experiments have been performed under... 

The scope of the present paper is to emphasize that the interactions between support, metal and atmosphere are responsible for both the physical (size distribution, shape of the crystallites, wettability of the substrate by the crystallites and vice versa), the chemical and the catalytic (suppression of chemisorption, increased activity for methanation, etc.) manifestations of the supported metal catalysts. In the next section of the paper, a few experimental results concerning the behaviour of iron crystallites on alumina are presented to illustrate the role of the strong chemical interactions between the substrate and the compounds of the metal formed in the chemical atmosphere. Surface energetic considerations, similar to those already employed by the author (7,8), are then used to explain some of the observed phenomena. Subsequently, the Tauster effect is explained as a result of the migration, driven by strong interactions,... 

Chen and White (102), in an attempt to demonstrate the influence of electron transfer on metal-support interactions, showed that the addition of small amounts of K to Pt/Ti02 catalysts suppressed H2 chemisorption on low-temperature reduced catalysts. They explained this result in terms of a charge transfer from K to Pt and suggested that the loss in chemisorption capacity occurring after HTR on Ti02-supported catalysts could be... 

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