Selectivity Enhanced by Shape

Zaera et al. successfully tuned the selectivity for the production of cix-olefins by isomerization [47]. They synthesized tetrahedral Pt nanoparticles with Pt(lll) facets using PVP as the surface-capping agent Then, the organic surface layer was ranoved by calcination and subsequent oxidation/reduction cycles in O2 and H2 atmospheres. When the calcination temperature was 475 K, the shape was preserved and the trans to cis formation occurred more frequently, as shown in Fig. 2.12. When the calcination temperature was 575 K, the tetrahedral shape degraded into the spherical shape and the cis to tranx formation occurred more frequently than the trans to dx.  

Conteol over the reaction pathway was also observed in electrocatalytic reactions. In electeocatalytic formic acid oxidation, there are two pathways by which formic acid is oxidized dehydration (HC00H H20-i-C0) and dehydrogenation (HC00H H2-hC02). The dehydration pathway generates surface-poisoning CO 

The electrocatalytic hydrogenation of cyclohexenone was also tested for various shapes of Pt cubes, cuboctahedra, and dendrites [49]. The dendrites produced more fully hydrogenated cyclohexanol, whereas the cubes produced more partially hydrogenated cyclohexanone. Presumably, there are more stepped sites on the surface of the dendrites, which are more advantageous for hydrogenating C=0 bonds, compared to the (100) surface. 

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