Transition metals (Pt, Pd, Rh, Cr, etc.) are widely used as catalysts on γ- and η-alumina, two phases of Al2O3, but the catalytic activity of Cr on γ-alumina degrades rapidly. We report density-functional calculations that trace the origin of the effect to differences in surface reconstruction caused by different distributions of bulk cation vacancies. On η-alumina, Cr atoms remain on the surface, threefold-coordinated and reactive; on γ-alumina, they get trapped in subsurface octahedral sites and become inactive. Some metal atoms (e.g., Mn) also get trapped, but the other catalytic elements (Pt, Pd, Rh) do not. Steric constraints, size effects, or other qualitative considerations are not adequate to account for the results.
|Number of pages||4|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 1 Mar 2003|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics