Аннотация:A series of PdO slabs deposited via low-index planes (100), (010), (001), and (101) on γ-alumina, titania, and zirconia was modeled. Relative stabilities and surface energies of the PdO planes are divided into two groups of (100), on the one hand, and (010), (001), (101), on the other hand. The calculated barriers of CH4 dissociation increase with the stability or decreases versus surface energies of joined system being the lowest for 4-layer PdO(010) without support and over monoclinic ZrO2. The authors outline that CH4 oxidation upon a partial transformation of Pd to PdO allows growing of more active PdO planes (in the terms of activation barrier) over Pd instead of the most stable (in the terms of stabilization energy U1 or surface energy ) and less active PdO(100) at the oxide supports (-Al2O3, ZrO2, TiO2). The role of the contact Pd/support layer in PdO formation is discussed. Computed barriers of CH4 dissociation related to separate PdO planes over the oxides are compared with oxidation barriers calculated or measured in other works.
