Partial Palladium Oxidation over Various Oxide Supports for a Higher Reactivity of PdO with Respect to CH₄

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), and (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 the 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 ΔU₁ or surface energy γ) and less active PdO(100) at the oxide supports (γ-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.