H₂ INTERACTION WITH BIMETALLIC DIMERS SUPPORTED ON THE MgO(100) SURFACE: A DFT CLUSTER MODEL STUDY

Abstract

The interaction between the H 2 molecule and the PdAg, PdAu, PtAg and PtAu bimetallic dimers deposited on the MgO(100) surface is investigated using density functional theory (DFT). The bimetallic dimers, whose molecular axes are considered to be perpendicular to the support surface, are adsorbed on top of an oxygen atom. Within this adsorption mode, the dimers prefer the orientation in which their Pd or Pt end is closer to the oxygen atom. The Ag and Au ends of the MgO-supported dimers capture the H 2 molecule with small exoenergetic e®ects. The spontaneous dissociation of H 2 on these ends does not occur. Thus, the MgO support decreases the ability of the dimers to adsorb and dissociate the H 2 molecule. From a catalytic viewpoint, it means that the activity of small bimetallic clusters toward the dissociative adsorption of H 2 is reduced when they are arranged on MgO. On the other hand, the results of our calculations show that the presence of the MgO support strengthens the binding of H atoms inside the PdAu, PtAg and PtAu dimers.

Bimetallic dimers adsorbed on a defect-free MgO(001) surface: bonding, structure and reactivity

“…The knowledge gained from this kind of studies could allow us to optimize the chemical reactivity of clusters by the adjustment of the chemical composition. [21][22][23][24] For example, Matczak investigated H 2 interaction with MgO(001) supported PdAg, PdAu, PtAg and PtAu bimetallic dimers and showed that MgO support decreases the ability of the dimers to adsorb and dissociate hydrogen molecules. 21 Florez et al investigated Cu n M (M = Ni, Pd, Pt; n = 1 to 4) bimetallic nanoparticles adsorbed on the F s center of MgO(001) and showed that chemical reactivity depends on the nanoparticle arrangement on the surface as well as on the type of binding atom (Cu or M).…”

“…[21][22][23][24] For example, Matczak investigated H 2 interaction with MgO(001) supported PdAg, PdAu, PtAg and PtAu bimetallic dimers and showed that MgO support decreases the ability of the dimers to adsorb and dissociate hydrogen molecules. 21 Florez et al investigated Cu n M (M = Ni, Pd, Pt; n = 1 to 4) bimetallic nanoparticles adsorbed on the F s center of MgO(001) and showed that chemical reactivity depends on the nanoparticle arrangement on the surface as well as on the type of binding atom (Cu or M). 22 Obviously, catalysis via highly undercoordinated metal atoms becomes a reality, but very little is known about the electronic structure parameters that govern their reactivity.…”