(226e) DFT Estimation of Surface Energy of Different Surfaces Morphology in Heterogeneous Catalyst

Structures and property of surface are very important in different chemical, physical and biological process. In case of heterogeneous catalysis, reaction takes place at the surface of the metals clusters (Pt, Rh etc) supported mainly on metal oxides. The interaction between the reactant molecules (adsorbate) and the surface are important in the performance of the catalyst. The property of the surface depends on surface defects like steps, holes and terraces on the surface as well as its crystal lattice structures. This surface property influences the structure of the adsorbate on the surface. Surface with different defects will have different surface morphology.

A first principle density functional theoretical (DFT) calculation is generally used to find the activation energy of different surface reaction on different catalysts. The defects on the surface (lattice structure) have great impact on the activation energy. This can be simulated with ab-initio DFT calculation.

Both the surface structure and surface coverage by different reaction intermediates have effect on different activation energies. This is because different surface coverage of intermediates gives different available sites for reaction and also results in lateral repulsive surface interaction. A relation between amounts of intermediate coverage of the surface with the activation energy of reaction of a particular intermediate is important. A MC simulation will relate theoretical calculations with realistic operating conditions that involve interactions of different adsorbed molecules.

Reaction is a surface phenomenon in a heterogeneous catalyst. Basic properties of the catalyst like reaction rate depend on the nature of the surface. The adsorbate tends to form clusters on the surface of the catalyst and change the nature of the surface. There is also a presence of clusters of reaction intermediates on the surface during reaction. This cluster of adsorbate and reaction intermediates on the surface alters the energy of the surface. The inclusion of the adsorbate and reaction intermediates on the metal surface gives a new energy to the system based on the new ?many body N electron systems? of the structure of surface together with the adsorbate and reaction intermediate.

In this paper we will address surface with different morphology. We will calculate the surface energy associated with that surface and try to find a relation between the surface morphology and average activation energy of the surface.