Identification of general linear relationships between activation energies and enthalpy changes for dissociation reactions at surfaces

Towards the computational design of solid catalysts

Over the past decade the theoretical description of surface reactions has undergone a radical development. Advances in density functional theory mean it is now possible to describe catalytic reactions at surfaces with the detail and accuracy required for computational results to compare favourably with experiments. Theoretical methods can be used to describe surface chemical reactions in detail and to understand variations in catalytic activity from one catalyst to another. Here, we review the first steps towards using computational methods to design new catalysts. Examples include screening for catalysts with increased activity and catalysts with improved selectivity. We discuss how, in the future, such methods may be used to engineer the electronic structure of the active surface by changing its composition and structure.

The CO formation reaction pathway in steam methane reforming by rhodium

Three different pathways toward CO formation from adsorbed CH and O are compared by quantum-chemical density functional theory (DFT) calculations for planar and stepped Rh surfaces. The conventional pathway competes with the pathway involving a formyl (CHO) species. This holds for both types of surfaces. The barrier for carbon-oxygen bond formation for the planar surface (180 kJ/mol) is substantially higher than that for the stepped surface (90 kJ/mol). The reaction path through intermediate formyl formation competes with direct formation of CO from recombination via adsorbed C and O atoms. Calculations are used as a basis for the analysis of the overall kinetics of the methane steam reforming reaction as a function of the particle size and the metal.

Ab initio study of water interaction with a Cu surface

We have performed a first principles investigation of water interaction with a Cu surface. The calculated surface energy of a Cu(100) slab is in reasonable agreement with experimental data. The energy of water dissociation is in agreement with experiment. The results of the ab initio calculations are compared to experimental data on hydrogen partial pressure. It is concluded that Cu(OH)(ads) is formed due to a reaction between Cu and anoxic water. The energy of the Cu(100) slab with OH and H adsorbed is lower than the energy of the same slab with an adsorbed water molecule.

Mean-field study of the synergic effect of the CO–NO reaction on a heterogeneous substrate of interconnected sectors

A mean-field theory study is made of the behaviour of a kinetic model of the reduction reaction of NO by CO catalyzed by a surface with simple heterogeneity consisting of two interconnected sectors that differ in their NO dissociation activation energy. A synergistic effect is manifested in the activity, apparent activation energy, and reaction order of the system. This situation, analogous to that observed in the literature in the case of a heterogeneous catalytic particle, is used in the paper to analyze a real case of a bimetallic catalyst.