Segregation in alloy surfaces under reactive environments

I&EC 128

John R Kitchin, jkitchin@andrew.cmu.edu, Department of Chemical Engineering, Carnegie Mellon University, 5000 Forbes Ave, 2208C Doherty Hall, Pittsburgh, PA 15213
The formation of transition metal alloys typically changes the electronic structure of the constituent atoms due to changes in the lattice constant (strain effects) and heterometallic bonding (ligand effects). As a result, alloy surfaces often have chemical properties, e.g. adsorption or catalytic properties, which are unlike either of the pure metal surfaces. Understanding the chemical properties of alloy surfaces is further complicated by issues of segregation, which makes the surface composition unlike that in the bulk, and surface heterogeneity (ensemble effects). The combination of these effects can make it difficult to interpret experimental data and makes modelling efforts of alloys surfaces challenging. A significant challenge that remains is modelling alloy surfaces under reaction conditions. Using a new first-principles thermodynamics approach we have developed we find that the presence of a reactive environment can have a significant impact on the alloy surface composition and adsorption properties.