Thermodynamics of Environment-Dependent Chemisorption on Metal Surfaces Versus Metal Oxo Cations

Reaction conditions (i.e., temperature, concentration) have significant impact on catalyst composition and structure. For metal catalysts, environmental conditions induce surface coverages, and can even induce bulk transformation of the metal (e.g., into a metal oxide). For metal oxo catalysts, environmental conditions influence ligand compositions and may promote metal agglomeration. These structural and compositional changes can have significant influence on catalytic thermodynamics, kinetics, and mechanisms. Hence, a key challenge in fundamental catalysis research is understanding how catalyst composition and structure evolve under different environmental conditions. In this presentation, we discuss our endeavors to understand the structures and compositions of metal catalysts under conditions relevant for oxidation (specifically, of NO to NO₂ and n-butane to 1-butanol) and metal oxo catalysts under conditions relevant for hydrogenation (specifically, of alkenes to alkanes). We use combinations of density functional theory (DFT) and thermodynamic and kinetic modeling to estimate the compositions and structures of these catalysts at various fluid phase temperatures and concentrations and show how variation of catalyst composition and structure influences catalytic thermodynamics, kinetics, and mechanisms. Included in this story are results from our very first presentation in CRE, given in 2007. We discuss how those results have influenced our thinking about catalytic chemistry over the last 15 years and highlight the students who have continued to evolve the work and present it in the CRE Division over the years.