Rachel B. Getman, Department of Chemical and Biomolecular Engineering, University of Notre Dame, 182 Fitzpatrick Hall, Notre Dame, IN 46556 and William Schneider, Chemical and Biomolecular Engineering, University of Notre Dame, 182 Fitzpatrick, Notre Dame, IN 46556.
One key challenge facing chemical engineers is being able to control the rates of chemical reactions, and therefore much research has focused on understanding catalysis. Heterogeneous catalysis is a popular type and has been implemented into many common processes such as fuel cells, ammonia synthesis, and emissions control. NO oxidation to NO2 is an example of a heterogeneously catalyzed reaction for the remediation of NOx from emissions. In this work we use Density Functional Theory (DFT) to examine the thermodynamics and kinetics of NO oxidation catalysis over Pt, the most common catalyst for the reaction. The enthalpy of NO oxidation is quite small, -60 kJ/mol, and therefore, NO2 formation is best promoted at high pressures, conditions which induce high concentrations of O on the catalyst surface. We show that the surface O concentrations generated under an NO oxidation atmosphere have strong effects on both the thermodynamics and kinetics of different steps in the overall reaction. The results provide insights toward formulating an NO oxidation mechanism and can likely be used to describe other transition metal-catalyzed oxidations as well.