Revisiting the Microkinetic Modeling of the CO Oxidation over Rh/Al2O3

Carbon monoxide (CO) results in the deaths of millions every year. Much of the transportation-related CO emissions in the U.S. are from light-duty vehicles equipped with three-way catalysts containing Pt and Rh. While spark-ignition engines are more efficient under fuel-lean operations, the current microkinetic mechanisms for CO oxidation on Rh are limited to predicting a stoichiometric CO and O2 feed. In this work, we present a thermodynamically consistent, density functional theory (DFT)-based parametrized microkinetic model that predicts CO oxidation on Rh at stoichiometric and lean conditions. We demonstrate the model’s versatility by accurately simulating experimental data at different temperatures, flow rates, and inlet compositions. We then show that the model can predict literature data collected under vastly different conditions. We utilize sensitivity analysis to determine the key reactions. Additionally, we study the surface affinity to oxygen and the lack of coke formation. This microkinetic mechanism can enable optimizing three-way catalysts to reduce CO emissions further and propose cheaper alternative catalysts.