(645a) On the Reaction Mechanism of NO Reduction By H2 on Platinum Catalysts

Environmental concerns with pollutant gases have become a global topic and attracted significant attention. One particular type of pollutant gas generated from fossil fuels combustion is nitric oxide (NO), which has many deleterious effects on both the environment and human health. Though NO removal technologies, e.g. three-way catalysts (TWC) and selective catalytic reduction (SCR), have been developed and improved significantly over the last several decades, a fundamental understanding of the NO reduction reaction mechanism is still lacking, stimulating researchers to study the reaction network on various transition metal catalysts. Pt, a major component in three-way catalysts, has been shown to have high catalytic activity in NO reduction reaction. In this study, we use a combined periodic, self-consistent density functional theory (DFT-GGA), reaction kinetics experiments and micro-kinetic modeling to analyze the mechanism of NO reduction by H₂ on Pt catalysts. In particular, we investigate the role of H in activating the N-O bond by comparing the energetics of direct and H-assisted pathways, the NO coverage effects on surface reaction chemistry, and the structure sensitivity of this reaction by making comparisons between multiple Pt facets. Parameters in micro-kinetic modeling are optimized to describe experimental kinetic data, and to elucidate the nature of possible active sites for NO reduction by H₂ on Pt.