First-Principles Research on Adsorption of NOx on Pt Cluster and BaO Cluster Supported by γ-Al
Lean NOx trap (LNT) is a great potential NOx abatement method for lean-burn gasoline engines in consideration of exhaust aftertreatment cost and installation space. NOx firstly is adsorbed on storage sites during the lean-burn period, then reduced to N2 under catalysis of the catalyst sites in the rich-burn phase. There must be a spillover of NOx species between both types of sites. For a better understanding of this spillover process of NOx species between Pt (as the catalytic center) and BaO sites (as storage components in commercial catalyst), this work focused on the vital first step of spillover, the adsorption of NOx on clean substrate surface (γ-Al2O3 (110) surface) and Ba\Pt cluster supported by the surface. Based on first principles software VASP (Vienna Ab-initio Simulation Package), the most stable adsorption structures of NO with Pt3 clusters and (BaO)3 clusters on carrier γ- Al2O3 (110) surface were confirmed and the adsorption energy of these structures were compared. Meanwhile electronic structure analysis of these adsorption systems was investigated by analyzing DOS (density of state), Bader charge, charge density difference and COHP (crystal orbital Hamilton population). From electronic structure analysis methods mentioned above, a better view of electron transfer and bond formation between gas phase NOx molecules and supported BaO or Pt cluster was obtained. This work has laid a good foundation for the further research of NOx adsorption and reduction of LNT by providing a more microscopic explanation of NOx species spillover mechanism.