Investigating the adsorption behavior of NOx molecules on γ-Al2O3(1 0 0)-supported proximal Pt-Ba clusters using density functional theory

Abstract

The advancement of low to zero carbon fuels for internal combustion engines has made Nitrogen oxides (NOx) emissions a focal point of engine aftertreatment. Lean NOx Trap (LNT) is one of the most promising technologies for reducing NOx emissions in light-duty vehicles. The proximity of barium (Ba) to platinum (Pt) sites plays a significant role in the adsorption, reduction, and desorption of NOx inside LNT. A simultaneous loading of Pt clusters (Pt3) and barium oxide clusters ((BaO)2) on γ-Al2O3(100) was innovatively established in this study, and the effect of oxide carrier - triatomic catalyst clusters - bimolecular alkaline earth metal oxide clusters was considered comprehensively to examine the effect of Pt-Ba proximity on the NOx adsorption behavior. Interesting trends in the adsorption energy and activation of NOx molecules (including NO/NO2 and the strong greenhouse gas N2O) due to differences in the adsorption sites (from Pt sites to Pt-Ba proximity sites and finally to Ba sites) were found, and the essential reasons for such variations were elucidated by an exhaustive electronic structure analysis. The results of this study are an interesting complement to the current mechanism for storage and reduction of NOx.