Catalytic oxidation of NO to NO2 on pure and doped AunPt3-n (n=0–3) clusters: A DFT perspective

Abstract

A systematic density functional theory (DFT) calculations are performed on pure as well as doped Au3 trimer clusters to study the catalytic oxidation of NO to NO2 using the M06L functional combined with a def2QZVPP basis set. Adsorption energies and Bader charges of adsorbed NO and O2 on the AunPt3-n clusters have been calculated to observe the stability of the adsorbed species. Results show that the adsorption of both NO and O2 on the bimetallic clusters is stronger on the Pt site than that of Au site. Owing to the high adsorption energy of both the reactants, we further propose a reaction mechanism of NO oxidation over AunPt3-n (n = 0–3) clusters following the Langmuir-Hinshelwood (L-H) mechanism. The rate constants of NO2 production at each step of the reaction mechanism are determined using the Transition State Theory (TST). Energetic span model is also used to determine the efficient catalytic system among the four clusters. This study offers a new insight into the fundamental effect of doping Pt on Au3 and conveys an understanding for the NO oxidation mechanism at the molecular level which in turn will help in building efficient catalysts for large-scale processes.