A Comparative DFT Study on the Catalytic Oxidation of Nitric Oxide by Pd2 and PdM (M = Cu, Rh, Ag, Au, Pt)

Abstract

A detailed mechanistic investigation for the catalytic oxidation of NO over monometallic palladium dimer and its bimetallic counterparts, PdM (M = Cu, Rh, Ag, Au, Pt) has been performed using DFT. Nitric oxide is a major environmental problem, inclusive of acid rain and photochemical smog formation which is released mainly in automobile exhausts. Thus, removal of poisonous NO is a major challenge and understanding its oxidation at molecular level is of great importance in designing suitable catalysts. Bimetallic nanoparticles are more promising as catalyst due to synergetic effect. A full catalytic cycle has been studied producing two NO2 molecules from two molecules of NO and one O2 molecule. Both the pristine and bimetallic systems catalyse the reaction according to Eley–Rideal mechanism. The bimetallic PdCu system is found to be the most dominant catalytic system with the more active Pd-site (i.e. O2 activated by Pd-site). The present study enlightens the understanding for higher catalytic activity of bimetallic nanoparticle. DFT studies for the catalytic oxidation of NO on pure and bimetallic palladium clusters: Pd2, PdAu, PdAg, PdRh, PdCu, and PdPt. Removal of poisonous NO is a major challenge and understanding its oxidation at molecular level is of great importance in designing suitable catalysts. A full catalytic cycle has been studied producing two NO2 molecules from two NO molecules in presence of air. Energetic calculation reveals that PdCu is the predominant catalytic system with more active Pd-site.