Theoretical Investigation of Catalytic Oxidation of Benzylalcohol by Au, Cu and Au-Cu nanoclusters

Abstract

Gold nanoclusters have been found to catalyze chemically significant reactions like oxidation of greenhouse gases and selective oxidation of alcohols. Further incorporation of Cu atoms in Au alloys enhances their catalytic activity and selectivity. Experimental results have demonstrated different rates of benzyl alcohol conversion to benzaldehyde relative to different ratios of Au and Cu in the catalyst nanoparticle. The rates of conversion demonstrates higher catalytic activity of pure Au cluster compared to pure Cu cluster. In this work, the catalytic roles of Au and Cu in the aerobic oxidation of benzyl alcohol to benzaldehyde were analyzed using density functional theory (DFT) methods. Au-rich and Cu-rich clusters were considered as catalyst, namely Au13, Au12Cu and Cu13, Cu12 Au clusters respectively. The mechanism of the minimum energy path focuses on the oxidation of two molecules of benzyl alcohol by a single molecule of O2 to produce two molecules of benzaldehyde and H2O each. The calculations reveal that the reaction rate is predominantly governed by the adsorption of reactants and the desorption of products, consistent with experimental observations. In Cu-rich clusters, the adsorption of O2 is more favorable due to effective charge transfer between the cluster and O2 resulting in high adsorption energy. Additionally, the desorption of products is significantly endothermic on Cu rich catalysts than on Au-rich catalysts.