Extensive density functional theory calculations are performed to analyze the structure and activity of Cu and Cu Zn/Cu ZnO clusters containing up to 10 Cu/Zn atoms. The minimum-energy structures of Cu Zn and Cu ZnO clusters are found by doping minimum-energy pure Cu clusters with Zn atom(s) and ZnO molecule(s), respectively, followed by energy minimization of the resultant clusters. Odd-even alteration in properties that determine cluster stability/activity is observed with cluster size, which may be attributed to the presence/absence of unpaired electrons. The difference in behavior between Zn/ZnO doping can be interpreted in terms of charge transfer between atoms. Charge transfers from Zn to Cu in the Cu Zn clusters and from Cu and Zn atoms to O atom in Cu-ZnO clusters, which implies that the Cu atom acts as an electron acceptor in the Cu Zn clusters but not in the Cu ZnO clusters. Finally, the adsorption energies of glycerol and hydrogen on Cu Zn/Cu ZnO clusters are computed in the context of the use of Cu Zn/Cu ZnO catalysts in glycerol hydrogenolysis. Glycerol adsorption is generally found to be more energetically favorable than hydrogen adsorption. Dual-site glycerol adsorption is also observed in some of the planar clusters. Fundamental insights obtained in this study can be useful in the design of Cu Zn/Cu ZnO catalysts. K E Y W O R D S catalysis, copper-zinc clusters, DFT, glycerol adsorption, mixed oxides | INTRODUCTIONAlloys of more than one metal have been of interest to mankind since prehistoric days as they provide the means to attain desired synergistic behavior using a proper combination of constituents. With recent advances in material synthesis and nanotechnology, newer applications of such materials have emerged. For instance, in the area of catalysis, a large variety of bimetallic catalysts has been reported that often exhibit enhanced properties such as stability, selectivity to desired products, resistance to poisoning/deactivation, etc. compared to single-metal catalysts formed by their respective constituents. [1][2][3] Besides, the addition of a second, cheaper metal is also often an economical choice when dealing with expensive metals. Such catalysts are of tremendous interest in emerging areas of hydrogen production, [4,5] CO x utilization, [6] water treatment, [7] biomass conversion, [8] etc.The experimental design of bimetallic catalysts using the trial and error method is a costly and time-consuming affair, which may benefit from theoretical knowledge of metal-metal interactions and charge transfers in a bimetallic system. Although detailed quantum chemistry calculations of bulk catalysts containing thousands of atoms are far from feasible with current computational capabilities, two plausible alternatives exist.

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The thermolysis of ammonium perchlorate (AP) and AP/polystyrene propellants was investigated with carboxylates of copper as additives. The rate of burning was found to be enhanced considerably. TG and ignition delay studies demonstrated that the high-temperature decomposition of AP is enhanced enormously by these additives, whereas the low-temperature decomposition remains unaffected. It is suggested that the main species catalysing the rate of burning or AP decomposition is CuO. Analysis showed that the increase in the rate of burning is controlled by the catalysis of AP decomposition.The thermal decomposition of ammonium perchlorate (ALP) has previously been thoroughly investigated due to its deflagration characteristics. The initial thermolysis reaction of this salt is proton transfer from NI-I~ to the anion, liberating adsorbed and gaseous NH3 and .HC104 [1,2]. Subsequently, these species react by radical reactions, providing N2, H20, C12, nitrogen oxides, etc. However, the thermal decomposition involves a complex set of competitive reactions.The presence of metal oxide additives during the decomposition of AP is believed to accelerate the decomposition of ammonia [2][3][4][5][6][7]. In earlier studies, we reported [6,7] that the carbonates and freshly prepared oxides of copper and chromium are better burning rate additives than their aged oxides.

Quantum chemistry calculations have been performed to access the efficacy of Cu-based catalysts in various mechanistic steps of the glycerol hydrogenolysis reaction. Calculations are first performed for reactants in the gas phase (noncatalyzed system) and reactants in the gas phase with a 3-atom Cu cluster (catalyzed system). We demonstrate that the glycerol to ethylene glycol conversion is preferred in the noncatalyzed system but glycerol conversion to 1,2-propanediol via the 2-acetol intermediate is preferred in the catalyzed system. We next analyze the adsorption energies of the reactant and product species involved in the glycerol to 1,2-PDO reaction on an 8-atom Cu cluster and Cu cluster doped with a Zn atom or a ZnO molecule. Finally, we study the effects of Zn or ZnO doping on the activation barriers of the two steps of the glycerol to 1,2-PDO reaction.