Reaction mechanism of the direct gas phase synthesis of H2O2 catalyzed by Au3.

The gas phase reaction of molecular oxygen and hydrogen catalyzed by a Au₃ cluster to yield H₂O₂ was investigated theoretically using second order Z-averaged perturbation theory, with the final energies obtained with the fully size extensive completely renormalized CR-CC(2,3) coupled cluster theory. The proposed reaction mechanism is initiated by adsorption and activation of O₂ on the Au₃ cluster. Molecular hydrogen then binds to the Au₃O₂ global minimum without an energy barrier. The reaction between the activated oxygen and hydrogen molecules proceeds through formation of hydroperoxide (HO₂) and a hydrogen atom, which subsequently react to form the product hydrogen peroxide. All reactants, intermediates, and product remain bound to the gold cluster throughout the course of the reaction. The steps in the proposed reaction mechanism have low activation energy barriers below 15 kcal/mol. The overall reaction is highly exothermic by ∼30 kcal/mol. [ABSTRACT FROM AUTHOR]