from first principles PP-I-1

PP-I-2Mechanism of H 2 O 2 Synthesis from H 2 and O 2 on Gold and Gold-PalladiumNanoclusters: DFT ApproachBeletskaya A.V., Pichugina D.A., Kuz’menko N.E.M.V. Lomonosov Moscow State University, Moscow, Russiaanbelna@gmail.comSupported bimetallic gold-palladium nanoparticles exhibit higher activity and selectivity indirect synthesis of H 2 O 2 than the catalysts containing only gold or palladium nanoclusters. Tounderstand the nature of such synergetic effect and to improve efficiency of a catalyst it isimportant to investigate the mechanism of the reaction. For this purpose modern quantumchemicalmethods are frequently used.Bare Au 2 , Au 8 , Au 20 , Au 32, Pd 8 and mixed Au 4 Pd 4 , Au 7 Pd, Au 19 Pd and Au 31 Pd have beenchosen as active nanoparticles to investigate the mechanism of H 2 O 2 synthesis. Au 8 andAu 7 Pd have planar structure, Au 20 and Au 19 Pd clusters are of tetrahedral structure, Au 32 andAu 31 Pd possess cage-like structure. Calculations have been performed in the framework ofDFT/PBE approach with relativistic all electron basis set.Au 8 and Au 4 Pd 4 clusters are potentially active in the direct synthesis of H 2 O 2 as molecularadsorption of oxygen on these clusters takes place that is necessary in selective formation ofH 2 O 2 . In case of Pd 8 dissociative adsorption of oxygen is more energetically favorable.Hydrogen adsorbs on Au 8 cluster in dissociative form. Hydrogen atom migration on goldcluster passes through several steps and deals with low energy barriers, except the last stageof H atom migration to form H 2 O 2 (81 kJ/mol). Energy barrier of the last stage decreases incase of Au 4 Pd 4 and Au 7 Pd.The modeling of the last stage of H atom migration has been performed on top, edge and facetof Au 20 and Au 19 Pd tetrahedral clusters. This process passes on Au 20 top atom with highestenergy barrier (109 kJ/mol) and on Au 20 edge atom with lowest energy barrier (3 kJ/mol).Au 19 Pd cluster is more active in this reaction as highest energy barrier of H atom migration onAu 19 Pd top atom two times lower than in case of Au 20 . Kinetics of this reaction is determinedby structural features more significant for Au 20 than for Au 19 Pd.High catalytic activity of AuPd clusters is caused by charge redistribution in bimetallicsystems.This work has been financially supported by the grant of Russian Federation PresidentМК-158.2010.3 and МК-107.2011.3. and the grant of government support of leading scientificgroup of Russian Federation НШ-6512.2010.3. Calculations have been performed using“Lomonosov” and “Chebyshev” supercomputer of M.V. Lomonosov Moscow State University.117