The Interface Structures And Modulation Of Catalytic H₂O₂Synthesis Of Carbon-supported Noble Metal Clusters

Graphene, as a novel material, has attracted tremendous attention indifferent research fields since its discovery in2004. Meanwhile, carbonnanotubes offer a new opportunity to diversify catalytic applications dueto its superior mechanical strength, nanosized pore, graphene-like tubewalls, high specific surface area as well as high conductivity. Therefore, itis of great significance to investigate the modifications of the interfacestructures and properties between the metal clusters and the graphene orthe carbon nanotubes. The direct synthesis of H₂O₂from H₂and O₂is anenvironmental friendly reaction, which has aroused a lot of researchinterest. However, the reaction mechanism is still unclearIn this work, we first systematically studied the interactions betweennoble metals （e.g. Au, Ag and Pt） and graphene on the basis offirst-principles density functional theory. Our calculated results indicatedthat in the case of the same metal, the enhanced role in the binding energy increased in this order: N-doping, B-doping, and vacancies. On the samegraphene, the binding energies of the three kinds of metal adatomsincreased in this order: Ag, Au, and Pt. The N-, B-doping resulted in theenhancement of the covalent bond between Au and carbon atoms andformation of the chemical bond between Au or Ag and B, respectively.The point vacancies mainly acted as the geometrically anchoring sites ofmetal adatoms as well as the electron reservoir.In addition, we further investigated the stability of bare Au_nPd_10-nand supported Au_nPd_10-n（n=1,2,3,4,5） on carbon nanotubes and theoxygen adsorption properties on them. Our study suggested that, thestructures of AuPd are greatly influenced by the carbon nanotube. Forbare Pd10with D2hsymmetry, the substituted Pd by Au are located theedge site, separated, which tends to the formation Pd core structure forthe most and second most stable structures. For AuPd clusters supportedon carbon nanotube, Au is always located on the top layer for most stablestuctures. The adsorption energy of O₂decreases with the increasing ofconcentration of Au.Finally, we investigated the H₂O₂direct synthesis on Au₃₇Pd₁medium clusters. Our results show that oxygen chemisorbed weakly onthe edge of Au（111） and Au（100） rather than the surface of Au（111）. Theenergy barrier of H₂O₂synthesis was smaller than that of H2O formationreactions on the high coordinated Pd site, which is beneficial for H₂O₂ syntheis.