Chemical Reactivity of Pd−Au Bimetallic Nanoclusters Grown via Amorphous Solid Water as Buffer Layer

Abstract

Bimetallic Pd-Au nanoclusters were prepared on SiO 2 /Si(100) via amorphous solid water (ASW) as buffer layer. Selective growth pathways have led to segregated palladium and gold clusters or alloy bimetallic crystallites. Morphology and chemical composition were determined by AFM, SEM, and HR-TEM coupled to EDX analysis. Correlation between clusters morphology and composition to their chemical reactivity is reported for the first time. Temperature programmed reaction studies revealed that conversion of acetylene to ethylene and trimerization to benzene are significantly enhanced over crystalline alloy Pd-Au clusters when compared to clean Pd. A remarkable selectivity toward ethylene formation over benzene is unique to the alloy bimetallic clusters grown via ASW buffer layer on silica, presumably due to suppression of the trimerization pathway. The intrinsic, modified electronic properties of the bimetallic alloy clusters are believed to drive their enhanced chemical reactivity when compared with the pure Pd clusters.

Investigation of the structures and chemical ordering of small Pd–Au clusters as a function of composition and potential parameterisation

“…For larger w a (0.6-1.0), inc-Ih-Mackay is a competitive structure, especially in the Au-rich range from (9,29) to (5,33). Other structures that might be competitive for Pd-Au clusters are pIh 6 (w a = 1.0, (6,32)), pIh(LS) and the new structures of Oh-Ih (w a = 1.0, (16,22) and (15,23)) that were not found previously for the average Gupta potential. 11,25 For w a = 0.8-1.0, the minima in excess energy occur at (18,20), after which there is a sudden increase of energy that can be explained by adding a single Au atom to the unfavourable core of the TO cluster.…”

“…4 Nanoclusters of Pd-Au supported on a variety of surfaces (e.g. magnesia, titania , silica, alumina) show great potential for a wide range of catalytic reactions, such as: acetylene cyclotrimerization (to yield benzene) and related reactions; 13 selective hydrogenation; [14][15][16] hydrodechlorination of trichloroethene in water at room temperature; 17 lowtemperature synthesis of hydrogen peroxide from oxygen and hydrogen, 18,19 CO and alcohol reduction; 20 the Sonagashira cross-coupling reaction; 21 and synthesis of vinyl acetate by acetoxylation of ethylene. 22,23 In this paper, the energetics, structures and segregation (chemical ordering) of Pd-Au nanoalloys are investigated as a function of composition for 34-and 38-atom clusters, using a genetic algorithm for global geometry optimisation (i.e.…”

First principles study of oxygen adsorption and dissociation on the Pd/Au surface alloys

“…Pd-Au bimetallic systems have been widely studied for applications in a vast number of catalytic reactions, such as CO oxidation, [1][2][3][4][5][6] butadiene selective hydrogenation, 7 H 2 O 2 production, [8][9][10][11] cyclotrimerization of acetylene, 12 vinyl acetate (VA) synthesis, [13][14][15] and alcohol oxidation. 16 Several forms of Pd-Au bimetallic catalysts have been identified and reported, including nanoclusters, [17][18][19][20] Pd clusters on Au nanoparticles, 21 Pd overlayers on Au surface, 22,23 and random alloy surfaces with varying Pd ensembles.…”

Gold–palladium core@shell nanoalloys: experiments and simulations

“…1,2 The case of nanoalloys is of topmost interest and they constitute an innovative type of catalyst, mainly due to the fact that their physicochemical properties can be tuned by varying the composition and atomic arrangement as well as their sizes and shapes. 3 Among various nanoalloys, the Pd-Au system is one of the most attractive systems in catalysis; 4 since alloyed and core@shell Au-Pd structures have been used as catalysts in the oxidation reaction of CO at low temperatures, 5 acetylene to ethylene conversion, 6 oxidation of alcohols to aldehydes and production of vinyl acetate monomers, selective hydrogenation of butadiene, 7 and the Ullmann reaction of aryl chlorides in water, 8 among others. [9][10][11] Due to the widespread diversity of applications of Au-Pd nanocatalysts, it is crucial to comprehend the structure, surface composition and growth mechanism of Au-Pd nanoalloys.…”