A series of catalysts containing of gold-palladium bimetallic nanoparticles (Au-Pd NPs in the range of 1-6 nm) anchored on foam-like mesoporous silica were used for the aerobic oxidation of benzyl alcohol. A remarkable synergistic effect was observed on these Au-Pd NPs catalysts prepared by one-pot method. Both the experimental and theoretical study revealed a close relationship between the surface PdO species on the catalysts and their catalytic performance, that is, a higher surface PdO content leads to a lower catalytic activity. The surface content of PdO species on the catalysts could be tuned by controlling the Au/Pd ratios, because the formation of Au-Pd alloy NPs and electron transfer between surface Au and Pd atoms prevented the oxidation of surface Pd and retarded the formation of PdO species. An optimal Au/Pd ratio of 1/4.5 on the foam-like mesoporous silica support was obtained, with nearly no surface PdO species formed and resulted the highest benzyl alcohol conversion of 96%.The bimetallic Au-Pd catalysts exhibited much higher catalytic activity for benzyl alcohol oxidation (TOF = 50000 -60000 h -1 ) than the monometallic Pd catalyst (TOF = 12500 h -1 ) on which surface Pd is easily oxidized to PdO. These results provide direct evidence for the synergistic effect of the Au-Pd bimetallic catalyst in benzyl alcohol oxidation.

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A series of SnOx and MoOx promoted gold nanoparticle catalysts were used for the aerobic oxidation of benzyl alcohol.

A mesostructured cellular foam (MCF) silica was applied to support gold (Au)platinum (Pt) alloy nanoparticles (NPs) for benzyl alcohol partial oxidation. A catalytic synergy on bimetallic gold (Au)-platinum (Pt) nanoparticle (NP) catalyst, referring to that introducing Au to Pt leading to a higher catalytic performance has been observed. However, the essence of this synergistic effect is still under debate. In this work, a series of MCF supported Au-Pt NP catalysts are designed to reveal the essence. Well-developed porous structure of MCF support eliminated the mass transfer limitation and intrinsic catalytic activity was obtained.The improved catalytic performance on bimetallic catalyst is attributed to the geometric and electronic changes of active sites after formation of Au-Pt alloy NPs.Compared with monometallic catalyst, the formation of Au-Pt alloy results in the changes of particle size and lattice structure. Electronic property analyses confirmed the increase of d state electrons on Au-Pt alloy NPs, which are calculated from s-p-d hybridization and intra-atomic charge redistribution, leading to the increased abundance of transferable d electrons near Fermi level and further enhancing the catalytic activity. These findings gain new insights into the catalytic synergy of bimetallic nanoparticles and shed light on the optimization of these catalysts.