Main content area

Structural and electronic feature evolution of Au-Pd bimetallic catalysts supported on graphene and SiO2 in H2 and O2

Liu, Huan, Wu, Zhiwei, Wang, Ruiyi, Dong, Mei, Wang, Guofu, Qin, Zhangfeng, Ma, Jingyuan, Huang, Yuying, Wang, Jianguo, Fan, Weibin
Journal of catalysis 2019 v.376 pp. 44-56
alloys, catalysts, catalytic activity, dissociation, electron transfer, electrons, formates, geometry, gold, graphene, hydrogen, methanol, nanoparticles, oxidation, oxygen, palladium, silica, temperature
The structure and electronic feature evolution of graphene (Gr)- and SiO2-supported Au-Pd bimetallic nanoparticles (NPs) in H2 and O2 at different temperatures were investigated with a series of techniques and DFT calculation method. It was found that a uniform Au-Pd alloy nanostructure was formed on Gr, while a Au@Pd core-shell structure was generated on SiO2. The formation of Au-Pd alloy nanostructure on Gr originates from a strong s-p-d hybridization among Au 5d6s, Pd 4d and Gr C 2p, which greatly facilitates the electron transfer among Au, Pd and Gr and enhances the reduction of palladium species. The higher stability of the geometric and electronic structures of Au-Pd NPs on Gr than on SiO2 in both H2 and O2 atmospheres below 100 °C results from the fact that Gr could timely supplement the electrons transferring to O2 from metallic species in O2-treatment process, but play a contrary role in H2-treatment process. Such unique geometric and electronic structures endow Au-Pd/Gr show higher catalytic activity than Au-Pd/SiO2 in selective oxidation of methanol to methyl formate. A further investigation of catalytic mechanism reveals that the activation of O2 is dominated by the methanol-assisted way on Au and Au-Pd alloy NPs, whereas the direct dissociation of O2 mainly occurs on Pd and Au@Pd NPs.