Abstract
Au and Ag were deposited on TiO2 modified with Ce, La, Fe or Mg in order to obtain bimetallic catalysts to be used for liquid-phase oxidation of 1-octanol. The effects of the deposition order of gold and silver, and the nature of the support modifying additives and redox pretreatments on the catalytic properties of the bimetallic Au-Ag catalysts were studied. Catalysts were characterized by low-temperature nitrogen adsorption–desorption, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and ultraviolet-visible diffuse reflectance spectroscopy. It was found that pretreatments with hydrogen and oxygen at 300 °C significantly decreased the activity of AuAg catalysts (silver was deposited first) and had little effect on the catalytic properties of AgAu samples (gold was deposited first). The density functional theory method demonstrated that the adsorption energy of 1-octanol increased for all positively charged AuxAgyq (x + y = 10, with a charge of q = 0 or +1) clusters compared with the neutral counterparts. Lanthanum oxide was a very effective promoter for both monometallic and bimetallic gold and silver catalysts in the studied process.
Highlights
Introduction iationsGold nanoparticles are unique catalysts for many low-temperature processes [1,2].The majority of the reported works deal with the tuning of the gold particle size, support modification and the pretreatment conditions [1,2]
We aimed to investigate the effect of the deposition order of gold and silver on the support, and the influence of modifying additives and redox pretreatments on the change in the catalytic, structural and electronic properties of these bimetallic Au-Ag catalysts for liquid-phase oxidation of 1-octanol
It should be noted that Au5 Ag5 with a random atomic arrangement had lower adsorption energy than the layered Au4 Ag6 and Ag4 Au6 clusters
Summary
The majority of the reported works deal with the tuning of the gold particle size, support modification and the pretreatment conditions [1,2]. Many research groups continue to look for ways to further improve the efficiency of nanogold catalysts. One of these methods is the synthesis of bimetallic systems consisting of two catalytically active metals, as well as the addition of modifying additives made of various compounds. It has been reported that several Au-containing bimetallic catalysts like Au-Cu [4,5], Au-Ag [6,7,8,9,10,11,12,13,14,15,16], Au-Pt [17,18] and Au-Pd [18,19,20] demonstrated an improvement in catalytic
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