Decoration of Cube‐Like Ceria Crystals by Well‐Dispersed Au Nanoparticles: Surface Influence

Abstract

In this paper, the run of the decorating process of the active support, like CeO2, by the gold nanoparticles via deposition‐precipitation method has been studied. Two types of the Au/CeO2 systems with different mean particle size (but the same morphology) of the support have been investigated. It was noted that the decoration process proceeds easily only for large crystals with average size about 67 nm. Three hypotheses were tested in order to explain unsuccessful initial Au nanoparticles decoration of the cube‐like CeO2 crystals with average size about 14 nm as a support. The tests have shown that the ratio of the molar content of the chloroauric acid to the total surface area of the support (MAu/SCeO2) has a significant impact on the decorating process of CeO2 by nano‐Au. If the above ratio is too small, the thin layer of gold instead of the Au nanoparticles is formed on the support surface. In this paper, the calculations of the real surface area (from TEM/HRTEM data) were used to adjust the optimum the MAu/SCeO2 to obtain the Au/CeO2 system with the desired properties.

Hierarchical Au/CeO2systems – influence of Ln3+dopants on the catalytic activity in the propane oxidation process

“…The decoration process of the pure and Ln-doped hierarchical ceria tube-like macroparticles by gold nanoparticles was performed by the deposition–precipitation method. 60 As shown in the literature 86–89 and our previous experiences, 61,90 the decoration method used in this work is effective in obtaining ceria (or defected ceria) with small gold nanocrystals well dispersed on the surface (with various support morphologies – cubes, octahedra, rods, etc. ).…”

“…Moreover, as shown in ref. 61, a key role in the decoration process is played by the ratio of the molar content of the chloroauric acid to the total surface area of the support ( M Au / S support ). In view of the high surface area of the support S BET (see Table 2), it was necessary to use a large amount of gold to obtain Au particles with a size of about 3–4 nm.…”

“…It is in line with our previous experiences with Au/CeO 2 (ref. 61 and 90) systems. As shown in Table 3, it seems that gold nanoparticles deposited on Ln-doped supports are slightly smaller than those dispersed on pure CeO 2 .…”

“…60 The mixture (suspension) of ceria or mixed oxide macro-particles, HAuCl 4 , (NH 2 ) 2 CO and H 2 O was stirred and kept at 80 °C in a silicone oil bath for 24 h. The amount of gold in the hierarchical Au/oxide samples was described as follows: 5 particles of HAuCl 4 on 1 nm 2 (surface area) of the hierarchical support. 61 Then, the obtained product was washed and dried at 70 °C. The solid product was heated at 300 °C in static air for 3 h (heating rate: 5 °C min −1 ).…”

Confinement of nano-gold in 3D hierarchically structured gadolinium-doped ceria mesocrystal: synergistic effect of chemical composition and structural hierarchy in CO and propane oxidation

“…Especially, the value of Au-9.8 wt% for Au2/CeO 2 again implies the high sorption potential of the hierarchically structured particles, considering that all the gold was absorbed inside the particles. In the case of the model catalyst composed of Au2/CeO 2 nanocubes (gold loading value M Au /S CeO 2 = ∼2), no distinct AuNPs were observed on ceria, 53 in contrast to the hierarchical ceria support with a roughly similar gold loading (SC = 2). This confirms that the confined space in the hierarchical support allows the formation of gold particles for a relatively low SC value.…”