Surface Hydroxyl-Determined Migration and Anchoring of Silver on Alumina in Oxidative Redispersion

Abstract

Hydroxyl (OH) groups are widely present on an oxide surface, which have been recognized as a key factor affecting surface properties of the oxide and interaction of the metal overlayer with the oxide. Here, γ-alumina (γ-Al2O3) supports with different OH contents are prepared by calcinating pseudo-boehmite (AlOOH) at different temperatures. The surface OH effect on oxidative redispersion of supported Ag nanoparticles including surface migration and anchoring of Ag species has been explored using in situ X-ray diffraction and UV–visible spectroscopy, as well as ex situ X-ray photoelectron spectroscopy and transmission electron microscopy. We reveal that the dispersion capacity, i.e., the amount of anchored Ag species associated with the steady dispersion state is thermodynamically determined by the surface OH contents, while the dispersion rate related to the surface migration process is kinetically limited by surface OH densities at low Ag loading. The higher dispersion ability is observed on the support with higher OH contents, and the quicker dispersion occurs on the support with higher OH densities. The results reveal that both OH contents and OH densities are critical in the redispersion of metal particles on oxide surfaces, which can be used to manipulate the Ag-catalyzed CO oxidation reaction.

Tuning the electronic structure of Pd by the surface configuration of Al2O3 for hydrogenation reactions

“…4(b), the peaks at approximately 531.0 eV and 532.3 eV are attributed to the lattice oxygen and surface hydroxyl groups, respectively. 39,40 Compared with the supports, Pd/γ-Al 2 O 3 shows a positive shift of 0.11 eV from the lattice oxygen, while Pd/η-Al 2 O 3 exhibits a positive shift of 0.02 eV. The lattice oxygen peak on Pd/γ-Al 2 O 3 shifts more positively due to more electrons transferring from the medium basic sites on the surface of γ-Al 2 O 3 to Pd NPs.…”

Recent Advancements in the Preparation and Application of Copper Single-Atom Catalysts

“…Cu 2+ ions, which have a size comparable to that of Al 3+ ions, have a tendency to diffuse into the lattice’s vacant metal positions. Additionally, Al 3+ centers that are coordinatively unsaturated and pentacoordinated are the binding sites for isolated metal atoms via weak oxygen bridges. , Compared to ordinary bulk Al 2 O 3 , the mesoporous alumina having greater Al 3+ defects shows enhanced stability, activity, and selectivity …”

“…Additionally, Al 3+ centers that are coordinatively unsaturated and pentacoordinated are the binding sites for isolated metal atoms via weak oxygen bridges. 129,130 Compared to ordinary bulk Al 2 O 3 , the mesoporous alumina having greater Al 3+ defects shows enhanced stability, activity, and selectivity. 131 Tunsten oxide (WO 3 ) is a viable support for the generation and stabilization of SACs.…”

A Minireview: The Mechanism of H2O2 Photoproduction by Graphitic Carbon Nitride

“…Elements doping, [31] introducing vacancies, [32] and constructing heterojunction [33] are all effective methods to broaden light absorption. Shi et al prepared holey defective g-C 3 N 4 (Holey DCN) with abundant nitrogen vacancies.…”