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.
Activity of active oxygen species on supported Ag atoms can be effectively modulated by metal-support interaction using different oxide supports. The strong interaction between Ag and Al2O3 with more electrons...
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