posted on 2021-11-17, 09:14authored byLulu Huang, Wen Liu, Jin Hu, Xiaopeng Xing
Reactivities of AgAun–1– (n =
3–10) with O2 at a low temperature were studied
using an instrument combining
a magnetron sputter cluster source, a microflow reactor, and a time-of-flight
mass spectrometer. Their reaction products as well as size-dependent
kinetic rates were nearly identical to those of corresponding Aun– (n =
3–10). Previous experiments showed that the Ag atom in AgAun–1– (n = 3–10) was fully or partially enclosed by the gold atoms.
We studied the adsorption of O2 on these reported structures
using the B3LYP theory with relatively large basis sets. The theoretical
results indicate that the adsorption sites as well as the adsorption
energies of O2 on AgAun–1– (n = 3–10) are nearly
identical to those on the corresponding Aun– (n = 3–10). The O2 adsorption on a series of proposed isomers of AgAun–1– (denoted as Aun–1Ag–), in which the silver
atom was on the protruding site, was explored using the same theoretical
methods. The O2 tends to bond with the protruding Ag atoms,
and the binding energies are apparently higher than those on the corresponding
Aun– and AgAun–1–. The adsorption and
activation of O2 on Aun–, AgAun–1–, and Aun–1Ag– were correlated with their global electron detachment energies (VDEs)
as well as the element types of the adsorption sites. Generally, low
VDE values and silver sites facilitate the O2 adsorption,
and these two factors separately dominate in various cluster species.
The revealed effects of a doping silver atom in small gold clusters
are helpful to understand the role of the residual silver components
in many nano gold catalysts.