Chemistry Reference
In-Depth Information
Fig. 30 Lowest-energy structures of Au
2
O
y
and Au
3
O
y
(
y
¼
1-5). All structures fall within an
energy range of 0.2 eV. The energy differences in eV with respect to the most stable structure are
given in round brackets. Labels of the symmetry group and the ground electronic state are also
given. Bond distances are in
Å
. Figure reproduced from reference [
307
]
Au
3
O
, replacement occurs for Au
3
O
3
(Eq. (
43
)) and oxidation (Eq. (
44
)) occurs
for Au
2
O
,Au
2
O
3
and Au
2
O
4
. Theoretical results suggest that oxidation reac-
tions mainly occur at the peripheral O atoms [
309
].
Gold oxide cluster cations react with CO via four types of reactions that also
depend on both
x
and
y
[
306
,
310
,
311
]: association (Eq. (
45
)), replacement
(Eq. (
46
)), oxidation of CO (Eq. (
47
)) and cluster fragmentation (Eq. (
48
)). Clusters
with one oxygen promoted oxidation (Eq. (
47
)), with Au
3
O
+
reacting more rapidly
than Au
2
O
+
[
311
]. Clusters with larger numbers of oxygen favoured adsorption of
CO and loss of O
2
(Eqs. (
45
) and (
46
)), while Au
2
O
3
+
,Au
3
O
3
+
,Au
4
O
2
+
and Au
4
O
3
+
all underwent some cluster fragmentation (Eq. (
48
)):
Au
x
O
y
þ
ð
þ
CO
!
Au
x
O
y
CO
ð
45
Þ
ð
þ
!
Au
x
O
y
2
CO
ð
46
Þ
Au
x
O
y
1
þ
!
CO
2
ð
47
Þ
ð
þ
þ
!
Au
x
1
O
y
2
CO
AuO
2
ð
48
Þ
A combination of experiments and theory provided detailed insights into how the
charge state of gold oxide cluster ions influences the mechanism of oxidation of CO
