Supporting Information
A DFT Investigation on the Mechanism and Kinetics of Dimethyl
Carbonate Formation on Cu2O Catalyst
Riguang Zhang, Luzhi Song,
Baojun Wang*,
Zhong Li
(Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province,
Taiyuan University of Technology, Taiyuan 030024, Shanxi, People’s Republic of China)
The size effect of unit cell on calculation
We firstly investigate the necessary size for supercell, in which the adsorption energies and
optimized geometries of CO with C–down and CH3O with O–down adsorbed at CuCUS site for
different supercells are compared. When one molecule is placed on Cu2O(111)–[2×2] surface, the
coverage is set to 0.25 monolayer. CuCUS site is only considered according to the conclusion from
our previous studies [1] and the main text in this study. Table S1 lists the equilibrium parameters
and adsorption energies. It can be seen that the adsorption energies and optimized geometries of
CO do not change with the coverage. For the adsorption of CH3O, the adsorption energies and
optimized geometries have a large change from 1 to 1/4 ML coverages. However, the adsorption
energies and optimized geometries have little change from 1/4 to 1/6 ML coverages.
Table S1
The effect of supercell size in the surface model on the adsorbed configuration and
adsorption energies for CH3O and CO adsorbed at CuCUS site of Cu2O(111) surface, respectively a
Coverage b/ML
d(C－O)/nm
d(Cu－O(C))/nm
α/° c
Eads/kJ·mol-1
1
0.1424 (0.1149)
0.1819 (0.1834)
128.0 (179.8)
214.6 (131.1)
1/2
0.1412 (0.1148)
0.1820 (0.1835)
128.0 (179.9)
217.6 (131.1)
1/4
0.1423 (0.1149)
0.1827 (0.1835)
125.1 (179.9)
224.9 (131.1)
1
1/6
0.1420 (0.1148)
0.1824 (0.1835)
125.3 (179.5)
a
the values of CO adsorbed in parentheses.
b
ML Monolayer.
c
α denotes the angle between C–O axis and the binding surface Cu atom.
225.3 (131.1)
Then, we investigate the effect of the size of the surface unit cell on the adsorption energies
and optimized geometries for the larger reactant systems, such as, DMC and CH3OCO, as well as
the co-adsorption system of CH3O/OH, CH3O/CO, CH3OCO/CH3O, (CH3O)(OH)/CH3OH,
(CH3O)2/H2O and (CH3O)2/CO adsorbed on Cu2O(111)–[2×2] and [2×3] surface, respectively. Fig.
S1 and 2 show the structures with key structural parameters for these larger reactant systems on
Cu2O(111)–[2×2] and [2×3] surface, respectively, and the corresponding adsorption energies are
listed in Table S2.
It can be seen that the key structural parameters for these larger reactant systems adsorbed on
Cu2O(111)–[2×2] surface in Fig. S1 is nearly close to those on [2×3] surface in Fig. S2. Moreover,
the corresponding adsorption energies for these larger reactant systems on Cu2O(111)–[2×2]
surface is also close to those on Cu2O(111)–[2×3] surface, as presented in Table S2. Above
calculated results show that whether we use [2×2] or [2×3] supercell, the nearly same results for
these larger reactant systems can be obtained.
2
0.0973
0.1008
0.1708
0.4949
0.2727
0.0983
(b) (CH3O)2*/H2O
(a) (CH3O)*(OH)*/CH3OH
0.5207
0.1353
0.1218
0.1142
0.5144
0.1480
0.1374
0.1471
(d) DMC
(c) (CH3O)2*/CO
0.1143
0.2766
0.1473
0.4870
0.1422
0.1829
0.1419
0.2241
0.1940
(e) (CH3OCO)*/(CH3O)*
(f) (CH3O)*/CO
(CH3OCO)*/(CH3O)*
0.2841
0.1470
0.1391
0.1434
0.1221
0.1934
(g) CH3OCO
0.0976
(h) CH3O*/ OH*
Fig. S1 Optimized geometrical structures and parameters for the larger reactant systems on
Cu2O (111)–[2×2] surface (unit: nm).
Orange black balls represent Cu atoms; Red light balls represent O atoms; Grey black balls
represent C atoms and White light balls represent H atoms.
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0.0976
0.1012
0.1664
0.0984
0.4951
0.2732
(b) (CH3O)2*/H2O
(a) (CH3O)*(OH)*/CH3OH
0.5126
0.1359
0.1219
0.1143
0.5182
0.1466
0.1362
0.1464
(d) DMC
(c) (CH3O)2*/CO
0.1143
0.2697
0.1425
0.1826
0.1475
0.3995
0.1427
0.2203
0.1963
(f) (CH3O)*/CO
(e) (CH3OCO)*/(CH3O)*
(CH3OCO)*/(CH3O)*
0.1471
0.1434
0.1398
0.2946
0.0976
0.1221
0.1939
(g) CH3OCO
(h) CH3O*/ OH*
Fig. S2 Optimized geometrical structures and parameters for the larger reactant systems on
Cu2O (111)–[2×3] surface (unit: nm). See Fig. S1 for color coding.
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Table S2 The adsorption energies for the larger reactant systems, such as, DMC and CH3OCO,
as well as the co-adsorption system of CH3O/OH, CH3O/CO, CH3OCO/CH3O, (CH3O)(OH)/
CH3OH, (CH3O)2/H2O, and (CH3O)2/CO on Cu2O(111)–[2×2] and [2×3] surface, respectively.
Adsorption energies/kJ·mol-1
Adsorbed species
Cu2O(111)–[2×2] surface
Cu2O(111)–[2×3] surface
(CH3O)(OH)/CH3OH
416.4
406.0
(CH3O)2/H2O
336.1
344.4
(CH3O)2/CO
304.0
318.7
33.6
29.0
CH3O/CO
243.0
239.8
CH3OCO/CH3O
279.0
274.0
CH3OCO
204.4
206.2
CH3O/OH
394.9
392.3
DMC
Afterwards, we investigate the size effects of unit cell on reaction energies and activation
barriers involving in the reaction of CO insertion to methoxide species and methoxide reaction
with carbomethoxide to DMC on Cu2O(111)–[2×2] and [2×3] surface, respectively. The
corresponding reaction energies and activation barriers are presented in Table S3. In addition, we
also compared the key structural parameters of transition states on Cu2O(111)–[2×2] and [2×3]
surface, respectively. Fig. S3 shows the structures with key structural parameters for transition
states involving in the reaction of CO insertion to methoxide species and methoxide reaction with
carbomethoxide to DMC on Cu2O(111)–[2×2] surface, respectively, and Fig. S4 shows those on
Cu2O(111)–[2×3] surface. Similarly, our results also show that the reaction energies and activation
barriers of above two reactions on [2×2] surface, as well as the corresponding geometrical
structure of transition states are also close to those on [2×3] surface. Once again, our calculated
results suggest that whether we use [2×2] or [2×3] supercell, the same results can also be obtained.
Therefore, based on the above discussions, we can think that whether we use [2×2] or [2×3]
supercell, the same results can be obtained. As a result, taking calculation efficiency into
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consideration, a [2×2] supercell is large enough for our studied system, and is employed in our
present study.
Table S3
The reaction energies (Er) and activation energies (Ea) involving in the reaction of CO
insertion to methoxide species and methoxide reaction with carbomethoxide to DMC on
Cu2O(111)–[2×2] and [2×3] surface, respectively.
the size of unit cell
Reactions
CH3O+CO→CH3OCO (TS3)
CH3O+CH3OCO→DMC (TS4)
Cu2O(111)–[2×2]
Cu2O(111)–[2×3]
Er /kJ·mol-1
-54.0
-53.4
Ea/kJ·mol-1
161.9
169.4
Er /kJ·mol-1
-148.9
-153.8
Ea/kJ·mol-1
98.8
96.2
0.2015
0.2049
0.1442
1
0.2503
2
0.1157
2
0.2857
0.2557
(a) TS3
1
0.1450
0.2891
(b) TS4
Fig. S3 The geometrical structures with key parameters of the transition states involving in the
reaction (a) CO insertion to methoxide species and (b) methoxide reaction with carbomethoxide to
DMC on Cu2O (111)–[2×2] surface (unit: nm). See Fig. S1 for color coding.
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0.2079
0.2034
0.1443
1
0.2503
2
0.1153
2
0.2975
0.2519
(a) TS3
1
0.1448
0.2709
(b) TS4
Fig. S4 The geometrical structures with key parameters of the transition states involving in the
reaction (a) CO insertion to methoxide species and (b) methoxide reaction with carbomethoxide to
DMC on Cu2O (111)–[2×3] surface (unit: nm). See Fig. S1 for color coding.
References
[1] Zhang, R. G.; Liu, H. Y.; Ling, L. X.; Li, Z.; Wang, B. J. Appl Surf Sci 2011, 257, 4232–4238.
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