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Article
IR Spectroscopic Evidence for MoS2
Morphology Changewith Sulfidation Temperature on MoS
2
/Al2
O3
CatalystJianjun Chen, Vincent Labruyère, Francoise Mauge, Anne-
Agathe Quoineaud, Antoine Hugon, and Laetitia OlivieroJ. Phys. Chem. C, Just Accepted Manuscript • Publication Date (Web): 19 Nov 2014
Downloaded from http://pubs.acs.org on November 20, 2014
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1
IR Spectroscopic Evidence for MoS2 Morphology Change with
Sulfidation Temperature on MoS2/Al2O3 Catalyst
Jianjun Chen1, Vincent Labruyere
2, Francoise Mauge
1, Anne-Agathe Quoineaud
2, Antoine Hugon
2, Laetitia
Oliviero1*
1. Laboratoire Catalyse et Spectrochimie, ENSICAEN, Université de Caen Basse Normandie, CNRS, 6, bd du
Maréchal Juin, 14050 Caen, France
2. IFP Energies nouvelles, Rond-Point de l’Echangeur de Solaize, BP 3, 69360 Solaize, France
Abstract: Low temperature CO adsorption followed by IR spectroscopy (IR/CO)
characterization was used to depict the MoS2 morphology change with sulfidation temperature on
MoS2/Al2O3 catalyst. It is found that the morphology of MoS2 slabs on MoS2/Al2O3 catalyst under
typical sulfidation temperature range (573 to 723 K) is truncated triangle exposing both M-edge
and S-edge. Moreover, the IR/CO data indicates that the truncation degree (ratio of S-edge/M-edge)
of MoS2 slabs gradually increases with increasing sulfidation temperature. This finding is in lines
with Density Functional Theory (DFT) calculation on model catalyst, providing the IR evidence
of MoS2 morphology change with sulfidation temperature on Al2O3-supported catalyst. As a
further step, it is also found that the MoS2 morphology is strongly influenced by MoS2-Al2O3
interactions under the same sulfidation temperature.
Keywords: Hydrodesulfurization (HDS), Molybdenum disulfide (MoS2), Slab morphology, S- and
M- edges, truncation degree, CO adsorption.
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1 Introduction
Co (or Ni)-promoted MoS2/Al2O3 catalysts have been for many years the most important
hydrotreatment catalysts in petroleum refinery. The active phase of these catalysts is obtained by
sulfiding the oxidic precursors with a gas phase H2S/H2 mixture or a feedstock of organic sulfur
compound at the temperature range of 573 to 723 K 1. Sulfidation temperature, which is of crucial
importance to the hydrotreatment catalysts, has strong influences on the active phase structure and
catalytic performance of the Co (or Ni)-promoted MoS2/Al2O3 catalysts 2-4
.
With DFT (density functional theory) calculations Raybaud and co-workers 5, 6
recently made
an important progress in understanding the effect of sulfidation temperature on MoS2-based
catalysts. In their studies, they found that the morphology of MoS2 slabs, i.e. the relative
concentration of M-edge and S-edge exposed, is controlled by the pseudo chemical potential of
sulfur that is a function of sulfidation temperature and partial pressure ratio of H2S and H2
(PH2S/PH2). Therefore, it is expected according to these DFT calculations that variation of
sulfidation temperature may lead to morphology change of MoS2 slabs. This is of great importance
to the performance of Co(or Ni)-promoted MoS2/Al2O3 catalysts, as it is proposed that the Co(or Ni)
promoters have different affinity to M-edge and S-edge 7-10
, and that CoMoS sites located at
different edges have distinct intrinsic activity11-13
. Although the MoS2 morphology change with
PH2S/PH2 has been imaged by Lauritsen et al. 14
using STM (scanning tunneling microscopy) on
Au-supported MoS2 model catalyst prepared by a special procedure under ultra-high vacuum
(UHV) conditions, the direct experimental evidence of MoS2 change with sulfidation temperature
on MoS2/Al2O3 catalyst is still lacking. Moreover, the isolated character of Al2O3 makes STM
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investigation of MoS2 morphology change on Al2O3 support extremely difficult.
As a proven technique, low-temperature CO adsorption followed by infrared spectroscopy
(IR/CO) is intensively used to probe the edges sites of MoS2 slabs on MoS2/Al2O3 catalysts. It has
been observed by IR/CO that there are distinctly two different CO adsorption bands located at
~2110 and ~2070 cm-1
on MoS2 edges 15, 16
. Combining experimental infrared spectra and
theoretical DFT calculations, Travert et al. 17, 18
well established that the v(CO) bands located at
~2110 cm-1
and ~2070 cm-1
are respectively attributed to CO adsorption on M-edge and S-edge of
MoS2 slabs. These attributions correspond to monocarbonyl adsorption on 6 coordinated Mo atoms
with 50% S-coverage on M-edge and 100% S-coverage on S-edge. In addition, a quantitative
evaluation of the M-edge and S-edge concentrations on MoS2/Al2O3 catalysts can be obtained after
determination of the integrated molar extinction coefficient of CO adsorbed on each edge (ref.19
and Supplementary Information). Recently, this IR/CO technique has been used successfully to
characterize the effect of citric acid addition on MoS2 morphology of MoS2/Al2O3 catalysts
allowing the determination of the intrinsic activity of sites from each edge20
.
In this paper, we use IR/CO to investigate the MoS2 morphology change with sulfidation
temperature on MoS2/Al2O3 catalysts. For this purpose, two types of Mo/Al2O3 catalysts with
monolayer Mo loading were prepared by conventional impregnation in the presence and absence of
citric acid. Citric acid was used as chelating agent to reduce the slab-support interactions after
sulfidation 21, 22
, expecting a clearer IR spectroscopic evidence of MoS2 morphology change with
sulfidation temperature20, 23
. The objective of this study is to verify the DFT prediction on MoS2
morphology change with sulfidation temperature, bringing the experimental evidence of such
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morphology change on MoS2/Al2O3 catalyst, which was used as a base of industrial hydrotreatment
catalyst.
2 Experimental
2.1 Catalyst preparation
Two types of Mo/Al2O3 catalysts were prepared by an one-step pore volume impregnation
method in the presence or absence of citric acid (CA). The impregnation solutions were firstly
prepared with or without citric acid (CA, C6H8O7.H2O, PROLABO) and ammonium
heptamolybdate tetrahydrate (AHT, (NH4)6Mo7O24.4H2O, MERCK). Sequentially, the pretreated
γ-Al2O3 support (Sasol, specific surface area of 252m2
/g and pore volume of 0.84mL/g,
pre-calcined in air at 723K for 2 hours) was added into the solutions and strongly shaken for 2
hours. Finally the catalysts were dried at 383K for 3 hours. Note that these catalysts were not
calcined in order to keep the citric acid in its initial form. Hereinafter, the Mo/Al2O3 catalysts
prepared with and without CA are denoted as Mo(CA)/Al2O3 and Mo/Al2O3, respectively. The Mo
content was kept at 0.19 mmol per gram Al2O3 support (corresponding to monolayer Mo) for each
catalyst, and the molar ratio of CA/Mo is 2 for Mo(CA)/Al2O3 catalyst.
2.2 Infra Red (IR) spectroscopy characterization
The IR characterization was performed on a newly designed system called CellEx 24
. The
CellEx mainly consists of three parts: (i) a stainless steel reactor for catalyst sulfidation under
different temperature, pressure and gas phase; (ii) an IR cell equipped with a spectrometer for
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spectroscopic characterization; and (iii) a transfer connection between the reactor and IR cell for
transferring sample under protecting of inert gas. With the CellEx, the catalysts can be activated
under different conditions and sequentially in situ characterized by IR spectroscopy without any air
pollution.
2.2.1 Catalyst sulfidation
Catalyst sulfidation were performed in the stainless reactor of CellEx 24
. Catalyst sample was
firstly grounded and pressed into self-supporting pellet of ~8 mg/cm2 (precisely weighted). The
pellet was introduced into the reactor that was then evacuated to 1.33 Pa to remove the air. After
that the pellet was sulfided in a flow of 30 mL/min H2S/H2 (10%). The sulfidation temperature was
reached at 3 K/min and maintained for 2 hours. Sequentially, the pellet was flushed with Ar and
then cooled down to room temperature under Ar. Finally, the sulfided pellet was transferred under
Ar to the IR cell for IR characterization.
2.2.2 Low-temperature CO adsorption followed by IR spectroscopy (IR/CO)
After the above-described sulfidation, the catalyst was firstly evacuated in the IR cell under
vacuum at 623 K (or at the sulfidation temperature if the pellet was sulfided at temperature lower
than 623 K) and kept for 1 hour with the final pressure to 10-3
Pa. After evacuation, the catalyst was
cooled down by liquid nitrogen to 100K for CO adsorption. CO adsorption was performed by
introducing small calibrated doses (0.8852 cm3) of CO at different pressures (0.03 ~1.20 µmol of
CO) and finally with 133 Pa CO at equilibrium in the IR cell. IR spectra of adsorbed CO were
recorded with a Nicolet spectrometer (Nexus) equipped with a MCT detector with 256 scans and 4
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cm-1
resolution. For comparison, all the spectra presented were normalized to a sulfided catalyst
pellet of 5 mg/cm2.
The concentration of each type of edge sites was obtained after spectral decomposition
performed on Peakfit V4.12 using “Autofit peak II—Second derivative Methods”. In spectral
decomposition, the center and full width at half height (FWHH) of the generated peaks were
allowed varying in fixed small range. The molar extinction coefficient of CO adsorbed on M-edge
(εεεεM-edge) was determined in the IR cell by introducing small doses of CO onto the 623 K sulfided
Mo/Al2O3 catalyst at liquid nitrogen temperature (100 K). The molar extinction coefficient of CO
adsorbed on S-edge (εεεεS-edge) was determined by subtracting the contribution of M-edge from the
spectra obtained after introducing small doses of CO onto the 623 K sulfided Mo(CA)/Al2O3
catalyst at liquid nitrogen temperature (100 K). The determined εεεεM-edge and εεεεS-edge are 20±3
µmol-1
.cm and 35±9 µmol-1
.cm, respectively. Details for spectral decomposition, εεεεM-edge and εεεεS-edge
determination, and edge concentration calculation are given in Supplementary Information.
3 Results
2250 2200 2150 2100 2050 2000 1950
(2069)
CO/S-edge
Adso
rba
nce
(a
.u.)
Wavenumber (cm-1)
0.05
623K
573K
723K
(2111)
(2155)
(2189) (2065)
CO/Al3+
CO/OH
CO/M-edge
(2113)
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Figure 1: IR spectra of CO adsorbed (133 Pa at equilibrium, 100 K) on Mo/Al2O3 catalyst sulfided with 10% H2S/H2 at
different temperatures
The Mo/Al2O3 catalyst was sulfided with 10% H2S/H2 at different temperatures (573, 623, and
723 K) and then in situ characterized by IR/CO. The obtained IR spectra of CO adsorption (133 Pa
at equilibrium, 100 K) are shown in Figure 1. On the Mo/Al2O3 catalyst sulfided with different
temperature, a quite strong CO adsorption band located at ~2111 cm-1
is recorded, which is
attributed to CO adsorption on M-edge of MoS2 phase 17, 18, 25
. Another two bands located at ~2189
and ~2155 cm-1
are also observed, which are assigned to CO adsorption on Al2O3 support 17, 18, 25
.
In addition, a shoulder band at ~2065 cm-1
is also detected, which is associated to CO adsorption on
S-edge of MoS2 slabs 17, 18, 25
. With increasing sulfidation temperature, the υ(CO) band on M-edge
(band at ~2111 cm-1
) is gradually decreased while the shoulder band attributed to CO adsorption on
S-edge (band at ~2065 cm-1
) slightly becomes clearer.
Besides the CO adsorption band intensity, as shown in Figure 1, the CO adsorption band
position on M-edge and S-edge also varies with sulfidation temperature. When the sulfidation
temperature increases from 573 to 723 K, the CO adsorption band on M-edge is gradually
upward-shifted from 2111 to 2113 cm-1
and that on S-edge is shifted from 2065 to 2069 cm-1
. The
increase of sulfidation temperature also leads to an upward shift of the CO adsorption band on OH
groups indicating an increase of their Brønsted acidity which can be explained by a partial
deshydroxylation in accordance with the concomitant decrease of the associated band area26
.
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2250 2200 2150 2100 2050 2000 1950
(2183)
(2152)
(2064)
(2108)0.05
Ad
sorb
an
ce
Wavenumber
573K
623K
723K
CO/Al3+
CO/OH CO/M-edge
CO/S-edge
(2111) (2068)
Figure 2: IR spectra of CO adsorbed (133 Pa at equilibrium, 100 K) on Mo(CA)/Al2O3 catalyst sulfided with 10%
H2S/H2 at different temperatures
The same experiments were performed on the Mo(CA)/Al2O3 catalyst and the obtained IR
spectra of low-temperature CO adsorption (133 Pa at equilibrium, 100 K) on this catalyst are
shown in Figure 2. On the 573 K sulfided Mo(CA)/Al2O3 catalyst, the υ(CO) band on M-edge
(band at 2108 cm-1
) is recorded with high intensity with a broad width. Meanwhile, the υ(CO) band
on S-edge (band at 2064 cm-1
) is observed as an ill-defined shoulder. On this sample and for this
lower temperature, the CO adsorption band on Al3+
sites is much lower than for the other sample
and than for the higher sulfidation temperatures. It can be thus proposed that part of Al3+
sites are
covered by citric acid residuals after sulfidation at 573K. With increasing sulfidation temperature,
the intensity of υ(CO) band on M-edge is decreased whereas the CO adsorption band on S-edge
becomes more pronounced. On the 723 K sulfided sample, the intensity of the υ(CO) band on
S-edge is even higher than that on M-edge.
Like for Mo/Al2O3 catalyst, the υ(CO) band position on M-edge and S-edge also varies with
sulfidation temperature on Mo(CA)/Al2O3 catalyst. The CO adsorption band on M-edge is
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upward-shifted from 2108 to 2111 cm-1
and that on S-edge is shifted from 2064 to 2068 cm-1
with
increasing sulfidation temperature. Meanwhile, the CO adsorption band on OH groups is decreased
and upward shifted. Like proposed for the Mo/Al2O3 catalyst, it would indicate an increased
Brønsted acidity due to partial deshydroxylation 26
.
560 580 600 620 640 660 680 700 720 740
0
20
40
60
80
100
120
140
560 580 600 620 640 660 680 700 720 740
0
20
40
60
80
100
120
140
S-edge/M-edge
(A) Mo/Al2O
3
Ed
ge c
on
ce
ntr
ation
(µ
mo
l/g
cata
lyst)
Sulfidation temperature (K)
M-edge
S-edge
0.0
0.2
0.4
0.6
0.8
1.0
Ra
tio
of
S-e
dge
/M-e
dge
Ed
ge c
on
ce
ntr
ation
(µ
mo
l/g
cata
lyst)
Sulfidation temperature (K)
M-edge
S-edge
S-edge/M-edge
0.0
0.2
0.4
0.6
0.8
1.0
(B) Mo(CA)/Al2O
3
Ra
tio
of
S-e
dge
/M-e
dge
Figure 3: M-edge and S-edge site concentration detected by low-temperature CO adsorption (dash line) and the ratio of
S-edge/M-edge (solid line) on (A) Mo/Al2O3 and (B) Mo(CA)/Al2O3 catalyst sulfided with different temperature
The obtained IR spectra were further decomposed using the software Peakfit V4.12 and the
concentration of M-edge and S-edge was calculated after determining the molar adsorption
coefficient of CO adsorption on each edge (details in Supplementary Information). As shown in
Figure 3 (A), the concentration of M-edge detected by low-temperature CO adsorption on
Mo/Al2O3 catalyst declines with increasing sulfidation temperature. The concentration of S-edge
on this catalyst is much lower than that of M-edge. With increasing temperature, the S-edge
concentration first slightly decreases and then level off. Nevertheless, the concentration ratio of
S-edge/M-edge is steadily increased with sulfidation temperature.
Figure 3 (B) illustrates the M-edge and S-edge concentration as well as the S-edge/M-edge
ratio on Mo(CA)/Al2O3 catalyst sulfided at different temperature. Like that on Mo/Al2O3 catalyst,
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the M-edge and S-edge concentration declines with increasing sulfidation temperature. Meanwhile,
the S-edge/M-edge ratio is also increased with increasing temperature. In addition, on
Mo(CA)/Al2O3 catalyst the concentration of S-edge is strongly enhanced, which becomes
comparable with that of M-edge. Thus, the S-edge/M-edge ratio on this catalyst is much higher
than that on Mo/Al2O3 catalyst.
Considering that the ratio of M-edge and S-edge for a single MoS2 slab is in line with the
overall ratio of each edge detected by IR/CO, a schematic diagram of MoS2 morphology on
Mo/Al2O3 and Mo(CA)/Al2O3 catalyst was depicted in Figure 3. First, the present IR spectroscopic
data shows that the morphology of MoS2 phase on both Mo/Al2O3 and Mo(CA)/Al2O3 catalyst is
truncated triangle exposing both M-edge and S-edge. Secondly, the truncation degree of MoS2
slabs on Mo(CA)/Al2O3 catalyst is much higher than that on Mo/Al2O3 catalyst, indicating that
addition of citric acid leads to the MoS2 phase exposing relatively more S-edge, as previously
observed20
. Thirdly, the truncation degree of MoS2 slabs steadily increases with increasing
sulfidation temperature on both Mo/Al2O3 and Mo(CA)/Al2O3 catalyst, demonstrating that
sulfidation temperature influences the morphology of MoS2 slabs on Al2O3-supported catalysts.
4 Discussion
In this work, low-temperature CO adsorption followed by IR spectroscopy (IR/CO) was used
to probe the concentration of M-edge and S-edge sites on Mo/Al2O3 and Mo(CA)/Al2O3 catalyst
sulfide with different temperature. First of all, it is found that the concentration of M-edge and
S-edge sites decreases with increasing sulfidation temperature on both Mo/Al2O3 and
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Mo(CA)/Al2O3 catalyst (Figure 3). The decrease of M-edge and S-edge concentration detected by
CO adsorption can be attributed to the decrease in dispersion of MoS2 phase with increasing
sulfidation temperature. This is in agreements with previous studies with other techniques, such as
NO adsorption 3 and HRTEM (high resolution transmission electron microscopy) study.
2. To
further verify such results, TEM was also performed on the Mo/Al2O3 catalyst and a general
increase of slab length and stacking was observed by TEM (more details in Supplementary
Information).
Another result obtained from IR/CO characterization is that the ratio of S-edge/M-edge
steadily increases with increasing sulfidation temperature on both Mo/Al2O3 and Mo(CA)/Al2O3
catalyst (Figure 3). We consider this result as a strong indication of MoS2 morphology change with
sulfidation temperature on these two catalysts. This consideration is taken based on the statistic
assumption that the ratio of S-edge/M-edge on a single MoS2 slab is in line with the overall ratio of
each edge detected by CO adsorption. Moreover, this ratio is hardly affected by other MoS2
characteristics such as slab length and stacking, although these characteristics are also changed
with sulfidation temperature (ref.2, 3
and Supplementary Information).
It should be stressed that the fine structure of MoS2 edges is supposed to differ with sulfidation
temperature, which will also influence the CO adsorption on M-edge and S-edge. However, the
change of MoS2 edge fine structure with sulfidation temperature cannot result in the increase of
S-edge/M-edge ratio observed in this study. Indeed, previous studies 14, 27-29
proposed that the
sulfur and hydrogen coverage on MoS2 edges varies with a pseudo chemical potential of sulfur
(∆µS) that is a function of temperature and PH2S/PH2. For the sulfidation conditions used in our work,
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the ∆µS is then determined according to Ref. 30
and is reported in Table 1. It appears that the
chemical potential of sulfur corresponding to the sulfidation conditions used in this work only
varies in a small range: it decreases from -0,80 eV to -0.95 eV with increasing temperature from
573 to 723 K. In this range, the sulfur coverage on both M-edge and S-edge should stay constant
with 50% on both edges according to DFT calculations 5. Meanwhile, this decrease of chemical
potential of sulfur should lead to an increase of hydrogen coverage on MoS2 edges 14, 28
, which may
partially (together with decrease of MoS2 edge dispersion) account for the decrease of M-edge and
S-edge concentration detected by CO adsorption. However, several investigations suggested that H
adsorbs more strongly on S-edge than M-edge 31-34
, which will result in a more significant decrease
of CO adsorption intensity on S-edge than that on M-edge and cannot lead to the IR/CO result that
the ratio S-edge/M-edge steadily increases with increasing sulfidation temperature. Thus, the
increase of S-edge/M-edge ratio is a convincing evidence of MoS2 morphology change although
the fine structure of MoS2 edges such as hydrogen coverage may increase with sulfidation
temperature.
Table 1: MoS2 morphology revealed by IR/CO experiments and predicted by DFT calculations in the sulfidation
temperature range in this work
Catalysts/DFT Temperature range
(T, K)
∆µS range (1)
(eV)
MoS2 truncation degree
(S-edge/M-edge)
Mo/Al2O3 [523, 723] [-0.80, -0.95] [0.17, 0.35], increases with temperature
Mo(CA)/Al2O3 [523, 723] [-0.80, -0.95] [0.59, 0.75], increases with temperature
DFT(2) / [-0.80, -0.95] [0.30, 0.43], increases with temperature
(1). ∆µS: chemical potential of sulfur, calculated according to ref. 30;
(2). DFT (Density functional theory) calculations in ref. 5, 6;
In addition, the IR/CO result that MoS2 morphology varies with sulfidation temperature is in
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good agreements with DFT calculations 5, 6
. In the ∆µS range corresponding to the sulfidation
conditions of our work, the MoS2 morphology predicted by DFT calculations 5, 6
is compared with
our IR/CO results on Mo/Al2O3 and Mo(CA)/Al2O3 catalyst in Table 1. It appears that our IR/CO
results are essentially in line with DFT calculations 5, 6
in two aspects. First, DFT calculations 5, 6
predicted that under HDS sulfidation conditions, the morphology of MoS2 slab is a truncated
triangle exposing both M-edge and S-edge. Correspondingly, CO adsorption bands on both M-edge
and S-edge were unambiguously recorded on Mo/Al2O3 and Mo(CA)/Al2O3 catalyst in our IR/CO
study. Secondly, the increase of temperature from 573 to 723 K (this study) corresponds to a
decrease of ∆µS from -0.80 eV to 0.90 eV 30
. In this ∆µS range, DFT calculations predicted that the
truncation degree of MoS2 increases with decreasing ∆µS 5, 6
. Thus, both IR/CO study and DFT
calculations suggest that the MoS2 truncation degree (ratio of S-edge/M-edge) increases with
increasing sulfidation temperature in the range of 573 to 723 K.
Nevertheless, the precise MoS2 morphology revealed by IR/CO is not identical with that
predicted by DFT calculations 5, 6
. As shown in Table 1, the truncation degree (S-edge/M-edge ratio)
of MoS2 predicted by DFT is [0.30, 0.43], which is in-between the IR/CO results on Mo/Al2O3
catalyst [0.17, 0.35] and Mo(CA)/Al2O3 catalyst [0.59, 0.75]. Such difference between DFT and
IR/CO study can be tentatively explained by the fact that the MoS2-support interactions were not
taken into account in the DFT calculations in references5, 6
. However, further DFT studies35
have
included slab-support interaction but in the case of alumina, the estimated truncation degree was
not modified due to weak calculated interaction for slabs of length around 3 nm. Meanwhile, this
explanation is further supported by the IR/CO results that the truncation degree of MoS2 on
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Mo(CA)/Al2O3 catalyst is always higher than that on Mo/Al2O3 catalyst in accordance with
previous study20
. Therefore, the present results indicate that the MoS2 morphology is also strongly
influenced by MoS2-Al2O3 interactions. Such finding is in line with the recent STM study by
Lauritsen and co-workers 23
, in which it was found that the MoS2 slabs adopt different
morphologies on different supports (Au, graphite, and TiO2).
5 Conclusions
In conclusion, low-temperature CO adsorption followed by IR spectroscopy (IR/CO)
characterization was successfully used to depict the MoS2 morphology change with sulfidation
temperature on Mo/Al2O3 and Mo(CA) /Al2O3 catalyst. Within typical HDS sulfidation
temperature range (573 to 723 K), it is found that the MoS2 phase on Mo/Al2O3 and Mo(CA)
/Al2O3 catalyst exposes both M-edge and S-edge, and that the concentration of each edge detected
by CO adsorption decreases with increasing sulfidation temperature. More important, the IR/CO
results reveal that the ratio of S-edge/M-edge steadily increases with sulfidation temperature,
indicating that the MoS2 slab becomes more heavily truncated. This effect of sulfidation
temperature on MoS2 morphology is in good agreements with DFT predictions 5, 6
, verifying the
relevance of these DFT studies for Al2O3-supported catalysts. As a further step, the present IR/CO
data reveals that the MoS2 morphology is also strongly influenced by MoS2-Al2O3 interactions
under the same sulfidation temperature.
Acknowledgements
The French Ministry of Research is acknowledged for the Ph. D. grant of J. Chen. Yoann Levaque,
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Valérie Ruaux, and Philippe Bazin are greatly acknowledged for the technical support on IR
experiment. Perla Castillo-Villalon is greatly acknowledged for the help on catalyst preparation.
Supporting Information
Supporting Information Available: spectral decomposition, εM-edge and εS-edge determination, edge
concentration calculation and Transmission Electron Microscopy results are available free of
charge via the Internet at: http://pubs.acs.or
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TOC
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