Effects of the Fe/Ce ratio on the activity of CuO/CeO2-Fe2O3 catalysts for NO reduction by CO

Article abstract of DOI:10.1039/c8cy00709h

Copper catalysts on Fe-loaded ceria were studied for NO reduction by CO. Catalysts with different Fe/Ce molar ratios (Cu/C₁F_x) were synthesized by a wet impregnation method. Catalysts were characterized by XRD, BET, Raman, EPR, H₂-TPR and in situ DRIFTS. CuO was highly dispersed on the support surface to form active species. Ceria modification by incorporation of a lower amount of Fe³⁺ was beneficial for NO conversion and N₂ selectivity as compared with pure ceria and iron-rich ones, which resulted from the strong interaction between ceria and iron. Cu/C₁F₁ showed better catalytic performance at 100-200 °C, whereas Cu/C₁F_0.5 gave higher N₂ selectivity than the other samples. In situ DRIFTS suggested that iron-rich catalysts ensured inhibition of NO reduction by increasing the partial pressure of NO. Two mechanisms could explain formation of the NCO intermediate and N₂O intermediate over ceria-rich catalysts. With an increase in the Fe/Ce molar ratio and temperature, a mechanism in which N₂O is the intermediate dominates the reaction, whereas a process in which NCO species are produced as intermediates results in their gradual disappearance.

Full text of DOI:10.1039/c8cy00709h

View Article Online
View Journal
Catalysis
Sc ience &
Technology
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: X. Zhang, X.
Cheng, M. Chuanyuan and Z. Wang, Catal. Sci. Technol., 2018, DOI: 10.1039/C8CY00709H.
Volume 6 Number 1 7 January 2016 Pages 1–308
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Catalysis
Science &
Technology
www.rsc.org/catalysis
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 2044-4753
PAPER
Qingzhu Zhang et al.
Catalytic mechanism of C–F bond cleavage: insights from QM/MM
analysis of fluoroacetate dehalogenase
rsc.li/catalysis

Page 1 of 12
C Pa l tea al ys se i sd So c ni eo nt c ae d &j u Ts et cmh an rog l ion gs y
View Article Online
DOI: 10.1039/C8CY00709H
Catalysis
Science &
Technology
PAPER
Effects of Fe/Ce ratio on the catalytic activity of CuO/CeO -Fe O
3
2
2
catalysts for NO reduction by CO
Received 00th April 20xx,
Accepted 00th Apri 20xx
ab
ab
ab
ab
Xingyu Zhang , Xingxing Cheng* , Chunyuan Ma* and Zhiqiang Wang
DOI: 10.1039/x0xx00000x
Copper catalysts on Fe-loaded ceria were studied for NO reduction by CO. The catalyst with different Fe/Ce molar ratio
Cu/C ) were synthesized by impregnation method. The catalysts were characterized by XRD, BET, Raman, EPR, H -TPR
and in situ DRIFT spectra. CuO was highly dispersed on support surface to form active species. The ceria modification by
(
1
F
x
2
www.rsc.org/
3
+
incorporation of lower Fe amount is beneficial for NO conversion and the N
and iron-rich ones, which would be resulted from the strong interaction between ceria and iron. Cu/C
catalytic performance at 100-200 °C, while Cu/C 0.5 gave the higher N selectivity than other samples. In situ DRIFT results
suggested that rich-iron catalysts ensured an inhibition of the reduction of NO by increased NO partial pressures. There
exists two mechanisms that form the NCO intermediate and N O intermediate over ceria-rich catalysts. With the
increasing of Fe/Ce molar ratio and temperature, The mechanism of N O as intermediate dominate the reaction, while the
process that produced NCO species as intermediate gradually disappear.
2
selectivity as compared with the pure ceria
1 1
F
showed better
1
F
2
2
2
investigating the performance over various supported noble metal
A Headings are the primary heading type e.g.
Introduction, Results and discussion,
Experimental
10
11
12
catalysts, such as Pd/Al
2
O
3
,
Rh/Al2O
3
,
Pt/WO
3
2 2
/CeO /ZrO ,
13
14
15
Pt/SBA-15, Au/CeO
2
–M
2
O
3
(M = Al, La), Ir/WO –SiO . In recent
3 2
years, ceria (CeO ) has been received increasing attentions and
2
The abatement of NO
importance for environmental protection. Nitric oxide reduction
by CO is a new technology in the removal of NO from stationary
x
from the combustion of fossil fuel is of great
found tremendous applications in environmental catalysis due to its
1
-6
4
+
3+
high oxygen storage-release capacity associated with Ce /Ce
x
16, 17
+
redox cycle.
When doped with Cu ions, ceria acts as highly
7
-9
sources emission using rotary reactor. The catalyst with excellent
active deNOx catalysts with high resistance to H O and SO2
2
performance not only could be used at the reactor work as the
1
8
poisoning. Nevertheless, it still showed the unsatisfactory activity
and selectivity for NO reduction at low temperature, especially for
the stability of the catalysts structure. Generally, the most studied
component of the catalysts has been cerium oxide since it is able to
stabilizes the dispersion of active metal oxides and it stores and
medium of NO
x
adsorbed and reduced, but also could reduced the
from the surface of the catalyst by CO in the
desorption NO
x
reducing gas. Meanwhile, low reaction temperatures are of great
significance for cost savings. Hence, the catalyst with superior
catalytic activity at low temperature exhibit multifunctional
application potential.
1
9
releases oxygen. Therefore, many studies worldwide aim at
improve efficiency and stability by introducing other promoters,
For NO + CO reaction, many efforts have been spent on
1, 20
21
22
23
24, 25
such as alumina,
zinc, stannum, cobalt, molybdenum,
2
6
27-30
magnesium, and zirconia.
The nature of dopant plays an important role for ceria
modification, and the interaction between ceria and dopant could
promote the catalysis. Research shows that doped-ceria with
3
+
3+
trivalent ions (Pr and Tb ) result in a lowering of the energy
This journal is © The Royal Society of Chemistry 2018
J. Name., 2018, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Catalysis Science & Technology
Page 2 of 12
View Article Online
DOI: 10.1039/C8CY00709H
ARTICLE
Journal Name
3
1, 32
barrier for oxygen migration,
this seems to be beneficial for the (DXRD) were determined from XRD line broadening measurements
formation of oxygen vacancies. Whereas the outstanding using the Scherrer equation, DXRD Kλ/βcosθ, where λ is the X-ray
performance of Fe for redox capacity and N O reduction by CO wavelength, θ is the diffraction angle, K is the particle shape factor,
2
O
3
2
3
3
draw our attention. Hence, it was expected that combining the usually taken as 0.89, and β is full width at half maximum in radians.
advantages of CuO/CeO2 system and iron oxides promoter to Raman pectra were collected on a Jobin-Yvon (France-Japan)
+
achieve the goal of high reactivity and low cost.
T64000 type Raman spectroscopy using Ar laser beam. The Raman
spectra were recorded with an excitation wavelength at 514nm and
the laser power at 300mW. The EPR spectra were recorded on a
EPR spectrometer (JEOL-FE-1X) operating in the X-band frequency
In this paper, we systematically synthesized a series of
2 2 3
Cu/CeO -Fe O composites with the Fe atomic ratio (Ce balance)
varying from 0 to 100%. Their structures were characterized by
means of X-ray diffraction (XRD), BET surface area measurement,
Raman spectroscopy, and Electron Paramagnetic Resonance (EPR).
(
≈9.200 GHz) with a field modulation frequency of 100 kHz. The
magnetic field was scanned from 0 to 500mT and the microwave
power used was 5mW. The measurements were made at room
The catalytic performance of Cu/CeO
2 2 3
-Fe O composites in NO
temperature. H
type reactor, and 50 mg sample was used for each measurement.
Prior to the reduction, the catalyst was pretreated in N stream at
20 °C for 1 h and then cooled to room temperature. After that, H
2
-TPR experiments were performed in a quartz U-
redution by CO was also tested. The role of Fe on Cu/CeO -Fe O is
2
2
3
discussed. The purpose of the present work is not only to assess the
deNOx capability of the Cu/CeO -Fe catalysts, but more
2
2
2 3
O
1
2
–
importantly to clarify the nature of Fe-doped for catalytic
performance.
Ar mixture (10% H
2
by volume) was switched on, and the
temperature increased gradually with a ramp of 10 °C/min. The H2
consumption was monitored using a thermal conduction detector
2
. Experiments
Catalysts preparation
(
TCD). In situ DRIFTS spectra was collected at 300°C temperature on
The mixed oxides of CeO2 and Fe O3 are prepared by co-
2
a Nicolet 6700 FT-IR spectrometer, working in the range of wave
precipitation method. The requisite amount of Ce(NO
3 3 2
) ·6H O as Ce
−
1
−1
numbers 650–4000cm at a resolution of 4 cm (number of scans,
source and Fe(NO ·9H O as Fe source was dissolved into distilled
3
)
3
2
6
4). The spectra of empty FTIR cell was collected in NO and CO
water to form solution. After being stirred for 1h, the solution was
evaporated in air at 160 °C for 2h, and then calcinated in air at 550
atmosphere at various target temperatures as background. The
catalysts (∼10 mg) were mounted in a quarts FTIR cell and
pretreated for 1 h at 100 ◦C in flowing Ar atmosphere. After cooled
to room temperature, the sample wafers were exposed to a
controlled stream of CO–Ar (0.5 % of CO by volume) and NO–Ar
mixture (0.2% of NO by volume) at a rate of 50 ml/min for 30 min.
°
C for 3h. The as-prepared CeO
2
-Fe
2
O
3
oxide supports were
and Fe were
hereafter denoted as CF. In addition, pure CeO
2
2 3
O
prepared via the same procedure for comparison. The Cu/CF
catalysts were prepared by wetness impregnation method with
Cu(NO
60 °C for 2h, and finally calculated in air at 550 °C for 3h. Catalysts
with individualoxide CeO and Fe support are named as Cu/Ce
3 2
) solution. The mixture was kept in stirring 1h, dried in air at
-1
Then, the cell was heated at a rate of 10 °C min ,All of the
presented spectra were obtained by subtraction of the
corresponding background reference.
1
2
2 3
O
and Cu/Fe, respectively. Some main properties of the prepared
catalysts are summarized in Table 1.
Catalytic activity measurement
The catalytic activity experiments were performed in a fixed bed,
Catalyst characterization
down flow, quartz reactor (length, 30 cm; inner diameter, 4 mm).
The NO + CO reaction was investigated under steady state,
involving a fixed feed with a gas composition of 800 ppm NO, 1600
The specific surface area was investigated by nitrogen adsorption at
77 K (Quantachrome Autosorb-iQ) using the BET method. The pore
volume and average pore diameter were derived from the BJH
method. XRD patterns were recorded on a Philips X’Pert Pro
diffractometer, equipped with a Ni-filtered Cu K radiation (0.15418
nm). The X-ray tube was operated at 40 kV and 40 mA. The data
were ollected in the 2 range of 10–80◦. The average crystallite sizes
ppm CO and N
2
by volume as a carrier gas at a space velocity of
−
1
3
0,000 h . For each measurement, 50mg catalyst was pretreated in
N2 stream at 100 °C for 1 h and then be cooled to room
temperature. After that, the valve gear was switched to the
2 2
reaction gas. Concentration of NO, N O, CO and CO at the inlet and
2
| J. Name., 2018, 00, 1-3
This journal is © The Royal Society of Chemistry 2018
Please do not adjust margins

Page 3 of 12
C Pa l tea al ys se i sd So c ni eo nt c ae d &j u Ts et cmh an rog l ion gs y
View Article Online
DOI: 10.1039/C8CY00709H
Journal Name
ARTICLE
the outlet of the reactor were simultaneously monitored by an
online combustion gas analyzer (Gasmet DX-4000, Finland).
♦
♦
:CeO2
•
:Fe Ο3
2
3
. Results and discussion
∗
:CuΟ
♦
Characterization of catalysts
♦
♦
•
Fig. 1 presented the XRD patterns of Cu/CF catalysts. It can be seen
♦
♦
Cu/Ce
♦
♦
•
•
∗
•
•
•
•
• •
•
2 2 3
that CuO, CeO and α-Fe O characteristic peaks appear for all the
Cu/C F
1
0.1
present catalysts. The extremely small CuO peak at about 38.79°
indicating that copper oxide was well dispersed in all the catalysts.
With the decrasing Ce/Fe ratio, the peak corresponding to cubic
fluorite structure of ceria gradually weakened, indicating that the
loading of iron reduced the content and crystallinity of ceria.
Cu/C F
1
0.5
Cu/C F1
1
1
Cu/C F5
Cu/C F
1
10
Cu/Fe
10
20
30
40
50
60
70
80
2
However, no observable shift in diffraction lines of CuO, CeO and
2θ
α-Fe
2
O
3
can be found in all catalysts, indicating that there is no Fig. 1 XRD patterns of the studied copper catalysts on Fe-doped ceria
supports
change of crystallite structure. From Table 1, it could be seen that
the crystallite size of α-Fe in catalysts increased crystallite size of
CeO in catalysts is similar. However, the crystallite size of CuO vary metal-oxygen arrangement and lattice defects, was performed to
2
O
3
Raman spectroscopy, as a potential tool and sensitive to
2
3
4, 35
greatly in size and Cu/C
1
F
1
has the smallest crystallite size. obtain additional structural information
. As shown in Fig. 2,
-1
Additionally, the decreased of Ce/Fe molar ratio also leads to three typical bands of crystalline CuO at 298, 340, and 628 cm
decreased surface area and pore volume.
were not observed, which suggests that copper interaction of Cu
and Ce species probably occurred through the formation of a Cu-O-
36
Ce bond. Similar results were also reported by Li et al.
-
1
Additionally, the strong peak at 458 cm for the Cu/Ce sample was
attributed to triply degenerate F2g mode of the fluorite-type lattice,
which can be viewed as a symmetric breathing mode of oxygen
3
7
atoms around cerium ions . The Raman band position and width
could be influenced by phonon confinement, strain, defects, and
3
8
variation in the particle size . Once iron species is introduced, this
-1
-1
peak shifts from 458 cm for the Cu/Ce sample to 451cm for the
Cu/C sample, and becomes weaker. This shift may imply that
slight changes in the lattice parameter with particle size and the
1 5
F
Table 1 Copper oxide, cerium oxide and iron oxide loading and BET surface area and crystallite size of catalysts
a
Catalysts
Cu/Fe
CuO
loading
CuO loading
Ce/Fe
molar
ratio
BET surface
area(m /g)
Pore
Crystallite size (nm)
Fe
2
2
（mmol/100m ）
Volume
3
(
%)
(cm /g)
CuO
2
O
3
CeO
2
b
b
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.05
0.04
0.02
0.013
0.01
0.008
0.0079
-
10
12
24
38
51
59
63
0.08
0.09
0.11
0.14
0.15
0.18
0.22
22
22
25
19
15
14
13
n.d.
n.d.
12
Cu/C
1
F
10
1:10
1:5
1:1
1:0.5
1:0.1
-
23
26
20
26
33
25
Cu/C
Cu/C
1
F
F
5
1
1
16
13
14
12
Cu/C
Cu/C
1
F
F
0.5
0.1
1
b
Cu/Ce
n.d.
2 3 2
The crystallite size of CuO, Fe O and CeO from the crystal plane diffraction peak (111), (111) and (104), respectively.
a
Crystallite size determined from the xrd diffraction peak by Scherrer equation
Not detected
b
This journal is © The Royal Society of Chemistry 2018
J. Name., 2018, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Catalysis Science & Technology
Page 4 of 12
View Article Online
DOI: 10.1039/C8CY00709H
ARTICLE
Journal Name
39, 40
presence of oxygen vacancies
, which is related to structural ions in the lattice with the smallest distance (3.811 A° ). This
. The appearance substitution only occurs on the surface and does not destroy the
0.5 attributed to matrix structure of Fe and CeO . Compared with Cu/Fe, Cu/Ce
2 3
hematite (α-Fe O ) and these peaks shifts from the above to 291, shows stronger signal, indicating that the larger specific surface
defects derived from interaction of iron and CeO
2
-
1
of other bands at 284, 400 and 591 cm for Cu/C
1
F
2
O
3
2
-
1
37, 41, 42
2+
4
07 and 606 cm for Cu/Fe
new bands at 224 and 496 cm for Cu/C
Cu/Fe attributed to hematite (α-Fe ) and that was not seen in the introduced, the signal intensity decreases with Fe/Ce molar ratio.
other catalysts. Thus, the present results indicate that the presence The reason is easy to understand that the doping of undispersible
. Meanwhile, the appearance of area of CeO promotes the dispersion of Cu and the substitution
2
-1
2+
4+
1 1 1 5 1 2 3 2
F , Cu/C F , Cu/C F10 and of Cu for Ce . However, when both of Fe O and CeO are
2 3
O
2
+
of over-proportional ceria influences the crystal lattice of iron Cu is difficult when specific surface area of Cu/C F decreases. the
1
x
3
+
4+
2+
oxide. Fe is much easier to occupy the substituted Ce sites in the signals at g
‖
= 2.329 and g
‖
= 2.335, are contributed by isolated Cu
3
+
CeO
2
lattice as the concentration of doped Fe is below the critical in octahedral sites of ceria with a tetragonal distortion and in
4
3
value and prefers to become interstitial within the ceria structure surface substitution sites of ceria, respectively . Meanwhile, a
3
+
37
3+
when the concentration of doped Fe surpasses the critical value . typical EPR spectrum for Fe ions in Cu/Fe, Cu/C
1 1 1
F10 and Cu/C F
As it was reported that a change of the particle size of CeO from 6 catalysts. The EPR spectra mainly consists of an intense resonance
2
-139, 40
3+
nm to 5 μm led to a shift in peak position about 10 cm
.
signal at g≈4.3, it can be attributed to the isolated free Fe (smaller
However, in the case of the XRD results, all catalysts have similar iron oxides phases). In particular for Cu/Fe, the EPR spectrum shows
3
+
crystallite size of CeO
peaks of these Cu/C1Fx catalysts suggest may only lower Fe
amount could incorporate into ceria oxide lattice and the vast than 2.0, indicting to rhombic distortions of the crystal field around
2
, the results of Raman and XRD characteristic a shoulder in the region of g≈6.3. The g value of Fe is expected to
3
+
lie very near the free-ion value and the g value very much greater
3
+
44
45, 46
majority of Fe still exist in the form of Fe
2
O
3
.
Fe ions . Some investigators
suggested that these large g
3
+
value of catalysts containing Fe ions is related to the coordination
number, and the g≈4.2 resonance signal is due to low symmetry
4
51
58
4
4
4
(rhombic) sites of either tetrahedral or octahedral coordination .
Cu/Ce
Interestingly, with increase of Ce/Fe molar ratio, both of the two
Cu/C F
1
0.1
0.5
1
3
+
Cu/C F
signals contributed to Fe almost disappear, corresponding to the
1
Cu/C F
3+
37
1
the isolated free Fe gradually disappears . In order to further
elucidate the different iron species with Ce/Fe molar ratio, the
evolution of this resonance line with the decrease of Fe/Ce molar
ratio is following in the dependence of the EPR parameters. These
parameters are: the peak-to-peak line width ΔB and the line
Cu/C F
1
5
Cu/C F
1
10
Cu/Fe
407
224
496
2
84291
591 606
2
intensity approximated by J=I(10*ΔB) where I denotes the line
47
height . The corresponding variations of the separameters for the
2
00
300
400
500
600
700
800
ꢀ1
Raman shift (cm )
Fig. 2 Raman spectra of the studied copper catalysts on iron-ceria supports
studied Cu/C Fx samples are presented in Fig. 3 for the resonance
1
lines at g ≈ 4.3 (Fig. 3b) and g ≈ 2.23 (Fig. 3c), respectively.
EPR was performed to investigate the surface oxidation According to Fig. 3b, the line intensity of the resonance centered at
states, the physical form of the transition metal oxides, and some g ≈ 4.3 increases with the decreasing of Fe/Ce molar ratio, the
synergetic interactions on the surface. Fig. 3a shows the spectra of signal intensity being proportional to the quantity of EPR active
the representative catalysts. The EPR spectra exhibit multiple species involves in the resonance absorption. The increase of this
signals of copper, the signal that showing unresolved parallel resonance line intensity at the same time with the decreasing of
component at g
= 2.040, is ascribed to the copper(II) ion pairs in Fe/Ce molar ratio is due to the destruction of the configuration
┴
2
+
4+ from the iron ions vicinities, which assures their magnetic isolation.
The intensity of g ≈ 2.23 absorption line decreases with the
ceria, i.e., the substitution of two Cu ions for two neighboring Ce
4
| J. Name., 2018, 00, 1-3
This journal is © The Royal Society of Chemistry 2018
Please do not adjust margins

Page 5 of 12
C Pa l tea al ys se i sd So c ni eo nt c ae d &j u Ts et cmh an rog l ion gs y
View Article Online
DOI: 10.1039/C8CY00709H
Journal Name
decreasing of Fe/Ce molar ratio, which further confirms that the
ARTICLE
a
g=6.3
3
+
g=4.36
g=4.2
g=2.335
g=2.329
formation of polymeric Fe clusters are less. The line width
evolution of the g ≈ 4.29 and g ≈ 2.23 resonance lines (Fig. 3b and
3c) shows a monotonically decrease with the decreasing of Fe/Ce
molar ratio, which is associated to the dipole–dipole interactions
and the interactions between iron ions and iron ions. Which
manifest that with of Fe/Ce molar ratio decreasing, the content of
Cu/Fe
Cu/C
F
1
10
5
Cu/C F
1
Cu/C F
1
1
Cu/C F
3
+
1
0.5
0.1
distorted tetrahedrally coordinated isolated Fe ions increases
Cu/C F
1
Cu/Ce
whereas that of the distorted octahedral coordinated polymeric
g=2.0324
400
3
+
1
00
200
300
Magnetic field (mT)
500
30
Fe clusters decreases. As the result, it is reasonable to conclude
3
+
3+
that isolated Fe ions change into polymeric Fe clusters with the
3
5
90
b
∆
J
B
increase of Fe/Ce molar ratio . To sum up: the results of XRD,
Raman and H -TPR in this work show, the copper, iron and ceria of
Cu/C existing in the form of CuO, Fe and CeO , respectively,
corresponding to the integrity of the Fe and CeO crystal
structure. However, the EPR results shows only few copper ions
could incorporate into the iron or ceria lattice in Cu/C catalysts,
2
80
70
60
50
40
2
1
0
0
1
F
x
2
O
3
2
2
O
3
2
0
1 x
F
due to the limitation of oxygen vacancies in the Ce-Fe support. On
the other hand, the appropriate Ce/Fe molar ratio can create more
oxygen vacancies, due to the formation of local nonequilibrium
All Fe
10:1
5:1
1:1
0.5:1
0.1:1
Fe/Ce Molar ratio
3
+
4+
solid solution CuO/C
1
F
x
and therefore, more Fe and Ce could be
1
8
6
4
2
0
00
0
2
+
substituted by Cu ions.
90
∆B
J
c
8
7
6
5
4
0
0
0
0
0
0
0
0
All Fe
10:1
5:1
1:1
0.5:1
0.1:1
Fe/Ce Molar ratio
Fig. 3 EPR spectra of the studied copper catalysts on Fe-doped ceria
supports (a). Composition dependence of line intensity and line width for g ≈
4
.3 (b) and g ≈ 2.0-2.3 (c)
Fig. 4 depicted the H
2
-TPR profiles for catalysts. The TPR
consumption, spanning the
ranges 100−270, 270−500, and 500−900°C, associated with a
profiles consist of three regions of H
2
2
3, 43, 48
reduction of CuO
x
, Fe
2
O
3
, FeO and/or CeO
2
, respectively
.
Cu/Ce catalyst shows reduction peaks of CuO at 205, 241 and 296
°
C, respectively, which indicated CuO fine dispersed in the CeO
2
4
9
surface . While Fe was introduced into Cu/Ce
1
Fe
x
catalysts, the TPR
profiles for Cu/Ce became more complex. In the case of
Cu/Ce Fe catalyst, there are two peaks of CuO at 160 and 192 °C,
1
0.05
This journal is © The Royal Society of Chemistry 2018
J. Name., 2018, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Catalysis Science & Technology
Page 6 of 12
View Article Online
DOI: 10.1039/C8CY00709H
ARTICLE
Journal Name
respectively, and a new peak appear at 523°C. Fisrtly, Fe O coverts oxygen, which is unstable structures and led to the copper species
2
3
to Fe
00°C, secondly, the temperature ranges of 450 - 600°C for Cu/Ce easily incorporate into the cubic vacant sites of ceria when Ce/Fe
catalyst was not observed the reduction peaks of CeO . Hence, the molar is 1.Doping ceria with transition metals is a well-known way
peak at 523°C may be attributed to the reduction of the surface to modify the redox properties, enhance the oxygen mobility, and
3 4 3 4
O at 300 - 450 °C and Fe O coverts to FeO or Fe at 450 - more easily reduced. Therefore, the dispersed copper species more
9
2
2
3, 50, 51
oxygen or lattice oxygen, which indicates that the strong interaction improve the catalytic activity
. Physical and catalytic
properties of Fe -CeO binary systems can be modulated
2
O
3
2
between Fe with Ce and the doping of Fe changed the oxygen
structure of catalyst. While for Cu/Ce Fe0.5 catalyst, the reduction
peaks of CuO at 162 and 195°C, a new peak appear at 322°C,
attributed to the reduction of Fe and the broad peak in the
tenperature range of 450-650°C attributed to the reduction of
Fe and lattice oxygen, respective. The reduction peaks of CuO
continue decrease to 144 and 177°C for Cu/Ce Fe catalyst, while
the reduction peak of Fe also reduced to 315°C, and the
reduction peak of Fe and lattice oxygen has shift to lower
tenperature. Notably, the reduction peaks of CuO and Fe shift to
higher temperature when continue increase the Fe/Ce molar ratio.
For Cu/Ce Fe and Cu/Ce Fe catalysts, the reduction peaks of CuO Effect of Fe/Ce molar ratio on the activity of catalysts
depending on the Fe/Ce molar ratio and preparation method. These
observations may due to different interaction between copper and
ceria–iron. From the above findings, it was suggested that ceria–iron
mixed oxides with these molar ratios (1:1 and 1:0.5) readily
promoted the reduction of copper species interacting with ceria–iron
support. In summary, the difference in the reducibility of copper
oxide should be related to the different coordinate environments of
copper species, which is due to different surface structures of ceria
and iron. Maenwhile, different Fe/Ce mole ratio changed the lattice
oxygen of the catalyst structure.
1
2
O
3
3
O
4
1
1
2
O
3
3 4
O
2
O
3
1
5
1
10
increase to 183, 250°C and 191, 260°C, respectively. In the case of
Cu/Fe catalyst, only a reduction peak for CuO at 215°C, and the TPR
2
Fig. 5 showed the NO conversion and N selectivity with different
Fe/Ce molar ratio as a function of temprature. For all the prepared
catalysts, the NO reduction efficiency increased with
temperature(Fig.5a). The NO conversion of the catalyst supporter
with only iron or ceria reached approximately 91% and 80% at 200
2 3
peak of Fe O at 320°C. Compared with Cu-Ce and Cu-Fe, the
interaction of Fe and Ce exhibited complex reducibility of CuO. As
reported in the literatures, these reduction peaks of CuO can be
divided into different temperature range, which is related to the
°
C, respectively. The addition of ceria-iron mixed oxides significantly
34
dispersed CuO species on the surface of catalyst . The dispersed
improved the reactivity compared with the Cu/Fe and Cu/Ce
catalysts. In addition, the catalyst performance was depended on
CuO
Fe O
FeO
Cu/Fe
3
20
2
3
650
and
O
1 1
the Fe/Ce molar ratio in some extent. Overall, Cu/C F and gave the
215
higher NO conversion than other catalysts. Especially at 200 °C, the
difference in the activities was remarkable, following in this order:
Cu/C F > Cu/C F > Cu/C F > Cu/C F > Cu/C F > Cu/Fe> Cu/Ce,
645
3
32
Cu/C Fe
1
10
260
1
91
83
44177
364
1
1
1
0.5
1
5
1
0.1
1 10
Cu/C Fe
2
50
1
5
1
which should be related to the difference of interaction between
5
86
1
315
Cu/C Fe
1
1
iron and ceria. In view of N selectivity over these catalysts (Fig.
2
5
98
3
22
1
95
Cu/C Fe
5b), the remarkable difference could be observed below and above
1
0.5
162
1
2
92
100 °C. This might be resulted from the different active species at
160
523
Cu/C Fe
1
0.05
low and high temperatures. Additionally, the N selectivity followed
2
2
96
05 241
Cu/Ce
800
in the order: Cu/C1F0.1> Cu/C1F0.5> Cu/Ce > Cu/C F > Cu/C F >
1
5
1 1
1
00
200
300
400
500
600
700
Cu/C
1
F
10> Cu/Fe. Obvious, the order of the N
2
yield is not consistent
Temperature (°C)
2
-TPR profiles of the studied copper catalysts on Fe-doped ceria
with the NO conversion on Cu/C
1 x
F catalysts at 200 °C. The reasons
Fig. 4 H
supports
for these differences in the activity and N2 selectivity at low
temperatures are that: above all, the addtion amount of Fe should
copper species could incorporate into the cubic vacant sites of ceria
and form a five-coordinated surface structure with the capping
2
be the crucial factor, N selectivity are higher when the Fe/Ce molar
6
| J. Name., 2018, 00, 1-3
This journal is © The Royal Society of Chemistry 2018
Please do not adjust margins

Page 7 of 12
C Pa l tea al ys se i sd So c ni eo nt c ae d &j u Ts et cmh an rog l ion gs y
View Article Online
DOI: 10.1039/C8CY00709H
Journal Name
ARTICLE
ratio are less than or equal to 1 than the Fe/Ce molar ratio above 1, Cu/Fe and Cu/Ce catalysts, Cu catalysts on Fe-doped ceria show
indicating a small amount of iron additive can more effectively higher N selectivity, especially Cu/C 0.5 and Cu/C 0.1, indicated the
convert NO to N , the second, the specific surface area of the modification of ceria by incorporation of lower Fe amount is
catalysts should be taken into consideration, corresponding to beneficial for NO reduction by CO.
2
1
F
1
F
3
+
2
2
+
higher specific surface area helps to increase the effective Cu
activity sites(Table 1). We compared the N selectivity with the
specific surface area of the Cu/C catalysts, and found the N
2
In situ DRIFTs results of NO and CO co-adsorption with
2
Cu/C
1
F
1
catalyst
1
F
x
selectivity followed the same order with the specific surface area,
which indicated N2 selectivity was sensitive to the structure of
2
00°C
1389
1
50°C
2407
100°C
7
5°C
0°C
5
supports. Based on all the above results, Cu/C
1
F
1
catalyst displayed
30°C
1763
1046
the better performance in activity correspondingly, which should be
beneficial from the strong interaction among these components.
2077
2
176
1
00
a
Cu/Fe
80
60
40
20
0
Cu/C1F10
Cu/C1F5
Cu/C1F1
Cu/C1F0.5
Cu/C1F
0.1
2170
1616
2
404
2115 1904
2000
1766 1626
1025
1397
1406
13661264
Cu/Ce
1
400 1200
2400
2200
1800 16001200
1100
1000
NO: 0.08%
CO: 0.16%
ꢀ
1
Wavenumber(cm )
ꢀ1
GHSV: 30,000h
1 1
Fig. 6 In situ DRIFTs spectra of NO and CO co-adsorption with Cu/C F
catalyst with the catalysts from 30 °C to 200 °C
5
0
75
100
125
150
175
200
Temprature, °C
Fig. 6 shows in situ DRIFTs results of NO and CO co-adsorption
1
00
b
with Cu/C F catalyst as the temperature increasing from 30 to 200
1
1
NO: 0.08%
CO: 0.16%
°
2
C. The bridging bidentate nitrates display a NO symmetric
80
60
40
20
0
ꢀ1
GHSV: 30,000h
-1
Cu/Fe
vibration mode at 1025 cm . Some bands observed at 1264 and
Cu/C F
1
10
5
-
1
Cu/C F
1366 cm can be assigned to the progressive accumulation of
1
Cu/C F
1
1
-1
bidentate nitrates. These bands observed at 1347 - 1420 cm and
Cu/C F
1
0.5
0.1
Cu/C F
-1
1
1
600 - 1610 cm can be attributed to the vibration of the free
Cu/Ce
75
nitrate ion and bridge nitrates, respectively, the former indicated
that free nitrates acted as a stable inert species during the
5
0
100
125
150
175
200
5
2
Temprature, °C
interaction of NO + CO . The surface carbonate species appear at
Fig. 5 (a) NO conversion, (b) N
2
selectivity in CO + NO reaction over copper
-1
1
554 and 1567 cm , their intensities get stronger when the
-1
catalysts on Fe-doped ceria supports. (Conditions: GHSV = 30,000 h , 0.08%
temprature increased to 200 °C and to the progressive
accumulation of bidentate nitrates and carbonates. The band
NO, 0.16% ppm CO)
In addtion, compared with Cu/Fe, Cu/Ce sample has higher
-
1
observed at 1605 cm can be attributed to the N = O stretching
NO conversion efficiency and N
NCO species may plays important role for NO reduction by CO.
Notable, The N O selectivity also is important with catalytic activity
over Cu/C catalysts. The amount of N O over Cu/Fe was bigger
and the temperature in the corresponding maxium amount of N
2
selectivty, which suggests that the
−
1
mode. While the band at 1766 cm can be assigned to vibrational
modes of Cu-(NO) , indicating that Cu ions acted as the active site
2
2
for transforming nitrate oxides, which could promote the key step
for the NO + CO reaction, i.e., the dissociation of NO. The gaseous
1
F
x
2
2
O
-1
NO molecules display a weak band at 1904 cm . Concerning the
was higher than in the case of Cu/Ce sample , which disclose the
fact that Fe O phase is favored by N O formation. Compared with
-
1
spectral features in the region of 2000 - 2500 cm , these bands at
2
3
2
This journal is © The Royal Society of Chemistry 2018
J. Name., 2018, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
Catalysis Science & Technology
Page 8 of 12
View Article Online
DOI: 10.1039/C8CY00709H
ARTICLE
Journal Name
-
1
+
around 2114 and 2176 cm can be assigned to Cu - CO and
Cu/Fe
Cu/C
Cu/C F
1357
3
0°C
8
1
F
10
5
carbonyl associated with cerium ions, respectively , which were
O
N
O
N
1
Cu/C F
1397
1
1
2
+
Cu/C F
formed at room temperature via adsorbed CO with Cu , indicating
1
0.5
Cu/C F
1
0.1
CO2
Cu
Cu/Ce
1
766
that the reduced copper species worked at lower temperature. The
1610
600
1
1025
-
1
1904
regions of 2400 - 2411 cm assigned to the accumulation of
1264
carbonate. Interestingly, no
temperature, the formation of N
N
2
O
species appeared at all
2
207
O
2
O was in accordance with activity
N
1361
1
567
554
C
test results that low N
2
selectivity at low temperature and high at
1
53
217 62 114
2200 2000
high temperature on Cu/C F catalyst. Sugi et al. associated the
1
1
2
400
1800
1600
1200
1000
1400
1200
dependence of N
way: at the beginning of the reduction process, established the
adsorption equilibrium between NO and N O and N O is displaced
by NO before it is converted to N ; As the temperature rises, a part
2
O formation on the temperature by the following
ꢀ1
Wavenumbers/cm
Cu/Fe
1 10
Cu/C F
1357
1
00°C
O
N
O
N
1396
2
2
Cu/C F5
1
Cu/C F1
1
Cu/C
Cu/C F
F
2
1
0.5
0.1
CO2
Cu
1
Cu/Ce
1766
of the N
displacement by NO, which was evidenced by N
situ DRIFTs and the reaction mechanism was associated with the
formation of N O over Cu/C catalysts.
2
O formed on the catalyst will be reduced to N
2
before the
2
068
1025
1
624
2
selectivity and in
O
N
1
364
2
1 1
F
2207
C
In situ DRIFTs results of NO and CO adsorption with
Cu/CF catalysts
2400
2200
2000
1800
1600
1
1200
1000
1400
1200
ꢀ
Wavenumbers/cm
Cu/Fe
1358
1399
150°C
Cu/C F
1
10
5
Cu/C F
1
O
N
O
N
=
=
Cu/C1F1
Cu/C1F0.5
CO2
Cu/C
1
F
0.1
Cu/Ce
Cu
766
1
1
365
1399
1400
1200
2
400
2200
2000
1800
1600
1200
1000
ꢀ1
Wavenumbers/cm
Cu/Fe
Cu/C1F10
200°C
1399
1360
Cu/C1F
Cu/C1F1
5
O
N
O
N
CO2
Cu/C1F
0.5
Cu/C1F0.1
Cu/Ce
1
766Cu
1
358
1
399
2400
2200
2000
1800
1600 1200
1000
1400
1200
ꢀ
1
Wavenumbers/cm
1 x
Fig. 7 In situ DRIFTs spectra of NO and CO co-adsorption with Cu/C F
catalyst with the catalysts from 25 °C to 200 °C
8
| J. Name., 2018, 00, 1-3
This journal is © The Royal Society of Chemistry 2018
Please do not adjust margins

Page 9 of 12
C Pa l tea al ys se i sd So c ni eo nt c ae d &j u Ts et cmh an rog l ion gs y
View Article Online
DOI: 10.1039/C8CY00709H
Journal Name
ARTICLE
In order to clear the role of Fe addition for NO reduction by oxide species, as an intermediate of NO reduction by CO, appeared
-1
14
CO over these catalysts, in situ DRIFTS of NO and CO co-adsorption at around 2230 cm at rich-ceria catalysts. Daturi et al suggest
for these catalysts are collected at different Fe/Ce molar ratio with that the adsorption equilibrium between NO and N O is established
different temperatures, and the corresponding results are displayed at the beginning of the reduction process, then N O is displaced by
in Fig.7. For Cu/Ce sample at 30 °C(Fig.7a), except for similar bands NO before it is converted to N ; as the temperature is raised, a part
2
2
2
-
1
of Cu/C
1 1 2 2
F sample. a new bands observed at 2207 cm can be of the N O formed on the catalyst will be reduced to N before the
assigned to the generation of intermediate isocyanates (NCO) displacement by NO, which indicated the adsorption of NO is
5
4
2
species , which indicated that copper plays an important role in stronger than that of N O. Additional, the addtion of Fe obvious
the generation of oxygen vacancies on the basis of the generatetion enhanced the intension of NO adsorbed, in other words, the
mechanism of NCO in a significantly lower temperature range, addtion of iron promoted the adsorption of NO and the reduction
2
+
which involving the dissociation of NO, followed by the reaction of copper oxide, the latter as the receptor of adsorbed CO. Cu ions
+
between the N atoms lying on the surface with the CO molecules also acted as NO adsorption sites, while Cu ions acted as recipients
5
6
and generate NCO species. However, with the introduction of Fe of the O atoms produced through the dissociation of NO .
and the increase of Fe/Ce molar ratio, the NCO species disappear Therefore, rich-iron smples ensured an inhibition of the oxidation of
gradually, especially Cu/Fe sample. The reason is that the role of CO by increased NO partial pressures because of the competitive
5
4
copper for NO dissociation is well known and the catalysts of rich- adsorption of NO and CO , which correspond to the NO reduction
cerium have a higher effect in promotes NO desorption as N
2
at efficiency of Cu/Ce and Cu/Fe catalysts(Fig.3a).
55
much lower temperatures than ceria-free catalysts . In addtion,
Possible reaction mechanism
free nitrate ion gradually shifted from 1395 and 1361 to 1397 and
-
1
1
359 cm for Cu/Ce and Cu/Fe, indicated that the differences for
In general, the dissociation of NO is the crucial step for NO
removal by CO, and abundant oxygen vacancies can activate the N–
2
+
3+
NO adsorption on Cu and Fe , respectively. That bands assigned
to the progressive accumulation of NO strengthen with the increase
of Fe/Ce molar ratio, indicated the adsorption bond energy on Fe
stronger than Ce, which suggested that the rich-iron phase had the
greater ability to accelerate the NO desorption or/and rapid change
in valence states of copper than rich-ceria during the reaction
process.
5
7
O bond to promote this dissociation . In our case, the different
reducibility over Cu/CF catalysts possibly originated from their
different surface structures, which corresponded to the copper
5
4
species with different coordinated environments . Combining with
the above results and conclusion, the highly dispersed copper oxide
was the active species in NO + CO reaction. When exposing the
Cu/Ce catalyst to CO and NO mixture gases, the CO molecules
Further increasing the temperature to 100, 150 and 200
4
+
2+
preferred to adsorb on Ce sites rather than Cu sites, while the NO
°
C(Fig.7b,7c and 7d), respectively, the adsorbed free nitrate ion
2+
4+
molecules preferred to adsorb on Cu sites rather than Ce sites.
The scheme includes NO dissociation as two oxygen atoms from two NO
molecules fill oxygen vacancies re-oxidizing the reduced ceria surface,
-
1
specie (1396 cm ) are steadily strengthen with the increase of the
Fe/Ce molar ratio, indicated that iron adsorption sites possess
stronger absorption ability of NO. The NCO species still exist in
1
4
while the nitrogen atoms recombine giving rise to a N molecule . The
2
several catalysts, such as Cu/Ce, Cu/C
1 1
F0.1, Cu/C F0.5. In addition, the
4
+
CO species adsorbed on Ce can combine with O radicals from the
-1
decrease in peak intensity at 2207 cm may be due to
dissociation of NO on the adjacent oxygen vacancy to form CO
2
. With the
1
3
decomposition of isocyanates at elevated temperatures ,
suggesting NCO species are unstable. Especially above 150 °C, the
peak disappear completely. Which is inconsistent with the xiao’s
4
+
3+
3+
formation of oxygen vacancies, Ce is restored to Ce , while Ce has
4
+
better adsorption property of CO than Ce . Therefore, the NO
conversion efficiency and CO oxidization rate increases, along with the
1
3
results , obviously, the difference mainly derive from the lower
activity of Cu than Pt. It is interesting that the NCO species were not
observed in rich-iron catalysts and further revealed NO easier to
attach to the Fe. Simultaneously, some small weak peaks nitric
2
temperature rises. The N O was produced over Cu/Ce up to 100 °C.
Meanwhile, another scheme that isocyanates as the intermediates
in the CO + NO reaction has been proposed based on the above analysis.
This journal is © The Royal Society of Chemistry 2018
J. Name., 2018, 00, 1-3 | 9
Please do not adjust margins

Please do not adjust margins
Catalysis Science & Technology
Page 10 of 12
View Article Online
DOI: 10.1039/C8CY00709H
ARTICLE
Journal Name
First, the dissociation of NO on the oxygen vacancies of the copper The superabundant iron ensured an inhibition of the adsorption of
sites, followed by the reaction between the N atoms lying on the CO by increased NO partial pressures and the CO adsorption
3
+
2 3
surface with the CO molecules and generate NCO species. The diminishes. Especially for Cu/Fe O , Fe acts as the adsorption sites
2
+
+
unstable NCO species decompose quickly with the temperature goes of NO, while Cu /Cu acts as the adsorption sites of CO, which
up. However, the NCO species disappear completely when above 150 inhibited the formation of the NCO species based on the vulnerable
2
+
°
C, which means the reaction process convert the scheme to the first to reduced of Cu . Hence, the mechanism of NO reduction by CO
scheme ( N O as the intermediate). may accord with the first scheme ( N O as the intermediate). This
2
2
suggests that NO chemisorption is deeply influenced by the co-
existence of Fe and Ce. The cooperative activation of NO
+
3+
chemisorbed onto Cu and Fe would be a key step, although
further study should be needed to clarify the detailed reaction. To
further understand the remarkable enhancement of the catalytic
performance results from Fe/Ce molar ratio, the possible reaction
mechanism is illustrated in Fig.8
.
Conclusions
The work explored the effects of Ce/Fe molar ratio on the
physicochemical properties of Cu/CF catalysts. It was found that
copper oxide dispersed on Ce-Fe supports exhibited the different
reducibility. The difference of Fe/Ce molar ratio reflect on the
support’s structure. Meanwhile, the ceria modification by
3
+
incorporation of lower Fe amount is beneficial especially for NO
conversion and the selectivity to N as compared with the pure ceria
2
and iron-rich ones. These were resulted from the difference in the
strong interaction among the copper, iron–ceria support.
Additionally, DRIFT and activity tests results suggested that a
dissociation mechanism for the CO + NO reaction was proposed
+
over Cu/CF. The NO species was further dissociated to
Fig. 8 Possible reaction mechanisms of NO reduction by CO over
copper catalysts on Fe-doped ceria supports with difference Ce/Fe
molar ratio
intermediate N O is the dominant reaction step. Nevertheless,
2
there exists another mechanism that the interaction of
chemisorbed NO and gaseous CO further to form the NCO
3
+
When the Fe was introduced, the incorporation of lower Fe
1 x
intermediate orignating over Cu/C F (x=0, 0.1 and 0.5). The
2
amount does not destroy the crystal structure of CeO .
addition of Fe obvious enhanced the intension of NO adsorbed and
rich-iron samples inhibit the the oxidation of CO by increased NO
adsorbed.
Simultaneously, the addtion of iron promoted the adsorption of NO
and supplements inadequate the adsorption of NO based on a small
amount of Cu activity sites, and then afford the O atoms produced
through the dissociation of NO, and then, simultaneous, the rest of
the N atoms combined with the adsorption of NO and to form N O, Conflicts of interest
2
There are no conflicts to declare.
eventually raising the reaction process. Thus, the addtion of iron
promoted the NO reduction by CO. However, the crystal structure
of rich-iron smples is dominated by the crystal structure of Fe
2
O
3
.
Acknowledgements
1
0 | J. Name., 2018, 00, 1-3
This journal is © The Royal Society of Chemistry 2018
Please do not adjust margins

Page 11 of 12
C Pa l tea al ys se i sd So c ni eo nt c ae d &j u Ts et cmh an rog l ion gs y
View Article Online
DOI: 10.1039/C8CY00709H
Journal Name
ARTICLE
The authors thank the National Natural Science Foundation of 17 P. C. Caldas, J. M. R. Gallo, A. Lopez-Castillo, D. Zanchet and
China (NO. 51776113 and NO. 51776114), Natural Science
Foundation of Shandong Province (NO. ZR2017MEE035), the Key
R&D Program Funds of Shandong Province (NO. 2017GSF17122),
and the Foundation of Shandong University for Young Scholar’s
Future Plan (NO. 2017WLJH29) for the financial support.
J. M. C. Bueno, ACS. Catal, 2017, 7, 2419-2424.
18 R. Zhang, W. Y. Teoh, R. Amal, B. Chen and S. Kaliaguine, J.
Catal, 2010, 272, 210-219.
19 G. Zafiris and R. Gorte, J. Catal, 1993, 139, 561-567.
20 X. Wu, F. Lin, D. Weng and J. Li, Catal. Commun, 2008,
428-2432.
9,
2
2
1 M. Mrad, D. Hammoud, C. Gennequin, A. Aboukaïs and E.
Abi-Aad, Appl. Catal. A: Gen, 2014, 471, 84-90.
Notes and references
1
2
3
4
C. Ge, L. Liu, Z. Liu, X. Yao, Y. Cao, C. Tang, F. Gao and L.
2
2 X. Yao, Y. Xiong, W. Zou, L. Zhang, S. Wu, X. Dong, F. Gao, Y.
Deng, C. Tang and Z. Chen, Appl. Catal. B, 2014, 144, 152-
Dong, Catal. Commun, 2014, 51, 95-99.
Q. Yu, X. Yao, H. Zhang, F. Gao and L. Dong, Appl. Catal. A-
Gen, 2012, 423, 42-51.
1
65.
2
2
2
2
2
2
3 Z. Liu, Z. Wu, X. Peng, A. Binder, S. Chai and S. Dai, J. Phys.
Chem. C, 2014, 118, 27870-27877.
L. Liu, Y. Chen, L. Dong, J. Zhu, H. Wan, B. Liu, B. Zhao, H. Zhu,
K. Sun and L. Dong, Appl. Catal., B, 2009, 90, 105-114.
C. A. Roberts, D. Prieto-Centurion, Y. Nagai, Y. F. Nishimura,
R. D. Desautels, J. van Lierop, P. T. Fanson and J. M.
Notestein, J. Phys. Chem. C, 2015, 119, 4224-4234.
C. Sun, Y. Tang, F. Gao, J. Sun, K. Ma, C. Tang and L. Dong,
Phys. Chem. Chem. Phys, 2015, 17, 15996-16006.
H. Simon, A. Reff, B. Wells, J. Xing and N. Frank, Environ Sci.
Tech, 2014, 49, 186-195.
4 X. Li, X. Li, J. Li and J. Hao, J. Hazard. Mater, 2016, 318, 615-
6
22.
5 H. Zhang, A. Zhu, X. Wang, Y. Wang and C. Shi, Catal.
Commun, 2007, , 612-618.
8
5
6
7
8
9
1
1
1
1
1
6 J. Chen, J. Zhu, C. Chen, Y. Zhan, Y. Cao, X. Lin and Q. Zheng,
Catal. Lett, 2009, 130, 254-260.
7 Z. Yang, Y. Wei, Z. Fu, Z. Lu and K. Hermansson, Surf. Sci,
2
008, 602, 1199-1206.
X. Cheng, X. Zhang, M. Zhang, P. Sun, Z. Wang and C. Ma,
Chem. Eng. J, 2017, 307, 24-40.
8 E. V. Frolova, M. Ivanovskaya, V. Sadykov, G. Alikina, A.
Lukashevich and S. Neophytides, Prog. Solid. State Ch, 2005,
X. Cheng, M. Zhang, P. Sun, L. Wang, Z. Wang and C. Ma,
Green. Chem, 2016.
33, 317-325.
2
3
3
9 Q. Yu, X. Wu, X. Yao, B. Liu, F. Gao, J. Wang and L. Dong,
Catal. Commun, 2011, 12, 1311-1317.
J. Wang, X. Wang, J. Zhu, J. Wang and M. Shen, Environ Sci.
Tech, 2015, 49, 7965-7973.
0 H. Zhu, M. Shen, F. Gao, Y. Kong, L. Dong, Y. Chen, C. Jian and
0 D. Rainer, M. Koranne, S. Vesecky and D. Goodman, The J.
Phys. Chem. B, 1997, 101, 10769-10774.
Z. Liu, Catal Commun, 2004, 5, 453-456.
1 F. J. Pérez-Alonso, M. López Granados, M. Ojeda, P. Terreros,
S. Rojas, T. Herranz, J. L. G. Fierro, M. Gracia and J. R.
Gancedo, Chem. Mater, 2005, 17, 2329-2339.
1 M. Li, X. Wu, Y. Cao, S. Liu, D. Weng and R. Ran, J. Colloid.
Interf. Sci, 2013, 408, 157-163.
2 H.-o. Zhu, J.-R. Kim and S.-K. Ihm, Appl. Catal. B, 2009, 86
,
3
3
2 A. Trovarelli, Comment. Inorg. Chem, 1999, 20, 263-284.
3 N. Miki, Y. Kunihiko and M. Yuichi, B. Chem. Soc. Jpn, 1981,
8
7-92.
3 P. Xiao, R. C. Davis, X. Ouyang, J. Li, A. Thomas, S. L. Scott and
J. Zhu, Catal. Commun, 2014, 50, 69-72.
54, 975-979.
3
3
3
4 Q. Yu, L. Liu, L. Dong, D. Li, B. Liu, F. Gao, K. Sun, L. Dong and
Y. Chen, Appl. Catal. B, 2010, 96, 350-360.
4 L. Ilieva, G. Pantaleo, N. Velinov, T. Tabakova, P. Petrova, I.
Ivanov, G. Avdeev, D. Paneva and A. M. Venezia, Appl. Catal.
B, 2015, 174–175, 176-184.
5 L. Dong, B. Zhang, C. Tang, B. Li, L. Zhou, F. Gong, B. Sun, F.
Gao, L. Dong and Y. Chen, Catal. Sci. Tech, 2014, 4, 482-493.
1
1
5 M. Haneda and H. Hamada, J. Catal, 2010, 273, 39-49.
6 Q. Shen, G. Lu, C. Du, Y. Guo, Y. Wang, Y. Guo and X. Gong,
Chem. Eng. J, 2013, 218, 164-172.
6 D. Li, Q. Yu, S. S. Li, H. Q. Wan, L. J. Liu, L. Qi, B. Liu, F. Gao, L.
Dong and Y. Chen, Chem–Eur. J, 2011, 17, 5668-5679.
This journal is © The Royal Society of Chemistry 2018
J. Name., 2018, 00, 1-3 | 11
Please do not adjust margins

Please do not adjust margins
Catalysis Science & Technology
Page 12 of 12
View Article Online
DOI: 10.1039/C8CY00709H
ARTICLE
Journal Name
3
3
3
4
4
4
4
4
4
7 W. Wang, Q. Zhu, Q. Dai and X. Wang, Chem. Eng. J 2017, 57 T. Boningari, S. M. Pavani, P. R. Ettireddy, S. S. C. Chuang and
07, 1037-1046. P. G. Smirniotis, Mol. Catal, 2017.
3
8 K. N. Rao, P. Venkataswamy and B. M. Reddy, Ind. Eng.
Chem. Res, 2011, 50, 11960-11969.
9 L. Qi, Q. Yu, Y. Dai, C. Tang, L. Liu, H. Zhang, F. Gao, L. Dong
and Y. Chen, Appl. Catal. B, 2012, 119, 308-320.
0 M. Fernandez-Garcia, A. Martinez-Arias, J. Hanson and J.
Rodriguez, Chem. Rev, 2004, 104, 4063-4104.
1 K. C. K. Lai and I. M. C. Lo, Environ. Sci. Techn, 2008, 42
238-1244.
2 X. Zhu, K. Li, Y. Wei, H. Wang and L. Sun, Energy. Fuel, 2014,
, 754-760.
3 L. Liu, Z. Yao, B. Liu and L. Dong, Journal of Catalysis, 2010,
75, 45-60.
,
1
28
2
4 S. P. Singh, R. P. S. Chakradhar, J. L. Rao and B. Karmakar, J.
Alloy. Compd, 2010, 493, 256-262.
5 R. S. Muralidhara, C. R. Kesavulu, J. L. Rao, R. V. Anavekar
and R. P. S. Chakradhar, J. Phy. Chem. Solids, 2010, 71, 1651-
1
655.
4
6 R. A. Eichel, H. Meštrić, K. P. Dinse, A. Ozarowski, J. van Tol,
L. C. Brunel, H. Kungl and M. J. Hoffmann, Magn. Reson.
Chem, 2005, 43
.
4
4
4
5
5
5
5
5
5
5
7 R. Stefan, P. Pascuta, A. Popa, O. Raita, E. Indrea and E.
Culea, J. Phys. Chem. Solids, 2012, 73, 221-226.
8 Z. Qu, L. Miao, H. Wang and Q. Fu, Chem. Commun, 2015, 51
56-958.
9 G. Avgouropoulos and T. Ioannides, Appl. Catal. A-Gen, 2003,
44, 155-167.
,
9
2
0 A. Martínez-Arias, D. Gamarra, M. Fernández-García, A.
Hornés and C. Belver, Top. Catal, 2009, 52, 1425-1432.
1 Z. Liu, R. Zhou and X. Zheng, J. Mol. Catal. A-Chem, 2007,
2
67, 137-142.
2 L. Wang, X. Cheng, Z. Wang, C. Ma and Y. Qin, Appl. Catal. B,
017, 201, 636-651.
3 Y. Sugi, N. Todo and T. Sato, B. Chem. Soc. Jpn, 1975, 48, 337-
38.
4 Y. Xiong, X. Yao, C. Tang, L. Zhang, Y. Cao, Y. Deng, F. Gao and
L. Dong, Catal. Sci. Tech, 2014, , 4416-4425.
2
3
4
5 Y. Xiaojiang, Y. XIONG, S. Jingfang, G. Fei, D. Yu, T. Changjin
and D. Lin, J. Rare. Earth, 2014, 32, 131-138.
6 V. I. Pârvulescu, P. Grange and B. Delmon, Catal. Today,
1
998, 46, 233-316.
1
2 | J. Name., 2018, 00, 1-3
This journal is © The Royal Society of Chemistry 2018
Please do not adjust margins