Highly efficient formaldehyde elimination over meso-structured M/CeO2 (M = Pd, Pt, Au and Ag) catalyst under ambient conditions

Article abstract of DOI:10.1039/c5ra04928h

A series of mesoporous CeO₂ supported noble metal (Pt, Pd, Au and Ag) catalysts, fabricated through a facial pyrolysis and in situ reduction protocol, were used for formaldehyde elimination under ambient conditions. The materials possessed relatively high specific surface area and uniformly dispersed noble metal nanoparticles, and showed very high catalytic activities for formaldehyde oxidation. For about 1 wt% noble metal loaded materials, Pt/CeO₂, Pd/CeO₂ and Au/CeO₂ catalysts could completely catalytically oxidize HCHO at room temperature. Even for the low activity Ag/CeO₂ catalyst, the complete conversion temperature could reach 100°C, much lower than that reported before. Such good catalytic properties could be attributed to the strong synergetic interaction between the active component and CeO₂ nano-crystalline aggregated support. The reaction mechanism over the noble-metal/CeO₂ catalyst was also discussed through in situ DRIFTS analysis.

Full text of DOI:10.1039/c5ra04928h

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Highly efficient formaldehyde elimination over
meso-structured M/CeO2 (M ¼ Pd, Pt, Au and Ag)
catalyst under ambient conditions†
Cite this: RSC Adv., 2015, 5, 36428
*
Gengnan Li and Liang Li
A series of mesoporous CeO2 supported noble metal (Pt, Pd, Au and Ag) catalysts, fabricated through a facial
pyrolysis and in situ reduction protocol, were used for formaldehyde elimination under ambient conditions.
The materials possessed relatively high specific surface area and uniformly dispersed noble metal
nanoparticles, and showed very high catalytic activities for formaldehyde oxidation. For about 1 wt%
noble metal loaded materials, Pt/CeO2, Pd/CeO2 and Au/CeO2 catalysts could completely catalytically
oxidize HCHO at room temperature. Even for the low activity Ag/CeO2 catalyst, the complete
conversion temperature could reach 100 ꢀC, much lower than that reported before. Such good catalytic
properties could be attributed to the strong synergetic interaction between the active component and
CeO2 nano-crystalline aggregated support. The reaction mechanism over the noble-metal/CeO2 catalyst
was also discussed through in situ DRIFTS analysis.
Received 20th March 2015
Accepted 15th April 2015
DOI: 10.1039/c5ra04928h
www.rsc.org/advances
supported noble-metal materials are the promising catalysts for
many oxidation catalysis process, including the oxidation of
formaldehyde.7–9,20–25 Zhang et al. developed a three-dimensionally
1. Introduction
Formaldehyde, one of the most noxious indoor gaseous pollut-
ants, is commonly emitted from decorative and building mate-
rials. Long-term exposure may cause serious problems to human
health even under a few ppm concentration. Research for the
complete elimination of formaldehyde is thus of great impor-
tance for both practical application and fundamental research.1,2
Although various methods have been proposed so far to remove
this kind of indoor pollutant, they all can be classied as the
adsorption and the catalytic oxidation strategy.3–18 In comparison,
catalytic oxidation under ambient condition is much attractive
way to remove formaldehyde, because this process could not only
constantly convert formaldehyde to non-harmful carbon dioxide
and water molecules with low consumption of energy, but also
absolutely overcome the disadvantage of the limited removal
capacities of absorbent during absorption process.2,19
ordered macro-structured Au/CeO2 catalyst, and the complete
oxidation of HCHO could be obtained at 75 ꢀC.7 Zhu et al. found
that Au/CeO2 prepared by deposition–precipitation method could
achieve complete HCHO conversion into CO2 and H2O at room
temperature.8 Ma et al. reported recently that Ag/CeO2 nano-
sphere prepared by hydrothermal and impregnation method
could completely eliminate HCHO above 110 ꢀC under relatively
high space velocity.9 All above literatures clearly show that the
catalytic activity of the CeO2 supported noble metal catalyst is
mainly related to the surface area, highly dispersed noble metal
species and the existence form of the active component.
Herein, we present a simple and versatile protocol to prepare
meso-structured noble metal/CeO2 catalysts for formaldehyde
elimination under ambient condition. Nano-crystalline inter-
sectioned mesoporous CeO2 support was directly pyrolysis
from oxalate and noble metal nanoparticles was conned
through in situ reduction. Compared with other method, this
strategy is simple and time-saving. The resulting materials
process high specic surface area and the noble nanoparticles
could be highly deposited in/on the CeO2 nano-crystalline
support, and thus possess much high catalytic activities for
formaldehyde oxidation.
Cerium oxide, especially its nano-crystalline, always possesses
large amount of oxygen vacancies and thus shows excellent
oxygen storage and release properties, which are also critical
factors for oxidation process. When combined with noble metal,
benetting from the strong synergetic interaction, signicantly
enhanced activity could be achieved. It has been proved that CeO2
Key Laboratory for Ultrane Materials of Ministry of Education, School of Materials
Science and Engineering, East China University of Science and Technology, Meilong
Road 130, Shanghai, China. E-mail: liliang@ecust.edu.cn
2. Experimental
2.1 Materials preparation
† Electronic supplementary information (ESI) available: The XRD patterns of
Ce2(C2O4)3$2H2O precursor, the XRD pattern and TEM image of CeO2 support
and the comparison of the catalyst performance over different noble-metal
supported catalysts for formaldehyde oxidation reported previously. See DOI:
10.1039/c5ra04928h
10 mmol Ce(NO3)3$6H2O was rst dissolved into 100 ml
aqueous solution, 30 ml 1 M oxalate was slowly added under
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vigorous stirring. The precipitate was ltered, washed with
deionized water and dried at 60 ꢀC. The mesoporous CeO2
material was nally obtained aer calcinated at 350 ꢀC for 2 h.
A series of mesoporous CeO2 supported noble mental cata-
lysts were synthesized through an improved wet impregnation
procedure. For Pd/CeO2 catalyst, 0.5 g above synthesized mes-
oporous CeO2 material was added in 25 ml aqueous solution
containing calculated content of Na2PdCl4. Aer stirred for 2 h,
100 ml 0.1 M hydrazine hydrate was slowly added and stirred for
12 h successively. The resulting solid mass was collected
½HCHOꢂ ꢁ ½HCHOꢂ
in
out
HCHO conversion ð%Þ ¼
ꢃ 100%
½HCHOꢂ
in
where [HCHO]in and [HCHO]out represent the HCHO concen-
tration in inlet and outlet gas, respectively.
3. Results and discussion
3.1 Catalytic oxidation performance of different noble-
metal/CeO2 catalysts
ꢀ
through centrifugation, washed with water and dried at 60 C
Fig. 1 depicts the catalytic activities of HCHO oxidation over
different noble metal/CeO2 catalysts. It clearly shows that the as
prepared Pd, Pt and Au loaded CeO2 catalysts all process much
higher catalytic activity for HCHO oxidation at ambient
temperature. Under 600 ppm HCHO concentration and the gas
hourly space velocities (GHSV) of 120 000 hꢁ1, all the HCHO
could be complete eliminated over Pt/CeO2 catalyst even the
reaction temperature as lower as 20 ꢀC. Comparatively,
although the Pd/CeO2 and Au/CeO2 catalysts show a slight
decreased catalytic activities, the HCHO still can be totally
converted below the temperature of 22 ꢀC and 28 ꢀC, respec-
tively. Even for the traditional lower-active Ag catalyst, the as
prepared Ag/CeO2 material could complete oxidize HCHO at
100 ꢀC and 95% HCHO conversion could be achieved at 60 ꢀC,
much lower than reported before.9 Meanwhile, to understand
the intrinsically catalytic properties, the turn over frequency
(TOF) of the catalysts were calculated and showed the much
higher values for HCHO oxidation process when compared with
related research results (ESI†).
for 24 h. The other noble metal/CeO2 materials were synthe-
sized similar with that of Pd/CeO2.
2.2 Characterization
Powder X-ray diffraction (XRD) patterns were recorded on a
Bruker D8 Focus powder diffract meter with graphite mono-
chromatized Cu Ka radiation (l ¼ 0.15405 nm) operated at
40 kV. Nitrogen adsorption and desorption isotherms were
measured on a Micromeritics ASAP 2020M analyzer at liquid
nitrogen temperature (77 K). Prior to the measurements, the
samples were degassed at 423 K in vacuum for 6 h. The specic
surface area and pore size distribution were calculated using
the Brunauer–Emmett–Teller (BET) and Barrett–Joyner–
Halenda (BJH) methods, respectively. Transmission Electron
Microscopy (TEM) observations were performed on a eld
emission JEM-2100 (JEOL) electron microscope operated at
300 kV equipped with a Gatan-666 electron energy loss spec-
trometer and energy dispersive X-ray spectrometer. XPS (X-ray
photoelectron spectroscopy) signals were collected on a VG
Micro MK II instrument using monochromatic Al Ka X-ray at
1486.6 eV operated at 200 W. All the elemental binding energies
were referenced to the C (1s) line situated at 284.6 eV. Infrared
spectra were recorded by a FTIR spectrometer (Nicolet iS10)
equipped with a MCT detector. The sample cell was tted with
ZnSe windows. The sample was exposed to the corresponding
reaction stream (60 ml minꢁ1). The DRIFT spectra obtained at
25 ꢀC with a solution of 4 cmꢁ1 and 50 scans. Typical gas
mixture was 600 ppm HCHO, 20.0 vol% O2 balanced with N2.
Besides, the effect of GHSV to HCHO conversion over
different catalysts are also presented in Fig. 1. For the highest
active catalyst Pt/CeO2 material, even the GHSV increase to
2.3 Catalytic properties
The oxidation of HCHO was performed in a quartz tubular (i.d. ¼
6 mm) xed-bed reactor under atmospheric pressure. 50 mg of
catalyst was loaded in the rector and the reaction temperature
was monitored by a thermo-couple placed in the middle of the
catalyst bed. A gas mixture containing 600 ppm HCHO and
20.0 vol% O2 balanced by N2 was introduced as reactants.
Gaseous HCHO was generated by following air through formalin
in a saturator kept at 0 ꢀC. The HCHO was analyzed by an online
GC equipped with a FID detector. The gaseous products passed
through a methanization converter lled with Ni catalyst and all
the carbon-containing products were converted to methane
before they went to the FID detector to ensure a high intensity of
signal. In a typical runs, the reaction data were obtained aer
HCHO was performed for 30 min to achieve steady state. The
HCHO conversion was calculated as follows:
Fig. 1 Catalytic oxidation of HCHO over different noble metal/CeO2
catalysts: Pd/CeO2 (A), Pt/CeO2 (B), Au/CeO2 (C) and Ag/CeO2 (D).
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360 000 hꢁ1, HCHO still can be totally converted at the reduction process has been proved to be effective method for
temperature of 60 ꢀC and 70% conversion could be achieved at fabrication highly dispersed noble metal nanoparticles on CeO2
20 ꢀC. All these results appear that the noble-mental/CeO2 support.
catalysts prepared through pyrolysis and in situ reduction
To obtain detailed morphology and noble meal distribution,
protocol are all among the most active catalysts reported in the the materials were examined with transmission electron
literatures (ESI†).
microscopy (TEM). Fig. 3 shows the TEM results of the meso-
structured CeO2 support and noble metal loaded catalysts. It
clearly shows that the meso-structured CeO2 support was
composed by aggregation of nano-crystalline of several nano-
meters. Pores are randomly but homogeneously distributed
within the whole particle, which are produced by a great
quantity of gases slowly released from the oxalate precursor
leaving behind numerous voids during thermal decomposition
process. Aer impregnation, the noble metal ion species was
transferred into the porous structure of CeO2. The following
in situ reduction results in noble metal/CeO2 material with
noble metal nanoparticles being homogeneously dispersed
in/on the mesoporous support. No large noble metal particle
can be found in the TEM images. In addition, the selected area
electron diffraction (SAED) patterns from the same area are also
presented in the TEM images. The well-dened diffraction rings
for CeO2 can be found in all the samples. However, the relative
faint diffraction ring of noble metals may be related to their
small loading amount. These results are in good agreement
with above XRD analysis.
3.2 Physicochemical properties of the catalysts
Highly dispersed noble metal species and high specic surface
area CeO2 support with large amount of oxygen vacancies are
two key factors of highly active noble-metal/CeO2 catalyst for
HCHO oxidation under ambient conditions. In the experiment,
the nano-crystalline inter-sectioned mesoporous CeO2 support
was obtained through direct pyrolysis of oxalate, and the noble
metal component was transferred into the porous structure
through wet impregnation and in situ reduction strategy. The
actual contents of Pd, Pt, Au and Ag loaded in the meso-
structured CeO2 materials were determined by the ICP-AES
technique to be 0.78, 1.00, 0.92 and 0.98 wt%, respectively.
The result shows that almost all of the noble metal species in
the aqueous solution have been deposited into/on the meso-
structured CeO2 support.
The crystalline structure of resulting noble-metal/CeO2
materials were characterized by X-ray diffraction (XRD) analysis.
Aer calcination, the precursor oxalate lost its original crystal-
line structure and turned to CeO2 (PDF card no. 81-0792). No
additional diffraction peaks from impurities were detected.
Sequential impregnation and in situ reduction process did not
affect the crystalline structure of the CeO2 support. Fig. 2
presents the XRD patterns of the obtained noble metal/CeO2
catalysts with different noble mental of Pd, Pt, Au and Ag,
respectively. For Pd/CeO2 and Pt/CeO2 materials, except that for
CeO2 support, there is not any additional diffraction peaks for
metallic Pd or Pt. This may be attribute to the small loading
amount of noble metals or the highly dispersed Pd and Pt
species. On the other hand, a peak emerged at 2q ¼ 38ꢀ for
Au/CeO2 and Ag/CeO2 catalysts which can be identied as (111)
diffraction band of face-centered cubic structure Au and Ag. It
should be note that all the characteristic peaks of metallic Au
and Ag are broad and weak, and the particle sizes calculated
through Scherrer equation are all smaller than 3 nm. The in situ
Aer loaded with noble metal, the materials still possess
mesoporous structure. Impregnation and sequential in situ
reduction process did not affect the meso-structured nature of
the CeO2 support, as conrmed by the adsorption–desorption
isotherms of nitrogen analysis at 77 K (Fig. 4). In all the cases,
the typical Langmuir IV isotherms suggest the mesoporous
structure and the appearance of H3 hysteresis loops indicate the
Fig. 3 TEM images and corresponding select area diffraction patterns
Fig. 2 XRD patterns of 1 wt% noble metal/CeO2 catalysts: Pd/CeO2 of
1
wt% noble metal/CeO2 materials: Pd/CeO2 (a), Pt/CeO2
(a), Pt/CeO2 (b), Au/CeO2 (c) and Ag/CeO2 (d).
(b), Au/CeO2 (c) and Ag/CeO2 (d).
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formation of slit-like mesopore. Surprisingly, the specic
surface area and pore size of the samples show only limited
change aer loading of noble metals. These results demonstrate
that noble metal nanoparticles have been uniformly dispersed
and ungrowth during the deposition process, corresponding
well with the above XRD and TEM analysis.
The surface chemical states of the species for noble metal/
CeO2 catalysts were detected by X-ray photoelectron spectros-
copy (XPS). Fig. 5A depicts the similar Ce 3d XPS spectra of the
different noble metal/CeO2 catalysts which clearly show the
coexistence of Ce(III) and Ce(IV). Generally, the Ce 3d spectrum is
somewhat complicated and composed with two series of peaks:
3d5/2 with two very pronounced “shake-down” satellites and
3d3/2 with the same characteristic. The satellite peak associated
to the Ce 3d3/2 at 916.9 eV is the characteristic of the presence of
tetravalent Ce(IV). The appearance of signals located at about
903.5, 885.4, 898.9 and 880.9 eV, respectively, indicates the
existence of Ce(III), which may also use as an indicator for the
existence of oxygen vacancies.20,25–27 The high amount of Ce(III)
result in oxygen vacancies which could promote the oxygen
release and store and thus directly affect the catalytic perfor-
mance for HCHO oxidation. The O 1s XPS spectra of the cata-
lysts can be resolved into three peaks as shown in Fig. 5B. The
main contribution at 529.1 eV is the characteristic peak of
metal–oxygen due to the lattice oxygen (Olat), and that at
530.9 and 532.0 eV are usually associated with the surface
chemisorbed oxygen species.25 In addition, the Pd 3d, Pt 4f, Au
4f and Ag 3d XPS spectrum for the different noble metal/CeO2
catalysts are also presented in the Fig. 5C–F, respectively.8,13,14,25
From the corresponding contents of the different noble metal
species (ESI†), it can be found that almost all of the noble metal
Fig. 5 The XPS spectra of CeO2 support (a) and noble metal/CeO2
catalysts. Pd/CeO2 (b), Pt/CeO2 (c), Au/CeO2 (d) and Ag/CeO2 (e).
element exist as metallic in noble metal/CeO2 catalyst. This may
be concerned with the synthesized method in the experiment
(post-graing and reduction).
Fig. 6 shows the similar Raman spectra for the CeO2 and
noble metal loaded CeO2 samples within 300–600 cmꢁ1 range.
The main bands centred at about 460 cmꢁ1 are typical of CeO2
vibrations (the triply degenerated TO mode).28,29 Generally, the
intensity of the Raman peaks is related to various parameters of
the physicochemical structure of the materials, while the full
width at half maximum (FWHM) is associated with the crys-
tallite size and/or the amount of oxygen vacancies.30,31 In our
experiment, the CeO2 supports are all from the decomposition
of the oxalate precursor, and it has been proved that the
sequential impregnation and in situ reduction process do not
affect the crystal size of the CeO2 support. Thus, a larger FWHM
means a high amount of oxygen vacancies in the CeO2 structure.
For noble metal/CeO2 materials, the FWHM values are all
increased when loaded with noble metal, suggesting that the
increased concentration of oxygen vacancies. As reported in
literature, the oxygen vacancies play a very important role in
oxidation reaction process. The high amount of oxygen
Fig. 4 N2 desorption–adsorption isotherms and pore distributions of
noble metal/CeO2 materials: Pd/CeO2 (a), Pt/CeO2 (b), Au/CeO2
(c) and Ag/CeO2 (d).
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were assigned to ns(C–H).8,11,32 In addition, a weak band appear-
ing at 2320 cmꢁ1 is the typical band of CO2. The immediately
emerged and gradually increasing of these spectra suggest that
the absorbed HCHO could be rapidly converts to format species
intermediates on Pd/CeO2 catalyst and then decomposed to CO2.
Interestingly, the Pt/CeO2, Au/CeO2 and Ag/CeO2 catalysts
showed the similar trend during HCHO oxidation process indi-
cating the almost the same oxidation mechanism.
3.4 Oxidation mechanism
Why as prepared noble metal/CeO2 show the much higher
catalytic activities for HCHO oxidation? The crystalline struc-
ture of the CeO2 and high dispersing of the active component
must be considered. In the present work, the CeO2 support was
fabricated from pyrolysis of oxalate precursor, and resulting
meso-structure were composed by aggregation of CeO2 nano-
crystalline which containing much more defect sites and thus
provides more oxygen vacancies that are able to absorb and
activate O2, as evidenced experimentally and theoretically.
Raman spectroscopies results also reveal that the noble metal
loaded CeO2 catalysts have higher oxygen vacancy concentra-
tion compared to the as prepared CeO2 support, implying a
promoting effect of the generation of active oxygen species for
the HCHO oxidation reaction. Meanwhile, as can be seen from
the TEM and XRD results, the high dispersing of the noble
metal may be the other key factor for high catalytic activities for
formaldehyde oxidation. Due to the strong synergetic interac-
tion between active component and CeO2 support, the redox
capability of the catalyst is enhanced by the defective CeO2.
Thus, when the catalysts were used in formaldehyde oxidation
process, the HCHO could react with the absorbed active oxygen
to form COOH intermediates and decomposed to CO2 rapidly.
Fig. 6 Raman spectra of CeO2 support (a) and noble metal/CeO2
catalysts: Pd/CeO2 (b), Pt/CeO2 (c), Au/CeO2 (d) and Ag/CeO2 (e).
vacancies may be responsible for the enhanced catalytic activity
for HCHO oxidation.
3.3 In situ DRIFT study
In situ DRIFT spectra were employed to explain the signicantly
enhanced catalytic activity of as prepared noble-metal/CeO2
catalysts solid solution for HCHO oxidation. Fig. 7 shows in situ
DRIFT spectra of Pd/CeO2 material exposed to 600 ppm of HCHO
ꢀ
+ 20.0 vol% O2 + N2 at 25 C. Aer exposed to HCHO + O2 + N2
mixture, the bands at 2940, 2860, 2320, 1540 and 1340 cmꢁ1
appeared. With the time increasing, the band intensities
increased and reached a steady level aer expose for several
minutes, more rapid than reported before. According to the
literature, two bands at 1540 and 1340 cmꢁ1 could be ascribed to
nas(COO) and ns(COO). The small bands at about 3050, 2900 cmꢁ1
4. Conclusions
A series of mesoporous CeO2 supported noble metal (Pt, Pd, Au
and Ag) catalysts were fabricated through a facial pyrolysis and
in situ reduction protocol and were used for formaldehyde
elimination under ambient condition. The as prepared CeO2
support was composed of the aggregation of CeO2 nano-crystal
with several nanometers, which contain abundant of oxygen
vacancies. When combined with noble metal species, the
signicant catalytic activities could be achieved. For 1% noble
metal loaded materials, Pt/CeO2, Pd/CeO2 and Au/CeO2 cata-
lysts could complete catalytic oxidize HCHO at room tempera-
ture. Even for the lower-active Ag/CeO2 catalyst, the complete
conversion temperature could be reached to 100 ꢀC, much lower
than that reported before. Such highly catalytic properties could
be assigned to the strong synergetic interaction between highly
dispersed active component and nano-crystalline CeO2 support
with abundant oxygen vacancies.
Acknowledgements
Fig. 7 In situ DRIFT spectra of formaldehyde oxidation over noble
metal/CeO2 catalysts: Pd/CeO2 (a), Pt/CeO2 (b), Au/CeO2 (c) and Ag/
CeO2 (d).
This study was supported by National Basic Research Program
of China (973 Program) no. 2013CB933201.
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18 S. Song, J. Ding, J. Bao, C. Gao, Z. Qi and C. Li, Catal. Lett.,
2010, 137, 239–246.
Notes and references
19 J. Quiroz Torres, S. Royer, J. P. Bellat, J.-M. Giraudon and
J.-F. Lamonier, ChemSusChem, 2013, 6, 578–592.
20 R. V. Gulyaev, E. M. Slavinskaya, S. A. Novopashin,
D. V. Smovzh, A. V. Zaikovskii, D. Y. Osadchii,
O. A. Bulavchenko, S. V. Korenev and A. I. Boronin, Appl.
Catal., B, 2014, 147, 132–143.
1 T. Salthammer, S. Mentese and R. Matrutzky, Chem. Rev.,
2010, 110, 2536–2572.
2 Y. Sekine, Atmos. Environ., 2002, 36, 5543–5547.
3 K. J. Lee, N. Shiratori, G. H. Lee, J. Miyawaki, I. Mochida and
J. Jang, Carbon, 2010, 48, 4248–4255.
4 Z. Xu, J. Yu and W. Xiao, Chem.–Eur. J., 2013, 19, 9592–9598.
5 C. Zhang, H. He and K.-I. Tanaka, Appl. Catal., B, 2006, 65,
37–43.
21 M.-F. Luo, Z.-Y. Hou, X.-X. Yuan and X.-M. Zheng, Catal.
Lett., 1998, 50, 205–209.
22 B. Wang, D. Weng, X. Wu and R. Ran, Appl. Surf. Sci., 2011,
257, 3878–3883.
23 A. K. Datye, J. Bravo, T. R. Nelson, P. Atanasova,
M. Lyubovsky and L. Pfefferle, Appl. Catal., A, 2000, 198,
179–196.
24 A. S. Ivanova, E. M. Slavinskaya, R. V. Gulyaev,
V. I. Zaikovskii, O. A. Stonkus, I. G. Danilova,
L. M. Plyasova, I. A. Polukhina and A. I. Boronin, Appl.
Catal., B, 2010, 97, 57–71.
6 C. Zhang, F. Liu, Y. Zhai, H. Ariga, N. Yi, Y. Liu, K. Asakura,
M. Flytzani-Stephanopoulos and H. He, Angew. Chem., 2012,
124, 9766–9770.
7 B. Liu, C. Li, Y. Zhang, Y. Liu, W. Hu, Q. Wang, L. Han and
J. Zhang, Appl. Catal., B, 2012, 111–112, 467–475.
8 B.-B. Chen, C. Shi, M. Crocker, Y. Wang and A.-M. Zhu, Appl.
Catal., B, 2013, 132–133, 245–255.
9 L. Ma, D. Wang, J. Li, B. Bai, L. Fu and Y. Li, Appl. Catal., B,
2014, 148–149, 36–43.
25 G. Li, L. Li, Y. Yuan, J. Shi, Y. Yuan, Y. Li, W. Zhao and J. Shi,
Appl. Catal., B, 2014, 158–159, 341–347.
10 B.-B. Chen, X.-B. Zhu, M. Crocker, Y. Wang and C. Shi, Appl.
Catal., B, 2014, 154–155, 73–81.
26 P. Bera, K. C. Patil, V. Jayaram, G. N. Subbanna and
M. S. Hegde, J. Catal., 2000, 196, 293–301.
11 H.-F. Li, N. Zhang, P. Chen, M.-F. Luo and J.-Q. Lu, Appl.
Catal., B, 2011, 110, 279–285.
27 K. R. Priolkar, P. Bera, M. S. Hegde, S. Emura, R. Kumashiro
and N. P. Lalla, Chem. Mater., 2002, 14, 2120–2128.
28 W. H. Weber, K. C. Hass and J. R. McBride, Phys. Rev. B:
Condens. Matter Mater. Phys., 1993, 48, 178–185.
12 R. Averlant, S. Royer, J.-M. Giraudon, J.-P. Bellat,
I. Bezverkhyy, G. Weber and J.-F. Lamonier, ChemCatChem,
2014, 6, 152–161.
13 D. Chen, Z. Qu, Y. Sun, K. Gao and Y. Wang, Appl. Catal., B,
2013, 142–143, 838–848.
´
´
´
29 J. M. Lopez, R. Arenal, B. Puertolas, A. Mayoral, S. H. Taylor,
´
B. Solsona and T. Garcıa, J. Catal., 2014, 17, 167–175.
14 L. Nie, J. Yu, X. Li, B. Cheng, G. Liu and M. Jaroniec, Environ.
Sci. Technol., 2013, 47, 2777–2783.
15 S. Yang, M. Besson and C. Descorme, Appl. Catal., B, 2010,
100, 282–288.
16 H. Huang and D. Y. C. Leung, ACS Catal., 2011, 1, 348–354.
17 Z. Xu, J. Yu and M. Jaroniec, Appl. Catal., B, 2015, 163, 306–
312.
30 D. Andreeva, R. Nedyalkova, L. Ilieva and M. V. Abrashev,
Appl. Catal., B, 2004, 52, 157–165.
31 G. W. Graham, W. H. Weber, C. R. Peters and R. Usmen, J.
Catal., 1991, 130, 310–313.
32 C. Li, K. Domen, K. Maruya and T. Onishi, J. Catal., 1990,
125, 445–455.
This journal is © The Royal Society of Chemistry 2015
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