Ag3PW12O40/C3N4 nanocomposites as an efficient photocatalyst for hydrocarbon selective oxidation

Article abstract of DOI:10.1039/c6ra09235g

Ag₃PW₁₂O₄₀/C₃N₄ nanocomposites were successfully synthesized by loading Ag₃PW₁₂O₄₀ into C₃N₄, in which case Ag₃PW₁₂O₄₀

Full text of DOI:10.1039/c6ra09235g

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: Z. kang, Y. Zhang,
L. hu, S. zhao, N. Liu, L. Bai, J. Liu, H. Huang and Y. liu, RSC Adv., 2016, DOI: 10.1039/C6RA09235G.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
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. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
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 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.
www.rsc.org/advances

Please do not adjust margins
RSC Advances
Page 1 of 6
View Article Online
DOI: 10.1039/C6RA09235G
Journal Name
ARTICLE
Received 00th January
20xx,
Ag PW O /C N nanocomposites as an efficient photocatalyst
3
12 40
3
4
for hydrocarbon selective oxidation
§
§
Yalin Zhang, Lulu Hu, Shunyan Zhao, Naiyun Liu, Liang Bai, Juan Liu,* Hui Huang,* Yang Liu* and Zhenhui Kang
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
The Ag
3
PW12
O
40/C
3
N
4
nanocomposites were successfully synthesized by loading Ag
3 3 4
PW12O40 into C N , in which case
Ag
3
PW12
O
40 is gained through reaction between AgNO and 40 at room temperature. The obtained
3
3
H PW12O
nanocomposites show efficient and light-operated catalytic activity for hydrocarbon selective oxidation (selective
o
oxidation of cyclooctene and cyclohexane) without adding any oxidant at 60 C. For cyclooctene, the conversion based on
cyclooctene is 41.26 %, and the selectivity of selective oxidation epoxycyclooctane can be up to 77.2 %. The
nanocomposites catalyst yielded oxidation of cyclohexane to cyclohexanone with 8.62 % efficiency and > 99.0 % selectivity.
In the catalytic system, the oxidant (H
decomposed into HO· with the help of Ag
of cyclooctene and cyclohexane is mainly attributed to the high BET surface area of C
Ag 40 and C , the nanocomposites display considerable catalytic activity, which shed light on the catalyst design
applied in selective oxidation of hydrocarbon.
2
O
2
) in the catalysis process can be produced by the irradiation of C
40. The observed improvement in the activities of photo-induced oxidation
. With the synergistic effect of
3 4
N and then
3
PW12O
3 4
N
3
PW12O
3 4
N
which is in contradiction with sustainable development.
Therefore, it is of utmost emergency to seek a new route to
design the photocatalysis with high performance.
Introduction
The selective oxidation of hydrocarbons is a crucial process in
the manufacture of high-tonnage commodities, high-value fine
chemicals, agrochemicals and pharmaceuticals, which targets
addition of oxygen atoms to produce specifically desired
reaction products, such as diols, epoxides, alcohols and
Graphitic carbon nitride (g-C
3 4
N ) has attracted tremendous
8
,
interests as a metal-free and visible light active photocatalyst,
9
which possesses excellent characteristics for photocatalysis,
such as harvesting sunlight, a suitable redox potential to
efficiently catalyze reactions, chemical and photocatalytic
stability, abundant and inexpensive building elements. More
important, in recent researches, some reports demonstrated
1
-4
carbonyl compounds.
Among various alkane oxidation,
selective oxidation of cyclooctene and cyclohexane arouse
extensive interest due to its products as intermediates of
Nylon-6 and Nylon-66. However, despite tremendous efforts in
the past years, developing efficient catalysts with high
efficiency and selectivity still remains a great challenge, one of
which lies at the key of choice of oxidant. In quest of oxidants,
O and H O appear to be the preferable oxidants attributed to
the C
that H
photocatalysis.
3
N
4
can produce H
2
O
2
under illumination, which indicates
-based
2
O can be used as the source of oxidants by C N
3 4
8
,10
The polyoxometalates (POMs), as typical oxidation catalysts,
have received increasing attention due to their numerous
advantageous properties, such as inorganic nature,
thermodynamic stability to oxidation, hydrostability, tunability
2
2 2
high content of active oxygen sites and coproduction of only
5
water (no coproducts in some cases).
-7
Whereas, the
1
1-14
of redox, acid properties and so on.
Recently, Xue et al.
utilization of these oxidants is still not as high as expected. In
addition, the reaction conditions always need higher
temperature, higher pressure, and an initiator or co-catalyst,
developed a kind of multi-cationic polyoxometalate-based
hybrid catalyst for heterogeneous cyclohexane oxidation in the
1
.
5
presence of H
2
O
2
2 2
It turned out that the H O couldn’t be
fully utilized due to its self-decomposition, where even half or
more amount of the dosage is wasteful.
In view of light-induced H
and oxidation characteristic
Ag nanocomposites may offer an ideal method
to improve the efficiency of oxidation of hydrocarbons. Here,
we demonstrate facile two-step method to obtain
Ag nanocomposites, including pyrolysis of urea
to get C nanosheets and subsequent combination with both
AgNO
2
O
2
generation property of C
3 4
N
of POM, designing
3
3 4
PW12O40/C N
a
3
3 4
PW12O40/C N
3 4
N
3
and H
3
PW12
O40 at room temperature. The obtained
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 2 of 6
View Article Online
DOI: 10.1039/C6RA09235G
ARTICLE
Journal Name
Ag
operated catalytic activity for hydrocarbon selective oxidation
selective oxidation of cyclooctene and cyclohexane) without
3 3 4
PW12O40/C N nanocomposites show efficient and light-
(
o
adding oxidant at 60 C. An illustration of the present synthesis
strategy for the Ag nanocomposites is shown in
3
3 4
PW12O40/C N
Figure 1. (a and b) SEM and TEM images of Ag
a) is the corresponding EDS spectrum. (c) XRD patterns of Ag
nanocomposites and Ag 40 nanoparticles (black and red lines, respectively). (d)
UV-Vis diffuse reflectance absorption spectra of Ag nanocomposites,
Ag 40 nanoparticles and C (black, blue and red lines, respectively).
3 3 4
PW12O40/C N nanocomposites, inset in
(
3 3 4
PW12O40/C N
3
PW12O
3 3 4
PW12O40/C N
Scheme 1. Synthesis strategy for Ag
3 3
PW12O40/C N
4
nanocomposites and the
3
PW12
O
3 4
N
corresponding conversion/selectivity for hydrocarbon selective oxidation.
with
Ag
H
3
PW12
40/C
O
40 for further reaction. The desired
nanocomposites can be obtained by a series
Scheme 1. For selective oxidation of cyclooctene, the
conversion can achieve 41.26 %, and the selectivity of
oxidation epoxycyclooctane can be up to 77.2 %. The
nanocomposites catalyst yielded oxidation of cyclohexane to
cyclohexanone with 8.62 % efficiency and > 99.0 % selectivity.
In our strategy, H O is used as the source of H O produced by
3
PW12
O
3
N
4
of centrifugation and washing (the detailed experiments
shown in Supplementary Information 1.1-1.3).
All photocatalyst characterizations are exhibited in
Supplementary Information section 1.4 in detail. Figure 1a
shows the typical scanning electron microscopy (SEM) image
2
2 2
the irradiation of C N , which is of great importance to
4
3
3 3 4
of the obtained Ag PW12O40/C N nanocomposites, which
generate oxidants slowly upon the employment of light.
Thereby, it is beyond doubt that H O can be taken full
reveals a two-dimensional nanostructure consisting of flat
sheets with wrinkles and irregular shape. The Energy
Dispersive X-ray Spectroscopy (EDS) image inserted in Figure
2
2
advantage of to improve the conversion of substrate. In
addition, the Ag PW O /C N nanocomposites reveal high
3
12 40
3 4
1
a indicates that the nanocomposites constitute of Ag, P, W, O,
efficiency for the hydrocarbon selective oxidation under light
irradiation.
C and N elements without other impurities. The TEM image of
the Ag
3
PW12
O40/C
3
N
4
nanocomposites shown in Figure 1b
O40 nanoparticles with the diameter of
displays the Ag
3
PW12
around 5 nm are uniform spheres and well-dispersed on the
nanosheets. The X-ray diffraction (XRD) patterns of the
In our experiments, briefly, based on facile two-step method, as-prepared Ag PW O /C N nanocomposites (black line) and
Results and Discussion
3 4
C N
3
12 40
3 4
as-synthesized C
image is shown in Figure S1) was added into AgNO
subsequent stirring. Then, the obtained sample was mixed
3 4
3 12 40
N (transmission electron microscopy (TEM) Ag PW O nanoparticles (red line) are shown in Figure 1c. All
3
solution for the characteristic diffraction peaks of Ag PW O
3
12 40
nanoparticles can be readily matched with that in
3 3 4 3 3 4
Ag PW12O40/C N nanocomposites, and the Ag PW12O40/C N
nanocomposites show highly crystallized without any
o
impurities. In addition, the peak at 27.5 in the black line can
be assigned to the layered stacking with a distance of 0.326
1
6, 17
nm, which is consistent with the reported g-C
Vis diffuse reflectance absorption spectra of Ag
nanocomposites (black line), Ag 40 nanoparticles (blue
line) and C (red line) are shown in Figure 1d. The spectrum
of C (red line) shows typical semiconductor optical
characteristics as reported,
Ag obviously confirms the formation of the
composite structure. These results indicate that the desired
Ag nanocomposites were successfully
synthesized in the designed synthesis process.
3
N
4
.
The UV-
3
3 4
PW12O40/C N
3
PW12O
3 4
N
3 4
N
1
8
and the spectrum of
3
PW12
PW12
O
40/C
3 4
N
3
O40/C
3 4
N
The X-ray photoelectron spectroscopy (XPS) is served to
analyze the chemical state of elements in the compositions.
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 3 of 6
View Article Online
DOI: 10.1039/C6RA09235G
Journal Name ARTICLE
Due to the little amount of
P
(Ag
3
PW12
O
40
,
1.7%; Ag
3
PW12
O40/C
3
N
4
are illustrated in Figure 2e. The two main
Ag
Figure S2). As for pure Ag
gives three obvious peaks which belong to W, O and Ag in peak is assigned to π exicitation. Based on above discussions,
Figure S2a and Figure 2a-c. As shown in Figure 2a, W 4f can be the Ag compositions are synthesized
deconvoluted into two main peaks located at 34.4 eV and 36.5 successfully.
eV for W 4f7/2 core excitation in Ag 40, which are close to
the theoretical values of the oxidation state of tungsten.
3
PW12
O
40/C
3
N
4
, 0.24%), it is not obvious to be detected peaks at 397.4 eV and 398.9 eV are attributed to imine
1
9
(
3
PW12O40, the survey spectrum nitrogen atoms and C=N-C bond, respectively. The weaker
2
4
3
3 4
PW12O40/C N
3
PW12O
1
9,20
The high resolution XPS spectra of the O 1s are presented in
Figure 2b, where three peaks are exhibited at 531.7 eV, 530.9
eV and 529.5 eV, respectively. The former two peaks are
corresponding to the lattice oxygen in the Keggin structure of
P-O and W-O-W bond, and another one is attributed to the O-
2
1,22
Ag bond, which is further confirmed in Ag 3d spectrum.
The spectrum of Ag 3d show two main peaks at around 367.1
eV and 373.1 eV in Figure 2c, which are assigned to Ag-O bond
and the standard metallic Ag 3d3/2, separately. With respect to
Ag PW O /C N compositions, the high resolution XPS
2
Figure 3. N adsorption and desorption isotherms at 78 K. BET surface area was
3
12 40
3 4
measured by Tristar II 3020.
spectra also present the elements of W, O and Ag exhibited in
Figure S2b and Figure 2a-c, which are large identical but
The photocatalytic efficiency of C
25,26
3
N
4
can be controlled by
, a
3 4
N ) were synthesized
the surface area.
To achieve a high-surface area of C
3 4
N
series of porous graphite-like C
3
N
4
(pg-C
by adding ammonium hydroxide into urea. Detailed
information was shown in Supplementary information 1.2.
Figure 3 displays nitrogen adsorption/desorption isotherms of
g-C
hydroxide. The curves exhibit that samples possess typical type
isotherm, which is attributed to the weak adsorbent-
adsorbent interaction and porous structure. The surface area
3 4 3 4
N and pg-C N with different amount of ammonium
Ⅲ
2
-1
2 -1
of g-C
3 4
N is 57.62 m g , while it increases to 95.50 m g ，
2
-1
61.27 m g , 168.25 m g for pg-C N prepared with addition
2 -1
1
3 4
of 1 mL, 3 mL, 5 mL ammonium hydroxide respectively,
suggesting that the utilization of ammonium hydroxide can
significantly increase the surface area of final product.
3 3 4
To evaluate the catalytic ability of Ag PW12O40/C N
nanocomposites, the selective oxidation of cyclooctene and
Figure 2. The W 4f, O 1s, Ag 3d spectra of Ag
in (a) (b) and (c), respectively. The upper spectra belong to Ag
a-c) show the XPS spectra of Ag
spectra of Ag
3
PW12
O
40 and Ag
3
PW12
O
40/C
3 4
N are shown
cyclohexane with the nanocomposites as catalyst was
o
composites. (d) C 1s and (e) N 1s investigated without oxidant at 60 C under near ultraviolet
3
PW12
O40, the bottom of
(
3
PW12O
3
40/C N
4
3 3 4
PW12O40/C N .
(
NUV
40, the Information section 1.5 in detail. The oxidation products were
two main peaks of W 4f are located at 36.3 eV and 34.2 eV analyzed by gas chromatography (GC) and gas chromatography
with a little shift shown in Figure 2a. When it comes with O 1s
massspectroscopy (GC-MS). We proceeded to optimize the
in Figure 2b, the three main peaks at around 532.3 eV, 530.9 catalyst composition by measuring the conversion of
eV and 529.3 ev are similar as Ag 40 just with little shift cyclooctene for different BET surface area of C N (Figure S3).
and intensity change, where P-O and W-O-W increases and the The conversion of cyclooctene increased with increasing BET
amount of Ag-O bond decreases with the addition of C
surface area. So in the following experiments, C N with the
which makes a difference in chemical environment of oxygen. BET surface area of 168.25 m /g was used to fabricate the
As shown in Figure 2c, Ag 3d spectra of compositions exhibit Ag PW O /C N
nanocomposites and detect its
40. Moreover, the photocatalytic activities. Details of the conversion and
λ > 400 nm), which was shown in Supplementary
3
with minor difference. Compared with pure Ag PW12O
−
3
PW12O
3
4
3 4
N
3
4
2
3
12 40
3 4
3
the same chemical state as pure Ag PW12O
compositions also present another two elements in high selectivity of cyclooctene oxidation catalyzed by
resolution XPS spectra. As depicted in Figure 2d, the C 1s Ag PW O /C N nanocomposites are shown in Figure 4a and
3
12 40
3 4
spectra exhibits the main contribution with the binding energy Table S1. As shown in Figure 4a, after 48 h reaction, the
of 287.8 eV ascribed to sp -bonded carbon (N-C=N) in the
2
hetero-cycle ring, the peak locating at 286.7 eV corresponded
2
3
to the C-OH, and a weak peak at 283.4 eV. Another weaker
peak at 284.8 eV is the graphite carbon, which is usually
observed in carbon nitrides. The N 1s signals of the synthesized
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 4 of 6
View Article Online
DOI: 10.1039/C6RA09235G
ARTICLE
Journal Name
3 3 4
the highlight effectiveness of Ag PW12O40/C N catalyst. First,
the blank reaction without catalyst was carried out, which
shows that none of oxidation products generated. (Table S1).
Moreover, the filtrate solution test (an additional 24 h of
3 3 4
reaction after removing the Ag PW12O40/C N composites from
the reaction medium) showed no catalytic activity, indicating
that leaching did not play an important role in the present
system. Figure 4c and Table S2 show the detailed conversion
based on cyclooctene with different catalysts under
illumination or dark. As shown, the Ag
catalyst in dark (black line) yielded low conversion (2.03 %) for
selective oxidation of cyclooctene. In addition, the Ag
and C N used separately as catalyst (olive and navy lines,
3 3 4
PW12O40/C N as
3
PW12O
40
3
4
respectively) achieved cyclooctene oxidation with lower
conversion of only 0.89 % and 0.68 %, respectively under dark.
It is worth mentioning that in spite of illumination, the
Figure 4. (a) Time dependence of the conversion and selectivity of the oxidation of
cyclooctene with Ag
The conversion and selectivity of the oxidation of cyclooctene on the Ag
composites as photocatalyst over cycling times. (c) Time dependence of the
3 3 4
PW12O40/C N nanocomposites as photocatalyst driven by NUV. (b)
3
PW12O40/C
3
N
4
conversion based on cyclooctene with Ag PW12O40 (red line) as
3
6
catalyst is still not as high as expected (0.97 %). However,
under illumination, the conversion based on cyclooctene with
conversion and selectivity of the oxidation of cyclooctene with different catalysts under
illumination or dark. (d) The conversion of the oxidation of cyclooctene with
Ag
by a 300 W Xe lamp using different band-gap filters. Red line: 400±10 nm; Green line:
25±10 nm; Blue line: 620±10 nm; Purple line: 750±10 nm. All of the light irradiations
3
PW12
O
40/C
3
N
4
nanocomposites as photocatalyst driven by different light irradiations C N as catalyst displays slight improvement (9.25 %, blue line)
3 4
(
because the system can generate H O upon light induces C N ,
2
2
3 4
5
-
2
intensities were kept at 10 mW cm ).
which is used to contribute to the oxidation of cyclooctene. In
return, H O can also poison the catalyst leading to a little
conversion of cyclooctene reached 41.26 %, and the
selectivity to 2-hydroxycyclooctanone and epoxycyclooctane
were 21.4 % and 77.2 %, respectively, which reveals that the
selectivity to epoxycyclooctane increased with increasing the
reaction time, while the selectivity to 2-hydroxycyclooctanone
decreased with the reaction time prolong. These results
2
2
8
increasement of conversion. These results demonstrate
Ag PW O /C N composites indeed function as a high-
3
12 40
3 4
performance photocatalyst in the present reaction system.
Cyclooctene oxidation was further carried out with the
optimized Ag PW O /C N composites catalyst driven by
3
12 40
3 4
lights of different wavelengths (Figure 4d). As shown, the best
conversion can be obtained at the near ultraviolet (red line),
whose wavelength well matches with the UV-Vis absorption
spectra of C N .
3 3 4
indicate that catalytic selectivity of Ag PW12O40/C N
nanocomposites may be tunable by careful selection of
reaction conditions and excessive oxidation of the product (2-
hydroxycyclooctanone) can be reduced by using the
nanocomposites as catalyst. The turnover frequency (TOF) was
employed to evaluate the catalytic activities, which was
calculated by determining the moles of product formed (or
reactant consumed) per unit time per mole of available active
sites on the catalyst. Calculation details are shown in
Supplementary Information section 1.7. The TOF of
3
4
To further evaluate the catalytic activity of Ag PW O /C N ,
3
12 40
3 4
the catalytic oxidation of cyclohexane was carried on with the
optimized nanocomposites as catalyst. The oxidation products
were analysed by GC and GC-MS. Figure 5a shows the time
dependence of the conversion and selectivity of cyclohexane
oxidation to cyclohexanone with Ag PW O /C N composites
3
12 40
3 4
-
1
as the photocatalyst driven by NUV (λ> 400 nm) and dark. As
Ag
3
PW12
O40/C
3
N
4
based on cyclooctene oxidation was 2.65 h .
shown in Figure 5a, under illumination, the conversion
efficiency can achieve to 8.62 % with increasing reaction time,
while the selectivity to cyclohexanone is nearly constant at
To explore the stability of the Ag PW12O40/C N
3
3 4
nanocomposites catalyst, the repetitive experiments were
performed under the same condition. As shown in Figure 4b,
9
9.0 %. When dark, after 48 h, the conversion and selectivity
the Ag
experiments without exhibiting any significant loss of catalytic
activity and selectivity. After recycling times,
Ag still retains high catalytic activity (conv.%
0.2 %) and selectivity of epoxycyclooctane (select.%
0.2 %) after 48 h reaction. Moreover, the influence of
40 loaded on the C on the
catalytic activities was evaluated shown in Figure S4. As shown,
with increasing the amount of Ag 40 from 13.8 % to
4.1 %, the catalytic activities increased firstly and then fell.
1.54 % was the optimal amount of Ag 40 at the reaction
3
PW12
O
40/C
3
N
4
is stable during the repeated
of oxidation product catalyzed by Ag PW O /C N are 1.78 %
3
12 40
3 4
and 96.6 % respectively, which are both lower than that of
illumination condition. The results demonstrate the
6
3
3 4
PW12O40/C N
Ag
3 3 4
PW12O40/C N nanocomposites are efficient and light-
4
1.26
7.2
±
operated catalyst for cyclohexane oxidation. The TOF of
7
±
-1
3 3 4
Ag PW12O40/C N based on cyclohexane oxidation was 0.67 h
different amounts of Ag
3
PW12
O
3 4
N
shown in Supporting Information section 1.7. In the following
experiments, the blank reaction (without catalyst) and filtrate
solution test (an additional 24 h of reaction after removing the
3
PW12
O
9
6
3 3 4
Ag PW12O40/C N composites from the reaction medium) were
3
PW12
O
also investigated. The results show no conversion and
selectivity of oxidation product can be obtained, further
time of 48 h. This might be ascribed to the excessive amount
of Ag 40, in which case the surface area of C reduces,
3
PW12
O
3 4
N
3 3 4
revealing the Ag PW12O40/C N nano- composites catalyst is
resulting in the decrease in photocatalytic efficiency. For
comparison, the different catalysts were employed to estimate
efficient for the reaction. The repeated catalytic oxidation of
4
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 5 of 6
View Article Online
DOI: 10.1039/C6RA09235G
Journal Name ARTICLE
2
−
as O ·
cyclohexane was also carried out using Ag
3
PW12
O40/C
3
N
4
radical
scavenger)
and
disodium
catalyst for 6 times shown in Figure 4b, which once again ethylenediaminetetraacetate (Na
2
-EDTA, a hole scavenger) are
proves the Ag
application.
3
PW12
O40/C
3
N
4
are stable for the practical used. The photocatalytic performances in Figure 6b are shown
that the addition of tert-butanol substantially reduced the
Bearing in mind our previous discussion on the mechanism photocatalytic activity for the oxidation of cyclohexane from
of catalysis oxidation of cyclohexane over C /Au composites, almost 41 % to 3.93 % in 48 h. The introduction of BZQ and
the important factor which is also the rate-limiting step here Na -EDTA do not affect the photocatalysis results. It implies
seems to be the ability of H generated from water that ·OH radical is the main reactive species. While
3 4
N
2
2 2
O
2
7
2−
oxidation. In this work, the whole oxidation process of
O · radicals and holes do not contribute to photocatalytic
performance. The addition of tert-butanol traps the ·OH
radicals leading to low conversion of cyclohexane. It confirms
3 3 4
that in the buffer solution containing Ag PW12O40/C N catalyst,
a larger number of HO· will be produced with visible light
irradiation.
Based on the above results, the catalytic reaction process of
the Ag PW O /C N nanocomposites as catalyst can be
3
12 40
3 4
described as followed: under illumination, the C N4 can
3
produce H O acting as a free radical initiator, and then the
2
2
Figure 5. (a) Time dependence of the conversion and selectivity of the selective
oxidation of cyclohexane with Ag
driven by NUV (λ > 400 nm). (b) The conversion and selectivity of the oxidation of
cyclohexane on the Ag composites as photocatalyst over cycling 6 times.
3
PW12
O
40/C
3
N
4
nanocomposites as photocatalyst generated H
2
O
2
could be decomposed by Ag
3
PW12
O
40 to come
into being the reactive oxygen species (HO·), which may
directly oxidize the hydrocarbon (cyclooctene and cyclohexane)
to form a primary epoxide and other higher oxidization state
products in the sequential oxidation process.
3
3 4
PW12O40/C N
cyclootene and cyclohexane maybe include two steps. First,
the light-induced water splitting process on C will generate
and H as production. Then H is decomposed to the
reactive oxygen species (HO·) by Ag 40. Here we have
proved that. First the electrochemical behavior of
Ag modified electrodes is measured using a
linear sweep voltammetry method in 0.1 M phosphate buffer
solution (PBS, pH 7.4) in the presence of 10 and 20 mM H
as shown in Figure 5a. After adding H , an obvious reduction
current at about -0.2 V (vs. RHE) is observed. With the
concentration of H increasing, the reduction current
2 2
3 3
increased, which can be due to the decomposition of H O . To Figure 6. (a) Linear sweep voltammetry of Ag PW12O40/C N4 modified glass carbon
3 4
N
H
2
O
2
2
2 2
O
3
PW12O
3
3 4
PW12O40/C N
2 2
O
2 2
O
2 2
O
electrode in 0.1 M PBS (black trace), 0.1 M PBS containing 10 mM H
PBS, red trace) and 20 mM H -PBS (blue trace) at a scan rate of 10 mV/s. (b)
Photocatalysis activities of Ag in reactive species trapping experiments
2 2 2 2
O (10 mM H O -
further prove that we added o-tolidine as peroxide indicator to
2
O
2
the reaction system containing pure water and photocatalysts,
3
3 4
PW12O40/C N
and monitored the production of H
2 2
O
by measuring the with three kinds of reactive species scavengers.
absorption peak of o-tolidine at 446 nm using UV-Vis
1
4
spectroscopy. Note that we needed to strongly centrifuge
the solution (12000 rpm) and to remove the catalyst to be able Conclusions
to suppress the UV absorption background of the catalyst.
We demonstrate a facile two-step method to obtain
nanocomposites, including pyrolysis of urea
nanosheets and subsequent combination with both
and H 40 at room temperature. The obtained
nanocomposites show efficient and light-
operated catalytic activity for hydrocarbon selective oxidation
selective oxidation of cyclooctene and cyclohexane) without
adding oxidant at 60 under NUV. For selective oxidation of
cyclooctene, the conversion based on cyclooctene can achieve
1.26 %, and the selectivity of selective oxidation
Figure S5 shows that the absorption peak at 446 nm in the UV-
Vis spectrum (the top trace) was distinctly observed in the
reaction system with C N as catalyst after irradiation for 12 h.
Ag
to get C
AgNO
Ag
3
PW12
O
40/C
3
N
4
3 4
N
3
4
3
3
PW12O
There is no H O found as using Ag PW O /C N
3 4
2
2
3
12 40
3
PW12
O40/C
3
N
4
nanocomposites instead of C N (in Figure S5, the bottom
3
4
trace). An electron transfer number determination test shown
in Supporting Information section 1.6 was carried out on
rotating ring disk electrode (RRDE) further indicate that H O is
(
℃
2
2
the main water oxidation production under light irradiation
over C N (Figure S6).
4
3
4
epoxycyclooctane can be up to 77.2 %. The nanocomposites
catalyst yielded oxidation of cyclohexane to cyclohexanone
with 8.62 % efficiency and > 99.0 % selectivity. The
experimental results proved the oxidant in the catalysis
Previous studies explored the mechanism of HO· generation
by utilizing POM-based catalytic materials in the presence of
2
8,29
H O .
2
For further confirming the generation of HO·, a
2
reactive species trapping experiments were carried out to
investigate the reactive oxygen species in the photocatalytic
oxidation process. In this part, three different scavengers, tert-
butanol (a ·OH radical scavenger), p-benzoquinone (BZQ, a
3 4
process can be produced by the irradiation of C N . The
present work provides an exciting thought for the design of
high performance novel catalyst towards new energy sources
and environmental issues.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 6 of 6
View Article Online
DOI: 10.1039/C6RA09235G
ARTICLE
Journal Name
2
2
2
3 D. Dontsova, S. Pronkin, M. Wehle, Z. P. Chen, C.
Fettkenhauer, G. Clavel and M. Antonietti, Chem. Mater.,
Acknowledgements
2
015, 27, 5170-5179.
4 J. Liu, Y. Liu, N. Y. Liu, Y. Z. Han, X. Zhang, H. Huang, Y.
This work is supported by Collaborative Innovation Center of
Suzhou Nano Science and Technology, the National Basic
Research Program of China (973 Program) (2012CB825803,
2013CB932702), the National Natural Science Foundation of
China (51422207, 51132006, 21471106), the Specialized
Lifshitz, S. T. Lee, J. Zhong and Z. H. Kang, Science, 2015,
347, 970-974.
5 F. Z. Su, S. C. Mathew, G. Lipner, X. Z. Fu, M. Antonietti, S.
Blechert and X. C. Wang, J. Am. Chem. Soc., 2010, 132
,
16299-16301.
Research Fund for the Doctoral Program of Higher Education 26 J. Liu, Y. M. Yang, N. Y. Liu, Y. Liu, H. Huang and Z. H. Kang,
(
20123201110018), a Suzhou Planning Project of Science and
Green Chem., 2014, 16, 4559-4565.
7 T. Miyake, M. Hamada, Y. Sasaki and M. Oguri, Appl. Catal. A,
2
2
2
Technology (ZXG2012028), and a project funded by the Priority
Academic Program Development of Jiangsu Higher Education
Institutions (PAPD).
1
995, 131, 33-42.
8 Kenji Nomiya, Kei Hashino, Yukihiro Nemoto, Mai Watanabe,
J. Mol. Cata. A-Che., 2001, 176, 79-86.
9 P. X. Lei, C. C. Chen, J. Yang, W. H. Ma, J. C. Zhao and L. Zang,
Environ. Sci. Technol., 2005, 39, 8466-8474.
Notes and references
1
2
3
Y. Wen, X. Wang, H. Wei, B. Li, P. Jin and L. Li, Green Chem.,
012, 14, 2868-2875.
T. Newhouse and P. S. Baran, Angew. Chem. Int. Ed., 2011,
, 3362-3374.
K. Sato, M. Aoki and R. Noyori, Science, 1998, 281, 1646-
647.
G. Bellussi and C. Perego, CATTECH, 2000,
X. Q. Wang, J. P. Wu, M. W. Zhao, Y. F. Lv, G. Y. Li and C. W.
Hu, J. Phys. Chem. C, 2009, 113, 14270-14278.
A. Gonzalez-de-Castro and J. L. Xiao, J. Am. Chem. Soc., 2015,
2
5
0
1
4
5
4, 4-16.
6
7
8
137, 8206-8218.
Z. Guo, B. Liu, Q. H. Zhang, W. P. Deng, Y. Wang and Y. H.
Yang, Chem. Soc. Rev., 2014, 43, 3480-3524.
J. Liu, Y. Liu, N. Y. Liu, Y. Z. Han, X. Zhang, H. Huang, Y.
Lifshitz, S. T. Lee, J. Zhong and Z. H. Kang, Science, 2015, 347
70-974.
,
9
9
1
J. H. Liu, Y. W. Zhang, L. H. Lu, G. Wu and W. Chen, Chem.
Commun., 2012, 48, 8826-8828.
0 X. C. Wang , K. Maeda, X. F. Chen, K. Takanabe, K. Domen, Y.
D. Hou, X. Z. Fu and M. Antonietti, J. Am. Chem. Soc., 2009,
1
31, 1680-1681.
1 J. Liu, H. C. Zhang, D. Tang, X. Zhang, L. K. Yan, Y. Z. Han, H.
Huang, Y. Liu, and Z. H. Kang, ChemCatChem, 2014, , 2634-
641.
1
6
2
1
1
1
1
2 A. Dolbecq, P. Mialane, B. Keitab and L. Nadjo, J. Mater.
Chem., 2012, 22, 24509-24521.
3 A. Hiskia, A. Mylonas and E. Papaconstantinou, Chem. Soc.
Rev., 2001, 30, 62–69.
4 J. Huang, C. Tao, Q. An, W. Zhang, Y. Wu, X. Li, D. Shen and G.
Li, Chem. Commun., 2010, 46, 967–969.
5 X. C. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J. M.
Carlsson, K. Domen and M. Antonietti, Nature Materials,
2
009,
6 X. Chen, Y.-S. Jun, K. Takanabe, K. Maeda, K. Domen, X. Fu,
M. Antonietti and X. Wang, Chem. Mater., 2009, 21, 4093
095.
8, 76-80.
1
1
1
–
4
7 K. Schwinghammer, M. B. Mesch, V. Duppel, C. Ziegler, J.
Senker and B. V. Lotsch, J. Am. Chem. Soc., 2014, 136, 1730-
1
733.
8 G. H. Dong and L. Z. Zhang, J. Mater. Chem., 2012, 22, 1160-
166.
1
1
2
9 Z. Obalı and T. Doğu, Chem. Eng. J., 2008, 138, 548-555.
0 D. Mucha, L. Matachowski, T. Machej, J. Gurgul and R. P.
Socha, Solid State Sci., 2011, 13, 1276-1284.
2
2
1 J. Gurgul, M. Zimowska, D. Mucha, R. P. Socha and L.
Matachowski, J. Mol. Cata. A-Che., 2011, 135, 1-10.
2 M. Faur, D. T. Jayne, M. Goradia and C. Goradia, Surf.
Interface Anal., 1990, 15, 641-650.
6
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins