Comparison N-CU–codoped nanotitania and n-doped nanotitania in photocatalytic reduction of CO2under UV light

Article abstract of DOI:10.1080/15533174.2015.1137053

Nitrogen-copper–codoped nanotitania and nitrogen-doped nanotitania for CO₂ photoreduction by water in liquid phase were prepared by sol-gel method. The catalysts were characterized by XRD, HRTEM, DRS, FTIR, and XPS. N-doped TiO₂ have remarkably better photocatalytic activity than N- and Cu-codoped TiO₂ for the CO₂ photoreduction to acetone under ultraviolet illumination. The acetone yield of N₃/TiO₂ could reach 52.6 μmol/g h and the acetone yield of Cu_0.6N₄/TiO₂ could reach 33.2 μmol/g h under UV conditions. The mechanism of CO₂photoreduction on N-doped nanotitania and N-Cu–codoped TiO₂was proposed.

Full text of DOI:10.1080/15533174.2015.1137053

Synthesis and Reactivity in Inorganic, Metal-Organic, and
Nano-Metal Chemistry
ISSN: 1553-3174 (Print) 1553-3182 (Online) Journal homepage: http://www.tandfonline.com/loi/lsrt20
Comparison N-Cu co-doped nanotitania and N
doped nanotitania in photocatalytic reduction of
CO2 under UV light
Cuiping Liu, Tao Yu, Xin Tan & Xiang Huang
To cite this article: Cuiping Liu, Tao Yu, Xin Tan & Xiang Huang (2016): Comparison N-Cu co-
doped nanotitania and N doped nanotitania in photocatalytic reduction of CO2 under UV
light, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, DOI:
10.1080/15533174.2015.1137053
To link to this article: http://dx.doi.org/10.1080/15533174.2015.1137053
Accepted author version posted online: 18
Aug 2016.
Published online: 18 Aug 2016.
Submit your article to this journal
Article views: 1
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=lsrt20
Download by: [185.14.195.165]
Date: 11 September 2016, At: 04:31

ACCEPTED MANUSCRIPT
Comparison N-Cu co-doped nanotitania and N doped nanotitania in photocatalytic
reduction of CO2 under UV light
Cuiping Liu1,2 Tao Yu1 Xin Tan3 Xiang Huang1,3,*
1School of Chemical Engineering and Technology, Tianjin University,
2School of Science, Tianjin Chengjian University
3School of Science, Tibet University
*Corresponding Author Email: xiang.huang@utibet.edu.cn
Abstract
Nitrogen-copper co-doped nanotitania and nitrogen doped nanotitania for CO2 photoreduction by
water in liquid phase were prepared by sol-gel method. The catalysts were characterized by XRD,
HRTEM, DRS, FTIR, and XPS. N doped TiO2 have remarkably better photocatalytic activity than
N and Cu co-doped TiO2 for the CO2 photoreduction to acetone under ultraviolet illumination. The
acetone yield of N3/TiO2 could reach 52.6 μmol/g∙h and the acetone yield of Cu0.6N4/TiO2 could
reach 33.2μmol/g∙h under UV conditions. The mechanism of CO2 photoreduction on N doped
nanotitania and N -Cu co-doped TiO2 was proposed.
keywords
Nano-TiO2; Nitrogen and copper codoping; Sol-gel;CO2 photoreduction; Acetone.
1
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
1. Introduction
Global warming caused by the emission of greenhouse gases, primarily carbon dioxide (CO2), is
attracting increasing attention all over the world [1].It is highly desired to convert atmospheric
CO2 into useful substances. Previous work demonstrated that CO2 could be photocatalytically
reduced to carbon monoxide and hydrocarbons including methane, ethane, formaldehyde,
methanol, and formic acid [2-5] in both liquid phase and gas phase. Most of the investigations of
photoreduction of CO2 have focused on TiO2.From the view point of practical application, TiO2
is reasonably cheap, photo-stable, and non-toxic, making it a perfect candidate for photocatalytic
processes. Yet carbon dioxide conversion rates still low despite using ultraviolet illumination for
band gap excitations. [6].
Numerous studies have been reported on how to increase the photoreduction activity of TiO2 using
metal-doped modified TiO2 [7-9]. For example, the optimal Cu-loaded titania was a highly
efficient, photocatalyst for CO2 reduction since copper are an effective electron trapper [10-11].
Besides, nonmetal-doped TiO2 have been used as visible light-responsive photocatalysts for CO2
photoreduction. Significant enhancement of CO2 photoreduction to CO have been reported for
I-doped TiO2 due to the extension of TiO2 absorption spectra to the visible light region by I doping
[12].There have been literature reports that suggest that co-doping of metal and nonmetal species
on TiO2 leads to enhanced photoreduction activity as compared with single N-doped TiO2.For
example, Ni and N co-doped TiO2 for enhanced CO2 photoreduction as compared to N/TiO2
2
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
because of a smaller crystal size and higher surface area[13]. The V-N co-doped TiO2 nanotube
arrays co-doped TiO2 photocatalysts show remarkably enhanced photocatalytic activity for the
CO2 photoreduction to methane under ultraviolet illumination[14].
Among the current research of Cu and N doping into anatase TiO2, the photocatalytic activity
of some Cu-N co-doped TiO2 was considerably greater than that of the sample N doped TiO2 and
commercially available TiO2 which is attributed to the synergistic effect of Cu-N
co-doped[15-16].
But in Kuvarega’s particle, the Cu-N co-doped TiO2 showed least photoactivity than N doped
TiO2[17] due to the lowest adsorption capacity of Cu-N co-doped TiO2. In other words, the
photocatalytic activity of N and Cu co-doped TiO2 in photocatalytic was not absolutely better than
N doped TiO2. At present, Cu-N co-modified TiO2 for photocatalytic CO2 reduction has been
reported only once in the literature. Varghese et al [18] synthesized N-doped TiO2 nanotube
arrays sputtered with Cu nanoparticles as a co-catalyst and tested the catalytic activity for CO2
reduction with water under sunlight. The raw materials used in the work of Varghese were
expensive and the fabrication process was relatively complicated. In this work, we used a much
simpler method and cheaper raw materials to synthesize Cu and N co-modified TiO2
nanoparticles. The catalytic activities for the photocatalytic reduction of CO2 with water under
ultraviolet illumination and the mechanism of photocatalytic reduction CO2 on Cu-N co-doped
3
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
TiO2 catalyst. In order to comparion, photocatalytic reduction CO2 on N doped TiO2 were
proposed.
2. Experiment
2.1 Catalyst preparation
The synthesis of N and Cu co-doped TiO2 (N-Cu/TiO2) nanoparticles involved the following
steps:First, tetrabutyl titanate and ethanol were mixed and stirred for 30 min at room
temperature(solution A).A appropriate amount of acetic acid, copper
nitrate(Cu(NO3)2∙6H2O),urea, H2O, dissolved in ethanol(solution B). Then, solution B was
dropped into solution A and kept the solution stirring for 2 h. Thereafter, the solution was aged
until the gel formed. The gel was dried at 80℃ and calcined in a muffle at 500℃ for 2h. Then,
the N and Cu co-doped TiO2 samples can be obtained. The doping amount of N varied from 1 to 6
wt%(N:TiO2 = 1wt%,2wt%,3wt%,4wt%, 5wt%,6wt% respectively)and the amount of Cu2+ was
0.6wt%(Cu:TiO2 = 0.6wt%). (For short, hereafter, Cu0.6NX/TiO2 denotes the sample containing
X wt% of N and 0.6wt% of Cu2+).
2.2 Characterization
The phase compositions of samples were identified by X-Ray Powder Diffraction (Cu Kα
radiation). The UV-vis diffuse reflectance spectra (DRS) were recorded at room temperature on a
Shimadzu UV-3600 UV-vis spectrometer with barium sulfate as the reference sample. FT-IR
spectra of the samples were collected on a Nicolet 6700 FT-IR spectrophotometer at room
4
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
temperature by KBr method. Morphologies of samples were characterized using a high resolution
transmission electron microscope (JEM-2100F). The XPS measurement was performed using a
PHI1600 Analyzer.
2.3 Photocatalytic reduction of CO2
The photocatalytic reaction system was illuminated by a 365W Hg lamp in the center, and it
was shielded by a black box during the reaction to prevent interference from outside light. The
catalyst was suspended in 40 ml of 0.2mol/L NaOH aqueous solution. Ultra pure CO2 was bubbled
through the reactor for at least 30 min to eliminate the dissolved oxygen and saturate the solution.
The catalyst suspended solution was agitated by a magnetic stirrer. A needle-type probe was
inserted into the reactor to withdraw a small liquid sample, and after the catalyst powder were
filtered, the liquid sample was analyzed using gas chromatography (Agilent 6890N-05973).
Analysis indicated that acetone was the major hydrocarbon. Blank reactions were also conducted,
one without catalyst, and one without illumination; no hydrocarbon was detected in the blank tests.
Then the N and Cu co-doped TiO2 (Cu0.6N1/TiO2,Cu0.6N2/TiO2,Cu0.6N3/TiO2,Cu0.6N4/TiO2,
Cu0.6N5/TiO2,Cu0.6N6/TiO2) samples turned on to start the reaction. For the sake of comparison,
pure Cu0.6TiO2 and N doped TiO2 (N1/TiO2, N2/TiO2, N3/TiO2, N4/TiO2, N5/TiO2,
N6/TiO2)samples, also prepared by the similar procedure.
3. Results and Discussion
3.1 Characterization
5
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
3.1.1 XRD
Characteristics of samples the XRD of the catalysts in Fig.1 shows all samples were ascribed to
pure anatase TiO2 .The grain sizes of the catalyst were calculated from the Scherrer equation. The
particle sizes of sol-gel derived N-Cu co-doped TiO2 and N doped TiO2 are uniform and the
diameter is between 10-15nm, The particle sizes of Cu0.6N2/TiO2, Cu0.6N4/TiO2, Cu0.6N6/TiO2 are
15.2nm, 9.6nm, 13.7 nm respectively; N2/TiO2, N4/TiO2, N6/TiO2 are 11.0 nm, 9.1nm, 12.6 nm
respectively. From above the result, the particle sizes of Cu-N co-doped TiO2 are larger than N
doped TiO2.A detail analysis of XRD patterns was performed by enlarging the anatase (101) plane
of the samples as shown in the inset of Figure.1.(a) and (b), Figure.1.(a) indicated that the peak
position of the Cu-N co-doped TiO2 samples gradually shifted toward a higher diffraction angle. It
suggested that Cu, N might be incorporated into the crystal lattice of anatase[14]. Figure.1.(b)
indicated that the peak position of the N doped TiO2 samples gradually shifted toward a higher
diffraction angle too. However, peak position change of N4/TiO2 was not obvious, indicating that
the doped N might be excessive then inhibit the incorporation of N into crystal lattice.
3.1.2 FT-IR
Fig.2 shows the FTIR spectrum of TiO2, Cu0.6/TiO2, Nx/TiO2, and Cu0.6NX/TiO2. All of the
samples show similar FT-IR spectra, indicating the structure of TiO2 did not change after copper
and nitrogen-doping. The absorption bands at about 3406 cm−1 and 1663 cm−1are assigned to the
surface adsorbed water and hydroxyl groups. The absorption band corresponds to Ti-O-N was not
6
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
observed for the nitrogen-doped samples, probably because the amount of doped N was very
small. The peak at 500 cm−1 is due to stretching vibration of Ti-O[19,20]. The peak at 1380 cm−1
2-
was ascribed to the symmetric stretching vibration of bidentate carbonate b-CO3 bonded with
Ti4+-O2[21].The peaks were seen at 2330 cm−1 and 2360 cm−1, which can be assigned to the
stretching vibration of C-O, maybe due to the oxidation of existing C element when the products
exposed to air.[22]
3.1.3 TEM
The morphologies of the particles measured by transmission electron microscopy (TEM) are
given in Figure.3.(a)(b)(c).Figure.3.(a) shows the Cu0.6N4/TiO2 particles with uniform spheroidal
shape, and an average agglomerate size are about 9-12nm for Cu0.6N4/TiO2. The difference of the
particle size by TEM with that estimated by XRD results is attributed to the particle
agglomeration. The diffraction pattern of the Cu0.6N4/TiO2 shown in Figure.3.(b) indicates the
presence of TiO2 anatase with the typical (101) direction [23]. Fig.3.(c) shows the EDX spectrum
of Cu0.6N4/TiO2, which indicates the presence of Cu and N in the nanocomposite.
3.1.4 Optical property
Fig.4.(a) displays the UV-vis diffuse reflectance spectra of serial copper and nitrogen co-doped
TiO2.The Cu0.6N4/TiO2 and Cu0.6N2/TiO2 shows absorption in the UV region, However
Cu0.6N6-TiO2 shows absorption in the visible region. Fig.4.(b) presents the spectra of nitrogen
doped TiO2 and non-doped TiO2 samples. The N4/TiO2 and N2/TiO2 shows absorption in the UV
7
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
region. However, N6/TiO2 shows absorption in the visible region. Kubelka-Munk function was
used to estimate the band-gap energy of all samples [24]. The calculated results of band gap
energies for the Cu0.6-TiO2, Cu0.6N2-TiO2, Cu0.6N4-TiO2 and Cu0.6N6-TiO2 are 2.76eV, 2.98eV,
3.02eV and 2.86eV；TiO2, N2-TiO2, N4-TiO2 and N6-TiO2 are 3.03eV, 3.1eV, 3.06eV and 2.95 eV
respectively. It shows that the Cu-N co-doped TiO2 have a narrower band gap than that of N doped
TiO2 samples. And with the increase of N doping amount, an obvious red shift of the N-Cu/TiO2
and N/TiO2.The N6/TiO2 and Cu0.6N6/TiO2 absorption in the visible-light range was related to
impurity energy levels of N doping in the gap[25]-[26]. The reason of Cu0.6N2-TiO2, Cu0.6N4/TiO2,
N2/TiO2 and N4/TiO2 absorption in the UV-light range may be the small amount of N.
3.1.5 XPS
To explore the states of the copper and nitrogen doped species, the samples were subjected to
X-ray photoelectron spectroscopy (XPS) analysis. Fig.5.(a) shows the XPS survey spectrum of
the representative Cu0.6N4/TiO2 sample and TiO2. Obviously, Ti, O, N and C elements exist at the
surface of the sample. Fig. 5.(b) depicts the N 1s XPS spectra of Cu0.6N4/TiO2, showing the
peaks at the binding energy positions of ca.395-405 eV. After background subtraction and curve
fitting, the N1s peak could be decomposed to one component peaks centered at ca.400.23. These
peak were attributed to the signals of the molecularly chemisorbed nitrogen species (N2) or
nitroxide species (e.g., NO and NO2) [27].The peak related to the signal of Ti-N bonding (at ca.
8
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
396--397eV) was not observed [28].There were approximately 0.7% of lattice O atoms
substituted by N atoms for the Cu0.6N4/TiO2 sample.
3.2 Activity evaluation
3.2.1 The effect of N in photoreduction of CO2
The aqueous phase was analysed for the reduction products of CO2. Photoreduction of
products were determined by gas chromatography on a Hp-innowax column using a flame
ionization detector. During the research acetone is the only one hydrocarbon product to be detected
in the aqueous phase over all the samples.
From Fig.6, one can see that the unloaded TiO2 sample shows poor activity and there was
trace amount of acetone detected. The loading of Cu2+ and N generally promoted the formation of
acetone. The optimum loading amounts for N is 4 wt%. The acetone yield is two times that
achieved over the unloaded TiO2 sample. Fig.7 shows the loading of N sample promoted the
formation of acetone, too. The optimum loading amounts for N is 3 wt%; The acetone yield is
three times that achieved over the unloaded TiO2 sample. N doping can greatly enhance the
activity of light absorption. But when the doping amount of N is excess, N species may be piled
together on the crystal surface of TiO2.
The acetone yield of N3/TiO2 could reach 52.6μmol/g∙h and the acetone yield of Cu0.6N4/TiO2
could reach 33.2μmol/g∙h under UV conditions(λ = 365nm). In this article, N doped TiO2 have
better property than Cu-N co-doped TiO2 on photoreduction of CO2, the one reason is maybe the
9
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
particle sizes of N-doped TiO2 smaller than Cu-N co-doped TiO2 on the basis of XRD result; the
other reason is the band gap of N doped TiO2 (N2/TiO2-3.1eV;N4/TiO2-3.06eV) are little higher
than Cu-N co-doped TiO2 (Cu0.6N2/TiO2-2.98eV；Cu0.6N4/TiO2-3.02eV), meaning the better
absorption of ultraviolet light.
3.3 Mechanism of photoreduction of CO2
In liquid system of photoreduction of CO2, CH3OH, HCOOH often detected as
photoreduction production. At present, acetone as photoreduction product is scarce.
TiO2/Pd/Al2O3 system is quite noteworthy in relation to other semiconductor based systems
(TiO2/Pd/SiO2,etc) which generate abroad distribution of C1--C3 product (CH3OH, C2H5OH,
C3H6O),and the C3H6O yield notebalely higher than the yield of CH3OH and C2H5OH[29].C3H6O
may be producted by CH3OH and C2H5OH.Other based sample of derived from the urea
graphitic carbon nitride (u-g-C3N4) result in the formation of a mixture containing CH3OH
and C2H5OH,too[30]. Cu-N co-doped TiO2 and N doped TiO2 regard as the based sample due to
the N doping, so generate C3 product(C3H6O).
Therefore, we propose the following scheme. When illuminated by UV light, photo generated
electron and holes,photon-generated electrons(e) and holes (h+) are created on the surface of the
TiO2 catalysts(Eq.(1)). The holes first react with water adsorbed on the catalyst, producing
oxygen and H+ (Eq.(2)).The interaction of H+ ions with the excited electrons leads to the
formation of ∙H radicals (Eq. (3)). At the same time,∙CO2 radicals are formed by CO2(Eq.(4)).∙H
radicals react with ∙CO2 radicals leading to formation methyl alcohol and formaldehyde[30](Eq.(5)
10
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
and Eq.(6)).Then the ∙CH3 and H-∙C(OH) radicals are formed from methyl alcohol and
formaldehyde respectively(Eq.(7) and Eq.(8)) [29].The H-∙C(OH) radicals fixation via ∙CH3
radicals lead to form ethyl alcohol(Eq. (9)). So methyl alcohol and ethyl alcohol possiblely
produce acetone(Eq. (10)).
TiO2 e- + h+
4h+ + 2H2O O2 + 4H+
H+ + e- H
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
CO2 + e- CO2
CO-2 + 6H CH3OH + 2H2O
CO-2 + 4H HCOH + H2O
CH3OH +H CH3 + H2O
HCOH +H HC(OH)-H
CH3 + H -C(OH) -H C2H5OH
CH3OH + C2H5OH CH3COCH3 + 2H2O
4. Conclusion
In this study, Cu-N co-doped TiO2 and N doped TiO2 photocatalysts were prepared by sol-gel
method for CO2 photoreduction by water in liquid phase. All of the TiO2 samples were
crystallized basically in anatase phase. The TEM image revealed that the Cu0.6N4/TiO2 were
uniform spheroidal shape with agglomerate size of 9-12nm.The Cu0.6N4/TiO2 and N3/TiO2 catalyst
showed the maximum activity in photoreduction of CO2. When the N amount was 2wt% and
4wt%, the N doped and Cu-N co-doped TiO2 showed absorption in the UV region, However, when
the N amount was 6wt% the N doped and Cu-N co-doped TiO2 had good visible light absorption.
XPS analysis indicated that the doped nitrogen was in the state of molecularly chemisorbed
nitrogen. Acetone is the only hydrocarbon product in CO2 photoreduction over the TiO2 samples.
The acetone yield of N doped TiO2 higher than TiO2 and the optimum loading amount of N was
11
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
3wt%. However, the acetone yield of Cu-N co-doped TiO2 was lower than that of N doped TiO2
due to the bigger particle size and narrower band gap.
Acknowledge
This work was supported by the National Natural Science Foundation of China (21406164,
21466035), the National Key Basic Research and Development Program of China (973 program,
No. 2014CB239300, 2012CB720100), the Natural Science Foundation of Tianjin
(No.13JCQNJC05700), Research Fund for the Doctoral Program of Higher Education of
China(No.20130032120019)
12
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Reference
[1] C.M. White, B.R. Strazisar, E.J. Granite, Separation and capture of CO2 from large stationary
sources and sequestration in geological formations coal beds and deep saline aquifers, Journal
of Air＆Waste Management Association. 53 (2003) 645-715.
[2]M. Anpo,H. Yamashita,Y. Ichihashi, S. Ehara, Photocatalytic reduction of CO2 with H2O on
various titanium oxide catalysts, Journal of Electroanalytical Chemistry.396(1995) 21-26.
[3]M.Anpo, H.Yamashita, K.Ikeue, Y.Fujii, S.G.Zhang, Photocatalytic reduction of CO2 with
H2O on Ti-MCM-41 and Ti-MCM-48 mesoporous zeolite catalysts, Catalysis Today. 44
(1998) 327-332.
[4]Y.Kohno, H.Hayashi, S. Takenaka, T. Tanaka, T. Funabiki, S. Yoshida, Photo-enhanced
reduction of carbon dioxide with hydrogen over Rh/TiO2, Journal of photochemistry and
Photobiology A. 126 (1999) 117-123.
[5]Y. Kohno, T. Tanaka, T. Funabiki, S. Yoshida, Photoreduction of CO2 with H2 over ZrO2. A
study on interaction of hydrogen with photoexcited CO2, Physical Chemistry Chemical
Physics. 2 (2000) 2635-2639.
[6]Xiukai Li, Zongjin Zhuang, Wei Li, Huiqi. Pan, Photocatalytic reduction of CO2 over noble
metal loaded and nitrogen-doped mesoporous TiO2, Applied Catalysis A: General.429-430
(2012) 31- 38.
13
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
[7]I.H. Tseng, J.C.S. Wu, HY Chou, Effects of sol–gel procedures on the photocatalysis of
Cu/TiO2 in CO2 photoreduction , Journal of Catalysis. 221 (2004) 432–440.
[8]Kocí K, Obalová L,Matìjová L, Effect of TiO2 particle size on the photocatalytic reduction of
CO2 , Applied Catalysis B: Environmental.89(2009)494-502.
[9] P.L. Richardson, Marisa L.N, Perdigoto, W. Wang, Manganese-and copper-doped titania
nanocomposites for the photocatalytic reduction of carbon dioxide into methanol, Applied
Catalysis B: Environmental. 126 (2012) 200-207.
[10]I.H. Tseng, W.C. Chang, J.C.S. Wu, Photoreduction of CO2 using sol-gel derived titania and
titania-supported copper catalysts. Applied Catalysis B: Environmental. 37(2002) 37-48.
[11]I.H. Tseng, Jeffrey C.-S. Wu, Chemical states of metal-loaded titania in the photoreduction of
CO2, Catalysis Today. 97 (2004) 113-119.
[12]Zhang Q, Li Y, Ackerman EA, Gajdardziska-Josifovska M, Li H, Visible light responsive
iodine-doped TiO2 for photocatalytic reduction of CO2 to fuels, Applied Catalysis A
General.400(2011)195-202.
[13]Jun Fan, Enzhou Liu, Lei Tian, Synergistic Effect of N and Ni2+on nanotitania in
photocatalytic Reduction of CO2,Journal of Environmental Engineering. 137(2011)171-176.
[14]Dandan Lu, Min Zhang, Zhihua Zhang, Self-organized vanadium and nitrogen co-doped
titaniananotube arrays with enhanced photocatalytic reduction of CO2 into CH4 , Nanoscale
Research letter .9(2014)272.
14
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
[15]Kaixi Song, Jiahong Zhou, Jianchun Bao, Photocatalytic Activity of (Copper, Nitrogen)
co-doped Titanium Dioxide Nanoparticles, Journal of the American Ceramic Society.91[4]
(2008) 1369-1371.
[16]Chan-Soo Kim, Jung-Woo Shin, Young-Hyuck Cho, Synthesis and characterization of Cu/N
doped mesoporous TiO2 visible light photocatalysts, Applied Catalysis A: General. 455
(2013) 211-218.
[17]Alex T. Kuvarega, RuiW. M. Krause, Bhekie B. Mamba, Comparison between base metals
and platinum group metals in nitrogen, M Codoped TiO2 (M = Fe, Cu, Pd, Os) for
Photocatalytic Removal of an Organic Dye in Water, Journal of Nanomaterials.2014(2014)
[18] Oomman K. Varghese, Maggie Paulose, Thomas J. LaTempa, Craig A. Grimes, High-Rate
Solar Photocatalytic Conversion of CO2 and Water Vapor to Hydrocarbon Fuels, Nano Letters.
9(2009)731-737.
[19]S. Xu, W. Shangguan, J. Yuan, M. Chen, J. Shi, Preparations and photocatalytic properties
of magnetically separable nitrogen-doped TiO2 supported on nickel ferrite, Applied Catalysis.
B: Environmental. 71 (2007)177-184.
[20]G.S. Shao, F.Y. Wang, T.Z. Ren, Y. Liu, Hierarchical mesoporous phosphorus and nitrogen
doped titania materials: Synthesis, characterization and visible-light photocatalytic activity,
Applied Catalysis B: Environmental. 92 (2009) 61-67.
15
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
[21]L, Liu，C, Zhao, Y Li, Spontaneous dissociation of CO2 to CO on defective surface of
Cu(I)/TiO2 Nanoparticles at Room Temperature, Journal of Physical Chemistry C.116 (2012)
7904-7912.
[22]Guidong Yang, Ting Wang, Bolun Yang, Enhanced visible-light activity of F-N co-doped
TiO2 nanocrystals via nonmetal impurity, Ti3+ ions and oxygen vacancies, Applied Surface
Science.287 (2013) 135-142.
[23]Y. Gao, S.A. Elder, Shape control of nanostructured TiO2 using a Schiff base ligand via
sol-gel hydrothermal method, Journal of Sol-Gel Science Technology. 69 (2014)544-552.
[24] L.K˝orösi, I. Dékány, Preparation and investigation of structural and photocatalytic
properties of phosphate modified titanium dioxide, Colloids Surface A: General
Physicochemical and Engineering Aspects.280 (2006) 146-154.
[25]M.M. Joshi, N.K. Labhsetwar, P.A. Mangrulkar, S.N. Tijare, S.P. Kamble, S.S. Rayalu,
Visible light induced photoreduction of methyl orange by N-doped mesoporous titania,
Applied. Catalysis. A Genera.357 (2009) 26-33.
[26]R.Asahi, T.Morikawa,T. Ohwaki, K. Aoki, Y. Taga, Visible-Light Photocatalysis in
Nitrogen-Doped Titanium Oxides, Science .293 (2001) 269-271.
[27]Z. Wang, W. Cai, X. Hong, X. Zhao, F. Xu, C. Cai, Photocatalytic degradation of phenol in
aqueous nitrogen-doped TiO2 suspensions with various light sources, Applied Catalysis. B:
Environmental. 57 (2005)223-231.
16
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
[28]J. Yuan, M. Chen, J. Shi, W. Shang guan, Preparations and photocatalytic hydrogen
evolution of N-doped TiO2 from urea and titanium tetrachloride, International Journal of
Hydrogen Energy.31 (2006)1326-1331.
[29]M. Subrahmanyam , S. Kaneco. A screening for the photo reduction of carbon dioxide
supported on metal oxide catalysts for C1–C3 selectivity, Applied Catalysis B: Environmental.
23 (1999) 169-174.
[30]Tianyou Peng, Xiaohu Zhang，Effect of graphitic carbon nitride microstructures on the
activity and selectivity of photocatalytic of reduction CO2 under visible light, Catalysis
Science & Technology. 3 (2013) 1253-1260.
17
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Fig.1. XRD pattern of (a) Cu and N co-doped TiO2 -(1)TiO2 (2)Cu0.6/TiO2 (3)Cu0.6N2/TiO2
(4)Cu0.6N4/TiO2 (5)Cu0.6N6/TiO2 (b) N doped TiO2- (1)TiO2 (2)N2/TiO2 (3)N4/TiO2 (4) N6/TiO2
18
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Fig.2. FTIR pattern of (a) Cu and N co-doped TiO2 (b) N doped TiO2
19
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Fig.3. (a) TEM of Cu0.6N4/TiO2 (b) HRTEM image of Cu0.6N4/TiO2 with labeled lattice spacings
and surface facet for anatase (101) (c) EDX of Cu0.6N4/TiO2
20
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Fig.4. UV-vis of (a) Cu and N co-doped TiO2 (b) N-doped TiO2
21
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Fig.5. XPS spectra of Cu0.6N4/TiO2 and TiO2 (a) Survey spectrum and (b) peak fitting of N 1s
spectrum of Cu0.6N4/TiO2.
22
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Fig.6. Effect of N doping amount on acetone yield of Cu-N co-doped TiO2
23
ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Fig.7. Effect of N doping amount on acetone yield of N doped TiO2
24
ACCEPTED MANUSCRIPT