- Email: [email protected]
Synthesis and photocatalytic property of TiO2@V2O5 core-shell hollow porous microspheres towards gaseous benzene
Accepted Manuscript Synthesis and photocatalytic property of TiO2@V2O5 core-shell hollow porous microspheres towards gaseous benzene Yueli Liu, Linlin Wang, Wei Jin, Chao Zhang, Min Zhou, Wen Chen PII:
S0925-8388(16)32516-6
DOI:
10.1016/j.jallcom.2016.08.137
Reference:
JALCOM 38639
To appear in:
Journal of Alloys and Compounds
Received Date: 17 May 2016 Revised Date:
13 July 2016
Accepted Date: 16 August 2016
Please cite this article as: Y. Liu, L. Wang, W. Jin, C. Zhang, M. Zhou, W. Chen, Synthesis and photocatalytic property of TiO2@V2O5 core-shell hollow porous microspheres towards gaseous benzene, Journal of Alloys and Compounds (2016), doi: 10.1016/j.jallcom.2016.08.137. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Revision Manuscript for Journal of Alloys and Compounds Ref. No.: JALCOM-D-16-04616 Synthesis and photocatalytic property of TiO2@V2O5 core-shell
RI PT
hollow porous microspheres towards gaseous benzene Yueli Liu, Linlin Wang, Wei Jin, Chao Zhang, Min Zhou, Wen Chen*
SC
State Key Laboratory of Advanced Technology for Materials Synthesis and
M AN U
Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, P. R. China
Prof. Wen Chen
TE D
[*] Correspondent:
Tel.: +86-27-87651107
EP
Fax: +86-27-87760129
AC C
E-mail: [email protected] (Wen Chen)
ACCEPTED MANUSCRIPT
Abstract TiO2 hollow spheres are prepared by a template method, and TiO2@V2O5 core-shell hollow porous microspheres are successfully synthesized through a facile
RI PT
hydrothermal progress followed by sol-gel technique. The diameters of TiO2@V2O5 core-shell hollow porous microspheres are quite uniform ranging from 700 nm to 900 nm. It is found that the photodegradation rate of TiO2@V2O5 core-shell hollow porous
SC
microspheres towards benzene is greatly enhanced compared with that of TiO2 hollow
M AN U
porous microspheres and P25, and TiO2@V2O5-10% core-shell hollow porous microspheres possess the best photocatalytic activity of 100% in 55 min and 68.9% in 75 min under UV-visible and visible light irradiation, respectively. The reason lies in the fact that the light absorption range is extended due to the narrowed band gap of
TE D
TiO2@V2O5 core-shell hollow porous microspheres, and the photogenerated electrons and holes are effectively separated as well as the surface charge carrier transfer rate is promoted.
EP
Keywords: TiO2 hollow porous microspheres; TiO2@V2O5 core-shell; photocatalysis;
AC C
gaseous benzene
ACCEPTED MANUSCRIPT
1. Introduction Volatile organic compounds (VOCs) are the most harmful pollutants in air and result in outdoor and indoor air deterioration [1-3]. Among various VOCs, benzene is
RI PT
one of the carcinogenic and recalcitrant aromatic hydrocarbons in polluted urban atmosphere, which is regarded as a prior hazardous substance that requires highly efficient treatment technologies. For the VOCs removal, photocatalytic process is
SC
proved to be a promising technology [4-8]. For the photocatalysts, titanium dioxide
M AN U
(TiO2) is one of the most basic materials in our daily life, which shows great potential application as ideal and powerful photocatalysts for various significant reactions due to its special characters, such as low cost, readily available material, chemical stability, nontoxicity and high reactivity, and so on [9-16]. Nowadays, it is widely used to
TE D
remove both of organic and inorganic pollutants from various environmental media. Recently, TiO2 microspheres with high surface areas and abundant porous
EP
structures have stimulated much attention due to the high dispersion and large surface area, which give rise to a high light-harvesting, and they have been applied in
AC C
dye-sensitized solar cells [17] as well as photocatalytic degradation [18-20]. However, practical applications of TiO2 microspheres are still limited by their fast electron-hole recombination and wide band gap energy (3.2 eV), as they only absorb a small portion of solar spectrum in the UV light region, which is about 4% of the incoming solar light [21-24]. Therefore, it is essential to improve the photocatalytic properties of TiO2 microspheres in visible light region. Till now, many methods have been used to improve the utilization of solar
ACCEPTED MANUSCRIPT energy and reduce the recombination of photo-induced electron-hole pairs, such as chemical modification [9-14], surface sensitization [25] and coupling with other semiconductor materials [5, 7, 26, 27]. A considerable enhancement in the
RI PT
photocatalytic efficiency of TiO2 microspheres under visible light has been obtained by coupled with the semiconductors of low band gap. As an important transition metal-oxide semiconductor, V2O5 possesses relatively low band gap (about 2.3 eV),
SC
which may provide a capability of absorbing a broad solar spectrum. Therefore,
M AN U
TiO2@V2O5 composites are considered to be effective and practical catalyst for photocatalytic application. For example, Cha prepared V2O5@TiO2 nanoparticles catalysts by chemical vapor condensation (CVC) and impregnation methods with varied V2O5 concentrations, and the highest NOx conversion was observed by using 7
TE D
and 10 wt% V2O5@TiO2 catalysts [28]. Wang synthesized one-dimensional (1D) TiO2@V2O5 branched heterostructures catalysts, and their photodegradation rate of RhB under visible light is much faster than that of the pure TiO2 nanofibers [29].
EP
V2O5@TiO2 catalysts with different vanadium contents were prepared by wet
AC C
impregnation method, and the 3-5 wt% V2O5@TiO2 catalysts are best for the oxidation of chlorobenzene [30]. In the present work, TiO2 hollow porous microspheres are prepared by a template
method, and then TiO2@V2O5 core-shell hollow porous microspheres are successfully fabricated via a facile hydrothermal progress followed by sol-gel technique. The interactions between the core and shell material can drastically improve the overall performance of the core–shell nanostructure system and even create advantageous
ACCEPTED MANUSCRIPT synergetic effects, it is expected that TiO2@V2O5 core-shell hollow porous microspheres possess an enhanced photodegradation towards gaseous benzene, as the low band gap of V2O5 shell may enlarge the light absorption range of solar light and
RI PT
favor for the effective separation of photo-generated electrons and holes.
2. Experimental procedures
SC
Synthesis of TiO2 hollow porous microspheres: In our previous work, we have synthesized solid-cored TiO2 microspheres [31]. Similar to the synthesis process,
M AN U
TiO2 hollow spheres with nanosize were prepared by the template method. Firstly, polystyrene (PS) nanospheres were synthesized by emulsion polymerization, and monodisperse
PS
nanosphere
templates
with
electronegative
surface
and
homogeneous size were synthesized at 70 °C for 18 h. Secondly, 0.5 g of PS
TE D
nanospheres was dispersed in a mixed solution of absolute ethanol and acetonitrile (Vethanol/Vacetonitrile=3.0) with ultrasonic dispersing for 20 min, and then a certain
EP
amount of mass fraction of 27% aqueous ammonia was added. 3 mL tetrabutyl titanate and 0.2 g triethanolamine with 20 mL of anhydrous ethanol were mixed and
AC C
stirred until the solution became a clear solution, and a mixed solution of polystyrene mentioned above was dropwisely added with continuous stirring for 2 h. After the reaction, the resulting white precipitate was centrifuged, washed and then dried. Then PS@TiO2 was successfully synthesized. These core-shell particles were subsequently calcined to prepare well-defined TiO2 hollow porous microspheres (HPMs) with predetermined diameters. Synthesis of TiO2@V2O5 core-shell hollow porous microspheres: In our work,
ACCEPTED MANUSCRIPT various amounts (0.0572 g, 0.113 g and 0.169 g) of V2O5 powders were dissolved in 5 mL H2O2 solution, and 15 mL of deionized water was then added. V2O5 is dissolved in H2O2 to form a kind of coordination compound (V2O5·nH2O gels). V2O5 is
RI PT
dissolved in H2O2 to form a kind of coordination compound (V2O5·nH2O gels). When V2O5 is dissolved into H2O2, an unstable diperoxo [VO(O2)2]- is produced, which is then dissociated to monoperoxo [VO(O2)]+ and vanadate. After ‘a few hours’,
SC
decavanadic acid [HnV10O28](6-n) is produced. The decavanadic acid is slowly
M AN U
dissociated and undergone the polymerization to produce V2O5·nH2O gels, which favors for the dissolving of V2O5 solution [32].
After the reaction, 0.002 g sodium dodecyl sulfate (SDS) solution was added in the V2O5 sol solution. SDS is used as an anionic modifier, adding SDS in
TE D
V2O5-H2O2-H2O solution may enhance the surface activity of V2O5 solution, which is favorable for the coating of the V2O5 shell on the surface of TiO2 HPMs. 1 g TiO2 HPMs were dispersed in deionized water by adding 0.001 g hydroxypropyl cellulose
EP
(HPC). HPC is used as a bonding resin, which is also favorable for the coating of the
AC C
V2O5 shell on the surface of TiO2 HPMs, and then a good interface combination between V2O5 shell and TiO2 core may be formed. Then V2O5 sol was dropwisely added in the reaction solution containing TiO2 HPMs with stirring for a period with the temperature of 80 ℃. The samples were centrifuged, washed, dried, and finally calcined in a muffle furnace at 350℃to obtain TiO2@V2O5 core-shell HPMs, which were named to be TiO2@V2O5-5%, TiO2@V2O5-10% and TiO2@V2O5-15%, respectively, and the detailed parameters for the synthesis of TiO2@V2O5 core-shell
ACCEPTED MANUSCRIPT HPMs are listed in Table 1. Photocatalytic degradation of gaseous benzene: Photocatalytic decomposition of the benzene was carried out in a hermetic stainless steel chamber with the volume of 5
RI PT
L, and a lamp with the wavelength centered at 365 nm was installed on the bracket. The catalyst (0.5 g prepared sample) was dispersed as a thin layer over a glass vessel with the total area of 0.18 m2. The required quantity of benzene was injected into the
SC
reactor, and the initial concentration of benzene was kept at 370 mg/m3 for all
M AN U
experiments. Simultaneous concentration determination of benzene and carbon dioxide was performed with an online gas chromatograph equipped with a flame ionization detector.
Characterization: The samples were characterized by an X-ray diffractometer
TE D
(XRD D/MAX-III) using a Cu K radiation and graphite monochromator, Field emission scanning electron microscopy (FESEM) was carried out on a JEOL JSM-6330F microscope. X-ray photoelectron spectroscopy (XPS) measurements were
EP
performed on a VG Multilab 2000 multi-technique electron spectrometer using Al Kα
AC C
radiation as excitation source. UV-vis absorption spectrum was recorded on a UV-2550 UV-vis spectrophotometer. The Photocatalytic degradation of benzene was performed by a Gas Chromatography (GC-9560, Shanghai Chenhua Technology Corp., Ltd.)
3. Results and Discussion From the XRD patterns shown in Fig. 1, the diffraction peaks centered at 2θ=25.1°, 37.6°, 47.9°, 53.7°, 54.5° and 62.7° appear in the TiO2 sample, which
ACCEPTED MANUSCRIPT agrees well with the crystal planes of anatase TiO2 phase (JCPDS No. 21-1272). For the sample of pure V2O5, there are some diffraction peaks centered 2θ=15.3°, 20.3°, 21.7°, 25.6° and 31.0°, which are assigned to V2O5 phase (JCPDS No. 41-1426).
RI PT
However, the XRD patterns of the samples of TiO2@V2O5-5%, TiO2@V2O5-10% and TiO2@V2O5-15% only possess the diffraction peaks of the anatase TiO2 phase without the diffraction peaks of V2O5 phase, and it indicates that a very thin layer of V2O5
M AN U
detection of V2O5 phase in the XRD patterns.
SC
shells is uniformly dispersed onto the surface of TiO2 HPMs, which may induce no
SEM image proves the hollow structure of the sample shown in Fig. 2(a), and it is found that the microspheres diameter is quite uniform ranging from 700 nm to 900 nm. From the broken microspheres, it is found that TiO2 HPMs are composed of a
TE D
thin layer of TiO2 nanoparticles. From the SEM images in Fig. 2(b-d), the diameters of the TiO2@V2O5 core-shell HPMs are also uniform, and there is no change compared with that of TiO2 HPMs in Fig. 2(a). However, the surface of TiO2@V2O5
EP
core-shell HPMs becomes much rough, and the very small nanoparticles in the
AC C
surface should be vanadium pentoxide. Moreover, the surface chemical composition of the TiO2@V2O5-10% core-shell HPMs is further determined by energy dispersive X-ray (EDX) measurement as described in Fig. 2(e). EDX pattern demonstrates that the TiO2@V2O5 core-shell HPMs are mainly composed of titanium (Ti), oxygen (O), carbon (C) and vanadium (V) elements, which proves the existence of vanadium. The detailed microstructure characteristics of the TiO2 HPMs and TiO2@V2O5 core-shell HPMs are further tested by TEM measurement. From the TEM image in
ACCEPTED MANUSCRIPT Fig. 3(a), it can be seen that the diameter of TiO2 HPMs is of about 700nm, and the lattice distance of 0.365nm corresponds to (101) crystal plane of TiO2 phase from the inset HRTEM image shown in Fig. 3(a). It is found that TiO2 HPMs are composed of
RI PT
a thin layer of TiO2 nanoparticles, and the diameters of the TiO2 nanoparticles are in the range from 20 nm to 50 nm, which is in good agreement with the SEM image in Fig. 2(a). From the TEM images in Fig. 3(b) and 3(c), the diameter of TiO2@V2O5
SC
core-shell HPMs is about 700-900nm. From the selected-area electron diffraction
M AN U
(SAED) pattern in Fig. 3(d), it can be seen that there are two kinds of the diffraction rings, one of them is assigned to be (101) and (103) crystal planes of anatase TiO2 phase, another belongs to the (600) and (402) crystal planes of V2O5 phase, which further proves the coexistence of the polycrystalline structure of the TiO2 and V2O5 in
TE D
the TiO2@V2O5 core-shell HPMs.
XPS spectra are used to investigate the chemical state of TiO2 HPMs and TiO2@V2O5 core-shell HPMs, as shown in Fig. 4, which reveals that the TiO2 HPMs
EP
contain three elements of Ti, O and C in XPS survey spectrum in Fig. 4(a), while the
AC C
V element appears in the in XPS survey spectrum of TiO2@V2O5 core-shell HPMs. Ti 2p spectra in Fig. 4(b) show that 2p1/2 peak of Ti element locates at 464.26 eV, and there is no obvious shift in the peak position after the formation of TiO2@V2O5 core-shell HPMs [33, 34]. Generally, the O 1s peak at 529.77 eV is assigned to the Ti–O bonds, and the peak at 530.5 eV is a signal of the V–O bonds for V2O5, while the peak at 531.69 eV is related to the surface-adsorbed hydroxide (OH) as shown in Fig. 4(c) [34-36],
ACCEPTED MANUSCRIPT which is physically adsorbed on the surface due to their unique microspheres-like structure and high surface area. For the pure TiO2 HPMs, only two peaks with the binding energies of 529.77 eV and 531.69 eV coexist. While for TiO2@V2O5
RI PT
core-shell HPMs, three peaks with the binding energies of 529.75 eV, 530.54 eV and 531.79 eV coexist, which implies the existence of V2O5 in TiO2@V2O5 core-shell HPMs. Most interesting, there are no obvious peak shift for the peak of
SC
surface-adsorbed hydroxide (OH) at 531.79 eV, however, the relative intensity of the
M AN U
peak of adsorbed oxygen (531.79 eV) to the peaks of lattice oxygen (529.75 eV and 530.54 eV) increases from 1:3.67 to 1:1.76 after the formation of TiO2@V2O5 core-shell HPMs, which partially originates from the deposition of V2O5 shells as well as the increasing of the surface-adsorbed hydroxide. It is well known that the
TE D
adsorbed hydroxide species are quite important for the process of photocatalytic reaction, as it may produce hydroxyl radical (OH) by capturing the photo-induced electrons, which favors for the oxidizing of the organic materials and the oxidizing
EP
hydroxylating reaction products as the oxidant [29, 38, 39]. Therefore, the increasing
AC C
of the hydroxide absorption in TiO2@V2O5 core-shell HPMs will favor for their photocatalytic reaction, as the physical absorption ability of hydroxide species not only enhances the separation efficiency of photo-induced electrons and holes, but also promotes the fast transfer of photo-induced electrons to the adsorbed hydroxide species. The binding energies at 524.8 eV and 517.7 eV correspond to V 2p1/2 and V 2p3/2 in Fig. 4(d), respectively, which is related to V5+ oxidation state, and it further improves the existence of V2O5 in the TiO2@V2O5 core-shell HPMs [33, 34].
ACCEPTED MANUSCRIPT UV-vis spectra are used to character the optical absorption of all samples in the wavelength range of 300-800 nm in Fig. 5. It shows that the absorption edges of all TiO2@V2O5 core-shell HPMs will shift to the visible light range compared with that
RI PT
of TiO2 HPMs, which is related to the narrowing band gap by the modification of V2O5 shells. Moreover, TiO2@V2O5 core-shell HPMs possess an obvious enhancement for light absorption ability in the range of UV and visible light
SC
compared with that of TiO2 HPMs and P25. For all of the TiO2@V2O5 core-shell
M AN U
HPMs, the TiO2@V2O5-10% core-shell HPMs achieve the highest optical absorption intensity. The reason lies in the fact that the oxygen vacancies formed during the synthesis process may capture the electrons, which has an important effect on the light absorption [14, 39].
TE D
By choosing the photo-degradation of gaseous benzene as reference materials, the potential photocatalytic properties of TiO2 HPMs and TiO2@V2O5 core-shell HPMs with various V2O5 contents are investigated, respectively. The conversion
EP
between the benzene concentration and the concentration of the produced CO2 gas
AC C
acts as a function of irradiation time, as shown in Fig. 6 and Fig. 7. As shown in Fig. 6, for P25 and V2O5 powder, the removal rate of gaseous benzene is only 74.3% and 27.8% under UV-vis light irradiation, respectively. It is found that no benzene signal is detected after 70 min reaction for TiO2 HPMs, and it exhibits an enhanced removal rate than that of P25, which is attributed to the three-dimensional (3D) architectures of TiO2 HPMs. The 3D architectures of TiO2 HPMs have excellent and attractive performances due to the large interfacial contact areas with gaseous benzene.
ACCEPTED MANUSCRIPT Moreover, it is found that the photocatalytic performance will be enhanced by the formation of TiO2@V2O5 core-shell HPMs. It is found that gaseous benzene is totally photodegraded to be CO2 and H2O in 55 min for the TiO2@V2O5-10% core-shell
RI PT
HPMs, and the produced CO2 concentration is of 1293 ppm in Fig. 6, which corresponds to a high mineralization ratio ([CO2]produced/[C6H6]converted) of 5.5. Such high ratio suggests that about 91.7% of converted-benzene is completely mineralized
SC
to CO2 and H2O, and the other 8.3% of converted-benzene may be degraded to some
formaldehyde [23, 30].
M AN U
kinds of incompletely decomposed compounds, such as CO, acthaldehyde and
Meanwhile, too excessive V2O5 contents (15%) will reduce the photocatalytic properties, and the gaseous benzene is totally photodegraded in 65 min. The reason
TE D
may lies in the fact that TiO2 cores plays a dominant factor for the photodegradation of gaseous benzene, and the effect of V2O5 shells is to extend the light absorption range and then enhance the light absorption, as proved by UV-vis spectra in Fig. 5.
EP
Therefore, too excessive V2O5 loading will cover a large surface of TiO2 HPMs, and it
AC C
may decrease the contact areas with gaseous benzene as well as inhibit the interfacial absorption spectrum of TiO2 HPMs due to the shading effect [28, 30, 40]. At the same time, for pure V2O5 nanoparticles, the removal rate of gaseous
benzene is only 31.8% under visible light irradiation shown in Fig. 7, which indicates that the pure V2O5 powder have a poor photocatalytic activity towards gaseous benzene. It is also found that P25 and TiO2 HPMs have almost no photodegradation towards gaseous benzene under visible light irradiation, as it is well known that the
ACCEPTED MANUSCRIPT conventional TiO2 is photoactivated mostly upon UV irradiation (light wavelength <400 nm) in order to overcome its wide band gap energy (3.2 eV). Obviously, under visible light irradiation the photodegradation efficiencies of P25 and TiO2 HPMs are low.
However,
TiO2@V2O5
core-shell
HPMs
show
a
higher
RI PT
relatively
photodegradation activity than either P25, TiO2 HPMs or pure V2O5, especially for TiO2@V2O5-10%, the removal rate of gaseous benzene is 68.9% in 75 min. The result
SC
should be mainly attributed to the coupling of TiO2 cores with V2O5 shells may
M AN U
promote the photodegradation activity, and the TiO2@V2O5 interface plays a crucial role in the gaseous benzene photodegradation reaction.
It is well known that a typical junction barrier at the interface between V2O5 shells and TiO2 cores will be formed, as the heterojunctions will suppress the recombination
TE D
of electron-hole pairs in TiO2@V2O5 core-shell HPMs, where the V2O5 shells act as an efficient electron traps aiding electron-hole separation. The possible mechanism of the heterojunctions can be understood through the energy band diagram of the
EP
heterojunctions as shown in Fig. 8. Under UV-visible light irradiation, the absorption
AC C
of a photon with energy larger than the band gap of the semiconductor can induce the electron transition from the valence band (VB) to the conduction band (CB) of V2O5 shells and TiO2 cores, and then the photoexcited electrons migrate and are collected to the CB of V2O5 shells, leaving holes in the VB of TiO2 cores [4, 7, 40]. Therefore, the photogenerated electrons and holes can be separated efficiently at the interface, and the chemical binding interface of TiO2@V2O5 core-shell HPMs is also favorable for the effective separation of photoexcited electrons and holes in our
ACCEPTED MANUSCRIPT case. The increasing of the charge separation of the photogenerated electrons and holes allows both of the photo-generated electrons and holes to initiate redox reactions with molecular species adsorbed on the surfaces of the composite catalysts.
RI PT
The photogenerated holes can react with surface adsorbed H2O molecules to produce •OH radicals, while the photoexcited electrons are usually scavenged by O2 to yield superoxide radical anions •O2-, which can degrade gaseous benzene efficiently. In
SC
addition, the large surface area of TiO2@V2O5 core-shell HPMs is favorable for the
M AN U
adsorption of benzene molecules due to their porous structure. For a large amount of benzene molecules absorbed on the surface, it becomes easy for the pollutants to react with the generated active species (•OH and •O2-), and this may be an important reason
4. Conclusions
TE D
for the high activity of the TiO2@V2O5 core-shell HPMs [18, 41].
In summary, three-dimensional (3D) architectures of TiO2 HPMs are successfully
EP
synthesized, and then TiO2@V2O5 core-shell HPMs are formed by hydrothermal progress together with sol-gel technique. Hollow microspheres with high surface
AC C
areas and abundant porous structures are beneficial to the large interfacial contact areas with gaseous benzene. It is found that TiO2@V2O5 core-shell HPMs have been proven to show a superior photocatalytic activity compared to pure TiO2 HPMs, P25 and V2O5 nanoparticles. In particular, TiO2@V2O5-10% core-shell HPMs presents the best photodegradation efficiency of 100% in 55 min and 68.9% in 75 min under UV-visible and visible light irradiation, respectively. However, too excessive V2O5 contents (15%) will reduce the photocatalytic properties, and the gaseous benzene is
ACCEPTED MANUSCRIPT totally photodegraded in 65 min. The reason may lies in the fact that TiO2 cores plays a dominant factor for the photodegradation of gaseous benzene, and the effect of V2O5 shells is to extend the light absorption to visible light range and then enhance the light Moreover, the well-formed interface between V2O5 shells and TiO2
RI PT
absorption.
cores may suppress the recombination of electron-hole pairs in TiO2@V2O5 core-shell HPMs, and the photogenerated electrons and holes can be separated efficiently at the
SC
interface, which may greatly enhance the photodegradation performance. While too
M AN U
excessive V2O5 loading will cover a large surface of TiO2 HPMs, and it may decrease the contact areas with gaseous benzene as well as inhibit the interfacial absorption spectrum of TiO2 HPMs due to the shading effect.
Acknowledgements
TE D
This work is supported by Equipment pre-research project (No. 625010402), National Nature Science Foundation of China (51506155), Science and Technology Support Program of Hubei Province (No. 2014BAA096), the Nature Science
EP
Foundation of Hubei Province (No. 2014CFB165), and the Key Laboratory of
AC C
Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province (No. GD201402). Thanks for the measurements supporting from Center for Materials Research and Analysis at Wuhan University of Technology (WUT).
ACCEPTED MANUSCRIPT
References [1] S. Ge, H. X. Zheng, Y. F. Sun, Z. Jin, J. H. Shan, C. Wang, H. Wu, M. Q. Li, F. L. Meng, J. Alloys Compd. 659 (2016) 127-131.
RI PT
[2] H. B. Huang, H. L. Huang, L. Zhang, P. Hu, X. G. Ye, D. Y. C. Leung, Chem. Eng. J. 259 (2015) 534-541.
[3] S. Weon, W. Choi, Environ. Sci. Technol. 50 (2016) 2556-2563.
SC
[4] X. B. Chen, S. H. Shen, L. J. Guo, S. S. Mao, Chem. Rev. 110 (2010) 6503-6570.
M AN U
[5] R. M. Mohamed, I. A. Mkhalid, J. Alloys Compd. 501 (2010) 143-147. [6] F. Y. Jing, D. Z. Zhang, F. Li, J. G. Zhou, D. M. Sun, S. P. Ruan, J. Alloys Compd. 650 (2015) 97-101.
[7] C. M. Teh, A. R. Mohamed, J. Alloys Compd. 509 (2011) 1648-1660.
[9] S.
Ivanov,
A.
TE D
[8] A. I. Hochbaum, P. D. Yang, Chem. Rev. 110 (2010) 527-546. Barylyak,
K.
Besaha,
A.
Bund,
Y.
Bobitski,
R.
Wojnarowska-Nowak, I. Yaremchuk, M. Kus-Liśkiewicz, Nanoscale Res. Lett.
EP
11 (2016) 1-12.
AC C
[10] K. Pathakoti, S. Morrow, C. Han, M. Pelaez, X. J. He, D. D. Dionysiou, H. M. Hwang, Environ. Sci. Technol. 47 (2013) 9988-9996.
[11] M. Hamadanian, A. Reisi-Vanani, A. Majedi. Appl. Surf. Sci. 256 (2010) 1837-1844.
[12] L. G. Devi, R. Kavitha, Appl. Catal. B 140 (2013) 559-587. [13] S. Izadyar, S. Fatemi, Ind. Eng. Chem. Res. 52 (2013) 10961-10968.
ACCEPTED MANUSCRIPT [14] Y. L. Liu, G. J. Yang, H. Zhang, Y. Q. Cheng, K. Q. Chen, Z. Y. Peng, W. Chen, RSC Adv. 4 (2014) 24363-24368. [15] Y. L. Liu, W. Shu, Z. Y. Peng, K. Q. Chen, W. Chen, Catal. Today 208 (2013)
RI PT
28-33. [16] Y. L. Liu, Y. Q. Cheng, W. Shu, Z. Y. Peng, K. Q. Chen, J. Zhou, W. Chen, G. S. Zakharova, Nanoscale 6 (2014) 6755-6762.
Liu, Y. K. Liu, C. Y. Luan, H. Cheng, Y. Y. Li, L.
SC
[17] H. E. Wang, L. X. Zheng, C. P.
M AN U
Martinu, J.A. Zapien, I. Bello. J. Phys. Chem. C 115 (2011) 10419-10425. [18] Y. Yang, G. Z. Wang, Q. Deng, H. L. Ng. Dickon, H. J. Zhao. ACS Appl. Mater. Interfaces 6 (2014) 3008-3015.
[19] C. L. Yu, J. C. Yu, M. Chan. J. Solid State Chem. 182 (2009) 1061-1069.
TE D
[20] H. Y. Yin, X. L. Wang, L. Wang, Q. L. Nie, Y. Zhang, Q. L. Yuan, W. W. Wu, J. Alloys Compd. 657 (2016) 44-52.
[21] H. J. Yan, H. X. Yang. J. Alloys Compd. 509 (2011) L26-L29.
EP
[22] J. G. Tao, T. Luttrell, M. Batzill, Nat. Chem. 3 (2011) 296-300.
AC C
[23] Y. L. Liu, W. Shu, K. Q. Chen, Z. Y. Peng, W. Chen, ACS Catal. 2 (2012) 2557-2565.
[24] Y. D. Liu, F. Xin, F. M. Wang, S. X. Luo, X. H. Yin, J. Alloys Compd. 498 (2010) 179-184.
[25] H. Park, Y. Park, W. Kim, W. Choi, J. Photoch. Photobio. C 15 (2013) 1-20. [26] J. Zhang, W. Fu, J. H. Xi, H. He, S. C. Zhao, H. W. Lu, Z. G. Ji, J. Alloys Compd. 575 (2013) 40-47.
ACCEPTED MANUSCRIPT [27] W. Shu, Y. L. Liu, Z. Y. Peng, K. Q. Chen, C. Zhang, W. Chen, J. Alloys Compd. 563 (2013) 229-233. [28] W. Cha, S. Chin, E. Park, S. T. Yun, J. Jurng, Appl. Catal. B 140 (2013) 705-715.
Nanotechnology 22 (2011) 225702.
RI PT
[29] Y. Wang, Y. R. Su, L. Qiao, L. X. Liu, Q. Su, C. Q. Zhu, X. Q. Liu,
[30] J. Wang, X. Wang, X. L. Liu, J. L. Zeng, Y. Y. Guo, T. Y. Zhu, J. Mol. Catal.
SC
A-Chem. 402 (2015) 1-9.
M AN U
[31] J. J. Du, W. Chen, C. Zhang, Y. L. Liu, C. X. Zhao, Y. Dai, Chem. Eng. J. 170 (2011) 53-58.
[32] B. Alonso and J. Livage, J. Solid State Chem. 148 (1999)16-19. [33] J. L. G. Fierro, L. A. Arrua, J. M. L. Nieto, G. Kremenic, Appl. Catal. 37 (1988)
TE D
323-338.
[34] J. L. Ong, L. C. Lucas, G. N. Raikar, J. C. Gregory, Appl. Surf. Sci. 72 (1993) 7-13.
EP
[35] V. I. Nefedov, M. N. Firsov, I. S. Shaplygin, J. Electron Spectrosc. Relat. Phenom.
AC C
26 (1982) 65-70.
[36] P. R. Moses, L. M. Wier, J. C. Lennox, H. O. Finklea, F. R. Lenhard, R. W. Murray, Anal. Chem. 50 (1978) 576-581.
[37] A. Mills, S. L. Hunte, J. Photoch. Photobio. A 108 (1997) 1-35. [38] D. Chatterjee, S. Dasgupta, J. Photoch. Photobio. C 6 (2005) 186-205. [39] J. S. Dalton, P. A. Janes, N. G. Jones, J. A. Nicholson, K. R. Hallam, G. C. Allen, Environ. Pollut. 120 (2002) 415–422.
ACCEPTED MANUSCRIPT [40] J. Su, X. X. Zou, G. D. Li, X. Wei, C. Yan, Y. N. Wang, J. Zhao, L. J. Zhou, J. S. Chen, J. Phys. Chem. C 115 (2011) 8064-8071. [41] Y. M. Lin, D. Z. Li, J. H. Hu, G. C. Xiao, J. X. Wang, W. J. Li, X. Z. Fu, J. Phys.
AC C
EP
TE D
M AN U
SC
RI PT
Chem. C 116 (2012) 5764-5772.
ACCEPTED MANUSCRIPT Figure Captions Table 1 Synthesis parameters of TiO2@V2O5 core-shell hollow porous microspheres Fig. 1 XRD patterns of the samples.
RI PT
Fig. 2 SEM images of samples: (a) Pure TiO2 HPMs; (b) TiO2@V2O5-5% core-shell HPMs; (c) TiO2@V2O5-10% core-shell HPMs; (d) TiO2@V2O5-15% core-shell HPMs; (e) EDX pattern of TiO2@V2O5-10% core-shell HPMs.
SC
Fig. 3 (a) TEM images and HRTEM images of the pure TiO2 HPMs; (b, c) TEM
M AN U
images and (d) SAED pattern of TiO2@V2O5 core-shell HPMs.
Fig. 4 XPS spectra of TiO2 HPMs and TiO2@V2O5 core-shell HPMs: (a) Survey spectra; (b) Ti 2p spectra; (c) O 1s spectra; (d) V 2p spectrum.
Fig. 5 UV-vis spectra of TiO2 HPMs and TiO2@V2O5 core-shell HPMs.
TE D
Fig. 6 The photocatalytic performance of P25, pure TiO2 HPMs and TiO2@V2O5 core-shell HPMs under UV-vis light irradiation: (a) Plots of the decreasing in benzene concentration vs. irradiation time; (b) plots of the increasing in CO2 concentration vs.
EP
irradiation time.
AC C
Fig. 7 The photocatalytic performance of P25, pure TiO2 HPMs and TiO2@V2O5 core-shell HPMs under visible light irradiation: (a) Plots of the decreasing in benzene concentration vs. irradiation time; (b) plots of the increasing in CO2 concentration vs. irradiation time.
Fig. 8 Energy band diagram of TiO2@V2O5 core-shell HPMs.
RI PT
ACCEPTED MANUSCRIPT
Table 1 Synthesis parameters of TiO2@V2O5 core-shell hollow porous microspheres
V 2O 5
0.0572 g
1g
M AN U
1g
AC C
EP
TE D
TiO2 HPMs
TiO2@V2O5-10%
TiO2@V2O5-15%
SC
TiO2@V2O5-5%
0.1130 g
1g 0.1690 g
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
Fig. 1 XRD patterns of the samples.
ACCEPTED MANUSCRIPT
(a)
500 nm
500 nm
(c)
M AN U
(d)
SC
200 nm
200 nm
200 nm
RI PT
(b)
200 nm
500 nm
TE D
500 nm
AC C
EP
(e)
Fig. 2 SEM images of samples: (a) Pure TiO2 HPMs; (b) TiO2@V2O5-5% core-shell HPMs; (c) TiO2@V2O5-10% core-shell HPMs; (d) TiO2@V2O5-15% core-shell HPMs; (e) EDX pattern of TiO2@V2O5-10% core-shell HPMs.
(b)
(a) 0.365 (101)
M AN U
SC
3nm
RI PT
ACCEPTED MANUSCRIPT
500 nm
100nm
(c)
TiO2 (103)
TiO2 (101) V2O5 (402)
EP
100 nm
TE D
(d)
V2O5 (600)
AC C
Fig. 3 (a) TEM images and HRTEM images of the pure TiO2 HPMs; (b, c) TEM (b) images and (d) SAED pattern of TiO2@V2O5 core-shell HPMs.
(b)
M AN U
SC
(a)
RI PT
ACCEPTED MANUSCRIPT
(c)
EP
TE D
(d)
AC C
Fig. 4 XPS spectra of TiO2 HPMs and TiO2@V2O5 core-shell HPMs: (a) Survey spectra; (b) Ti 2p spectra; (c) O 1s spectra; (d) V 2p spectrum.
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
Fig. 5 UV-vis spectra of TiO2 HPMs and TiO2@V2O5 core-shell HPMs.
ACCEPTED MANUSCRIPT
M AN U
SC
RI PT
(a)
AC C
EP
TE D
(b)
Fig. 6 The photocatalytic performance of P25, pure TiO2 HPMs and TiO2@V2O5
core-shell HPMs under UV-vis light irradiation: (a) Plots of the decreasing in benzene concentration vs. irradiation time; (b) plots of the increasing in CO2 concentration vs. irradiation time.
ACCEPTED MANUSCRIPT
M AN U
SC
RI PT
(a)
AC C
EP
TE D
(b)
Fig. 7 The photocatalytic performance of P25, pure TiO2 HPMs and TiO2@V2O5
core-shell HPMs under visible light irradiation: (a) Plots of the decreasing in benzene concentration vs. irradiation time; (b) plots of the increasing in CO2 concentration vs. irradiation time.
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
Fig. 8 Energy band diagram of TiO2@V2O5 core-shell HPMs
ACCEPTED MANUSCRIPT Research highlights 1) TiO2@V2O5 core-shell hollow porous microspheres (HPMs) are successfully
RI PT
synthesized
2) Photodegradation rate of TiO2@V2O5 core-shell HPMs towards benzene is greatly enhanced
SC
3) Light absorption range of TiO2@V2O5 core-shell HPMs is extended due to the
M AN U
narrowed band gap
4) The photogenerated electrons and holes are effectively separated for TiO2@V2O5
AC C
EP
TE D
core-shell HPMs
S0925-8388(16)32516-6
DOI:
10.1016/j.jallcom.2016.08.137
Reference:
JALCOM 38639
To appear in:
Journal of Alloys and Compounds
Received Date: 17 May 2016 Revised Date:
13 July 2016
Accepted Date: 16 August 2016
Please cite this article as: Y. Liu, L. Wang, W. Jin, C. Zhang, M. Zhou, W. Chen, Synthesis and photocatalytic property of TiO2@V2O5 core-shell hollow porous microspheres towards gaseous benzene, Journal of Alloys and Compounds (2016), doi: 10.1016/j.jallcom.2016.08.137. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Revision Manuscript for Journal of Alloys and Compounds Ref. No.: JALCOM-D-16-04616 Synthesis and photocatalytic property of TiO2@V2O5 core-shell
RI PT
hollow porous microspheres towards gaseous benzene Yueli Liu, Linlin Wang, Wei Jin, Chao Zhang, Min Zhou, Wen Chen*
SC
State Key Laboratory of Advanced Technology for Materials Synthesis and
M AN U
Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, P. R. China
Prof. Wen Chen
TE D
[*] Correspondent:
Tel.: +86-27-87651107
EP
Fax: +86-27-87760129
AC C
E-mail: [email protected] (Wen Chen)
ACCEPTED MANUSCRIPT
Abstract TiO2 hollow spheres are prepared by a template method, and TiO2@V2O5 core-shell hollow porous microspheres are successfully synthesized through a facile
RI PT
hydrothermal progress followed by sol-gel technique. The diameters of TiO2@V2O5 core-shell hollow porous microspheres are quite uniform ranging from 700 nm to 900 nm. It is found that the photodegradation rate of TiO2@V2O5 core-shell hollow porous
SC
microspheres towards benzene is greatly enhanced compared with that of TiO2 hollow
M AN U
porous microspheres and P25, and TiO2@V2O5-10% core-shell hollow porous microspheres possess the best photocatalytic activity of 100% in 55 min and 68.9% in 75 min under UV-visible and visible light irradiation, respectively. The reason lies in the fact that the light absorption range is extended due to the narrowed band gap of
TE D
TiO2@V2O5 core-shell hollow porous microspheres, and the photogenerated electrons and holes are effectively separated as well as the surface charge carrier transfer rate is promoted.
EP
Keywords: TiO2 hollow porous microspheres; TiO2@V2O5 core-shell; photocatalysis;
AC C
gaseous benzene
ACCEPTED MANUSCRIPT
1. Introduction Volatile organic compounds (VOCs) are the most harmful pollutants in air and result in outdoor and indoor air deterioration [1-3]. Among various VOCs, benzene is
RI PT
one of the carcinogenic and recalcitrant aromatic hydrocarbons in polluted urban atmosphere, which is regarded as a prior hazardous substance that requires highly efficient treatment technologies. For the VOCs removal, photocatalytic process is
SC
proved to be a promising technology [4-8]. For the photocatalysts, titanium dioxide
M AN U
(TiO2) is one of the most basic materials in our daily life, which shows great potential application as ideal and powerful photocatalysts for various significant reactions due to its special characters, such as low cost, readily available material, chemical stability, nontoxicity and high reactivity, and so on [9-16]. Nowadays, it is widely used to
TE D
remove both of organic and inorganic pollutants from various environmental media. Recently, TiO2 microspheres with high surface areas and abundant porous
EP
structures have stimulated much attention due to the high dispersion and large surface area, which give rise to a high light-harvesting, and they have been applied in
AC C
dye-sensitized solar cells [17] as well as photocatalytic degradation [18-20]. However, practical applications of TiO2 microspheres are still limited by their fast electron-hole recombination and wide band gap energy (3.2 eV), as they only absorb a small portion of solar spectrum in the UV light region, which is about 4% of the incoming solar light [21-24]. Therefore, it is essential to improve the photocatalytic properties of TiO2 microspheres in visible light region. Till now, many methods have been used to improve the utilization of solar
ACCEPTED MANUSCRIPT energy and reduce the recombination of photo-induced electron-hole pairs, such as chemical modification [9-14], surface sensitization [25] and coupling with other semiconductor materials [5, 7, 26, 27]. A considerable enhancement in the
RI PT
photocatalytic efficiency of TiO2 microspheres under visible light has been obtained by coupled with the semiconductors of low band gap. As an important transition metal-oxide semiconductor, V2O5 possesses relatively low band gap (about 2.3 eV),
SC
which may provide a capability of absorbing a broad solar spectrum. Therefore,
M AN U
TiO2@V2O5 composites are considered to be effective and practical catalyst for photocatalytic application. For example, Cha prepared V2O5@TiO2 nanoparticles catalysts by chemical vapor condensation (CVC) and impregnation methods with varied V2O5 concentrations, and the highest NOx conversion was observed by using 7
TE D
and 10 wt% V2O5@TiO2 catalysts [28]. Wang synthesized one-dimensional (1D) TiO2@V2O5 branched heterostructures catalysts, and their photodegradation rate of RhB under visible light is much faster than that of the pure TiO2 nanofibers [29].
EP
V2O5@TiO2 catalysts with different vanadium contents were prepared by wet
AC C
impregnation method, and the 3-5 wt% V2O5@TiO2 catalysts are best for the oxidation of chlorobenzene [30]. In the present work, TiO2 hollow porous microspheres are prepared by a template
method, and then TiO2@V2O5 core-shell hollow porous microspheres are successfully fabricated via a facile hydrothermal progress followed by sol-gel technique. The interactions between the core and shell material can drastically improve the overall performance of the core–shell nanostructure system and even create advantageous
ACCEPTED MANUSCRIPT synergetic effects, it is expected that TiO2@V2O5 core-shell hollow porous microspheres possess an enhanced photodegradation towards gaseous benzene, as the low band gap of V2O5 shell may enlarge the light absorption range of solar light and
RI PT
favor for the effective separation of photo-generated electrons and holes.
2. Experimental procedures
SC
Synthesis of TiO2 hollow porous microspheres: In our previous work, we have synthesized solid-cored TiO2 microspheres [31]. Similar to the synthesis process,
M AN U
TiO2 hollow spheres with nanosize were prepared by the template method. Firstly, polystyrene (PS) nanospheres were synthesized by emulsion polymerization, and monodisperse
PS
nanosphere
templates
with
electronegative
surface
and
homogeneous size were synthesized at 70 °C for 18 h. Secondly, 0.5 g of PS
TE D
nanospheres was dispersed in a mixed solution of absolute ethanol and acetonitrile (Vethanol/Vacetonitrile=3.0) with ultrasonic dispersing for 20 min, and then a certain
EP
amount of mass fraction of 27% aqueous ammonia was added. 3 mL tetrabutyl titanate and 0.2 g triethanolamine with 20 mL of anhydrous ethanol were mixed and
AC C
stirred until the solution became a clear solution, and a mixed solution of polystyrene mentioned above was dropwisely added with continuous stirring for 2 h. After the reaction, the resulting white precipitate was centrifuged, washed and then dried. Then PS@TiO2 was successfully synthesized. These core-shell particles were subsequently calcined to prepare well-defined TiO2 hollow porous microspheres (HPMs) with predetermined diameters. Synthesis of TiO2@V2O5 core-shell hollow porous microspheres: In our work,
ACCEPTED MANUSCRIPT various amounts (0.0572 g, 0.113 g and 0.169 g) of V2O5 powders were dissolved in 5 mL H2O2 solution, and 15 mL of deionized water was then added. V2O5 is dissolved in H2O2 to form a kind of coordination compound (V2O5·nH2O gels). V2O5 is
RI PT
dissolved in H2O2 to form a kind of coordination compound (V2O5·nH2O gels). When V2O5 is dissolved into H2O2, an unstable diperoxo [VO(O2)2]- is produced, which is then dissociated to monoperoxo [VO(O2)]+ and vanadate. After ‘a few hours’,
SC
decavanadic acid [HnV10O28](6-n) is produced. The decavanadic acid is slowly
M AN U
dissociated and undergone the polymerization to produce V2O5·nH2O gels, which favors for the dissolving of V2O5 solution [32].
After the reaction, 0.002 g sodium dodecyl sulfate (SDS) solution was added in the V2O5 sol solution. SDS is used as an anionic modifier, adding SDS in
TE D
V2O5-H2O2-H2O solution may enhance the surface activity of V2O5 solution, which is favorable for the coating of the V2O5 shell on the surface of TiO2 HPMs. 1 g TiO2 HPMs were dispersed in deionized water by adding 0.001 g hydroxypropyl cellulose
EP
(HPC). HPC is used as a bonding resin, which is also favorable for the coating of the
AC C
V2O5 shell on the surface of TiO2 HPMs, and then a good interface combination between V2O5 shell and TiO2 core may be formed. Then V2O5 sol was dropwisely added in the reaction solution containing TiO2 HPMs with stirring for a period with the temperature of 80 ℃. The samples were centrifuged, washed, dried, and finally calcined in a muffle furnace at 350℃to obtain TiO2@V2O5 core-shell HPMs, which were named to be TiO2@V2O5-5%, TiO2@V2O5-10% and TiO2@V2O5-15%, respectively, and the detailed parameters for the synthesis of TiO2@V2O5 core-shell
ACCEPTED MANUSCRIPT HPMs are listed in Table 1. Photocatalytic degradation of gaseous benzene: Photocatalytic decomposition of the benzene was carried out in a hermetic stainless steel chamber with the volume of 5
RI PT
L, and a lamp with the wavelength centered at 365 nm was installed on the bracket. The catalyst (0.5 g prepared sample) was dispersed as a thin layer over a glass vessel with the total area of 0.18 m2. The required quantity of benzene was injected into the
SC
reactor, and the initial concentration of benzene was kept at 370 mg/m3 for all
M AN U
experiments. Simultaneous concentration determination of benzene and carbon dioxide was performed with an online gas chromatograph equipped with a flame ionization detector.
Characterization: The samples were characterized by an X-ray diffractometer
TE D
(XRD D/MAX-III) using a Cu K radiation and graphite monochromator, Field emission scanning electron microscopy (FESEM) was carried out on a JEOL JSM-6330F microscope. X-ray photoelectron spectroscopy (XPS) measurements were
EP
performed on a VG Multilab 2000 multi-technique electron spectrometer using Al Kα
AC C
radiation as excitation source. UV-vis absorption spectrum was recorded on a UV-2550 UV-vis spectrophotometer. The Photocatalytic degradation of benzene was performed by a Gas Chromatography (GC-9560, Shanghai Chenhua Technology Corp., Ltd.)
3. Results and Discussion From the XRD patterns shown in Fig. 1, the diffraction peaks centered at 2θ=25.1°, 37.6°, 47.9°, 53.7°, 54.5° and 62.7° appear in the TiO2 sample, which
ACCEPTED MANUSCRIPT agrees well with the crystal planes of anatase TiO2 phase (JCPDS No. 21-1272). For the sample of pure V2O5, there are some diffraction peaks centered 2θ=15.3°, 20.3°, 21.7°, 25.6° and 31.0°, which are assigned to V2O5 phase (JCPDS No. 41-1426).
RI PT
However, the XRD patterns of the samples of TiO2@V2O5-5%, TiO2@V2O5-10% and TiO2@V2O5-15% only possess the diffraction peaks of the anatase TiO2 phase without the diffraction peaks of V2O5 phase, and it indicates that a very thin layer of V2O5
M AN U
detection of V2O5 phase in the XRD patterns.
SC
shells is uniformly dispersed onto the surface of TiO2 HPMs, which may induce no
SEM image proves the hollow structure of the sample shown in Fig. 2(a), and it is found that the microspheres diameter is quite uniform ranging from 700 nm to 900 nm. From the broken microspheres, it is found that TiO2 HPMs are composed of a
TE D
thin layer of TiO2 nanoparticles. From the SEM images in Fig. 2(b-d), the diameters of the TiO2@V2O5 core-shell HPMs are also uniform, and there is no change compared with that of TiO2 HPMs in Fig. 2(a). However, the surface of TiO2@V2O5
EP
core-shell HPMs becomes much rough, and the very small nanoparticles in the
AC C
surface should be vanadium pentoxide. Moreover, the surface chemical composition of the TiO2@V2O5-10% core-shell HPMs is further determined by energy dispersive X-ray (EDX) measurement as described in Fig. 2(e). EDX pattern demonstrates that the TiO2@V2O5 core-shell HPMs are mainly composed of titanium (Ti), oxygen (O), carbon (C) and vanadium (V) elements, which proves the existence of vanadium. The detailed microstructure characteristics of the TiO2 HPMs and TiO2@V2O5 core-shell HPMs are further tested by TEM measurement. From the TEM image in
ACCEPTED MANUSCRIPT Fig. 3(a), it can be seen that the diameter of TiO2 HPMs is of about 700nm, and the lattice distance of 0.365nm corresponds to (101) crystal plane of TiO2 phase from the inset HRTEM image shown in Fig. 3(a). It is found that TiO2 HPMs are composed of
RI PT
a thin layer of TiO2 nanoparticles, and the diameters of the TiO2 nanoparticles are in the range from 20 nm to 50 nm, which is in good agreement with the SEM image in Fig. 2(a). From the TEM images in Fig. 3(b) and 3(c), the diameter of TiO2@V2O5
SC
core-shell HPMs is about 700-900nm. From the selected-area electron diffraction
M AN U
(SAED) pattern in Fig. 3(d), it can be seen that there are two kinds of the diffraction rings, one of them is assigned to be (101) and (103) crystal planes of anatase TiO2 phase, another belongs to the (600) and (402) crystal planes of V2O5 phase, which further proves the coexistence of the polycrystalline structure of the TiO2 and V2O5 in
TE D
the TiO2@V2O5 core-shell HPMs.
XPS spectra are used to investigate the chemical state of TiO2 HPMs and TiO2@V2O5 core-shell HPMs, as shown in Fig. 4, which reveals that the TiO2 HPMs
EP
contain three elements of Ti, O and C in XPS survey spectrum in Fig. 4(a), while the
AC C
V element appears in the in XPS survey spectrum of TiO2@V2O5 core-shell HPMs. Ti 2p spectra in Fig. 4(b) show that 2p1/2 peak of Ti element locates at 464.26 eV, and there is no obvious shift in the peak position after the formation of TiO2@V2O5 core-shell HPMs [33, 34]. Generally, the O 1s peak at 529.77 eV is assigned to the Ti–O bonds, and the peak at 530.5 eV is a signal of the V–O bonds for V2O5, while the peak at 531.69 eV is related to the surface-adsorbed hydroxide (OH) as shown in Fig. 4(c) [34-36],
ACCEPTED MANUSCRIPT which is physically adsorbed on the surface due to their unique microspheres-like structure and high surface area. For the pure TiO2 HPMs, only two peaks with the binding energies of 529.77 eV and 531.69 eV coexist. While for TiO2@V2O5
RI PT
core-shell HPMs, three peaks with the binding energies of 529.75 eV, 530.54 eV and 531.79 eV coexist, which implies the existence of V2O5 in TiO2@V2O5 core-shell HPMs. Most interesting, there are no obvious peak shift for the peak of
SC
surface-adsorbed hydroxide (OH) at 531.79 eV, however, the relative intensity of the
M AN U
peak of adsorbed oxygen (531.79 eV) to the peaks of lattice oxygen (529.75 eV and 530.54 eV) increases from 1:3.67 to 1:1.76 after the formation of TiO2@V2O5 core-shell HPMs, which partially originates from the deposition of V2O5 shells as well as the increasing of the surface-adsorbed hydroxide. It is well known that the
TE D
adsorbed hydroxide species are quite important for the process of photocatalytic reaction, as it may produce hydroxyl radical (OH) by capturing the photo-induced electrons, which favors for the oxidizing of the organic materials and the oxidizing
EP
hydroxylating reaction products as the oxidant [29, 38, 39]. Therefore, the increasing
AC C
of the hydroxide absorption in TiO2@V2O5 core-shell HPMs will favor for their photocatalytic reaction, as the physical absorption ability of hydroxide species not only enhances the separation efficiency of photo-induced electrons and holes, but also promotes the fast transfer of photo-induced electrons to the adsorbed hydroxide species. The binding energies at 524.8 eV and 517.7 eV correspond to V 2p1/2 and V 2p3/2 in Fig. 4(d), respectively, which is related to V5+ oxidation state, and it further improves the existence of V2O5 in the TiO2@V2O5 core-shell HPMs [33, 34].
ACCEPTED MANUSCRIPT UV-vis spectra are used to character the optical absorption of all samples in the wavelength range of 300-800 nm in Fig. 5. It shows that the absorption edges of all TiO2@V2O5 core-shell HPMs will shift to the visible light range compared with that
RI PT
of TiO2 HPMs, which is related to the narrowing band gap by the modification of V2O5 shells. Moreover, TiO2@V2O5 core-shell HPMs possess an obvious enhancement for light absorption ability in the range of UV and visible light
SC
compared with that of TiO2 HPMs and P25. For all of the TiO2@V2O5 core-shell
M AN U
HPMs, the TiO2@V2O5-10% core-shell HPMs achieve the highest optical absorption intensity. The reason lies in the fact that the oxygen vacancies formed during the synthesis process may capture the electrons, which has an important effect on the light absorption [14, 39].
TE D
By choosing the photo-degradation of gaseous benzene as reference materials, the potential photocatalytic properties of TiO2 HPMs and TiO2@V2O5 core-shell HPMs with various V2O5 contents are investigated, respectively. The conversion
EP
between the benzene concentration and the concentration of the produced CO2 gas
AC C
acts as a function of irradiation time, as shown in Fig. 6 and Fig. 7. As shown in Fig. 6, for P25 and V2O5 powder, the removal rate of gaseous benzene is only 74.3% and 27.8% under UV-vis light irradiation, respectively. It is found that no benzene signal is detected after 70 min reaction for TiO2 HPMs, and it exhibits an enhanced removal rate than that of P25, which is attributed to the three-dimensional (3D) architectures of TiO2 HPMs. The 3D architectures of TiO2 HPMs have excellent and attractive performances due to the large interfacial contact areas with gaseous benzene.
ACCEPTED MANUSCRIPT Moreover, it is found that the photocatalytic performance will be enhanced by the formation of TiO2@V2O5 core-shell HPMs. It is found that gaseous benzene is totally photodegraded to be CO2 and H2O in 55 min for the TiO2@V2O5-10% core-shell
RI PT
HPMs, and the produced CO2 concentration is of 1293 ppm in Fig. 6, which corresponds to a high mineralization ratio ([CO2]produced/[C6H6]converted) of 5.5. Such high ratio suggests that about 91.7% of converted-benzene is completely mineralized
SC
to CO2 and H2O, and the other 8.3% of converted-benzene may be degraded to some
formaldehyde [23, 30].
M AN U
kinds of incompletely decomposed compounds, such as CO, acthaldehyde and
Meanwhile, too excessive V2O5 contents (15%) will reduce the photocatalytic properties, and the gaseous benzene is totally photodegraded in 65 min. The reason
TE D
may lies in the fact that TiO2 cores plays a dominant factor for the photodegradation of gaseous benzene, and the effect of V2O5 shells is to extend the light absorption range and then enhance the light absorption, as proved by UV-vis spectra in Fig. 5.
EP
Therefore, too excessive V2O5 loading will cover a large surface of TiO2 HPMs, and it
AC C
may decrease the contact areas with gaseous benzene as well as inhibit the interfacial absorption spectrum of TiO2 HPMs due to the shading effect [28, 30, 40]. At the same time, for pure V2O5 nanoparticles, the removal rate of gaseous
benzene is only 31.8% under visible light irradiation shown in Fig. 7, which indicates that the pure V2O5 powder have a poor photocatalytic activity towards gaseous benzene. It is also found that P25 and TiO2 HPMs have almost no photodegradation towards gaseous benzene under visible light irradiation, as it is well known that the
ACCEPTED MANUSCRIPT conventional TiO2 is photoactivated mostly upon UV irradiation (light wavelength <400 nm) in order to overcome its wide band gap energy (3.2 eV). Obviously, under visible light irradiation the photodegradation efficiencies of P25 and TiO2 HPMs are low.
However,
TiO2@V2O5
core-shell
HPMs
show
a
higher
RI PT
relatively
photodegradation activity than either P25, TiO2 HPMs or pure V2O5, especially for TiO2@V2O5-10%, the removal rate of gaseous benzene is 68.9% in 75 min. The result
SC
should be mainly attributed to the coupling of TiO2 cores with V2O5 shells may
M AN U
promote the photodegradation activity, and the TiO2@V2O5 interface plays a crucial role in the gaseous benzene photodegradation reaction.
It is well known that a typical junction barrier at the interface between V2O5 shells and TiO2 cores will be formed, as the heterojunctions will suppress the recombination
TE D
of electron-hole pairs in TiO2@V2O5 core-shell HPMs, where the V2O5 shells act as an efficient electron traps aiding electron-hole separation. The possible mechanism of the heterojunctions can be understood through the energy band diagram of the
EP
heterojunctions as shown in Fig. 8. Under UV-visible light irradiation, the absorption
AC C
of a photon with energy larger than the band gap of the semiconductor can induce the electron transition from the valence band (VB) to the conduction band (CB) of V2O5 shells and TiO2 cores, and then the photoexcited electrons migrate and are collected to the CB of V2O5 shells, leaving holes in the VB of TiO2 cores [4, 7, 40]. Therefore, the photogenerated electrons and holes can be separated efficiently at the interface, and the chemical binding interface of TiO2@V2O5 core-shell HPMs is also favorable for the effective separation of photoexcited electrons and holes in our
ACCEPTED MANUSCRIPT case. The increasing of the charge separation of the photogenerated electrons and holes allows both of the photo-generated electrons and holes to initiate redox reactions with molecular species adsorbed on the surfaces of the composite catalysts.
RI PT
The photogenerated holes can react with surface adsorbed H2O molecules to produce •OH radicals, while the photoexcited electrons are usually scavenged by O2 to yield superoxide radical anions •O2-, which can degrade gaseous benzene efficiently. In
SC
addition, the large surface area of TiO2@V2O5 core-shell HPMs is favorable for the
M AN U
adsorption of benzene molecules due to their porous structure. For a large amount of benzene molecules absorbed on the surface, it becomes easy for the pollutants to react with the generated active species (•OH and •O2-), and this may be an important reason
4. Conclusions
TE D
for the high activity of the TiO2@V2O5 core-shell HPMs [18, 41].
In summary, three-dimensional (3D) architectures of TiO2 HPMs are successfully
EP
synthesized, and then TiO2@V2O5 core-shell HPMs are formed by hydrothermal progress together with sol-gel technique. Hollow microspheres with high surface
AC C
areas and abundant porous structures are beneficial to the large interfacial contact areas with gaseous benzene. It is found that TiO2@V2O5 core-shell HPMs have been proven to show a superior photocatalytic activity compared to pure TiO2 HPMs, P25 and V2O5 nanoparticles. In particular, TiO2@V2O5-10% core-shell HPMs presents the best photodegradation efficiency of 100% in 55 min and 68.9% in 75 min under UV-visible and visible light irradiation, respectively. However, too excessive V2O5 contents (15%) will reduce the photocatalytic properties, and the gaseous benzene is
ACCEPTED MANUSCRIPT totally photodegraded in 65 min. The reason may lies in the fact that TiO2 cores plays a dominant factor for the photodegradation of gaseous benzene, and the effect of V2O5 shells is to extend the light absorption to visible light range and then enhance the light Moreover, the well-formed interface between V2O5 shells and TiO2
RI PT
absorption.
cores may suppress the recombination of electron-hole pairs in TiO2@V2O5 core-shell HPMs, and the photogenerated electrons and holes can be separated efficiently at the
SC
interface, which may greatly enhance the photodegradation performance. While too
M AN U
excessive V2O5 loading will cover a large surface of TiO2 HPMs, and it may decrease the contact areas with gaseous benzene as well as inhibit the interfacial absorption spectrum of TiO2 HPMs due to the shading effect.
Acknowledgements
TE D
This work is supported by Equipment pre-research project (No. 625010402), National Nature Science Foundation of China (51506155), Science and Technology Support Program of Hubei Province (No. 2014BAA096), the Nature Science
EP
Foundation of Hubei Province (No. 2014CFB165), and the Key Laboratory of
AC C
Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province (No. GD201402). Thanks for the measurements supporting from Center for Materials Research and Analysis at Wuhan University of Technology (WUT).
ACCEPTED MANUSCRIPT
References [1] S. Ge, H. X. Zheng, Y. F. Sun, Z. Jin, J. H. Shan, C. Wang, H. Wu, M. Q. Li, F. L. Meng, J. Alloys Compd. 659 (2016) 127-131.
RI PT
[2] H. B. Huang, H. L. Huang, L. Zhang, P. Hu, X. G. Ye, D. Y. C. Leung, Chem. Eng. J. 259 (2015) 534-541.
[3] S. Weon, W. Choi, Environ. Sci. Technol. 50 (2016) 2556-2563.
SC
[4] X. B. Chen, S. H. Shen, L. J. Guo, S. S. Mao, Chem. Rev. 110 (2010) 6503-6570.
M AN U
[5] R. M. Mohamed, I. A. Mkhalid, J. Alloys Compd. 501 (2010) 143-147. [6] F. Y. Jing, D. Z. Zhang, F. Li, J. G. Zhou, D. M. Sun, S. P. Ruan, J. Alloys Compd. 650 (2015) 97-101.
[7] C. M. Teh, A. R. Mohamed, J. Alloys Compd. 509 (2011) 1648-1660.
[9] S.
Ivanov,
A.
TE D
[8] A. I. Hochbaum, P. D. Yang, Chem. Rev. 110 (2010) 527-546. Barylyak,
K.
Besaha,
A.
Bund,
Y.
Bobitski,
R.
Wojnarowska-Nowak, I. Yaremchuk, M. Kus-Liśkiewicz, Nanoscale Res. Lett.
EP
11 (2016) 1-12.
AC C
[10] K. Pathakoti, S. Morrow, C. Han, M. Pelaez, X. J. He, D. D. Dionysiou, H. M. Hwang, Environ. Sci. Technol. 47 (2013) 9988-9996.
[11] M. Hamadanian, A. Reisi-Vanani, A. Majedi. Appl. Surf. Sci. 256 (2010) 1837-1844.
[12] L. G. Devi, R. Kavitha, Appl. Catal. B 140 (2013) 559-587. [13] S. Izadyar, S. Fatemi, Ind. Eng. Chem. Res. 52 (2013) 10961-10968.
ACCEPTED MANUSCRIPT [14] Y. L. Liu, G. J. Yang, H. Zhang, Y. Q. Cheng, K. Q. Chen, Z. Y. Peng, W. Chen, RSC Adv. 4 (2014) 24363-24368. [15] Y. L. Liu, W. Shu, Z. Y. Peng, K. Q. Chen, W. Chen, Catal. Today 208 (2013)
RI PT
28-33. [16] Y. L. Liu, Y. Q. Cheng, W. Shu, Z. Y. Peng, K. Q. Chen, J. Zhou, W. Chen, G. S. Zakharova, Nanoscale 6 (2014) 6755-6762.
Liu, Y. K. Liu, C. Y. Luan, H. Cheng, Y. Y. Li, L.
SC
[17] H. E. Wang, L. X. Zheng, C. P.
M AN U
Martinu, J.A. Zapien, I. Bello. J. Phys. Chem. C 115 (2011) 10419-10425. [18] Y. Yang, G. Z. Wang, Q. Deng, H. L. Ng. Dickon, H. J. Zhao. ACS Appl. Mater. Interfaces 6 (2014) 3008-3015.
[19] C. L. Yu, J. C. Yu, M. Chan. J. Solid State Chem. 182 (2009) 1061-1069.
TE D
[20] H. Y. Yin, X. L. Wang, L. Wang, Q. L. Nie, Y. Zhang, Q. L. Yuan, W. W. Wu, J. Alloys Compd. 657 (2016) 44-52.
[21] H. J. Yan, H. X. Yang. J. Alloys Compd. 509 (2011) L26-L29.
EP
[22] J. G. Tao, T. Luttrell, M. Batzill, Nat. Chem. 3 (2011) 296-300.
AC C
[23] Y. L. Liu, W. Shu, K. Q. Chen, Z. Y. Peng, W. Chen, ACS Catal. 2 (2012) 2557-2565.
[24] Y. D. Liu, F. Xin, F. M. Wang, S. X. Luo, X. H. Yin, J. Alloys Compd. 498 (2010) 179-184.
[25] H. Park, Y. Park, W. Kim, W. Choi, J. Photoch. Photobio. C 15 (2013) 1-20. [26] J. Zhang, W. Fu, J. H. Xi, H. He, S. C. Zhao, H. W. Lu, Z. G. Ji, J. Alloys Compd. 575 (2013) 40-47.
ACCEPTED MANUSCRIPT [27] W. Shu, Y. L. Liu, Z. Y. Peng, K. Q. Chen, C. Zhang, W. Chen, J. Alloys Compd. 563 (2013) 229-233. [28] W. Cha, S. Chin, E. Park, S. T. Yun, J. Jurng, Appl. Catal. B 140 (2013) 705-715.
Nanotechnology 22 (2011) 225702.
RI PT
[29] Y. Wang, Y. R. Su, L. Qiao, L. X. Liu, Q. Su, C. Q. Zhu, X. Q. Liu,
[30] J. Wang, X. Wang, X. L. Liu, J. L. Zeng, Y. Y. Guo, T. Y. Zhu, J. Mol. Catal.
SC
A-Chem. 402 (2015) 1-9.
M AN U
[31] J. J. Du, W. Chen, C. Zhang, Y. L. Liu, C. X. Zhao, Y. Dai, Chem. Eng. J. 170 (2011) 53-58.
[32] B. Alonso and J. Livage, J. Solid State Chem. 148 (1999)16-19. [33] J. L. G. Fierro, L. A. Arrua, J. M. L. Nieto, G. Kremenic, Appl. Catal. 37 (1988)
TE D
323-338.
[34] J. L. Ong, L. C. Lucas, G. N. Raikar, J. C. Gregory, Appl. Surf. Sci. 72 (1993) 7-13.
EP
[35] V. I. Nefedov, M. N. Firsov, I. S. Shaplygin, J. Electron Spectrosc. Relat. Phenom.
AC C
26 (1982) 65-70.
[36] P. R. Moses, L. M. Wier, J. C. Lennox, H. O. Finklea, F. R. Lenhard, R. W. Murray, Anal. Chem. 50 (1978) 576-581.
[37] A. Mills, S. L. Hunte, J. Photoch. Photobio. A 108 (1997) 1-35. [38] D. Chatterjee, S. Dasgupta, J. Photoch. Photobio. C 6 (2005) 186-205. [39] J. S. Dalton, P. A. Janes, N. G. Jones, J. A. Nicholson, K. R. Hallam, G. C. Allen, Environ. Pollut. 120 (2002) 415–422.
ACCEPTED MANUSCRIPT [40] J. Su, X. X. Zou, G. D. Li, X. Wei, C. Yan, Y. N. Wang, J. Zhao, L. J. Zhou, J. S. Chen, J. Phys. Chem. C 115 (2011) 8064-8071. [41] Y. M. Lin, D. Z. Li, J. H. Hu, G. C. Xiao, J. X. Wang, W. J. Li, X. Z. Fu, J. Phys.
AC C
EP
TE D
M AN U
SC
RI PT
Chem. C 116 (2012) 5764-5772.
ACCEPTED MANUSCRIPT Figure Captions Table 1 Synthesis parameters of TiO2@V2O5 core-shell hollow porous microspheres Fig. 1 XRD patterns of the samples.
RI PT
Fig. 2 SEM images of samples: (a) Pure TiO2 HPMs; (b) TiO2@V2O5-5% core-shell HPMs; (c) TiO2@V2O5-10% core-shell HPMs; (d) TiO2@V2O5-15% core-shell HPMs; (e) EDX pattern of TiO2@V2O5-10% core-shell HPMs.
SC
Fig. 3 (a) TEM images and HRTEM images of the pure TiO2 HPMs; (b, c) TEM
M AN U
images and (d) SAED pattern of TiO2@V2O5 core-shell HPMs.
Fig. 4 XPS spectra of TiO2 HPMs and TiO2@V2O5 core-shell HPMs: (a) Survey spectra; (b) Ti 2p spectra; (c) O 1s spectra; (d) V 2p spectrum.
Fig. 5 UV-vis spectra of TiO2 HPMs and TiO2@V2O5 core-shell HPMs.
TE D
Fig. 6 The photocatalytic performance of P25, pure TiO2 HPMs and TiO2@V2O5 core-shell HPMs under UV-vis light irradiation: (a) Plots of the decreasing in benzene concentration vs. irradiation time; (b) plots of the increasing in CO2 concentration vs.
EP
irradiation time.
AC C
Fig. 7 The photocatalytic performance of P25, pure TiO2 HPMs and TiO2@V2O5 core-shell HPMs under visible light irradiation: (a) Plots of the decreasing in benzene concentration vs. irradiation time; (b) plots of the increasing in CO2 concentration vs. irradiation time.
Fig. 8 Energy band diagram of TiO2@V2O5 core-shell HPMs.
RI PT
ACCEPTED MANUSCRIPT
Table 1 Synthesis parameters of TiO2@V2O5 core-shell hollow porous microspheres
V 2O 5
0.0572 g
1g
M AN U
1g
AC C
EP
TE D
TiO2 HPMs
TiO2@V2O5-10%
TiO2@V2O5-15%
SC
TiO2@V2O5-5%
0.1130 g
1g 0.1690 g
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
Fig. 1 XRD patterns of the samples.
ACCEPTED MANUSCRIPT
(a)
500 nm
500 nm
(c)
M AN U
(d)
SC
200 nm
200 nm
200 nm
RI PT
(b)
200 nm
500 nm
TE D
500 nm
AC C
EP
(e)
Fig. 2 SEM images of samples: (a) Pure TiO2 HPMs; (b) TiO2@V2O5-5% core-shell HPMs; (c) TiO2@V2O5-10% core-shell HPMs; (d) TiO2@V2O5-15% core-shell HPMs; (e) EDX pattern of TiO2@V2O5-10% core-shell HPMs.
(b)
(a) 0.365 (101)
M AN U
SC
3nm
RI PT
ACCEPTED MANUSCRIPT
500 nm
100nm
(c)
TiO2 (103)
TiO2 (101) V2O5 (402)
EP
100 nm
TE D
(d)
V2O5 (600)
AC C
Fig. 3 (a) TEM images and HRTEM images of the pure TiO2 HPMs; (b, c) TEM (b) images and (d) SAED pattern of TiO2@V2O5 core-shell HPMs.
(b)
M AN U
SC
(a)
RI PT
ACCEPTED MANUSCRIPT
(c)
EP
TE D
(d)
AC C
Fig. 4 XPS spectra of TiO2 HPMs and TiO2@V2O5 core-shell HPMs: (a) Survey spectra; (b) Ti 2p spectra; (c) O 1s spectra; (d) V 2p spectrum.
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
Fig. 5 UV-vis spectra of TiO2 HPMs and TiO2@V2O5 core-shell HPMs.
ACCEPTED MANUSCRIPT
M AN U
SC
RI PT
(a)
AC C
EP
TE D
(b)
Fig. 6 The photocatalytic performance of P25, pure TiO2 HPMs and TiO2@V2O5
core-shell HPMs under UV-vis light irradiation: (a) Plots of the decreasing in benzene concentration vs. irradiation time; (b) plots of the increasing in CO2 concentration vs. irradiation time.
ACCEPTED MANUSCRIPT
M AN U
SC
RI PT
(a)
AC C
EP
TE D
(b)
Fig. 7 The photocatalytic performance of P25, pure TiO2 HPMs and TiO2@V2O5
core-shell HPMs under visible light irradiation: (a) Plots of the decreasing in benzene concentration vs. irradiation time; (b) plots of the increasing in CO2 concentration vs. irradiation time.
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
Fig. 8 Energy band diagram of TiO2@V2O5 core-shell HPMs
ACCEPTED MANUSCRIPT Research highlights 1) TiO2@V2O5 core-shell hollow porous microspheres (HPMs) are successfully
RI PT
synthesized
2) Photodegradation rate of TiO2@V2O5 core-shell HPMs towards benzene is greatly enhanced
SC
3) Light absorption range of TiO2@V2O5 core-shell HPMs is extended due to the
M AN U
narrowed band gap
4) The photogenerated electrons and holes are effectively separated for TiO2@V2O5
AC C
EP
TE D
core-shell HPMs