Metal-free porous phosphorus-doped g-C3N4photocatalyst achieving efficient synthesis of benzoin

Article abstract of DOI:10.1039/d1ra00701g

Photocatalytic organic synthesis is mostly limited by the shortcomings of insufficient light absorption, high photogenerated electron-hole recombination rate and inadequate reactive sites of photocatalysts. To solve these problems, phosphorus-doped g-C₃N₄with a porous structure was constructed. Benefiting from enhanced light absorption and electron-hole separation efficiency, PCNT has intensive oxygen activation ability to generate superoxide radicals, and is highly active in organic synthesis. In addition, PCNT has enhanced surface nucleophilicity, which is conducive to the carbon-carbon coupling process of the intermediate product benzaldehyde molecules and benzyl alcohol molecules in the benzoin condensation reaction. Metal-free PCNT is expected to replace the previously used highly toxic cyanide catalysts and provide a new way for the low-cost and efficient photocatalytic synthesis of benzoin.

Full text of DOI:10.1039/d1ra00701g

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Metal-free porous phosphorus-doped g-C3N4
photocatalyst achieving efficient synthesis of
benzoin†
Cite this: RSC Adv., 2021, 11, 12682
a
a
a
Yuanjin Li,‡ Shuhui Wang,‡ Jin Wu,b Qiuyan Wang,
Changqiu Ma,a
*
a
c
b
a
*
*
*
Daheng Jiang, Wanglai Hu, Lixin Zhu and Xiaoliang Xu
Photocatalytic organic synthesis is mostly limited by the shortcomings of insufficient light absorption, high
photogenerated electron–hole recombination rate and inadequate reactive sites of photocatalysts. To
solve these problems, phosphorus-doped g-C3N4 with a porous structure was constructed. Benefiting
from enhanced light absorption and electron–hole separation efficiency, PCNT has intensive oxygen
activation ability to generate superoxide radicals, and is highly active in organic synthesis. In addition,
PCNT has enhanced surface nucleophilicity, which is conducive to the carbon–carbon coupling process
of the intermediate product benzaldehyde molecules and benzyl alcohol molecules in the benzoin
condensation reaction. Metal-free PCNT is expected to replace the previously used highly toxic cyanide
catalysts and provide a new way for the low-cost and efficient photocatalytic synthesis of benzoin.
Received 26th January 2021
Accepted 13th March 2021
DOI: 10.1039/d1ra00701g
rsc.li/rsc-advances
covalent bonds, which has the advantages of simple and
convenient synthesis, low toxicity and high chemical
stability.11–14 Because of its proper electronic energy band
1. Introduction
Organic synthetic chemistry has constructed a rich and col-
ourful world and plays an increasingly important role in
people's life.1,2 The pursuit of green and efficient synthetic
methods has always been the development direction of organic
synthesis chemistry. Among them, photocatalytic organic
synthesis has become a potential organic synthesis method due
to its advantages of utilizing renewable solar energy and mild
reaction conditions.3–6 Benzoin, as an important organic
synthesis intermediate, has wide applications in the production
of medicines, spices and daily chemicals.7–9 However, the
current catalytic oxidation synthesis of benzoin usually uses
highly toxic cyanide as a catalyst, which is likely to cause
pollution during the operation, signicantly limiting its further
applications.10 Therefore, there is an urgent need to design and
construct a cheap and environmentally friendly heterogeneous
photocatalyst for efficient benzoin condensation reaction.
Graphite carbon nitride (g-C3N4) is a polymer semiconductor
material with a layered structure similar to graphite, in which
carbon and nitrogen atoms are tightly combined into rings by
position and outstanding physical and chemical properties, g-
C3N4 is considered as a developing photocatalyst, which has
been used in various photocatalytic applications, such as water
splitting,15–18 CO2 reduction,11,19,20 pollutant degradation,21–23
and organic synthesis.24–27 Generally, an effective photocatalyst
needs to have strong and broad light absorption, effective
photogenerated carrier separation efficiency, appropriate
energy band position, and enough reactive sites to make active
substances (such as electrons and reactive oxygen species)
participate in the catalytic process. Therefore, these properties
can determine the efficiency of photocatalytic organic synthesis.
For improvement of relevant catalysts, porous structure and
element doping are two crucial methods.11,28–30 Among them,
the porous structure helps the catalyst expose more active sites,
and the reactants and products are more easily to diffuse in the
catalyst, thereby helping to accelerate the reaction process.
Element doping can change the electronic state density of the
catalyst, facilitate the separation and redistribution of charges
in the catalyst, and can provide more charge for the photo-
catalytic reaction and improve the photocatalytic performance.
Herein, we synthesized porous phosphorus-doped g-C3N4
(PCNT) through the combination of mixed precursors and
thermal exfoliation. PCNT has excellent photocatalytic perfor-
mance and can be used in the selective oxidative coupling
reaction of benzyl alcohol. A detailed study of the reaction
process shows that the synthesis of benzoin from benzyl alcohol
is divided into two steps, in which benzaldehyde is an inter-
mediate product in the reaction process, and the enhanced
aSchool of Physical Sciences, University of Science and Technology of China, Hefei,
Anhui 230026, PR China. E-mail: wsh2016@mail.ustc.edu.cn; xlxu@ustc.edu.cn
bDepartment of General Surgery & Central Laboratory, The First Affiliated Hospital of
Anhui Medical University, Hefei, Anhui 230022, PR China. E-mail: lx-zhu@163.com
cTranslational Research Institute of Henan Provincial People's Hospital, Molecular
Pathology Center of Academy of Medical Science, Zhengzhou University, Zhengzhou,
Henan 450003, PR China. E-mail: wanglaihu@ahmu.edu.cn
† Electronic supplementary information (ESI) available: Experiment details and
additional characterizations. See DOI: 10.1039/d1ra00701g
‡ These authors contributed equally to this work.
12682 | RSC Adv., 2021, 11, 12682–12686
© 2021 The Author(s). Published by the Royal Society of Chemistry

View Article Online
Paper
RSC Advances
nucleophilicity of PCNT is benecial to the occurrence of the benzyl alcohol concentration. Selectivity is the ratio of yield rate
carbon–carbon coupling process. This is the rst report of using to conversion rate.
a completely non-metallic photocatalyst in the condensation of
benzoin. As a photocatalyst, PCNT can reduce production costs
3. Results and discussion
and increase the conversion rate of reaction raw materials, and
the catalyst can be easily recycled as well. It is a new way to
efficiently synthesize benzoin and conform to the new concept
of modern green chemistry.
In this work, PCNT was prepared by phosphorus doping and
thermal exfoliation. The characteristic crystal structures of all
prepared samples are shown in Fig. 1a, the two crystal planes of
(100) and (002) are corresponding to the standard patterns
(JCPDS 87-1526), indicating high purity of all samples.
2. Experimental
Compared with CN, the (002) diffraction peak of PCN obviously
moves to a lower angle due to the introduction of phosphorus
element with a larger atomic radius, and the peak moves back
slightly aer thermal exfoliation. Energy Dispersive Spectrom-
eter conrms the equidistribution of P, C and N elements in
PCNT (Fig. 1b). The chemical structure and composition of
PCNT were further studied by X-ray photoelectron spectroscopy
(XPS) and X-ray absorption near edge structure (XANES).
Compared with that of CNT, the N 1s spectrum of PCNT shis to
the direction of higher binding energy (Fig. 1c), and the peak
located at 133.8 eV binding energy in the P 2p spectrum of PCNT
can be attributed to the P–N bond (Fig. S2†).31,32 Therefore, it
can be inferred that P replaces C in the structural unit of g-C3N4.
As shown by the N K-edge spectra of Fig. 1d, the peak belonging
to C–N–C is obviously shied, which further supports the above
conclusion.
2.1 Synthesis of photocatalysts
All reagents are analytical grade chemicals, directly used
without further depuration. Phosphorus-doped g-C3N4 (PCN)
was synthesized by thermal condensation of mixed precursors
(2-aminoethylphosphonic acid and melamine). More
concretely, 6 g of melamine (ME) and 100 mg of 2-amino-
ethylphosphonic acid (AEP) were uniformly mixed and placed in
a covered quartz boat (the optimal doping concentration was
determined by preliminary research in Fig. S1†). The mixture
was heated to 550 ꢀC from 30 ꢀC within 52 minutes, maintained
for 6 h, then naturally cooled. The obtained PCN was treated
with thermal exfoliation to synthesize porous PCNT. In detail,
ꢀ
the PCN was heated in an open crucible to 500 C, kept for 90
minutes, then cooled naturally. The product was ground into
powder to obtain PCNT. In the same way without AEP, ordinary
g-C3N4 (CN) and thermally peeled g-C3N4 (CNT) were prepared.
On the other hand, the AEP added in the synthesis process of
PCN and PCNT can not only be used as a phosphorus source,
but also can be used as a gas phase template for sample growth.
AEP can generate ammonia during the heating process, which
will create a porous structure in the sample.33 A further thermal
peeling process can reduce the thickness of the sample and
expose these holes. The porous structure of PCNT was ocularly
characterized by the transmission electron microscopy (TEM)
and scanning electron microscopy images in Fig. 2a and S3.† In
contrast, CN has a thick and large aggregate morphology
2.2 Nitroblue tetrazole (NBT) degradation experiments
50 mg of photocatalyst was mixed with 50 mL NBT solution (200
mM), illuminated by a 300 W xenon lamp (PLS-SXE300/300UV,
Trusttech Co., Ltd., Beijing). The concentration of NBT was
monitored by UV-visible spectra (Perkin Elmer Lambda950)
every 30 minutes, as the absorption peak of NBT is located at
259 nm.
2.3 Electron spin resonance (ESR) tests
500 mL of 5,5-dimethyl-1-pyrrolidine-N-oxide (DMPO, 10 mM)
was added into 50 mL sample aqueous solution (10 g LÀ1). Aer
being irradiated for 1 min with a xenon lamp (same as above),
the mixed solution was characterized using a JEOL JES-FA200
electron spin resonance spectrometer (298 K, 9.062 GHz).
2.4 Photocatalytic synthesis of benzoin
10 mg of photocatalyst and 2 mL of benzotriuoride were mixed
in a 10 mL quartz tube. Aer sonication, 0.1 mmol of benzyl
alcohol was added and oxygen was bubbled for one minute.
Then the quartz tube was sealed and irradiated with a xenon
lamp (the same as that in ESR tests) for 6 h. The photocatalyst
was removed by centrifugation, and the reaction solution was
collected. The product was measured by a 400 MHz 1H Bruker
AVANCE AV III NMR spectrometer, using tetramethylsilane as
an internal standard. Conversion rate is the ratio of reduced
benzyl alcohol concentration to initial benzyl alcohol concen-
tration. The yield rate is the proportion of benzyl alcohol
Fig. 1 (a) X-ray diffraction results of CN, CNT, PCN, and PCNT. (b)
Elemental mapping images of PCNT. (c) XPS N 1s spectra of PCNT and
concentration consumed by the target product in the initial CNT. (d) XANES N K-edge spectra of PCNT and CNT.
© 2021 The Author(s). Published by the Royal Society of Chemistry
RSC Adv., 2021, 11, 12682–12686 | 12683

View Article Online
RSC Advances
Paper
Fig. 2 (a–c) TEM images of (a) PCNT, (b) PCN, and (c) CNT. (d)
Nitrogen adsorption–desorption isotherms of CN, CNT, PCN, and
PCNT with the inset displaying the corresponding pore size distribu-
tion curves.
Fig. 3 (a) UV-vis absorption spectra, (b) corresponding band gap, (c)
schematic illustration of band structure, and (d) photoluminescence
spectra of CN, CNT, PCN, and PCNT.
photocatalysts was detected through photoluminescence
spectra. As displayed in Fig. 3d, CN has the relatively strongest
photoluminescence intensity, indicating the serious recombi-
nation of the photogenerated electrons and holes in it. For CNT
and PCNT, their photoluminescence position has a signicant
blue shi relative to the corresponding bulk materials, which is
consistent with the UV-visible absorption spectroscopy. PCN
and PCNT have signicantly reduced luminous intensity,
proving that phosphorous doping can effectively hinder the
recombination of photogenerated carriers. For PCNT, enhanced
light absorption is conducive to utilizing more solar energy and
generating more photogenerated carriers, and the effective
separation of photogenerated carriers ensures that there are
enough electrons and holes for photocatalytic reactions.
(Fig. S3†), PCN has a rough undulating surface (Fig. 2b), while
CNT has a non-porous sheet structure (Fig. 2c and S4†). The BET
surface area of all samples was compared by nitrogen adsorp-
tion–desorption curve. As displayed in Fig. 2d, both samples
show IV type isotherms, indicating the presence of mesopores
in the samples.34 Under higher relative pressure, the isotherms
of PCNT show higher absorption rates, indicating that there are
large mesopores and macropores. The unique porous structure
of PCNT results in a relatively large specic surface area, which
exposes more active sites. At the same time, the presence of
pores facilitates the diffusion of reactants and products mole-
cules in the photocatalytic process, which is benecial to the
improvement of catalytic activity.
As the rst step of the photocatalytic reaction process, only
when photocatalysts absorb sufficient light energy, can photo-
generated electron–hole pairs be produced in photocatalysts. In
this case, light absorption efficiency much affects the photo-
catalytic reaction efficiency.35 UV-visible diffuse reectance
spectroscopy was conducted to study the optical properties and
band structure of the prepared samples. As displayed in Fig. 3a,
phosphorus doping makes the light absorption of PCN and
PCNT signicantly increase over a large range. The porous
structure caused by phosphorus doping increases the reection
of light in the holes, which may lead to enhanced light
absorption. Meanwhile, the absorption edge of PCN and PCNT
extend to the high wavelength direction. Due to the quantum
connement effect, the light absorption of the two thermally
stripped samples is slightly blue-shied compared with that of
original samples.36,37 The typical light absorption edges of CN,
CNT, PCN, and PCNT are located at approximately 454, 444, 471
and 468 nm, corresponding to the indirect band gaps of 2.73,
2.79, 2.63 and 2.65 eV, respectively (Fig. 3b). Combined with the
XPS valence band spectra (Fig. S5†), the band structures of
several samples are schematically shown in Fig. 3c. Further-
more, the separation efficiency of photogenerated carriers of all
Fig. 4 (a) The degradation process of NBT with PCNT and CNT in O2.
(b) Time-dependent NBT concentration curve in the degradation
process. (c) Time-dependent NBT degradation process with PCNT in
gas conditions. (d) ESR spectra of PCNT and CNT after adding DMPO.
12684 | RSC Adv., 2021, 11, 12682–12686
© 2021 The Author(s). Published by the Royal Society of Chemistry

View Article Online
Paper
RSC Advances
Phosphorus doping is favourable in oxygen activation, which so it is speculated that benzaldehyde is an intermediate product
is proved with nitroblue tetrazole (NBT) as a probe molecule for in the synthesis process of benzoin from benzyl alcohol. To
generated O2cÀ radicals.38 As displayed in Fig. 4a and b, the verify this, we monitored the changes in the content of benz-
time-dependent absorption spectra of NBT degradation in aldehyde and benzoin over time. As shown in Fig. 5b and c, only
oxygen displays the enhanced oxygen activation ability of PCNT. benzaldehyde was produced at the beginning. Aer 3 hours of
Besides, the dramatically different NBT degradation rates light irradiation, the yield of benzaldehyde reached the highest
decreased signicantly under the condition of oxygen- value of 41.8%. As the reaction continues, the content of
deciency (air) and oxygen-free (argon), indicating that the benzaldehyde begins to decrease, and benzoin is gradually
O2cÀ evolve from oxygen (Fig. 4c). Electron spin resonance (ESR) formed, eventually reaching a high benzoin yield. According to
tests can also evaluate the presence of O2cÀ. When DMPO was this trend, we conrmed the accumulation and consumption of
used as a scavenger to detect the O2cÀ formation in the system, benzaldehyde in the reaction process, and benzaldehyde is an
signicantly enhanced sextet ESR signals of DMPO-O2cÀ intermediate product of the reaction. One of the reasons why
adducts were clearly observed in both PCNT and CNT, con- CN, CNT and PCN cannot catalyze the formation of benzoin is
rming the generation of O2cÀ (Fig. 4d). Moreover, the DMPO- that sufficient concentration of benzaldehyde is not produced
O2cÀ signal of PCNT is obviously stronger than that of CNT, during the reaction. In addition, we used benzaldehyde as the
suggesting the enhanced O2cÀ generation ability, which is well raw material for the photocatalytic synthesis of benzoin, and
in agreement with the above oxygen activation tests.
only the conversion rate and selectivity of benzaldehyde to
The synthesis of benzoin with benzyl alcohol further benzoin on PCNs both reached 99%.
conrmed the excellent photocatalytic performance of PCNT. As
Based on the above experimental results, we analyzed the
shown in Fig. 5a, aer 6 hours of xenon lamp irradiation, the reaction mechanism, which is schematically shown in Fig. 5d.
conversion rate of benzyl alcohol can reach 99.8% with PCNT as In the synthesis process of benzoin from benzyl alcohol, the
the photocatalyst, and the yield of benzoin can reach 95.4% formation of benzaldehyde is the rst step, and O2cÀ is the key
with fairly high selectivity. For CN, CNT and PCN, they can only reactive oxygen species for the formation of benzaldehyde.
catalyse the oxidation of benzyl alcohol to a small amount of Beneting from the enhanced ability to generate superoxide
benzaldehyde (Fig. S6†). The reaction time was further extended radicals, PCNT can more effectively photocatalyze the selective
to 12 hours, and there was still no benzoin formation on CN, photo-oxidation of benzyl alcohol to benzaldehyde. When the
CNT, and PCN. Moreover, prolonging the reaction time has concentration of benzaldehyde in the reaction system is suffi-
almost no effect on the amount of benzaldehyde produced on cient, the C–C coupling of benzaldehyde molecules occurs in
these catalysts. In addition, the cyclic stability of PCNT in the the synthesis process of benzoin.39 In the C–C coupling process,
photocatalytic benzyl synthesis process was further studied. polarity of the photocatalyst is of critical importance. As shown
Aer 5 consecutive cycles, the conversion rate of benzyl alcohol by the zeta potential results (Fig. S7†), compared with the
and the yield of benzoin remained basically unchanged, indi- original CN, the zeta potential of PCNT is doubled, and the
cating that PCNT has good cycle stability.
potential of PCNT is the lowest among all the catalysts, which
In the benzoin synthesis process with PCNT as a photo- proves that the surface of PCNT has more negative charges.
catalyst, no by-products were detected except for benzaldehyde, PCNT is a catalyst with more nucleophilic surface properties,40
so it is easier to connect to the carbon ions in the benzaldehyde
carbonyl group, and drive the C–C coupling process of benzal-
dehyde. Finally, the efficient conversion from benzyl alcohol to
benzoin is achieved on PCNT.
4. Conclusions
In summary, the problem of insufficient light absorption and
serious recombination of photogenerated carriers of g-C3N4 is
solved by the strategy of phosphorus doping, resulting in
enhanced photocatalytic activity. Using mixed precursor
thermal condensation and subsequent thermal peeling
methods, we prepared phosphorus-doped PCNT with a porous
structure. The introduction of P element was demonstrated by
different characterizations. The porous structure of PCNT was
veried by TEM image, SEM image and nitrogen adsorption–
desorption curve. PCNT achieved enhanced light absorption
capacity and effective photogenerated carriers separation, and
Fig. 5 (a) Yield rate of benzoin and benzaldehyde on different pho-
have enhanced oxygen activation capacity. As a result, the
tocatalysts within 6 h. (b) Time-dependent yield rate of benzoin and
photocatalytic synthesis process of benzoin from benzyl alcohol
can be efficiently realized on PCNT, with benzaldehyde as the
intermediate product in the reaction. PCNT is easy to prepare,
benzaldehyde with PCNT as photocatalyst. (c) Representative 1H NMR
spectra of photocatalytic reaction process on PCNT at different times.
(d) Schematic synthesis mechanism of benzoin from benzyl alcohol.
© 2021 The Author(s). Published by the Royal Society of Chemistry
RSC Adv., 2021, 11, 12682–12686 | 12685

View Article Online
RSC Advances
Paper
do not contain any metal elements, and is an environmentally 17 X. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin,
friendly photocatalyst. This work is expected to apply cheap,
non-polluted and metal-free semiconductor materials for
J. M. Carlsson, K. Domen and M. Antonietti, Nat. Mater.,
2009, 8, 76.
achieving effective photocatalytic organic synthesis reactions 18 J. Liu, Y. Liu, N. Liu, Y. Han, X. Zhang, H. Huang, Y. Lifshitz,
under environmental conditions.
S. T. Lee, J. Zhong and Z. Kang, Science, 2015, 347, 970.
19 A. Li, T. Wang, C. Li, Z. Huang, Z. Luo and J. Gong, Angew.
Chem., Int. Ed., 2019, 58, 3804.
20 K. Wang, Q. Li, B. Liu, B. Cheng, W. Ho and J. Yu, Appl.
Catal., B, 2015, 176, 44.
Conflicts of interest
There are no conicts to declare.
21 M. Chu, K. Hu, J. Wang, Y. Liu, S. Ali, C. Qin and L. Jing, Appl.
Catal., B, 2019, 243, 57.
Acknowledgements
22 T. Xiong, W. Cen, Y. Zhang and F. Dong, ACS Catal., 2016, 6,
2462.
23 M. Zhang, X. Bai, D. Liu, J. Wang and Y. Zhu, Appl. Catal., B,
2015, 164, 77.
This work was supported by the National Natural Science
Foundation of China (grant numbers: 51672003 and 51872279).
24 X. Sun, D. Jiang, L. Zhang and W. Wang, Appl. Catal., B, 2018,
220, 553.
References
¨
25 F. Su, S. C. Mathew, L. Mohlmann, M. Antonietti, X. Wang
1 J. Xiao, X. Liu, L. Pan, C. Shi, X. Zhang and J. Zou, ACS Catal.,
2020, 10, 12256.
2 D. Franchi and Z. Amara, ACS Sustainable Chem. Eng., 2020,
8, 15405.
and S. Blechert, Angew. Chem., Int. Ed., 2011, 50, 657.
26 H. Wang, X. Sun, D. Li, X. Zhang, S. Chen, W. Shao, Y. Tian
and Y. Xie, J. Am. Chem. Soc., 2017, 139, 2468.
27 H. Wang, S. Jiang, S. Chen, D. Li, X. Zhang, W. Shao, X. Sun,
J. Xie, Z. Zhao, Q. Zhang, Y. Tian and Y. Xie, Adv. Mater.,
2016, 28, 6940.
28 J. Ran, T. Y. Ma, G. Gao, X. W. Du and S. Z. Qiao, Energy
Environ. Sci., 2015, 8, 3708.
29 S. Hu, L. Ma, J. You, F. Li, Z. Fan, F. Wang, D. Liu and J. Gui,
RSC Adv., 2014, 4, 21657.
30 A. Dandia, S. L. Gupta, P. Saini, R. Sharma, S. Meena and
V. Parewa, Curr. Res. Green Sustainable Chem., 2020, 3,
100039.
31 Y. Zhang, T. Mori, J. Ye and M. Antonietti, J. Am. Chem. Soc.,
2010, 132, 6294.
32 S. Guo, Z. Deng, M. Li, B. Jiang, C. Tian, Q. Pan and H. Fu,
Angew. Chem., Int. Ed., 2016, 55, 1830.
33 M. Zhang, J. Xu, R. Zong and Y. Zhu, Appl. Catal., B, 2014,
147, 229.
´
´
`
3 F. Parrino, M. Bellardita, E. I. Garcıa-Lopez, G. Marcı,
V. Loddo and L. Palmisano, ACS Catal., 2018, 8, 11191.
4 S. Zhang, Y. Zhao, R. Shi, C. Zhou, G. I. N. Waterhouse,
L. Wu, C. H. Tung and T. Zhang, Adv. Energy Mater., 2020,
10, 1901973.
5 Y. Zhao, Y. Zhao, R. Shi, B. Wang, G. I. N. Waterhouse,
L. Z. Wu, C. H. Tung and T. Zhang, Adv. Mater., 2019, 31,
1806482.
6 X. Sun, X. Luo, X. Zhang, J. Xie, S. Jin, H. Wang, X. Zheng,
X. Wu and Y. Xie, J. Am. Chem. Soc., 2019, 141, 3797.
7 E. Frick, C. Schweigert, B. B. Noble, H. A. Ernst, A. Lauer,
Y. Liang, D. Voll, M. L. Coote, A. N. Unterreiner and
C. Barner-Kowollik, Macromolecules, 2016, 49, 80.
8 P. Burger, A. Casale, A. Kerdudo, T. Michel, R. Laville,
F. Chagnaud and X. Fernandez, Food Chem., 2016, 210, 613.
9 J. Du, H. Singh and T. H. Yi, Bioprocess Biosyst. Eng., 2016, 39,
1923.
34 X. Zhou, Z. Luo, P. Tao, B. Jin, Z. Wu and Y. Wang, Mater.
Chem. Phys., 2014, 143, 1462.
10 Y. He and Y. Xue, J. Phys. Chem. A, 2010, 114, 9222.
11 S. Wang, J. Zhan, K. Chen, A. Ali, L. Zeng, H. Zhao, W. Hu,
L. Zhu and X. Xu, ACS Sustainable Chem. Eng., 2020, 8, 8214.
12 Y. Li, S. Jin, X. Xu, H. Wang and X. Zhang, J. Appl. Phys., 2020,
127, 170903.
13 H. Wang, S. Jiang, W. Liu, X. Zhang, Q. Zhang, Y. Luo and
Y. Xie, Angew. Chem., Int. Ed., 2020, 59, 11093.
14 F. He, Z. Wang, Y. Li, S. Peng and B. Liu, Appl. Catal., B, 2020,
269, 118828.
15 Y.-P. Zhu, T. –Z. Ren and Z. –Y. Yuan, ACS Appl. Mater.
Interfaces, 2015, 7, 16850.
16 M. Zhu, S. Kim, L. Mao, M. Fujitsuka, J. Zhang, X. Wang and
T. Majima, J. Am. Chem. Soc., 2017, 139, 13234.
35 G. Liu, P. Niu, C. Sun, S. C. Smith, Z. Chen, G. Q. Lu and
H. M. Cheng, J. Am. Chem. Soc., 2010, 132, 11642.
36 H. Xu, J. Yan, X. She, L. Xu, J. Xia, Y. Xu, Y. Song, L. Huang
and H. Li, Nanoscale, 2014, 6, 1406.
37 Q. Lin, L. Li, S. Liang, M. Liu, J. Bi and L. Wu, Appl. Catal., B,
2015, 163, 135.
38 J. Huang, L. Dou, J. Li, J. Zhong, M. Li and T. Wang, J.
Hazard. Mater., 2021, 403, 123857.
39 J. E. Perez, M. Kumar, J. S. Francisco and A. Sinha, J. Phys.
Chem. A, 2017, 121, 1022.
40 K. Ranjan, K. Dharamvir and V. K. Jindal, Phys. B, 2005, 365,
121.
12686 | RSC Adv., 2021, 11, 12682–12686
© 2021 The Author(s). Published by the Royal Society of Chemistry