Highly efficient degradation of phenol from wastewater: Via an electro-catalytic oxidation approach with a CeO2-CuO cathode

Article abstract of DOI:10.1039/c8ra00983j

The development of highly efficient cathode materials for the electro-catalytic oxidation of phenol from wastewater is of vital importance for environment protection. Herein, we develop an effective CeO₂-CuO electrocatalyst for 2-electron oxygen reduction reaction (ORR) to generate H₂O₂, and then applied it as the cathode for the electro-catalytic oxidation of phenol. Results showed that the CeO₂-CuO cathode with different contents of CuO exhibited a higher yield of H₂O₂ than those of CuO and CeO₂, and the highest yield of H₂O₂ (114 mg L^-1) was achieved with a CuO content of 13.4%. The resultant CeO₂-CuO-13.4% cathode demonstrated a high degradation rate of 91% after 180 min, which was 1.82-fold and 1.52-fold higher than pure CuO (50%) and CeO₂ (60%) electrodes, respectively. Furthermore, the degradation rate of phenol via the electro-catalytic oxidation technology by using a CeO₂-CuO cathode significantly outperformed that of the chemical oxidation approach. The outstanding degradation performance of the CeO₂-CuO cathode is attributed to the high yield of H₂O₂ and the strong interaction of CeO₂ and CuO.

Full text of DOI:10.1039/c8ra00983j

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Highly efficient degradation of phenol from
wastewater via an electro-catalytic oxidation
Cite this: RSC Adv., 2018, 8, 15167
approach with a CeO –CuO cathode
2
Jiankang Luo,
Huan Zhang and Zenghe Li*
The development of highly efficient cathode materials for the electro-catalytic oxidation of phenol from
wastewater is of vital importance for environment protection. Herein, we develop an effective CeO
CuO electrocatalyst for 2-electron oxygen reduction reaction (ORR) to generate H , and then applied
it as the cathode for the electro-catalytic oxidation of phenol. Results showed that the CeO –CuO
than those of CuO and CeO
2
–
2 2
O
2
cathode with different contents of CuO exhibited a higher yield of H
2
O
2
2
,
À1
and the highest yield of H
CeO
fold and 1.52-fold higher than pure CuO (50%) and CeO
the degradation rate of phenol via the electro-catalytic oxidation technology by using a CeO
cathode significantly outperformed that of the chemical oxidation approach. The outstanding
degradation performance of the CeO –CuO cathode is attributed to the high yield of H and the
strong interaction of CeO and CuO.
2
O
2
(114 mg L ) was achieved with a CuO content of 13.4%. The resultant
2
–CuO-13.4% cathode demonstrated a high degradation rate of 91% after 180 min, which was 1.82-
(60%) electrodes, respectively. Furthermore,
–CuO
2
Received 1st February 2018
Accepted 10th April 2018
2
DOI: 10.1039/c8ra00983j
2
2 2
O
rsc.li/rsc-advances
2
9,12
toward phenol. Therefore, there is an urgent need but it is still
a signicant challenge to develop an efficient cathode material
1
Introduction
The phenolic compound is one kind of hazardous pollutant in with a high yield of H O for the removal of phenol.
2 2
wastewater discharged from chemical, petrochemical and phar-
Platinum, ruthenium, palladium and other precious metals
1
13–15
maceutical industries, which has drawn much public concern are the preferred cathode materials
due to their high cata-
due to its highly toxic features. Consequently, a variety of lytic activity and good durability. However, their high cost and
2
3
approaches, such as physical adsorption, coagulation, biolog- scarce reserve are hindering the widespread application of
4
5
ical treatment, chemical oxidation, and electro-catalytic oxida- precious metals. Hence, considerable attentions have been paid
6
tion technology, have been adopted to remove phenol from to the development of metal oxides (such as CeO
2
, CuO, MnO
2
,
16–19
wastewater. Among them, the electro-catalytic oxidation tech- and La
O
2
).
As one of the rare earth oxides, CeO has
3
2
nology is considered to be one of the most effective approaches attracted great attention owing to its high oxygen storage
for the removal of phenol due to its high efficiency, low cost, and capacity and excellent redox property due to the presence of
4
+
3+ 20
7
environment-friendly features (no serious secondary pollution).
The electro-catalytic oxidation technology usually involves the
electrogeneration of H O in situ via the 2-electron oxygen decomposed into the oxidative cOH, which is expected as
Ce /Ce . Furthermore, CeO
H
2
can promote the generation of
2
O
2
via catalyzing the 2-electron ORR, and then H
2 2
O
can be
21
2
2
reduction reaction (ORR) and subsequently generates the a promising candidate of cathode materials for the removal of
hydroxyl radical (cOH) that can degrade the organic pollutant to phenol. However, the CeO cathode still suffered from a low
degradation efficiency probably due to its low catalytic activity
Previously studies indicated that the efficiency of electro-catalytic of 2-electron ORR with a low yield of H . To further improve
oxidation technology largely depended on the choice of the the catalytic activity, the CeO -based metal oxide composites
such as have emerged as effective electrocatalysts due to the strong
2
8–10
2 2
form simple organic compounds (e.g., CO and/or H O).
O
2 2
2
9–11
cathode materials, in which the carbon materials,
graphite, mesh porous carbon, and activated carbon ber as the interaction between CeO
electrocatalyst for ORR, have been widely investigated due to ported that during the chemical oxidation of phenol, the CeO
their high catalytic activity, low cost, and rich-resources. CuO composite cathode exhibited a remarkable catalytic activity
However, most reported carbon materials still exhibited a low for promoting the decomposing of the extra added H , and
22
2
and other metal oxides. It was re-
2
–
2 2
O
23
yield of H
2
O
2
, causing an insufficient degradation efficiency thus resulting in a high degradation efficiency. However, to
the best of our knowledge, the CeO –CuO composite cathode
2
for the degradation of phenol by the electro-catalytic oxidation
technology has rarely been reported.
Beijing University of Chemical Technology, Beijing 100029, PR China. E-mail: lizh@
mail.buct.edu.cn
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 15167–15172 | 15167

View Article Online
RSC Advances
Paper
2
In this work, a highly efficient CeO –CuO composite cathode 2.4 Characterization
for the electro-catalytic oxidation of phenol was synthesized by
The crystal structures of the samples were identied by powder
X-ray diffraction (XRD, Rigaku Ultimal II) in the 2q range of 10–
the sol–gel method. The resultant CeO –CuO cathode exhibited
2
À1
a high yield of H O as high as 114 mg L aer the degradation
ꢀ
ꢀ
À1
2
2
7
0 at a scanning step of 10 min . X-ray photoelectron spec-
troscopy (XPS) measurements were performed on an ESCALAB
50 electron spectrometer with a monochromatic 150 W Al Ka
source with the binding energy calculated referring to C 1s
284.8 eV). The morphology of the as-synthesized samples was
for 180 min, leading to an excellent degradation performance
with the degradation rate of 91%, signicantly higher than that
of chemical oxidation of phenol (79%). Furthermore, the effect
2
2 2
of CuO content on the yield of H O and the degradation
(
performance, and the degradation mechanism of CeO
were also investigated.
2
–CuO
examined on scanning electron microscopy (SEM, 23200N,
Hitachi) and high resolution transmission microscopy (HR-
TEM, Tecnai G220). The inductively coupled plasma (ICP)
analysis was conducted with a Shimadzu ICPS-7500 instrument
to determine the content of element. Nitrogen sorption
measurements were conducted at an AS-AP-2000 instrument to
determine the specic surface area (SBET) based on Brunauer–
2
Introduction
2.1 Synthesis of the CeO
2
–CuO electrocatalyst
The CeO
2
–CuO electrocatalysts with different CuO contents (0,
5.5, 8.5, 13.4, 31.8, and 58 wt%) were prepared by the sol–gel
Emmett–Teller (BET) model. The concentration of H O2 was
2
approach, respectively. In the typical synthesis, a certain
determined by UV-vis spectrophotometer (mini-1240) at 400 nm
amount of Ce(NO ) $6H O and Cu(NO ) $3H O were dissolved
3
3
2
3 2
2
with potassium titanyl oxalate (C K O Ti$2H O) as color indi-
4
2
9
2
into the deionized water and stirred for 0.5 h. Then, 2.1 g of
citric acid was added to the above solution with continuously
cator. The degradation rate of phenol was measured by a high
performance liquid chromatography (HPLC, Agilent 1260).
ꢀ
stirring. Aerwards, the mixed solution was heated at 80 C in
a water bath and stewed for 2 h. The resultant product was dried
ꢀ
ꢀ
at 100 C for 12 h and then heat-treated at 700 C in air atmo-
3
Results and discussion
2
sphere for 3 h to generate the CeO –CuO composite.
3
.1 Structural characterization
The crystal structures of the CeO
The foamed nickel (2 cm  2 cm) was used as the electrode different CuO contents were identied by XRD. As shown in
substrate of cathode. Typically, 0.4 g of graphite and 0.2 g of Fig. 1, all the CeO –CuO electrocatalysts exhibited several
2
2.2 Preparation of the CeO –CuO cathode
2
–CuO electrocatalysts with
2
ꢀ
ꢀ
ꢀ
ꢀ
polytetrauoroethylene (2% PTFE) were dispersed in ethanol, strong diffraction peaks at 28.72 , 33.24 , 47.64 and 56.42 ,
and then the obtained mixture was homogeneously coated on respectively, which are assigned to the (111), (200), (220) and
the foamed nickel. Subsequently, the coated foamed nickel was (311) planes of CeO
. Obviously, the intensity of these peaks was
dried at 100 C aer the pressing treatment to obtain the gas signicantly higher than that of CeO , suggesting an improved
diffusion layer (GDL). Aerwards, a homogeneously dispersed crystalline of CeO –CuO composite. However, the typical
2
ꢀ
2
2
electrocatalyst ink (ultrasonically dispersing 50 mg of electro- diffraction peaks of CuO were not detected as the CuO content
catalyst, 0.4 g of Vulcan XC-72 carbon black, and 0.2 g of PTFE in was lower than 13.4 wt%, probably due to its low content and/or
2
.5 mL ethanol and deionized water with a volume ratio of 1) low crystalline. When the CuO content was increased to
ꢀ
was coated on the GDL, and then the GDL was dried at 100 C 13.4 wt%, the typical diffraction peaks of CuO phase appeared.
ꢀ
ꢀ
ꢀ
followed by the pressing treatment to obtain the catalyst layer. The peaks located at 35.45 and 38.65 are assigned to (111) and
Finally, the cathode electrode was obtained by the heat- (111) planes of CuO, respectively, and the intensity of both
ꢀ
treatment of the catalyst layer at 300 C for 1 h under the air peaks was found to increase with the increase of CuO content.
atmosphere.
2.3 Electro-catalytic degradation of phenol
The electro-catalytic degradation of phenol was conducted in
a standard three-electrode system with a graphite sheet (2 cm Â
2
cm) as anode and a CeO –CuO (2 cm  2 cm) composite as
2
cathode, and a saturated calomel electrode (SCE) as reference
electrode. The H was produced by the reduction of oxygen at
2 2
O
cathode in an electrochemical cell with 100 mL of deionized
water bubbled with oxygen, and then a certain amount of liquid
was extracted in which the concentration of H
2 2
O was measured
at an interval of 20 min. The initial concentration of phenol was
À1
À2
1
00 mg L and the current density is 40 mA cm . The Na SO
2 4
was used as supporting electrolyte with the concentration of
À1
0
7
.1 mol L , and the initial pH of the solution was adjusted to
2
Fig. 1 XRD patterns of the CeO –CuO electrocatalysts with different
CuO contents.
.0 by 1 M H
2
SO
4
.
15168 | RSC Adv., 2018, 8, 15167–15172
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
The nitrogen adsorption–desorption measurements were
RSC Advances
conducted to determine the specic surface area of the CeO2–
CuO electrocatalysts. As shown in Table 1, compared with the
2
À1
pure CeO (S : 43.8 m g ), all the CeO –CuO electrocatalysts
2
BET
2
2
À1
possessed lower specic surface area (SBET: 23.2–40.4 m g ),
which might be attributed to the higher crystallinity of CeO
CuO with large particle size than that CeO
analysis. The TEM images in Fig. 2a displayed that the CeO
2
–
2
as indicated by XRD
2
–
CuO electrocatalyst exhibited a strip-like morphology with the
particle size of approximately 20–40 nm. Further HR-TEM
observation (Fig. 2b) showed that the lattice fringe spacing of
Fig. 2 Representative TEM image (a) and HR-TEM image (b) of CeO
CuO-13.4%.
2
–
0
.31 nm was corresponded to the (111) plane of CeO , while the
2
ꢀ
lattice fringe spacing of 0.25 nm was assigned to the (111) plane 3.2 Electrogeneration of H O and degradation of phenol
2
2
of CuO. This result further conrmed the formation of CeO
CuO composite, which was in accordance with the XRD
analysis.
The surface composition and chemical state of the CeO –
2
CuO electrocatalyst were investigated by XPS measurement. As
2
–
À
The yield of H
2 2 2 2
O generated via 2-electron ORR (O + 2H O + 4e
À
/
H
2
O
2
+ 2OH ) catalyzed by the CeO
2
–CuO cathode was
determined by the UV-vis spectrophotometer (Fig. 4a–b). It was
observed that the CuO content had a signicant inuence on
the H O yield, exhibiting a volcano-shaped relation with the
highest H O yield at the CuO content of 13.4%. The H O yield
2 2 2 2
–CuO-13.4% cathode was determined as high as
14 mg L , signicantly outperformed CuO (25 mg L ) and
CeO (60 mg L ), and higher than that of reported CeO elec-
2 2
trocatalyst in the literature, which is very favorable to promoting
the degradation of phenol by the strong oxidizing agents. These
2
2
shown in Fig. 3a, the peaks located at 530 eV, 285 eV, 920–
9
60 eV, and 880–920 eV are ascribed to the O 1s, C 1s, Cu 2p,
for the CeO
1
2
and Ce 3d, respectively. The C element is likely to due to the
indenite hydrocarbon from the XPS apparatus. The Ce 3d
À1
À1
À1
spectra of both CeO
deconvoluted into eight peaks, in which the peaks labelled
as V, V , V , U, U , and U are associated with characteristic of
Ce state, while the peaks labelled as V and U are assigned
2 2
and CeO –CuO in Fig. 3b–c can be
2
3
2
3
results indicated the CeO –CuO cathode can accelerate the 2-
4
+
2
1
1
electron ORR pathway to generate a high yield of H O .
3
+
21
4+
3+
2 2
to the Ce state, indicating the existence of Ce /Ce redox
The effect of CuO content on the degradation rate towards
phenol was investigated as shown in Fig. 4c–d. For comparison,
couple in CeO and CeO –CuO. Furthermore, the content of
2
2
3
+
Ce was calculated to be 20.02% for CeO
higher than that of CeO (14.19%), which probably attributed
to the strong interaction between CuO and CeO2. The high
2
–CuO, signicantly
the degradation rates of phenol by using the pure CeO
were also evaluated in the identical condition, respectively. As
expected, the CeO –CuO-13.4% cathode exhibited a highest
2
and CuO
2
3
+
2
content of Ce for CeO
2
–CuO is believed benecial for the
degradation rate among all the samples, with the degradation
rate as high as 91% aer the degradation for 180 min, which
was signicantly higher than those of CuO (50%) and CeO2
enhancement concentration of the oxygen vacancy, leading to
2
1
a superior catalytic activity of 2-electron ORR. Furthermore,
the binding energies of Ce 3d in CeO –CuO were all shied
2
(
2
60%). The strong interaction between CeO and CuO as
positively in comparison to CeO , once again conrming
2
2
a strong interaction between CeO and CuO. The XPS spec-
trum of Cu 2p in Fig. 3d can be deconvoluted into four peaks,
in which the peaks located at 933.9 eV, 952.66 eV and the
2
+
24
shake-up satellite peak can be assigned to the Cu state,
+
while the peak located at 933.06 eV is related to the Cu
2
5
+
species. The presence of Cu species is favorable to the
generation of $OH by decomposing H O , leading to an
2
2
2
6
enhancement of degradation performance.
2
Table 1 Specific surface areas of CeO –CuO with different CuO
contents
2
À1
Sample
SBET/m g
CeO
CeO
CeO
CeO
CeO
CeO
2
2
2
2
2
2
43.8
40.4
37.1
35.6
30.3
23.2
–CuO-5.5%
–CuO-8.5%
–CuO-13.4%
–CuO-31.8%
–CuO-58.0%
Fig. 3 XPS survey spectrum of CeO
resolution Ce 3d spectra of CeO (b) and CeO
high-resolution Cu spectrum of CeO –CuO-13.4%(d).
2
–CuO-13.4% (a), and high-
2
2
–CuO-13.4% (c), and
2
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 15167–15172 | 15169

View Article Online
RSC Advances
Paper
of phenol. Unlike the chemical oxidation approach that
required the extra addition of H O , the electro-catalytic
2
2
oxidation technology can produce H O in situ via 2-electron
2
2
ORR catalyzed by the CeO –CuO electrocatalyst, promoting the
2
generation of H
2 2
O and $OH, and thus leading to a high
degradation rate of phenol.
3.3 Degradation mechanism of phenol
In order to determine the major active species in the electro-
catalytic degradation of phenol, Fe(II)–EDTA and tert-butyl
2 2
alcohol (TBA) were used as the scavengers for H O and $OH,
21
respectively, and the degradation rate of phenol with and
without scavengers were evaluated. As shown in Fig. 6, when the
scavenger (TBA) of $OH was added into the solution, the degra-
dation rate of phenol obviously decreased by 31%, while for the
addition of H O scavenger (Fe(II)–EDTA), the degradation rate
Fig. 4 Effect of CuO content of CeO
2
–CuO on the H
2
O
2
yield (a and
2 2
b) and degradation rate of phenol (c and d).
only reduced by 4.5%. This result clearly revealed that $OH
played a more important role for the degradation of phenol than
H O
2 2
in the electro-catalytic oxidation process. In this work, the
indicated by XPS analysis was believed favorable to the genera- CeO
tion of high yield of H
and $OH for the efficient degradation catalyst to produce H
2
–CuO composite was used as the 2-electron ORR electro-
O
2 2
2 2
O
, and then catalyzed the decomposition
À
of phenol. These results further conrmed the electro-catalytic of H
O
2 2
to generate HO
2
and further turn into $OH. The
oxidation technology by using CeO –CuO composite cathode
2
was an effective approach for the degradation of phenol.
In order to get insight into the merits of the electro-catalytic
oxidation technology, the degradation rate of phenol by the
2
chemical oxidation approach using CeO –CuO cathode was
evaluated. As shown in Fig. 5, the degradation rates at different
time by the electro-catalytic oxidation technology were all
higher than those of the chemical oxidation approach. Aer the
degradation for 180 min, the degradation rate of phenol by the
electro-catalytic oxidation (91%) was 1.14-fold of that of the
chemical oxidation (80%), indicating that the electro-catalytic
oxidation technology is an effective approach for degradation
Fig. 6 The degradation rate of phenol with or without 10 mL scav-
À1
engers (1 mol L ).
2
Fig. 5 Degradation curves of phenol using CeO –CuO cathode with Fig. 7 The degradation mechanism of the electro-catalytic oxidation
the electro-catalytic oxidation and chemical oxidation approaches.
2
of phenol with CeO –CuO cathode.
15170 | RSC Adv., 2018, 8, 15167–15172
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
2
that of chemical oxidation approach by using CeO –CuO
cathode (80%). The outstanding degradation performance of
CeO –CuO cathode is attributed to the high yield of H O and
2
2 2
strong interaction of CeO and CuO. Degradation mechanism
2
analysis indicated that $OH played a more important role for
the degradation of phenol than H
oxidation process.
2 2
O in the electro-catalytic
Conflicts of interest
There are no conict to declare.
Notes and references
Fig. 8 The stability of the electrode investigated by nine successive
measurements.
1
2
R. M. Liou and S. H. Chen, J. Hazard. Mater., 2009, 172, 498.
B. I. Dvorak and D. A. Boadway, Water Environ. Res., 1993, 65,
27–838.
8
3
4
5
6
X. Hui, R. Jiao, F. Xiao and D. Wang, Colloids Surf., A, 2016,
490, 189–199.
K. C. Chen, Y. H. Lin, W. H. Chen and Y. C. Liu, Enzyme
Microb. Technol., 2002, 31, 490–497.
M. P ´e rez, F. Torrades, J. A. Garc ´ı a-Hortal, X. Dom `e nech and
J. Peral, Appl. Catal., B, 2002, 36, 63–74.
J. L. Chen, J. Y. Wang, C. C. Wu and K. Y. Chiang, Colloids
Surf., A, 2011, 379, 163–168.
generated $OH can oxidize the phenol to form CO and/or H O
2
2
21
(Fig. 7). The reactions are as follows:
À
O
2
+ 2H
2
O + 2e / H
2
O
2
+ 2OH
(1)
(2)
(3)
À
À
À
O + 2OH + 2e / 2HO2
2
2À
2
2
+ H O
H
2
O
2
+ HO / 2$OH + O
7
8
Y. J. Feng and X. Y. Li, Water Res., 2003, 37, 2399–2407.
E. Guinea, J. A. Garrido, R. M. Rodr ´ı guez, P. L. Cabot,
C. Arias, F. Centellas and E. Brillas, Electrochim. Acta, 2010,
Furthermore, the CeO –CuO electrocatalyst possessed the
redox couples of Ce /Ce and Cu /Cu , which can promote
2
3+
4
+
2+
+
55, 2101–2115.
the transformation of H O to $OH. The reactions are as
2
2
9
A. R. Khataee, M. Safarpour, M. Zarei and S. Aber, J.
Electroanal. Chem., 2011, 659, 63–68.
21,26
follows:
4
+
À
3+
+
10 G. Xia, Y. Lu and H. Xu, Electrochim. Acta, 2015, 158, 390–
96.
11 W. L. Chou, C. T. Wang, C. C. Huang and C. Y. Wang,
Ce + e / Ce
(4)
(5)
3
2
+
À
Cu + e / Cu
Fresenius Environ. Bull., 2013, 22, 2234–2241.
3
Ce + H
+
4+
/ Ce + $OH
2
O
2
(6) 12 A. D. Pozzo, L. D. Palma and C. Merli, J. Appl. Electrochem.,
005, 35, 413–419.
(7) 13 K. J. Kinoshita, J. Electrochem. Soc., 1990, 137, 845–848.
2
+
2+
Cu + H O / Cu + $OH
2
2
1
4 H. Wang, J. K. Lee, A. Moursi and J. J. Lannutti, Electrochim.
Acta, 2008, 53, 6402–6409.
5 Y. Zheng, Y. Jiao, Y. Zhu, L. H. Li, Y. Han, Y. Chen,
M. Jaroniec and S. Z. Qiao, J. Am. Chem. Soc., 2016, 138,
As shown in Fig. 8, the phenol removal rate was only declined
from 91% to 80% aer nine cycles and no obvious change of the
electrode was observed during the experiment, demonstrating
that the electrode is stable and favorable for practical applica-
tion for phenol degradation.
1
16174.
1
6 M. H. M. T. Assumpç ˜a o, A. Moraes, R. F. B. D. Souza,
I. Gaubeur, R. T. S. Oliveira, V. S. Antonin,
G. R. P. Malpass, R. S. Rocha, M. L. Calegaro and
M. R. V. Lanza, Appl. Catal., A, 2012, 411–412, 1–6.
4
Conclusions
In summary, an efficient CeO
electron ORR was synthesized and applied as the cathode for
the electro-catalytic oxidation of phenol. Results showed that 18 G. Yu, L. Hu, N. Liu, H. Wang, M. Vosgueritchian, Y. Yang,
the CeO –CuO cathode with different contents of CuO exhibited Y. Cui and Z. Bao, Nano Lett., 2011, 11, 4438–4442.
a higher yield of H , and the 19 N. Wang, J. Liu, W. Gu, Y. Song and F. Wang, RSC Adv., 2016,
highest yield of H
6, 77786–77795.
2
–CuO electrocatalyst for the 2- 17 D. S. Kim, G. H. Lee, S. Lee, J. C. Kim, H. J. Lee, B. K. Kim and
D. W. Kim, J. Alloys Compd., 2016, 275–280.
2
2
O
2
than those of CuO and CeO
2
À1
2
O
2
(114 mg L ) was achieved at CuO content
of 13.4%. The resultant CeO –CuO cathode demonstrated an 20 L. Jiang, M. Yao, B. Liu, Q. Li, R. Liu, H. Lv, S. Lu, C. Gong,
2
excellent degradation performance with a removal rate of 91%
aer the degradation for 180 min, signicantly higher than that 21 L. Yu, X. Yu, T. Sun and N. Wang, J. Nanosci. Nanotechnol.,
of CuO (50%) and CeO (60%) electrodes, and even higher than 2015, 15, 4920.
B. Zou and T. Cui, J. Phys. Chem. C, 2012, 116, 11741–11745.
2
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 15167–15172 | 15171

View Article Online
RSC Advances
Paper
2
2
2
2 W. Yang, D. Li, D. Xu and X. Wang, J. Nat. Gas Chem., 2009, 25 S. Ho ˇc evar, U. O. Kra ˇs ovec, B. Orel, A. S. Aric ´o and H. Kim,
8, 458–466. Appl. Catal., B, 2000, 28, 113–125.
3 F. I. P. Massa, P. Haure and R. Fenoglio, J. Hazard. Mater., 26 Y. Cheng, Y. Lin, J. Xu, J. He, T. Wang, G. Yu, D. Shao,
1
2011, 190, 1068–1073.
W. H. Wang, F. Lu and L. Li, Appl. Surf. Sci., 2016, 366,
120–128.
4 K. N. Rao, P. Venkataswamy and B. M. Reddy, Ind. Eng. Chem.
Res., 2011, 50, 11960–11969.
15172 | RSC Adv., 2018, 8, 15167–15172
This journal is © The Royal Society of Chemistry 2018