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Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene
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Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene E.S. Baeissa∗ Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
a r t i c l e
i n f o
Article history: Received 19 July 2016 Revised 7 November 2016 Accepted 10 November 2016 Available online xxx Keywords: Holmium hydroxide nanowires Silver depositing Nitrobenzene reduction
a b s t r a c t Holmium hydroxide nanowires were prepared by a hydrothermal method, while silver was deposited on the surface of holmium hydroxide nanowires by a photoassisted deposition method. Holmium hydroxide nanowires and silver deposited holmium hydroxide nanowires were characterized by different techniques such as XRD, PL, XPS, UV–vis, TEM and BET surface area measurements. The photocatalytic performance of holmium hydroxide nanowires and silver deposited holmium hydroxide nanowires was measured by studied the visible light reduction of nitrobenzene to aniline. The results reveal that the form of deposited silver is a metallic silver and it well dispersed on the surface of holmium hydroxide nanowires. Band gap of holmium hydroxide nanowires was decreased from 2.92 to 2.64 eV by depositing of silver. Weight percent of deposited silver plays important role in control band gap and photocatalytic activity of holmium hydroxide nanowires. 0.3 wt% silver deposited holmium hydroxide has the lowest band gap and the highest photocatalytic activity for reduction of nitrobenzene. © 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
1. Introduction One of the most important chemicals and intermediates in the production of dyes, pigments, pesticides and pharmaceuticals is aniline [1,2]. Aniline was prepared by hydrogenation of nitrobenzene. In hydrogenation process, the most common catalysts are noble metals catalysts such as Au, Pd and Pt and transitions metals catalysts such as Ni and Cu [1–3], but, the hydrogenation process needs high hydrogen pressure, high temperature and high reaction time [3,4]. The preparation of aniline was done at room temperature and atmospheric pressure by using photocatalytic process [5–15]. The most famous photocatalyst it titanium dioxide due to its stability, and high photocatalytic activity. But, TiO2 absorb in UV region and percent of UV light in solar spectrum is about 3–5%, which hinder using of TiO2 in visible region [16]. Many methods were used to shift absorption of TiO2 from UV to visible region such as metal and non metal doping and coupling with another semiconductor materials [17–25]. Recently, new photocatalysts which have narrow band gaps were prepared. Perovskites photocatalysts have narrow band gap [26–32]. The drawbacks of perovskites photocatalysts are high electron–hole recombination rate and low surface area. Also, researchers prepare polymer-like semiconductor materials that are considered to be an efficient photocatalyst using visible light for environmental purification and ∗
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hydrogen production [33–37]. Polymer-like semiconductor materials have many properties, such as high stability, low cost and a controllable surface. Therefore, a polymer-like semiconductor material can be considered as a new material for solar energy and environmental applications. There are three drawbacks for using it as a commercial photocatalyst: a small surface area, high recombination rate of electron–hole pairs and a lack of absorption above 460 nm. Recently, hydroxide-based photocatalysts such as In(OH)3 and InOOH have high photocatalytic activity for photodegradation of benzene [38,39]. To best of our knowledge, there is no reported about preparation of holmium hydroxide or silver doped holmium hydroxide nanowires. Also, there is no published paper about synthesis of aniline by hydroxide photocatalyst. Thus, this work aims to preparation of holmium hydroxide and silver deposited holmium hydroxide nanowires for preparation of aniline from visible light photocatalytic reduction of nitrobenzene. 2. Experimental 2.1. Synthesis of photocatalyst Holmium hydroxide nanowires were prepared by a hydrothermal method. In a typical procedure, 30 ml of ethylene glycol, 98.8% was mixed with 20 ml of isopropanol, 99% and 5 mmol of holmium nitrate pentahydrate was added dropwise to them and resulting mixture was stirred for 30 min at room temperature. The obtained sol was heated at 80 °C to produce gel and the gel was dried for
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Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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Jasco, Japan) in air at room temperature to detect absorption over the range 20 0–80 0 nm. And photoluminescence emission spectra (PL) were obtained with a Shimadzu RF-5301 fluorescence spectrophotometer.
0.40 wt % Ag-Ho(OH)3
2.3. Photocatalytic performance
0.10 wt % Ag-Ho(OH)3
Ho(OH)3
201
110 101
15.6 16.0 16.4 2-theta, degree
16.8
211
15.2
100
Intensity, a.u.
Intensity, a.u.
0.30 wt % Ag-Ho(OH)3 0.20 wt % Ag-Ho(OH)3
0.40 wt % Ag-Ho(OH)3 0.30 wt % Ag-Ho(OH)3 0.20 wt % Ag-Ho(OH)3 0.10 wt % Ag-Ho(OH)3 Ho(OH)3
10
15
20
25
30
35
40
45
50
55
60
65
70
2-theta, degree Fig. 1. XRD of holmium hydroxide and silver doped holmium hydroxide nanowires.
24 h at 100 °C. The obtained powders were dispersed in 80 ml of distilled water and heated at 180 °C for 24 h using an autoclave. After cooling temperature of autoclave, the obtained powders were washed many times by distilled water and absolute ethanol, then dried for 24 h at 80 °C. Different weight percents of silver (0.1, 0.2. 0.3 and 0.4 wt% Ag) were deposited on the surface of holmium hydroxide nanowires by a photoassisted deposition method. In a typical procedure, metallic silver was deposited on surface of holmium hydroxide nanowires using strong UV lamp (150 W) and in presence of silver nitrate solution. 2.2. Characterization techniques Nanostructure morphology and sample dimensions were measured using JEOL-JEM-1230 transmission electron microscopy (TEM). Samples were suspended in ethanol and ultra-sonicated for 30 m. A small amount was then coated with carbon, dried on a copper grid, and loaded into the TEM. Also, N2 -adsorption measurements were taken on treated samples (2 h under vacuum at 100 °C) with a Nova 2000 series Chromatech apparatus at 77 K to calculate surface area. Crystalline phase was determined by powder X-ray diffraction (XRD) using Bruker axis D8 with Cu Kα ra˚ at room temperature. X-ray photoelectron diation (λ = 1.540 A) spectroscopy (XPS) measurements were performed on a Thermo Scientific K-ALPHA spectrometer. Band gap performance was determined by ultra violet–visible diffuse reflectance spectra (UV– vis-DRS), measured using a UV–vis-NIR spectrophotometer (V-570,
The photocatalytic apparatus consists of two parts: an annular quartz tube and a sealed quartz reactor. A 500-W Xenon lamp (Institute of Electric Light Source, Beijing) with a maximum emission of about 470 nm is the visible light source. A cutoff filter (λ > 420 nm) controlled the light’s wavelength. The lamp was in an empty chamber of the annular tube, and running water passed through the tube’s inner thimble. Continuous cooling kept the reaction solution at approximately 30 °C. The sealed quartz reactor has a diameter of 8.3 cm and is below the lamp. For each photochemical reaction, we ultrasonically dispersed a sample of the photocatalyst (50 mg) in 10 ml nitrobenzene–CH3 OH solution (1/99, v/v). The initial concentration of nitrobenzene (NB) was 8.13 × 10−4 mol/l. The distance between the light source and the surface of the reaction solution was 11 cm. Nitrogen passed through the solution for 0.5 h before illumination to remove dissolved oxygen in the solution, freeing photoinduced electrons to reduce NB. After 2.5 h of illumination, we took the samples from the reaction suspension, centrifuged them at 70 0 0 rpm for 20 min and finally filtered them through a 0.2-μm millipore filter to remove any residual particles. The filtrate was then analyzed using a gas chromatography Agilent GC 7890A model: G3440A Gas Chromatography using 19091J-413 capillary column (30 m × 0.32 μm × 0.25 μm). 2.4. Radical-trapping experiment In order to identify the major active species in the reduction of nitrobenzene, radical-trapping experiments were carried out using three chemicals, disodium ethylenediaminetetraacetate (Na2 EDTA, a hole scavenger), tert-butanol (an • OH radical scavenger) and benzoquinone (a superoxide anion radical scavenger). The conditions radical-trapping experiments are the same as in photocatalytic test except we add one of chemicals to reaction mixture. 2.5. Transient photocurrent tests Indium-tin-oxide slices (ITO) were boiled in a 2 M NaOH solution and sonicated successively in acetone, alcohol, and deionized water for 15 min each. Then, the ITO electrodes were rinsed with deionized water and dried at room temperature. The solution with Ho(OH)3 was dropped onto the pretreated ITO (1.0 cm × 1.0 cm) and then dried at room temperature. The photocurrent intensity recorded using electrochemical workstation, Zahner Zennium, Germany. The photocurrent measurements were carried out in 0.1 M Na2 SO4 solution. The applied potential was 0.2 V and a 500 WXe lamp equipped with a monochromator was used as the irradiation source to produce the monochromatic light at 420 nm.
Table 1 Texture parameters of Ho(OH)3 and Ag–Ho(OH)3 nanowires. Sample
SBET (m2 /g)
St (m2 /g)
Smicro (cm2 /g)
Sext (cm2 /g)
Vp (cm3 /g)
Vmicro (cm3 /g)
Vmeso (cm3 /g)
˚ r (A)
Ho(OH)3 0.10 wt% Ag–Ho(OH)3 0.20 wt% Ag–Ho(OH)3 0.30 wt% Ag–Ho(OH)3 0.40 wt% Ag–Ho(OH)3
40.00 37.00 35.00 33.00 31.00
41.00 38.00 35.00 34.00 31.00
27.00 26.00 25.00 24.00 23.00
13.00 11.00 10.00 09.00 08.00
0.200 0.190 0.160 0.155 0.130
0.150 0.150 0.130 0.120 0.110
0.050 0.040 0.030 0.025 0.020
30.00 35.00 40.00 45.00 50.00
Note: (SBET ) BET-surface area (St ) surface area derived from Vl − t plots. (Smic ) surface area of micropores (Sext ) external surface area. (Vp ) total pore volume (Vmic ) pore volume of micropores. (Vmes ) pore volume of mesopores (r− ) mean pore radius.
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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3
A
Intensity, a.u.
Ho 3d 5/2
166
164
162
160
158
156
Binding energy, eV
B
C Ag 3d
528
Intensity, a.u.
Intensity, a.u.
O 1s
530
532
534
536
538
540
380 378 376 374 372 370 368 366 364 362 360 Binding energy, eV
Binding energy (eV)
Fig. 2. XPS spectres of Ho3d (A); O 1s (B) and Ag 4d (C) for 0.30 wt% Ag–Ho(OH)3 sample.
3. Results and discussions 3.1. Characterizations of photocatalysts Fig. 1 shows XRD of holmium hydroxide and silver deposited holmium hydroxide nanowires. The results reveal that holmium hydroxide and silver deposited holmium hydroxide samples are composed from holmium hydroxide and there are no peaks for silver or silver oxide, due to the weight percent of silver is low detection limit of XRD or the high dispersion of silver on surface of holmium hydroxide. Also, we noticed that peaks intensity of holmium hydroxide phase was decreased and broad by addition of silver. There is a slight right shift in the [100] peak of Ho(OH)3 for the Ag–Ho(OH)3 samples, which suggests that silver has been doped into the Ho(OH)3 lattice. Fig. 2 shows XPS spectres of Ho3d (A); O 1s (B) and Ag4d (C) for 0.30 wt% Ag–Ho(OH)3 sample. The results reveal that the peak at 163.1 eV represents binding energy of Ho3d5/2 which confirm the presence of Ho3+ ion as shown in Fig. 2A. The peak at 532.1 eV represents binding energy of O 1s, which confirm the presence of O ion bonded to H as shown in Fig. 2B. XPS of Ho and O species confirm the formation of Ho(OH)3 , which was agree with XRD results. Also, we noticed that the two peaks at 368.2 and 374.2 eV represent the binding energy of Ag3d5/2 and Ag3d3 /2 , respectively, which confirm the presence of metallic silver as shown in Fig. 2C.
Table 2 Band gap energy of Ho(OH)3 and Ag–Ho(OH)3 nanowires. Sample
Band gap energy (eV)
Ho(OH)3 0.10 wt% Ag–Ho(OH)3 0.20 wt% Ag–Ho(OH)3 0.30 wt% Ag–Ho(OH)3 0.40 wt% Ag–Ho(OH)3
2.90 2.80 2.70 2.63 2.61
Fig. 3 shows TEM images of holmium hydroxide and silver deposited holmium hydroxide nanowires, where (A) Ho(OH)3 ; (B) 0.1 wt% Ag–Ho(OH)3 ; (C) 0.2 wt% Ag–Ho(OH)3 ; (D) 0.3 wt% Ag– Ho(OH)3 and (E) 0.4 wt% Ag–Ho(OH)3 . The results reveal that shape of holmium hydroxide and silver deposited holmium hydroxide samples is nanowires and metallic silver was deposited as dots. Also, we noticed that the dispersion of metallic silver depends on weight percent of deposited silver. 0.3 wt% Ag–Ho(OH)3 sample has the best dispersion of silver on surface of holmium hydroxide. Table 1 shows texture parameters of holmium hydroxide and silver deposited holmium hydroxide nanowires. The values of specific surface area are 40, 37, 35, 33 and 31 m2 /g, for Ho(OH)3 , 0.1 wt% Ag–Ho(OH)3 , 0.2 wt% Ag–Ho(OH)3 , 0.3 wt% Ag–Ho(OH)3 and 0.4 wt% Ag–Ho(OH)3 , respectively. Thus the addition of silver leads to decrease specific surface area of holmium hydroxide and
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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A
B
C
D
E
Fig. 3. TEM images of holmium hydroxide and silver doped holmium hydroxide nanowires, where (A) Ho(OH)3 ; (B) 0.1 wt% Ag–Ho(OH)3 ; (C) 0.2 wt% Ag–Ho(OH)3 ; (D) 0.3 wt% Ag–Ho(OH)3 and (E) 0.4 wt% Ag–Ho(OH)3 .
Ho(OH)3
0.40 wt % Ag-Ho(OH)3
0.10 wt % Ag-Ho(OH)3
0.30 wt % Ag-Ho(OH)3
0.20 wt % Ag-Ho(OH)3
0.20 wt % Ag-Ho(OH)3
0.30 wt % Ag-Ho(OH)3
Reflectance, %
0.10 wt % Ag-Ho(OH)3
0.40 wt % Ag-Ho(OH)3
200
300
Intensity (a. u.)
Ho(OH)3
400
500
600
700
800
Wavelength, nm Fig. 4. UV–vis absorption spectra of holmium hydroxide and silver doped holmium hydroxide nanowires.
these can be attributed to blocking of some pores of holmium hydroxide by depositing of silver as shown in Table 1. Also, we noticed that the values of SBET are very close to values of St , which confirm the presence of mesopores materials.
440
460
480
500
520
540
560
580
600
620
Wavelength (nm) Fig. 5. PL spectra of holmium hydroxide and silver doped holmium hydroxide nanowires.
Fig. 4 shows UV–vis-DRS of holmium hydroxide and silver deposited holmium hydroxide nanowires. The results reveal that holmium hydroxide and silver deposited holmium
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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Fig. 6. Chromatograms of different samples, where A at initial of the reactions; B at medium time and C at finial of the reaction.
hydroxide nanowires absorb in visible region. The absorption edge of holmium hydroxide was increased from 428 to 471 nm by increased weight percent of doped metallic silver from zero to 0.3 wt% and increase weight percent of deposited metallic silver above 0.3 wt% has no significant effect on absorption edges of holmium hydroxide. Therefore, weight percent of deposited metallic silver plays important role in control absorption edge of holmium hydroxide nanowire. The band gap energies of holmium hydroxide and silver deposited holmium hydroxide nanowires were calculated from UV–vis-DRS and values were tabulated in Table 2. The results reveal that the band gap values are 2.90, 2.80, 2.70, 2.63 and 2.61 eV for Ho(OH)3 , 0.1 wt% Ag–Ho(OH)3 , 0.2 wt% Ag–Ho(OH)3 , 0.3 wt% Ag–Ho(OH)3 and 0.4 wt% Ag–Ho(OH)3 , respectively. The reason for the decrease in Eg could be the localized surface plasmon resonance (SPR) effect that was attributed by the Ag NPs [40]. Therefore, the actual Eg of holmium hydroxide was the same, but the SPR added visible light absorbance as results published for Ag/TiO2 [40]. The PL spectra were detected for the different samples which were exited at 265 nm at room temperature. Fig. 5 shows PL spectra of holmium hydroxide and silver deposited holmium hydroxide
nanowires. The results reveal that the PL peak intensity was decreased by increase weight percent of doped metallic silver from zero to 0.3 wt% and increase weight percent of deposited metallic silver above 0.3 wt% has no significant effect on PL peak intensity. Therefore, weight percent of doped metallic silver plays important role in control electron–hole recombination rate of holmium hydroxide nanowire. 3.2. Photocatalytic activities We studied the conversion of nitrobenzene into aniline before studied the photocatalysis process under different conditions such as in presence of light and in absence of photocatalyst, in presence of photocatalyst and in absence of light. Gas chromatogram results reveal that nitrosobenzene and aniline are main products as shown in Fig. 6A–C. Also, we noticed that in both cases, there is detection of aniline or nitrosobenzene, which means the conversion of nitrobenzene cannot carried out by UV light only or photocatalyst only. Fig. 7 shows effect of weight percent of silver on photocatalytic activity of holmium hydroxide nanowires for conversion of nitrobenzene to aniline. The results reveal that the photocatalytic
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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No catalyst NO light Ho(OH)3
90
100
Conversion of nitrobenzene to aniline, %
Conversion of nitrobenzene to aniline, %
100
0.1 wt % Ag-Ho(OH)3 0.2 wt % Ag-Ho(OH)3
80
0.3 wt % Ag-Ho(OH)3 0.4 wt % Ag-Ho(OH)3
70 60 50 40 30 20 10 0 0
15
30
45
60
75
90
105
120
135
90 80 70 60 50 40 30 20 10 0
150
1
Irradiation time, min
2
3
conversion of nitrobenzene to aniline was increased from 55 to 95% by increase weight percent of deposited metallic silver on surface of holmium hydroxide nanowire from zero to 0.3 wt%, due to decrease band gap and prevent of decrease electron–hole recombination rate. Also, we noticed that weight percent of deposited metallic silver on surface of holmium hydroxide nanowire above 0.3 wt% has no significant effect on photocatalytic conversion of nitrobenzene to aniline. Fig. 8 shows effect of 0.3 wt% Ag–Ho(OH)3 dose on photocatalytic activity of 0.3 wt% Ag–Ho(OH)3 nanowires for conversion of nitrobenzene to aniline. The results reveal that photocatalytic conversion was increased from 76 to 95% by increase dose of 0.3 wt% Ag–Ho(OH)3 photocatalyst from 0.5 to 1.0 g/l, respectively. Reaction time which required for complete conversion of nitrobenzene to aniline was decreased from 150 to 90 min by increase dose of 0.3 wt% Ag–Ho(OH)3 photocatalyst from 1.0 to 2.0 g/l, respectively, due to increase number of available active sites by increase dose of photocatalyst. Also, we can noticed that reaction time which
required for complete conversion of nitrobenzene to aniline was increased from 90 to 150 min by increase dose of 0.3 wt% Ag– Ho(OH)3 photocatalyst from 2.0 to 2.5 g/l, respectively, due to high dose of photocatalyst hinder penetration of light to reach surface of photocatalyst. I compared my photocatalyst with 0.3 wt% Ag–P25 TiO2 photocatalyst. Ag–Ho(OH)3 photocatalyst can reduce 8.13 × 10−4 mol/l nitrobenzene to aniline within 90 min, while 0.3 wt% Ag–P25 TiO2 photocatalyst take about 180 min to reduce the same concentration. The photocatalytic stability of 0.3 wt% Ag–Ho(OH)3 photocatalyst was studied under the following conditions: weight percent of silver is 0.3 wt%; reaction time is 90 min; nitrobenzene concentration is 8.13 × 10−4 mol/l and dose of 0.3 wt% Ag–Ho(OH)3 photocatalyst is 2.0 g/l. Fig. 9 shows recycle and reuse of 0.3 wt% Ag–Ho(OH)3 photocatalyst for photocatalytic conversion of nitrobenzene to aniline. The results reveal that the photocatalytic conversion of nitrobenzene to aniline by 0.3 wt% Ag–Ho(OH)3
90
90
80 70 60 50
0.5 g/l 1.0 g/l 1.5 g/l 2.0 g/l 2.5 g/l
40 30 20 10 0
Conversion of nitrobenzene to aniline, %
100
80 70 60 50 40 30
Ag-Ho(OH)3 in1mM Na2EDTA
20
Ag-Ho(OH)3 in1mM Benzoquinone Ag-Ho(OH)3in1mM TBuOH
10
Ag-Ho(OH)3
0 20
40
60
80
100
5
Fig. 9. Recycle and reuse of 0.3 wt% Ag–Ho(OH)3 photocatalyst for photocatalytic conversion of nitrobenzene to aniline.
100
0
4
No of cycles
Fig. 7. Effect of weight percent of silver on photocatalytic activity of holmium hydroxide nanowires for conversion of nitrobenzene to aniline.
Conversion of nitrobenzene to aniline, %
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120
140
Reaction time, min Fig. 8. Effect of 0.3 wt% Ag–Ho(OH)3 dose on photocatalytic activity of 0.3 wt% Ag– Ho(OH)3 nanowires for conversion of nitrobenzene to aniline.
0
10
20
30
40
50
60
70
80
90
Reaction time, min Fig. 10. Photocatalytic conversion of nitrobenzene to aniline using 0.3 wt% Ag– Ho(OH)3 and 0.3 wt% Ag–Ho(OH)3 in presence of three scavengers agents.
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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0.3 wt % Ag-Ho(OH)3 off
Ho(OH)3
Photocurrent, mA/cm2
on
0
20
40
60
80
100 120 140 160 180 200 220 240
Time(s) Fig. 11. Transient photocurrent responses of Ho(OH)3 and 0.3 wt% Ag–Ho(OH)3 photocatalyst.
photocatalyst was almost constant after reuse five times, thus 0.3 wt% Ag–Ho(OH)3 photocatalyst has photocatalytic stability.
3.3. Radical-trapping experiment Radical-trapping experiments were carried out to measure the main active species in photocatalytic conversion of nitrobenzene to aniline. In radical-trapping experiments, three chemicals were used as scavengers agents such as disodium ethylenediaminetetraacetate (Na2 -EDTA) as a hole scavenger, benzoquinone as a superoxide anion radical scavenger (O2•− ), and tert-butanol as a hydroxyl radical (• OH) scavenger. Fig. 10 shows that the photocatalytic conversion of nitrobenzene to aniline, percentage using 0.3 wt% Ag–Ho(OH)3 and 0.3 wt% Ag–Ho(OH)3 in presence of three scavengers agents. The results reveal that the photocatalytic conversion of nitrobenzene to aniline, percentage was very small with use of 1 mM of Na2 -EDTA, indicating that photogenerated holes in the 0.3 wt% Ag– Ho(OH)3 are the main reactive species which contribute for conversion of nitrobenzene to aniline. However, in the presence of tert-butanol, the photocatalytic conversion of nitrobenzene to aniline, percentage was gradually changed. These can be attributed to reaction of nitrobenzene with partial holes directly, in addition a reaction with water to produce hydroxyl radical. Also, we noticed that, in addition, that the photocatalytic degradation of conversion of nitrobenzene to aniline, percentage was gradually changed in the presence of benzoquinone. Therefore, O2 •− and photogenerated hole are the main responsible species in the photocatalytic conversion of nitrobenzene to aniline.
3.4. Transient photocurrent test Fig. 11 shows transient photocurrent responses of Ho(OH)3 and 0.3 wt% Ag–Ho(OH)3 photocatalyst under visible light irradiation. The results reveal that the photocurrent density of 0.3 wt% Ag– Ho(OH)3 photocatalyst is about three times higher than that of Ho(OH)3 photocatalyst. Therefore, 0.3 wt% Ag–Ho(OH)3 photocatalyst has low recombination rate and high separation efficiency of electron and hole pairs, which is in agreement with PL and UV–vis spectra results.
3.5. Mechanism of photocatalytic reduction of nitrobenzene by 0.3 wt% Ag–Ho(OH)3 photocatalyst When 0.3 wt% Ag–Ho(OH)3 photocatalyst exposed to visible light, electron was moved from valence band to conduction band of Ag–Ho(OH)3, which created reductive conduction electrons and oxidative photogenerated valence holes as shown in Eq. (1). Electrons and holes moved to surface of photocatalysts. Methanol can be captured holes and produce reductive H. and HCHO oxide as shown in Eqs. (2) and (3). Aniline can be produced by reduction of nitrobenzene by H. and photogenerated electron as shown in Eq. (4).
4. Conclusions In summary, holmium hydroxide nanowires were prepared by a hydrothermal method, while silver was deposited on the surface of holmium hydroxide nanowires by a photoassisted deposition method. The silver–holmium hydroxide nanowires photocatalyst was proven to be a promising photocatalyst due to its high photocatalytic efficiency under visible light. By control weight percent of doped deposited metallic silver on holmium hydroxide nanowires the band gap of holmium hydroxide nanowires can be controlled. The optimum conditions for reach 100% conversion of nitrobenzene to aniline was 0.3 wt% Ag–Ho(OH)3 as photocatalyst, 2.0 g/l as dose of photocatalyst as 90 min as reaction time
Acknowledgment This work was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under Grant number (130-564-D1435). The authors, therefore, acknowledge with thanks DSR technical and financial support.
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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References [1] Corma A, Concepcion P, Serna P. A different reaction pathway for the reduction of aromatic nitro compounds on gold catalysts. Angew Chem Int Ed 2007;46:7266–9. [2] Wang J, Yuan Z, Nie R, Hou Z, Zheng X. Hydrogenation of nitrobenzene to aniline over silica gel supported nickel catalysts. Ind Eng Chem Res 2010;49:4664–9. [3] Lee S-P, Chen Y-W. Nitrobenzene hydrogenation on Ni–P, Ni–B and Ni–P–B ultrafine materials. J Mol Catal A Chem 20 0 0;152:213–23. [4] Li H, Zhao Q, Wan Y, Dai W, Qiao M. Self-assembly of mesoporous Ni–B amorphous alloy catalysts. J Catal 2006;244:251–4. [5] Flores SO, Rios-Bernij O, Valenzuela MA, Córdova I, Gómez R, Gutiérrez R. Photocatalytic reduction of nitrobenzene over titanium dioxide: by-product identification and possible pathways. Top Catal 2007;44:507–11. [6] Fuldner S, Pohla P, Bartling H, Dankesreiter S, Stadler R, Gruber M, et al. Selective photocatalytic reductions of nitrobenzene derivatives using PbBiO2 −X and blue light. Green Chem 2011;13:640–3. [7] Ferry JL, Glaze WH. Photocatalytic reduction of nitro organics over illuminated titanium dioxide: role of the TiO2 surface. Langmuir 1998;14:3551–5. [8] Chen S, Zhang H, Yu X, Liu W. Photocatalytic reduction of nitrobenzene by titanium dioxide powder. Chin J Chem 2010;28:21–6 (2010). [9] Mahdavi F, Bruton TC, Li Y. Photoinduced reduction of nitro compounds on semiconductor particles. J Org Chem 1993;58:744–6. [10] Ferry JL, Glaze WH. Photocatalytic reduction of nitroorganics over illuminated titanium dioxide: electron transfer between excited-state TiO2 and nitroaromatics. J Phys Chem B 1998;102:2239–44. [11] Liu G, Li X, Zhao J, Horikoshi S, Hidaka H. Photooxidation mechanism of dye alizarin red in TiO2 dispersions under visible illumination: an experimental and theoretical examination. J Mol Catal A Chem 20 0 0;153:221–9. [12] Dai H-P, Shiu K-K. Voltammetric behavior of alizarin red S adsorbed on electrochemically pretreated glassy carbon electrodes. Electrochim Acta 1998;43:2709–15. [13] Rychnovsky SD, Vaidyanathan R, Beauchamp T, Lin R, Farmer PJ. AM1-SM2 calculations model the redox potential of nitroxyl radicals such as TEMPO. J Org Chem 1999;64:6745–9. [14] Zhang M, Chen C, Ma W, Zhao J. Visible-light-induced aerobic oxidation of alcohols in a coupled photocatalytic system of dye-sensitized TiO2 and TEMPO. Angew Chem Int Ed 2008;120:9876–9. [15] Balasubramanian S. Luminescence behavior of tetraaza macrocylic nickel (II) complexes and non-linear Stern–Volmer quenching. J Lumin 2004;106:69–76. [16] Abdelaal MY, Mohamed RM. Novel Pd/TiO2 nanocomposite prepared by modified sol–gel method for photocatalytic degradation of methylene blue dye under visible light irradiation. J Alloys Compd 2013;576:201–7. [17] Mohamed RM, Aazam ES. H2 production with low CO selectivity from photocatalytic reforming of glucose on Ni/TiO2 -SiO2 . Chin J Catal 2012;33(2):247–53. [18] Mohamed RM. UV-assisted photocatalytic synthesis of TiO2 -reduced graphene oxide with enhanced photocatalytic activity in decomposition of Sarin in gas phase,. Desalin Water Treat 2012;50:147–56. [19] Mohamed RM, McKinney DL, Sigmund WM. Enhanced nanocatalysts. Mater Sci Eng R 2012;73:1–13. [20] Mohamed RM, Aazam ES. Photocatalytic oxidation of carbon monoxide over NiO/SnO2 Nanocomposites under UV irradiation. J Nanotechnol 2012;2012:9 Article ID 794874pages.
[21] Mohamed RM, Aazam ES. Preparation and characterization of platinum doped porous titania nanoparticles for photocatalytic oxidation of carbon monoxide. J Alloys Compd 2011;509:10132–8. [22] Mohamed RM, Mkhalid IA. Characterization and catalytic properties of nano– sized Ag metal catalyst on TiO2 -SiO2 Synthesized by photo-assisted deposition (PAD) and impregnation methods. J Alloys Compd 2010;501:301–6. [23] Mohamed RM, Mkhalid IA. The effect of rare earth dopants on the structure, surface texture and photocatalytic properties of TiO2 -SiO2 prepared by sol-gel method. J Alloys Compd 2010;501:143–7. [24] Mohamed RM, Baeissa ES. Mordenite encapsulated with Pt-TiO2 : characterization and applications for photocatalytic degradation of direct blue dye. J Alloys Compd 2013;558:68–72. [25] Mohamed RM, Baeissa ES. Preparation and characterization of Pd-TiO2 -hydroxyapatite nanoparticles for the photocatalytic degradation of cyanide under visible light. Appl Catal A 2013;464-465:218–24. [26] Niu X, Li H, Liu G. Preparation, characterization and photocatalytic properties of REFeO3 (RE = Sm, Eu, Gd). J Mol Catal A Chem 2005;232:89–93. [27] Mahata P, Aarthi T, Madras G, Natarajan S. Photocatalytic degradation of dyes and organics with nano GdCoO3 . J Phys Chem C 2007;111:1665–74. [28] Li Y, Yao S, Xue L, Yan Y. Sol-gel combustion synthesis of nanocrystalline LaMnO3 powders and photocatalytic properties. J Mater Sci 2009;44:4455–9. [29] Zhang Y, Yang J, Xu J, Gao Q, Hong Z. Controllable synthesis of hexagonal and orthorhombic YFeO3 and their visible-light photocatalytic activities. Mater Lett 2012;81:1–4. [30] Bong B, Li Z, Li Z, Xu X, Song M, Zheng W, et al. Highly efficient LaCoO3 nanofibers catalysts for photocatalytic degradation of rhodamine B. J Am Ceram Soc 2010;93:3587–90. [31] Ding J, Lu X, Shu H, Xie J, Zhang H. Microwave-assisted synthesis of perovskite ReFeO3 (Re: La, Sm, Eu, Gd) photocatalyst. Mat Sci Eng B 2010;171:31–4. [32] Tang P, Chen H, Cao F, Pan G. Magnetically recoverable and visible-light-driven nanocrystalline YFeO3 photocatalysts. Catal Sci Technol 2011;1:1145–8. [33] Maeda K, Wang X, Nishihara Y, Lu D, Antonietti M, Domen K. Photocatalytic activities of graphitic carbon nitride powder for water reduction and oxidation under visible light. J Phys Chem C 2009;113:4940–7. [34] Yan SC, Li ZS, Zou ZG. Photodegradation performance of g-C3 N4 fabricated by directly heating melamine. Langmuir 2009;25:10397–401. [35] Wang Y, Wang X, Antonietti M. Polymeric graphitic carbon nitride as a heterogeneous organocatalyst: from photochemistry to multipurpose catalysis to sustainable chemistry. Angen Chem Int Ed 2012;51:68–89. [36] Su F, Mathew SC, Mohlmann L, Antonietti M, Wang X, Blechert S. Aerobic oxidative coupling of amines by carbon nitride photocatalysis with visible light. Angen Chem Int Ed 2011;50:657–60. [37] Guo Y, Chu S, Yan S, Wang Y, Zou Z. Developing a polymeric semiconductor photocatalyst with visible light response. Chem Commun 2010;46:7325–7. [38] Li ZH, Xie ZP, Zhang YF, Wu L, Wang XX, Fu XZ. Wide band gap p-block metal oxyhydroxide InOOH: a new durable photocatalyst for benzene degradation. J Phys Chem C 2007;111:18348–52. [39] Yan TJ, Wang XX, Long JL, Liu P, Fu XL, Zhang GY, et al. Urea-based hydrothermal growth, optical and photocatalytic properties of single-crystalline In(OH)3 nanocubes. J Colloid Interface Sci 2008;325:425–31. [40] Rao CV, Golder AK. Development of a bio-mediated technique of silver-doping on titania. J Colloid Interface Sci 2016;506:557–65.
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Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene E.S. Baeissa∗ Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
a r t i c l e
i n f o
Article history: Received 19 July 2016 Revised 7 November 2016 Accepted 10 November 2016 Available online xxx Keywords: Holmium hydroxide nanowires Silver depositing Nitrobenzene reduction
a b s t r a c t Holmium hydroxide nanowires were prepared by a hydrothermal method, while silver was deposited on the surface of holmium hydroxide nanowires by a photoassisted deposition method. Holmium hydroxide nanowires and silver deposited holmium hydroxide nanowires were characterized by different techniques such as XRD, PL, XPS, UV–vis, TEM and BET surface area measurements. The photocatalytic performance of holmium hydroxide nanowires and silver deposited holmium hydroxide nanowires was measured by studied the visible light reduction of nitrobenzene to aniline. The results reveal that the form of deposited silver is a metallic silver and it well dispersed on the surface of holmium hydroxide nanowires. Band gap of holmium hydroxide nanowires was decreased from 2.92 to 2.64 eV by depositing of silver. Weight percent of deposited silver plays important role in control band gap and photocatalytic activity of holmium hydroxide nanowires. 0.3 wt% silver deposited holmium hydroxide has the lowest band gap and the highest photocatalytic activity for reduction of nitrobenzene. © 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
1. Introduction One of the most important chemicals and intermediates in the production of dyes, pigments, pesticides and pharmaceuticals is aniline [1,2]. Aniline was prepared by hydrogenation of nitrobenzene. In hydrogenation process, the most common catalysts are noble metals catalysts such as Au, Pd and Pt and transitions metals catalysts such as Ni and Cu [1–3], but, the hydrogenation process needs high hydrogen pressure, high temperature and high reaction time [3,4]. The preparation of aniline was done at room temperature and atmospheric pressure by using photocatalytic process [5–15]. The most famous photocatalyst it titanium dioxide due to its stability, and high photocatalytic activity. But, TiO2 absorb in UV region and percent of UV light in solar spectrum is about 3–5%, which hinder using of TiO2 in visible region [16]. Many methods were used to shift absorption of TiO2 from UV to visible region such as metal and non metal doping and coupling with another semiconductor materials [17–25]. Recently, new photocatalysts which have narrow band gaps were prepared. Perovskites photocatalysts have narrow band gap [26–32]. The drawbacks of perovskites photocatalysts are high electron–hole recombination rate and low surface area. Also, researchers prepare polymer-like semiconductor materials that are considered to be an efficient photocatalyst using visible light for environmental purification and ∗
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hydrogen production [33–37]. Polymer-like semiconductor materials have many properties, such as high stability, low cost and a controllable surface. Therefore, a polymer-like semiconductor material can be considered as a new material for solar energy and environmental applications. There are three drawbacks for using it as a commercial photocatalyst: a small surface area, high recombination rate of electron–hole pairs and a lack of absorption above 460 nm. Recently, hydroxide-based photocatalysts such as In(OH)3 and InOOH have high photocatalytic activity for photodegradation of benzene [38,39]. To best of our knowledge, there is no reported about preparation of holmium hydroxide or silver doped holmium hydroxide nanowires. Also, there is no published paper about synthesis of aniline by hydroxide photocatalyst. Thus, this work aims to preparation of holmium hydroxide and silver deposited holmium hydroxide nanowires for preparation of aniline from visible light photocatalytic reduction of nitrobenzene. 2. Experimental 2.1. Synthesis of photocatalyst Holmium hydroxide nanowires were prepared by a hydrothermal method. In a typical procedure, 30 ml of ethylene glycol, 98.8% was mixed with 20 ml of isopropanol, 99% and 5 mmol of holmium nitrate pentahydrate was added dropwise to them and resulting mixture was stirred for 30 min at room temperature. The obtained sol was heated at 80 °C to produce gel and the gel was dried for
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Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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Jasco, Japan) in air at room temperature to detect absorption over the range 20 0–80 0 nm. And photoluminescence emission spectra (PL) were obtained with a Shimadzu RF-5301 fluorescence spectrophotometer.
0.40 wt % Ag-Ho(OH)3
2.3. Photocatalytic performance
0.10 wt % Ag-Ho(OH)3
Ho(OH)3
201
110 101
15.6 16.0 16.4 2-theta, degree
16.8
211
15.2
100
Intensity, a.u.
Intensity, a.u.
0.30 wt % Ag-Ho(OH)3 0.20 wt % Ag-Ho(OH)3
0.40 wt % Ag-Ho(OH)3 0.30 wt % Ag-Ho(OH)3 0.20 wt % Ag-Ho(OH)3 0.10 wt % Ag-Ho(OH)3 Ho(OH)3
10
15
20
25
30
35
40
45
50
55
60
65
70
2-theta, degree Fig. 1. XRD of holmium hydroxide and silver doped holmium hydroxide nanowires.
24 h at 100 °C. The obtained powders were dispersed in 80 ml of distilled water and heated at 180 °C for 24 h using an autoclave. After cooling temperature of autoclave, the obtained powders were washed many times by distilled water and absolute ethanol, then dried for 24 h at 80 °C. Different weight percents of silver (0.1, 0.2. 0.3 and 0.4 wt% Ag) were deposited on the surface of holmium hydroxide nanowires by a photoassisted deposition method. In a typical procedure, metallic silver was deposited on surface of holmium hydroxide nanowires using strong UV lamp (150 W) and in presence of silver nitrate solution. 2.2. Characterization techniques Nanostructure morphology and sample dimensions were measured using JEOL-JEM-1230 transmission electron microscopy (TEM). Samples were suspended in ethanol and ultra-sonicated for 30 m. A small amount was then coated with carbon, dried on a copper grid, and loaded into the TEM. Also, N2 -adsorption measurements were taken on treated samples (2 h under vacuum at 100 °C) with a Nova 2000 series Chromatech apparatus at 77 K to calculate surface area. Crystalline phase was determined by powder X-ray diffraction (XRD) using Bruker axis D8 with Cu Kα ra˚ at room temperature. X-ray photoelectron diation (λ = 1.540 A) spectroscopy (XPS) measurements were performed on a Thermo Scientific K-ALPHA spectrometer. Band gap performance was determined by ultra violet–visible diffuse reflectance spectra (UV– vis-DRS), measured using a UV–vis-NIR spectrophotometer (V-570,
The photocatalytic apparatus consists of two parts: an annular quartz tube and a sealed quartz reactor. A 500-W Xenon lamp (Institute of Electric Light Source, Beijing) with a maximum emission of about 470 nm is the visible light source. A cutoff filter (λ > 420 nm) controlled the light’s wavelength. The lamp was in an empty chamber of the annular tube, and running water passed through the tube’s inner thimble. Continuous cooling kept the reaction solution at approximately 30 °C. The sealed quartz reactor has a diameter of 8.3 cm and is below the lamp. For each photochemical reaction, we ultrasonically dispersed a sample of the photocatalyst (50 mg) in 10 ml nitrobenzene–CH3 OH solution (1/99, v/v). The initial concentration of nitrobenzene (NB) was 8.13 × 10−4 mol/l. The distance between the light source and the surface of the reaction solution was 11 cm. Nitrogen passed through the solution for 0.5 h before illumination to remove dissolved oxygen in the solution, freeing photoinduced electrons to reduce NB. After 2.5 h of illumination, we took the samples from the reaction suspension, centrifuged them at 70 0 0 rpm for 20 min and finally filtered them through a 0.2-μm millipore filter to remove any residual particles. The filtrate was then analyzed using a gas chromatography Agilent GC 7890A model: G3440A Gas Chromatography using 19091J-413 capillary column (30 m × 0.32 μm × 0.25 μm). 2.4. Radical-trapping experiment In order to identify the major active species in the reduction of nitrobenzene, radical-trapping experiments were carried out using three chemicals, disodium ethylenediaminetetraacetate (Na2 EDTA, a hole scavenger), tert-butanol (an • OH radical scavenger) and benzoquinone (a superoxide anion radical scavenger). The conditions radical-trapping experiments are the same as in photocatalytic test except we add one of chemicals to reaction mixture. 2.5. Transient photocurrent tests Indium-tin-oxide slices (ITO) were boiled in a 2 M NaOH solution and sonicated successively in acetone, alcohol, and deionized water for 15 min each. Then, the ITO electrodes were rinsed with deionized water and dried at room temperature. The solution with Ho(OH)3 was dropped onto the pretreated ITO (1.0 cm × 1.0 cm) and then dried at room temperature. The photocurrent intensity recorded using electrochemical workstation, Zahner Zennium, Germany. The photocurrent measurements were carried out in 0.1 M Na2 SO4 solution. The applied potential was 0.2 V and a 500 WXe lamp equipped with a monochromator was used as the irradiation source to produce the monochromatic light at 420 nm.
Table 1 Texture parameters of Ho(OH)3 and Ag–Ho(OH)3 nanowires. Sample
SBET (m2 /g)
St (m2 /g)
Smicro (cm2 /g)
Sext (cm2 /g)
Vp (cm3 /g)
Vmicro (cm3 /g)
Vmeso (cm3 /g)
˚ r (A)
Ho(OH)3 0.10 wt% Ag–Ho(OH)3 0.20 wt% Ag–Ho(OH)3 0.30 wt% Ag–Ho(OH)3 0.40 wt% Ag–Ho(OH)3
40.00 37.00 35.00 33.00 31.00
41.00 38.00 35.00 34.00 31.00
27.00 26.00 25.00 24.00 23.00
13.00 11.00 10.00 09.00 08.00
0.200 0.190 0.160 0.155 0.130
0.150 0.150 0.130 0.120 0.110
0.050 0.040 0.030 0.025 0.020
30.00 35.00 40.00 45.00 50.00
Note: (SBET ) BET-surface area (St ) surface area derived from Vl − t plots. (Smic ) surface area of micropores (Sext ) external surface area. (Vp ) total pore volume (Vmic ) pore volume of micropores. (Vmes ) pore volume of mesopores (r− ) mean pore radius.
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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3
A
Intensity, a.u.
Ho 3d 5/2
166
164
162
160
158
156
Binding energy, eV
B
C Ag 3d
528
Intensity, a.u.
Intensity, a.u.
O 1s
530
532
534
536
538
540
380 378 376 374 372 370 368 366 364 362 360 Binding energy, eV
Binding energy (eV)
Fig. 2. XPS spectres of Ho3d (A); O 1s (B) and Ag 4d (C) for 0.30 wt% Ag–Ho(OH)3 sample.
3. Results and discussions 3.1. Characterizations of photocatalysts Fig. 1 shows XRD of holmium hydroxide and silver deposited holmium hydroxide nanowires. The results reveal that holmium hydroxide and silver deposited holmium hydroxide samples are composed from holmium hydroxide and there are no peaks for silver or silver oxide, due to the weight percent of silver is low detection limit of XRD or the high dispersion of silver on surface of holmium hydroxide. Also, we noticed that peaks intensity of holmium hydroxide phase was decreased and broad by addition of silver. There is a slight right shift in the [100] peak of Ho(OH)3 for the Ag–Ho(OH)3 samples, which suggests that silver has been doped into the Ho(OH)3 lattice. Fig. 2 shows XPS spectres of Ho3d (A); O 1s (B) and Ag4d (C) for 0.30 wt% Ag–Ho(OH)3 sample. The results reveal that the peak at 163.1 eV represents binding energy of Ho3d5/2 which confirm the presence of Ho3+ ion as shown in Fig. 2A. The peak at 532.1 eV represents binding energy of O 1s, which confirm the presence of O ion bonded to H as shown in Fig. 2B. XPS of Ho and O species confirm the formation of Ho(OH)3 , which was agree with XRD results. Also, we noticed that the two peaks at 368.2 and 374.2 eV represent the binding energy of Ag3d5/2 and Ag3d3 /2 , respectively, which confirm the presence of metallic silver as shown in Fig. 2C.
Table 2 Band gap energy of Ho(OH)3 and Ag–Ho(OH)3 nanowires. Sample
Band gap energy (eV)
Ho(OH)3 0.10 wt% Ag–Ho(OH)3 0.20 wt% Ag–Ho(OH)3 0.30 wt% Ag–Ho(OH)3 0.40 wt% Ag–Ho(OH)3
2.90 2.80 2.70 2.63 2.61
Fig. 3 shows TEM images of holmium hydroxide and silver deposited holmium hydroxide nanowires, where (A) Ho(OH)3 ; (B) 0.1 wt% Ag–Ho(OH)3 ; (C) 0.2 wt% Ag–Ho(OH)3 ; (D) 0.3 wt% Ag– Ho(OH)3 and (E) 0.4 wt% Ag–Ho(OH)3 . The results reveal that shape of holmium hydroxide and silver deposited holmium hydroxide samples is nanowires and metallic silver was deposited as dots. Also, we noticed that the dispersion of metallic silver depends on weight percent of deposited silver. 0.3 wt% Ag–Ho(OH)3 sample has the best dispersion of silver on surface of holmium hydroxide. Table 1 shows texture parameters of holmium hydroxide and silver deposited holmium hydroxide nanowires. The values of specific surface area are 40, 37, 35, 33 and 31 m2 /g, for Ho(OH)3 , 0.1 wt% Ag–Ho(OH)3 , 0.2 wt% Ag–Ho(OH)3 , 0.3 wt% Ag–Ho(OH)3 and 0.4 wt% Ag–Ho(OH)3 , respectively. Thus the addition of silver leads to decrease specific surface area of holmium hydroxide and
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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A
B
C
D
E
Fig. 3. TEM images of holmium hydroxide and silver doped holmium hydroxide nanowires, where (A) Ho(OH)3 ; (B) 0.1 wt% Ag–Ho(OH)3 ; (C) 0.2 wt% Ag–Ho(OH)3 ; (D) 0.3 wt% Ag–Ho(OH)3 and (E) 0.4 wt% Ag–Ho(OH)3 .
Ho(OH)3
0.40 wt % Ag-Ho(OH)3
0.10 wt % Ag-Ho(OH)3
0.30 wt % Ag-Ho(OH)3
0.20 wt % Ag-Ho(OH)3
0.20 wt % Ag-Ho(OH)3
0.30 wt % Ag-Ho(OH)3
Reflectance, %
0.10 wt % Ag-Ho(OH)3
0.40 wt % Ag-Ho(OH)3
200
300
Intensity (a. u.)
Ho(OH)3
400
500
600
700
800
Wavelength, nm Fig. 4. UV–vis absorption spectra of holmium hydroxide and silver doped holmium hydroxide nanowires.
these can be attributed to blocking of some pores of holmium hydroxide by depositing of silver as shown in Table 1. Also, we noticed that the values of SBET are very close to values of St , which confirm the presence of mesopores materials.
440
460
480
500
520
540
560
580
600
620
Wavelength (nm) Fig. 5. PL spectra of holmium hydroxide and silver doped holmium hydroxide nanowires.
Fig. 4 shows UV–vis-DRS of holmium hydroxide and silver deposited holmium hydroxide nanowires. The results reveal that holmium hydroxide and silver deposited holmium
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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Fig. 6. Chromatograms of different samples, where A at initial of the reactions; B at medium time and C at finial of the reaction.
hydroxide nanowires absorb in visible region. The absorption edge of holmium hydroxide was increased from 428 to 471 nm by increased weight percent of doped metallic silver from zero to 0.3 wt% and increase weight percent of deposited metallic silver above 0.3 wt% has no significant effect on absorption edges of holmium hydroxide. Therefore, weight percent of deposited metallic silver plays important role in control absorption edge of holmium hydroxide nanowire. The band gap energies of holmium hydroxide and silver deposited holmium hydroxide nanowires were calculated from UV–vis-DRS and values were tabulated in Table 2. The results reveal that the band gap values are 2.90, 2.80, 2.70, 2.63 and 2.61 eV for Ho(OH)3 , 0.1 wt% Ag–Ho(OH)3 , 0.2 wt% Ag–Ho(OH)3 , 0.3 wt% Ag–Ho(OH)3 and 0.4 wt% Ag–Ho(OH)3 , respectively. The reason for the decrease in Eg could be the localized surface plasmon resonance (SPR) effect that was attributed by the Ag NPs [40]. Therefore, the actual Eg of holmium hydroxide was the same, but the SPR added visible light absorbance as results published for Ag/TiO2 [40]. The PL spectra were detected for the different samples which were exited at 265 nm at room temperature. Fig. 5 shows PL spectra of holmium hydroxide and silver deposited holmium hydroxide
nanowires. The results reveal that the PL peak intensity was decreased by increase weight percent of doped metallic silver from zero to 0.3 wt% and increase weight percent of deposited metallic silver above 0.3 wt% has no significant effect on PL peak intensity. Therefore, weight percent of doped metallic silver plays important role in control electron–hole recombination rate of holmium hydroxide nanowire. 3.2. Photocatalytic activities We studied the conversion of nitrobenzene into aniline before studied the photocatalysis process under different conditions such as in presence of light and in absence of photocatalyst, in presence of photocatalyst and in absence of light. Gas chromatogram results reveal that nitrosobenzene and aniline are main products as shown in Fig. 6A–C. Also, we noticed that in both cases, there is detection of aniline or nitrosobenzene, which means the conversion of nitrobenzene cannot carried out by UV light only or photocatalyst only. Fig. 7 shows effect of weight percent of silver on photocatalytic activity of holmium hydroxide nanowires for conversion of nitrobenzene to aniline. The results reveal that the photocatalytic
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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No catalyst NO light Ho(OH)3
90
100
Conversion of nitrobenzene to aniline, %
Conversion of nitrobenzene to aniline, %
100
0.1 wt % Ag-Ho(OH)3 0.2 wt % Ag-Ho(OH)3
80
0.3 wt % Ag-Ho(OH)3 0.4 wt % Ag-Ho(OH)3
70 60 50 40 30 20 10 0 0
15
30
45
60
75
90
105
120
135
90 80 70 60 50 40 30 20 10 0
150
1
Irradiation time, min
2
3
conversion of nitrobenzene to aniline was increased from 55 to 95% by increase weight percent of deposited metallic silver on surface of holmium hydroxide nanowire from zero to 0.3 wt%, due to decrease band gap and prevent of decrease electron–hole recombination rate. Also, we noticed that weight percent of deposited metallic silver on surface of holmium hydroxide nanowire above 0.3 wt% has no significant effect on photocatalytic conversion of nitrobenzene to aniline. Fig. 8 shows effect of 0.3 wt% Ag–Ho(OH)3 dose on photocatalytic activity of 0.3 wt% Ag–Ho(OH)3 nanowires for conversion of nitrobenzene to aniline. The results reveal that photocatalytic conversion was increased from 76 to 95% by increase dose of 0.3 wt% Ag–Ho(OH)3 photocatalyst from 0.5 to 1.0 g/l, respectively. Reaction time which required for complete conversion of nitrobenzene to aniline was decreased from 150 to 90 min by increase dose of 0.3 wt% Ag–Ho(OH)3 photocatalyst from 1.0 to 2.0 g/l, respectively, due to increase number of available active sites by increase dose of photocatalyst. Also, we can noticed that reaction time which
required for complete conversion of nitrobenzene to aniline was increased from 90 to 150 min by increase dose of 0.3 wt% Ag– Ho(OH)3 photocatalyst from 2.0 to 2.5 g/l, respectively, due to high dose of photocatalyst hinder penetration of light to reach surface of photocatalyst. I compared my photocatalyst with 0.3 wt% Ag–P25 TiO2 photocatalyst. Ag–Ho(OH)3 photocatalyst can reduce 8.13 × 10−4 mol/l nitrobenzene to aniline within 90 min, while 0.3 wt% Ag–P25 TiO2 photocatalyst take about 180 min to reduce the same concentration. The photocatalytic stability of 0.3 wt% Ag–Ho(OH)3 photocatalyst was studied under the following conditions: weight percent of silver is 0.3 wt%; reaction time is 90 min; nitrobenzene concentration is 8.13 × 10−4 mol/l and dose of 0.3 wt% Ag–Ho(OH)3 photocatalyst is 2.0 g/l. Fig. 9 shows recycle and reuse of 0.3 wt% Ag–Ho(OH)3 photocatalyst for photocatalytic conversion of nitrobenzene to aniline. The results reveal that the photocatalytic conversion of nitrobenzene to aniline by 0.3 wt% Ag–Ho(OH)3
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Fig. 7. Effect of weight percent of silver on photocatalytic activity of holmium hydroxide nanowires for conversion of nitrobenzene to aniline.
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Reaction time, min Fig. 8. Effect of 0.3 wt% Ag–Ho(OH)3 dose on photocatalytic activity of 0.3 wt% Ag– Ho(OH)3 nanowires for conversion of nitrobenzene to aniline.
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Reaction time, min Fig. 10. Photocatalytic conversion of nitrobenzene to aniline using 0.3 wt% Ag– Ho(OH)3 and 0.3 wt% Ag–Ho(OH)3 in presence of three scavengers agents.
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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photocatalyst was almost constant after reuse five times, thus 0.3 wt% Ag–Ho(OH)3 photocatalyst has photocatalytic stability.
3.3. Radical-trapping experiment Radical-trapping experiments were carried out to measure the main active species in photocatalytic conversion of nitrobenzene to aniline. In radical-trapping experiments, three chemicals were used as scavengers agents such as disodium ethylenediaminetetraacetate (Na2 -EDTA) as a hole scavenger, benzoquinone as a superoxide anion radical scavenger (O2•− ), and tert-butanol as a hydroxyl radical (• OH) scavenger. Fig. 10 shows that the photocatalytic conversion of nitrobenzene to aniline, percentage using 0.3 wt% Ag–Ho(OH)3 and 0.3 wt% Ag–Ho(OH)3 in presence of three scavengers agents. The results reveal that the photocatalytic conversion of nitrobenzene to aniline, percentage was very small with use of 1 mM of Na2 -EDTA, indicating that photogenerated holes in the 0.3 wt% Ag– Ho(OH)3 are the main reactive species which contribute for conversion of nitrobenzene to aniline. However, in the presence of tert-butanol, the photocatalytic conversion of nitrobenzene to aniline, percentage was gradually changed. These can be attributed to reaction of nitrobenzene with partial holes directly, in addition a reaction with water to produce hydroxyl radical. Also, we noticed that, in addition, that the photocatalytic degradation of conversion of nitrobenzene to aniline, percentage was gradually changed in the presence of benzoquinone. Therefore, O2 •− and photogenerated hole are the main responsible species in the photocatalytic conversion of nitrobenzene to aniline.
3.4. Transient photocurrent test Fig. 11 shows transient photocurrent responses of Ho(OH)3 and 0.3 wt% Ag–Ho(OH)3 photocatalyst under visible light irradiation. The results reveal that the photocurrent density of 0.3 wt% Ag– Ho(OH)3 photocatalyst is about three times higher than that of Ho(OH)3 photocatalyst. Therefore, 0.3 wt% Ag–Ho(OH)3 photocatalyst has low recombination rate and high separation efficiency of electron and hole pairs, which is in agreement with PL and UV–vis spectra results.
3.5. Mechanism of photocatalytic reduction of nitrobenzene by 0.3 wt% Ag–Ho(OH)3 photocatalyst When 0.3 wt% Ag–Ho(OH)3 photocatalyst exposed to visible light, electron was moved from valence band to conduction band of Ag–Ho(OH)3, which created reductive conduction electrons and oxidative photogenerated valence holes as shown in Eq. (1). Electrons and holes moved to surface of photocatalysts. Methanol can be captured holes and produce reductive H. and HCHO oxide as shown in Eqs. (2) and (3). Aniline can be produced by reduction of nitrobenzene by H. and photogenerated electron as shown in Eq. (4).
4. Conclusions In summary, holmium hydroxide nanowires were prepared by a hydrothermal method, while silver was deposited on the surface of holmium hydroxide nanowires by a photoassisted deposition method. The silver–holmium hydroxide nanowires photocatalyst was proven to be a promising photocatalyst due to its high photocatalytic efficiency under visible light. By control weight percent of doped deposited metallic silver on holmium hydroxide nanowires the band gap of holmium hydroxide nanowires can be controlled. The optimum conditions for reach 100% conversion of nitrobenzene to aniline was 0.3 wt% Ag–Ho(OH)3 as photocatalyst, 2.0 g/l as dose of photocatalyst as 90 min as reaction time
Acknowledgment This work was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under Grant number (130-564-D1435). The authors, therefore, acknowledge with thanks DSR technical and financial support.
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017
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References [1] Corma A, Concepcion P, Serna P. A different reaction pathway for the reduction of aromatic nitro compounds on gold catalysts. Angew Chem Int Ed 2007;46:7266–9. [2] Wang J, Yuan Z, Nie R, Hou Z, Zheng X. Hydrogenation of nitrobenzene to aniline over silica gel supported nickel catalysts. Ind Eng Chem Res 2010;49:4664–9. [3] Lee S-P, Chen Y-W. Nitrobenzene hydrogenation on Ni–P, Ni–B and Ni–P–B ultrafine materials. J Mol Catal A Chem 20 0 0;152:213–23. [4] Li H, Zhao Q, Wan Y, Dai W, Qiao M. Self-assembly of mesoporous Ni–B amorphous alloy catalysts. J Catal 2006;244:251–4. [5] Flores SO, Rios-Bernij O, Valenzuela MA, Córdova I, Gómez R, Gutiérrez R. Photocatalytic reduction of nitrobenzene over titanium dioxide: by-product identification and possible pathways. Top Catal 2007;44:507–11. [6] Fuldner S, Pohla P, Bartling H, Dankesreiter S, Stadler R, Gruber M, et al. Selective photocatalytic reductions of nitrobenzene derivatives using PbBiO2 −X and blue light. Green Chem 2011;13:640–3. [7] Ferry JL, Glaze WH. Photocatalytic reduction of nitro organics over illuminated titanium dioxide: role of the TiO2 surface. Langmuir 1998;14:3551–5. [8] Chen S, Zhang H, Yu X, Liu W. Photocatalytic reduction of nitrobenzene by titanium dioxide powder. Chin J Chem 2010;28:21–6 (2010). [9] Mahdavi F, Bruton TC, Li Y. Photoinduced reduction of nitro compounds on semiconductor particles. J Org Chem 1993;58:744–6. [10] Ferry JL, Glaze WH. Photocatalytic reduction of nitroorganics over illuminated titanium dioxide: electron transfer between excited-state TiO2 and nitroaromatics. J Phys Chem B 1998;102:2239–44. [11] Liu G, Li X, Zhao J, Horikoshi S, Hidaka H. Photooxidation mechanism of dye alizarin red in TiO2 dispersions under visible illumination: an experimental and theoretical examination. J Mol Catal A Chem 20 0 0;153:221–9. [12] Dai H-P, Shiu K-K. Voltammetric behavior of alizarin red S adsorbed on electrochemically pretreated glassy carbon electrodes. Electrochim Acta 1998;43:2709–15. [13] Rychnovsky SD, Vaidyanathan R, Beauchamp T, Lin R, Farmer PJ. AM1-SM2 calculations model the redox potential of nitroxyl radicals such as TEMPO. J Org Chem 1999;64:6745–9. [14] Zhang M, Chen C, Ma W, Zhao J. Visible-light-induced aerobic oxidation of alcohols in a coupled photocatalytic system of dye-sensitized TiO2 and TEMPO. Angew Chem Int Ed 2008;120:9876–9. [15] Balasubramanian S. Luminescence behavior of tetraaza macrocylic nickel (II) complexes and non-linear Stern–Volmer quenching. J Lumin 2004;106:69–76. [16] Abdelaal MY, Mohamed RM. Novel Pd/TiO2 nanocomposite prepared by modified sol–gel method for photocatalytic degradation of methylene blue dye under visible light irradiation. J Alloys Compd 2013;576:201–7. [17] Mohamed RM, Aazam ES. H2 production with low CO selectivity from photocatalytic reforming of glucose on Ni/TiO2 -SiO2 . Chin J Catal 2012;33(2):247–53. [18] Mohamed RM. UV-assisted photocatalytic synthesis of TiO2 -reduced graphene oxide with enhanced photocatalytic activity in decomposition of Sarin in gas phase,. Desalin Water Treat 2012;50:147–56. [19] Mohamed RM, McKinney DL, Sigmund WM. Enhanced nanocatalysts. Mater Sci Eng R 2012;73:1–13. [20] Mohamed RM, Aazam ES. Photocatalytic oxidation of carbon monoxide over NiO/SnO2 Nanocomposites under UV irradiation. J Nanotechnol 2012;2012:9 Article ID 794874pages.
[21] Mohamed RM, Aazam ES. Preparation and characterization of platinum doped porous titania nanoparticles for photocatalytic oxidation of carbon monoxide. J Alloys Compd 2011;509:10132–8. [22] Mohamed RM, Mkhalid IA. Characterization and catalytic properties of nano– sized Ag metal catalyst on TiO2 -SiO2 Synthesized by photo-assisted deposition (PAD) and impregnation methods. J Alloys Compd 2010;501:301–6. [23] Mohamed RM, Mkhalid IA. The effect of rare earth dopants on the structure, surface texture and photocatalytic properties of TiO2 -SiO2 prepared by sol-gel method. J Alloys Compd 2010;501:143–7. [24] Mohamed RM, Baeissa ES. Mordenite encapsulated with Pt-TiO2 : characterization and applications for photocatalytic degradation of direct blue dye. J Alloys Compd 2013;558:68–72. [25] Mohamed RM, Baeissa ES. Preparation and characterization of Pd-TiO2 -hydroxyapatite nanoparticles for the photocatalytic degradation of cyanide under visible light. Appl Catal A 2013;464-465:218–24. [26] Niu X, Li H, Liu G. Preparation, characterization and photocatalytic properties of REFeO3 (RE = Sm, Eu, Gd). J Mol Catal A Chem 2005;232:89–93. [27] Mahata P, Aarthi T, Madras G, Natarajan S. Photocatalytic degradation of dyes and organics with nano GdCoO3 . J Phys Chem C 2007;111:1665–74. [28] Li Y, Yao S, Xue L, Yan Y. Sol-gel combustion synthesis of nanocrystalline LaMnO3 powders and photocatalytic properties. J Mater Sci 2009;44:4455–9. [29] Zhang Y, Yang J, Xu J, Gao Q, Hong Z. Controllable synthesis of hexagonal and orthorhombic YFeO3 and their visible-light photocatalytic activities. Mater Lett 2012;81:1–4. [30] Bong B, Li Z, Li Z, Xu X, Song M, Zheng W, et al. Highly efficient LaCoO3 nanofibers catalysts for photocatalytic degradation of rhodamine B. J Am Ceram Soc 2010;93:3587–90. [31] Ding J, Lu X, Shu H, Xie J, Zhang H. Microwave-assisted synthesis of perovskite ReFeO3 (Re: La, Sm, Eu, Gd) photocatalyst. Mat Sci Eng B 2010;171:31–4. [32] Tang P, Chen H, Cao F, Pan G. Magnetically recoverable and visible-light-driven nanocrystalline YFeO3 photocatalysts. Catal Sci Technol 2011;1:1145–8. [33] Maeda K, Wang X, Nishihara Y, Lu D, Antonietti M, Domen K. Photocatalytic activities of graphitic carbon nitride powder for water reduction and oxidation under visible light. J Phys Chem C 2009;113:4940–7. [34] Yan SC, Li ZS, Zou ZG. Photodegradation performance of g-C3 N4 fabricated by directly heating melamine. Langmuir 2009;25:10397–401. [35] Wang Y, Wang X, Antonietti M. Polymeric graphitic carbon nitride as a heterogeneous organocatalyst: from photochemistry to multipurpose catalysis to sustainable chemistry. Angen Chem Int Ed 2012;51:68–89. [36] Su F, Mathew SC, Mohlmann L, Antonietti M, Wang X, Blechert S. Aerobic oxidative coupling of amines by carbon nitride photocatalysis with visible light. Angen Chem Int Ed 2011;50:657–60. [37] Guo Y, Chu S, Yan S, Wang Y, Zou Z. Developing a polymeric semiconductor photocatalyst with visible light response. Chem Commun 2010;46:7325–7. [38] Li ZH, Xie ZP, Zhang YF, Wu L, Wang XX, Fu XZ. Wide band gap p-block metal oxyhydroxide InOOH: a new durable photocatalyst for benzene degradation. J Phys Chem C 2007;111:18348–52. [39] Yan TJ, Wang XX, Long JL, Liu P, Fu XL, Zhang GY, et al. Urea-based hydrothermal growth, optical and photocatalytic properties of single-crystalline In(OH)3 nanocubes. J Colloid Interface Sci 2008;325:425–31. [40] Rao CV, Golder AK. Development of a bio-mediated technique of silver-doping on titania. J Colloid Interface Sci 2016;506:557–65.
Please cite this article as: E.S. Baeissa, Silver deposited holmium hydroxide nanowires for synthesis of aniline from visible light reduction of nitrobenzene, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.11.017