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Photocatalytic Property of Nanostructured S Doped TiO2 Films Prepared by the Micro Plasma Method
Rare Metal Materials and Engineering Volume 44, Issue 7, July 2015 Online English edition of the Chinese language journal Cite this article as: Rare Metal Materials and Engineering, 2015, 44(7): 1629-1632
ARTICLE
Photocatalytic Property of Nanostructured S Doped TiO2 Films Prepared by the Micro Plasma Method Yu Zhongchen1, 1
Wang Song1,
Han Lu2,
Li Zhuan1,
Niu Yuanlin 1
Northeastern Petroleum University, Daqing 163318, China；2 Hebei Normal University of Science and Technology, Qinghuangdao 066004,
China
Abstract: Mesoporous titanium dioxide thin films were prepared on titanium plates within a short time by a micro-plasma oxidation method. The films were used to degrade Rhodamine B, a textile industry pollutant. To increase the photocatalytic activity, different concentrations of CH4N2S were added into an H2SO4 electrolyte solution to make the doped S enter the films. X-ray diffraction and scanning electron microscopy were used to characterize the surface morphology, the composition, the crystal structure and microstructure of the modified films. Results show that the modified films are porous with different sizes of pores. The CH 4N2S concentration in the electrolyte solution has a greater influence on the micropore density and the pore size of the film. S-doping can increase micropore density and specific surface area of the film, somewhat alters its crystal lattice parameter, but affects its crystal structure only a little. The photo-catalytic activity will be enhanced effectively by S-doping, for example, when the CH4N2S concentration in the electrolyte solution is 6.0 g/L, the photocatalytic degradation of Rhodamine B with the initial concentration of 10 mg/L by TiO2 thin films reaches 98% within 120 min, showing the maximum photocatalytic degradation of TiO 2 films. Key words: TiO2 thin films; photocatalytic activity; S-doping
TiO2 is widely used as a photocatalyst because of its photochemical stability, nontoxicity, and low cost[1,2]. Several researchers doped TiO2 films with non-metal impurities to improve their photocatalytic performance[3–5]. Asahi et al. (2001) reported the doping of TiO2 with S ions[6]. S ion is difficult to be introduced into the crystal lattice of TiO2 because of its large diameter. Ohno demonstrated that S4+ can replace Ti4+ in the TiO2 crystal lattice to expand the absorption wavelength range and to improve the photocatalytic efficiency[7,8]. Nevertheless, the crystal structure of S-doped TiO2 has not been defined. TiO2 films could be prepared via micro-plasma oxidation (MPO), consisting of numerous simultaneous and uniform plasma discharges on a metal surface[9–11]. Homogenous films with good adherence to the substrate could be produced within a short time[12]. The dopant added to the electrolyte solution was readily incorporated into the film. MPO exhibits many advantages, such as fast reaction, simple
operation, and easy doping of ions into the electrolyte. The prepared film is directly connected with the electrolyte. Thus, ions can be easily doped into the film[13]. Different concentrations of CH4N2S were added into the electrolyte solution during MPO. In the present experiment S-doped films were prepared on titanium plates by MPO process using CH4N2S as dopant to evaluate the photocatalytic activity, crystal structure and surface morphology of S-TiO2 films so as to provide technical reference for further improvement of the photocatalytic property.
1
Experiment
Pure and S-doped thin TiO2 films were grown on a titanium substrate using the MPO method. The experiment reaction unit of MPO is shown in Fig.1. Thin TiO2 films were prepared as follows. A titanium sheet washed in a HF-HNO3 (1:1, V/V) aqueous solution was selected as an anode. The reaction area was 20 mm×10 mm. A copper sheet was used as a cathode. A
Received date: July 25, 2014 Foundation item: Scientific Research Foundation of the Educational Commission of Heilongjiang Province of China (12541066) Corresponding author: Yu Zhongchen, Master, Associate Professor, School of Civil Engineering & Architecture, Northeastern Petroleum University, Daqing 163318, P. R. China, Tel: 0086-459-6503117, E-mail: [email protected] Copyright © 2015, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.
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2
Removal Efficiency/%
TS2
TS1
TS3
TS4
80 60 40 20 0
15
30
45 b
100 80 Pure TiO2 TS1 TS2 TS3 TS4
60 40 20 0 0
Fig.2
a
15
30
45 60 75 Time/min
90 105 120
Photocatalytic degradation of Rhodamine B by TiO2 thin films produced at different conditions
Results and Discussion
2.1 Results of photo degradation of Rhodamine B The degradation of Rhodamine B by the thin TiO2 films was determined (Fig.2a and 2b). The results show that the rapid removal rate of Rhodamine B is before 45 min, and the removal efficiencies of all TiO2 films are higher than 70% (Fig.2a). Afterwards, the removal rate decreases. After 90 min, the removal efficiency does not change and the plateaus is 98%. The difference in the degradation capability of the thin TiO 2 films is most obvious within the first 45 min (Fig.2b). The removal efficiencies of TS1, TS2, TS3, and TS4 films are higher than that of the pure TiO 2 film. The removal of Rhodamine B increases with increasing of CH4N2S electrolyte concentration. The maximum removal rate is achieved at 6.0
H2O 220 V
H2O
1. Ti sheet; 2. thermometer; 3. blender; 4. condensate; 5. electrical source; 6. copper sheet Fig.1
Pure TiO2
100
Removal Efficiency/%
0.5 mol/L H2SO4 electrolyte solution was used to prepare the film. CH4N2S was added to the electrolyte solution to form the S-doped thin TiO2 film. The S-doped thin TiO2 films were prepared using different CH4N2S concentrations, of 0.1, 2.0, 6.0, and 8.0 g/L denoted as TS1, TS2, TS3, and TS4, respectively. The MPO process was conducted in two 10 min stages. A direct current power supply was used in the experiment. A constant current density (12.5 A⋅dm-2) was first applied until a designated anode-to-cathode voltage (170 V) was reached. This voltage was kept until oxidation of the new film ended. Then, TiO2 films were rinsed with distilled water and dried in a baking oven at 100 °C. XRD with a Cu Kα source (D/max-r B from Ricoh) was used to study the crystalline structure of the prepared TiO2 films. The morphology of the produced films was examined by SEM (S-570 from Hitachi). A cylindrical quartz cell (25 mm in diameter and 50 mm in height) and a 20-W quartz–UV lamp (maximum UV irradiation peak of 365 nm) were used to fabricate the bench-scale photo-reactor system. 4.0 cm2 film samples were immersed in 15 mL of aqueous Rhodamine B solution (10 mg/L). UV light irradiation was applied for 2 h. Rhodamine B concentration was determined using a UV spectrophotometer.
Reaction unit of the micro plasma oxidation method
g/L CH4N2S (TS3). When the concentration is higher than 6.0 g/L CH4N2S, the removal rate decreases. 2.2 Analysis of SEM and EDS results The SEM images of undoped and doped TiO2 films are shown in Fig.3. Fig.3 shows that the five films exhibit uniform appearance with regular distribution of pores. In comparison with pure TiO2, the densities of the pores in TS1, TS2, TS3, and TS4 films increase and the pore sizes decrease with increasing of CH4N2S content. As the content of CH4N2S increases and reaches 6.0 g/L, the density of the pores reaches the maximum and the pore size reaches the minimum. At higher concentration (8.0 g/L), the density of the pores decreases and irregular pores appear. The EDS spectra of undoped and doped TiO2 films are shown in Fig.4 and Table 1. From the EDS spectrum, it can be seen that the undoped TiO2 film mainly contains Ti and O elements. After doping CH4N2S into the H2SO4 electrolyte, the S ions appear in the TiO2 film. 2.3 Crystal structural analysis of the prepared films The XRD patterns of the films are shown in Fig.5. Many sharp peaks are evident in the XRD patterns as shown in Fig.5a, indicating the presence of crystallization in the prepared films. The films primarily consist of the anatase phase with less rutile and titanium phases. No new crystal phases are associated with S doping. Fig.5b presents the enlarged XRD peaks of the anatase TiO2
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Yu Zhongchen et al. / Rare Metal Materials and Engineering, 2015, 44(7): 1629-1632
Table 1
a
Composition of MPO coating (wt/%)
Element TiO2 S-TiO2
O 31.11 26.39
Ti 68.89 72.59
S 01.03
a
Anatase Rutile Titanium
c
b
TS4
Intensity/a.u.
TS3 TS2 TS1 Undoped TiO2
20
30
40
50
60
70
80 b TS4
d
e
Intensity/a.u.
TS3 TS2 TS1 Undoped TiO2
24.5
2.0 μm Fig.3
Surface morphologies of the thin TiO2 films prepared under different conditions: (a) pure TiO2, (b) TS1, (c) TS2, (d) TS3,
Fig.5
25.0
25.5 2θ/(°)
26.0
26.5
XRD patterns (a) of the thin TiO2 films prepared under different conditions and the magnification (b)
and (e) TS4
Intensity/×103 cps
2.7
a
2.1 1.8 Ti
1.1 0.5 0.0
Au O Ti Au
1.00
3.00
5.00
7.00
9.00
Intensity/×103 cps
2.1
b
1.7 1.3 0.9 0.4 0.0
Ti Au O Ti
1.00
S
3.00
Au
5.00
7.00
9.00
Energy/keV Fig.4
EDS spectra of undoped and S-doped TiO2 thin films: (a) undoped and (b) S-doped
plane A (101) in the 2θ region of 24.5~26.5. It demonstrates that the XRD peaks of the crystal plane A (101) shifts to a higher diffraction angle. The full width at half maximum (FWHM) value increases when CH4N2S is added into the electrolyte. This change increases with increasing of CH4N2S concentration. The CH4N2S concentration of 6.0 g/L is associated with the widest FWHM. 2.4 Relationship of temperature, structure and physical properties Many factors affect the photocatalytic activity of TiO2 film such as crystalline structure, specific surface area, and porosity[14]. According to the Scherrer formula, a wide FWHM value results in small particle sizes. Fig.5 indicates that the grain size of TiO2 particles decreases after S doping. S4+ replaces Ti4+ in the crystal lattice, resulting in small grain sizes. Accordingly, these small grain sizes contribute to the larger surface area of the TiO2 film, resulting in the presence of more photocatalytic reaction sites; thereby the photocatalytic activity of the prepared TiO2 films is improved. The SEM images demonstrate that the density of the pores increases with increasing of S content. Hence, the photocatalytic activity of the films is improved because more mesopores can produce more reactive sites for adsorption and
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oxidation of pollutants. The surface grain size and the density of the pores do not increase at 8 g/L CH4N2S electrolyte. At this concentration, the dopants function as recombination centers for the photo-excited electrons and thus the photocatalytic efficiency is reduced. The S content is proportional to the CH4N2S content. A high concentration of CH4N2S results in high S content in the films. However, the removal efficiency of organic matter in the TiO2 film does not always increase with increasing of CH4N2S content. The CH4N2S concentration presents the optimal range. The XPS spectrum of S-doped film was used to analyze the element composition. S does not appear in the XPS spectrum, which may be due to the very low S content. Thus, this paper provides the EDS spectrum only. The changes in the surface morphology of the TiO2 film may be affected by S doping and CH4N2S in the electrolyte. CH4N2S is an anelectrolyte. The low content of CH4N2S minimally affects the MPO discharge. However, the surface morphology of the film exhibits significant changes caused by doping S into the TiO2 film. The high CH4N2S concentration affects the resistance of the electrolyte and the discharge of MPO. Correspondingly, the discharge hole decreases. Therefore, the specific surface area is small, resulting in decreased photocatalytic ability of the TiO2 film. This analysis is confirmed by the results of the photodegradation of Rhodamine B.
3
Conclusions
1) TiO2 films can be prepared via MPO with H2SO4 electrolyte solution. 2) The TiO2 films exhibit a high photocatalytic activity
when CH4N2S is added into the solution. The enhanced activity is related to the changes in the morphology and crystal structure induced by S doping.
References 1 Sriwong C, Wongnawa S, Patarapaiboolchai Rubber O. J Environ Sci[J], 2012, 24: 464 2 Du J J, Chen W, Zhang C et al. Chem Eng[J], 2011, 170: 53 3 Wen C, Zhu Y J, Kanbara T et al. Desalination[J], 2009, 249(5): 621 4 Hu X Y, Zhang T C, Jin Z et al. Mater Lett[J], 2008, 62: 4579 5 Mekprasart W, Pecharapa W. Energy Procedia[J], 2011, 9(14): 509 6 Asahi R, Morikawa T, Ohwaki T et al. Science[J], 2001, 293(71): 269 7 Ohno T, Mitsui T, Matsumura M. Chem Lett[J], 2003, 32(5): 364 8 Ohno T, Akiyoshi M, Umebayashi T et al. Appl Catal A[J], 2004, 265(21): 115 9 Terleeva O P, Sharkeev Y P, Slonova A I et al. Sur Coat Tech[J], 2010, 205(29): 1723 10 Awad S H, Qian H C. Wear[J], 2006, 260(22): 215 11 Rogov A B, Terleeva O P, Mironov I V et al. Applied Surface Science[J], 2012, 258(5): 2761 12 Shimizu Y, Sasaki T, Bose A C et al. Sur Coat Tech[J], 2006, 200(6): 4251 13 Li J M, Zhang Q W, Cai H et al. Rare Metal Materials and Engineering[J], 2013, 42(7): 2083 (in Chinese) 14 Su H D, Zhai Y C, Shao Z C et al. J Chi Rare Earth Soc[J], 2005, 23(7): 434
1632
ARTICLE
Photocatalytic Property of Nanostructured S Doped TiO2 Films Prepared by the Micro Plasma Method Yu Zhongchen1, 1
Wang Song1,
Han Lu2,
Li Zhuan1,
Niu Yuanlin 1
Northeastern Petroleum University, Daqing 163318, China；2 Hebei Normal University of Science and Technology, Qinghuangdao 066004,
China
Abstract: Mesoporous titanium dioxide thin films were prepared on titanium plates within a short time by a micro-plasma oxidation method. The films were used to degrade Rhodamine B, a textile industry pollutant. To increase the photocatalytic activity, different concentrations of CH4N2S were added into an H2SO4 electrolyte solution to make the doped S enter the films. X-ray diffraction and scanning electron microscopy were used to characterize the surface morphology, the composition, the crystal structure and microstructure of the modified films. Results show that the modified films are porous with different sizes of pores. The CH 4N2S concentration in the electrolyte solution has a greater influence on the micropore density and the pore size of the film. S-doping can increase micropore density and specific surface area of the film, somewhat alters its crystal lattice parameter, but affects its crystal structure only a little. The photo-catalytic activity will be enhanced effectively by S-doping, for example, when the CH4N2S concentration in the electrolyte solution is 6.0 g/L, the photocatalytic degradation of Rhodamine B with the initial concentration of 10 mg/L by TiO2 thin films reaches 98% within 120 min, showing the maximum photocatalytic degradation of TiO 2 films. Key words: TiO2 thin films; photocatalytic activity; S-doping
TiO2 is widely used as a photocatalyst because of its photochemical stability, nontoxicity, and low cost[1,2]. Several researchers doped TiO2 films with non-metal impurities to improve their photocatalytic performance[3–5]. Asahi et al. (2001) reported the doping of TiO2 with S ions[6]. S ion is difficult to be introduced into the crystal lattice of TiO2 because of its large diameter. Ohno demonstrated that S4+ can replace Ti4+ in the TiO2 crystal lattice to expand the absorption wavelength range and to improve the photocatalytic efficiency[7,8]. Nevertheless, the crystal structure of S-doped TiO2 has not been defined. TiO2 films could be prepared via micro-plasma oxidation (MPO), consisting of numerous simultaneous and uniform plasma discharges on a metal surface[9–11]. Homogenous films with good adherence to the substrate could be produced within a short time[12]. The dopant added to the electrolyte solution was readily incorporated into the film. MPO exhibits many advantages, such as fast reaction, simple
operation, and easy doping of ions into the electrolyte. The prepared film is directly connected with the electrolyte. Thus, ions can be easily doped into the film[13]. Different concentrations of CH4N2S were added into the electrolyte solution during MPO. In the present experiment S-doped films were prepared on titanium plates by MPO process using CH4N2S as dopant to evaluate the photocatalytic activity, crystal structure and surface morphology of S-TiO2 films so as to provide technical reference for further improvement of the photocatalytic property.
1
Experiment
Pure and S-doped thin TiO2 films were grown on a titanium substrate using the MPO method. The experiment reaction unit of MPO is shown in Fig.1. Thin TiO2 films were prepared as follows. A titanium sheet washed in a HF-HNO3 (1:1, V/V) aqueous solution was selected as an anode. The reaction area was 20 mm×10 mm. A copper sheet was used as a cathode. A
Received date: July 25, 2014 Foundation item: Scientific Research Foundation of the Educational Commission of Heilongjiang Province of China (12541066) Corresponding author: Yu Zhongchen, Master, Associate Professor, School of Civil Engineering & Architecture, Northeastern Petroleum University, Daqing 163318, P. R. China, Tel: 0086-459-6503117, E-mail: [email protected] Copyright © 2015, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.
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Yu Zhongchen et al. / Rare Metal Materials and Engineering, 2015, 44(7): 1629-1632
2
Removal Efficiency/%
TS2
TS1
TS3
TS4
80 60 40 20 0
15
30
45 b
100 80 Pure TiO2 TS1 TS2 TS3 TS4
60 40 20 0 0
Fig.2
a
15
30
45 60 75 Time/min
90 105 120
Photocatalytic degradation of Rhodamine B by TiO2 thin films produced at different conditions
Results and Discussion
2.1 Results of photo degradation of Rhodamine B The degradation of Rhodamine B by the thin TiO2 films was determined (Fig.2a and 2b). The results show that the rapid removal rate of Rhodamine B is before 45 min, and the removal efficiencies of all TiO2 films are higher than 70% (Fig.2a). Afterwards, the removal rate decreases. After 90 min, the removal efficiency does not change and the plateaus is 98%. The difference in the degradation capability of the thin TiO 2 films is most obvious within the first 45 min (Fig.2b). The removal efficiencies of TS1, TS2, TS3, and TS4 films are higher than that of the pure TiO 2 film. The removal of Rhodamine B increases with increasing of CH4N2S electrolyte concentration. The maximum removal rate is achieved at 6.0
H2O 220 V
H2O
1. Ti sheet; 2. thermometer; 3. blender; 4. condensate; 5. electrical source; 6. copper sheet Fig.1
Pure TiO2
100
Removal Efficiency/%
0.5 mol/L H2SO4 electrolyte solution was used to prepare the film. CH4N2S was added to the electrolyte solution to form the S-doped thin TiO2 film. The S-doped thin TiO2 films were prepared using different CH4N2S concentrations, of 0.1, 2.0, 6.0, and 8.0 g/L denoted as TS1, TS2, TS3, and TS4, respectively. The MPO process was conducted in two 10 min stages. A direct current power supply was used in the experiment. A constant current density (12.5 A⋅dm-2) was first applied until a designated anode-to-cathode voltage (170 V) was reached. This voltage was kept until oxidation of the new film ended. Then, TiO2 films were rinsed with distilled water and dried in a baking oven at 100 °C. XRD with a Cu Kα source (D/max-r B from Ricoh) was used to study the crystalline structure of the prepared TiO2 films. The morphology of the produced films was examined by SEM (S-570 from Hitachi). A cylindrical quartz cell (25 mm in diameter and 50 mm in height) and a 20-W quartz–UV lamp (maximum UV irradiation peak of 365 nm) were used to fabricate the bench-scale photo-reactor system. 4.0 cm2 film samples were immersed in 15 mL of aqueous Rhodamine B solution (10 mg/L). UV light irradiation was applied for 2 h. Rhodamine B concentration was determined using a UV spectrophotometer.
Reaction unit of the micro plasma oxidation method
g/L CH4N2S (TS3). When the concentration is higher than 6.0 g/L CH4N2S, the removal rate decreases. 2.2 Analysis of SEM and EDS results The SEM images of undoped and doped TiO2 films are shown in Fig.3. Fig.3 shows that the five films exhibit uniform appearance with regular distribution of pores. In comparison with pure TiO2, the densities of the pores in TS1, TS2, TS3, and TS4 films increase and the pore sizes decrease with increasing of CH4N2S content. As the content of CH4N2S increases and reaches 6.0 g/L, the density of the pores reaches the maximum and the pore size reaches the minimum. At higher concentration (8.0 g/L), the density of the pores decreases and irregular pores appear. The EDS spectra of undoped and doped TiO2 films are shown in Fig.4 and Table 1. From the EDS spectrum, it can be seen that the undoped TiO2 film mainly contains Ti and O elements. After doping CH4N2S into the H2SO4 electrolyte, the S ions appear in the TiO2 film. 2.3 Crystal structural analysis of the prepared films The XRD patterns of the films are shown in Fig.5. Many sharp peaks are evident in the XRD patterns as shown in Fig.5a, indicating the presence of crystallization in the prepared films. The films primarily consist of the anatase phase with less rutile and titanium phases. No new crystal phases are associated with S doping. Fig.5b presents the enlarged XRD peaks of the anatase TiO2
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Table 1
a
Composition of MPO coating (wt/%)
Element TiO2 S-TiO2
O 31.11 26.39
Ti 68.89 72.59
S 01.03
a
Anatase Rutile Titanium
c
b
TS4
Intensity/a.u.
TS3 TS2 TS1 Undoped TiO2
20
30
40
50
60
70
80 b TS4
d
e
Intensity/a.u.
TS3 TS2 TS1 Undoped TiO2
24.5
2.0 μm Fig.3
Surface morphologies of the thin TiO2 films prepared under different conditions: (a) pure TiO2, (b) TS1, (c) TS2, (d) TS3,
Fig.5
25.0
25.5 2θ/(°)
26.0
26.5
XRD patterns (a) of the thin TiO2 films prepared under different conditions and the magnification (b)
and (e) TS4
Intensity/×103 cps
2.7
a
2.1 1.8 Ti
1.1 0.5 0.0
Au O Ti Au
1.00
3.00
5.00
7.00
9.00
Intensity/×103 cps
2.1
b
1.7 1.3 0.9 0.4 0.0
Ti Au O Ti
1.00
S
3.00
Au
5.00
7.00
9.00
Energy/keV Fig.4
EDS spectra of undoped and S-doped TiO2 thin films: (a) undoped and (b) S-doped
plane A (101) in the 2θ region of 24.5~26.5. It demonstrates that the XRD peaks of the crystal plane A (101) shifts to a higher diffraction angle. The full width at half maximum (FWHM) value increases when CH4N2S is added into the electrolyte. This change increases with increasing of CH4N2S concentration. The CH4N2S concentration of 6.0 g/L is associated with the widest FWHM. 2.4 Relationship of temperature, structure and physical properties Many factors affect the photocatalytic activity of TiO2 film such as crystalline structure, specific surface area, and porosity[14]. According to the Scherrer formula, a wide FWHM value results in small particle sizes. Fig.5 indicates that the grain size of TiO2 particles decreases after S doping. S4+ replaces Ti4+ in the crystal lattice, resulting in small grain sizes. Accordingly, these small grain sizes contribute to the larger surface area of the TiO2 film, resulting in the presence of more photocatalytic reaction sites; thereby the photocatalytic activity of the prepared TiO2 films is improved. The SEM images demonstrate that the density of the pores increases with increasing of S content. Hence, the photocatalytic activity of the films is improved because more mesopores can produce more reactive sites for adsorption and
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oxidation of pollutants. The surface grain size and the density of the pores do not increase at 8 g/L CH4N2S electrolyte. At this concentration, the dopants function as recombination centers for the photo-excited electrons and thus the photocatalytic efficiency is reduced. The S content is proportional to the CH4N2S content. A high concentration of CH4N2S results in high S content in the films. However, the removal efficiency of organic matter in the TiO2 film does not always increase with increasing of CH4N2S content. The CH4N2S concentration presents the optimal range. The XPS spectrum of S-doped film was used to analyze the element composition. S does not appear in the XPS spectrum, which may be due to the very low S content. Thus, this paper provides the EDS spectrum only. The changes in the surface morphology of the TiO2 film may be affected by S doping and CH4N2S in the electrolyte. CH4N2S is an anelectrolyte. The low content of CH4N2S minimally affects the MPO discharge. However, the surface morphology of the film exhibits significant changes caused by doping S into the TiO2 film. The high CH4N2S concentration affects the resistance of the electrolyte and the discharge of MPO. Correspondingly, the discharge hole decreases. Therefore, the specific surface area is small, resulting in decreased photocatalytic ability of the TiO2 film. This analysis is confirmed by the results of the photodegradation of Rhodamine B.
3
Conclusions
1) TiO2 films can be prepared via MPO with H2SO4 electrolyte solution. 2) The TiO2 films exhibit a high photocatalytic activity
when CH4N2S is added into the solution. The enhanced activity is related to the changes in the morphology and crystal structure induced by S doping.
References 1 Sriwong C, Wongnawa S, Patarapaiboolchai Rubber O. J Environ Sci[J], 2012, 24: 464 2 Du J J, Chen W, Zhang C et al. Chem Eng[J], 2011, 170: 53 3 Wen C, Zhu Y J, Kanbara T et al. Desalination[J], 2009, 249(5): 621 4 Hu X Y, Zhang T C, Jin Z et al. Mater Lett[J], 2008, 62: 4579 5 Mekprasart W, Pecharapa W. Energy Procedia[J], 2011, 9(14): 509 6 Asahi R, Morikawa T, Ohwaki T et al. Science[J], 2001, 293(71): 269 7 Ohno T, Mitsui T, Matsumura M. Chem Lett[J], 2003, 32(5): 364 8 Ohno T, Akiyoshi M, Umebayashi T et al. Appl Catal A[J], 2004, 265(21): 115 9 Terleeva O P, Sharkeev Y P, Slonova A I et al. Sur Coat Tech[J], 2010, 205(29): 1723 10 Awad S H, Qian H C. Wear[J], 2006, 260(22): 215 11 Rogov A B, Terleeva O P, Mironov I V et al. Applied Surface Science[J], 2012, 258(5): 2761 12 Shimizu Y, Sasaki T, Bose A C et al. Sur Coat Tech[J], 2006, 200(6): 4251 13 Li J M, Zhang Q W, Cai H et al. Rare Metal Materials and Engineering[J], 2013, 42(7): 2083 (in Chinese) 14 Su H D, Zhai Y C, Shao Z C et al. J Chi Rare Earth Soc[J], 2005, 23(7): 434
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