- Email: [email protected]
One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method
Materials Letters xxx (xxxx) xxx
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method Yousong Liu a, Songhong Wang b, Peng Zheng a, Mengling Ding a, Guangcheng Yang a,⇑ a b
Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, PR China Department of Information Engineering, Laiwu Vocational and Technical College, Laiwu 271199, PR China
a r t i c l e
i n f o
Article history: Received 13 October 2019 Received in revised form 11 November 2019 Accepted 12 November 2019 Available online xxxx Keywords: AgN3 deflagration Ti3+-doped TiO2 Ag/TiO2 interfaces Nanocomposites Defects
a b s t r a c t Ag-decorated Ti3+-doped TiO2 nanocomposites featuring plentiful ultra-small Ag nanoparticles and Ti3+ ions are ideal materials for the photocatalytic degradation of organic pollutants due to the improved light-absorption ability and the separation rate of photo-generated carriers, resulting from the plasma effect of Ag nanoparticles, abundant Ag/TiO2 Schottky interferences, and Ti3+ ions. However, it is still a challenge to synthesize Ag-decorated Ti3+-doped TiO2 nanocomposites. Herein, we present an ultrafast deflagration method to transform energetic AgN3 nanoparticles to Ag particles at a size of several nanometers and to achieve Ti3+ doping using N radicals ablation in one-step. The extraordinary photocatalytic performance obtained verifies the practicability of this synthetic approach. Moreover, this work opens up a new approach to fabricating Ag-decorated and doped materials in one step and expands the scope for future material design. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Currently, much effort has been devoted to composite or doped photocatalytic materials for solving serious problems of lightabsorption and photo-generated electron–hole recombination with the increasing usage of photovoltaic devices and pollutant degradation reagents in energy conversion and environmental applications [1]. Taking the well-known semiconductor photocatalyst, TiO2, as an example, its utilization in solar energy conversion is limited to the ultraviolet region due to the wide band gap of ~3.2 eV; therefore, introducing foreign dopant into TiO2 [2], generating local defects (e.g. Ti3+ ions, oxygen defects, etc.) in TiO2 [3], and modifying TiO2 with novel metals have been widely adopted to enhance its photocarrier transfer and extend its lightabsorption range, thereby boosting the catalytic efficiency of TiO2. Dopants like metals or nonmetals can be exploited to generate extra impurity energy levels in TiO2 as a result of the electronic transition of the dopant. Among them, Ti3+-doping is attracting increasing interests owing to its abundant resources. Generally, local Ti3+ impurity can be generated by calcination or hydrothermal processes using reduction species [4] and treated by a high ⇑ Corresponding author. E-mail addresses: [email protected] (Y. Liu), [email protected] (S. Wang), [email protected] (P. Zheng), [email protected] (M. Ding), [email protected] (G. Yang).
energy particle flow (including nitrogen-ion implantation [5], ultraviolet pulsed laser ablation [6], and spark plasma sintering [7]); however, this treatment suffers from low efficiency, highpower dissipation, and being time-consuming. Ag-decorated TiO2 has been widely explored due to abundant Ag resources, the strong surface-plasmon-resonance effect of Ag nanoparticles, and Ag/TiO2 Schottky junction, which benefits the photocatalytic activity via improving the light absorption ability and photo-generated electron-hole separation. To date, many preparation methods such as solvothermal method [8], electrochemical synthesis [9], and strong electrostatic adsorption technique [10] have been developed to synthesize Ag/TiO2 nanocomposites; however, these methods have the drawbacks of low efficiency, insufficient contact, and being time-consuming. Therefore, it is still necessary to develop effective methods for efficient and controllable doping and Ag decorating. Herein, we designed an ultrafast one-step AgN3 deflagration method to fabricate Ag-decorated Ti3+-doped TiO2 nanocomposites (AT-TiO2). Once initiated, the energetic AgN3 nanoparticles decompose into Ag and N radicals and release a large amount of gases/ heat, causing the local to be decorated with Ag nanoparticles and N radicals to act as particle flow ablation introducing Ti3+ and oxygen vacancies doping. The as-obtained Ag-decorated Ti3+-doped TiO2 samples are composed of plentiful Ag nanoparticles, Ag/TiO2 Schottky junctions, and high Ti3+ ions and oxygen vacancies and exhibit superior photocatalytic performance.
https://doi.org/10.1016/j.matlet.2019.127016 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Y. Liu, S. Wang, P. Zheng et al., One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method, Materials Letters, https://doi.org/10.1016/j.matlet.2019.127016
2
Y. Liu et al. / Materials Letters xxx (xxxx) xxx
2. Experimental section 2.1. Synthesis procedure of AT-TiO2 TiO2 nanosheets were fabricated using a facile hydrothermal reaction reported elsewhere [11]. The procedure for the synthesis of Ag-TiO2 microporous nanosheets is as follows: 1.0 g of TiO2 nanosheets and a certain amount of AgNO3 were added into 5 mL deionized water to obtain a white homogeneous suspension. Then, a NaN3 solution was poured into the suspension to form a precipitate and followed by a freeze-drying process to obtain a mixture of TiO2 and AgN3. After the deflagration of AgN3, while annealing at ca. 300 °C under an N2 atmosphere, the product was washed with deionized water and dried at 60 °C for 12 h in a vacuum oven. Afterward, the product was labeled as AT-TiO2-X, where X presents the amounts of added AgNO3 and NaN3 (X 2 mmol). 2.2. Characterization The crystal structure and the morphology of all the samples were examined by X-ray diffraction analysis (XRD, Bruker D8 Advance with Cu-Ka radiation, k = 1.5418 Å) and transmission electron microscopy (TEM, JEOL JSM-2010). UV–visible absorption spectra were also obtained using a UV–visible spectrometer (Shimadzu UV-3600), and electron paramagnetic resonance spectra (EPR) were recorded at 110 K on a Bruker EMX-10/12 EPR spectrometer. X-ray photoelectron spectroscopy (XPS) analyses were performed using ESCALAB 250 XPS X-ray electron spectrometer (American Thermo Electron Corporation). 2.3. Photocatalytic measurements 100 mg of AT-TiO2-X was added to 200 mL of a rhodamine B (RhB) solution (7.5 mg L 1). A 300 W Xe arc lamp (CHF-XM500W, Beijing TrustTech Co. Ltd.) was used as the light source. Prior to irradiation, the RhB solution suspended with photocatalysts was stirred in the dark for 30 min. Then, 3 mL of the suspension was withdrawn throughout the experiment at 1-min intervals. The samples were analyzed using a UV–visible spectrophotometer after removing the catalyst powders by centrifugation. 3. Results and discussion The XRD patterns of the TiO2 nanosheets and the AT-TiO2 samples are shown in Fig. 1a. The diffraction peaks in the XRD pattern of the pristine TiO2 nanosheets are indexed to the anatase phase of TiO2 (JCPDS Card 21-1272). After AgN3 deflagration, new peaks at 38.3°, 44.4°, 64.7°, and 77.6° respectively corresponding to the
(1 1 1), (2 0 0), (2 2 0), and (3 1 1) planes of Ag (JCPDS Card 652871) can be observed. The Ag 3d XPS spectra in Fig. 1b display two strong peaks at 367.6 (Ag 3d3/2) and 373.6 eV (Ag 3d5/2). The energy difference between Ag 3d3/2 and Ag 3d5/2 splitting is approximately 6.0 eV, suggesting the formation of Ag metals. EPR was conducted to determine the presence of Ti3+ in the AT-TiO2 samples. Two EPR signal peaks at g = 1.93 and 2.01 can be seen from Fig. 1c, which can be assigned to Ti3+ and oxygen vacancies respectively. Thus, it can be inferred from the above results that Ag-decoration and Ti3+-doping can be accomplished by our designed AgN3 deflagration method. Moreover, the concentration of Ag nanoparticles and Ti3+ ions increased at higher amounts of AgN3 (Fig. S1 and Table S1). The structural features of the TiO2 nanosheets and the AT-TiO2 samples can be observed in the TEM images in Fig. 2. The pristine TiO2 nanosheets exhibited a square structure with a uniform size of about 50 nm (Fig. 2a) and exposed (1 0 1) facet with a lattice spacing of 0.35 nm (Fig. 2b). Compared with the pristine TiO2 nanosheets, the obtained AT-TiO2 samples showed many Ag nanoparticles (ca. 5 nm, dark-grey) decorated on the surfaces of the TiO2 nanosheets (light-grey), suggesting the formation of abundant Ag-TiO2 Schottky interfaces (Figs. 2c–h and S2). Moreover, the concentration and size of Ag nanoparticles in the AT-TiO2 samples increased by raising the amount of added AgN3. From the HRTEM image of the AT-TiO2-3 samples in Fig. 2h, the lattice plane spacing of 0.35 nm and 0.235 nm can be deduced, which can be assigned to the (1 0 1) facet of TiO2 and the (1 1 1) facet of Ag respectively, thereby directly illustrating the formation of small-size Ag/TiO2 Schottky interfaces. However, it should be noted that the short duration of high temperature environment from AgN3 deflagration resulted in a so-called incomplete wetting of Ag nanoparticles by TiO2, which is different from the reported grain boundary results of alloys after long anneals [12,13]. Fig. 3a depicts the UV–Vis absorption spectra of the TiO2 nanosheets and the AT-TiO2 composites. It can be seen that the pristine TiO2 only absorbed ultraviolet light at a wavelength of less than 387 nm. By contrast, the absorption intensity of the AT-TiO2 composites was greatly improved in the visible region and increased by raising the concentration of Ag nanoparticles and Ti3+ ions, which is in accordance with the color of the AT-TiO2 samples changing from light gray to dark black. The photocatalytic activity of the TiO2 nanosheets and AT-TiO2 samples was characterized using the degradation rate of RhB. As shown in Fig. 3b, the degradation rate of RhB in the presence of the pristine TiO2 was about 90% after 1 h of Xe arc lamp irradiation, while the AT-TiO2 samples completely degraded RhB within 10 min. Fig. 3c also illustrates the degradation kinetics curves of the pristine TiO2 and AT-TiO2 samples. The linearity of the ln(C0/ C) versus irradiation time suggests that the degradation of RhB
Fig. 1. The (a) XRD patterns, (b) Ag 3d XPS spectra, and (c) EPR spectra of the TiO2 and AT-TiO2 samples.
Please cite this article as: Y. Liu, S. Wang, P. Zheng et al., One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method, Materials Letters, https://doi.org/10.1016/j.matlet.2019.127016
Y. Liu et al. / Materials Letters xxx (xxxx) xxx
3
Fig. 2. TEM images of the pristine TiO2 nanosheets (a, b), the obtained AT-TiO2-1 (c, d), AT-TiO2-2 (e, f) and AT-TiO2-3 (g, h) samples.
Fig. 3. (a) Ultraviolet–visible diffuse reflectance spectra of TiO2 and AT-TiO2; the inset is the photo of TiO2 and AT-TiO2 samples; (b) the rate-time curve of Rhodamine B degradation under xenon lamp irradiation; (c) the degradation kinetics (ln(C0/C)–time curve) of TiO2 and AT-TiO2 as the photocatalyst; (d) schematic diagram of the energy band structure and charge transfer of the AT-TiO2 samples.
Please cite this article as: Y. Liu, S. Wang, P. Zheng et al., One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method, Materials Letters, https://doi.org/10.1016/j.matlet.2019.127016
4
Y. Liu et al. / Materials Letters xxx (xxxx) xxx
should be a first-order reaction. The calculated kinetic constant of the RhB photocatalytic degradation by TiO2 was 0.0344 min 1, while the kinetic constants of the RhB photocatalytic degradation by the AT-TiO2-1, AT-TiO2-2, and AT-TiO2-3 samples were respectively 0.326, 0.437, and 0.511 min 1, which were 9.48, 12.70, and 14.85 times larger than that of the pristine TiO2 nanosheets, respectively. The improved photocatalytic properties of the AT-TiO2 could be attributed to the synergistic effect of Ag nanoparticles decoration and Ti3+ doping. It enhanced the visible light absorption intensity and helped to increase the concentration of the photo-generated carriers and improve the separation efficiency through Ti3+doping and Ag/TiO2 interfaces as demonstrated in Fig. 3d. 4. Conclusions In summary, we have presented an ultra-fast one-step AgN3 deflagration method to fabricate Ag-decorated Ti3+-doped TiO2 nanocomposites. It is found that the AT-TiO2 samples present stronger light absorption properties compared to the pristine TiO2 as a result of the effect of Ag nanoparticles and Ti3+ doping on TiO2. An optimized AT-TiO2 sample exhibited a 14.85-fold enhancement of the rhodamine B photodegradation under Xe arc lamp irradiation. Our designed deflagration synthesis technique can be extended to the preparation of other advanced materials in an efficient way. CRediT authorship contribution statement Yousong Liu: Writing - original draft. Songhong Wang: Data curation. Peng Zheng: Data curation. Mengling Ding: Validation. Guangcheng Yang: Writing - review & editing.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (grant numbers 11702264, 11702268, 21703217, 11772307, and 11802276). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.matlet.2019.127016. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
H. Tong, S. Ouyang, Y. Bi, et al., Adv. Mater. 24 (2012) 229–251. Y. Liu, S. Ouyang, W. Guo, et al., Nano Res. 11 (2018) 4735–4743. Y. Ji, Y. Luo, J. Am. Chem. Soc. 138 (2016) 15896–15902. F. Zuo, K. Bozhilov, R.J. Dillon, et al., Angew. Chem. Int. Ed. 51 (2012) 6223– 6226. X. Zhou, V. Häublein, N. Liu, et al., Angew. Chem. Int. Ed. 55 (2016) 3763–3767. S. Pan, X. Liu, M. Guo, et al., J. Mater. Chem. A 3 (2015) 11437–11443. Y. Yang, T. Zhang, L. Le, et al., Sci. Rep. 4 (2014) 7045. C. Su, L. Liu, M. Zhang, et al., CrystEngComm 14 (2012) 3989–3999. C. Gaidau, A. Petica, M. Ignat, et al., Open Chem. 14 (2016) 383–392. C. Cao, J. Huang, L. Li, et al., RSC Adv. 7 (2017) 13347–13352. X. Han, Q. Kuang, M. Jin, et al., J. Am. Chem. Soc. 131 (2009) 3152–3153. B.B. Straumal, O.A. Kogtenkova, A.B. Straumal, et al., J. Mater. Sci. 45 (2010) 4271–4275. B.B. Straumal, A.A. Mazilkin, S.G. Protasova, et al., Rev. Adv. Mater. Sci. 38 (2014) 17–28.
Please cite this article as: Y. Liu, S. Wang, P. Zheng et al., One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method, Materials Letters, https://doi.org/10.1016/j.matlet.2019.127016
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method Yousong Liu a, Songhong Wang b, Peng Zheng a, Mengling Ding a, Guangcheng Yang a,⇑ a b
Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, PR China Department of Information Engineering, Laiwu Vocational and Technical College, Laiwu 271199, PR China
a r t i c l e
i n f o
Article history: Received 13 October 2019 Received in revised form 11 November 2019 Accepted 12 November 2019 Available online xxxx Keywords: AgN3 deflagration Ti3+-doped TiO2 Ag/TiO2 interfaces Nanocomposites Defects
a b s t r a c t Ag-decorated Ti3+-doped TiO2 nanocomposites featuring plentiful ultra-small Ag nanoparticles and Ti3+ ions are ideal materials for the photocatalytic degradation of organic pollutants due to the improved light-absorption ability and the separation rate of photo-generated carriers, resulting from the plasma effect of Ag nanoparticles, abundant Ag/TiO2 Schottky interferences, and Ti3+ ions. However, it is still a challenge to synthesize Ag-decorated Ti3+-doped TiO2 nanocomposites. Herein, we present an ultrafast deflagration method to transform energetic AgN3 nanoparticles to Ag particles at a size of several nanometers and to achieve Ti3+ doping using N radicals ablation in one-step. The extraordinary photocatalytic performance obtained verifies the practicability of this synthetic approach. Moreover, this work opens up a new approach to fabricating Ag-decorated and doped materials in one step and expands the scope for future material design. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Currently, much effort has been devoted to composite or doped photocatalytic materials for solving serious problems of lightabsorption and photo-generated electron–hole recombination with the increasing usage of photovoltaic devices and pollutant degradation reagents in energy conversion and environmental applications [1]. Taking the well-known semiconductor photocatalyst, TiO2, as an example, its utilization in solar energy conversion is limited to the ultraviolet region due to the wide band gap of ~3.2 eV; therefore, introducing foreign dopant into TiO2 [2], generating local defects (e.g. Ti3+ ions, oxygen defects, etc.) in TiO2 [3], and modifying TiO2 with novel metals have been widely adopted to enhance its photocarrier transfer and extend its lightabsorption range, thereby boosting the catalytic efficiency of TiO2. Dopants like metals or nonmetals can be exploited to generate extra impurity energy levels in TiO2 as a result of the electronic transition of the dopant. Among them, Ti3+-doping is attracting increasing interests owing to its abundant resources. Generally, local Ti3+ impurity can be generated by calcination or hydrothermal processes using reduction species [4] and treated by a high ⇑ Corresponding author. E-mail addresses: [email protected] (Y. Liu), [email protected] (S. Wang), [email protected] (P. Zheng), [email protected] (M. Ding), [email protected] (G. Yang).
energy particle flow (including nitrogen-ion implantation [5], ultraviolet pulsed laser ablation [6], and spark plasma sintering [7]); however, this treatment suffers from low efficiency, highpower dissipation, and being time-consuming. Ag-decorated TiO2 has been widely explored due to abundant Ag resources, the strong surface-plasmon-resonance effect of Ag nanoparticles, and Ag/TiO2 Schottky junction, which benefits the photocatalytic activity via improving the light absorption ability and photo-generated electron-hole separation. To date, many preparation methods such as solvothermal method [8], electrochemical synthesis [9], and strong electrostatic adsorption technique [10] have been developed to synthesize Ag/TiO2 nanocomposites; however, these methods have the drawbacks of low efficiency, insufficient contact, and being time-consuming. Therefore, it is still necessary to develop effective methods for efficient and controllable doping and Ag decorating. Herein, we designed an ultrafast one-step AgN3 deflagration method to fabricate Ag-decorated Ti3+-doped TiO2 nanocomposites (AT-TiO2). Once initiated, the energetic AgN3 nanoparticles decompose into Ag and N radicals and release a large amount of gases/ heat, causing the local to be decorated with Ag nanoparticles and N radicals to act as particle flow ablation introducing Ti3+ and oxygen vacancies doping. The as-obtained Ag-decorated Ti3+-doped TiO2 samples are composed of plentiful Ag nanoparticles, Ag/TiO2 Schottky junctions, and high Ti3+ ions and oxygen vacancies and exhibit superior photocatalytic performance.
https://doi.org/10.1016/j.matlet.2019.127016 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Y. Liu, S. Wang, P. Zheng et al., One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method, Materials Letters, https://doi.org/10.1016/j.matlet.2019.127016
2
Y. Liu et al. / Materials Letters xxx (xxxx) xxx
2. Experimental section 2.1. Synthesis procedure of AT-TiO2 TiO2 nanosheets were fabricated using a facile hydrothermal reaction reported elsewhere [11]. The procedure for the synthesis of Ag-TiO2 microporous nanosheets is as follows: 1.0 g of TiO2 nanosheets and a certain amount of AgNO3 were added into 5 mL deionized water to obtain a white homogeneous suspension. Then, a NaN3 solution was poured into the suspension to form a precipitate and followed by a freeze-drying process to obtain a mixture of TiO2 and AgN3. After the deflagration of AgN3, while annealing at ca. 300 °C under an N2 atmosphere, the product was washed with deionized water and dried at 60 °C for 12 h in a vacuum oven. Afterward, the product was labeled as AT-TiO2-X, where X presents the amounts of added AgNO3 and NaN3 (X 2 mmol). 2.2. Characterization The crystal structure and the morphology of all the samples were examined by X-ray diffraction analysis (XRD, Bruker D8 Advance with Cu-Ka radiation, k = 1.5418 Å) and transmission electron microscopy (TEM, JEOL JSM-2010). UV–visible absorption spectra were also obtained using a UV–visible spectrometer (Shimadzu UV-3600), and electron paramagnetic resonance spectra (EPR) were recorded at 110 K on a Bruker EMX-10/12 EPR spectrometer. X-ray photoelectron spectroscopy (XPS) analyses were performed using ESCALAB 250 XPS X-ray electron spectrometer (American Thermo Electron Corporation). 2.3. Photocatalytic measurements 100 mg of AT-TiO2-X was added to 200 mL of a rhodamine B (RhB) solution (7.5 mg L 1). A 300 W Xe arc lamp (CHF-XM500W, Beijing TrustTech Co. Ltd.) was used as the light source. Prior to irradiation, the RhB solution suspended with photocatalysts was stirred in the dark for 30 min. Then, 3 mL of the suspension was withdrawn throughout the experiment at 1-min intervals. The samples were analyzed using a UV–visible spectrophotometer after removing the catalyst powders by centrifugation. 3. Results and discussion The XRD patterns of the TiO2 nanosheets and the AT-TiO2 samples are shown in Fig. 1a. The diffraction peaks in the XRD pattern of the pristine TiO2 nanosheets are indexed to the anatase phase of TiO2 (JCPDS Card 21-1272). After AgN3 deflagration, new peaks at 38.3°, 44.4°, 64.7°, and 77.6° respectively corresponding to the
(1 1 1), (2 0 0), (2 2 0), and (3 1 1) planes of Ag (JCPDS Card 652871) can be observed. The Ag 3d XPS spectra in Fig. 1b display two strong peaks at 367.6 (Ag 3d3/2) and 373.6 eV (Ag 3d5/2). The energy difference between Ag 3d3/2 and Ag 3d5/2 splitting is approximately 6.0 eV, suggesting the formation of Ag metals. EPR was conducted to determine the presence of Ti3+ in the AT-TiO2 samples. Two EPR signal peaks at g = 1.93 and 2.01 can be seen from Fig. 1c, which can be assigned to Ti3+ and oxygen vacancies respectively. Thus, it can be inferred from the above results that Ag-decoration and Ti3+-doping can be accomplished by our designed AgN3 deflagration method. Moreover, the concentration of Ag nanoparticles and Ti3+ ions increased at higher amounts of AgN3 (Fig. S1 and Table S1). The structural features of the TiO2 nanosheets and the AT-TiO2 samples can be observed in the TEM images in Fig. 2. The pristine TiO2 nanosheets exhibited a square structure with a uniform size of about 50 nm (Fig. 2a) and exposed (1 0 1) facet with a lattice spacing of 0.35 nm (Fig. 2b). Compared with the pristine TiO2 nanosheets, the obtained AT-TiO2 samples showed many Ag nanoparticles (ca. 5 nm, dark-grey) decorated on the surfaces of the TiO2 nanosheets (light-grey), suggesting the formation of abundant Ag-TiO2 Schottky interfaces (Figs. 2c–h and S2). Moreover, the concentration and size of Ag nanoparticles in the AT-TiO2 samples increased by raising the amount of added AgN3. From the HRTEM image of the AT-TiO2-3 samples in Fig. 2h, the lattice plane spacing of 0.35 nm and 0.235 nm can be deduced, which can be assigned to the (1 0 1) facet of TiO2 and the (1 1 1) facet of Ag respectively, thereby directly illustrating the formation of small-size Ag/TiO2 Schottky interfaces. However, it should be noted that the short duration of high temperature environment from AgN3 deflagration resulted in a so-called incomplete wetting of Ag nanoparticles by TiO2, which is different from the reported grain boundary results of alloys after long anneals [12,13]. Fig. 3a depicts the UV–Vis absorption spectra of the TiO2 nanosheets and the AT-TiO2 composites. It can be seen that the pristine TiO2 only absorbed ultraviolet light at a wavelength of less than 387 nm. By contrast, the absorption intensity of the AT-TiO2 composites was greatly improved in the visible region and increased by raising the concentration of Ag nanoparticles and Ti3+ ions, which is in accordance with the color of the AT-TiO2 samples changing from light gray to dark black. The photocatalytic activity of the TiO2 nanosheets and AT-TiO2 samples was characterized using the degradation rate of RhB. As shown in Fig. 3b, the degradation rate of RhB in the presence of the pristine TiO2 was about 90% after 1 h of Xe arc lamp irradiation, while the AT-TiO2 samples completely degraded RhB within 10 min. Fig. 3c also illustrates the degradation kinetics curves of the pristine TiO2 and AT-TiO2 samples. The linearity of the ln(C0/ C) versus irradiation time suggests that the degradation of RhB
Fig. 1. The (a) XRD patterns, (b) Ag 3d XPS spectra, and (c) EPR spectra of the TiO2 and AT-TiO2 samples.
Please cite this article as: Y. Liu, S. Wang, P. Zheng et al., One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method, Materials Letters, https://doi.org/10.1016/j.matlet.2019.127016
Y. Liu et al. / Materials Letters xxx (xxxx) xxx
3
Fig. 2. TEM images of the pristine TiO2 nanosheets (a, b), the obtained AT-TiO2-1 (c, d), AT-TiO2-2 (e, f) and AT-TiO2-3 (g, h) samples.
Fig. 3. (a) Ultraviolet–visible diffuse reflectance spectra of TiO2 and AT-TiO2; the inset is the photo of TiO2 and AT-TiO2 samples; (b) the rate-time curve of Rhodamine B degradation under xenon lamp irradiation; (c) the degradation kinetics (ln(C0/C)–time curve) of TiO2 and AT-TiO2 as the photocatalyst; (d) schematic diagram of the energy band structure and charge transfer of the AT-TiO2 samples.
Please cite this article as: Y. Liu, S. Wang, P. Zheng et al., One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method, Materials Letters, https://doi.org/10.1016/j.matlet.2019.127016
4
Y. Liu et al. / Materials Letters xxx (xxxx) xxx
should be a first-order reaction. The calculated kinetic constant of the RhB photocatalytic degradation by TiO2 was 0.0344 min 1, while the kinetic constants of the RhB photocatalytic degradation by the AT-TiO2-1, AT-TiO2-2, and AT-TiO2-3 samples were respectively 0.326, 0.437, and 0.511 min 1, which were 9.48, 12.70, and 14.85 times larger than that of the pristine TiO2 nanosheets, respectively. The improved photocatalytic properties of the AT-TiO2 could be attributed to the synergistic effect of Ag nanoparticles decoration and Ti3+ doping. It enhanced the visible light absorption intensity and helped to increase the concentration of the photo-generated carriers and improve the separation efficiency through Ti3+doping and Ag/TiO2 interfaces as demonstrated in Fig. 3d. 4. Conclusions In summary, we have presented an ultra-fast one-step AgN3 deflagration method to fabricate Ag-decorated Ti3+-doped TiO2 nanocomposites. It is found that the AT-TiO2 samples present stronger light absorption properties compared to the pristine TiO2 as a result of the effect of Ag nanoparticles and Ti3+ doping on TiO2. An optimized AT-TiO2 sample exhibited a 14.85-fold enhancement of the rhodamine B photodegradation under Xe arc lamp irradiation. Our designed deflagration synthesis technique can be extended to the preparation of other advanced materials in an efficient way. CRediT authorship contribution statement Yousong Liu: Writing - original draft. Songhong Wang: Data curation. Peng Zheng: Data curation. Mengling Ding: Validation. Guangcheng Yang: Writing - review & editing.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (grant numbers 11702264, 11702268, 21703217, 11772307, and 11802276). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.matlet.2019.127016. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
H. Tong, S. Ouyang, Y. Bi, et al., Adv. Mater. 24 (2012) 229–251. Y. Liu, S. Ouyang, W. Guo, et al., Nano Res. 11 (2018) 4735–4743. Y. Ji, Y. Luo, J. Am. Chem. Soc. 138 (2016) 15896–15902. F. Zuo, K. Bozhilov, R.J. Dillon, et al., Angew. Chem. Int. Ed. 51 (2012) 6223– 6226. X. Zhou, V. Häublein, N. Liu, et al., Angew. Chem. Int. Ed. 55 (2016) 3763–3767. S. Pan, X. Liu, M. Guo, et al., J. Mater. Chem. A 3 (2015) 11437–11443. Y. Yang, T. Zhang, L. Le, et al., Sci. Rep. 4 (2014) 7045. C. Su, L. Liu, M. Zhang, et al., CrystEngComm 14 (2012) 3989–3999. C. Gaidau, A. Petica, M. Ignat, et al., Open Chem. 14 (2016) 383–392. C. Cao, J. Huang, L. Li, et al., RSC Adv. 7 (2017) 13347–13352. X. Han, Q. Kuang, M. Jin, et al., J. Am. Chem. Soc. 131 (2009) 3152–3153. B.B. Straumal, O.A. Kogtenkova, A.B. Straumal, et al., J. Mater. Sci. 45 (2010) 4271–4275. B.B. Straumal, A.A. Mazilkin, S.G. Protasova, et al., Rev. Adv. Mater. Sci. 38 (2014) 17–28.
Please cite this article as: Y. Liu, S. Wang, P. Zheng et al., One-step synthesis of Ag-decorated Ti3+-doped TiO2 nanosheets with improved photocatalytic properties via deflagration method, Materials Letters, https://doi.org/10.1016/j.matlet.2019.127016