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Topotactic soft chemical synthesis and photocatalytic performance of one-dimensional AgNbO3 nanostructures
Materials Letters 137 (2014) 110–112
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Topotactic soft chemical synthesis and photocatalytic performance of one-dimensional AgNbO3 nanostructures Liyun Cao a, Zhanglin Guo a, Jianfeng Huang a, Cuiyan Li a, Jie Fei a, Qi Feng b, Puhong Wen c, Youquan Sun d, Xingang Kong a,d,n a
School of Materials Science and Engineering, Shaanxi University of Science and Technology, Weiyang, Xi'an, Shaanxi 710021, PR China Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu-shi 761-0396, Japan c Department of Chemistry and Chemical Engineering, Baoji University of Arts and Science, 1 Gaoxin Road, Baoji, Shaanxi 721013, PR China d Anhui Deli Household Glass Co., Ltd., Fengyang Gate Taiwan Industrial Park, Anhui 223121, PR China b
art ic l e i nf o
a b s t r a c t
Article history: Received 4 July 2014 Accepted 28 August 2014 Available online 6 September 2014
A topotactic soft chemical process was used for the synthesis of one-dimensional AgNbO3 nanostructures. Firstly, using a tunnel structure potassium niobate K2Nb2O6 nH2O filiform crystal as precursor, the K þ in K2Nb2O6 nH2O were exchanged by an Ag þ in the AgNO3 water solution, forming Ag þ ionexchanged sample. Secondly, the Ag þ ion-exchanged sample was heat-treated to obtain the perovskite AgNbO3 by in situ topotactic structural transformation reaction. The one-dimensional nanostructured AgNbO3 was characterized by XRD, FE-SEM, TEM, SAED, EDS and UV–vis diffuse reflectance spectra. The one-dimensional AgNbO3 nanostructures were constructed from nanocrystals arranged along [011]crystal axis and with predominantly exposed (100) facet. The samples were able to degrade MB under ultraviolet irradiation and catalyze water-splitting in aqueous solution under illumination of visible light. Crown Copyright & 2014 Published by Elsevier B.V. All rights reserved.
Keywords: In situ topotactic AgNbO3 One-dimensional Semiconductors Microstructure Nanocrystalline materials
1. Introduction The soft chemical process is a useful method for the preparation of particles with controlled morphology, grain size, chemical composition, and nanostructure [1–3]. The process typically comprises two steps: the first step is the preparation of a framework precursor, and the second step is the structural transformation of the template precursor into a desired structure. Since the structural transformation in the soft chemical process is an in situ topotactic structural transformation reaction, the morphology of the precursor can be retained after the reaction. This in situ topotactic structural transformation has been widely used in synthesizing various kinds of materials with special structures and morphologies, such as plate like Ba0.5(Bi0.5K0.5)0.5TiO3 nanostructures [2], tunnel structured manganese oxide [3], and mixed layered Ni(OH)2–manganese oxides [4]. Therefore layered or tunnel structured compounds, because of their ion-exchange property, are suitable as precursors for synthesizing and designing the photocatalytic materials [5,6].
n Corresponding author at: School of Materials Science and Engineering, Shaanxi University of Science and Technology, Weiyang, Xi'an, Shaanxi 710021, PR China. Tel./fax: þ 86 29 86168802. E-mail address: [email protected] (X. Kong).
http://dx.doi.org/10.1016/j.matlet.2014.08.150 0167-577X/Crown Copyright & 2014 Published by Elsevier B.V. All rights reserved.
Recently, photocatalytic performance of AgNbO3 was abundantly reported [7–10]. The photocatalytic reaction and efficiency are closely related to the morphology and micro-structure of the material because photocatalytic actions are typically surface-based processes. However the AgNbO3 particles obtained by normal methods, such as solid-state reaction [7], the sol–gel method [8], molten-salt method [9] and solvothermal method [10], usually have cubic or irregular morphologies. Through these traditional methods it is difficult to simultaneously control chemical composition, grain size, morphology and nanostructure of product particles. In this paper, therefore, we describe a soft chemical synthesis of one-dimensional AgNbO3 nanostructures from the tunnel structure K2Nb2O6 nH2O filiform crystal. And the sample's photocatalytic performances were investigated by decomposing the dye MB and evolving O2 via water splitting.
2. Experimental 0.5 g of tunnel structured K2Nb2O6 nH2O fibrous crystal [11] was put into a 0.5 mol L 1 AgNO3 water solution, and then stirred and ion-exchanged for 24 h at room temperature. The ionexchange was performed twice for K þ of the K2Nb2O6 nH2O to be exchanged completely with Ag þ . After ion-exchange, the products were filtered, washed with distilled water, and dried at
L. Cao et al. / Materials Letters 137 (2014) 110–112
room temperature. The Ag þ -exchanged samples were obtained. Finally, the Ag þ -exchanged sample was heat-treated at 500 1C for 2 h to obtain the perovskite structured one-dimensional AgNbO3 nanostructures. The products were analyzed by XRD (D/max-2200) using CuKα radiation (λ ¼0.154 nm). The morphology study and characterization of the products were performed by FE-SEM (Hitachi S-4800) and TEM (FEI Tecnai G2 F20). UV–vis absorption spectra were recorded on a UV/vis/NIR spectrophotometer (LAMBDA950, PerkinElmer).The photocatalytic activities of samples were evaluated by degradation of methylene blue (MB) under xenon lamp and mercury lamp irradiation. 50 mg of AgNbO3 sample was added into the solution (50 mL, 10 mg L 1). The suspensions were magnetically stirred in dark for 40 min to ensure the establishment of an adsorption–desorption equilibrium. Then, the solution was exposed to the lamp irradiation. The concentrations of the remnant dye in the collected solution were monitored by UV–vis spectroscopy (Unico UV-2600) each for 10 min. The photocatalytic O2 evolution experiments were performed in a 300 mL quartz reactor at ambient temperature. The reactor was connected to a closed circulating system. A PLSSXE 300UV Xe arc lamp with a UV-cutoff filter (4400 nm) was used. 0.1 g of photocatalyst powder was dispersed in 100 mL of 0.05 mol L 1 AgNO3 solution. The O2 evolution was detected by gas chromatography (Shimadzu GC-8A).
3. Result and discussion In the previous study [11] we have reported the synthesis of a tunnel structure niobate K2Nb2O6 nH2O which is composed of NbO6 and KO6 octahedrons with the remaining K þ occupying the tunnel sites, and is a single particle with fiber-like morphology. Fig. 1a shows the XRD patterns of samples of K2Nb2O6 nH2O precursor. It was found that the precursor K2Nb2O6 nH2O possessed a characteristic peak of tunnel structure near 2θ ¼101 and fine crystallinity. After the K2Nb2O6 nH2O precursor was ionexchanged with Ag þ ion in the 0.5 mol L 1 AgNO3 water solution the Ag þ -exchanged sample retained the tunnel structure, though its characteristic peak widened (Fig. 1b). The chemical composition analysis result reveals that no K component is detected, and the mole ratio of Ag and Nb is 0.99/1, which is not consistent with our report that the K þ ions in the K2Nb2O6 precursor cannot be completely exchanged with the Li þ in LiCl water solution [11]. The reason was that AgNO3 water solution presented acidity,
111
whereas the KO6 octahedral layers in the tunnel structural framework were not steady and were easily dissolved in the acid environment [11]. Thus, the K þ ions in the KO6 octahedral layers were dissolved out. According to the TG–DTA analysis of the Ag þ -exchanged sample we found that it had an exothermic peak at 500 1C, which indicates the existence of a phase transition. Fig. 1c shows the XRD patterns of samples obtained by heat-treating the Ag þ -exchanged sample at 500 1C for 2 h. It was found that a pure orthorhombic AgNbO3 phase (JCPDS No. 22-0471) was formed after the heattreatment of the Ag þ -exchanged sample. The chemical composition analysis indicated that the mole ratio of Ag to Nb was the same in samples before and after the heat-treatment. The Ag þ -exchanged sample showed a fiber-like morphology with the size of about 2 μm in width and 50 μm in length, which was the same as that of K2Nb2O6 nH2O precursor (Fig. 2). The obtained AgNbO3 sample still retained the fiber-like morphology, and its size almost had no change compared with that of the precursors. These results suggested that in situ topotactic transition reaction occurred from the tunnel structure K2Nb2O6 nH2O to the perovskite AgNbO3. The size and morphology of the AgNbO3 sample were dependent on those of the precursor. Similar to AgNbO3 sample's SEM images the TEM images of AgNbO3 sample also presented filaments that were constructed from nanocrystals (Fig. 2d), meaning one-dimensional nanostructures. It is very interesting that the SAED pattern of the AgNbO3 one-dimensional nanostructures shows one set of diffraction spots similar to those of a single crystal, which correspond to the (100) and (011) planes of the perovskite structured AgNbO3. This result suggests that all the AgNbO3 nanoparticles in one-dimensional nanostructures have the same crystal-axis orientation, and all the AgNbO3 nanoparticles grow along the [011]-crystal-axis. These one-dimensional nanostructures predominately exposed the (100) facet. Fig. 3a shows the UV–vis diffuse reflectance spectra of onedimensional AgNbO3 nanostructures. It was seen that the AgNbO3 sample displayed the absorption edges in the ultraviolet light region of 300–400 nm, same as that of the AgNbO3 samples reported in the literature [12]. In the visible light region of 550– 650 nm, however, our AgNbO3 sample presented a stronger absorption than that of the literature [12], and dark gray color (Fig. 3b). The photocatalytic performance of the AgNbO3 onedimensional nanostructures was evaluated by degradation of 10 mol L 1 MB solution under xenon lamp and mercury lamp irradiation. As shown in the Fig. 3c, the AgNbO3 sample reached the degradation efficiency of 98.8% for MB after UV-irradiation for 30 min. The degradation efficiency for MB is only 24.4% under visible light irradiation for 30 min which is less than that of the reported literature (MB degradation efficiency of 85%) [8]. In the visible light photocatalytic O2 evolution experiments, however, the O2 evolution quantity was about 27 μmol h 1, higher than that 14 μmol h 1 of AgNbO3 sample prepared by conventional solidstate reactions [7]. This may be attributed to the fact that AgNbO3 nanocrystal with exposed (100) facet in one-dimensional nanostructures is generally beneficial for surface-based photocatalysed water splitting. The exposed (100) facet may provide more reaction sites [13]. Here, the detailed photocatalytic mechanism of the one-dimensional AgNbO3 nanostructures is not discussed.
4. Conclusions
Fig. 1. XRD patterns of K2Nb2O6 nH2O precursor (a), Ag þ -exchanged sample (b), and the sample obtained by heat-treating Ag þ -exchanged sample (c).
Perovskite one-dimensional AgNbO3 nanostructures were successfully synthesized by in situ topotactic transition reaction. Results show that one-dimensional nanostructures were constructed
112
L. Cao et al. / Materials Letters 137 (2014) 110–112
Fig. 2. FE-SEM (a)–(c) and TEM (d) images of samples. K2Nb2O6 nH2O precursor (a), Ag þ -exchanged sample (b) and AgNbO3 sample (c, d).
Acknowledgments The authors acknowledgment the support of Natural Science Basic Research Plan in Shaanxi Province of China (Program No. 2013JQ6012), China Postdoctoral Science Foundation (Program No. 2013M542314), the Research Starting Foundation from Shaanxi University of Science and Technology (BJ12-22), and Innovation Team Assistance Foundation of Shaanxi Province (Grant No. 2013KCT-06).
References
Fig. 3. UV–visible diffuse reflectance spectra (a), color photo (b) and photocatalytic degradation for MB results (c) of AgNbO3 nanostructures. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
from AgNbO3 nanocrystals arranged along the [011]-crystal axis. The samples were found to be capable of photodegrading MB and the photodegradation rate reached 98.8% after 30 min under ultraviolet irradiation. The O2 evolution by water-splitting with sacrificial reagents under visible light irradiation of the onedimensional nanostructures was about 27 μmol h 1. It is believed that other new types of functional niobates may also be obtained by the topotactic soft chemical process.
[1] Feng Q, Hirasawa M, Kajiyoshi K, Yanagisawa K. J Am Ceram Soc 2005;88 (6):1415–20. [2] Kong X, Hu D, Ishikawa Y, Tanaka Y, Feng Q. Chem Mater 2011;23 (17):3978–86. [3] Feng Q, Yanagawa K, Yamasaki N. J Porous Mater 1998;5(2):153–62. [4] Xu Y, Feng Q, Kajiyoshi K, Yanagisawa K, Yang X, Makita Y, et al. Chem Mater 2002;14(9):3844–51. [5] Li L, Deng J, Chen J, Sun X, Yu R, Liu G, et al. Chem Mater 2009;21(7):1207–13. [6] Sayama K, Tanaka A, Domen K, Maruya K, Onishi T. J Phys Chem 1991;95 (3):1345–8. [7] Kato H, Kobayashi H, Kudo A. J Phys Chem B 2002;106(48):12441–7. [8] Wu W, Liang S, Chen Y, Shen L, Yuan R, Wu L. Mater Res Bull 2013;48 (4):1618–26. [9] Arney D, Hardy C, Greve B, Maggard PA. J Photochem Photobiol A 2010;214 (1):54–60. [10] Chang H, Shang M, Zhang C, Yuan H, Feng S. J Am Ceram Soc 2012;95 (11):3673–7. [11] Kong X, Hu D, Wen P, Ishii T, Tanaka Y, Feng Q. Dalton Trans 2013;42 (21):7699–709. [12] Li G, Yan S, Wang Z, Wang X, Li Z, Ye J, et al. Dalton Trans 2009;40:8519–24. [13] Li Y, Shen W. Chem Soc Rev 2014;43(5):1543–74.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Topotactic soft chemical synthesis and photocatalytic performance of one-dimensional AgNbO3 nanostructures Liyun Cao a, Zhanglin Guo a, Jianfeng Huang a, Cuiyan Li a, Jie Fei a, Qi Feng b, Puhong Wen c, Youquan Sun d, Xingang Kong a,d,n a
School of Materials Science and Engineering, Shaanxi University of Science and Technology, Weiyang, Xi'an, Shaanxi 710021, PR China Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu-shi 761-0396, Japan c Department of Chemistry and Chemical Engineering, Baoji University of Arts and Science, 1 Gaoxin Road, Baoji, Shaanxi 721013, PR China d Anhui Deli Household Glass Co., Ltd., Fengyang Gate Taiwan Industrial Park, Anhui 223121, PR China b
art ic l e i nf o
a b s t r a c t
Article history: Received 4 July 2014 Accepted 28 August 2014 Available online 6 September 2014
A topotactic soft chemical process was used for the synthesis of one-dimensional AgNbO3 nanostructures. Firstly, using a tunnel structure potassium niobate K2Nb2O6 nH2O filiform crystal as precursor, the K þ in K2Nb2O6 nH2O were exchanged by an Ag þ in the AgNO3 water solution, forming Ag þ ionexchanged sample. Secondly, the Ag þ ion-exchanged sample was heat-treated to obtain the perovskite AgNbO3 by in situ topotactic structural transformation reaction. The one-dimensional nanostructured AgNbO3 was characterized by XRD, FE-SEM, TEM, SAED, EDS and UV–vis diffuse reflectance spectra. The one-dimensional AgNbO3 nanostructures were constructed from nanocrystals arranged along [011]crystal axis and with predominantly exposed (100) facet. The samples were able to degrade MB under ultraviolet irradiation and catalyze water-splitting in aqueous solution under illumination of visible light. Crown Copyright & 2014 Published by Elsevier B.V. All rights reserved.
Keywords: In situ topotactic AgNbO3 One-dimensional Semiconductors Microstructure Nanocrystalline materials
1. Introduction The soft chemical process is a useful method for the preparation of particles with controlled morphology, grain size, chemical composition, and nanostructure [1–3]. The process typically comprises two steps: the first step is the preparation of a framework precursor, and the second step is the structural transformation of the template precursor into a desired structure. Since the structural transformation in the soft chemical process is an in situ topotactic structural transformation reaction, the morphology of the precursor can be retained after the reaction. This in situ topotactic structural transformation has been widely used in synthesizing various kinds of materials with special structures and morphologies, such as plate like Ba0.5(Bi0.5K0.5)0.5TiO3 nanostructures [2], tunnel structured manganese oxide [3], and mixed layered Ni(OH)2–manganese oxides [4]. Therefore layered or tunnel structured compounds, because of their ion-exchange property, are suitable as precursors for synthesizing and designing the photocatalytic materials [5,6].
n Corresponding author at: School of Materials Science and Engineering, Shaanxi University of Science and Technology, Weiyang, Xi'an, Shaanxi 710021, PR China. Tel./fax: þ 86 29 86168802. E-mail address: [email protected] (X. Kong).
http://dx.doi.org/10.1016/j.matlet.2014.08.150 0167-577X/Crown Copyright & 2014 Published by Elsevier B.V. All rights reserved.
Recently, photocatalytic performance of AgNbO3 was abundantly reported [7–10]. The photocatalytic reaction and efficiency are closely related to the morphology and micro-structure of the material because photocatalytic actions are typically surface-based processes. However the AgNbO3 particles obtained by normal methods, such as solid-state reaction [7], the sol–gel method [8], molten-salt method [9] and solvothermal method [10], usually have cubic or irregular morphologies. Through these traditional methods it is difficult to simultaneously control chemical composition, grain size, morphology and nanostructure of product particles. In this paper, therefore, we describe a soft chemical synthesis of one-dimensional AgNbO3 nanostructures from the tunnel structure K2Nb2O6 nH2O filiform crystal. And the sample's photocatalytic performances were investigated by decomposing the dye MB and evolving O2 via water splitting.
2. Experimental 0.5 g of tunnel structured K2Nb2O6 nH2O fibrous crystal [11] was put into a 0.5 mol L 1 AgNO3 water solution, and then stirred and ion-exchanged for 24 h at room temperature. The ionexchange was performed twice for K þ of the K2Nb2O6 nH2O to be exchanged completely with Ag þ . After ion-exchange, the products were filtered, washed with distilled water, and dried at
L. Cao et al. / Materials Letters 137 (2014) 110–112
room temperature. The Ag þ -exchanged samples were obtained. Finally, the Ag þ -exchanged sample was heat-treated at 500 1C for 2 h to obtain the perovskite structured one-dimensional AgNbO3 nanostructures. The products were analyzed by XRD (D/max-2200) using CuKα radiation (λ ¼0.154 nm). The morphology study and characterization of the products were performed by FE-SEM (Hitachi S-4800) and TEM (FEI Tecnai G2 F20). UV–vis absorption spectra were recorded on a UV/vis/NIR spectrophotometer (LAMBDA950, PerkinElmer).The photocatalytic activities of samples were evaluated by degradation of methylene blue (MB) under xenon lamp and mercury lamp irradiation. 50 mg of AgNbO3 sample was added into the solution (50 mL, 10 mg L 1). The suspensions were magnetically stirred in dark for 40 min to ensure the establishment of an adsorption–desorption equilibrium. Then, the solution was exposed to the lamp irradiation. The concentrations of the remnant dye in the collected solution were monitored by UV–vis spectroscopy (Unico UV-2600) each for 10 min. The photocatalytic O2 evolution experiments were performed in a 300 mL quartz reactor at ambient temperature. The reactor was connected to a closed circulating system. A PLSSXE 300UV Xe arc lamp with a UV-cutoff filter (4400 nm) was used. 0.1 g of photocatalyst powder was dispersed in 100 mL of 0.05 mol L 1 AgNO3 solution. The O2 evolution was detected by gas chromatography (Shimadzu GC-8A).
3. Result and discussion In the previous study [11] we have reported the synthesis of a tunnel structure niobate K2Nb2O6 nH2O which is composed of NbO6 and KO6 octahedrons with the remaining K þ occupying the tunnel sites, and is a single particle with fiber-like morphology. Fig. 1a shows the XRD patterns of samples of K2Nb2O6 nH2O precursor. It was found that the precursor K2Nb2O6 nH2O possessed a characteristic peak of tunnel structure near 2θ ¼101 and fine crystallinity. After the K2Nb2O6 nH2O precursor was ionexchanged with Ag þ ion in the 0.5 mol L 1 AgNO3 water solution the Ag þ -exchanged sample retained the tunnel structure, though its characteristic peak widened (Fig. 1b). The chemical composition analysis result reveals that no K component is detected, and the mole ratio of Ag and Nb is 0.99/1, which is not consistent with our report that the K þ ions in the K2Nb2O6 precursor cannot be completely exchanged with the Li þ in LiCl water solution [11]. The reason was that AgNO3 water solution presented acidity,
111
whereas the KO6 octahedral layers in the tunnel structural framework were not steady and were easily dissolved in the acid environment [11]. Thus, the K þ ions in the KO6 octahedral layers were dissolved out. According to the TG–DTA analysis of the Ag þ -exchanged sample we found that it had an exothermic peak at 500 1C, which indicates the existence of a phase transition. Fig. 1c shows the XRD patterns of samples obtained by heat-treating the Ag þ -exchanged sample at 500 1C for 2 h. It was found that a pure orthorhombic AgNbO3 phase (JCPDS No. 22-0471) was formed after the heattreatment of the Ag þ -exchanged sample. The chemical composition analysis indicated that the mole ratio of Ag to Nb was the same in samples before and after the heat-treatment. The Ag þ -exchanged sample showed a fiber-like morphology with the size of about 2 μm in width and 50 μm in length, which was the same as that of K2Nb2O6 nH2O precursor (Fig. 2). The obtained AgNbO3 sample still retained the fiber-like morphology, and its size almost had no change compared with that of the precursors. These results suggested that in situ topotactic transition reaction occurred from the tunnel structure K2Nb2O6 nH2O to the perovskite AgNbO3. The size and morphology of the AgNbO3 sample were dependent on those of the precursor. Similar to AgNbO3 sample's SEM images the TEM images of AgNbO3 sample also presented filaments that were constructed from nanocrystals (Fig. 2d), meaning one-dimensional nanostructures. It is very interesting that the SAED pattern of the AgNbO3 one-dimensional nanostructures shows one set of diffraction spots similar to those of a single crystal, which correspond to the (100) and (011) planes of the perovskite structured AgNbO3. This result suggests that all the AgNbO3 nanoparticles in one-dimensional nanostructures have the same crystal-axis orientation, and all the AgNbO3 nanoparticles grow along the [011]-crystal-axis. These one-dimensional nanostructures predominately exposed the (100) facet. Fig. 3a shows the UV–vis diffuse reflectance spectra of onedimensional AgNbO3 nanostructures. It was seen that the AgNbO3 sample displayed the absorption edges in the ultraviolet light region of 300–400 nm, same as that of the AgNbO3 samples reported in the literature [12]. In the visible light region of 550– 650 nm, however, our AgNbO3 sample presented a stronger absorption than that of the literature [12], and dark gray color (Fig. 3b). The photocatalytic performance of the AgNbO3 onedimensional nanostructures was evaluated by degradation of 10 mol L 1 MB solution under xenon lamp and mercury lamp irradiation. As shown in the Fig. 3c, the AgNbO3 sample reached the degradation efficiency of 98.8% for MB after UV-irradiation for 30 min. The degradation efficiency for MB is only 24.4% under visible light irradiation for 30 min which is less than that of the reported literature (MB degradation efficiency of 85%) [8]. In the visible light photocatalytic O2 evolution experiments, however, the O2 evolution quantity was about 27 μmol h 1, higher than that 14 μmol h 1 of AgNbO3 sample prepared by conventional solidstate reactions [7]. This may be attributed to the fact that AgNbO3 nanocrystal with exposed (100) facet in one-dimensional nanostructures is generally beneficial for surface-based photocatalysed water splitting. The exposed (100) facet may provide more reaction sites [13]. Here, the detailed photocatalytic mechanism of the one-dimensional AgNbO3 nanostructures is not discussed.
4. Conclusions
Fig. 1. XRD patterns of K2Nb2O6 nH2O precursor (a), Ag þ -exchanged sample (b), and the sample obtained by heat-treating Ag þ -exchanged sample (c).
Perovskite one-dimensional AgNbO3 nanostructures were successfully synthesized by in situ topotactic transition reaction. Results show that one-dimensional nanostructures were constructed
112
L. Cao et al. / Materials Letters 137 (2014) 110–112
Fig. 2. FE-SEM (a)–(c) and TEM (d) images of samples. K2Nb2O6 nH2O precursor (a), Ag þ -exchanged sample (b) and AgNbO3 sample (c, d).
Acknowledgments The authors acknowledgment the support of Natural Science Basic Research Plan in Shaanxi Province of China (Program No. 2013JQ6012), China Postdoctoral Science Foundation (Program No. 2013M542314), the Research Starting Foundation from Shaanxi University of Science and Technology (BJ12-22), and Innovation Team Assistance Foundation of Shaanxi Province (Grant No. 2013KCT-06).
References
Fig. 3. UV–visible diffuse reflectance spectra (a), color photo (b) and photocatalytic degradation for MB results (c) of AgNbO3 nanostructures. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
from AgNbO3 nanocrystals arranged along the [011]-crystal axis. The samples were found to be capable of photodegrading MB and the photodegradation rate reached 98.8% after 30 min under ultraviolet irradiation. The O2 evolution by water-splitting with sacrificial reagents under visible light irradiation of the onedimensional nanostructures was about 27 μmol h 1. It is believed that other new types of functional niobates may also be obtained by the topotactic soft chemical process.
[1] Feng Q, Hirasawa M, Kajiyoshi K, Yanagisawa K. J Am Ceram Soc 2005;88 (6):1415–20. [2] Kong X, Hu D, Ishikawa Y, Tanaka Y, Feng Q. Chem Mater 2011;23 (17):3978–86. [3] Feng Q, Yanagawa K, Yamasaki N. J Porous Mater 1998;5(2):153–62. [4] Xu Y, Feng Q, Kajiyoshi K, Yanagisawa K, Yang X, Makita Y, et al. Chem Mater 2002;14(9):3844–51. [5] Li L, Deng J, Chen J, Sun X, Yu R, Liu G, et al. Chem Mater 2009;21(7):1207–13. [6] Sayama K, Tanaka A, Domen K, Maruya K, Onishi T. J Phys Chem 1991;95 (3):1345–8. [7] Kato H, Kobayashi H, Kudo A. J Phys Chem B 2002;106(48):12441–7. [8] Wu W, Liang S, Chen Y, Shen L, Yuan R, Wu L. Mater Res Bull 2013;48 (4):1618–26. [9] Arney D, Hardy C, Greve B, Maggard PA. J Photochem Photobiol A 2010;214 (1):54–60. [10] Chang H, Shang M, Zhang C, Yuan H, Feng S. J Am Ceram Soc 2012;95 (11):3673–7. [11] Kong X, Hu D, Wen P, Ishii T, Tanaka Y, Feng Q. Dalton Trans 2013;42 (21):7699–709. [12] Li G, Yan S, Wang Z, Wang X, Li Z, Ye J, et al. Dalton Trans 2009;40:8519–24. [13] Li Y, Shen W. Chem Soc Rev 2014;43(5):1543–74.