- Email: [email protected]
shell MoS2 microspheres
Author’s Accepted Manuscript Ionic liquid assisted Hydrothermal synthesis of hollow core/shell MoS2 microspheres Jiahe Li, Donge Wang, Huaijun Ma, Zhendong Pan, Yuxia Jiang, Min Li, Zhijian Tian www.elsevier.com
PII: DOI: Reference:
S0167-577X(15)30406-7 http://dx.doi.org/10.1016/j.matlet.2015.08.049 MLBLUE19410
To appear in: Materials Letters Received date: 29 May 2015 Accepted date: 9 August 2015 Cite this article as: Jiahe Li, Donge Wang, Huaijun Ma, Zhendong Pan, Yuxia Jiang, Min Li and Zhijian Tian, Ionic liquid assisted Hydrothermal synthesis of hollow core/shell MoS2 microspheres, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2015.08.049 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Ionic liquid assisted hydrothermal synthesis of hollow core/shell MoS2 microspheres Jiahe Lia,b, Donge Wanga, Huaijun Maa, Zhendong Pana, Yuxia Jianga,b, Min Lia,b, Zhijian Tiana,c,* a
Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy
of Sciences, Dalian 116023, China b
University of Chinese Academy of Sciences, Beijing 100049, China
c
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences,
Dalian 116023, China * Corresponding author: Tel: 86-411-84379151, Fax: 86-411-84379151 Email address: [email protected] Abstract Hollow core/shell MoS2 microspheres were successfully hydrothermally synthesized by adding an ionic liquid 1-ethyl-3-methylimidazolium bromide ([EMIM] Br) as additive. The obtained MoS2 products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). MoS2 microspheres have uniform morphology with the mean diameter of 2.5 μm and the shell thickness of about 0.8 μm. The surfaces of the hollow core/shell MoS2 microspheres are constructed by MoS2 nanosheets. Ionic liquids play an important role in the formation of hollow core/shell MoS2 microspheres. MoS2 microspheres with double-shell structure can be acquired by increasing the dosage of ionic liquid. A soft template mechanism of the hollow core/shell structure is proposed. Keyword: ionic liquids (ILs); MoS2 microspheres; hollow core/shell; microstructure; surfaces; multilayer structure 1. Introduction For the last few decades, transition metal chalcogenides, especially molybdenum sulfide (MoS2), have attracted much attention, due to their unique electronic property, optical property, mechanical property and layer structure [1]. To date, considerable efforts have been made to synthesize nano/micro MoS2 materials with different morphologies such as nanospheres[2,3], nanoflowers[4,5], nanorods[6,7], inorganic fullerene-like structure[8,9] etc.. To obtain various morphologies, many synthesis methods, including solide-gas sulfidation of the oxides, intercalation, exfoliation and restacking, precursor decomposition,
1
solution reactions, et al., have been reported[10]. Among various synthetic methods, the hydrothermal process is preferred by many researchers because of its advantages such as simple operation, mild conditions and good crystallinity of obtained products. Hollow inorganic micro- and nano-structures have many unique characteristics such as internal void space, low density, high surface-to-volume ratio, and low coefficients of thermal expansion and refractive index et al. [11,12]. Compared to the single-component hollow structures, core-shell particles often exhibit improved physical and chemical properties, and hence can be potentially used in more fields. Recently, the utilization of ionic liquids (ILs) in inorganic synthesis is a new direction in material chemistry. As a new reaction medium and template, ILs are nonvolatile, thermally stable, and its solubility is tunable for both water and common organic solvents[13]. By screening suitable ILs, many novel nano- or micro-structured materials have been prepared. Flower-like MoS2 microspheres [14,15] and hollow MoS2 microspheres[16,17] were respectively prepared by adding [BMIM][BF4], [BMIM][PF6] and [BMIM]Cl. However, to the best of our knowledge, there is no report on the preparation of hollow core/shell MoS2 microspheres using ILs. In this paper, we report a simple hydrothermal method to synthesize uniform hollow core/shell MoS2 microspheres by adding an ionic liquid [EMIM] Br. A soft template mechanism is presented for the formation of the hollow core/shell MoS2 microspheres. 2. Experimental 2.1. IL-assisted hydrothermal synthesis of MoS2 microspheres All chemicals were analytical reagents and used without further purification. In a typical process, 3 mmol of sodium molybdate and 9 mmol of CH3CSNH2 (TAA) were dissolved in 30 ml deionized water, and then an appropriate amount of [EMIM] Br was added into the above solution under continuous stirring. Hydrochloric acid was added into the above solution to adjust pH value to 5. The resulting solution was transferred into a 100 ml Teflon-lined stainless steel autoclave, and then the autoclave was sealed tightly. Hydrothermal reaction was carried out at 200 °C for 24 h. After that, the autoclave was allowed to cool down to room temperature naturally. The black precipitates were collected, washed with deionized water and absolute ethanol, and finally dried at 70 °C overnight in a vacuum oven. Finally the as-synthesized MoS2 samples were calcined at 400 °C for 2 h in the tube furnace in N2 atmosphere.
2
2.2. Characterizations of MoS2 microspheres XRD analysis of the obtained samples was performed on a PANalytical X’Pert PRO diffractometer fitted with a CuKα radiation source (λ=1.5418Å) operating at 40 mA and 40 kV. The morphologies and particle sizes were examined by a Phenom scanning electron microscope (FEI Electron Optics) and an FEI Quanta 200F field emission scanning electron microscope (FESEM). 3. Results and discussions Fig.1a shows XRD patterns of MoS2 hollow core/shell samples. The XRD pattern of as-synthesized MoS2 sample shows (002) diffraction peak at 2θ =9.45° corresponding to the interlayer distance of 9.36Å. Compared with the standard powder diffraction file of MoS2 (JCPDS No. 37-1492), the shift of (002) diffraction peak to lower angle indicates a substantial increase of interlayer distance. This phenomenon is similar to the results reported by Li et al.[17]. According to their analysis, the ILs located at inter-layers result in enlarging the interlayer distance. After calcination, all the diffraction peaks moved to higher angle and they can be assigned to hexagonal 2H MoS2 (JCPDS No. 37-1492). The reason for this shift probably is that the ILs were totally removed after the calcination, therefore, the interlayer distance returned to the standard values.
Fig.1
3
The sizes and morphologies of the as-synthesized MoS2 samples were studied by FESEM, as shown in Figure 1b-e. SEM images with lower magnifications in Fig. 1b and c show that the as-synthesized MoS2 sample is composed of uniform microspheres with average diameter of 2.5 μm. As is shown in Fig. 1d and e, MoS2 microspheres have hollow core/shell structure with shell thickness of about 0.8 μm, and the surface of MoS2 sample is constructed by nanosheets. According to the chemical reaction, it is believed that MoS2 is formed by an oxidation-reduction process and sulfurization reagents TAA also serve as reductant. The reaction process can be expressed as follows: CH3CSNH2 + 2H2O → H2S + CH3COOH + NH3 4Na2MoO4 + 9H2S + 6HCl → 4MoS2 + Na2SO4 + 6NaCl + 12H2O Fig.2 shows the SEM images of the MoS2 products obtained by adding different amounts of ILs. When no ILs were added to the reaction system, the obtained MoS2 particles are irregular, and large aggregates can be observed in the products (Fig.2a). After adding 0.3 g ILs, the as-synthesized MoS2 product is composed of uniform sphere-like particles with hollow core/shell structure (Fig.1b-e, Fig.2b). With the amount of the ILs rising up to 0.5 g, the particle sizes of MoS2 products become slightly larger and the thickness of the shell increases obviously (Fig.2c). By further increasing IL dosage to 1 g, MoS2 sample with double-shell structure can be acquired, as is seen in Fig.2d. In conclusion, the additives ILs were essential for the formation of the hollow core/shell structure.
Fig.2
4
In order to elucidate the growth mechanism of MoS2 hollow core/shell structure, a series of time-dependent experiments were performed. Fig.3 demonstrates the morphologies of MoS2 samples obtained by different hydrothermal times. As is shown in Fig.3a, solid spheres with smooth surfaces were obtained by hydrothermal treatment for 6 h. The arrangement of products became looser, and rather rough surfaces appeared for the MoS2 sample with increasing hydrothermal time to 12 h (Fig.3b). When the reaction time was increased to 18 h, occasional core/shell structures can be observed (Fig.3c). By further increasing the reaction time to 24h, the uniform hollow core/shell MoS 2 microspheres were finally generated, as is shown in Fig.3d.
Fig.3 Based on the results of the time-dependent experiments, a soft template mechanism of the MoS2 hollow core/shell structures is proposed as illustrated in Fig.4a. Firstly, thiomolybdate precursors were formed by the reaction of sodium molybdate and TAA in the deionized water. [EMIM]+ cations ionized from [EMIM] Br ILs absorbed to the surface of thiomolybdate precursors due to the electrostatic interaction. Then another layer of thiomolybdate precursors covered the [EMIM]+ cation layer at an appropriate concentration. The thiomolybdate precursor is ( Mo3 ( S2 ) 6S )2- by analyzing the XRD pattern (not shown here) of product of hydrothermal treatment for 6 h. Afterwards, thiomolybdate precursors gradually decomposed into MoS2 nanosheets, which arranged relatively loosely and allowed [EMIM]+ cations to permeate into the solution. This process is consistent with the SEM results of the hydrothermal treatment for 12 h and 18 h ( Fig.3b and 3c ). Finally, hollow core/shell MoS2 microspheres with uniform
5
size and morphology can be formed when the crystallization time prolongs to 24 h. If the amounts of ILs are further increased, the [EMIM]+ cations and thiomolybdate precursors would assemble layer by layer in a similar way and finally form double-shell MoS2 microspheres in the following hydrothermal reaction, as described in Fig.4b. This speculation can be proved by SEM image of MoS2 product synthesized with 1 g [EMIM]Br (Fig.2d) . Therefore, it is believed that a self-assembly mechanism of [EMIM]+ cations and thiomolybdate precursors is responsible for the formation of the hollow core/shell MoS2 microspheres. A similar mechanism has been reported by Liu et al.[18] who synthesized novel β-MoO3 and WO3 hollow nanospheres with core–shell–corona architecture using a soft template of polymeric micelle.
Fig.4 4. Conclusions Hollow core/shell MoS2 microspheres with average diameter of 2.5 μm and the shell thickness of about 0.8 μm were successfully hydrothermally synthesized by adding an ionic liquid [EMIM] Br as additive. MoS2 microspheres with double-shell structure can be acquired by increasing ionic liquids’ dosage. A soft template mechanism is proposed to explain the formation of hollow core/shell MoS 2 microspheres. The hollow core/shell MoS2 materials synthesized here may have a potential application in lithium-ion batteries, and the synthesis method may also be used to synthesis other transition metal sulfide materials. Acknowledgement This work was financially supported by the National Science Foundation of China (Grant No. 21373214). References [1]. Chhowalla M, Shin HS, Eda G, Li L-J, Loh KP, Zhang H. Nature Chem 2013; 5: 263-275. [2]. Wu Z, Wang D, Sun A. J Mater Sci 2009;45(1): 182-187. [3]. Tian Y, Zhao X, Shen L, Meng F, Tang L, Deng Y, et al. Mater Lett 2006;60(4): 527-529.
6
[4]. Ma L, Xu L-M, Zhou X-P, Xu X-Y. Mater Lett 2014;132: 291-294. [5]. Sheng B, Liu J, Li Z, Wang M, Zhu K, Qiu J, et al. Mater Lett 2015; 144: 153-156. [6]. Lin H, Chen X, Li H, Yang M, Qi Y. Mater Lett 2010; 64(15): 1748-1750. [7]. Tian Y, Zhao J, Fu W, Liu Y, Zhu Y, Wang Z. Mater Lett 2005;59(27): 3452-3455. [8]. Du K, Fu W, Wei R, Yang H, Liu S, Yu S, et al. Mater Lett 2007;61(27): 4887-4889. [9]. Li XL, Li YD. Chem 2003;9(12): 2726-31. [10]. Afanasiev P. Comptes Rendus Chimie 2008;11: 159-82. [11]. Lou XW, Archer LA, Yang Z. Adv Mater 2008;20: 3987-4019. [12]. Lai X, Halpert JE, Wang D. Energ Environ Sci 2012;5(2): 5604. [13]. Ma Z, Yu J, Dai S. Adv Mater 2010;22(2): 261-85. [14]. Ma L, Chen W-X, Li H, Zheng Y-F, Xu Z-D. Mater Lett 2008;62(6-7): 797-799. [15]. Ma L, Chen W-X, Li H, Xu Z-D. Mater Chem Phys 2009;116(2-3): 400-405. [16]. Luo H, Xu C, Zou D, Wang L, Ying T. Mater Lett 2008;62(20): 3558-3560. [17]. Li N, Chai Y, Li Y, Tang Z, Dong B, Liu Y, et al. Mater Lett 2012;66(1): 236-238. [18]. Liu J, Sasidharan M, Liu D, Yokoyama Y, Yusa S-i, Nakashima K. Mater Lett 2012;66 (1): 25-28.
Figure Captions Fig.1. (a) XRD patterns of the as-synthesized and calcined MoS2 samples. (b-e) SEM images of the as-synthesized MoS2 hollow core/shell microspheres. Fig.2. SEM images of the MoS2 microspheres obtained via a hydrothermal route by adding different amounts of ILs: (a) 0 g, (b) 0.3 g, (c) 0.5 g and (d) 1 g. Fig.3. SEM images of the MoS2 microspheres synthesized with 0.3g ILs for different hydrothermal times: (a) 6 h, (b) 12 h, (c) 18 h and (d) 24 h. Fig.4. (a) Illustration of the growth mechanism of MoS2 hollow core/shell microspheres; (b) Illustration of the growth mechanism of MoS2 double-shell microspheres.
Highlights
Hollow core/shell MoS2 microspheres were hydrothermally synthesized
Ionic liquids are important for the formation of hollow core/shell structure
Double-shell structure can be acquired by increasing ionic liquids’ dosage
A soft template mechanism of the hollow core/shell structure is proposed
7
PII: DOI: Reference:
S0167-577X(15)30406-7 http://dx.doi.org/10.1016/j.matlet.2015.08.049 MLBLUE19410
To appear in: Materials Letters Received date: 29 May 2015 Accepted date: 9 August 2015 Cite this article as: Jiahe Li, Donge Wang, Huaijun Ma, Zhendong Pan, Yuxia Jiang, Min Li and Zhijian Tian, Ionic liquid assisted Hydrothermal synthesis of hollow core/shell MoS2 microspheres, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2015.08.049 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Ionic liquid assisted hydrothermal synthesis of hollow core/shell MoS2 microspheres Jiahe Lia,b, Donge Wanga, Huaijun Maa, Zhendong Pana, Yuxia Jianga,b, Min Lia,b, Zhijian Tiana,c,* a
Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy
of Sciences, Dalian 116023, China b
University of Chinese Academy of Sciences, Beijing 100049, China
c
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences,
Dalian 116023, China * Corresponding author: Tel: 86-411-84379151, Fax: 86-411-84379151 Email address: [email protected] Abstract Hollow core/shell MoS2 microspheres were successfully hydrothermally synthesized by adding an ionic liquid 1-ethyl-3-methylimidazolium bromide ([EMIM] Br) as additive. The obtained MoS2 products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). MoS2 microspheres have uniform morphology with the mean diameter of 2.5 μm and the shell thickness of about 0.8 μm. The surfaces of the hollow core/shell MoS2 microspheres are constructed by MoS2 nanosheets. Ionic liquids play an important role in the formation of hollow core/shell MoS2 microspheres. MoS2 microspheres with double-shell structure can be acquired by increasing the dosage of ionic liquid. A soft template mechanism of the hollow core/shell structure is proposed. Keyword: ionic liquids (ILs); MoS2 microspheres; hollow core/shell; microstructure; surfaces; multilayer structure 1. Introduction For the last few decades, transition metal chalcogenides, especially molybdenum sulfide (MoS2), have attracted much attention, due to their unique electronic property, optical property, mechanical property and layer structure [1]. To date, considerable efforts have been made to synthesize nano/micro MoS2 materials with different morphologies such as nanospheres[2,3], nanoflowers[4,5], nanorods[6,7], inorganic fullerene-like structure[8,9] etc.. To obtain various morphologies, many synthesis methods, including solide-gas sulfidation of the oxides, intercalation, exfoliation and restacking, precursor decomposition,
1
solution reactions, et al., have been reported[10]. Among various synthetic methods, the hydrothermal process is preferred by many researchers because of its advantages such as simple operation, mild conditions and good crystallinity of obtained products. Hollow inorganic micro- and nano-structures have many unique characteristics such as internal void space, low density, high surface-to-volume ratio, and low coefficients of thermal expansion and refractive index et al. [11,12]. Compared to the single-component hollow structures, core-shell particles often exhibit improved physical and chemical properties, and hence can be potentially used in more fields. Recently, the utilization of ionic liquids (ILs) in inorganic synthesis is a new direction in material chemistry. As a new reaction medium and template, ILs are nonvolatile, thermally stable, and its solubility is tunable for both water and common organic solvents[13]. By screening suitable ILs, many novel nano- or micro-structured materials have been prepared. Flower-like MoS2 microspheres [14,15] and hollow MoS2 microspheres[16,17] were respectively prepared by adding [BMIM][BF4], [BMIM][PF6] and [BMIM]Cl. However, to the best of our knowledge, there is no report on the preparation of hollow core/shell MoS2 microspheres using ILs. In this paper, we report a simple hydrothermal method to synthesize uniform hollow core/shell MoS2 microspheres by adding an ionic liquid [EMIM] Br. A soft template mechanism is presented for the formation of the hollow core/shell MoS2 microspheres. 2. Experimental 2.1. IL-assisted hydrothermal synthesis of MoS2 microspheres All chemicals were analytical reagents and used without further purification. In a typical process, 3 mmol of sodium molybdate and 9 mmol of CH3CSNH2 (TAA) were dissolved in 30 ml deionized water, and then an appropriate amount of [EMIM] Br was added into the above solution under continuous stirring. Hydrochloric acid was added into the above solution to adjust pH value to 5. The resulting solution was transferred into a 100 ml Teflon-lined stainless steel autoclave, and then the autoclave was sealed tightly. Hydrothermal reaction was carried out at 200 °C for 24 h. After that, the autoclave was allowed to cool down to room temperature naturally. The black precipitates were collected, washed with deionized water and absolute ethanol, and finally dried at 70 °C overnight in a vacuum oven. Finally the as-synthesized MoS2 samples were calcined at 400 °C for 2 h in the tube furnace in N2 atmosphere.
2
2.2. Characterizations of MoS2 microspheres XRD analysis of the obtained samples was performed on a PANalytical X’Pert PRO diffractometer fitted with a CuKα radiation source (λ=1.5418Å) operating at 40 mA and 40 kV. The morphologies and particle sizes were examined by a Phenom scanning electron microscope (FEI Electron Optics) and an FEI Quanta 200F field emission scanning electron microscope (FESEM). 3. Results and discussions Fig.1a shows XRD patterns of MoS2 hollow core/shell samples. The XRD pattern of as-synthesized MoS2 sample shows (002) diffraction peak at 2θ =9.45° corresponding to the interlayer distance of 9.36Å. Compared with the standard powder diffraction file of MoS2 (JCPDS No. 37-1492), the shift of (002) diffraction peak to lower angle indicates a substantial increase of interlayer distance. This phenomenon is similar to the results reported by Li et al.[17]. According to their analysis, the ILs located at inter-layers result in enlarging the interlayer distance. After calcination, all the diffraction peaks moved to higher angle and they can be assigned to hexagonal 2H MoS2 (JCPDS No. 37-1492). The reason for this shift probably is that the ILs were totally removed after the calcination, therefore, the interlayer distance returned to the standard values.
Fig.1
3
The sizes and morphologies of the as-synthesized MoS2 samples were studied by FESEM, as shown in Figure 1b-e. SEM images with lower magnifications in Fig. 1b and c show that the as-synthesized MoS2 sample is composed of uniform microspheres with average diameter of 2.5 μm. As is shown in Fig. 1d and e, MoS2 microspheres have hollow core/shell structure with shell thickness of about 0.8 μm, and the surface of MoS2 sample is constructed by nanosheets. According to the chemical reaction, it is believed that MoS2 is formed by an oxidation-reduction process and sulfurization reagents TAA also serve as reductant. The reaction process can be expressed as follows: CH3CSNH2 + 2H2O → H2S + CH3COOH + NH3 4Na2MoO4 + 9H2S + 6HCl → 4MoS2 + Na2SO4 + 6NaCl + 12H2O Fig.2 shows the SEM images of the MoS2 products obtained by adding different amounts of ILs. When no ILs were added to the reaction system, the obtained MoS2 particles are irregular, and large aggregates can be observed in the products (Fig.2a). After adding 0.3 g ILs, the as-synthesized MoS2 product is composed of uniform sphere-like particles with hollow core/shell structure (Fig.1b-e, Fig.2b). With the amount of the ILs rising up to 0.5 g, the particle sizes of MoS2 products become slightly larger and the thickness of the shell increases obviously (Fig.2c). By further increasing IL dosage to 1 g, MoS2 sample with double-shell structure can be acquired, as is seen in Fig.2d. In conclusion, the additives ILs were essential for the formation of the hollow core/shell structure.
Fig.2
4
In order to elucidate the growth mechanism of MoS2 hollow core/shell structure, a series of time-dependent experiments were performed. Fig.3 demonstrates the morphologies of MoS2 samples obtained by different hydrothermal times. As is shown in Fig.3a, solid spheres with smooth surfaces were obtained by hydrothermal treatment for 6 h. The arrangement of products became looser, and rather rough surfaces appeared for the MoS2 sample with increasing hydrothermal time to 12 h (Fig.3b). When the reaction time was increased to 18 h, occasional core/shell structures can be observed (Fig.3c). By further increasing the reaction time to 24h, the uniform hollow core/shell MoS 2 microspheres were finally generated, as is shown in Fig.3d.
Fig.3 Based on the results of the time-dependent experiments, a soft template mechanism of the MoS2 hollow core/shell structures is proposed as illustrated in Fig.4a. Firstly, thiomolybdate precursors were formed by the reaction of sodium molybdate and TAA in the deionized water. [EMIM]+ cations ionized from [EMIM] Br ILs absorbed to the surface of thiomolybdate precursors due to the electrostatic interaction. Then another layer of thiomolybdate precursors covered the [EMIM]+ cation layer at an appropriate concentration. The thiomolybdate precursor is ( Mo3 ( S2 ) 6S )2- by analyzing the XRD pattern (not shown here) of product of hydrothermal treatment for 6 h. Afterwards, thiomolybdate precursors gradually decomposed into MoS2 nanosheets, which arranged relatively loosely and allowed [EMIM]+ cations to permeate into the solution. This process is consistent with the SEM results of the hydrothermal treatment for 12 h and 18 h ( Fig.3b and 3c ). Finally, hollow core/shell MoS2 microspheres with uniform
5
size and morphology can be formed when the crystallization time prolongs to 24 h. If the amounts of ILs are further increased, the [EMIM]+ cations and thiomolybdate precursors would assemble layer by layer in a similar way and finally form double-shell MoS2 microspheres in the following hydrothermal reaction, as described in Fig.4b. This speculation can be proved by SEM image of MoS2 product synthesized with 1 g [EMIM]Br (Fig.2d) . Therefore, it is believed that a self-assembly mechanism of [EMIM]+ cations and thiomolybdate precursors is responsible for the formation of the hollow core/shell MoS2 microspheres. A similar mechanism has been reported by Liu et al.[18] who synthesized novel β-MoO3 and WO3 hollow nanospheres with core–shell–corona architecture using a soft template of polymeric micelle.
Fig.4 4. Conclusions Hollow core/shell MoS2 microspheres with average diameter of 2.5 μm and the shell thickness of about 0.8 μm were successfully hydrothermally synthesized by adding an ionic liquid [EMIM] Br as additive. MoS2 microspheres with double-shell structure can be acquired by increasing ionic liquids’ dosage. A soft template mechanism is proposed to explain the formation of hollow core/shell MoS 2 microspheres. The hollow core/shell MoS2 materials synthesized here may have a potential application in lithium-ion batteries, and the synthesis method may also be used to synthesis other transition metal sulfide materials. Acknowledgement This work was financially supported by the National Science Foundation of China (Grant No. 21373214). References [1]. Chhowalla M, Shin HS, Eda G, Li L-J, Loh KP, Zhang H. Nature Chem 2013; 5: 263-275. [2]. Wu Z, Wang D, Sun A. J Mater Sci 2009;45(1): 182-187. [3]. Tian Y, Zhao X, Shen L, Meng F, Tang L, Deng Y, et al. Mater Lett 2006;60(4): 527-529.
6
[4]. Ma L, Xu L-M, Zhou X-P, Xu X-Y. Mater Lett 2014;132: 291-294. [5]. Sheng B, Liu J, Li Z, Wang M, Zhu K, Qiu J, et al. Mater Lett 2015; 144: 153-156. [6]. Lin H, Chen X, Li H, Yang M, Qi Y. Mater Lett 2010; 64(15): 1748-1750. [7]. Tian Y, Zhao J, Fu W, Liu Y, Zhu Y, Wang Z. Mater Lett 2005;59(27): 3452-3455. [8]. Du K, Fu W, Wei R, Yang H, Liu S, Yu S, et al. Mater Lett 2007;61(27): 4887-4889. [9]. Li XL, Li YD. Chem 2003;9(12): 2726-31. [10]. Afanasiev P. Comptes Rendus Chimie 2008;11: 159-82. [11]. Lou XW, Archer LA, Yang Z. Adv Mater 2008;20: 3987-4019. [12]. Lai X, Halpert JE, Wang D. Energ Environ Sci 2012;5(2): 5604. [13]. Ma Z, Yu J, Dai S. Adv Mater 2010;22(2): 261-85. [14]. Ma L, Chen W-X, Li H, Zheng Y-F, Xu Z-D. Mater Lett 2008;62(6-7): 797-799. [15]. Ma L, Chen W-X, Li H, Xu Z-D. Mater Chem Phys 2009;116(2-3): 400-405. [16]. Luo H, Xu C, Zou D, Wang L, Ying T. Mater Lett 2008;62(20): 3558-3560. [17]. Li N, Chai Y, Li Y, Tang Z, Dong B, Liu Y, et al. Mater Lett 2012;66(1): 236-238. [18]. Liu J, Sasidharan M, Liu D, Yokoyama Y, Yusa S-i, Nakashima K. Mater Lett 2012;66 (1): 25-28.
Figure Captions Fig.1. (a) XRD patterns of the as-synthesized and calcined MoS2 samples. (b-e) SEM images of the as-synthesized MoS2 hollow core/shell microspheres. Fig.2. SEM images of the MoS2 microspheres obtained via a hydrothermal route by adding different amounts of ILs: (a) 0 g, (b) 0.3 g, (c) 0.5 g and (d) 1 g. Fig.3. SEM images of the MoS2 microspheres synthesized with 0.3g ILs for different hydrothermal times: (a) 6 h, (b) 12 h, (c) 18 h and (d) 24 h. Fig.4. (a) Illustration of the growth mechanism of MoS2 hollow core/shell microspheres; (b) Illustration of the growth mechanism of MoS2 double-shell microspheres.
Highlights
Hollow core/shell MoS2 microspheres were hydrothermally synthesized
Ionic liquids are important for the formation of hollow core/shell structure
Double-shell structure can be acquired by increasing ionic liquids’ dosage
A soft template mechanism of the hollow core/shell structure is proposed
7