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SnO2 hollow spheres with enhanced activity for hydrazine electro-oxidation
Materials Letters 185 (2016) 346–350
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Facile synthesis of ternary Ag/C/SnO2 hollow spheres with enhanced activity for hydrazine electro-oxidation Wen-Hui Hu, Xiao Shang, Xin-Yu Zhang, Jue Wang, Bin Dong n, Xiao Li, Yan-Ru Liu, Guan-Qun Han, Yong-Ming Chai, Chen-Guang Liu n State Key Laboratory of Heavy Oil Processing, College of Science, China University of Petroleum (East China), Qingdao, 266580 PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 1 July 2016 Received in revised form 2 September 2016 Accepted 6 September 2016 Available online 8 September 2016
Highly dispersed ternary Ag/C/SnO2 hollow spheres have been synthesized for hydrazine electro-oxidation. The sharp XRD peak of Ag shows that Ag nanoparticles of Ag/C/SnO2 have good crystallinity. SEM shows that Ag/C/SnO2 maintained a good spherical morphology with the diameter of about 300 nm. TEM shows that Ag nanoparticles with the average diameter of about 10 nm disperse well on C/SnO2. The advantages derived from C/SnO2 support including carbon, SnO2 and hollow structures may facilitate the dispersion of Ag and the close interaction of Ag with support. The results of hydrazine electro-oxidation show that C/SnO2 has no activity for hydrazine electro-oxidation while ternary Ag/C/SnO2 exhibits excellent electrocatalytic activity with the negative oxidation peak at 0.25 V (vs. SCE) and the high peak current of 473 μA at the scan rate of 20 mV s 1. The enhancement of activity may be attributed to the small size, homogeneous dispersion of Ag and the synergistic effect derived from Ag/C/SnO2 hollow spheres. & 2016 Published by Elsevier B.V.
Keywords: Hollow spheres Ag Nanoparticles Hydrazine Oxidation
1. Introduction Owing to the increasing environmental pollution, new energy techniques have been pursued including Li þ batteries [1], supercapacitors [2], hydrogen energy [3], fuel cells [4] and so on. Due to the high energy density, simple structure and low pollution [5], hydrazine fuel cells have caused a wide attention. Pt-based metal catalysts exhibit best activity for hydrazine fuel cells. However, the scarcity and expensive price have limited the industrial application of hydrazine fuel cells. One effective strategy is to utilize supports such as carbonbased materials [6] and metal oxides [7] to improve the catalytic properties and strong interaction of catalysts. Recently, C. Marichy et al. have reported an electrospinning synthesis of composites based on carbon nanofibers and SnO2, which can greatly enhance the durability of Pt [8]. However, the corrosion of carbon-based support and weak conductivity of metal oxides have been the main drawbacks. Herein, we reported the ternary Ag/C/SnO2 for hydrazine electro-oxidation using C/SnO2 hollow spheres as support, which may alleviate the aggregations of Ag and prolong the stability. The surface of hollow nanostructure may reduce the distance of charge n
Corresponding authors. E-mail addresses: [email protected] (B. Dong), [email protected] (C.-G. Liu).
http://dx.doi.org/10.1016/j.matlet.2016.09.014 0167-577X/& 2016 Published by Elsevier B.V.
transfer and accelerate the reaction rate [9]. The electro-oxidation activity of ternary Ag/C/SnO2 for hydrazine is investigated. The enhancement mechanisms of electrocatalytic activity were discussed.
2. Experimental SnO2 hollow spheres were synthesized through previous report [10]. Firstly, 0.48 g urea was dissolved in 80 mL ethanol/water. Then 0.384 g K2SnO3 3H2O was added. After stirring, the solution was transferred into a 100 mL Teflon-lined stainless steel autoclave and heated at 200 °C for 20 h. For C/SnO2, 0.3 g SnO2 were dispersed in 60 mL 0.5 M glucose solution. The suspension was transferred into a Teflon-lined autoclave and kept at 180 °C for 4 h. Finally, the brown powder was heated at 650 °C for 5 h in Ar flow. The aqua ammonia (v(NH3):v(H2O) ¼1:20) was added into 10.0 mL 0.1 M AgNO3. Then 0.2 g of C/SnO2 hollow nanospheres was added into the silver-ammonia solution. The formaldehyde has been used as reductant. The black powder was obtained. The electro-oxidation of hydrazine has been conducted through a conventional three-electrode system using a Gamry Reference 600 electrochemical work station. Typically, 4 mg of the obtained Ag/C/ SnO2 with 20 μL Nafion were dispersed in 2 mL water-ethanol solution. 5 μL of the dispersion solution was coated onto a glassy
W.-H. Hu et al. / Materials Letters 185 (2016) 346–350
347
Fig. 1. (a) XRD patterns of SnO2, C/SnO2 and Ag/C/SnO2; (b) selected area electron diffraction of Ag/C/SnO2.
carbon electrode (GCE) as working electrode. Saturated calomel electrode (SCE) and Pt foil were used as reference and counter electrode, respectively. The electrolyte was 20 mM hydrazine in 1.0 M KOH solution. Crystallographic structure of all samples was investigated with X-ray powder diffraction (XRD, X′Pert PROMPD, Cu-Kr). The morphology of the samples was examined with scanning electron microscopy (SEM, Hitachi, S-4800). Transmission electron microscopy (TEM) images were collected on HRTEM, JEM-2100UHR with an accelerating voltage of 200 kV. Selected area electron diffraction (SAED) was used to examine samples’ crystallinity.
3. Results and discussion In Fig. 1a, XRD of C/SnO2 and Ag/C/SnO2 both exhibit the obvious diffraction peaks of the black line at 26.5°, 33.8°, 37.9° and 51.7° which are own to (110), (101), (200), and (211) plane of SnO2, respectively (PDF No. 03-065-0380). For C/SnO2, the peak of C cannot be observed, meaning that C in C/SnO2 is amorphous. For Ag/C/SnO2, there are three obvious peaks at 38.1°, 44.3° and 64.4°, which belong to (111), (200) and (220) plane of Ag (PDF No. 00001-1167). Fig. 1b shows the SAED patterns of Ag/C/SnO2, the main peaks of (110), (101) plane of SnO2 and (111), (200) of Ag can be identified. SAED proves that Ag in Ag/C/SnO2 has a very good crystallinity and no diffraction ring of C can be observed. SEM and elemental mapping images have been shown in Fig. 2. Fig. 2a shows that SnO2 hollow spheres dispersed well with the diameter of about 300 nm. SEM image (in Fig. 2b) of the intermediate product SnO2/glucose shows that the spherical morphology was still maintained. Due to the carbonization of the glucose, the dispersion of the intermediate was not as well as the pure SnO2. Fig. 2c shows that C/SnO2 nanospheres were prepared after being calcined 650 °C for 5 h in Ar. Although there are some small particles (in Fig. 2d), Ag/C/SnO2 still presents the originally spherical morphology of SnO2, meaning that the most of Ag coated well on the surface of C/SnO2. SEM mapping of Ag/C/SnO2 shows the existence and good dispersion of Ag and C in Fig. 2e. EDX data of Ag/C/SnO2 furtherly confirm the existence of Ag, C and Sn
element in Fig. 2f, which demonstrate the formation of ternary Ag/ C/SnO2. TEM images show that Ag/C/SnO2 presents hollow and spherical structure with good distribution in Fig. 3a and b. Ag nanoparticles with uniform diameter of about 10 nm dispersed well on C/SnO2 hollow spheres (Fig. 3c). HRTEM image (in Fig. 3d) shows the lattice space of Ag (111) plane and SnO2 (101), respectively, which are consistent with XRD. Fig. 4a shows CV curves of C/SnO2 (black) and Ag/C/SnO2 (red) for electro-oxidation of hydrazine. C/SnO2 has no catalytic activity for hydrazine. For Ag/C/SnO2, an obvious peak appears around at 0.25 V (vs. SCE) with the peak current of 473 μA which is much higher than the previous work [11], which may be due to the high dispersion and small size of Ag nanoparticles as well as the existence of C elements. In addition, C/SnO2 nanospheres as support can also provide better contact with Ag and conductivity for the enhancement of electro-oxidization. Fig. 4b shows CV curves of Ag/C/SnO2 at different scan rates (v) 10, 20, 30, 40, 50 mV s 1. With the increasing scanning rate, the peak current for hydrazine oxidation gradually improved and the potential also move to right. The relationship of Ip against v1/2 is shown in Fig. 4c. The linear relationship can be observed between them, meaning that it may be controlled by a diffusion process for hydrazine electro-oxidation [11].
4. Conclusions Ag/C/SnO2 has been synthesized by the solvothermal method using C/SnO2 hollow spheres as support. The electro-oxidation of hydrazine of Ag/C/SnO2 show the negative oxidation peak and the high peak current density, which may be attributed to the homogeneous dispersion of Ag and C/SnO2 hollow spheres as support. Novel C/SnO2 hollow spheres may provide large surface area, better conductivity, stability based on the synergistic advantages derived from C support and metal oxides support.
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Fig. 2. SEM images: (a) Pure SnO2; (b) SnO2/glucose; (c) C/SnO2; (d) Ag/C/SnO2; (e) SEM elemental mapping of Ag/C/SnO2; (f) EDX of Ag/C/SnO2.
W.-H. Hu et al. / Materials Letters 185 (2016) 346–350
Fig. 3. (a, b and c) TEM images of Ag/C/SnO2; (d) HR-TEM image of Ag/C/SnO2.
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W.-H. Hu et al. / Materials Letters 185 (2016) 346–350
Fig. 4. (a) CV of C/SnO2 and Ag/C/SnO2 at scan rate of 20 m s 1; (b) CV of Ag/C/SnO2 with different scan rate 10, 20, 30, 40, 50 mV s 1 from inner to outer. (c) Plot of peak current (Ip) against square root of scan rates (v1/2).
Acknowledgments This work is financially supported by the National Natural Science Foundation of China (U1162203) and the Fundamental Research Funds for the Central Universities (15CX05031A).
References [1] Q. Zhang, H.B. Wu, T. Song, U. Paik, X.W. Lou, TiO2 hollow spheres composed of high-crystallinity nanocrystals exhibit superior lithium storage properties, Angew. Chem. Int. Ed. 53 (2014) 12590–12593. [2] G.X. Gao, H.B. Wu, S.J. Ding, L.M. Liu, X.W. Lou, Hierarchical NiCo2O4 nanosheets grown on Ni nanofoam as high-performance electrodes for supercapacitors, Small 11 (2015) 804–808. [3] J. Wang, W. Cui, Q. Liu, Z. Xing, A.M. Asiri, X.P. Sun, Recent progress in Cobased heterogeneous catalysts for electrochemical water splitting, Adv. Mater. 28 (2016) 215–230. [4] Z. Zhao, M. Li, L. Zhang, L. Dai, Z. Xia, Design principles for heteroatom-doped carbon nanomaterials as highly-efficient catalysts for fuel cells and metal-air batteries, Adv. Mater. 27 (2015) 6834–6840.
[5] H. Yang, X. Zhong, Z. Dong, J. Wang, J. Jin, J. Ma, Polyethyleneimine decorated graphene oxide-supported Ni1 xFexbimetallic nanoparticles as efficient and robust electrocatalysts for hydrazine fuel cells, Catal. Sci. Technol. 3 (2013) 3155–3162. [6] J. Li, H. Tang, R. Chen, D. Liu, Z. Xie, M. Pan, S.P. Jiang, Highly ordered 3D macroporous scaffold supported Pt/C oxygen electrodes with superior gasproton transportation properties and activities for fuel cells, J. Mater. Chem. A 3 (2015) 15001–15007. [7] L. Zhang, H.B. Wu, B. Liu, X.W. Lou, Formation of porous SnO2 microboxes via selective leaching for highly reversible lithium storage, Energy Environ. Sci. 7 (2014) 1013–1017. [8] C. Marichy, G. Ercolano, G. Caputo, M.G. Willinger, D. Jones, J. Roziere, N. Pinna, S. Cavaliere, A.L.D. SnO2, protective decoration enhances the durability of a Pt based electrocatalyst, J. Mater. Chem. A 4 (2016) 969–975. [9] J. Liang, X.Y. Yu, H. Zhou, H.B. Wu, S.J. Ding, X.W. Lou, Bowl-like SnO2/carbon Hollow Particles as an Advanced Anode Material for Lithium-ion Batteries, Angew. Chem. Int. Ed. 53 (2014) 12803–12807. [10] C.F. Zhang, H.B. Wu, C.Z. Yuan, Z.P. Guo, X.W. Lou, Confining sulfur in doubleshelled hollow carbon spheres for lithium-sulfur batteries, Angew. Chem. Int. Ed. 124 (2012) 9730–9733. [11] Y.R. Liu, W.H. Hu, X.L. Yang, G.Q. Han, B. Dong, Y.M. Chai, Y.Q. Liu, C.G. Liu, Onepot facile synthesis of Ag/TiO2 spheres with enhanced electrocatalytic activity for hydrazine, Mater. Lett. 143 (2015) 181–184.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Facile synthesis of ternary Ag/C/SnO2 hollow spheres with enhanced activity for hydrazine electro-oxidation Wen-Hui Hu, Xiao Shang, Xin-Yu Zhang, Jue Wang, Bin Dong n, Xiao Li, Yan-Ru Liu, Guan-Qun Han, Yong-Ming Chai, Chen-Guang Liu n State Key Laboratory of Heavy Oil Processing, College of Science, China University of Petroleum (East China), Qingdao, 266580 PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 1 July 2016 Received in revised form 2 September 2016 Accepted 6 September 2016 Available online 8 September 2016
Highly dispersed ternary Ag/C/SnO2 hollow spheres have been synthesized for hydrazine electro-oxidation. The sharp XRD peak of Ag shows that Ag nanoparticles of Ag/C/SnO2 have good crystallinity. SEM shows that Ag/C/SnO2 maintained a good spherical morphology with the diameter of about 300 nm. TEM shows that Ag nanoparticles with the average diameter of about 10 nm disperse well on C/SnO2. The advantages derived from C/SnO2 support including carbon, SnO2 and hollow structures may facilitate the dispersion of Ag and the close interaction of Ag with support. The results of hydrazine electro-oxidation show that C/SnO2 has no activity for hydrazine electro-oxidation while ternary Ag/C/SnO2 exhibits excellent electrocatalytic activity with the negative oxidation peak at 0.25 V (vs. SCE) and the high peak current of 473 μA at the scan rate of 20 mV s 1. The enhancement of activity may be attributed to the small size, homogeneous dispersion of Ag and the synergistic effect derived from Ag/C/SnO2 hollow spheres. & 2016 Published by Elsevier B.V.
Keywords: Hollow spheres Ag Nanoparticles Hydrazine Oxidation
1. Introduction Owing to the increasing environmental pollution, new energy techniques have been pursued including Li þ batteries [1], supercapacitors [2], hydrogen energy [3], fuel cells [4] and so on. Due to the high energy density, simple structure and low pollution [5], hydrazine fuel cells have caused a wide attention. Pt-based metal catalysts exhibit best activity for hydrazine fuel cells. However, the scarcity and expensive price have limited the industrial application of hydrazine fuel cells. One effective strategy is to utilize supports such as carbonbased materials [6] and metal oxides [7] to improve the catalytic properties and strong interaction of catalysts. Recently, C. Marichy et al. have reported an electrospinning synthesis of composites based on carbon nanofibers and SnO2, which can greatly enhance the durability of Pt [8]. However, the corrosion of carbon-based support and weak conductivity of metal oxides have been the main drawbacks. Herein, we reported the ternary Ag/C/SnO2 for hydrazine electro-oxidation using C/SnO2 hollow spheres as support, which may alleviate the aggregations of Ag and prolong the stability. The surface of hollow nanostructure may reduce the distance of charge n
Corresponding authors. E-mail addresses: [email protected] (B. Dong), [email protected] (C.-G. Liu).
http://dx.doi.org/10.1016/j.matlet.2016.09.014 0167-577X/& 2016 Published by Elsevier B.V.
transfer and accelerate the reaction rate [9]. The electro-oxidation activity of ternary Ag/C/SnO2 for hydrazine is investigated. The enhancement mechanisms of electrocatalytic activity were discussed.
2. Experimental SnO2 hollow spheres were synthesized through previous report [10]. Firstly, 0.48 g urea was dissolved in 80 mL ethanol/water. Then 0.384 g K2SnO3 3H2O was added. After stirring, the solution was transferred into a 100 mL Teflon-lined stainless steel autoclave and heated at 200 °C for 20 h. For C/SnO2, 0.3 g SnO2 were dispersed in 60 mL 0.5 M glucose solution. The suspension was transferred into a Teflon-lined autoclave and kept at 180 °C for 4 h. Finally, the brown powder was heated at 650 °C for 5 h in Ar flow. The aqua ammonia (v(NH3):v(H2O) ¼1:20) was added into 10.0 mL 0.1 M AgNO3. Then 0.2 g of C/SnO2 hollow nanospheres was added into the silver-ammonia solution. The formaldehyde has been used as reductant. The black powder was obtained. The electro-oxidation of hydrazine has been conducted through a conventional three-electrode system using a Gamry Reference 600 electrochemical work station. Typically, 4 mg of the obtained Ag/C/ SnO2 with 20 μL Nafion were dispersed in 2 mL water-ethanol solution. 5 μL of the dispersion solution was coated onto a glassy
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347
Fig. 1. (a) XRD patterns of SnO2, C/SnO2 and Ag/C/SnO2; (b) selected area electron diffraction of Ag/C/SnO2.
carbon electrode (GCE) as working electrode. Saturated calomel electrode (SCE) and Pt foil were used as reference and counter electrode, respectively. The electrolyte was 20 mM hydrazine in 1.0 M KOH solution. Crystallographic structure of all samples was investigated with X-ray powder diffraction (XRD, X′Pert PROMPD, Cu-Kr). The morphology of the samples was examined with scanning electron microscopy (SEM, Hitachi, S-4800). Transmission electron microscopy (TEM) images were collected on HRTEM, JEM-2100UHR with an accelerating voltage of 200 kV. Selected area electron diffraction (SAED) was used to examine samples’ crystallinity.
3. Results and discussion In Fig. 1a, XRD of C/SnO2 and Ag/C/SnO2 both exhibit the obvious diffraction peaks of the black line at 26.5°, 33.8°, 37.9° and 51.7° which are own to (110), (101), (200), and (211) plane of SnO2, respectively (PDF No. 03-065-0380). For C/SnO2, the peak of C cannot be observed, meaning that C in C/SnO2 is amorphous. For Ag/C/SnO2, there are three obvious peaks at 38.1°, 44.3° and 64.4°, which belong to (111), (200) and (220) plane of Ag (PDF No. 00001-1167). Fig. 1b shows the SAED patterns of Ag/C/SnO2, the main peaks of (110), (101) plane of SnO2 and (111), (200) of Ag can be identified. SAED proves that Ag in Ag/C/SnO2 has a very good crystallinity and no diffraction ring of C can be observed. SEM and elemental mapping images have been shown in Fig. 2. Fig. 2a shows that SnO2 hollow spheres dispersed well with the diameter of about 300 nm. SEM image (in Fig. 2b) of the intermediate product SnO2/glucose shows that the spherical morphology was still maintained. Due to the carbonization of the glucose, the dispersion of the intermediate was not as well as the pure SnO2. Fig. 2c shows that C/SnO2 nanospheres were prepared after being calcined 650 °C for 5 h in Ar. Although there are some small particles (in Fig. 2d), Ag/C/SnO2 still presents the originally spherical morphology of SnO2, meaning that the most of Ag coated well on the surface of C/SnO2. SEM mapping of Ag/C/SnO2 shows the existence and good dispersion of Ag and C in Fig. 2e. EDX data of Ag/C/SnO2 furtherly confirm the existence of Ag, C and Sn
element in Fig. 2f, which demonstrate the formation of ternary Ag/ C/SnO2. TEM images show that Ag/C/SnO2 presents hollow and spherical structure with good distribution in Fig. 3a and b. Ag nanoparticles with uniform diameter of about 10 nm dispersed well on C/SnO2 hollow spheres (Fig. 3c). HRTEM image (in Fig. 3d) shows the lattice space of Ag (111) plane and SnO2 (101), respectively, which are consistent with XRD. Fig. 4a shows CV curves of C/SnO2 (black) and Ag/C/SnO2 (red) for electro-oxidation of hydrazine. C/SnO2 has no catalytic activity for hydrazine. For Ag/C/SnO2, an obvious peak appears around at 0.25 V (vs. SCE) with the peak current of 473 μA which is much higher than the previous work [11], which may be due to the high dispersion and small size of Ag nanoparticles as well as the existence of C elements. In addition, C/SnO2 nanospheres as support can also provide better contact with Ag and conductivity for the enhancement of electro-oxidization. Fig. 4b shows CV curves of Ag/C/SnO2 at different scan rates (v) 10, 20, 30, 40, 50 mV s 1. With the increasing scanning rate, the peak current for hydrazine oxidation gradually improved and the potential also move to right. The relationship of Ip against v1/2 is shown in Fig. 4c. The linear relationship can be observed between them, meaning that it may be controlled by a diffusion process for hydrazine electro-oxidation [11].
4. Conclusions Ag/C/SnO2 has been synthesized by the solvothermal method using C/SnO2 hollow spheres as support. The electro-oxidation of hydrazine of Ag/C/SnO2 show the negative oxidation peak and the high peak current density, which may be attributed to the homogeneous dispersion of Ag and C/SnO2 hollow spheres as support. Novel C/SnO2 hollow spheres may provide large surface area, better conductivity, stability based on the synergistic advantages derived from C support and metal oxides support.
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Fig. 2. SEM images: (a) Pure SnO2; (b) SnO2/glucose; (c) C/SnO2; (d) Ag/C/SnO2; (e) SEM elemental mapping of Ag/C/SnO2; (f) EDX of Ag/C/SnO2.
W.-H. Hu et al. / Materials Letters 185 (2016) 346–350
Fig. 3. (a, b and c) TEM images of Ag/C/SnO2; (d) HR-TEM image of Ag/C/SnO2.
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Fig. 4. (a) CV of C/SnO2 and Ag/C/SnO2 at scan rate of 20 m s 1; (b) CV of Ag/C/SnO2 with different scan rate 10, 20, 30, 40, 50 mV s 1 from inner to outer. (c) Plot of peak current (Ip) against square root of scan rates (v1/2).
Acknowledgments This work is financially supported by the National Natural Science Foundation of China (U1162203) and the Fundamental Research Funds for the Central Universities (15CX05031A).
References [1] Q. Zhang, H.B. Wu, T. Song, U. Paik, X.W. Lou, TiO2 hollow spheres composed of high-crystallinity nanocrystals exhibit superior lithium storage properties, Angew. Chem. Int. Ed. 53 (2014) 12590–12593. [2] G.X. Gao, H.B. Wu, S.J. Ding, L.M. Liu, X.W. Lou, Hierarchical NiCo2O4 nanosheets grown on Ni nanofoam as high-performance electrodes for supercapacitors, Small 11 (2015) 804–808. [3] J. Wang, W. Cui, Q. Liu, Z. Xing, A.M. Asiri, X.P. Sun, Recent progress in Cobased heterogeneous catalysts for electrochemical water splitting, Adv. Mater. 28 (2016) 215–230. [4] Z. Zhao, M. Li, L. Zhang, L. Dai, Z. Xia, Design principles for heteroatom-doped carbon nanomaterials as highly-efficient catalysts for fuel cells and metal-air batteries, Adv. Mater. 27 (2015) 6834–6840.
[5] H. Yang, X. Zhong, Z. Dong, J. Wang, J. Jin, J. Ma, Polyethyleneimine decorated graphene oxide-supported Ni1 xFexbimetallic nanoparticles as efficient and robust electrocatalysts for hydrazine fuel cells, Catal. Sci. Technol. 3 (2013) 3155–3162. [6] J. Li, H. Tang, R. Chen, D. Liu, Z. Xie, M. Pan, S.P. Jiang, Highly ordered 3D macroporous scaffold supported Pt/C oxygen electrodes with superior gasproton transportation properties and activities for fuel cells, J. Mater. Chem. A 3 (2015) 15001–15007. [7] L. Zhang, H.B. Wu, B. Liu, X.W. Lou, Formation of porous SnO2 microboxes via selective leaching for highly reversible lithium storage, Energy Environ. Sci. 7 (2014) 1013–1017. [8] C. Marichy, G. Ercolano, G. Caputo, M.G. Willinger, D. Jones, J. Roziere, N. Pinna, S. Cavaliere, A.L.D. SnO2, protective decoration enhances the durability of a Pt based electrocatalyst, J. Mater. Chem. A 4 (2016) 969–975. [9] J. Liang, X.Y. Yu, H. Zhou, H.B. Wu, S.J. Ding, X.W. Lou, Bowl-like SnO2/carbon Hollow Particles as an Advanced Anode Material for Lithium-ion Batteries, Angew. Chem. Int. Ed. 53 (2014) 12803–12807. [10] C.F. Zhang, H.B. Wu, C.Z. Yuan, Z.P. Guo, X.W. Lou, Confining sulfur in doubleshelled hollow carbon spheres for lithium-sulfur batteries, Angew. Chem. Int. Ed. 124 (2012) 9730–9733. [11] Y.R. Liu, W.H. Hu, X.L. Yang, G.Q. Han, B. Dong, Y.M. Chai, Y.Q. Liu, C.G. Liu, Onepot facile synthesis of Ag/TiO2 spheres with enhanced electrocatalytic activity for hydrazine, Mater. Lett. 143 (2015) 181–184.