Synthesis of Mesoporous Co2+-Doped TiO2 Nanodisks Derived from

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Synthesis of mesoporous Co2+ doped TiO2 nanodisks derived from metal organic frameworks with improved sodium storage performance Zhensheng Hong, Meiling Kang, Xiaohui Chen, Kaiqiang Zhou, Zhigao Huang, and Mingdeng Wei ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b06290 • Publication Date (Web): 11 Jul 2017 Downloaded from http://pubs.acs.org on July 12, 2017

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ACS Applied Materials & Interfaces

Synthesis of mesoporous Co2+ doped TiO2 nanodisks derived from metal organic frameworks with improved sodium storage performance Zhensheng Hong,* †, ‡,

⊥

⊥ Meiling Kang,†, Xiaohui Chen,† Kaiqiang Zhou,† Zhigao Huang, †, ‡

and Mingdeng Wei⊥ †

Fujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials, College of

Physics and Energy, Fujian Normal University, Fuzhou, Fujian 350117, China ‡

Fujian Provincial Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient

Devices, Xiamen, 361005, China ⊥

Institute of Advanced Energy Materials, Fuzhou University, Fuzhou, Fujian 350002, China

*Corresponding Authors: E-mail: [email protected]

Abstract TiO2 is a most promising anode candidate for rechargeable Na-ion batteries (NIBs) due to its appropriate working voltage, low cost and superior structural stability during chage/discharge process. Nevertheless, it suffers from intrinsically low electrical conductivity. Herein, we report an in-situ synthesis of Co2+ doped TiO2 through the thermal treatment of metal organic frameworks precursors of MIL-125(Ti)-Co as a superior anode material for NIBs. The Co2+ doped TiO2 possesses uniform nanodisk morphology, a large surface area and mesoporous structure with narrow pore distribution. The reversible capacity, Coulombic efficiency (CE) and rate capability can be improved by Co2+ doping in mesoporous TiO2 anode. Co2+ doped mesoporous TiO2 nanodisks exhibited a high reversible capacity of 232 mAhg-1 at 0.1 Ag-1, good rate capability and cycling stability with a stable capacity of about 140 mAhg-1 at 0.5 Ag-1 after 500 cycles.

The enhanced Na-ion storage performance could be due to the

increased electrical conductivity revealed by Kelvin probe force microscopy measurements.

Keywords: TiO2; Co2+doping; MOF; sodium-ion batteries; anode 1 ACS Paragon Plus Environment


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1. INTRODUCTION Over the past decades, lithium-ion batteries (LIBs) have already become the most prominent battery technology in our daily life for their wide applications in portable electronics and electric vehicles (EVs), owing to the long cycle life, excellent energy density and environmental friendliness.1,2 However, lithium reserves will be depleted in the future based on the current large-scale applications of LIBs.3 On the contrary, Na-ion batteries (NIBs) with identical conception have recently received intense attentions because of abundant sodium resources and similar electrochemical properties of sodium compared to lithium.4-7 However, the large diameter of the Na-ion (0.97 Å) makes it difficult for NIBs to develop available electrode materials with appropriate interstitial space for Na-ion storage.

Nowadays,

developing suitable anode materials for NIBs with satisfied electrochemical performance is still a major challenge. 4-7 Until now, many studies for NIBs have been reported for investigating anode materials with satisfied Na-ion storage capacity. Low graphitic hard carbon showed a good sodium-ion storage performance as anode materials for NIBs; however, it exhibited poor rate capability and suffered from safety problem due to a low Na-ion storage voltage around 0.01 V.8, 9 Metal alloy (Sn and Sb) , conversion-type metal oxides and metal sulphides have also been reported as potential anode materials because of high theoretical capacity.10-14 Nevertheless, most of them suffered from poor cycling stability during repeated charge-discharge process and too high voltage platform. In view of its material features, titanium dioxide (TiO2) is a most promising anode candidate for rechargeable NIBs due to its superior structural stability and safety during chage/discharge process as well as low cost.15

Nevertheless, pristine TiO2 has

intrinsically low electrical conductivity, resulting to the limited Na-ion storage capacity. In the past few years, many nanostructured TiO2 materials and their composites, such as nanotubes, hollow nanospheres/carbon, nanoporous microfibers, mesoporous structures and 2 ACS Paragon Plus Environment

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nanoporous mesocrystals have been fabricated and exhibited remarkable improved Na-ion storage performance.16-22 It has been demonstrated from the above studies that design of porous structure is an effective strategy to enhance the electrochemical performance of TiO2 anodes for NIBs. The void space in porous electrode will buffer the volumetric variation and release inner stress during charge and discharge process, and this is important especially for host material upon Na-ion interaction. Another good strategy to improve the electrochemical performance is elemental doping, which is an effective way to obtain the enhanced electrical conductivity of TiO2. 23-28 Recently, it has been reported the doping of a low charge state Ni2+ in TiO2 exhibited satisfied electrical conductivity due to the oxygen vacancies, leading to improved Na-ion storage properties.27 However, the research of metal ion doping in TiO2 anode for NIBs is still limited. Metal-organic frameworks (MOFs) are a class of recently developed porous materials, constructed by metal ions and organic linkers. MOFs have wide applications in gas storage, catalysis, drug delivery and sensors, owing to their highly porosities and tunable microstructure.

29-32

Recently, MOFs have been also explored as the ideal templates for the

fabrication of hierarchical porous metal oxide nanostructures and carbon matrices. 33-37 These materials exhibited outstanding electrochemical properties for Li(Na)-ion storage due to the intrinsically unique structure inherited from MOFs precursors. Herein we report, for the first time, mesoporous Co2+ doped TiO2 nanodisks derived from metal organic frameworks precursors of MIL-125(Ti)-Co and their Na-ion storage performance.

The prepared

mesoporous anatase TiO2 nanodisks doped by Co2+ exhibited a very good electrochemical performance of good cyclic stability and rate capability for Na-ion storage. 2. RESULTS AND DISCUSSION The precursors of Ti-based metal organic frameworks were synthesized through a solvothermal method. Figure 1a shows the X-ray diffraction (XRD) patterns of MIL-125(Ti), MIL-125(Ti)-16Co and MIL-125(Ti)-32Co, which demonstrates the formation of the pure 3 ACS Paragon Plus Environment


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phase of MIL-125(Ti).30 The enlarged XRD pattern in the inset of Figure 1a describes the apparent shift to the low angles for MIL-125(Ti)-16Co and MIL-125(Ti)-32Co, suggesting the achievement of Co2+ doping in the crystal structure of MIL-125(Ti). TiO2 and Co2+ doped TiO2 were obtained after thermal treatment of MIL-125(Ti) and MIL-125(Ti)-Co, the XRD patterns are shown in Figure 1b. It could be observed that tetragonal anatase TiO2 (JCPDS 21-1272) can be formed after heat treatment of the Ti-based metal organic frameworks, and the phase of precursors was disappear. The inset in Figure 1b displays the typical diffraction peak of TiO2, TiO2-16Co and TiO2-32Co.

It is notable that (101) diffraction peak slightly

shifts to the low angle with the increase of the Co2+ doping content. In addtion, TG curves (Fig. S2) revealed that the content of residual carbon in TiO2, TiO2-16Co and TiO2-32Co was about 2.5% , 2.5% and 5%, respectively. N2 adsorption-desorption isotherms measurements were adopted to investigate the Brunauer-Emmett-Teller (BET) surface area and pore size distribution of the as-prepared samples, as presented in Figure 2. It is clearly shown that all the samples have a type IV curves. The BET surface area and the pore volume of antase TiO2 were determined to be 101 m2 g-1 and 0.20 cm3 g-1, respectively. As shown in Figure 2b, TiO2 possesses a narrow pore size distribution located aroud 6 nm according to BJH analysis. TiO2-16Co has a larger surface area (146 m2 g-1) and pore volume (0.36 cm3 g-1). As to TiO2-32Co, it exhibits a largest surface area (175 m2 g-1) and pore volume (0.37 cm3 g-1). TiO2-32Co has a similar pore size with TiO2-16Co, where is mostly located aroud 5 nm. Accordingly, the obove three samples exhibit a relatively uniform mesoporous structure. The pore size of both the prepared TiO2 and Co2+ doped TiO2 with mesoporous structure is larger than that of the previous report of porous TiO2 (1-2 nm) derived from MIL-125(Ti).38 It is notable that a relatively large pore size is necessary for Na-ion intercalation, which is also in favor of cycling stability for NIBs.20, 21

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Figure 3a and Figure 3b show the low-magnification and high-magnification images of MIL-125(Ti), respectively. It can be clearly seen that numerous nanoparticles with high quality and uniform size of 200-300 nm were formed.

Interestingly, MIL-125(Ti)

nanoparticles have a square like morphology, while MIL-125(Ti)-16Co (Figure 3c-d) exhibits a disk-shaped morphology with size of 500-700 nm and thickness of 180-200 nm. MIL125(Ti)-32Co depicted in Figure 3e-f displays a similar morphology with that of MIL125(Ti)-16Co, but it has a smaller size of 300-500 nm and thickness of 100-120 nm. However, MIL-125(Ti)-Co with regular morphology and structure can not be formed under the presence of too many Co2+ (64 mg CoCl2·6H2O), as shown in Figure S3. SEM, TEM and HRTEM images of TiO2 are shown in Figure 4. The as-prepared anatse TiO2 bassically inhibited the square shape from MIL-125(Ti), as show in Figure 4a. It can be seen from highmagnification image (Figure 4b) that TiO2 possesses a rough surface and porous structure. The thickness of TiO2 is around 110 nm from the side view depicted in Figure 4a (inset). The morphology and structure of mesoporous anatase TiO2 were further confirmed by TEM and HRTEM images, as shown in Figure 4c-d. SAED pattern in the inset of Figure 4c demonstrated that the whole nanoparticle with square like shape has a polycrystalline structure. HRTEM image (Figure 4d) revealed that it was composed of tiny nanocrystal subunits (5-10 nm). The tiny nanocrystals were highly crystalline, and the clear lattice fringe of 0.35 nm could be well assigned to the (101) spacing of anatase structure. Figure 5a shows the image of TiO2-16Co, a large number of quasi-disk-shaped TiO2 with thickness about 100 nm were found. It could be clearly seen from Figure 5b that the quasidisk-shaped TiO2 is highly porous, and its size is around 250-400 nm. As shown in Figure 5c and Figure 5d, TiO2-32Co also displays nanodisk morphology with smaller thickness (50-60 nm). The size of nanodisk with highly porous structure is bout 200-300 nm.

TEM (Figure

5e) and HRTEM (Figure 5f) images of TiO2-32Co further comfirm its porous structure. The ring pattern made by small diffraction spots (inset in Figure 5e) suggests a 5 ACS Paragon Plus Environment


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polynanocrystalline structure of the nanodisk. Actually, the nanodisk was constructed by tiny nanocrystal subunits.

The nanocrystals subunits with diameter of 5-8 nm were highly

crystalline, as shown in Figure 5f. Elemental mapping has been conducted on the elemental distribution of Ti, O and Co in TiO2-32Co, as depicted in Figure 6a. It’s verifying that the mesoporous TiO2 nanodisks were uniformly doping by Co2+. In addition, the contents of Co2+ in the TiO2-32Co is about 0.94 at.%. It’s intersting that this synthetic method can be extended to prepare Ni2+ doping TiO2 nanodisks when nickel chloride was added, the results are shown in Figure S4. The surface chemical composition and oxidation state of the samples were investigated by by X-ray photoelectron spectroscopy (XPS). Figure 6b displays the XPS spectrum of TiO2, TiO2-16Co and TiO2-32Co, it is seen that the peak intensity of Co would be gradually enhanced with the increasing content of Co doping. As shown in Figure 6c and Figure 6d, the apparent peaks at binding energies of 780.1 eV (Co 2p3/2) are observed, which verifies the chemical state of Co2+ doped in both TiO2-16Co and TiO2-32Co.39 Figure 6e displays the the XPS results of Ti 2p of TiO2, TiO2-16Co and TiO2-32Co. The Ti 2p3/2 and Ti 2p1/2 for TiO2 are located at 458.6 and 464.5 eV, respectively, which corresponds to the characteristics of Ti4+-O bonds. As for TiO2-32Co or TiO2-16Co, the corresponding peaks shift slightly to the lower binding energies of 458.4 and 464.3.8 eV, which could be caused by the formation of oxygen vacancies.27, 40, 41 It’s demostrated that electrode material with a high electrical conductivity is crucial for Na-ion batterites with enhanced electrochemical performances.

Generally, an electron

escaping from the material was hindered by the forces of interaction with a crystal lattice, leading to the creation of a potential barrier on a material surface.

Herein, surface potential

of the samples was measured by means of Kelvin Probe Force Microscopy (KPFM). In this measured technique, surface potential is defined by the work function difference between the tip and the sample:42 6 ACS Paragon Plus Environment

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Vcpd =

Wtip – Wsample e

Here Wtip and Wsample are work functions of the tip and the sample, respectively. Vcpd is the contact potential difference, e is the elementary charge. As show in Figure 7a, the surface potential map of Au foil was measured as a reference sample. Figure 7b-d depicts the surface morphology and the corresponding surface potential maps of TiO2 and TiO2-32Co, respectively (the corresponding measurements of TiO2-16Co are shown in Figure S5).

It’s

observed that the surface potential of TiO2 increased with the doping content of Co2+ and TiO2-32Co has a largest surface potential among them, suggesting a decreased work functions after, and thus leading to improved electrical conductivity.43 Furthermore, the work functions of TiO2, TiO2-16Co and TiO2-32Co were calculated, as shown in Fig. 7f. It’s notable that the work function decreased from 5.02 eV for TiO2 to 4.74 eV for TiO2-32Co (4.87 eV for TiO216Co). Recently, MOFs have been also explored as the ideal templates for the synthesis of porous metal oxide nanostructures with good electrochemical properties.33-38 Herein, mesoporous TiO2 doped by Co2+ with uniform morphology was constructed from metal organic frameworks precursors, which would be expected with a good performance for NIBs. As shown in Figure 8a, a couple of redox peaks between 0.5 V and 1.0 V vs. Na/Na+ with a scan rate of 0.5 mV s-1 are observed from cyclic voltammetry (CV) measurement, which would be ascribed to the reversible reduction of Ti4+ to Ti3+.21-27 CV curve at the first cycle reveals the irreversible side reactions with electrolyte at the first reduced process.

Nevertheless, the

subsequent cycles basically have the same profile, suggesting a reversible Na-ion storage process. Figure 8b-d shows the charge-discharge profiles of TiO2-32Co, TiO2-16Co and TiO2 from the selective cycles at 0.1 Ag-1 in the voltage window of 0.01-3 V. All the samples did not exhibit a well-defined voltage plateaus during charge/discharge process, which is typical for TiO2 anode for NIBs.

TiO2-32Co displays a discharge capacity of 498 mAh g-1 and 7 ACS Paragon Plus Environment


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charge capacity of 232 mAhg-1 at the first cycle. The first charge capacity of TiO2-16Co and TiO2 is 184 and 168 mAhg-1, respectively. Thus, the reversibe capacity of TiO2-16Co is larger than that of TiO2, and TiO2-32Co is largest among them.

The first Coulombic

efficiency (CE) of 47%, 43% and 38% were obtained for TiO2-32Co, TiO2-16Co and TiO2, respectively. Generally speaking, the three samples all dispaly a large irreversible capacity at the first cycle,

which could be mainly ascribed to the formation of a solid-electrolyte

interface (SEI) formation of TiO2 accroding to the the previous report.27, 44, 45 Nevertheless, The reversible capacity and CE could be improved after Co2+ doping, which may be due to the smaller work functions. Figure 9a shows the rate capability of TiO2, TiO2-16Co and TiO2-32Co. The electrodes were cycled for the initial five cycles at 0.1 Ag-1, and the current density gradually increased to 2 Ag-1, and finally returned to 0.2 Ag-1. Although all the three samples display a relatively low (< 50%) first Coulombic efficiency, it will increased to 98% after 5 cycles.

The

reversible capacity (average) of TiO2 is about 168, 140, 105, 77 and 43 mAhg-1 at the current density of 0.1, 0.2, 0.5, 1 and 2 Ag-1, respectively. TiO2-16Co exhibits a larger reversible capacity than that of TiO2. It is notable that the reversible capacity of TiO2-32Co is up to 220, 193, 156, 121 and 94 mAhg-1 at 0.1, 0.2, 0.5, 1 and 2 Ag-1, respectively. Therefore, the reversible capacity of TiO2-32Co is largest capacity among them, which also demonstates a high rate performance. This may be due to the largest surface area and pore volume as well as the smallest thickness, which can provide most electrochemical active sites and short ions/electronics diffusion path, leading to improved Na-ion storage capacity and high rate performance. At the same time, the increased electrical conductivity due to the oxygen vacancies would also be favor for the rate capability, which will be discussed in the following text. Figure 9b presents the cycling performance of the above three samples at 0.1 Ag-1. The reversible capacity of 127, 141 mAhg-1 and 170 mAhg-1 could be maintained after 100 cycles for TiO2, TiO2-16Co and TiO2-32Co, respectively. The long-term cycling performance of 8 ACS Paragon Plus Environment

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TiO2-32Co was shown in Figure 9c.

It’s notable that the reversible capacity starts at 162

mAhg1 and still maintains at 139 mAhg-1 after 500 cycles at 0.5 Ag-1, suggesting excellent cycling stability. These results suggest that the prepared mesoporous anatase TiO2 derived from metal-organic frameworks basically exhibited a very good cycling stability and rate capability for Na-ion storage. AC impedance measurements were performed on the fresh batteries made of TiO2, TiO216Co and TiO2-32Co to investigate their characterizations of electrochemical performance for Na-ion storage. As presented in Figure 9d, the Nyquist complex plane impedance plots are composed of the electrolyte resistance (Rs) at high frequencies, a depressed semicircle at the middle frequencies reflected the impedance of the charge transfer reaction (Rct) and a slope at low frequencies arising from the Warburg impedance (W) corresponded to the Na+ diffusion in the electrode. By fitting the impedance data, the Rct of 521, 332 and 273 Ω was obtained for TiO2, TiO2-16Co and TiO2-32Co, respectively.

Thus, it’s verified that the Rct of

mesoporous TiO2 decreased with the increasing content of Co2+ doping, which could be due to the increase of oxygen vacancies caused by heteroatom doping, leading to the decrease in work functions.

Besides, the large surface area and pore volume can offer abundant

electrode-electrolyte interfaces to store sodium ions, which may be in favor of kinetic performance. The crystal structure of Co2+-doped mesoporous TiO2 electrode during chage/discharge process was sudied by XRD, the reults are shown in Figure S6. It’s obseved that the TiO2 diffraction peaks become weaker compared with the pristine electrode after first discharge, which may be due to the partial transformation of anatase into a rather amorphous sodium titanate structure upon sodium insertion.45 In the subsequent charged process, the diffraction peaks of TiO2 can be basically recovered, suggesting its reversibility during the Na-ion insertion/extraction process. 3. CONCLUSION



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In summary, we develop a mesoporous Co2+ doped TiO2 derived from metal organic frameworks precursors as a superior host material for Na-ion storage. The Co2+ doping in TiO2 with uniform distribution was achieved through the in-situ thermal treatment of MIL125(Ti)-Co. It is notable that such Co2+ doped TiO2 inherited uniform nanodisk morphology from the precursors and possesses a large surface area, pore volume and mesoporous structure with narrow pore distribution. It’s founded that the reversible capacity, Coulombic efficiency and rate capability can be improved by Co2+ doping in mesoporous TiO2 anode. Co2+ doped TiO2 nanodisks displayed a high reversible capacity, good rate performance and cycling stability. This could be attributed to the increased electrical conductivity caused by oxygen vacancies and the larger sufurce area after Co2+ doping. The present study not only provides a route for the synthesis of metal ions doped mesoporous TiO2 derived from metal-organic frameworks, but also brings a promising material for energy storage and conversion. ASSOCIATED CONTENT Supporting Information Experimental details, additional SEM images and XRD patterns. The Supporting Information is available free of charge on the ACS. AUTHOR INFORMATION Corresponding Authors E-mail: [email protected]. Author Contributions Z. H. and M.K. contributed equally to this work. Notes

⊥

The authors declare no competing financial interest. ACKNOWLEDGMENTS This work was financially supported by National Natural Science Foundation of China (NSFC 51502038 and U1505241), National Science Foundation of Fujian Province (2015J01042), and Education Department of Fujian Province (JA14081). 10 ACS Paragon Plus Environment

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References (1) Armand, M.; Tarascon, J. M. Building Better Batteries. Nature 2008, 451, 652-657. (2) Croguennec, L.; Palacin, M. R. Recent Achievements on Inorganic Electrode Materials for Lithium-Ion Batteries. J. Am. Chem. Soc. 2015, 137, 3140-3156. (3) Tarascon, J.-M. Is Lithium the New Gold? Nat. Chem. 2010, 2, 510-510. (4) Luo, W.; Shen, F.; Bommier, C.; Zhu, H.; Ji, X.; Hu, L. Na-Ion Battery Anodes: Materials and Electrochemistry. Accounts. Chem. Res. 2016, 49, 231-240. (5) Kim, Y.; Ha, K.-H.; Oh, S. M.; Lee, K. T. High-Capacity Anode Materials for Sodium-Ion Batteries. Chem. Eur. J. 2014, 20, 11980-11992. (6) Kang, H.; Liu, Y.; Cao, K.; Zhao, Y.; Jiao, L.; Wang, Y.; Yuan, H. Update on Anode Materials for Na-Ion Batteries. J. Mater. Chem. A 2015, 3, 17899-17913. (7) Yabuuchi, N.; Kubota, K.; Dahbi, M.; Komaba, S. Research Development on Sodium-Ion Batteries. Chem. Rev. 2014, 114, 11636-11682. (8) Zhang, B.; Ghimbeu, C. M.; Laberty, C.; Vix-Guterl, C.; Tarascon, J.-M. Correlation Between Microstructure and Na Storage Behavior in Hard Carbon. Adv. Energy Mater. 2016, 6, 1501588. (9) Li, Y.; Hu, Y.-S.; Titirici, M.-M.; Chen, L.; Huang, X. Hard Carbon Microtubes Made from Renewable Cotton as High-Performance Anode Material for Sodium-Ion Batteries. Adv. Energy Mater. 2016, 6, 1600659. (10) Liang, L.; Xu, Y.; Wang, C.; Wen, L.; Fang, Y.; Mi, Y.; Zhou, M.; Zhao, H.; Lei, Y. Large-Scale Highly Ordered Sb Nanorod Array Anodes with High Capacity and Rate Capability for Sodium-Ion Batteries. Energy Environ. Sci. 2015, 8, 2954-2962. (11) Li, N.; Liao, S.; Sun, Y.; Song, H. W.; Wang, C. X. Uniformly Dispersed SelfAssembled Growth of Sb2O3/Sb@Graphene Nanocomposites on a 3D Carbon Sheet



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Network for High Na-Storage Capacity and Excellent Stability. J. Mater. Chem. A 2015, 3, 5820-5828. (12) Wang, L.; Zhang, K.; Hu, Z.; Duan, W.; Cheng, F.; Chen, J. Porous CuO Nanowires as the Anode of Rechargeable Na-Ion Batteries. Nano Res. 2014, 7, 199-208. (13) Wang, T.; Chen, S.; Pang, H.; Xue, H.; Yu, Y. MoS2-Based Nanocomposites for Electrochemical Energy Storage. Adv. Sci. 2017, 4, 1600289. (14) Zhu, C.; Mu, X.; van Aken, P. A.; Yu, Y.; Maier, J. Single-Layered Ultrasmall Nanoplates of MoS2 Embedded in Carbon Nanofibers with Excellent Electrochemical Performance for Lithium and Sodium Storage. Angew.Chem. Int. Ed. 2014, 53, 21522156. (15) Mei, Y.; Huang, Y.; Hu, X. Nanostructured Ti-Based Anode Materials for Na-Ion Batteries. J. Mater. Chem. A 2016, 4, 12001-12013. (16) Ni, J.; Fu, S.; Wu, C.; Maier, J.; Yu, Y.; Li, L. Self-Supported Nanotube Arrays of Sulfur-Doped TiO2 Enabling Ultrastable and Robust Sodium Storage. Adv. Mater. 2016, 28, 2259-2265. (17) Su, D.; Dou, S.; Wang, G. Anatase TiO2: Better Anode Material Than Amorphous and Rutile Phases of TiO2 for Na-Ion Batteries. Chem. Mater. 2015, 27, 6022-6029. (18) Wang, N.; Gao, Y.; Wang, Y.-X.; Liu, K.; Lai, W.; Hu, Y.; Zhao, Y.; Chou, S.-L.; Jiang, L. Nanoengineering to Achieve High Sodium Storage: A Case Study of Carbon Coated Hierarchical Nanoporous TiO2 Microfibers. Adv. Sci. 2016, 3, 1600013 (19) Wu, Y.; Liu, X.; Yang, Z.; Gu, L.; Yu, Y. Nitrogen-Doped Ordered Mesoporous Anatase TiO2 Nanofibers as Anode Materials for High Performance Sodium-Ion Batteries. Small 2016, 12, 3522-3529. (20) Hong, Z.; Zhou, K.; Zhang, J.; Huang, Z.; Wei, M. Facile Synthesis of Rutile TiO2 Mesocrystals with Enhanced Sodium Storage Properties. J. Mater. Chem. A 2015, 3, 17412-17416. 12 ACS Paragon Plus Environment

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(21) Hong, Z.; Zhou, K.; Huang, Z.; Wei, M. Iso-Oriented Anatase TiO2 Mesocages as a High Performance Anode Material for Sodium-Ion Storage. Sci. Rep. 2015, 5, 11960. (22) Longoni, G.; Pena Cabrera, R. L.; Polizzi, S.; D’Arienzo, M.; Mari, C. M.; Cui, Y.; Ruffo, R. Shape-Controlled TiO2 Nanocrystals for Na-Ion Battery Electrodes: The Role of Different Exposed Crystal Facets on the Electrochemical Properties. Nano Lett. 2017, 17, 992-1000. (23) Zhao, F.; Wang, B.; Tang, Y.; Ge, H.; Huang, Z.; Liu, H. K. Niobium Doped Anatase TiO2 as an Effective Anode Material for Sodium-Ion Batteries. J. Mater. Chem. A 2015, 3, 22969-22974. (24) Yan, D.; Yu, C.; Bai, Y.; Zhang, W.; Chen, T.; Hu, B.; Sun, Z.; Pan, L. Sn-doped TiO2 Nanotubes as Superior Anode Materials for Sodium Ion Batteries. Chem. Commun. 2015, 51, 8261-8264. (25) Usui, H.; Yoshioka, S.; Wasada, K.; Shimizu, M.; Sakaguchi, H. Nb-Doped Rutile TiO2: a Potential Anode Material for Na-Ion Battery. ACS Appl. Mater. Interfaces 2015, 7, 6567-6573. (26) Wang, B.; Zhao, F.; Du, G.; Porter, S.; Liu, Y.; Zhang, P.; Cheng, Z.; Liu, H. K.; Huang, Z. Boron-Doped Anatase TiO2 as a High-Performance Anode Material for Sodium-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 16009-16015. (27) Yan, D.; Yu, C.; Li, D.; Zhang, X.; Li, J.; Lu, T.; Pan, L. Improved Sodium-Ion Storage Performance of TiO2 Nanotubes by Ni2+ Doping. J. Mater. Chem. A 2016, 4, 1107711085. (28) Li, Y.; Shen, J.; Li, J.; Liu, S.; Yu, D.; Xu, R.; Fu, W.-F.; Lv, X.-J. Constructing a Novel Strategy for Carbon-Doped TiO2 Multiple-Phase Nanocomposites toward Superior Electrochemical Performance for Lithium Ion Batteries and the Hydrogen Evolution Reaction. J. Mater. Chem. A 2017, 5, 7055-7063.



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(29) Liu, J.; Chen, L.; Cui, H.; Zhang, J.; Zhang, L.; Su, C.-Y. Applications of Metal-Organic Frameworks in Heterogeneous Supramolecular Catalysis. Chem. Soc. Rev. 2014, 43, 6011-6061. (30) Dan-Hardi, M.; Serre, C.; Frot, T.; Rozes, L.; Maurin, G.; Sanchez, C.; Férey, G. A New Photoactive Crystalline Highly Porous Titanium(IV) Dicarboxylate. J. Am. Chem. Soc. 2009, 131, 10857-10859. (31) Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.; Bloch, E. D.; Herm, Z. R.; Bae, T.-H.; Long, J. R. Carbon Dioxide Capture in Metal-Organic Frameworks. Chem. Rev. 2012, 112, 724-781. (32) Gkaniatsou, E.; Sicard, C.; Ricoux, R.; Mahy, J.-P.; Steunou, N.; Serre, C. Metal-organic Frameworks: a Novel Host Platform for Enzymatic Catalysis and Detection. Mater. Horiz. 2017, 4, 55-63. (33) Salunkhe, R. R.; Kaneti, Y. V.; Kim, J.; Kim, J. H.; Yamauchi, Y. Nanoarchitectures for Metal-Organic Framework-Derived Nanoporous Carbons toward Supercapacitor Applications. Accounts. Chem. Res. 2016, 49, 2796-2806. (34) Yu, L.; Hu, H.; Wu, H. B.; Lou, X. W. Complex Hollow Nanostructures: Synthesis and Energy-Related Applications. Adv. Mater. 2017, 1604563. (35) Kaneti, Y. V.; Tang, J.; Salunkhe, R. R.; Jiang, X.; Yu, A.; Wu, K. C. W.; Yamauchi, Y. Nanoarchitectured Design of Porous Materials and Nanocomposites from Metal-Organic Frameworks. Adv. Mater. 2016, 2017, DOI: 10.1002/adma.201604898. (36) Xie, Z.; Xu, W.; Cui, X.; Wang, Y. Recent Progress in Metal–Organic Frameworks and Their Derived Nanostructures for Energy and Environmental Applications. ChemSusChem 2017, DOI: 10.1002/adma.201604898. (37) Li, Z.; Wu, H. B.; Lou, X. W. Rational Designs and Engineering of Hollow Micro/Nanostructures as Sulfur Hosts for Advanced Lithium-Sulfur Batteries. Energy Environ. Sci. 2016, 9, 3061-3070. 14 ACS Paragon Plus Environment

Page 14 of 25

Page 15 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(38) Wang, Z.; Li, X.; Xu, H.; Yang, Y.; Cui, Y.; Pan, H.; Wang, Z.; Chen, B.; Qian, G. Porous Anatase TiO2 Constructed from a Metal-Organic Framework for Advanced Lithium-Lon Battery Anodes. J. Mater. Chem. A 2014, 2, 12571-12575. (39) Huang, W.; Zuo, Z.; Han, P.; Li, Z.; Zhao, T. XPS and XRD Investigation of Co/Pd/TiO2 Catalysts by Different Preparation Methods. J. Electron Spectrosc 2009, 173, 88-95. (40) Eom, J.-Y.; Lim, S.-J.; Lee, S.-M.; Ryu, W.-H.; Kwon, H.-S. Black Titanium Oxide Nanoarray Electrodes for High Rate Li-Ion Microbatteries. J. Mater. Chem. A 2015, 3, 11183-11188. (41) Tan, H.; Zhao, Z.; Niu, M.; Mao, C.; Cao, D.; Cheng, D.; Feng, P.; Sun, Z. A Facile and Versatile Method for Preparation of Colored TiO2 with Enhanced Solar-Driven Photocatalytic Activity. Nanoscale 2014, 6, 10216-10223. (42) Melitz, W.; Shen, J.; Kummel, A. C.; Lee, S. Kelvin Probe Force Microscopy and Its Application. Surf. Sci. Rep. 2011, 66, 1-27. (43) Zhu, J.; Zeng, Kai.; Lu, L. In-Situ Nanoscale Mapping of Surface Potential in All-SolidState Thin Film Li-Ion Battery Using Kelvin Probe Force Microscopy. J. Appl. Phys. 2012, 111, 063723. (44) Kim, K.-T.; Ali, G.; Chung, K. Y.; Yoon, C. S.; Yashiro, H.; Sun, Y.-K.; Lu, J.; Amine, K.; Myung, S.-T. Anatase Titania Nanorods as an Intercalation Anode Material for Rechargeable Sodium Batteries. Nano Lett. 2014, 14, 416-422. (45) Wu, L.; Bresser, D.; Buchholz, D.; Giffin, G. A.; Castro, C. R.; Ochel, A.; Passerini, S. Unfolding the Mechanism of Sodium Insertion in Anatase TiO2 Nanoparticles. Adv. Energy Mater. 2015, 5, 1401142.



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(a)

6.0

6.5

7.0

7.5

MIL-125(Ti)-32Co MIL-125(Ti)-16Co MIL-125(Ti)

5

10

15 20 25 30 2 Theta (degree)

35

40

(b)

22

24

26

28

TiO2-32Co TiO2-16Co TiO2

10

20

30

40

50

60

70

80

2 Theta (degree)

Figure 1 (a) XRD patterns of MIL-125(Ti), 16Co-MIL-125(Ti) and 32Co-MIL-125(Ti), (b) XRD patterns of TiO2, TiO2-16Co and TiO2-32Co obtained from the thermal treatment of the corresponding MOF precursors in (a). The insets in (a) and (b) are the corresponding enlarged XRD pattern from the typical peaks.


300

(a)

250


200 150 100 50 0 0.0

0.2

0.4

0.6

0.8

1.0

Relative pressure (P/P0) 0.10 dV/dD (cm3g-1nm-1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3 -1 Volume absorbed (cm g )

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(b)

TiO2-32Co

0.08

TiO2-16Co TiO2

0.06 0.04 0.02 0.00

0

5

10

15 20 D (nm)

25

30

Figure 2 (a) Nitrogen adsorption-desorption isotherms and (b) the corresponding BJH pore size distribution of TiO2, TiO2-16Co and TiO2-32Co.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 3 SEM images of (a, b) MIL-125(Ti), (c, d) MIL-125(Ti)-16Co and (e, f) MIL125(Ti)-32Co.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4 (a, b) SEM, TEM (c) and HRTEM (d) images of TiO2. The inset in (c) is the related SAED pattern.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 5 SEM images of TiO2-16Co (a, b) and TiO2-32Co (c, d), TEM (e) and HRTEM (f) images of TiO2-32Co (c, d). The inset in (e) is the related SAED pattern.


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(a) Ti

O

Co

100 nm

(b)

(c)

Co 2p

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Co 2p

TiO2-32Co TiO2-16Co TiO2-C

0

200

400

600

780

800 1000 1200

Binding Energy (eV) Co 2p

(d)

790

800

810

Binding Energy (eV) Ti 2p

(e)


780

790

800

450

810

455

460

465

Binding Energy (eV)

Binding Energy (eV)

Figure 6 (a) Corresponding EDX elemental mapping Ti, O and Co of TiO2-32Co. (b) XPS survey of TiO2, TiO2-16Co and TiO2-32Co, Co 2p band of (c) TiO2-16Co and (d) TiO2-32Co, (e) Ti 2p bands of the above three samples. 21 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 7 Surface potential maps of (a) Au foil, (c)TiO2 and (e) TiO2-32Co. Topography of (b) TiO2 and (d) TiO2-32Co. (f) Work functions of TiO2, TiO2-16Co and TiO2-32Co. .


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0.25

Voltage vs. Na/Na ( V)

(a)

-0.25 1st 4th

-0.50 -0.75

3

(b) 1st 2nd 5th

+

Current (mA)

0.00

0.0

0.5

1.0

2nd 5th 1.5

3rd

2.0

2.5

2

1

0

3.0

0

100

(c)

1

0

400

500

3

(d)

600

1st 2nd 5th

+

+

1st 2nd 5th

2

0

300

-1


3

200

Capacity (mAh g )

Voltage (V)


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


100 200 300 400 500 600 700

Capacity (mAh g ) -1

2

1

0

0

100

200

300

400

500

Capacity (mAh g ) -1

Figure 8 (a) CV curves of TiO2-32Co between 0.01 and 3.0 V with a scan rate of 0.5 mV s-1. Charge-discharge profiles of (b)TiO2-32Co, (c)TiO2-16Co and (d)TiO2 at 0.1 A g-1.



600

750

450

0.1 A g-1 0.2 A g-1 0.5 A g-1 1 A g-1

300 150 0

(b)

TiO2 TiO2-16Co TiO2-32Co

-1

600

Capacity (mAh g )

-1

Capacity (mAh g )

(a)

0.2 A g-1 2 A g-1

450

5

10

15

20

25

TiO2 TiO2-16Co TiO2-32Co

300 150 0

0

30

0

20

40

(c)

80

300

60

200

40

0.5 A g-1

100 0

1500

100

20 0

100

200

300

400

CPE1

80

100

(d)

Rs

1200 Rct W1

-Z''/ohm

-1

Capacity (mAh g )

500 400

60

Cycle number

Cycle number

Columbic efficiency

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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900 600 TiO2 TiO2-16Co

300

TiO2-32Co

0 500

0

Cycle number

0

200

400

600

800

1000

Z'/ohm

Figure 9 (a) Rate capability and (b) cycling performance at 0.1 A g-1 of TiO2, TiO2-16Co and TiO2-32Co. (c) Long cycling performance of TiO2-32Co at 0.5 A g-1. (d) Electrochemical impedance spectra (EIS) of the above three samples. The inset in (d) is the corresponding equivalent circuit.


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Table Of Contents (TOC)

O

-1

Ti

Capacity (mAh g )

500

80

300

60

200

40

100

20

0

Co

100

400

0

100

200

300

400

Columbic efficiency

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0 500

Cycle number


Synthesis of Mesoporous Co2+-Doped TiO2 Nanodisks Derived from

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