carbon nanorods hybrid materials for supercapacitor application

Author’s Accepted Manuscript Facile synthesis of MOF-derived porous spinel zinc manganese oxide/carbon nanorods hybrid materials for supercapacitor application Zihao Zhu, Zhongbing Wang, Zhaobin Yan, Rongqing Zhou, Zhenpeng Wang, Chunnian Chen www.elsevier.com/locate/ceri

PII: DOI: Reference:

S0272-8842(18)32049-2 https://doi.org/10.1016/j.ceramint.2018.07.310 CERI19032

To appear in: Ceramics International Received date: 5 July 2018 Revised date: 30 July 2018 Accepted date: 31 July 2018 Cite this article as: Zihao Zhu, Zhongbing Wang, Zhaobin Yan, Rongqing Zhou, Zhenpeng Wang and Chunnian Chen, Facile synthesis of MOF-derived porous spinel zinc manganese oxide/carbon nanorods hybrid materials for supercapacitor a p p l i c a t i o n , Ceramics International, https://doi.org/10.1016/j.ceramint.2018.07.310 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.

Facile synthesis of MOF-derived porous spinel zinc manganese oxide/carbon nanorods hybrid materials for supercapacitor application

Zihao Zhu, Zhongbing Wang*, Zhaobin Yan, Rongqing Zhou, Zhenpeng Wang, Chunnian Chen Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China *

Corresponding author: Tel.: +86-551-62901451; fax: +86-551-62901450,

[email protected]

Abstract For the past few years, transition metal oxides have attracted significant attention for supercapacitor due to their high theoretical capacity, low costs, and abundant natural reserves. In this work, we present a facile strategy to fabricate spinel zinc manganese oxide/carbon hybrid materials with rod-like structures from mixed-MOFs. Through two-steps calcining the mixed-MOFs constituted by metal ion and 1, 3, 5-Benzenetricarboxylic acid in different condition, the mixed-MOFs have converted to ZnMn2O4/carbon nanorods. The 1D rod-like nanostructure inherited from the MOFs was preserved intact during the process. Due to the porous 1D nanostructure and synergistic effect between the transition metal oxide and carbon, the specific capacitance of hybrid materials reaches to 589 F g-1 at 1 A g-1 within the potential window of 0−1.2 V. Meanwhile, the hybrid materials display superior capacitive behavior at high current density (278 F g-1 at 20 A g-1) and outstanding cycling stability (98.1% retention after 2000 cycles at 10 A g-1). The results imply that the 1

MOFs-derived hybrid materials could be potential electrode materials.

1 Introduction Due to the excessive consumption of fossil energy and the consequential environmental issue, demand in renewable energy resources is increasing.[1] Humankind has been driven by the ever-increasing demand to pay more research efforts to the field of sustainable energy. As a result of relatively high power density and excellent stability,[2] electrochemical supercapacitors attracted intense research interest as promising energy storage devices. Nevertheless, the application of supercapacitors is limited by lower energy density compared to lithium batteries.[3] Based on the above reasons, a great variety of nanomaterials have been researched for application as prominent electrode material in supercapacitors. Because of high theoretical capacity, transition metal oxides (TMO) have attracted increasing attentions of researchers for the past few years. Compared with carbon materials and conducting polymers, TMO exhibit superior characters including excellent redox activity, wider potential window and abundant reserves. In recent years, a vast variety of TMO materials and hybrid materials have been reported and show great potential as the electrode material for high perform supercapacitors.[4, 5] Especially ternary metal oxides with spinel crystal structure have received considerable attention. As the result of the synergistic effect between different cations, various properties of materials have been improved such as conductivity, cycling life and potential window.[6] In recent years, a large number of ternary metal oxides with spinel structure have been researched such as NiMn2O4,[7] NiCo2O4,[8] ZnMn2O4[9] and so forth. Among them, spinel zinc manganese oxide (ZnMn2O4) is worthy of consideration as a candidate for high-performance supercapacitors according to 2

previous researches.[9-11] Due to varieties of valence states of Mn, ZnMn2O4 exhibits high specific capacitance and lots of redox-active sites. However, spinel metal oxides are suffered from inherent defect, for instance poor dispersion, lower surface area and unsatisfactory conductivity. According to these reasons, tremendous efforts have been made to overcome above drawbacks. Xu and his co-workers enhances electrochemical behaviors of the materials by building unique hierarchic Co3O4@NiCo2O4 core-shell nanostructures.[12] Kong’s group reported 3D NiCo2O4@PPy hybrid material with superior electrochemical performances, the electron transportation of material has been improved by PPy.[13] Designing with nanostructure and incorporation with carbon materials provide a considerable approach to prepare high-performance spinel metal oxides hybrid materials. For the purpose of obtaining ideal material for supercapacitors, many factors should be considered such as surface area, conductivity, stability and so on. Nano materials demonstrate tremendous competitive advantage in this field. For the past few years, various nanomaterials on different dimensions from 0 to 3 have been reported as high perform supercapacitors such as nanospheres[14], nanotubes[15], nanosheets[16] nanocages [17] and so on. In particular, one-dimension nanomaterials present excellent properties in the field of energy. Zhang’s group reported a general approach to preparation of manganese-based nanobars for lithium-ion battery.[18] Bella and his co-workers obtained membranes with TiO2 nanotube array for high performance solar cell.[19] More to the point, as the result of high aspect ratio, one-dimension materials possess multiple advantages including short electrons and ions diffusion path, higher surface area and so forth.[20] Peng and his workmates investigated the energy storage applications of spinel 1D nanotube materials and the materials possess appealing performance.[21] Shaheen’s group reported rGO/MoO3 3

nanowires composites as electrode material and the materials exhibited tremendous potential.[22] For purpose of fabrication of one-dimensional nanostructure, metal-organic frameworks (MOFs) are worth expecting to build one-dimensional architectures in a facile and mild strategy. Since 1990s, Yaghi and Li first synthesized MOFs, MOFs have attracted an increasing number of attentions. MOFs constructed from metal ions and organic linkers, are fascinating category of porous materials and usually used in the fields of gas-liquid separation, catalyze, gas storage and so on.[23] However the thermal stability limits the applications of the MOFs in aforementioned fields. On the other hand, MOFs are ideal templates to build various nanostructures based on the poor thermal stability. Due to the unique advantages, for instance, miscellaneous compositions, controlled nanostructures, shorter electron and ion diffusion path and so forth, MOFs have been utilized to prepare nanomaterial for energy storage in the past few years. Different MOF-derived nanomaterials with various structures have been reported, such as carbon materials, TMOs and hybrid materials. A kind of hollow cage NixCo3-xO4 derived from ZIF-67 have been reported by Jayakumar, and NixCo3-xO4/graphene hybrid materials were investigated as electrode material for supercapacitors.[24]

Yuan’s group fabrication octahedral CuO

wrapped 3D graphen network as binder-free anode for lithium-ion batteries and the materials exhibit excellent electrochemical properties. [25] N-doped carbon materials with different nitrogen content surface areas and graphitization leaves derived from ZIF-8 were systematically investigated for enhancing perform of lithium-sulfur batteries. [26] Nevertheless, there are few strategies to synthesize ternary spinel metal oxides/carbon hybrid materials from MOFs without extra carbon source to the best of our knowledge. Herein, we present a facile method to obtain ZnMn2O4/Carbon nanorods (ZMCN) 4

hybrid materials from mixed-MOFs without extra carbon source. The as-prepared ZnMn2O4/Carbon hybrid materials possess unique porous 1D rod-like structures with large specific surface area and the spinel metal oxides were uniformly dispersed in the carbon support. Due to the unique structures and synergistic effect between the spinel and carbon, the electrochemical performance was significantly enhanced. Firstly, Zn-Mn-MOFs were constructed from Zn ions, Mn ions and organic linkers (1, 3, 5-benzenetricarboxylic acid), and the MOFs possessed appealing 1D nanostructures. Subsequently the MOFs were carbonized by pyrolysing in the N2 atmosphere at 500℃ as the sacrificial template. After carbonization, the as-fabricated product was calcined in the air at 300℃ to ensure the formation of the spinel structure.

As compared with

the ZnMn2O4 nanorods (ZMON) derived from the same mixed-MOFs, the hybrid materials possess wider application prospect as the electrode materials for supercapacitors. The maximum specific capacitance of the hybrid materials is as high as 589 F g-1 at 1 A g-1 and the capacitance retention is 98.1% after 2000 cycles, indicating the superior potential in energy storage.

2 Experiment section 2.1 Preparation of 1D ZMCN hybrid materials 1, 3, 5-Benzenetricarboxylic acid (H3BTC) was purchased from Macklin Biochemical Co. Ltd. The other chemicals were obtained from Sinopharm Chemical Reagent Co. Ltd. All reagents were of analytical grade and used directly. The synthesis of mixed-MOFs was based the previous report with some modifications.[27] Briefly, 735 mg manganese acetate tetrahydrate (C4H4MnO4·4H2O) and 329 mg Zinc acetate dehydrate (C4H4ZnO4·2H2O) were dissolved in 50 ml of ethanol and 50 ml of deionized water with stirring for 15 min to give solution I. In the meaning time, 945 5

mg trimesic acid (H3BTC) was dissolved in 50 ml of ethanol and 50 ml of deionized water with stirring to form solution II. Solution II was added to solution I slowly, and the mixture was keeping stirring at the room temperature for 4 h. The mixed-MOFs were obtained by centrifugation and washing with deionized water and ethanol for several times. After drying the mixed-MOFs at 60℃ overnight, the mixed-MOFs were carbonized at 500 ℃ for 1 h in N2 atmosphere with the ramp rate of 5 ℃ min-1. Subsequently, the as-prepared product was calcined at 300 ℃ in air for 1 h to ensure the formation of the spinel structures. The 1D ZMCN were synthesized successfully through aforementioned steps. For comparison, the 1D ZMON were prepared by calcining the mixed-MOFs at 450 ℃ for 2h in the air.

2.2 Characterization The crystalline phase of the as-obtain materials was analyzed from X-ray powder diffraction (XRD) on a X'Pert PRO MPD using a Cu Kα radiation with 2 range of 5°−70°. The morphologies of the materials were characterized by field emission scanning electron microscopy (FESEM) and highresolution transmission electron microscopy (HRTEM) with Hitachi SU8020 operating at 5.0 kV and JEOL JEM-2100 operating at 200 kV, respectively. The specimens used in morphological characterization were preprocessed by diffusing materials into ethanol. The X-ray photoelectron

spectroscopy

(XPS)

was

carried

on

a

Thermo

Scientific

ESCALAB250Xi with a focused monochrome Al Ka X-ray source. BET surface area was obtained using N2 adsorption/desorption isotherm measurements at 77.3 K on a Autosorb-IQ3.

6

2.3 Electrochemical measurements The working electrodes were prepared by dispersing active power (80 wt.%), acetylene black (10 wt.%) and polyvinylidene fluoride (10 wt.%) in N-methyl pyrrolidone to form homogeneous slurry, then coating the slurry on a platinum mesh current collector (1x1 cm2) and dried at 60 ℃ overnight. The loading mass of the mixture on the electrode was 1.0−2.0 mg. The electrochemical performance was evaluated in 1 M Na2SO4 electrolyte solution with a standard three-electrode system on

a

CHI660e

workstation

by

cyclic

voltammetry

(CV),

galvanostatic

charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements. The platinum sheet and saturated calomel electrode (SCE) were utilized as counter electrode and reference electrode, respectively. The specific capacitance (C, F g-1) was calculated from the GCD by following equation (Eq. (1)): C = I ∆t/∆V

(1)

Where I is the current density based on the loading mass on the current collector, ∆t is the discharging time and ∆V is the potential window, respectively.

3 Results and discussion The ZnMn2O4/Carbon nanorods hybrid materials were successfully derived from MOFs without extra carbon source through a facile strategy. Firstly, the mixed-MOFs were constructed from Zn2+, Mn2+ and H3BTC in an EtOH/H2O system at room temperature and utilized as self-sacrificial template. After pyrolyzation in N2 atmosphere at 500 ℃ for 1h, the mixed-MOFs were carbonized. Subsequently the as-prepared mixtures were calcined in the air for 1h at 300 ℃ to ensure the formation of spinel structure, and the final product ZMCN was obtained. The composition and crystallographic structures of the as-obtained samples were analyzed by XRD. As 7

shown in the Fig. 1, the diffraction peaks of the mixed-MOFs were consistent with Zheng’s and Huang’s reports.[28, 29] The diffraction peaks of ZMCN at 18.2°, 29.3°, 31.2°, 33.0°, 36.4°, 44.8°, 51.9°, 59.0°, 60.8° and 65.2° can be assigned to the (101), (112), (200), (103), (211), (220), (105), (321), (224) and (400) planes, respectively, indicating the spinel structure of ZnMn2O4 has been obtained after thermal treatment (JCPDS no. 24-1133). In addition, a distinct broad peak at around 25°, which was attributed to (002) of carbon. It is worth mentioning that there is no excess peak in the pattern, proving the relatively high purity of materials. The composition and oxidation states of the ZMCN were inquired into by XPS. The presence of Zn, Mn, O, and C can be confirmed from the survey spectrum of the hybrid materials as shown in Fig. 2a. In the Fig. 2b, the peaks located at 1021.1 eV and 1043.3 eV can be ascribed to Zn 2p3/2 and Zn 2p1/2.[30] The Fig. 2c reveals the Mn 2p3/2 peak and Mn 2p1/2 peak at 642.1 eV and 653.9 eV, and these two peaks can be fitted into several deconvoluted peaks for different valance states of Mn. The fitted peaks at 640.8 eV and 653.0 eV were allotted to Mn2+, the peaks at 642.2 eV and 654.13 eV were related to Mn3+, the rest of peak at 643.0 eV was corresponded to Mn4+.[31] The spectrum of C 1s shown in Fig. 2d can be fitted into three peaks located at 284.6 eV, 285.3 eV and 288.5 eV, these peaks were ascribed to the presence of the C=C. C-O and C=O, respectively.[32] The three fitted peaks of the O 1s spectrum shown in Fig. 2e were located at 529.8 eV, 530.3 eV and 531.8 eV, demonstrating the representative metal oxygen bond, hydroxyl bond and oxygen in defects states.[24] The micromorphology of the mixed-MOFs and hybrid materials were investigated by FESEM and HRTEM. The Fig. 3a and b reveal that mixed-MOFs possess 1D nanostructure with smooth surface and the size of most nanorods was 8

uniform. It is distinct to confirm that the diameter of mixed-MOFs nanorods was approximately 100 nm and the length of nanorods was nearly 800 nm from HRTEM images shown in Fig. 4a and b. After carbonization and calcination in different atmospheres, the mixed-MOFs were converted to ZMCN hybrid materials. The rods-like nanostructure was basically maintained but the surface of nanorods was rougher than the untreated as shown in Fig. 3c and d. There were vast microgrooves in the surface of nanorods due to heat treatment. As observed in the HRTEM images Fig. 4c and d, the hybrid materials nanorods were slightly longer and thinner than mixed-MOFs nanorods. which can be explained by the heterogeneous expansion during the heat treatment.[33] It is noteworthy that the ZMCN were consisted of a mass of nanoparticles with diameter of approximately 10 nm, this conversion should be attributed to the release of gaseous product and decomposition of organic linkers during pyrolysis process. As a result of this unique structure, the ZMCN possessed high surface area and the BET surface area was calculated to be 143.4 m2 g-1. The electrochemical properties of the as-obtained specimens were investigated in the standard three-electrode systems within the potential window of 0−1.2 V. The Fig. 5a reveals the CVs of ZMON and ZMCN at scan rate of 10 mV s-1. Compared with the CVs of ZMON, the CVs shape of hybrid materials are more similar to rectangle. It is obvious that the area of CVs for hybrid materials is larger than the ZMON, proving the remarkable capacitive properties. The CVs of the ZMCN hybrid materials with diverse scan rate from 10 to 100 mV s-1 are displayed in Fig. 5b. The shapes of each CV curves are similarly rectangular and the redox peaks are almost invisible, indicating the rapid successive surface redox reactions.[34] During the CVs test at various scan rates, it is hard to observe the release of gas on the electrodes and colour change of electrolyte, suggesting the superior stability of hybrid materials in broad 9

potential window. The Fig. 5c displays the comparison of the GCD curves of ZMON and ZMCN. It is apparent that hybrids materials possess higher capacity of energy storage. Based on the equipment mentioned above, the specific capacitance of ZMON and ZMCN is 217.5 F g-1, 589 F g-1 at 1 A g-1, respectively. The GCD curves of hybrid materials at different current densities are shown in Fig. 5d. Each curve of hybrid materials at different densities is similar isosceles and not strictly symmertrical, demonstrating the successive surface redox reactions. Due to reduction of interaction between Na+ ion and active materials on the current collector with increase of current density, the capacitance is decreased with relatively slight rates. Furthermore, it is noteworthy that the special capacitance is still reach 278 F g-1 when the current density rises to 20 A g-1, revealing the potential application value of the hybrid materials. The rate capability of the ZMCN hybrid materials and ZMON is investigated by testing with various current densities shown in Fig. 6a. The value of specific capacitance for hybrid materials is 589, 523.2, 489, 440.5, 364 and 278 F g-1, correspond to current densities of 1, 2, 3, 5, 10 and 20 A g-1. As can be obviously seen, the hybrid materials exhibit better rate capability than ZMON, which should be attributed to the highly electrolyte-accessible areas and short transfer path endowed by the porous and interconnected carbon support. In order to evaluate the application prospect of the hybrid materials, the cyclic stability was probed by GCD at current density of 10 A g-1 shown in Fig 6b. There is an increment of the specific capacitance for hybrids materials during the initial 500 cycles, and the specific capacitance finally reaches to 377.18 F g-1 from 364 F g-1. The probable reason for the increment should be related to the activation effect during the charge-discharge process and similar instances were extensively reported.[30, 35] After 2000 cycles, the capacitance of the hybrid materials remained 98.1% (357 F g-1) 10

of the premier value. As a contrast, the cyclic stability of ZMON was investigated in the uniform conditions. The increment is more distinct but the reserved capacitance only 77.1% of the premier. It can be confirmed that the incorporation with carbon materials endows the hybrid materials with remarkable cyclic stability. Compared with the previous report about ZnMn2O4 materials and other MOFs-derived materials, it is obvious that ZMCN exhibit significant electrochemical performance (table 1).[10, 11, 36-39] To probe the charge transfer and electrolyte diffusion, EIS were carried out within the frequency range from 0.01 Hz to 105 Hz at open-circuit potential. Fig. 6d displays the Nyquist plots of the ZMON and ZMCN, and the as-obtained equivalent circuit simulated by the Zview. (The Rs, Rct, CPE and W correspond to the resistance of the solution, the Faradaic interfacial charge transfer resistance, the constant phase element corresponding to the double-layer capacitor and the Warburg impedance, respectively.) It can be observed that the Nyquist plots are constituted with semicircle in high frequency region and straight lines in low frequency region. At the high frequency, the semicircle diameter of the hybrid is smaller than the ZMON, suggesting the higher transfer rate. The fitting results furtherly reveal that the charge transfer resistance of the ZMCN (0.36 Ω) is smaller than the ZMON (0.55 Ω). In addition, it is distinct that the solution resistance of the hybrid materials (1.94 Ω) is lesser than the ZMON (3.08 Ω). At the low frequency, the slope of the line for hybrid materials is larger than the ZMON, demonstrating the lower ion diffusive resistance. According to the results of electrochemical tests, it is obvious to confirm that the hybrid materials are benefitted from the unique 1D nanostructure and the synergistic effect. After all electrochemical measurement, the hybrid materials loaded on the platinum mesh electrode were retrieved via ultrasonication and characterized by TEM. 11

The Fig. 6d exemplify that micromorphology of ZMCN is basically maintained after cycles, there is almost negligible volume change and pulverization can be observed. This result turns out to be a direct proof of the stability and integrity of materials. The possible reasons for the remarkable electrochemical performance should be as follow: Firstly, the hybrid materials exhibit shorter electron transfer pathway and larger surface area due to the 1D nanostructure, which benefit to the capacitive behavior. Secondly, the porous nanostructure provides larger active contact area for the electrolyte ions to reduce the resistance of the hybrid materials. Thirdly, the carbon in nanorods endows the hybrid material with superior capacitive behavior and excellent conducting properties to ensure the rapid charge-discharge process. Finally, the carbon makes sure that the transition metal oxide is homogeneously dispersed in the nanorods and suppresses the volume change of the transition metal oxide during the redox process, which enhances the electrochemical stability. Aforesaid aspects lead to the superior electrochemical properties of the hybrid materials and increase the possibility of practical application.

4 Conclusions In summary, the ZnMn2O4/Carbon nanorods hybrid materials have been fabricated via directly calcining the mixed-MOFs nanorods in different atmosphere without extra carbon source. As the result of the unique 1D structure and synergistic effect, the ZMCN possesses remarkable potential as electrode materials in supercapacitors. The specific capacity of the hybrid materials final reaches to 589 F g-1 at 1 A g-1 within broad potential window. After 2000 cycles, 98.1 % of original capacitance has been remained. It is noteworthy that hybrid materials exhibit prominent rate capability at high current density, indicating the potential application 12

value. Furthermore, this facile strategy will offer a feasible approach to construct 1D nanorods structure spinel metal oxides/carbon hybrid materials from MOFs.

Acknowledgment This work was supported by the National Natural Science Foundation of China (Grant No. 51472070).

Reference [1] D.H. Chestnut, Ten years of experience with accidental dural puncture and post-dural puncture headache in a tertiary obstetric anaesthesia department, Yearbook of Anesthesiology and Pain Management, 2009 (2009) 252-253. [2] S. Zhu, M. Wu, M.-H. Ge, H. Zhang, S.-K. Li, C.-H. Li, Design and construction of three-dimensional CuO/polyaniline/rGO ternary hierarchical architectures for high performance supercapacitors, Journal of Power Sources, 306 (2016) 593-601. [3] X. Liu, C. Shi, C. Zhai, M. Cheng, Q. Liu, G. Wang, Cobalt-Based Layered Metal-Organic Framework as an Ultrahigh Capacity Supercapacitor Electrode Material, ACS Appl Mater Interfaces, 8 (2016) 4585-4591. [4] D. Ji, H. Zhou, J. Zhang, Y. Dan, H. Yang, A. Yuan, Facile synthesis of a metal–organic framework-derived Mn2O3nanowire coated three-dimensional graphene network for high-performance free-standing supercapacitor electrodes, J. Mater. Chem. A, 4 (2016) 8283-8290. [5] H. Gao, S. Cao, Y. Cao, Hierarchical Core-Shell Nanosheet Arrays with MnO 2 Grown on Mesoporous CoFe 2 O 4 Support for High-Performance Asymmetric Supercapacitors, Electrochimica Acta, 240 (2017) 31-42. [6] Y. Zhang, L. Li, H. Su, W. Huang, X. Dong, Binary metal oxide: advanced energy storage materials in supercapacitors, J. Mater. Chem. A, 3 (2015) 43-59. [7] M. Zhang, S. Guo, L. Zheng, G. Zhang, Z. Hao, L. Kang, Z.-H. Liu, Preparation of NiMn2O with large specific surface area from an epoxide-driven sol−gel process and its capacitance, Electrochimica Acta, 87 (2013) 546-553. [8] J. Pu, J. Wang, X. Jin, F. Cui, E. Sheng, Z. Wang, Porous hexagonal NiCo 2O4 nanoplates as electrode materials for supercapacitors, Electrochimica Acta, 106 (2013) 226-234. [9] Y. Guan, Y. Feng, Y. Mu, L. Fang, H. Zhang, Y. Wang, Ultra-tiny ZnMn2O4 nanoparticles encapsulated in sandwich-like carbon nanosheets for high-performance supercapacitors, Nanotechnology, 27 (2016) 475402. [10] T. Huang, C. Zhao, Z. Qiu, J. Luo, Z. Hu, Hierarchical porous ZnMn 2O4 synthesized by the sucrose-assisted combustion method for high-rate supercapacitors, Ionics, 23 (2016) 139-146. [11] N. Guo, X.Q. Wei, X.L. Deng, X.J. Xu, Synthesis and property of spinel porous ZnMn2O4 microspheres, Applied Surface Science, 356 (2015) 1127-1134. [12] K. Xu, X. Yang, J. Yang, J. Hu, Synthesis of hierarchical Co 3O4@NiCo2O4 core-shell nanosheets as electrode materials for supercapacitor application, Journal of Alloys and Compounds, 700 (2017) 247-251. [13] D. Kong, W. Ren, C. Cheng, Y. Wang, Z. Huang, H.Y. Yang, Three-Dimensional NiCo2O4@Polypyrrole Coaxial Nanowire Arrays on Carbon Textiles for High-Performance Flexible Asymmetric Solid-State Supercapacitor, ACS Appl Mater Interfaces, 7 (2015) 21334-21346. [14] C. Zhou, X. Chen, H. Liu, J. Zhou, Z. Ma, M. Jia, H. Song, Heteroatom-doped multilocular carbon nanospheres with high surface utilization and excellent rate capability as electrode material for supercapacitors, Electrochimica Acta, 236 (2017) 53-60. 13

[15] A. Singh, A. Chandra, Significant Performance Enhancement in Asymmetric Supercapacitors based on Metal Oxides, Carbon nanotubes and Neutral Aqueous Electrolyte, Sci Rep, 5 (2015) 15551. [16] K. Krishnamoorthy, G.K. Veerasubramani, P. Pazhamalai, S.J. Kim, Designing two dimensional nanoarchitectured MoS2 sheets grown on Mo foil as a binder free electrode for supercapacitors, Electrochimica Acta, 190 (2016) 305-312. [17] M. Huang, K. Mi, J. Zhang, H. Liu, T. Yu, A. Yuan, Q. Kong, S. Xiong, MOF-derived bi-metal embedded N-doped carbon polyhedral nanocages with enhanced lithium storage, Journal of Materials Chemistry A, 5 (2017) 266-274. [18] G. Ma, S. Li, W. Zhang, Z. Yang, S. Liu, X. Fan, F. Chen, Y. Tian, W. Zhang, S. Yang, M. Li, A General and Mild Approach to Controllable Preparation of Manganese-Based Micro- and Nanostructured Bars for High Performance Lithium-Ion Batteries, Angew Chem Int Ed Engl, 55 (2016) 3667-3671. [19] F. Bella, A. Lamberti, A. Sacco, S. Bianco, A. Chiodoni, R. Bongiovanni, Novel electrode and electrolyte membranes: Towards flexible dye-sensitized solar cell combining vertically aligned TiO2 nanotube array and light-cured polymer network, Journal of Membrane Science, 470 (2014) 125-131. [20] Z. Yu, L. Tetard, L. Zhai, J. Thomas, Supercapacitor electrode materials: nanostructures from 0 to 3 dimensions, Energy Environ. Sci., 8 (2015) 702-730. [21] S. Peng, L. Li, Y. Hu, Fabrication of Spinel One-Dimensional Architectures by Single-Spinneret Electrospinning for Energy Storage Applications, ACS NANO, 9 (2015) 1945-1954. [22] W. Shaheen, M.F. Warsi, M. Shahid, M.A. Khan, M. Asghar, Z. Ali, M. Sarfraz, H. Anwar, M. Nadeem, I. Shakir, Carbon Coated MoO3 Nanowires/Graphene oxide Ternary Nanocomposite for High-Performance Supercapacitors, Electrochimica Acta, 219 (2016) 330-338. [23] Z. Xie, W. Xu, X. Cui, Y. Wang, Recent Progress in Metal-Organic Frameworks and Their Derived Nanostructures for Energy and Environmental Applications, ChemSusChem, 10 (2017) 1645-1663. [24] A. Jayakumar, R.P. Antony, R. Wang, J.M. Lee, MOF-Derived Hollow Cage Nix Co3-x O4 and Their Synergy with Graphene for Outstanding Supercapacitors, Small, 13 (2017). [25] D. Ji, H. Zhou, Y. Tong, J. Wang, M. Zhu, T. Chen, A. Yuan, Facile fabrication of MOF-derived octahedral CuO wrapped 3D graphene network as binder-free anode for high performance lithium-ion batteries, Chemical Engineering Journal, 313 (2017) 1623-1632. [26] J. Zhang, M. Huang, B. Xi, K. Mi, A. Yuan, S. Xiong, Systematic Study of Effect on Enhancing Specific Capacity and Electrochemical Behaviors of Lithium-Sulfur Batteries, Advanced Energy Materials, 8 (2018) 1701330. [27] Kathryn M. L. Taylor, William J. Rieter, W. Lin, Manganese-Based Nanoscale Metal−Organic Frameworks for Magnetic Resonance Imaging, J Am Chem Soc, 130 (2008) 14358-14359. [28] X. Huang, Y. Chen, Z. Lin, X. Ren, Y. Song, Z. Xu, X. Dong, X. Li, C. Hu, B. Wang, Zn-BTC MOFs with active metal sites synthesized via a structure-directing approach for highly efficient carbon conversion, Chem Commun (Camb), 50 (2014) 2624-2627. [29] F. Zheng, G. Xia, Y. Yang, Q. Chen, MOF-derived ultrafine MnO nanocrystals embedded in a porous carbon matrix as high-performance anodes for lithium-ion batteries, Nanoscale, 7 (2015) 9637-9645. [30] B. Fan, A. Hu, X. Chen, S. Zhang, Q. Tang, J. Wang, W. Deng, Z. Liu, K. Xiao, Hierarchical Porous ZnMn 2 O 4 Microspheres as a High-Performance Anode for Lithium-Ion Batteries, Electrochimica Acta, 213 (2016) 37-45. [31] S. Nagamuthu, S. Vijayakumar, S.-H. Lee, K.-S. Ryu, Hybrid supercapacitor devices based on MnCo2O4 as the positive electrode and FeMn2O4 as the negative electrode, Applied Surface Science, 390 (2016) 202-208. [32] R. R., Salunkhe, Jing Tang, Yuichiro Kamachi, Teruyuki Nakato, Jung Ho Kim, Yusuke Yamauchi, Asymmetric Supercapacitors Using 3D Nanoporous Carbon and Cobalt Oxide Electrodes Synthesized from a Single Metal–Organic Framework, ACS Nano, 9 (2015) 6288-6296. [33] H. Pang, B. Guan, W. Sun, Y. Wang, Metal-Organic-Frameworks Derivation of Mesoporous NiO Nanorod for High-Performance Lithium Ion Batteries, Electrochimica Acta, 213 (2016) 351-357. [34] Patrice Simon, Y. Gogotsi, Materials for electrochemical capacitors, Nature Materials, 7 (2008) 845-854. [35] T.Y. Wei, C.H. Chen, H.C. Chien, S.Y. Lu, C.C. Hu, A cost-effective supercapacitor material of ultrahigh specific capacitances: spinel nickel cobaltite aerogels from an epoxide-driven sol-gel process, Adv Mater, 22 (2010) 347-351. [36] A. Sahoo, Y. Sharma, Synthesis and characterization of nanostructured ternary zinc manganese oxide as novel supercapacitor material, Materials Chemistry and Physics, 149-150 (2015) 721-727. [37] D. Ji, H. Zhou, J. Zhang, Y. Dan, H. Yang, A. Yuan, Facile synthesis of a metal–organic 14

framework-derived Mn2O3 nanowire coated three-dimensional graphene network for high-performance free-standing supercapacitor electrodes, J. Mater. Chem. A, 4 (2016) 8283-8290. [38] S. Chen, M. Xue, Y. Li, Y. Pan, L. Zhu, D. Zhang, Q. Fang, S. Qiu, Porous ZnCo2O4nanoparticles derived from a new mixed-metal organic framework for supercapacitors, Inorg. Chem. Front., 2 (2015) 177-183. [39] J.W. Jeon, R. Sharma, P. Meduri, B.W. Arey, H.T. Schaef, J.L. Lutkenhaus, J.P. Lemmon, P.K. Thallapally, M.I. Nandasiri, B.P. McGrail, S.K. Nune, In situ one-step synthesis of hierarchical nitrogen-doped porous carbon for high-performance supercapacitors, ACS Appl Mater Interfaces, 6 (2014) 7214-7222.

15

Table 1. The comparison of specific capacitance hybrid materials and other reported materials

No.

Composites

Specific Capacitance

Cycle Stability

References

88.32% 4000 cycles

10

~92% 1100 cycles

11

--

34

--

35

97.9% 1500 cycles

36

--

37

98.1% 2000 cycles

This work

411.75 F g-1 at 1A g-1 1

Hierarchical porous ZnMn2O4 from 0 to 0.6 V 155 F g-1 at 2 mV s-1

2

Porous ZnMn2O4 microspheres from -0.1 to 0.5 V 160 F g-1 at 3 mV s-1

3

Nanostructured ZnMn2O4 from -0.1 to 0.45 V 471.1 F g-1 at 0.2 A g-1

4

MOF-derived Mn2O3 nanowire/3D graphene from 0 to 0.8 V 451 F g-1 at 0.5 mV s-1

5

MOF-derived porous ZnCo2O4 nanoparticles from 0.05 to 0.45 V 239 F g-1 at 5 mV s-1

6

MOF-derived N-doped porous carbon from 0 to 1 V 589 at 1 A g-1

7

MOF-derived ZnMn2O4/C nanorods from 0 to 1.2 V

16

Fig.1. XRD patterns of the Mixed-MOFs, ZnMn2O4 nanrods and ZnMn2O4/carbon nanorods hybrid materials.

Fig.2. (a) XPS survey spectrum of ZnMn2O4/carbon nanorods hybrid materials, high resolution spectrum for (b) Zn 2p, (c) Mn 2p, (d) C 1s and (e) O 1s. 17

Fig.3. FESEM images of (a) (b) mixed-MOFs, (c) (d) ZnMn2O4/carbon nanorods

Fig.4. HRTEM images of (a) (b) mixed-MOFs, (c) (d) ZnMn2O4/carbon nanorods.

18

Fig.5. (a) CV curves of the ZMON, ZMCN at scan rate of 10 mV s-1, (b) CV curves of the ZMCN, (c) GCD curves of the ZMON, ZMCN at current density of 1 A g-1 and (d) GCD curves of the ZMCN.

Fig.6. (a) Specific capacitance as a function of the current density of the electrodes of the ZMON and the ZMCN, (b) the cyclic stability of the ZMON and the ZMCN, (c) Nyquist plot of the ZMON and the ZMCN, and (d) HRTEM of the ZMCN after cycles. 19