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High-Performance Supercapacitor Electrode based on Cobalt Oxide - Manganese Dioxide -Nickel Oxide Ternary 1D Hybrid Nanotubes Ashutosh Kumar Singh, Debasish Sarkar, Keshab Karmakar, Kalyan Mandal, and Gobinda Gopal Khan ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b05933 • Publication Date (Web): 19 Jul 2016 Downloaded from http://pubs.acs.org on July 21, 2016

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ACS Applied Materials & Interfaces

High-Performance Supercapacitor Electrode based on Cobalt Oxide - Manganese Dioxide -Nickel Oxide Ternary 1D Hybrid Nanotubes Ashutosh K. Singh,1, 2, ‡ Debasish Sarkar,3, ‡,* Keshab Karmakar,2 Kalyan Mandal,2 and Gobinda Gopal Khan4,* 1

Large Area Device Laboratory, Centre for Nano and Soft Matter Sciences, Jalahalli, Bengaluru 560013, India

2

Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake City, Kolkata 700106, India

3

Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, India 4

Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, Technology Campus, Block JD2, Sector III, Salt Lake City, Kolkata 700106, India

Keywords: Nanotubes, ternary, electrodeposition, diffusion, supercapacitor Abstract We report a facile method to design Co3O4-MnO2-NiO ternary hybrid 1D nanotube arrays for their application as an active material for high-performance supercapacitor electrode. This as-prepared novel supercapacitor electrode can store charge as high as ~ 2020 C/g (equivalent specific capacitance ~ 2525 F/g) for a potential window of 0.8V, has long cycle

stability

(nearly

80%

specific

capacitance

retains

after

successive

5700

charge/discharge cycle), significantly high coulombic efficiency and fast response time (~ 0.17s). The remarkable electrochemical performance of this unique electrode material is the outcome of its enormous reaction platform provided by its special nanostructure morphology and conglomeration of the electrochemical properties of three highly redox active materials in a single unit.

____________________________ *

Author to whom correspondence should be addressed. E-mail: [email protected], Tel: +91 (080) 2293 2945; and E-mail:[email protected], Tel: +91 (033) 2335 0067, ‡ Authors contributed equally to this work. 1 ACS Paragon Plus Environment


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Introduction Since last few years, the hassle of clean, efficient, and renewable energy sources is remarkable and thereby driving intense scientific concern in the production, storage and management of this precious energy.1,2 Among variety of electrical energy storage devices, supercapacitors (SCs), also known as electrochemical capacitors, have drawn enormous research and industrial attention because of their high power density and very long cycle stability ascompared to their counterparts such as batteries, fuel cells and conventional capacitors etc.3,4 Initially, some carbon-based electrode materials like activated carbon, carbon nanotubes, and graphene3,5,6 have been used as electrode materials, under the category of electric double layer capacitors (EDLC). Later, transition metal oxides (TMOs) like RuO2, MnO2, Fe2O3, NiO and Co3O4 etc. and conducting polymers specially PANI

3,5,6

have been

investigated thoroughly because of their very high specific capacitance resulting from unique redox reactions at the electrode and electrolyte interface and thus categorized as supercapacitors. In particular, Co3O4, MnO2, and NiO have exhibited immense potential as electro-active material in improving the performance of SCs because of their high theoretical specific capacitances, environmental compatibility, mechanical and thermal stability. Moreover, their natural abundance makes them economical as compared to other TMOs like RuO2.3,7 However, high resistivity of the TMO’s electrodes is a big challenge for their application in high-performance SCs. The electrical conductivity of TMOs can be improved by introducing vacancies or impurities, via sintering in the selected gaseous environment or through doping.8-11 Recently, it has been established that the electrical conductivity in TMOs electrodes could be enhanced by mixing one metal oxide material with other metal oxide material. This process augments the charge movement though their synergistic effect, which affects the reactions at the electrode-electrolyte interface facilitating charge transportation towards current collector improving the charge storage performance.12, 13 Different hybrid

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TMOs (binary and ternary) nanostructures have been established as the promising supercapacitor electrodes such as, NiCo2O4 nanowires, nanorods, and aerogels

14-16

Ni–Co

double hydroxide,17 Co3O4@MnO2 core-shell,18 NiO/Ni core-shell,19 Ni(OH)2−MnO2graphene oxide,20 NiCo2O4@MnO2 core-shell,21 α-MnO2/δ-MnO2 Core–Shell,22 and V2O5/polyindole composite.23 Different morphologies of nanostructures like nano-hollowspheres, nano-rods, nano-belts, nano-needles, nano-sheets, nano-flowers, nanowires, and nanotubes (NTs)3,5-7,14-23 of various TMOs have been designed to enhance their electrochemical performance. Interestingly, among different nanostructures, NTs have shown superiority because of their unique 1D structure having large accessible inner and outer surfaces, which serve as a feasible platform for redox reactions to boost the performance of the electrode with fast charge transportation.24-26 In this backdrop, we have employed a facile technique to grow free standing vertically aligned arrays of highly porous 1D Co3O4-MnO2-NiO composite NTs on conducting gold substrate for the fabrication of SC electrode (see Supporting Information for details). Figure 1 displays the schematics of the fabrication process of 1D Co3O4-MnO2-NiO ternary hybrid NTs arrays by using nanoporous anodic aluminium oxide (AAO) template. The growth mechanism of the 1D Co3O4-MnO2-NiO ternary hybrid NTs is elaborated in Supporting Information. The 1D Co3O4-MnO2-NiO ternary hybrid NTs have several scientific advantages: (i) 1D nano-tubular structure having large surface area with proper use of both of the inner and outer surfaces as well as their highly porous walls would enhance the effective accessible surface area of electrodes providing huge platform for surface based faradaic reactions; (ii) thin walls of NTs would provide short ion/electron diffusion path; (iii) combination of three highly redox active oxides (Co3O4, MnO2 and NiO) in a single nanostructure would definitely improve the charge storing capacity of the whole system because of synergistic effect; and (iv) direct growth of NTs on current collector (Au) would



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significantly improve the electrical conductivity of the entire electrode by reducing contact resistance and also eliminates the use of expensive and resistive binders, which causes extra weight to the electrode. As expected, SC electrode containing highly ordered, vertically aligned, porous 1D ternary hybrid NTs arrays demonstrates superior electrochemical performance with high specific capacitance (~ 2525 F/g within 0.8V potential window), excellent long cycle stability, high energy and power density, which are because of the unique design of the electrode together with the synergestic combination of three component TMOs in a single unit.

Figure 1. Schematic of the fabrication of ordered arrays of 1D Co3O4-MnO2-NiO hybrid NTs. Results and discussion Field emission scanning electron microscope (FESEM) image of the as-prepared 1D Co3O4-MnO2-NiO ternary hybrid NTs arrays is shown in Figure 2a. From the figures, it is evident that high density well aligned arrays of NTs have been formed uniformly throughout the whole substrate during the electrode position process (Figure S1 and S2 in Supporting Information). Average length and outer diameter of these NTs are uniform and found to be approximately 12 µm and 125 nm, respectively. The wall thickness of the NTs is ~ 10-15 nm only. The tubular nature of the as-prepared hybrid NTs is further explored by transmission electron microscope (TEM) and the corresponding micrograph for the hybrid NTs is shown


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in Figure 2b.TEM image displays solid tube wall (dark contrast) and voidcenter of the tubes (bright contrast), clearly confirms the formation of NTs (wall thickness ~ 12-15 nm) with huge surface roughness, which would enlarge the active surface area of the electrode, as discussed later. Further, the crystal structure of 1D Co3O4-MnO2-NiOternary hybrid NTs has been investigated by high-resolution TEM (HRTEM) (see Figure 2c), selected area electron diffraction (SAED) (Figure S3, Supporting Information) and x-ray diffraction (XRD) (Figure S4, Supporting Information) techniques which confirm the polycrystalline nature of these NTs. Three different sets of lattice fringes can be observed in the HRTEM image with lattice spacing nearly ~ 0.28, 0.268 and 0.24 nm, which correspond to the d-spacing of the (111) planes of NiO, (102) planes of MnO2 and (220) planes of Co3O4, respectively. Moreover, the XRD pattern illustrates diffraction peaks that can be indexed perfectly with corresponding lattice planes of NiO, MnO2, and Co3O4conforming the formation of ternary hybrid NTs of TMOs. However, the Au peak in the XRD pattern comes from metallic Au substrate underneath the hybrid NTs.

Figure 2. (a) FESEM image of the as-prepared Co3O4-MnO2-NiO ternary hybrid NTs, inset shows the side view of the NTs, (b) TEM image, (c) HRTEM image and (d)-(g) energy



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filtered TEM (EFTEM) images for individual components (Co, Mn, Ni and O) comprising the ternary hybrid NTs. Furthermore, elemental distribution throughout the 1D Co3O4-MnO2-NiOhybrid NTs has been examined by energy-filtered TEM (EFTEM), as shown in Figure 2d-2g, clearly indicate uniform distribution of metallic components and also oxygen ion present in the NTs. However, higher intensity of the Co, Mn, Ni and O at the surface as compared to the central portion of the nanostructure confirms the formation of uniform nano-tubes. We also have employed energy-dispersive x-ray spectroscopy (EDS) and the X-ray photoelectron spectroscopy (XPS) to verify the elemental composition and chemical states of the assynthesized1D Co3O4-MnO2-NiO ternary hybrid NTs, respectively. EDS spectrum (Figure S5 in Supporting Information) shows the presence of Co, Mn, Ni and O elements in the hybrid NTs, whereas the weight ratio of Co, Mn and Ni is found to be 1.1:1.2:1. Core level XPS spectrum (Figure S6 in Supporting Information) of Co 2p shows two peaks of Co 2p3/2 and Co 2p1/2 observed at the binding energies of 780.4 and 795.5 eV, respectively, suggest the Co2+ state, whereas two small peaks at 788.9 and 804 eV could be attributed to 2p3/2 and 2p1/2 of Co3+, respectively, indicating the presence of Co3O4 phase in this hybrid nanotube.27,28 Deconvolution of Mn 2p core level spectrum gives two distinct peaks at 642.1 and 653.4 eV with a spin-orbital splitting of 11.3 eV, which corresponds well to Mn 2p3/2 and Mn 2p1/2 of MnO2, respectively.27,29 Similarly, Ni 2p core level spectrum displays Ni 2p3/2 and Ni 2p1/2 peaks at binding energies of 855 and 872 eV, respectively, with the spin-orbital splitting of ~ 17 eV, confirming the divalent (+2) oxidation state of Ni in 1D Co3O4-MnO2-NiO hybrid NTs.30 Moreover, the presence of the satellite peak at ~ 861 eV again indicates 2+ oxidation state of Ni. The O1s core level XPS spectrum has two distinct component peaks at ~ 529.6 and 531.5 eV, which could be assigned to the oxygen present in the oxides of Co3O4, MnO2,


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and NiO and the oxygen atoms in hydroxyl groups or oxygen vacancy defects incorporated on the surface of NTs, respectively. Electrochemical performance of the as-prepared 1D Co3O4-MnO2-NiOhybrid NTs was investigated in three-electrode configuration by cyclic voltammetry (CV) and galvanostatic charge/discharge methods. The typical three-electrode cell consisted of the 1D Co3O4-MnO2-NiO ternary hybrid nanotubes, Ag/AgCl, and Pt electrodes as working, reference and counter electrodes, respectively, dipped in 1M aqueous KOH solution at room temperature. The CV curves of the as-prepared Co3O4-MnO2-NiO ternary hybrid NTs electrode at different scan rates are shown in Figure 3a, where the current increases sharply with increasing scan rate. However, the shape of the CV curves remains almost similar at all scan rates, suggesting good reversibility nature of the hybrid NTs electrode. The shape of the CV curves as observed in each CV curve suggests charge storage mechanism of Co3O4MnO2-NiO ternary hybrid NTs electrode via surface bound faradic reactions governed by inter conversion of various oxidation states of metal ions together with K+ ion intercalation/deintercalation process into/from oxide nanostructure.31, 32 The area under the CV curve represents total charge originating through faradaic and non-faradaic processes; faradaic contribution involves ion intercalation together with surface bound redox capacitance whereas non-faradaic process arises from double layer effect.33 These effects can be explained by analysing CV curves at different scan rates (v) using the power law: i = avb , where aand b are two adjustable parameters33,34 and accordingly parameter b can be calculated from the slope of the plot of log i vs log v. Generally, for ideal diffusion controlled faradaic process, slope b = 1/2 and it satisfies Cottrell’s equation: i = v1/2 ,35 whereas slope b = 1 represents purely capacitive response (redox capacitance plus double layer capacitance) because the capacitive current is proportional to the potential sweep rates: i = vCd A , Cd being the capacitance and A is the surface area of the electrode material.35 Hence, one can expect 7 ACS Paragon Plus Environment


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dominant capacitive charging at higher scan rates because of stronger linear dependence, whereas diffusion process will dominate more at lower sweep rates. Moreover, slope b, as obtained by plotting log i against log v at different voltages (V), shows a value ~ 0.5 at peak potentials suggesting dominance of diffusion-limited charge storage process, whereas at other potentials slope value is ~ 1 indicating that the current is predominantly capacitive, as shown in Figure 3b. Now, from CV curves capacitance (C) values are calculated using the equation: C = q / V = ∫ idt / V , where q is the charge stored, I is the current and V is the potential

window. In accordance with our arguments, we have observed a sharp increase in capacitance with decreasing sweep rates, a maximum value of ~ 1247 F/g (~ 555.5 mF/cm2) being attained at a scan rate of 2 mV/s (as shown in Figure S7, Supporting Information). It is mainly because of the formation of porous and spongy surface of this Co3O4-MnO2NiOternary hybrid NTs array that provide enormous and accessible inner surfaces of the nanostructure for effective diffusion controlled faradaic reactions at lower sweep rates. However, at higher scan rates, only non-diffusion controlled capacitive charging process dominates over intercalation capacity, that reduces the overall capacitance of hybrid NTs electrodes (~384.5 F/g at a scan rate of 100 mV/s).


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25

(a)

2 mV/s 5 mV/s 10 mV/s 25 mV/s 50 mV/s 100 mV/s

15 10 5

1.0

(b)

Anodic sweep Cathodic sweep

0.9

'b'- values

20

0 -5

0.8 0.7 0.6 0.5

-10 -15

0.4 -0.2

0.0

0.2

0.4

0.6

-0.2 -0.1 0.0

Potential (V) vs Ag/AgCl

q* (C/g)

1000

0.002

1/q*(v) = 1/q*total + (const.) v1/2

0.001

0.1

0.2

0.3

0.4

0.5

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Voltage (V)

(c)

0.003

1/q* (C-1.g)

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Current density (mA/cm2)

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(d)

100

q*(v) = q*outer + (const.) v-1/2

q*total = 2020.20 C/g

q* outer = Intercept = 282.81 C/g

0.000

10 0

2

4 1/2

6

8

10

0.2

0.3

1/2

v (mV/s)

0.4

v

-1/2

0.5

0.6

0.7

-1/2

(mV/s)

Figure 3. (a) Cyclic voltammetry curves recorded at various scan rates, (b) variation of slope ‘b’ as a function of voltage (V)for cathodic and anodic sweeps of CV cycles,and Trasatti plots: (c) plot of 1/q* against v1/2 to find the total charge (q*total) stored by the electrode material. (d) shows the plot of q* against v – 1/2 to quantify the charge stored only on the outer surface of the electrode material (q*outer). Now, as ion intercalation at lower sweep rates enhances charge storage capacity drastically, so it would be interesting to investigate the maximum charge that can be stored in this ternary hybrid NTs array and also the actual electrochemical surface area leading to total charge storage. The overall or complete charge stored in the electrode material can be calculated using the procedure given by Trasatti et al.,36 which involves the determination of total charge stored (q*total) from the intercept of the linear plot of 1/q* against v1/2, as shown in Figure 3c. This procedure can also be used to determine the charge stored only at the outer surface (q*outer) of the electrode material from the intercept of the linear plot of q* against v– 9 ACS Paragon Plus Environment


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1/2 33

, as shown in Figure 3d. Interestingly, the value of maximum charge that can be stored

within this ternary hybrid nanostructure is found to be 2020.20 C/g, equivalent to a specific capacitance of 2525.25 F/g for a potential window of 0.8V. Similarly, the charge stored on the outer surface is found to be 282.8 C/g with an equivalent capacitance of 353.5 F/g. Moreover, the charge stored in the inner surface (q*inner) is the difference between the total charge (q*total) and charge stored on the outer surface (q*outer), is found to be 1737.4 C/g (~ 2171.8 F/g). The high charge storage capacity of the electrode can be attributed to the porous, spongy and tubular structure of these ternary NTs that provides enormous inner and outer surface for both faradaic and non-faradaic processes at lower as well as at higher potential sweep rates, as discussed earlier. To further illustrate the capacitive performance of the Co3O4-MnO2-NiO ternary hybrid NTs, galvanostatic charge/discharge was performed within the potential window between -0.2V and 0.6V at different current densities and corresponding charge/discharge curves at some selected current densities are shown in Figure 4a. At lower current densities, charging profile shows non-linear and sluggish behavior, which are due to the diffusioncontrolled faradaic process together with purely capacitive charging. Interestingly, discharge profile shows two prominent regions, the first one after the IR-drop characterized by a linear discharge region can be attributed to the release of charges from the surface or near surface regions of the electrode material, i.e. capacitive discharge. However, the second region that is characterized by a very slow and extended discharge tail is mainly because of de-intercalation of diffused ions from the innermost portions of electrode material, i.e. diffusion controlled discharge profile. Such behavior of charge/discharge curves is consistent with their CV profiles at lower potential sweep rates. Moreover, at higher discharge currents, although the discharge profile shows the first linear region, however, the slow discharge tail has reduced significantly, which is mainly because of the availability of charges stored only at the surface


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or near-surface regions of the electrode material at higher currents, i.e. discharge becomes non-diffusion controlled and more capacitive with the increase in current. From the discharge profiles of charge/discharge curves, capacitance values for this Co3O4-MnO2-NiO ternary hybrid nanotubes electrode have been calculated using equation: C = i∆t / ∆V , (where, I is the discharge current,and ∆t be the discharge time for potential window ∆V) and plotted against current density in Figure 4b. The nanotube hybrid electrode exhibits a specific capacitance of ~ 1224.5 F/g (~ 544.9 mF/cm2) at a current density of 12.2 A/g (~5.4 mA/cm2) and retains a value of 397.5 F/g (~176.9 mF/cm2) as the current density reaches at ~ 18.4 A/g (~ 8.2 mA/cm2). It is noteworthy that, here we have chosen a limited range of current densities so as to observe the changeover in charge storage mechanism from diffusion limited to diffusion independent. However, the value of capacitances obtained for this hybrid nanotubes electrode is higher than previously reported transition metal oxides and their mixed composites incorporated with conductive polymers and carbon-based materials.20-22,31,32,37-48 A comparison among the present 1D ternary NTs electrode materials to other transition metal oxides (binary and ternary) hybrid nanostructure electrodes are presented in the Supporting Information (Table S1).


Potential (V) vs Ag/AgCl

0.8

12.2 A/g

0.6 0.4

14.3 A/g 18.4 A/g

0.2 0.0 -0.2 0

25

50

75

1400

600

(b) 500

1200

400

1000

300

800

200 600 100 400 0

100 125 150 175 200

12

13

Time (s)

40

80

f0 = 5.72 Hz

-10

τ0 = 0.17 s

-20 -30 -40

40

-50

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103

104

Frequency (Hz)

0 0

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200

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17

18

19

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Z' (Ω Ω)

(d) Potential (V) vs Ag/AgCl

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120

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Z(Ω)

-Z'' (Ω Ω)

100 80

15

Current density (A/g)

(c) 160

14

0

0.6

~92%

80

~80%

60

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0.0 -0.2

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303350

303450

Time (s) 1000 2000 3000 4000 5000 6000

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120

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Specific capacitance (F/g)

(a)

Phase angle (degree)

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Areal capacitance (mF/cm2)


Cycle number

Figure 4. (a) Galvanostatic charge/discharge curves for Co3O4-MnO2-NiO hybrid NTs electrode within voltage window of -0.2 to 0.6 V; (b) variation of areal and specific capacitances with current densities, calculated from the discharge profile; (c) Nyquist plot (Z′′ vs. Z′ plot) for the hybrid electrode within the frequency range of 1 Hz to 100 kHz, inset shows the Bode plot to find out response time of this hybrid NTs electrode and (d) shows cycling performance and coulombic efficiency during 5700 charge/discharge cycles while inset figure shows last five charge/discharge cycles. Energy (E) and power (P) densities for the ternary hybrid NTs electrode have been 2 calculated using equations E = 1/ 2CV and P = E / ∆t , respectively, where the parameters

have their usual meanings. This nanostructured electrode demonstrates an energy density as high as 108.8 Wh/kg at a current density of 12.2 A/g (based on the mass of the active material only). Moreover, maximum power density that has been achieved is ~ 8 kW/kg with a corresponding energy density of 35.3 Wh/kg when current density reaches at 18.4 A/g, thus 12 ACS Paragon Plus Environment

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showing remarkable energy and power performance of the hybrid NTs electrode. We have also performed electrochemical impedance spectroscopy and corresponding Nyquist plot (-Z′′ vs Z′ plot) is depicted in Figure 4c. The intercept of the Nyquist curve with the real axis at high-frequency regime provides equivalent series resistance (ESR) which is found to be ~ 3.55 Ω for this hybrid NTs electrode, showing the low resistance of the electrolyte and good electrical contact between the electrode material and the substrate. Moreover, the capacitive response frequency (f0) for this electrode as calculated from the Bode plot (as shown in the inset of Figure 4c) at a phase angle of -450 is found to be 5.72 Hz, gives a response time (τ0 = 1/f0) as small as 0.17s, again suggesting fast charge/discharge characteristics of this ternary hybrid NTs electrode. The cycling stability and coulombic efficiency of the Co3O4-MnO2-NiO ternary hybrid NTs electrode were investigated at a current density of 15 A/g during 5700 charge/discharge cycles are shown in Figure 4d and the charge-discharge profiles for last five cycles are shown in the inset of Figure 4d. The electrode exhibits an exceptional cycling stability with 80% retention of its initial capacitance and a coulombic efficiency of almost 92% after 5700 cycles, suggesting stable electrochemical behavior of the hybrid NTs electrode

during

long-cycle

test.

Drop

in

specific

capacitance

following

5700

charge/discharge cycles might be due to the bulging of the electrode material resulted from continual ion intercalation/deintercalation process during long charge/discharge cycles. However, FESEM micrograph of the 1D ternary hybrid NTs hardly shows any change in tubular morphology after long cycling test (Figure S8, Supporting Information), indicating good structural stability of the electrode material during cycling test. Nonetheless, such high specific capacitance, high energy/power density and fast response time, i.e. worthy capacitive performance of the Co3O4-MnO2-NiO hybrid NTs electrode can mostly attributable to the well planned nano-architectural designing of electrode based on three highly electroactive



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materials that offers huge surface area (having highly porous inner and outer surface of the NTs) for fast faradaic and non-faradaic process. Additionally, direct growth of electroactive materials on conducting substrate provides enough structural integrity to sustain long charge/discharge cycles and also reduces the internal resistance to facilitate electron transfer towards the current collector boosting the performance of the electrode. Conclusion: In conclusion, a novel 1D architecture of Co3O4-MnO2-NiOternary hybrid nanotube (NT) arrays with remarkable capacitive performance has been demonstrated. These hybrid nanotubes are fabricated by combining simple template based electrochemical deposition of Co-Mn-Ni alloy NTs followed by controlled oxidation. The unique nano-architectural design of this hybrid NTs electrode having large accessible inner and outer surface area and small ion diffusion path coupled with synergy effects from three highly redox active materials grown on a highly conducting metal substrate facilitating fast charge transport helps to achieve enhanced electrochemical properties of this hybrid NT array suitable for supercapacitor applications. ASSOCIATED CONTENT Supporting Information. Additional details, including synthesis procedures, experimental methods, growth mechanism, SEM images of Co-Mn-Ni alloy NTs, Co3O4-MnO2-NiO NTs before and after long term cycling, XRD, SAED, EDS, XPS analyses, and capacitance vs. scan rate graph for Co3O4-MnO2-NiO NTs arrays. AUTHOR INFORMATION Corresponding authors: *E-mail: [email protected], Tel: +91 (080) 2293 2945 (D. Sarkar). 14 ACS Paragon Plus Environment

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E-mail:[email protected], Tel: +91 (033) 2335 0067 (G. G. Khan). Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS Author Debasish Sarkar is thankful to the Department of Science and Technology (DST), Government of India, for providing research support through the ‘INSPIRE Faculty Award’ (IFA14-MS-32). Author Gobinda Gopal Khan is thankful to the Department of Science and Technology (DST), Government of India, for providing research support through the ‘INSPIRE Faculty Award’ (IFA12-ENG-09). This work was supported by the start-up research grant (No. SB/FTP/ETA-0142/2014) from Science and Engineering Research Board (SERB), Government of India. REFERENCES (1) Miller, J. R.; Simon, P. Electrochemical Capacitors for Energy Management. Science, 2008, 321, 651-652. (2) Chmiola, J.; Largeot, C.; Taberna, P. L.; Simon, P.; Gogotsi, Y. Monolithic CarbideDerived Carbon Films for Micro-Supercapacitors. Science, 2010, 328, 480-483. (3) Simon, P.; Gogotsi, Y. Materials for Electrochemical Capacitors. Nat. Mater. 2008, 7, 845-854. (4) Guo, G.; Huang, L.; Chang, Q.; Ji, L.; Liu, Y.;Xie, Y.; Shi W.; Jia, N. Sandwiched Nanoarchitecture of Reduced Graphene Oxide/ZnO Nanorods/Reduced Graphene Oxide on Flexible PET Substrate for Supercapacitor. Appl. Phys. Lett., 2011, 99, 083111-083113. (5) Wang, G.; Zhang, L.; Zhang, J. A Review of Electrode Materials for Electrochemical Supercapacitors. Chem. Soc. Rev., 2012, 41, 797-828. (6) Zhi, M.; Xian, C.; Li, J.; Li, M.; Wu, N. Nanostructured Carbon–Metal Oxide Composite Electrodes for Supercapacitors: A Review. Nanoscale, 2013, 5, 72-88.



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

Page 16 of 20

(7) Zhang, G.; Lou, X. W. Controlled Growth of NiCo2O4 Nanorods and Ultrathin Nanosheets on Carbon Nanofibers for High-performance Supercapacitors. Sci. Rep., 2013, 3, 1470-1475. (8) Lu, X.; Wang, G.; Zhai, T.; Yu, M.; Gan, J.; Tong, Y.; Li, Y. Hydrogenated TiO2 Nanotube Arrays for Supercapacitors. Nano Lett., 2012, 12, 1690-1696. (9) Greiner, M. T.; Chai, L.; Helander, M. G.; Tang, W.; Lu, Z. Transition Metal Oxide Work Functions: The Influence of Cation Oxidation State and Oxygen Vacancies.

Adv. Funct. Mater. 2012, 22, 4557-4568. (10) Park, M.; Li, J.; Kumar, A.; Li, G.; Yang, Y. Doping of the Metal Oxide Nanostructure and its Influence in Organic Electronics. Adv. Funct. Mater. 2009, 19, 1241-1246. (11) Meyer, J.; Kidambi, P. R.; Bayer, B. C.; Weijtens, C.; Kuhn, A.; Centeno, A.; Pesquera, A.; Zurutuza, A.; Robertson, J.; Hofmann, S. Metal Oxide Induced Charge Transfer Doping and Band Alignment of Graphene Electrodes for Efficient Organic Light Emitting Diodes. Sci. Rep., 2014, 4, 5380-5386. (12) Zhao, D. D.; Zhou,W. J.; Li, H. L. Effects of Deposition Potential and Anneal Temperature on the Hexagonal Nanoporous Nickel Hydroxide Films. Chem. Mater., 2007, 19, 3882-3891. (13) Yang, G. W.; Xu,C. L.; Li, H. L. Electrodeposited Nickel Hydroxide on Nickel Foam with Ultrahigh Capacitance. Chem. Commun., 2008, 48, 6537-6539. (14) Huang, L.; Chen, D. C.; Ding, Y.; Feng, S.; Wang, Z. L.; Liu, M. Nickel–Cobalt Hydroxide Nanosheets Coated on NiCo2O4 Nanowires Grown on Carbon Fiber Paper for High-Performance Pseudocapacitors. Nano Lett., 2013, 13, 3135-3139. (15) Zhang, G.; Lou, X. W. General Solution Growth of Mesoporous NiCo2O4 Nanosheets on

Various

Conductive

Substrates

as

High-Performance

Electrodes

for

Supercapacitors. Adv. Mater., 2013, 25, 976-979. (16) Wei, T.; Chen, C.; Chien, H.; Lu, S.; Hu, C. A Cost-Effective Supercapacitor Material of Ultrahigh Specific Capacitances: Spinel Nickel Cobaltite Aerogels from an Epoxide-Driven Sol–Gel Process. Adv. Mater., 2010, 22, 347-351. (17) Chen, H.; Hu, L.; Chen, M.; Yan, Y.; Wu, L. Nickel–Cobalt Layered Double Hydroxide Nanosheets for High-performance Supercapacitor Electrode Materials.

Adv. Funct. Mater. 2014, 24, 934-942.


Page 17 of 20

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


(18) Liu, J.; Jiang, J.; Cheng, C.; Li, H.; Zhang, J.; Gong, H.; Fan, H. J. Co3O4 Nanowire@MnO2 Ultrathin Nanosheet Core/Shell Arrays: A New Class of High-Performance Pseudocapacitive Materials. Adv. Mater., 2011, 23, 2076-2081. (19) Lu, Q.; Lattanzi, M. W.; Chen, Y.; Kou, X.; Li, W.; Fan, X.; Unruh, K. M.; Chen, J. G.; Xiao, J. Q. Supercapacitor Electrodes with High-Energy and Power Densities Prepared from Monolithic NiO/Ni Nanocomposites. Angew. Chem. Int. Ed., 2011, 50, 6847-6850. (20) Chen, H.; Zhou, S.; Wu, L. Porous Nickel Hydroxide–Manganese Dioxide-Reduced Graphene Oxide Ternary Hybrid Spheres as Excellent Supercapacitor Electrode Materials. ACS Appl. Mater. Interfaces, 2014, 6, 8621-8630. (21) Yu, L.; Zhang, G.; Yuan,C.; Lou, X. W. Hierarchical NiCo2O4@MnO2 Core–Shell Heterostructured Nanowire Arrays on Ni Foam as High-Performance Supercapacitor Electrodes. Chem. Commun., 2013, 49, 137-139. (22) Ma, Z.; Shao, G.; Fan, Y.; Wang, G.; Song, J.; Shen, D. Construction of Hierarchical α-MnO2 Nanowires@Ultrathin δ-MnO2 Nanosheets Core–Shell Nanostructure with Excellent Cycling Stability for High-Power Asymmetric Supercapacitor Electrodes.

ACS Appl. Mater. Interfaces, 2016, 8, 9050–9058 (23) Zhou, X.; Chen, Q.; Wang, A.; Xu, J.; Wu, S.; Shen, J. Bamboo-like Composites of V2O5/Polyindole and Activated Carbon Cloth as Electrodes for All-Solid-State Flexible Asymmetric Supercapacitors, ACS Appl. Mater. Interfaces, 2016, 8, 3776– 3783. (24) Wang, D. W.; Fang, H. T.; Li, F.; Chen, Z. G.; Zhong, Q. S.; Lu, G. Q.; Cheng, H. M. Aligned Titania Nanotubes as an Intercalation Anode Material for Hybrid Electrochemical Energy Storage. Adv. Funct. Mater. 2008, 18, 3787-3793. (25) Grote, F.; Kuhnel, R. S.; Balducci, A.; Lei, Y. Template Assisted Fabrication of FreeStanding MnO2 Nanotube and Nanowire Arrays and Their Application in Supercapacitors. Appl. Phys. Lett., 2014, 104, 053904-053907. (26) Kang, J.; Hirata, A.; Kang, L.; Zhang, X.; Hou, Y.; Chen, L.; Li, C.; Fujita, T.; Akagi, K.; Chen, M. Enhanced Supercapacitor Performance of MnO2 by Atomic Doping.

Angew. Chem. Int. Ed., 2013, 52, 1664-1667. (27) Xia, H.; Zhu, D.; Luo, Z.; Yu, Y.; Shi, X.; Yuan, G.; Xie, J. Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors. Sci.

Rep., 2013, 3, 2978-2985.



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

Page 18 of 20

(28) Yan, N.; Hu, L.; Li, Y.; Wang, Y.; Zhong, H.; Hu, X.; Kong,X.; Chen, Q. Co3O4 Nanocages for High-Performance Anode Material in Lithium-Ion Batteries. J.

Phys. Chem. C, 2012, 116, 7227-7235. (29) Reddy, A. L. M.; Shaijumon, M. M.; Gowda, S. R.; Ajayan, P. M. Coaxial MnO2/Carbon Nanotube Array Electrodes for High-Performance Lithium Batteries.

Nano Lett., 2009, 9, 1002-1006. (30) Tan, G.; Wu, F.; Lu, J.; Chen, R.; Li, L.; Amine, K. Controllable Crystalline Preferred Orientation in Li–Co–Ni–Mn Oxide Cathode Thin Films for All-solid-state Lithium Batteries. Nanoscale, 2014, 6, 10611-10622. (31) Rakhi, R. B.; Chen, W.; Cha, D.; Alshareef, H. N. Substrate Dependent SelfOrganization

of

Mesoporous

Cobalt

Oxide

Nanowires

with

Remarkable

Pseudocapacitance. Nano Lett., 2012, 12, 2559-2567. (32) Toupin, M.; Brousse, T.; Belanger, D. Charge Storage Mechanism of MnO2 Electrode Used in Aqueous Electrochemical Capacitor. Chem. Mater., 2004, 16, 3184-3190. (33) Sathiya, M.; Prakash, A. S.; Ramesha, K.; Tarascon, J. M.; Shukla, A. K. V2O5Anchored Carbon Nanotubes for Enhanced Electrochemical Energy Storage. J. Am.

Chem. Soc., 2011, 133, 16291-16299. (34) Lindstrolm, H.; Soldergren, S.; Solbrand, A.; Rensmo, H.; Hjelm, J.; Hagfeldt, A.; Lindquist, S. E. Li+ Ion Insertion in TiO2 (Anatase). 2. Voltammetry on Nanoporous Films. J. Phys. Chem. B, 1997, 101, 7717-7722. (35) Wang, J.; Polleux, J.; Lim,J.; Dunn, B. Pseudocapacitive Contributions to Electrochemical Energy Storage in TiO2 (Anatase) Nanoparticles. J. Phys. Chem. C, 2007, 111, 14925-14931. (36) Ardizzone, S.; Fregonara, G.; Trasatti, S. “Inner” and “Outer” Active Surface of RuO2 Electrodes, Electrochim. Acta, 1990, 35, 263-267. (37) Yuan, C.; Li, J.; Hou, L.; Zhang, X.; Shen, L.; Lou, X. W. Ultrathin Mesoporous NiCo2O4 Nanosheets Supported on Ni Foam as Advanced Electrodes for Supercapacitors, Adv. Funct. Mater. 2012, 22, 4592-4597. (38) Du, J.; Zhou, G.; Zhang, H.; Cheng, C.; Ma, J.; Wei, W.; Chen, L.; Wang, T. Ultrathin Porous NiCo2O4 Nanosheet Arrays on Flexible Carbon Fabric for High-Performance Supercapacitors, ACS Appl. Mater. Interfaces, 2013, 5, 7405-7409. (39) Yang, F.; Yao, J.; Liu, F.; He, H.; Zhou, M.; Xiao, P.; Zhang, Y. Ni–Co Oxides Nanowire Arrays Grown on Ordered TiO2 Nanotubes with High Performance in Supercapacitors. J. Mater. Chem. A, 2013, 1, 594-601. 18 ACS Paragon Plus Environment

Page 19 of 20

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


(40) Singh, A. K.; Sarkar, D.; Khan, G. G.; Mandal, K. Designing One Dimensional CoNi/Co3O4-NiO Core/shell Nano-heterostructure Electrodes for High-performance Pseudocapacitor, Appl. Phys. Lett., 2014, 104, 133904-133907. (41) Yang, L.; Cheng, S.; Ding, Y.; Zhu, X.; Wang, Z. L.; Liu, M. Hierarchical Network Architectures of Carbon Fiber Paper Supported Cobalt Oxide Nanonet for HighCapacity Pseudocapacitors, Nano Lett., 2012, 12, 321-325. (42) Zhang, G. Q. Wu, H. B.; Hoster, H. E.; Chan-Park, M. B.; Lou, X. W. SingleCrystalline NiCo2O4 Nanoneedle Arrays Grown on Conductive Substrates as BinderFree Electrodes for High-Performance Supercapacitors. Energy Environ. Sci., 2012, 5, 9453-9456. (43) Jiang, H.; Mab, J.; Li, C. Hierarchical Porous NiCo2O4 Nanowires for High-rate Supercapacitors, Chem. Commun., 2012, 48, 4465-4467. (44) Wang, H. L.; Gao, Q. M.; Jiang, L. Facile Approach to Prepare Nickel Cobaltite Nanowire Materials for Supercapacitors, Small, 2011, 7, 2454-2459. (45) Singh, A. K.; Sarkar, D.; Khan, G. G.; Mandal, K. Unique hydrogenated Ni/NiO Core/shell 1D Nano-heterostructures with Superior Electrochemical Performance as Supercapacitors, J. Mater. Chem. A, 2013, 1, 12759-12767. (46) Wang, H. L.; Casalongue, H. S.; Liang, Y. Y.; Dai, H. J. Ni(OH)2 Nanoplates Grown on Graphene as Advanced Electrochemical Pseudocapacitor Materials. J. Am. Chem.

Soc., 2010, 132, 7472-7477. (47) Xia, X. H.; Tu, J. P.; Mai, Y. J.; Wang, X. L.; Gu, C. D.; Zhao, X. B. Self-supported Hydrothermal Synthesized Hollow Co3O4 Nanowire Arrays with High Supercapacitor Capacitance. J. Mater.Chem., 2011, 21, 9319-9325. (48) Jiang, J.; Liu, J.; Ding, R.; Zhu, J.; Li, Y.; Hu, A.; Li, X.; Huang, X. Large-Scale Uniform α-Co(OH)2 Long Nanowire Arrays Grown on Graphite as Pseudocapacitor Electrodes. ACS Appl. Mater. Interfaces, 2011, 3, 99-103.



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