S1

Supplementary Information

Asymmetric Supercapacitors Using 3D Nanoporous

Carbon and Cobalt Oxide Electrodes Synthesized

from a Single Metal-Organic Framework

Rahul R. Salunkhe,1 Jing Tang,

1,2 Yuichiro Kamachi,

1,3 Teruyuki Nakato,

3

Jung Ho Kim*,4

and Yusuke Yamauchi*,2

[1] World Premier International (WPI) Research Center for Materials

Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS),

1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.

[2] Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku,

Tokyo 169-8555, Japan.

[3] Department of Applied Chemistry, Graduate School of Engineering, Kyushu

Institute of Technology, 1-1 Sensui-Cho, Tobata, Kitakyushu, Fukuoka 804-

8550, Japan.

[4] Institute for Superconducting and Electronic Materials, University of

Wollongong, North Wollongong, New South Wales 2500, Australia.

Keywords: nanoporous materials; coordination polymers; metal-organic frameworks;

cobalt oxide; carbon; supercapacitors

*Corresponding authors:

jhk@uow.edu.au (J.H. Kim); Yamauchi.yusuke@nims.go.jp (Y. Yamauchi)

S2

Table S1 Comparison of surface area of our Co3O4 polyhedra with previously reported

Co3O4 nanostructures produced by different synthetic routes.

Method Morphology Surface area (m2∙g-

1) Ref.

Hydrothermal method Ultralayered Co3O4 97 S1

Chemical precipitation Co3O4 Nanosheets 127 S2

Hydrothermal method Co3O4 nanorod/Ni

foam 14.74 S3

Controlled precipitation Co3O4 nanosheets 75.9 S4

MOF templated method Co3O4 microsheets 0.21 S5

Solution method Co3O4 nanosheets 25.12 S6

Topotactic transfer approach Co3O4 nanotubes 7.6 S7

Hydrothermal method

Co3O4 Nanosheet 17.8

S8 Co3O4 Nanobelt 20.1

Co3O4 Nanocubes 22.6

MOF templated method Co3O4 porous agglomerates

47.12 S9

MOF templated method Co3O4 polyhedrons 148 Our work

S3

Table S2 Comparison of electrochemical performance of our Co3O4 sample with

previous reports using standard three-electrode system.

Method Electrolyte Morphology Capacitance

(F∙g-1)

Scan rate

(mV∙s-1)

Current density (A∙g-1)

Ref.

Hydrothermal method

KOH (6M) Nanorod 456 - 1 S10

Hydrothermal method

KOH (1M) Ultra layer 548 8 S1

Controlled precipitation

method KOH (2M) Layered 202 1 S4

Hydrothermal method

NaOH (1M) Net-like 1090 10 - S11

Hydrothermal method

KOH (2M) Nanowire 754 - 2 S12

Hydrothermal method

KOH (6M) Flakes 263 - 1 S13

MOF templated

method KOH (6M) Sheets 208 - 1 S5

MOF templated

KOH (6M) Porous

polyhedron 504 5 -

Our work

S4

Table S3 Various performance parameters for our ASC supercapacitor.

Current density

(A∙g-1)

Discharge

time

(s)

Specific capacitance

(F∙g-1)

Specific energy

(W∙h∙kg-1)

Specific power

(W∙kg-1)

2 81 101.2 36 1600

3 40 75 27 2430

4 25 63 23 3312

5 19 60 22 4042

7 10.2 44.62 16.9 5964

10 7 44 15.4 7920

method

S5

Table S4 Comparison of our ASC performance of different metal oxides/hydroxides.

Materials Counter Electrolyte Operating voltage

(V)

Energy density

(W∙h∙kg-1)

Power density (W∙kg-1)

Ref.

Ni(OH)2@Ni foam

a-MEGO KOH (6M) 1.8 13.4 85000 S14

Co (OH)2 nanorods

GO KOH (1M) 1.2 11.94 2540 S15

MoO3 AC LiSO4 1.8 45 450 S16

MnO2 AC K2SO4 (0.5 M)

1.8 28.4 150 S17

MnO2 AC Na2SO4 (0.5 M)

1.8 10.4 14700 S18

Ni(OH)2 AC KOH (1 M) 1.3 35.7 490 S19

Co3O4 Nanoporous carbon

KOH (6 M) 1.6 36 1600 Our work

GO: graphene oxide

a-MEGO: activated microwave exfoliated graphite oxide

AC: activated carbon

(Note: The comparison has been made with bare metal oxides/hydroxides that used as positive electrode only and

ASC calculation based on weight of active electrode materials.)

6

Figure S1

Figure S1. Wide angle XRD pattern of ZIF-67 crystals.

Note for Figure S1: The topological information of the prepared crystals is revealed by the powder X-ray

diffraction (XRD) patterns. As shown in the Figure S1, the diffraction peaks of the prepared crystals are

identical to simulated crystal structure of the ZIF-67 crystals,S20

indicating the successful formation of ZIF-67

crystals.

7

Figure S2

Figure S2. EDS elemental mapping images of nanoporous carbon (top) and nanoporous Co3O4 (bottom). Both

samples contain carbon, cobalt, oxygen, and nitrogen as the main elements. (All scale bars shown are 1 μm in

length.)

8

Figure S3

Figure S3. (a, c) Nitrogen adsorption-desorption isotherms for (a) nanoporous carbon and (c) nanoporous

Co3O4. (b, d) Pore size distributions of (b) nanoporous carbon and (d) nanoporous Co3O4. Inset of b shows

magnified view of mesopores distribution.

9

Figure S4

Figure S4 (a) CV curves of Co3O4//carbon ASC. The device was cycled by varying the upper cell voltage from

1 V to 1.6 V. (b) Stability study of ASC up to 2000 repeated charge-discharge cycles. Inset of (b) shows the 10

charge-discharge cycles.

10

Figure S5

Figure S5 SSC tests based on nanoporous carbon electrodes. (a) CV curves of carbon//carbon SSC, with the

device cycled by varying the upper cell voltage from 1 V to 1.6 V; (b) galvanostatic discharge curves of the

carbon//carbon SSC cell at various current densities from 1-5 A∙g-1

; and (c) dependence of the specific

capacitance on the applied current density.

11

Figure S6

Figure S6 SSC tests based on nanoporous cobalt oxide electrodes. (a) CV curves of Co3O4//Co3O4 SSC, with

the device cycled by varying the upper cell voltage from 0.5 V to 0.9 V; (b) galvanostatic discharge curves of

Co3O4//Co3O4 SSC cell at various current densities from 1-5 A∙g-1

; and (c) dependence of the specific

capacitance on the applied current density.

12

Note for Figure S5 and Figure S6: Symmetric supercapacitor (SSC) studies were carried out for the

nanoporous carbon and the Co3O4. Each type of electrode, with size of 1 × 1 cm2, was used as both the positive

and negative working electrodes. In case of the SSCs, the total mass of both electrodes was adjusted to 2

mg∙cm-2

. Figure S5a shows the CV curves of the carbon//carbon SSC at various potential windows ranging

from 1.0 V to 1.6 V. It exhibits a rectangular shape, however, and after 1.6 V, a steep peak is observed, which

might be due to some irreversible chemical reactions, so the maximum working potential of this material is up

to 1.6 V. The capacitance of the SSC was evaluated by galvanostatic charge-discharge measurements (Figure

S5b). For this purpose, the applied current density was varied from 1 to 5 A∙g-1

. The absence of any initial

voltage loss (i.e. IR drop) indicates a fast current response with low internal resistance. The variation of specific

capacitance with applied current density is shown in Figure S5c. The maximum capacitance value obtained for

the symmetric carbon//carbon supercapacitor was 20 F∙g-1

at a current density of 1 A∙g-1

. Similar to the tests for

the carbon-based SSC, Co3O4 SSC tests were carried out (Figure S6a-c). The CV studies show that the

maximum working potential for the Co3O4-based supercapacitor is 0.9 V. The SSC cell shows a very

rectangular shape. The maximum capacitance value of the SSC was found to be 66 F∙g-1

at a current density of 1

A∙g-1

.

13

Figure S7

Figure S7 Heating of Co3O4 samples without preliminary nitrogen heat treatment at (a) 400 ºC and (b) 350 ºC,

respectively.

14

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