Supporting Information Copyright Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, 2014
Synthesis of Highly Active and Stable Spinel-Type Oxygen Evolution Electrocatalysts by a Rapid Inorganic Self-Templating Method Tian Yi Ma,[a] Sheng Dai,[a] Mietek Jaroniec,[b] and Shi Zhang Qiao*[a]
chem_201403946_sm_miscellaneous_information.pdf
Supplementary table and figures:
Table S1. Elemental analysis of P-MnxCo3-xO4-δ and B-MnCo2O4. Sample
P-MnxCo3-xO4-δ
B-MnCo2O4
Mn Co O (wt.%) (wt.%) (wt.%)
Composition
Surface area (m2 g-1)
Current densities at 1.60 V (mA cm-2)
x = 0.8
18.8
55.5
25.7
Mn0.8Co2.2O3.76
254
15.8
x = 1.0
23.6
50.6
25.8
MnCo2O3.75
263
16.6
x = 1.2
28.3
45.6
26.1
Mn1.2Co1.8O3.79
250
14.4
x = 1.4
33.1
40.6
26.3
Mn1.4Co1.6O3.81
246
13.2
x = 1.0
23.2
49.8
26.9
MnCo2O3.98
35
0.9
Figure S1. EDS elemental mapping of P-MnCo2O4-δ+KCl before water washing, showing homogenous dispersion of K, Cl, Mn, Co and O elements.
1
100 nm
20 nm
Figure S2. SEM and TEM images of P-MnCo2O4-δ.
100 nm
200 nm
Figure S3. TEM images of B-MnCo2O4 synthesized by the conventional sol-gel method, showing the bulk morphology with large crystal sizes.
2
(311)
Intensity (a.u.)
B-MnCo2O4
(220) (511) (440)
(400) (222)
(422)
MnCo2O4 20
30
40
50
60
70
2 Theta (Degree)
Figure S4. XRD pattern of B-MnCo2O4, showing high-intensity diffraction peaks.
2
-1
Surface area (m g )
200 150
Milled P-MnCo2O4- 2
-1
2
-1
SBET = 56 m g
3
250
120
-1
P-MnCo2O4-
Volume adsorbed (cm g STP)
300
80
B-MnCo2O4 SBET = 35 m g
40
0 0.0
0.2
0.4
0.6
0.8
1.0
Relative pressure (P/P0)
100
Milled P-MnCo2O4- P-MnCo2O4-+KCl
50
B-MnCo2O4
0
Figure S5. A comparison of surface areas of different samples, with inset displaying N2 adsorption isotherms of the milled P-MnCo2O4-δ and B-MnCo2O4.
3
(a)
Co 2p
(b)
2p3/2
Mn 2p 2p3/2 2p1/2
2p1/2 3+
2+ (sat) 2+ 3+ (sat)
810
Intensity (a.u.)
Intensity (a.u.)
3+
2+ 3+ (sat) 2+ (sat)
3+ 3+
660
800 790 780 Binding Energy (eV)
(c)
655
650
3+
655
650
645
640
540
635
536 532 528 Binding Energy (eV)
Binding Energy (eV)
(f)
(e) O
524
O 1s
Oads
Co Co
O Intensity (a.u.)
Intensity (a.u.)
Co
635
Oads
Intensity (a.u.)
Intensity (a.u.)
2+
3+
660
640
(d) O 1s
2p1/2
2+
645
Binding Energy (eV)
Mn 2p
2p3/2
2+
2+
Co Mn C CoCo
1000
800
600
400
200
0
540
Binding Energy (eV)
536
532
528
Binding Energy (eV)
Figure S6. High resolution XPS spectra of (a) Co 2p, (c) Mn 2p and (d) O 1s core levels in BMnCo2O4. High resolution XPS spectrum of (b) Mn 2p core level in P-MnCo2O4-δ. (e) XPS survey spectrum of B-MnCo2O4. (f) High resolution XPS spectrum of O 1s core level in the milled P-MnCo2O4-δ. 4
80
-2
J (mA cm ) (GSA)
1500 rpm 60
O2-saturated 0.1 M KOH
40
20
0 1.0
1.2
1.4
1.6
1.8
E vs. RHE (V)
Figure S7. The LSV plot of neat carbon powder (Vulcan XC-72), showing negligible OER activity.
Overpotential vs. RHE (V)
0.5
-1
IrO2 92 mV decade 0.4
0.3
0.0
0.5 1.0 -2 Log[J (mA cm )]
1.5
Figure S8. The Tafel plot of IrO2.
5
(b)
(a)
0
0.40 V
Pt
Iring (A)
-10
Pt
GC
-20
N2-saturated
N2-saturated
1500 rpm Idisk = 0
1500 rpm Idisk = 200 A
-30
Catalyst
-40
ORR
OER
OH-
O2
-50 0
OH-
10
20
30
40
0
10
20
30
Time (s)
Figure S9. Evidence of O2 generation from P-MnCo2O4-δ using a RRDE.
-2
J (mA cm ) (GSA)
2.0
P-MnCo2O4-
1.5
1.0
0.5
0.0 0
2
4
6
8
10
Time (h)
Figure S10. Chronoamperometric response of P-MnCo2O4-δ at 1.53 V vs. RHE.
6
40
50
(a)
80
(b)
1.52
1 M KOH
70
P-MnCo2O4- in 0.1 M KOH
50 40
1.50
-2
-2
J (mA cm ) (GSA)
60
E at 2.0 mA cm vs. RHE (V)
P-MnCo2O4- in 1 M KOH
30 20 10
1.48
IrO2
1.46
P-MnCo2O4-
0 1.0
1.2
1.4
1.6
0
1.8
200
400
600
800
1000
Time (s)
E vs. RHE (V)
Figure S11. (a) LSVs of P-MnCo2O4-δ in 0.1 M and 1 M KOH solutions. (b) Chronopotentiometric response of P-MnCo2O4-δ in 1 M KOH solution as compared to that obtained for IrO2 at a constant current density of 2.0 mA cm-2.
x = 0.8 x = 1.0 x = 1.2 x = 1.4
16.6
0.4
0.6
0.8
14.4
10 100 5
0
1.0
200 13.2
-1
50
0.2
15.8
-2
100
0 0.0
15
300
2
J at 1.60 V (mA cm )
3
-1
150
(b) 20
P-MnxCo3-xO4-
Surface area (m g )
Volume adsorbed (cm g STP)
(a) 200
0.8
1.0
1.2
1.4
0
X
Relative pressure (P/P0)
Figure S12. (a) N2 adsorption isotherms of P-MnxCo3-xO4-δ with different x values. (b) Comparison of current densities at 1.60 V and surface areas of P-MnxCo3-xO4-δ with different x values.
7
-Z'' ()
400
Milled P-MnCo2O4- 200
P-MnCo2O4-
0 0
200
400
Z' ()
Figure S13. (a) Electrochemical impedance spectra (EIS) of P-MnCo2O4-δ before and after ball-milling supported on carbon powder, with inset showing the corresponding equivalent circuit diagram, including an electrolyte resistance (Rs), a charge-transfer resistance (Rt), and a constant-phase element (CPE). The diameter of the semicircle for P-MnCo2O4-δ is much smaller than that of the milled P-MnCo2O4-δ in the high-medium frequency region of the EIS, which indicates a lower contact and charge transfer impedance of P-MnCo2O4-δ than that of the milled P-MnCo2O4-δ.
8
(a)
(b)
5 nm
5 nm
(d)
(c)
5 nm
5 nm
Figure S14. HRTEM images of (a, b) P-MnCo2O4-δ and (c, d) B-MnCo2O4. Point defects often cause a local lattice distortion and the real defect areas are much larger than a single atom. For example, an interstitial atom may push the surrounding atoms away from their ideal positions. In this case, HRTEM images may show high enough contrast (see J. C. RuizMorales, et al., Nature, 2006, 439, 568). The randomly distributed local defects are visible as dark spots in the HRTEM images of P-MnCo2O4-δ (Figures S14a, b). The edges of the PMnCo2O4-δ nanocrystals are very rough, with some distortion of lattice fringes including bending and dislocation (circled in the figures), due to the peeling of neighboring KCl selftemplate during the synthesis process, which reveals the presence of numerous defect sites in P-MnCo2O4-δ. On the contrary, large crystals with perfect lattice fringes are observed in the HRTEM images of B-MnCo2O4 (Figures S14c, d).
9
Synthesis of Highly Active and Stable Spinel-Type Oxygen Evolution Electrocatalysts by a Rapid Inorganic Self-Templating Method Tian Yi Ma,[a] Sheng Dai,[a] Mietek Jaroniec,[b] and Shi Zhang Qiao*[a]
chem_201403946_sm_miscellaneous_information.pdf
Supplementary table and figures:
Table S1. Elemental analysis of P-MnxCo3-xO4-δ and B-MnCo2O4. Sample
P-MnxCo3-xO4-δ
B-MnCo2O4
Mn Co O (wt.%) (wt.%) (wt.%)
Composition
Surface area (m2 g-1)
Current densities at 1.60 V (mA cm-2)
x = 0.8
18.8
55.5
25.7
Mn0.8Co2.2O3.76
254
15.8
x = 1.0
23.6
50.6
25.8
MnCo2O3.75
263
16.6
x = 1.2
28.3
45.6
26.1
Mn1.2Co1.8O3.79
250
14.4
x = 1.4
33.1
40.6
26.3
Mn1.4Co1.6O3.81
246
13.2
x = 1.0
23.2
49.8
26.9
MnCo2O3.98
35
0.9
Figure S1. EDS elemental mapping of P-MnCo2O4-δ+KCl before water washing, showing homogenous dispersion of K, Cl, Mn, Co and O elements.
1
100 nm
20 nm
Figure S2. SEM and TEM images of P-MnCo2O4-δ.
100 nm
200 nm
Figure S3. TEM images of B-MnCo2O4 synthesized by the conventional sol-gel method, showing the bulk morphology with large crystal sizes.
2
(311)
Intensity (a.u.)
B-MnCo2O4
(220) (511) (440)
(400) (222)
(422)
MnCo2O4 20
30
40
50
60
70
2 Theta (Degree)
Figure S4. XRD pattern of B-MnCo2O4, showing high-intensity diffraction peaks.
2
-1
Surface area (m g )
200 150
Milled P-MnCo2O4- 2
-1
2
-1
SBET = 56 m g
3
250
120
-1
P-MnCo2O4-
Volume adsorbed (cm g STP)
300
80
B-MnCo2O4 SBET = 35 m g
40
0 0.0
0.2
0.4
0.6
0.8
1.0
Relative pressure (P/P0)
100
Milled P-MnCo2O4- P-MnCo2O4-+KCl
50
B-MnCo2O4
0
Figure S5. A comparison of surface areas of different samples, with inset displaying N2 adsorption isotherms of the milled P-MnCo2O4-δ and B-MnCo2O4.
3
(a)
Co 2p
(b)
2p3/2
Mn 2p 2p3/2 2p1/2
2p1/2 3+
2+ (sat) 2+ 3+ (sat)
810
Intensity (a.u.)
Intensity (a.u.)
3+
2+ 3+ (sat) 2+ (sat)
3+ 3+
660
800 790 780 Binding Energy (eV)
(c)
655
650
3+
655
650
645
640
540
635
536 532 528 Binding Energy (eV)
Binding Energy (eV)
(f)
(e) O
524
O 1s
Oads
Co Co
O Intensity (a.u.)
Intensity (a.u.)
Co
635
Oads
Intensity (a.u.)
Intensity (a.u.)
2+
3+
660
640
(d) O 1s
2p1/2
2+
645
Binding Energy (eV)
Mn 2p
2p3/2
2+
2+
Co Mn C CoCo
1000
800
600
400
200
0
540
Binding Energy (eV)
536
532
528
Binding Energy (eV)
Figure S6. High resolution XPS spectra of (a) Co 2p, (c) Mn 2p and (d) O 1s core levels in BMnCo2O4. High resolution XPS spectrum of (b) Mn 2p core level in P-MnCo2O4-δ. (e) XPS survey spectrum of B-MnCo2O4. (f) High resolution XPS spectrum of O 1s core level in the milled P-MnCo2O4-δ. 4
80
-2
J (mA cm ) (GSA)
1500 rpm 60
O2-saturated 0.1 M KOH
40
20
0 1.0
1.2
1.4
1.6
1.8
E vs. RHE (V)
Figure S7. The LSV plot of neat carbon powder (Vulcan XC-72), showing negligible OER activity.
Overpotential vs. RHE (V)
0.5
-1
IrO2 92 mV decade 0.4
0.3
0.0
0.5 1.0 -2 Log[J (mA cm )]
1.5
Figure S8. The Tafel plot of IrO2.
5
(b)
(a)
0
0.40 V
Pt
Iring (A)
-10
Pt
GC
-20
N2-saturated
N2-saturated
1500 rpm Idisk = 0
1500 rpm Idisk = 200 A
-30
Catalyst
-40
ORR
OER
OH-
O2
-50 0
OH-
10
20
30
40
0
10
20
30
Time (s)
Figure S9. Evidence of O2 generation from P-MnCo2O4-δ using a RRDE.
-2
J (mA cm ) (GSA)
2.0
P-MnCo2O4-
1.5
1.0
0.5
0.0 0
2
4
6
8
10
Time (h)
Figure S10. Chronoamperometric response of P-MnCo2O4-δ at 1.53 V vs. RHE.
6
40
50
(a)
80
(b)
1.52
1 M KOH
70
P-MnCo2O4- in 0.1 M KOH
50 40
1.50
-2
-2
J (mA cm ) (GSA)
60
E at 2.0 mA cm vs. RHE (V)
P-MnCo2O4- in 1 M KOH
30 20 10
1.48
IrO2
1.46
P-MnCo2O4-
0 1.0
1.2
1.4
1.6
0
1.8
200
400
600
800
1000
Time (s)
E vs. RHE (V)
Figure S11. (a) LSVs of P-MnCo2O4-δ in 0.1 M and 1 M KOH solutions. (b) Chronopotentiometric response of P-MnCo2O4-δ in 1 M KOH solution as compared to that obtained for IrO2 at a constant current density of 2.0 mA cm-2.
x = 0.8 x = 1.0 x = 1.2 x = 1.4
16.6
0.4
0.6
0.8
14.4
10 100 5
0
1.0
200 13.2
-1
50
0.2
15.8
-2
100
0 0.0
15
300
2
J at 1.60 V (mA cm )
3
-1
150
(b) 20
P-MnxCo3-xO4-
Surface area (m g )
Volume adsorbed (cm g STP)
(a) 200
0.8
1.0
1.2
1.4
0
X
Relative pressure (P/P0)
Figure S12. (a) N2 adsorption isotherms of P-MnxCo3-xO4-δ with different x values. (b) Comparison of current densities at 1.60 V and surface areas of P-MnxCo3-xO4-δ with different x values.
7
-Z'' ()
400
Milled P-MnCo2O4- 200
P-MnCo2O4-
0 0
200
400
Z' ()
Figure S13. (a) Electrochemical impedance spectra (EIS) of P-MnCo2O4-δ before and after ball-milling supported on carbon powder, with inset showing the corresponding equivalent circuit diagram, including an electrolyte resistance (Rs), a charge-transfer resistance (Rt), and a constant-phase element (CPE). The diameter of the semicircle for P-MnCo2O4-δ is much smaller than that of the milled P-MnCo2O4-δ in the high-medium frequency region of the EIS, which indicates a lower contact and charge transfer impedance of P-MnCo2O4-δ than that of the milled P-MnCo2O4-δ.
8
(a)
(b)
5 nm
5 nm
(d)
(c)
5 nm
5 nm
Figure S14. HRTEM images of (a, b) P-MnCo2O4-δ and (c, d) B-MnCo2O4. Point defects often cause a local lattice distortion and the real defect areas are much larger than a single atom. For example, an interstitial atom may push the surrounding atoms away from their ideal positions. In this case, HRTEM images may show high enough contrast (see J. C. RuizMorales, et al., Nature, 2006, 439, 568). The randomly distributed local defects are visible as dark spots in the HRTEM images of P-MnCo2O4-δ (Figures S14a, b). The edges of the PMnCo2O4-δ nanocrystals are very rough, with some distortion of lattice fringes including bending and dislocation (circled in the figures), due to the peeling of neighboring KCl selftemplate during the synthesis process, which reveals the presence of numerous defect sites in P-MnCo2O4-δ. On the contrary, large crystals with perfect lattice fringes are observed in the HRTEM images of B-MnCo2O4 (Figures S14c, d).
9
