bimetallic thin film nico-nicoo2@nc as superior bifunctionalcoox@cn 0.12 1.0 m koh 0.23 115 j. am....
TRANSCRIPT
Supportting Information for
Bimetallic Thin Film NiCo-NiCoO2@NC as Superior Bifunctional
Electro- catalyst for Overall Water Splitting in Alkaline Media
Yun Xiao,† Pengfang Zhang,† Xin Zhang,†* Xiaoping Dai,† Yangde Ma,† Yao Wang,† Yan Jiang,†
Mengzhao Liu,† Yue Wang†.
†State Key Laboratory of Heavy Oil Processing College of Chemical Engineering, China University of Petroleum Beijing
102249 (China)
‡National Institute of Metrology, Beijing 100013, China
*Corresponding author. E-mail: [email protected]
Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2017
Calculation method
The TOF value (s-1
) was calculated from equation (1):
TOF = J×A
4×F×n (1)
J is obtained at overpotential = 300 mV, normalized by geometric area of GCE (0.07065 cm2), A is the
geometric area of GCE (0.07065 cm2), F is the Faraday constant, n is the mole number of active sites on
the electrode, n(metallic Ni and Co) is the mole number of active sites for HER, n(total Ni and Co
elements) is the mole number of active sites for OER, via equation below:
n(metallic Ni and Co) =mloading×A×rmetallic NiCo/NiCo− NiCoO2@NC×NA
Mw (2)
n(total Ni and Co ) =mloading×A×rtotal NiCo/NiCo− NiCoO2@NC ×NA
Mw (3)
where mloading is the loading mass via drop-casting, A is the geometric area of GCE (0.07065 cm2),
r metallic NiCo/NiCo−NiCoO2@NC is the weight ratio of Ni-Co alloy in NiCo-NiCoO2@NC,
rtotal NiCo/NiCo−NiCoO2@NC is the weight ratio of total Ni and Co elements in NiCo-NiCoO2@NC, NA is
Avogadro's constant, Mw is the molecular weight of active sites.
Mass activity (A·g-1
) values were calculated from the electrocatalyst loading mloading(0.14 mg· cm-2
)
and the measured current densityJ (mA ·cm-2
) at η = 300 mV:
Mass activity = J
mloading (4)
Table S1. Compositions of thin film NiCo-NiCoO2@NC, NiCoO2, Ni-NiO@NC, Co-CoO@NC
determined by ICP-MS and XPS
Sample bulk content(wt%) by ICP-MS Surface content(wt%) by XPS
Co Ni Co : Ni (atom) C N O Co Ni Co : Ni (atom)
Ni-NiO@NC - 65.78 - 83.97 1.48 11.45 - 3.1 -
Co-CoO@NC 60.14 - - 82.23 1.8 13.19 2.79 - -
NiCoO2 29.22 30.52 0.95 26.84 - 46.62 14.82 11.72 1.26
NiCo-NiCoO2@NC 27.25 29.89 0.91 60.96 2.65 25.02 6.48 4.89 1.32
NiCo@NC 37.03 39.84 0.93 66.84 - 26.62 6.82 5.72 1.19
NiCoO2@NC 30.60 31.63 0.97 60.96 2.65 39.02 7.48 6.59 1.14
Table S2. The surface area and pore volume of NiCo-NiCoO2@NC, NiCoO2, Ni-NiO@NC,
Co-CoO@NC
Material Surface area Pore volume Average pore
m2·g-
1 cm
3·g
-1 diameter(nm)
NiCo-NiCoO2@NC 128.7 0.22 3.77
Ni-NiO@NC 208.9 0.21 3.68
Co-CoO@NC 108.4 0.18 3.80
NiCoO2 19.7 0.12 3.40
Table S3. The quantitative results of H2-TPR characterization
Catalyst Weight Reduction Peak area H2
consumption
Ni/Co in
Oxides
content
Metallic
Ni/Co
content
(mg) Temperature (°C) mmol (wt%) (wt%)
NiCo-NiCoO2@NC 10.00 483/526 5011.00 0.05 31 26
Ni-NiO@NC 12.55 490 6894.80 0.07 34 32
Co-CoO@NC 10.00 582 5271.00 0.06 33 27
Table S4. Comparison of the electrocatalytic activity of NiCo-NiCoO2@NC to some
representatively reported OER catalysts in basic solutions.
Material Loading Electrolyte η (V) Tafel slope Reference
mg·cm-2
10 mA·cm-2
mV/decade
NiCo-NiCoO2@NC 0.14 1.0 M KOH 0.31 76 This work
Commercial IrO2/C 0.14 1.0 M KOH 0.36 136 This work
Co3O4/N-rmGO 1 1.0 M KOH 0.31 67 Nat. Mater. 2011, 10, 7801
Co3O4/NiCo2O4 1 1 M KOH 0.34 88 J. Am. Chem. Soc. 2015, 137, 16, 55902
NixCo3-xO4 2.7 1.0 M NaOH 0.42 59 Adv. Mater. 2010, 22, 19263 .
Co-P film 2.71 1.0 M KOH 0.34 47 Angew. Chem., Int. Ed. 2015, 54, 62514
α-Ni(OH)2/GC 0.2 0.1 M KOH 0.33 42 Chem. Mater. 2014, 26, 41305
NiCo-NS 0.07 1.0 M KOH 0.33 41 Nat. Commun. 2014, 5, 44776
NiCoLDHs 0.17 1.0 M KOH 0.37 40 Nano Lett. 2015, 15, 14217
CoP/C 0.36 1.0 M KOH 0.33 53 J. Mater. Chem. A. 2016, 4, 23, 90728
PNG-NiCo2O4 - 0.1 M KOH 0.35 156 ACS Nano 2013, 7, 101909
Table S5. Comparison of the electrocatalytic activity of NiCo-NiCoO2@NC to some
representatively reported HER catalysts for basic solutions.
Material Loading Electrolyte η (mV) Tafel slope Reference
mg·cm-2
10 mA·cm-2
mV/decade
NiCo-NiCoO2@NC 0.26 1.0 M KOH 0.11 125 This work
Commercial Pt/C 0.26 1.0 M KOH 0.066 90 This work
Co@N-C 4.5 1.0 M KOH 0.21 108 J. Mater. Chem. A 2014, 2, 2006710
Co-NCNT/CC 3.4 1.0 M KOH 0.18 193 ChemSusChem 2015, 8, 185011
CoOx@CN 0.12 1.0 M KOH 0.23 115 J. Am. Chem. Soc. 2015, 137, 268812
CoSe2 nanosheet 0.142 0.1 M KOH 0.32 44 ACS Nano 2014, 4,397013
Ni0.33Co0.67S2 nanowire 0.3 1.0 M KOH 0.088 118 Adv. Mater. 2010, 22,19263
Co-NRCNTs 0.36 1.0 M KOH 0.37 - Angew. Chem., Int. Ed. 2014, 5314
NiCo2S4 4 1.0 M KOH 0.26 141 Nanoscale 2015, 7, 1512215
NiCo2O4 1 1.0 M NaOH 0.11 49.7 Angew. Chem., Int. Ed. 2016, 55, 629016
Co-P film 2.71 1.0 M KOH 0.094 42 Angew. Chem., Int. Ed. 2015, 54, 62514
Table S6. TOF for HER of NiCo-NiCoO2@NC, Ni-NiO@NC, Co-CoO@NC, NiCo@NC and Pt/C
Catalyst
Current
density
(mA•cm-2
)
Current
density
(mA•cm-2
)
TOFH(S-1
) TOFH(S-1
) Mass activity
(A·g-1
)
Mass activity
(A·g-1
)
at η=300 mV at η=500 mV at η=300
mV
at η=500
mV at η=300 mV at η=500 mV
NiCo-NiCoO2@NC -141.4 -745.4 0.63 3.32 539.7 2845.0
Ni-NiO@NC -65.5 -169.9 0.24 0.62 250.0 648.5
Co-CoO@NC -19.7 -181.0 0.08 0.77 75.2 690.8
Pt/C -86.0 -130.0 0.87 1.31 328.2 496.2
NiCo@NC -49.1 -132.3 0.14 0.37 187.4 505.0
Table S7. TOF for OER of NiCo-NiCoO2@NC, Ni-NiO@NC, Co-CoO@NC, NiCo@NC,
NiCoO2@NC and IrO2
Catalyst
Current
density
(mA•cm-2
)
Current
density
(mA•cm-2
)
TOFO(S-1
) TOFO(S-1
) Mass activity
(A·g-1
)
Mass activity
(A·g-1
)
at η=300 mV at η=500 mV at η=300 mV at η=500 mV at η=300 mV at η=500 mV
NiCo-NiCoO2@NC 6.6 181.2 0.013 0.35 47.4 1294.3
Ni-NiO@NC 6.9 129.3 0.011 0.21 49.3 923.6
Co-CoO@NC 6.2 98.2 0.011 0.18 44.3 701.4
IrO2 4.0 79.2 0.0090 0.18 28.6 565.7
NiCo@NC 4.1 138.4 0.0058 0.20 29.3 988.6
NiCoO2@NC 4.0 150.2 0.0070 0.26 28.6 1072.9
Table S8. “theoretical” TOF numbers of NiCo-NiCoO2@NC
TOF TOFcal-H(S-1
) TOFcal-O(S-1
) TOFcalM-H(S-1
) TOFcalM-O(S-1
)
η(mV) η=300 η=500 η=300 η=500 η=300 η=500 η=300 η=500
NiCo-NiCoO2@NC 0.16 0.69 0.01 0.23 0.070 0.18 0.01 0.20
Table S9. Comparison of the electrocatalytic activity of NiCo-NiCoO2@NC to some
representatively reported bifunctional electrocatalysts for overall water splitting in 1.0 M KOH
solution.
Catalyst Catalyst Substrate Overall Voltage
(V) Reference
Cathode (H2) Athode (O2) at j=10 mA·cm-2
NiCo-NiCoO2@NC NiCo-NiCoO2@NC Ni foam 1.44 This work
NiFeLDH NiFeLDH Ni foam ~1.70 Science 2014, 345, 159317
CoOx@CN CoOx@CN Ni foam 1.62 J. Am. Chem. Soc. 2015, 137, 268812
NiSe NWs NiSe NWs Ni foam 1.63 Angew. Chen. Int. Ed. 2015, 54, 935118
Ni-Fe-O Ni-Fe-O Ni foam 1.51 Nat. Commun. 2015, 6, 726119
Ni0.33Co0.67S2 NiCo2O4 Ti foam ~1.73 Adv. Energy Mater. 2015, 5, 140203120
Ni2P nanoparticle Ni2P nanoparticle Ni foam 1.63 Energy Environ. Sci. 2015, 8, 234721
Ni4P5 film Ni4P5 film Ni foam 1.7 Angew. Chem. Int. Ed. 2015, 54, 1236122
Co-P film Co-P film Ni foam 1.63 Angew. Chen. Int. Ed. 2015, 54, 62514
EG/Co0.85Se/NiFe-LDH EG/Co0.85Se/NiFe-LDH EG foam 1.67 Energy Environ. Sci. 2016, 9, 47823
CoP nanorod CoP nanorod Ni foam 1.62 Adv. Funct. Mater. 2016, 25, 733724
Figure S1. (a) SEM image and (b) TEM image of NiCo-NiCoO2@NC obtained by directly calcination
under 600 oC
1 μm 200 nm
a b
Figure S2. XRD pattern of NiCoDH precursor [Ni(OH)2 (JCPDS no. 14-0117); Co(OH)2 (JCPDS no.
30-0443)]
Figure S3. (a) XRD patterns of NiCo@NC, NiCoO2@NC and NiCo-NiCoO2@NC; (b-d) XPS patterns
of NiCo@NC and NiCoO2@NC: (b) Ni 2p; (c) Co 2p; (d) O 1s.
b
c
a
d
Figure S4. SEM images of (a) Ni-NiO@NC; (b) Co-CoO@NC and c) NiCoO2.
Figure S5. TEM images of (a) Ni-NiO@NC with the inset showing the corresponding particle-size
distribution histogram; (b) Co-CoO@NC with the inset showing the corresponding particle-size
distribution histogram; c) NiCoO2.
ba
100 nm
c
34 36 38 40 42 440
10
20
30
40
Diameter(nm)
Fre
qu
en
cy(%
)
39.1±3.6 nm
27 30 33 360
20
40
60
Diameter(nm)
Fre
qu
en
cy
(%) 32.8±3.2 nm
Figure S6. (a) XPS patterns of N 1s of NiCo-NiCoO2@NC; (b) HER linear sweep voltammetry
(LSV) curves of NiCo-NiCoO2@NC and NiCo-NiCoO2@C; (c) OER LSV curves of
NiCo-NiCoO2@NC and NiCo-NiCoO2@C.
a cb
Figure S7. (a) XPS patterns of N 1s of Ni-NiO@NC; (b-f) CV measurements in a non-faradic
current region (0.1-0.2 V vs. RHE, no iR-corrected) at scan rates of 5, 10, 25, 50 and 100 mV s-1
of b) NiCo-NiCoO2@NC, c) Ni-NiO@NC, d) Co-CoO@NC, e) NiCoO2 and f) NC in 1 M
KOH.
b c
e f
a
d
Figure S8. TEM images of (a) NiCo@NC and (b) NiCoO2@NC
a b
Figure S9. (a) Cyclic voltammetry (CV) curves of NiCo@NC recorded at a scan rate of 50 mV s-1
in
1.0 M KOH solution; (b-d) XPS spectrum of CV conditioned species: (b) Ni 2p; (c) Co 2p; (d) O 1s.
b
c
a
d
Figure S10. XPS spectrum of OER conditioned NiCo- NiCoO2@NC: (a) Ni 2p; (b) Co 2p; (c) O 1s.
a b c
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