large-scale quantification of cvd graphene surface coverage - royal society of chemistry ·...
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Supporting Information
Large-scale quantification of CVD graphene
surface coverage
Adriano Ambrosi,a Alessandra Bonanni,
a Zdeněk Sofer
b and Martin Pumera
a*
a
Division of Chemistry & Biological Chemistry, School of Physical and Mathematical
Sciences, Nanyang Technological University, Singapore 637371.
b Institute of Chemical Technology, Department of Inorganic Chemistry, 166 28 Prague 6,
Czech Republic.
*Correspondence to: [email protected]
Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2013
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Fig. S1. Schematic of the electrochemical cell used for the measurements. It consists of a flat bottom
part where the metal/CVD-graphene sample is placed; and an upper part having a conical hole which
functions as reservoir. A rubber o-ring (I.D. = 4.5 mm; O.D. = 8.1 mm) and four screws ensure a
secure and sealed chamber to be filled with the measurement solution for a total surface of 17 mm2 for
the CVD-Graphene sample to be examined. The metal/CVD-graphene acts as the working electrode
while a Pt and Ag/AgCl wire immersed in the solution act as the auxiliary and the reference electrode,
respectively. The size of the o-ring defines the portion of the CVD-graphene surface investigated. A
Cu tape was used to ensure the electrical connection between the metal/CVD-graphene and the
voltammetric instrument. Electrochemical treatment and measurements were performed using NaOH
0.1 M as background electrolyte. All electrochemical potentials in this paper are stated versus
Ag/AgCl reference electrode.
Substrate/CVD-graphene
O-ring
Electrode
connectors
Cu-tape
connector
Ag/AgCl-wire Pt-wire
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Fig. S2. Successive cyclic voltammograms of (A) bare Si/SiO2/Ni, (B) bare Ni foil and (C) bare Cu
foil in 0.1 M NaOH. Plots of the charge (µC) vs. the number of CV scans are presented in the lower
part of the figure. The charge involved in the anodic oxidation of the Ni(OH)2 to NiOOH (Fig. S2A
and B) increases linearly with the natural logarithmic of the number of CV scans. On the contrary, the
electrochemical signal recorded for Cu foil reaches a steady contour after a few CV scans.
-200
-100
0
100
200
300
400
-0.5 -0.3 -0.1 0.1 0.3 0.5 0.7
i/ µ
A
E / V
17 mm2
0
50
100
150
200
250
1 10
Q /
µC
Log No. CV scans
Anodic peak
-200
-100
0
100
200
300
400
-0.5 -0.3 -0.1 0.1 0.3 0.5 0.7
i/ µ
A
E / V
0
50
100
150
200
1 10
Q /
µC
Log No. CV scans
Anodic peak
-300
-250
-200
-150
-100
-50
0
50
100
150
-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2
i / µ
A
E / V
0
50
100
150
200
250
300
0 10 20 30 40 50
Q /
µC
No. CV scans
peak-1
peak-2
17 mm2 17 mm2
A B C
a2
a1
c1
c2
Peak c1
Peak c2
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Fig. S3. (A) Different plots correlated to the Ni film active surface area. A linear relationship can be
obtained taking into consideration the charge involved in the anodic oxidation of Ni(OH)2 after 50 CV
scans (red square) or after 10 CV scans (blue square). Considering the CV scans from 4 to 10, a linear
regression between the charge and the Log of the number of scans (4-10) can be obtained. The slope
of such linear regression is then linearly proportional with the active Ni metal surface (green triangle).
(B) Plots correlated to the Cu active surface. A linear relationship can be obtained considering the
charge involved in the cathodic reduction process C1 (red square) or C2 (blue square). It can be seen
that in all cases a perfectly linear regression is generated, giving the opportunity to choose the most
appropriate measurement method.
0
50
100
150
200
250
0 5 10 15 20
Q /
µC
Ni-film active surface / mm2
50scans
10scans
slope4-10
0
50
100
150
200
250
300
0 5 10 15 20
Q /
µC
Cu-foil active surface / mm2
peak-1
peak-2
BA
Peak c1
Peak c2y = (16.45 0.40) xR2 = 0.998
y = (8.25 0.39) xR2 = 0.988
y = (7.95 0.29) xR2 = 0.993
y = (14.29 0.53) xR2 = 0.993
y = (2.42 0.03) xR2 = 0.999
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Fig. S4. Optical microscopy image of a region of Cu-Graphene sample (A) or Si/SiO2/Ni-Graphene
sample (D) with the corresponding Raman maps generated according to the G band (1550-1650 cm-1
)
(B and E) or the 2D band (2650-2750 cm-1
) (C and F). Laser: 514 nm, 100x objector, ~500 nm spot
size.
Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2013
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Fig. S5. Scanning electron microscopy images of Cu-Graphene sample as received (A) and after 10
cyclic voltammetric scans in NaOH (C). Si/SiO2/Ni-Graphene sample as received (B) and after 20
cyclic voltammetric scans in NaOH (D).
BA
DC
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Fig. S6. Optical microscopy images and corresponding Raman spectra of Ni-foil-ML-Graphene
samples as received (A) and after 50 cyclic voltammetric scans in NaOH (B).
0 1000 2000 30000 1000 2000 3000
Raman shift /cm-1 Raman shift /cm-1
Inte
nsi
ty /
a.u
.
Inte
nsi
ty /
a.u
.
BA
Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2013