Characterization and electrochemical properties of a nickel film/carbon paper electrode prepared by a filtered cathodic vacuum arc technique

Article abstract of DOI:10.1039/c5ra09487a

A nickel film was prepared through plasma deposition of a metal onto a carbon paper (CP) substrate with the filtered cathodic vacuum arc technique. Nickel metal plasma was generated at a current of 90 A and deposited on the CP substrate for 3 seconds, forming the nickel film modified electrode. The morphology image of the nickel film on the substrate surface was characterized by scanning electron microscopy (SEM). The existence of the nickel film was verified by energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results of the water contact angle measurement (WCA) showed that the existence of the nickel film improved the hydrophilicity of the CP. Cyclic voltammetry (CV) was carried out to investigate the electrochemical properties of the Ni/CP electrode. The nickel film provided a good electron conduction pathway and it improved the electron transfer ability of the substrate. It was found that the Ni/CP electrode exhibited good electrocatalytic oxidation behaviour towards glucose. Amperometric responses showed a good linear relationship with glucose concentration in the range from 2 μM to 500 μM with a detection limit of 0.6 μM. Thus this material is expected to have wide potential applications in glucose biosensors.

Full text of DOI:10.1039/c5ra09487a

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Characterization and electrochemical properties of
a nickel film/carbon paper electrode prepared by a
filtered cathodic vacuum arc technique
Cite this: RSC Adv., 2015, 5, 54777
a
a
a
ab
*
Yingyi Fu, Wen Su, Tong Wang and Jingbo Hu
A nickel film was prepared through plasma deposition of a metal onto a carbon paper (CP) substrate with the
filtered cathodic vacuum arc technique. Nickel metal plasma was generated at a current of 90 A and
deposited on the CP substrate for 3 seconds, forming the nickel film modified electrode. The
morphology image of the nickel film on the substrate surface was characterized by scanning electron
microscopy (SEM). The existence of the nickel film was verified by energy dispersive spectroscopy (EDS)
and X-ray photoelectron spectroscopy (XPS). The results of the water contact angle measurement (WCA)
showed that the existence of the nickel film improved the hydrophilicity of the CP. Cyclic voltammetry
(CV) was carried out to investigate the electrochemical properties of the Ni/CP electrode. The nickel film
provided a good electron conduction pathway and it improved the electron transfer ability of the
substrate. It was found that the Ni/CP electrode exhibited good electrocatalytic oxidation behaviour
Received 20th May 2015
Accepted 16th June 2015
towards glucose. Amperometric responses showed
a good linear relationship with glucose
DOI: 10.1039/c5ra09487a
concentration in the range from 2 mM to 500 mM with a detection limit of 0.6 mM. Thus this material is
www.rsc.org/advances
expected to have wide potential applications in glucose biosensors.
produces high density metal plasma. However, there are some
macroparticles in the produced metal plasma. In order to
1. Introduction
obtain high quality thin lm, these macroparticles must be
removed. There are a few methods to remove the macro-
particles, such as using mechanical blades lter, pulsed tech-
nique and magnetic lter.21–23 Magnetic lter method has been
used extensively and we adopted it to achieve the goal. Metal
plasma will move along the direction of magnetic eld and
reach the vacuum chamber, however the macroparticles
won't.24,25 By means of magnetic lter technique, we can obtain
homogeneous metal plasma. Finally, the metal plasma will be
deposited on the CP in vacuum chamber in a very short time.
Compared this technique with other modication methods
which mentioned above, such as electrochemical deposition
and chemical reduction, this technique can modify the wanted
lms on the substrate materials directly without any chemical
reagent or complex process. The modication process is facile
and fast. Besides, the magnetic lter technique provides
modied electrode with long-term stability and the thickness of
lms can be controlled by operating conditions.23,26–30
Ni-based materials have drawn great attention in battery cath-
odes, catalysts and biosensors due to their low toxicity, good
electrochemical stability and catalytic properties.1–4 Ni materials
have a unique electrocatalytic effect which arises from the
unpaired d electrons and vacant d-orbitals. It is also well known
that nickel and nickel hydroxide exhibit electrochemical activity
in alkaline medium.5–7 There are several methods to fabricate Ni
material, such as electrochemical deposition,8 chemical reduc-
tion,9 seed-mediated growth10 and electrospinning.11 However,
the need of chemical reagents and the complex process of these
methods are unfavourable for the electrode preparation. In the
present paper, we fabricate nickel thin lm on the carbon paper
(CP) surface with a new method, which is ltered cathodic
vacuum arc technique.
The ltered cathodic vacuum arc is an emerging technology
which has been used for various kinds of materials, such as
metals, metal oxides and metal nitrides, doped and undoped
semiconductors.12–18 The vacuum cathodic arc has been
employed extensively as a method of fabricating thin lm with
origin that can be traced back 1892 with a patent of Edison.19,20
This technique utilizes the cathode vacuum arc discharge and
CP is a kind of carbon ber material, which has good
compatibility, high specic surface area, excellent electrical
conductivity, low resistivity and stable chemical properties.
Besides, low cost carbon paper, unlike other substrate mate-
rials, can be cut out in any size at any time.31–34 These properties
of CP make it a suitable substrate material.
aCollege of Chemistry, Beijing Normal University, Beijing 100875, PR China. E-mail:
hujingbo@bnu.edu.cn; Fax: +86 10 58802075; Tel: +86 10 62209398
bKey Laboratory of Beam Technology and Material Modication of Ministry of
Education, Beijing Normal University, Beijing 100875, PR China
In the present paper, we selected CP as a substrate and
deposited nickel thin lm on it by ltered cathodic vacuum arc
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technique. The Ni/CP material was characterized by scanning that the surface is not smooth and there are many grooves on
electron microscope (SEM), energy dispersive spectroscopy the surface of CP (Fig. 1C). Aer deposition, no obvious
(EDS), X-ray photoelectron spectra (XPS) and water contact morphology changes are observed and the tubular carbon bres
angle measurement (WCA). As an electrode material, the elec- still exist (Fig. 1D). This phenomenon might be due to the
trochemical behaviour of Ni/CP was revealed by cyclic voltam- characteristic of the technique which modies the electrode
metry (CV) and chronoamperometry. The results showed that without damage. In Fig. 1D, no macroparticles on the carbon
the modied electrode Ni/CP exhibited ideal electrochemical paper are observed aer deposition, which demonstrates that
and electrocatalytic properties.
the magnetic lter method works effectively. The EDS spec-
trums (Fig. 1E and F) indicate the presence of Ni on the surface
of CP aer modication. These results above demonstrate that
the Ni lm was modied on the surface of CP successfully.
2. Experimental
2.1. Apparatus
3.2. XPS measurement of Ni/CP electrode
Filtered cathodic vacuum arc deposition was carried out with
the Beijing Normal University (BNU) FAD-MEVVA. X-ray
photoelectron spectroscopy (XPS) data was taken on an AXIS
Ultra spectrometer (Shimadzu, Japan). The scanning electron
microscope (SEM) and energy dispersive spectroscopy (EDS)
results were acquired with Hitachi X650 (Hitachi X650, Japan).
The water contact angle measurement (WCA) was performed
with the OCA15EC contact angle goniometer (Dataphysics
Instruments GmbH, Germany). All of the electrochemical
The chemical composition of the Ni/CP electrode was studied by
XPS further (Fig. 2). As shown in Fig. 2, there are no nickel peaks
on the CP electrode (curve A). However, two typical Ni 2p peaks
are observed at about 852.5 eV (2p3/2) and 869.8 eV (2p1/2) (curve
B), with a spin–orbit splitting of 17.3 eV. The data demonstrate
that the nickel thin lm immobilized on the electrode surface is
in the zero valent metallic state (Ni0). The satellite peak at
861.1 eV corresponds to Ni (2p3/2). In addition, Ni 2p3/2 peak at
about 855.8 eV and Ni 2p1/2 at about 873.5 eV indicate the
existence of Ni2+ on the electrode.35–39 From the results above, it
can be concluded that Ni0 and Ni2+ both exist on the nickel lm
surface.
The XPS spectra can also check the chemical states of oxygen
element in the CP and Ni/CP electrode. As it can be seen from
the O 1s spectra of CP electrode (Fig. 3A), the peak at 531.8 eV
corresponds to C–O, the O concentration on the surface of CP is
approximately 5.3%. Aer nickel lm was modied on CP, the
peak O 1s states can be divided into three components (Fig. 3B).
The peaks at 532.8 eV, 531.8 eV and 529.3 eV are indications of
the presence of C]O, C–O and metal oxide, respectively.35,40,41
The concentration of O increases to 31.7%, which might origi-
nate from the formation of metal oxide. These results are
consistent with the Fig. 2, metal nickel exists in the form of zero
valent and metal oxide state on the CP.
measurements were performed with
a CHI660D electro-
chemical workstation (CH Instruments, USA) at room temper-
ature. A traditional three-electrode system was applied with a
bare or modied carbon paper electrode (A ¼ 30 mm2) as the
working electrode, an Ag/AgCl electrode (saturated KCl) as the
reference electrode and a platinum wire electrode as the counter
electrode.
2.2. Reagents
CP was purchased from Shanghai Hephas Energy Company
Limited. All of the chemical reagents were of analytical grade
and solutions were dissolved with triple distilled water. All of
the measurements were carried out at room temperature.
2.3. Fabrication of nickel lm on carbon paper
Filtered cathodic vacuum arc deposition was carried out using
BNU FAD-MEVVA. High density nickel plasma was produced
using cathodic vacuum arc discharge technique at 90 A. Mac-
roparticles in metal plasma can be removed through the
magnetic lter. Aer that, nickel plasma was deposited on the
CP surface at 0 V. The deposition process continued for
3 seconds, forming the Ni/CP electrode. Before being used, the
modied electrode was washed with distilled water and ethanol
for several times.
3.3. WCA measurement of Ni/CP electrode
WCA measurements were applied to evaluate the surface
hydrophilicity of both the original CP electrode and the Ni/CP
electrode (Fig. 4). The measurements were carried out with
2 mL water droplet placed on the surface of the electrode. The
contact angles of the CP and Ni/CP electrodes were 130.7ꢀ and
118.1ꢀ, respectively. The smaller contact angle value of Ni/CP
electrode compared to that of the CP electrode illustrates that
the modication of the nickel lm improves the hydrophilicity
of the substrate. The increase in hydrophilicity of Ni/CP elec-
trode benets to the reaction of electroactive substance on the
electrode surface.
3. Results and discussion
3.1. Morphological characterization
The morphologies of the Ni/CP electrode were characterized by
scanning electron microscopy (SEM). As can be seen in Fig. 1A
and B, we can obtain the rough morphology of CP that many
3.4. Electrochemical characterization of Ni/CP electrode
interlaced tubular carbon bres dispersed randomly. In the CV was employed to investigate the electrochemical behaviour
cross-sectional views of carbon paper, we can see that the of the CP and Ni/CP electrode with the redox system serving as
carbon bres stacked optionally and the interval between each the probe such as [Fe(CN)6]3ꢁ/[Fe(CN)6]4ꢁ. Fig. 5 showed CVs for
other is different. In high magnication of SEM, we can observe an aqueous solution of 5 mM [Fe(CN)6]3ꢁ/[Fe(CN)6]4ꢁ in 0.1 M
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Fig. 1 SEM spectrum of bare CP in low magnification (A), bare CP of cross-sectional views (B), bare CP in high magnification (C), Ni/CP in high
magnification (D) and EDS spectrum of bare CP (E) and Ni/CP electrode (F).
KCl at a scan rate of 100 mV sꢁ1. KCl acted as supporting
electrolyte in the solution, a mass of anions (Clꢁ) and cations
(K+) surrounded around the anode and the cathode, therefore
the electrostatic attraction between electrode and measured
ions was reduced and the migration current generated by
electrostatic attraction was eliminated. Through added KCl, the
migration current was eliminated and the electrode process was
control by diffusion completely. These made the experiment
result more accurate. CV of the CP electrode exhibits a pair of
well-dened oxidation and reduction peak with a peak-to-peak
separation (DEp) of 323 mV (curve A). Aer deposition of
nickel lm on the CP substrate, a pair of characteristic oxidation
and reduction peaks was obtained. The anodic and cathodic
peak potentials move negatively and positively, with a DEp of
270 mV (curve B). Besides, the oxidation and reduction peak
currents are higher than those of the CP electrode. Compared to
Fig. 2 XPS spectrum for Ni 2p of CP electrode (A) and Ni/CP
electrode (B).
the CP electrode, the decrease of the DEp of Ni/CP electrode
indicates that the property of Ni/CP is better than CP electrode.
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Fig. 3 XPS spectrum for O 1s of CP electrode (A) and Ni/CP electrode (B).
solution was investigated. CVs of the Ni/CP electrode in 0.1 M
NaOH aqueous solution in the absence (A) and presence (B) of
1 mM glucose are shown in Fig. 6. Curve A shows a pair of redox
peaks of Ni2+/Ni3+ at 0.64 V and 0.50 V in alkaline medium. Upon
the addition of 1 mM glucose, the anodic peak current increases
and the cathodic peak current decreases (curve B), illustrating
that Ni/CP electrode exhibits excellent electrocatalytic ability
towards the oxidation of glucose. The increase of oxidation
current is ascribed to the production of Ni(OH)2 from the reac-
tion between NiOOH and glucose. The produced Ni(OH)2 is
further oxidized to NiOOH at the electrode surface. In addition,
the anodic peak potential moves from 0.64 V to 0.67 V and the
reason of that may be due to the diffusion limitation of glucose
at the electrode surface. As indicated in literatures,45–47 the
glucose can be oxidized to gluconolactone by NiOOH, which
produced by the oxidation of Ni(OH)2. The mechanism of the
glucose oxidation process can be illustrated as follows:
Fig. 4 Contact angles of CP electrode (A) and Ni/CP electrode (B).
These results demonstrate that the modication of nickel lm
can accelerate the electron transfer rate between the electrode
surface and [Fe(CN)6]3ꢁ/[Fe(CN)6]4ꢁ in aqueous solution and
exhibit good electrical properties. So we believe that the nickel
lm has been successfully deposited on the CP surface and
provide good electron conduction pathway which is suitable for
electrochemical sensor.
Ni(OH)2 + OHꢁ / NiOOH + H2O + eꢁ
NiOOH + glucose / Ni(OH)2 + gluconolactone
The effect of scan rate on oxidation peak current and
3.5. The electrocatalytic oxidation of glucose
Nickel material modied electrode exhibits favorable electro-
catalytic effects towards some biomolecules.42–44 To characterize
the electrocatalytic ability of Ni/CP electrode, the electro-
reduction peak current with
1 mM glucose has been
oxidation behaviour towards glucose in alkaline aqueous
Fig. 5 Cyclic voltammograms of CP electrode (A) and Ni/CP electrode Fig. 6 CVs of the Ni/CP electrode without (A) and with (B) 1 mM
(B) in 5 mM [Fe(CN)6]3ꢁ 4ꢁ solution at scan rate of 100 mV sꢁ1 glucose in 0.1 M NaOH. Scan rate: 100 mV sꢁ1
/
.
.
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Fig. 7 (A) CVs of the Ni/CP electrode in 0.1 M NaOH with 1 mM glucose at scan rates of 20, 40, 60, 80, 100, 125, 150, 175, 200, 225, 250, 275,
300 mV sꢁ1. Inset: the plots of peak current versus the square root of the scan rate. (B) Plot of the variation of anodic peak potential versus
logarithm of the scan rates.
controlled process. The value of electron transfer coefficient
(a) can be obtained from the equation of Epa ¼ 0.11862 log v +
0.43502. According to Laviron,48 the slope of the plot of Epa
versus the logarithm of scan rate is 2.3RT/(1 ꢁ a)nF and the
value of a was calculated to be 0.5.
Fig. 8 presents a typical amperometric response of Ni/CP
upon the successive addition of a certain concentration of
glucose at the potential of 0.67 V. The amperometric current
response was increased linearly with the increasing glucose
concentration in the range of 2 to 500 mM with a correlation
coefficient of 0.9916. The detection limit is found to be 0.6 mM.
The linear range and the detection limit of Ni/CP are compared
with those of other modied electrodes in Table 1. The good
catalytic effect and the simple preparation process make Ni/CP
as a potential material in glucose detection.
Fig. 8 Amperometric current response of Ni/CP electrode for the
successive addition of 50 mM glucose. Applied potential: 0.67 V. Inset
A: amperometric current response for successive addition of 2 mM,
4 mM and 5 mM glucose. Inset B: the plot of electrocatalytic current of
current of glucose versus the corresponding concentration.
4. Conclusions
Carbon paper substrate was deposited with nickel lm at 90 A in
3 seconds by the technique of ltered cathodic vacuum arc,
forming the Ni/CP electrode. The obtained Ni lm was charac-
terized by SEM, EDS, XPS, WCA and CV. The results of them
investigated in the range of 20–300 mV sꢁ1 (Fig. 7). Both the
anodic and the cathodic peak current are linearly proportional
to the square root of the scan rate, indicating a diffusion-
conrmed that the nickel lm was deposited on the CP surface
successfully and it improved the hydrophilicity and electron
transfer ability of the substrate. The Ni/CP electrode exhibited
good catalytic ability towards the oxidation of glucose in alka-
line solution with wide linear range and low detection limit.
Thus, the Ni/CP electrode is a promising material in the
development of non-enzymatic glucose sensor.
Table 1 Comparison of Ni/CP with other reported modified elec-
trodes for glucosea
Linear range
Detection limit
Type of electrode
(mM)
(mM)
Reference
NiO/FTO
Ni-MWCNT/GCE
Ni/ITO
NiO/CPEs
Ni/CP
10–800
3.2–17 500
1–350
1–110
2–500
1.2
0.89
0.5
0.16
0.6
10
46
49
45
Acknowledgements
This research was supported by the Fundamental Research
Funds for the Central Universities (Grant no. 2012YBXS09) and
the Key Laboratory of Beam Technology and Material Modi-
cation of Ministry of Education, China.
This work
a
FTO: uorine-doped tin oxide glass.
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24 V. Belous, V. Vasyliev, V. Goltvyanytsya, S. Goltvyanytsya,
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