In this work, we address the issue of controlled modification of the surface topography of carbon materials when subjected to oxygen-based plasma treatment, and we investigate the resulting enhanced surface area as a mean of controlling the
capacitance of supercapacitors. It is shown that carbon layers with porous of controllable nanoscale size can be tuned from nanoporous to mesh-like employing atmospheric plasma torch deposition technology and following appropriate plasma
processing. The nanoscale carbon processing is optimized to form surface topographies that promote carbon wettability with electrolyte. Three dimensional structures fabricated on carbon are chosen as appropriate surfaces for the enhancement of the
capacitance of supercapacitors. This fact underlines the potential application of the proposed technique for fabricating electrolyte-wetted carbon electrodes for supercapacitors.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2086

Pranevicius, L.

In this work, we address the issue of controlled modification of the surface topography of carbon materials when subjected to oxygen-based plasma treatment, and we investigate the resulting enhanced surface area as a mean of controlling the capacitance of supercapacitors. It is shown that carbon layers with porous of controllable nanoscale size can be tuned from nanoporous to mesh-like employing atmospheric plasma torch deposition technology and following appropriate plasma processing. The nanoscale carbon processing is optimized to form surface topographies that promote carbon wettability with electrolyte. Three dimensional structures fabricated on carbon are chosen as appropriate surfaces for the enhancement of the capacitance of supercapacitors. This fact underlines the potential application of the proposed technique for fabricating electrolyte-wetted carbon electrodes for supercapacitorsFizikos katedraVytauto Didžiojo universiteta

Pranevičius, Liudvikas

Vytautas Magnus University Institutional Repository (VMU ePub)

Tailoring of surface topography of carbon electrodes for supercapacitors using plasma technologies

Electronic Sumy State University Institutional Repository

448                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II              TAILORING OF SURFACE TOPOGRAPHY OF CARBON ELECTRODES FOR SUPERCAPACITORS USING PLASMA TECHNOLOGIES Liudvikas Pranevicius  Vytautas Magnus University, Vileikos str.8, 44404, Kaunas, Lithuania  ABSTRACT In this work, we address the issue of controlled modification of the surface topography of carbon materials when subjected to oxygen-based plasma treatment, and we investigate the resulting enhanced surface area as a mean of controlling the capacitance of supercapacitors. It is shown that carbon layers with porous of controllable nanoscale size can be tuned from nanoporous to mesh-like employing atmospheric plasma torch deposition technology and following appropriate plasma processing. The nanoscale carbon processing is optimized to form surface topographies that promote carbon wettability with electrolyte. Three dimensional structures fabricated on carbon are chosen as appropriate surfaces for the enhancement of the capacitance of supercapacitors. This fact underlines the potential application of the proposed technique for fabricating electrolyte-wetted carbon electrodes for supercapacitors.  Key words: supercapacitors, carbon electrodes, surface topography, and plasma technologies  INTRODUCTION  There is a need for a rechargeable energy source that can provide high power, can be recharged quickly, has a high cycle life and is environmentally benign for a myriad of applications including defence, consumer goods, and electric vehicles. Double layer capacitors known as supercapacitors are rechargeable charge storage devices that fulfil this need. A single-cell double layer capacitor consists of two electrodes which store charge (these are called the "active" materials), separated by a permeable membrane which permits ionic but not electronic conductivity. Each electrode is also in contact with a current collector which provides an electrical path to the external environment. The electrodes and the membrane are infused with an electrolyte, and the entire assembly is contained in inert packaging. Multiple cells may be connected in series or in parallel in the final packaged unit [1-3].  The capacitance, or amount of charge that a capacitor can store, is directly related to the surface area of the electrodes. Therefore, electrodes made from conductive materials that possess high surface area (>100 m 2 /g) are desirable. By employing various materials and fabrication means, Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II              449  capacitors have been developed which are capable of delivering very high specific power and energy densities. Because carbon is chemically inert, has a high electronic conductivity, is environmentally benign and is relatively inexpensive, it is a desirable material for fabricating electrodes for supercapacitors. A variety of porous forms of carbon are currently preferred as the supercapacitor electrode materials because they have exceptionally high surface areas, relatively high electronic conductivity, and acceptable cost. Since only the electrolyte-wetted surface-area contributes to capacitance, the nanoscale carbon processing is required to form surface topographies that promote carbon wettability with electrolyte [4,5]. This article concerns the energy storage devices and specifically to a method of making active materials or electrodes. The purpose of this research paper is focused on the surface modification of carbon electrodes using plasma techniques,  so  as  to  control  the  increase  in  surface  roughness  in  order  to  improve the capacitance of supercapacitors. In this study, the surfaces of the carbon electrodes were chemically and physically modified by their exposure in low-pressure oxygen plasma. The treated and untreated (as-received) surfaces of the carbon electrodes were subjected to detailed characterization.  EXPERIMENTAL  The experimental includes two parts: (i) the fabrication of thick porous carbon electrodes on stainless steel substrates employing atmospheric plasma torch carbon deposition technology, and (ii) the modification of surface proper-ties  of  carbon  electrodes  by  their  exposure  in  low  pressure  oxygen  plasma  to  achieve the highest performance parameters of supercapacitors.  The porous 50 µm thick carbon coatings were deposited on 2 mm thick 1X18H9T stainless steel substrate employing atmospheric plasma torch tech-nology. Details of this technique are disclosed in [6]. The plasma torch parame-ters were as follows: the arc voltage – 36 V, the arc current – 24 A, the working gas – the mixture of Ar and C2H2, and the deposition time – 150 s. The gas flow and gas composition was continuously controlled by mass flow controllers. The thickness of the deposited layer was evaluated by weight method using micro-balances. The modification of surface properties of deposited carbon layers was per-formed by high-flux, low-energy ion irradiation. The ions were extracted from DC magnetron plasma generated at 5 Pa pressure in the mixture of Ar and O2 (10 at.%) and accelerated by 350 V negative bias voltage. The magnetron dis-charge current was variable in the range 10-20 mA. The power density dissipat-ed in plasma was variable in the range 100 - 300 Wcm–2. The plasma parame-ters were evaluated experimentally using a Langmuir probe. For plasma source, the electron temperature, plasma potential, floating potential and plasma densi-ty were 2-4 eV, +5.0 V, +3.5 V and 41010 cm-3, respectively. The steady state 450                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II              substrate temperature of 480 K reached after two minutes of plasma treatment. The characterization of surface topography of as-deposited and plasma treated carbon electrodes were carried out using the atomic force microscope (Micro-mashines NT-206) and the nanoprofilometer (Ambios XP-200). The surface views were analyzed before and after plasma treatment by a scanning electron microscopy (SEM, JEOL JSM – 5600). The elemental composition of plasma treated carbon coatings was analyzed by energy dispersive X–ray spectroscopy (EDX, Bruker Quad 5040). RESULTS The surface topography of carbon layers fabricated employing atmospheric plasma torch technology has been studied in previous publications [6,  7].  In  this  work,  the  attempts  to  explain   why  the  capacitance  of  supercapacitors with C electrodes increases after their additional treatment in Ar+O2 plasma.  Fig.1 includes the dependence of the ratio of capacitances for supercapacitors with C electrodes treated and untreated in oxygen plasma (10 Pa, 1 min) on the flux ratio of Ar/C2H2 for plasma torch. It is seen that the capacitance increases up to 10 times for Ar/C2H2=55.  Fig.2a and Fig.2b include SEM surface views of carbon electrodes: a - as-deposited employing atmospheric pressure plasma torch technology for flux ratio Ar/C2H2=40, and b - after following treatment in low-pressure oxygen plasma (10 Pa, 1 min), respectively. It seen that the granular structure of as-deposited carbon becomes highly porous with channels accessible for electrolyte.  Fig. 2. – The SEM surface views of carbon electrodes: a – as-deposited, b – after treatment in oxygen plasma  Fig.1 – The dependence of the ratio of capacitances for supercapacitors with C electrodes treated and untreated in oxygen plasma (10 Pa, 1 min) on the flux ratio of Ar/C2H2 [7] 02468100 20 40 60Capacitance ratioFlux ratio Ar/C2H2Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II              451  MODELLING OF SURFACE STRUCTURE FORMATION The modelling of surface structure formation has been performed in an at-tempt to explain the significant increase of the capacitance of supercapacitor which was experimentally registered. The understanding of processes which lead to this effect is not complete.  The simultaneous action of three processes has been considered on the surface of carbon electrode immersed in O2+Ar plasma: (i) the isotropic plas-mochemical etching of C (C+2OĺCO2Ĺ), (ii) the adsorption of C atoms, and (iii) the anisotropic physical sputtering of surface by energetic incident oxygen and argon ions.  Fig.3 includes profiles of single carbon formation calculated on the basis of kinetic equations describing simultaneous action of the processes of carbon deposition, isotropic plasmochemical and anisotropic physical ion sputtering after different durations of plasma treatment (to=0, 1, 2, 3, and 4, curves 1 -5, respectively) in relative units for the case when the carbon deposition rate is equal to the plasmochemical etching rate (Fig.3a) , and when the carbon deposition rate exceeds the carbon plasmochemical etching rate (3X)(Fig.3b).  Curve 1 - the initial profile. It is demonstrated that different surface structure formations may be generated in dependence on the deposition and plasma treatment parameters.   Fig.3. – Calculated profiles of single carbon formation on the surface of plasma treated carbon for different deposition/etching  parameters:  a – the deposition and plasmochemical etcing rates are equal, and b – the deposition exceeds plasmochemical etching rate (3X)  after different treatment durations: t=0 (as deposited), 1, 2, 3 and 4 in relative units, curves 1-5, respectively  DISCUSSIONS AND CONCLUSIONS The surface topography of carbon materials has been optimized to promote carbon wettability with electrolyte and to increase the capacitance of superca-pacitors. High capacity of supercapacitor is obtained due to fabrication of po-rous electrodes with surface topography accessible for electrolyte to form dou--1,0 -0,5 0,0 0,5 1,00,20,40,60,81,0  t0 t1 t2 t3 t4Radius r/r0, rel.u.Heigth h/h 0, rel.u.1 2 3 45-1,0 -0,5 0,0 0,5 1,0123456   t0 t1 t2 t3 t4 Radius r/r0, rel.u.Heigth h/h 0, rel.u.12345a b452                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II              ble charge layer. The carbon etching in oxygen plasma is accompanied by na-noscale changes of the surface geometry.  The oxygen plasma treatments caused ablation of the carbon electrode surface, removing carbon atoms and molecules such as CO and CO2. Carbon electrodes treated in oxygen plasma for 1-3 min significantly (up to 10 times) increases the capacitance of supercapacitor. This effect depends on the microstructure of plasma untreated carbon layers. The conclusion is made that the modification of surface topography of carbon elec-trodes by oxygen plasma is a suitable technique for the improvements of the electrical properties of supercapacitors.  Acknowledgments This research was funded by a grant (Nr. ATE-10022) from the Research Council of Lithuania. The authors acknowledge useful discussions with dr. Ž.Kavaliauskas and highly appreciate dr. D. Milþius and dr. V. Valinþius, the heads of the Center for Hydrogen Energy Technologies and Plasma Treatment Laboratory, respectively, for the access to experimental technique. REFERENCES [1] A. Burke, Electrochim Acta, 2007, Vol.53, P.1083 – 1091. [2] A. Pandolfo, A. Hollenkamp, J. Power Sources, 2006, Vol.157, P.11 – 27. [3] G. Yuan, Z. Jiang, A. Aramata, Y. Gao, Carbon, 2005, Vol.43, P.2913 – 2917. [4] L. L. Zhang, X. S. Zhao, Chem. Soc. Rev., 2009, Vol.38, P.2520-2531. [5] C.Portet, P.L.Taberna, P.Simon et al., Electrochimica Acta, 2005, Vol.50, P.4174-4181. [6] Z.Kavaliauskas, Investigation of supercapacitors with carbon electrodes obtained from argon-acetylene arc plasma, Doctoral thesis, Vytautas Magnus University, Kaunas, 2011. [7] Z. Kavaliauskas, L.L. Pranevicius, L. Marcinauskas, P. Valatkevicius, Mater. Sci., 2009, Vol.15, P.99 – 102    

SocioEconomic Challenges Journal (Sumy State University)

448                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II             
 
TAILORING OF SURFACE TOPOGRAPHY OF CARBON 
ELECTRODES FOR SUPERCAPACITORS USING 
PLASMA TECHNOLOGIES 
Liudvikas Pranevicius 
 
Vytautas Magnus University, Vileikos str.8, 44404, Kaunas, Lithuania 
 
ABSTRACT 
In this work, we address the issue of controlled modification of the surface 
topography of carbon materials when subjected to oxygen-based plasma treatment, and 
we investigate the resulting enhanced surface area as a mean of controlling the 
capacitance of supercapacitors. It is shown that carbon layers with porous of 
controllable nanoscale size can be tuned from nanoporous to mesh-like employing 
atmospheric plasma torch deposition technology and following appropriate plasma 
processing. The nanoscale carbon processing is optimized to form surface topographies 
that promote carbon wettability with electrolyte. Three dimensional structures 
fabricated on carbon are chosen as appropriate surfaces for the enhancement of the 
capacitance of supercapacitors. This fact underlines the potential application of the 
proposed technique for fabricating electrolyte-wetted carbon electrodes for 
supercapacitors. 
 
Key words: supercapacitors, carbon electrodes, surface topography, and plasma 
technologies 
 
INTRODUCTION  
There is a need for a rechargeable energy source that can provide high 
power, can be recharged quickly, has a high cycle life and is environmentally 
benign for a myriad of applications including defence, consumer goods, and 
electric vehicles. Double layer capacitors known as supercapacitors are 
rechargeable charge storage devices that fulfil this need. A single-cell double 
layer capacitor consists of two electrodes which store charge (these are called 
the "active" materials), separated by a permeable membrane which permits 
ionic but not electronic conductivity. Each electrode is also in contact with a 
current collector which provides an electrical path to the external environment. 
The electrodes and the membrane are infused with an electrolyte, and the entire 
assembly is contained in inert packaging. Multiple cells may be connected in 
series or in parallel in the final packaged unit [1-3].  
The capacitance, or amount of charge that a capacitor can store, is 
directly related to the surface area of the electrodes. Therefore, electrodes 
made from conductive materials that possess high surface area (>100 m 2 /g) 
are desirable. By employing various materials and fabrication means, 
Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II              449 
 
capacitors have been developed which are capable of delivering very high 
specific power and energy densities. Because carbon is chemically inert, has a 
high electronic conductivity, is environmentally benign and is relatively 
inexpensive, it is a desirable material for fabricating electrodes for 
supercapacitors. A variety of porous forms of carbon are currently preferred as 
the supercapacitor electrode materials because they have exceptionally high 
surface areas, relatively high electronic conductivity, and acceptable cost. 
Since only the electrolyte-wetted surface-area contributes to capacitance, the 
nanoscale carbon processing is required to form surface topographies that 
promote carbon wettability with electrolyte [4,5]. 
This article concerns the energy storage devices and specifically to a 
method of making active materials or electrodes. The purpose of this research 
paper is focused on the surface modification of carbon electrodes using plasma 
techniques,  so  as  to  control  the  increase  in  surface  roughness  in  order  to  
improve the capacitance of supercapacitors. In this study, the surfaces of the 
carbon electrodes were chemically and physically modified by their exposure in 
low-pressure oxygen plasma. The treated and untreated (as-received) surfaces 
of the carbon electrodes were subjected to detailed characterization.  
EXPERIMENTAL  
The experimental includes two parts: (i) the fabrication of thick porous 
carbon electrodes on stainless steel substrates employing atmospheric plasma 
torch carbon deposition technology, and (ii) the modification of surface proper-
ties  of  carbon  electrodes  by  their  exposure  in  low  pressure  oxygen  plasma  to  
achieve the highest performance parameters of supercapacitors.  
The porous 50 µm thick carbon coatings were deposited on 2 mm thick 
1X18H9T stainless steel substrate employing atmospheric plasma torch tech-
nology. Details of this technique are disclosed in [6]. The plasma torch parame-
ters were as follows: the arc voltage – 36 V, the arc current – 24 A, the working 
gas – the mixture of Ar and C2H2, and the deposition time – 150 s. The gas flow 
and gas composition was continuously controlled by mass flow controllers. The 
thickness of the deposited layer was evaluated by weight method using micro-
balances. 
The modification of surface properties of deposited carbon layers was per-
formed by high-flux, low-energy ion irradiation. The ions were extracted from 
DC magnetron plasma generated at 5 Pa pressure in the mixture of Ar and O2 
(10 at.%) and accelerated by 350 V negative bias voltage. The magnetron dis-
charge current was variable in the range 10-20 mA. The power density dissipat-
ed in plasma was variable in the range 100 - 300 Wcm–2. The plasma parame-
ters were evaluated experimentally using a Langmuir probe. For plasma source, 
the electron temperature, plasma potential, floating potential and plasma densi-
ty were 2-4 eV, +5.0 V, +3.5 V and 4?1010 cm-3, respectively. The steady state 
450                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II             
 
substrate temperature of 480 K reached after two minutes of plasma treatment. 
The characterization of surface topography of as-deposited and plasma treated 
carbon electrodes were carried out using the atomic force microscope (Micro-
mashines NT-206) and the nanoprofilometer (Ambios XP-200). The surface 
views were analyzed before and after plasma treatment by a scanning electron 
microscopy (SEM, JEOL JSM – 5600). The elemental composition of plasma 
treated carbon coatings was analyzed by energy dispersive X–ray spectroscopy 
(EDX, Bruker Quad 5040). 
RESULTS 
The surface topography of carbon layers fabricated employing 
atmospheric plasma torch technology has been studied in previous publications 
[6,  7].  In  this  work,  the  attempts  to  explain   why  the  capacitance  of  
supercapacitors with C electrodes increases after their additional treatment in 
Ar+O2 plasma.  
Fig.1 includes the dependence of 
the ratio of capacitances for 
supercapacitors with C electrodes 
treated and untreated in oxygen plasma 
(10 Pa, 1 min) on the flux ratio of 
Ar/C2H2 for plasma torch. It is seen that 
the capacitance increases up to 10 times 
for Ar/C2H2=55.  
Fig.2a and Fig.2b include SEM 
surface views of carbon electrodes: a - 
as-deposited employing atmospheric 
pressure plasma torch technology for 
flux ratio Ar/C2H2=40, and b - after 
following treatment in low-pressure 
oxygen plasma (10 Pa, 1 min), 
respectively. It seen that the granular structure of as-deposited carbon becomes 
highly porous with channels accessible for electrolyte. 
 
Fig. 2. – The SEM surface views of carbon electrodes: a – as-deposited, b – after 
treatment in oxygen plasma 
 
Fig.1 – The dependence of the ratio of 
capacitances for supercapacitors with C 
electrodes treated and untreated in 
oxygen plasma (10 Pa, 1 min) on the 
flux ratio of Ar/C2H2 [7] 
0
2
4
6
8
10
0 20 40 60
C
ap
ac
ita
nc
e r
at
io
Flux ratio Ar/C2H2
Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II              451 
 
MODELLING OF SURFACE STRUCTURE FORMATION 
The modelling of surface structure formation has been performed in an at-
tempt to explain the significant increase of the capacitance of supercapacitor 
which was experimentally registered. The understanding of processes which 
lead to this effect is not complete.  
The simultaneous action of three processes has been considered on the 
surface of carbon electrode immersed in O2+Ar plasma: (i) the isotropic plas-
mochemical etching of C (C+2O?CO2?), (ii) the adsorption of C atoms, and 
(iii) the anisotropic physical sputtering of surface by energetic incident oxygen 
and argon ions.  
Fig.3 includes profiles of single carbon formation calculated on the basis 
of kinetic equations describing simultaneous action of the processes of carbon 
deposition, isotropic plasmochemical and anisotropic physical ion sputtering 
after different durations of plasma treatment (to=0, 1, 2, 3, and 4, curves 1 -5, 
respectively) in relative units for the case when the carbon deposition rate is 
equal to the plasmochemical etching rate (Fig.3a) , and when the carbon 
deposition rate exceeds the carbon plasmochemical etching rate (3X)(Fig.3b).  
Curve 1 - the initial profile. It is demonstrated that different surface structure 
formations may be generated in dependence on the deposition and plasma 
treatment parameters.  
 
Fig.3. – Calculated profiles of single carbon formation on the surface of plasma treated 
carbon for different deposition/etching  parameters:  a – the deposition and 
plasmochemical etcing rates are equal, and b – the deposition exceeds plasmochemical 
etching rate (3X)  after different treatment durations: t=0 (as deposited), 1, 2, 3 and 4 in 
relative units, curves 1-5, respectively 
 
DISCUSSIONS AND CONCLUSIONS 
The surface topography of carbon materials has been optimized to promote 
carbon wettability with electrolyte and to increase the capacitance of superca-
pacitors. High capacity of supercapacitor is obtained due to fabrication of po-
rous electrodes with surface topography accessible for electrolyte to form dou-
-1,0 -0,5 0,0 0,5 1,0
0,2
0,4
0,6
0,8
1,0  t0
 t1
 t2
 t3
 t4
Radius r/r0, rel.u.
H
eig
th
 h/
h 0
, r
el.
u.
1 2 3 4
5
-1,0 -0,5 0,0 0,5 1,0
1
2
3
4
5
6
 
 
 t0
 t1
 t2
 t3
 t4
 
Radius r/r0, rel.u.
H
eig
th
 h/
h 0
, r
el.
u.
1
2
3
4
5
a b
452                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part II             
 
ble charge layer. The carbon etching in oxygen plasma is accompanied by na-
noscale changes of the surface geometry.  The oxygen plasma treatments caused 
ablation of the carbon electrode surface, removing carbon atoms and molecules 
such as CO and CO2. Carbon electrodes treated in oxygen plasma for 1-3 min 
significantly (up to 10 times) increases the capacitance of supercapacitor. This 
effect depends on the microstructure of plasma untreated carbon layers. The 
conclusion is made that the modification of surface topography of carbon elec-
trodes by oxygen plasma is a suitable technique for the improvements of the 
electrical properties of supercapacitors. 
 
Acknowledgments 
This research was funded by a grant (Nr. ATE-10022) from the Research 
Council of Lithuania. The authors acknowledge useful discussions with dr. 
Ž.Kavaliauskas and highly appreciate dr. D. Mil?ius and dr. V. Valin?ius, the 
heads of the Center for Hydrogen Energy Technologies and Plasma Treatment 
Laboratory, respectively, for the access to experimental technique. 
REFERENCES 
[1] A. Burke, Electrochim Acta, 2007, Vol.53, P.1083 – 1091. 
[2] A. Pandolfo, A. Hollenkamp, J. Power Sources, 2006, Vol.157, P.11 – 27. 
[3] G. Yuan, Z. Jiang, A. Aramata, Y. Gao, Carbon, 2005, Vol.43, P.2913 – 2917. 
[4] L. L. Zhang, X. S. Zhao, Chem. Soc. Rev., 2009, Vol.38, P.2520-2531. 
[5] C.Portet, P.L.Taberna, P.Simon et al., Electrochimica Acta, 2005, Vol.50, P.4174-
4181. 
[6] Z.Kavaliauskas, Investigation of supercapacitors with carbon electrodes obtained 
from argon-acetylene arc plasma, Doctoral thesis, Vytautas Magnus University, 
Kaunas, 2011. 
[7] Z. Kavaliauskas, L.L. Pranevicius, L. Marcinauskas, P. Valatkevicius, Mater. Sci., 
2009, Vol.15, P.99 – 102 
 
  


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Tailoring of surface topography of carbon electrodes for supercapacitors using plasma technologies

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