22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Influence of temperature on synergistic CO 2 decomposition using hybrid reactor
of DBD-solid oxide electrolyser cell
L.L.Tun, N. Matsuura and S. Mori
Chemical Engineering Department, Tokyo Institute of Technology, Japan
Abstract: Carbon dioxide was decomposed using a hybrid reactor of DBD-Solid Oxide
Electrolyser Cell (SOEC). The shift of CO 2 decomposition equilibrium in the plasma was
observed when the oxidation of carbon monoxide was suppressed with the separation of
oxygen by SOEC. The influence of temperature was investigated in order to enhance the
decomposition.
Keywords: plasma, solid oxide electrolyser cell, hybrid reactor, temperature
1. Introduction
Carbon dioxide (CO 2 ) decomposition has been the
interest of the researchers in Plasma Chemistry. It is being
investigated by various discharge systems [1-10]. The
complete decomposition of CO 2 by the plasma, however,
seems to be difficult because intensive reverse reaction is
unavoidable. In our laboratory, for example, CO 2
conversion by plasma using capillary discharge tubes was
studied. It was deduced that a significant amount of CO 2
equilibrates with carbon monoxide (CO) and gas phase
reverse reactions occur even in a capillary plasma reactor
[3].
Meanwhile, electrochemical reduction of carbon
dioxide was investigated by SOEC and temperature above
700ºC was recommended for CO 2 electrolysis [5].
Obviously, the decomposition of CO 2 molecules can be
achieved using SOEC. There is another important
property of SOEC; oxygen is removed from the reactant
and the product gas [7]. Therefore, SOEC is capable of
suppressing the reverse reaction to form CO 2 from CO
with O 2 , O and O2-. However, working temperature of
SOEC was relatively high [10]. At higher operating
temperature, one concern may be to control the heat
inside the reactor.
In this study, we introduce the hybrid reactor of DBD
and SOEC in order to achieve the synergistic CO 2
decomposition of DBD plasma with the faster separation
of O 2 from the reaction zone by utilizing SOEC. The aim
of this paper is to examine the influence of temperature in
synergistic CO 2 decomposition using the hybrid system
of DBD-SOEC.
2. Experimental
A hybrid reactor was assembled using SOEC and DBD.
SOEC was composed of YSZ tube (electrolyte) which has
an outer diameter of 15 mm with 2 mm thickness as well
as LSM thin layer (electrodes) and the chromel wire
(ground electrode). Then, SOEC was inserted into a
quartz tube. The DBD reactor was composed of a quartz
tube of 500 mm length, 22 mm outer diameter, and 18
mm inner diameter. It was connected to the gas inlet and
outlet line by stainless steel union tees.
O-15-3
The quartz tube was covered with the stainless steel
mesh as a plasma electrode. The AC power supply (18
kHz) was applied between the plasma electrode and the
wrapped chromel wire to generate CO 2 plasma. The
maximum DBD applied voltage was set up to 11 kV and
the highest DBD power was approximately 39 W. SOEC
was evacuated with a rotary vacuum pump to increase
desorption
of
the
permeated
oxygen.
Gas
Chromatography (Shimadzu GC-8A) was used to analyse
the decomposed product.
Fig. 1. Schematic of the hybrid reactor.
3. Results and Discussion
Figure 2 represents the experimental results of CO 2
conversion with various values of DBD power.
Fig. 2. CO 2 conversion with DBD power.
1
In single DBD system, conversion slightly increases
with DBD power and, then the saturation arises after a
certain DBD power. However, the hybrid system shows
the significant increase in conversion with DBD power. It
could be the coinciding of CO 2 decomposition by DBD
plasma and permeation of O 2 by SOEC. Hereafter, the
saturation which usually occurs in the plasma reactor
seems to be overcome. Using the hybrid system, the shift
of CO 2 decomposition equilibrium in the plasma and the
suppression of the reformation of CO 2 occur.
Figure 3 shows the profile of CO 2 conversion with
SOEC current, and O 2 permeation profile in the hybrid
system. When DBD and SOEC are operated
independently, the maximum CO 2 conversions are about
15 % for DBD plasma reactor and 3 % for SOEC system.
However, the maximum CO 2 conversion by the hybrid
reactor is almost 93 %, much higher than the sum of the
conversions of DBD and SOEC.
chance in recombination of the decomposed gases.
Therefore, when the permeation current of SOEC is high
enough to remove oxygen completely from the CO 2
plasma region as shown in Fig.3, the synergistic effect of
the hybridization becomes apparent, and CO 2 conversion
increases drastically with oxygen removal.
The influence of temperature on CO 2 conversion is
examined as shown in Fig. 4. In the DBD system, the
increase in temperature occasionally influences the
conversion. There is an instantaneous increase in
conversion with the increase of reaction temperature in
the hybrid system as well as in the single SOEC system.
This is the high temperature preference of SOEC.
Fig. 4. CO 2 conversion as a function of temperature.
As illustrated in Fig.4, the advantage of the hybrid
reactor is observable at 500 ºC. In the hybrid system,
conversion is significantly higher than both DBD and
SOEC single systems at 500 ºC and complete conversion
performs at 600 and 700 ºC. Although SOEC system
enhances O 2 permeation more effectively at higher
temperature, hybrid reactor shows the feasibility of lower
working temperature. However, we still need to
investigate more efficient optimum conditions to
decompose CO 2 using the hybrid system.
Fig. 3. CO 2 conversion and O 2 removal with SOEC
current.
It can be seen clearly in Fig.3 that the increase in CO 2
conversion is correlated with the decrease in O 2 content
in the reaction zone. SOEC suppresses the reverse
reaction of CO 2 formation from CO and O 2 , and, then this
condition enhances the decomposition. This result could
be the synergistic effect in a hybrid system: simultaneous
processes of decomposition by plasma and removal of
oxygen by SOEC to overcome the saturation of CO 2
dissociation. The lower the oxygen content, the less
2
4. Conclusions
In this study, we investigated the synergistic CO 2
decomposition using the hybrid reactor of DBD-SOEC
and the influence of temperature in the hybrid system was
studied. It was observed that CO 2 decomposition by DBD
plasma was enhanced with the removal of oxygen by
SOEC. Although SOEC is more effective at high
operating temperature, hybridization with DBD could be
an operative way to decompose CO 2 at lower working
temperature.
5. Acknowledgements
Schlumberger: Faculty for the Future Programme is
sincerely acknowledged.
O-15-3
6. References
[1] Michael R.Thorson, Karl I. Siil, and Paul J. A. Kenis,
Journal of the Electrochemical Society, 160 (1) F69
F74 (2013).
[2] F. Bidrawn, G. Kim, G. Corre, J. T. S. Irvine, J. M.
Vohs and R. J. Gorte, Electrochemical and Solid-State
Letters, 11 (9) B167-B170 (2008).
[3] Shinsuke Mori, Aguru Yamamoto and Masaaki
Suzuki, Plasma Sources Sci. Technol. 15, 609–613
(2006).
[4] Sunghyun Uhm and Young Dok Kim, Current
Applied Physics, 672-679, 14 (2014).
[5] Jingbo Yan, Hao Chen, Emir Dogdibegovic, Jeffry W.
Stevenson, Mojie Cheng, Xiao-Dong Zhou, Journal of
Power Sources 79-84, 252 (2014).
[6] H. Guo, B. S. Kang, and A. Manivannan, ECS
Transactions, 50 (49) 129-136 (2013).
[7] Paolo Iora and Paolo Chiesa, J.Power Sources 408416,190 (2009).
[8] Widiatmini Sih Winanti ,Widodo Wahyu Purwanto
and Setijo Bismo, International Journal of
Technology, 1-11, 1 (2014).
[9] Ruixing Li, Qing Tang, Shu Yin, Yukishige
Yamaguchi, and Tsugio Sato Chemistry Letters
Vol.33, No.4 (2004).
[10] Arnoldus Lambertus Dipu, Yutaka Ujisawa, Junichi
Ryu, Yukitaka Kato, Nuclear Engineering and
Design 30–35, 271 (2014).
O-15-3
3