Selective, high efficiency reduction of CO2 in a non-diaphragm-based electrochemical system at low applied voltage

Article abstract of DOI:10.1039/c4ra14427a

In a typical electrochemical CO₂ reduction system, hydrocarbon products are not selectively generated when a diaphragm is used in the cell. However, without the diaphragm, H₂ and CH₄ are selectively produced with Faradaic efficiencies as high as 96.7% in methanolic NaOH and KOH electrolytes, respectively. We are the first to successfully achieve the selective production of hydrocarbon and hydrogen fuels from the electrochemical reduction of CO₂, which can help to meet the rapidly growing energy demands of modern society.

Full text of DOI:10.1039/c4ra14427a

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: K. Yim, D. Song,
C. Kim, N. Kim, K. Okuyama, T. Ogi, T. Iwaki, S. E. Lee and T. Kim, RSC Adv., 2014, DOI:
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Page 1 of 6
RSC Advances
View Article Online
DOI: 10.1039/C4RA14427A
RSC Advances
RSCPublishing
COMMUNICATION
Selective, High Efficiency Reduction of CO2 in a Non-
Diaphragm-Based Electrochemical System at Low
Applied Voltage
Cite this: DOI: 10.1039/x0xx00000x
KwangꢀJin Yim1†, DongꢀKeun Song2†, ChanꢀSoo Kim3†, NamꢀGyu Kim1, Toru
Iwaki4, Takashi Ogi4, Kikuo Okuyama4, SungꢀEun Lee5*b, TaeꢀOh Kim1*a
Received 00th January 2014,
Accepted 00th January 2014
DOI: 10.1039/x0xx00000x
www.rsc.org/
CO2 which did not use a diaphragm, as will be discussed.16–18
Abstract: In a typical electrochemical CO2 reduction system,
hydrocarbon products are not selectively generated when a
diaphragm is used in the cell. However, without the
diaphragm, H2 and CH4 are selectively produced with
Faradaic efficiencies as high as 96.7% in methanolic NaOH
and KOH electrolytes, respectively. We are the first to
successfully achieve the selective production of hydrocarbon
and hydrogen fuels from the electrochemical reduction of
CO2, which can help to meet the rapidly growing energy
demands of modern society.
Herein, we report the selective formation of CH4 and H2 as the final
products of CO2 reduction without use of a diaphragm. This is the
first example of the CO2 reduction reaction under these conditions.
In these experiments, we employed the alkaline salts NaOH and
KOH as electrolytes for the selective generation of hydrocarbons and
H2 at low applied voltage.
Traditional CO2 reduction is conducted in a reactor containing a
diaphragm (an ionꢀexchange membrane), cathode (working
electrode), anode (counter electrode), reference electrode, and
different electrolytes within separated compartments.19–27 In prior
studies of CO2 reduction, the diaphragm was used to suppress the
movement of unwanted intermediates to the reduction electrode and
selectively generate hydrocarbons.28 The diaphragm was also
employed to protect the reaction at the cathode from interference by
oxidation products and potential electrode poisons generated by the
anode.29 However, more complex product isolation processes may be
needed if various hydrocarbons, including the desired C1–Cn
compounds, are generated, because the formation of electrons and
protons on the anode in a diaphragmꢀcontaining reactor increases as
the applied voltage increases.30,31 The presumable drawbacks of CO2
reduction system without a diaphragm are uncertainty of proton
sources, hard to separate target compounds from unwanted products,
and occurrence of poisoned ions on Pt anode.14,32,37 Additionally, the
diaphragm, controlling the inflow of the intermediates, interferes
with the flow of the electrical current generated by the two
electrodes, resulting in the need for an overpotential for CO2
reduction.33 We considered that the use of a diaphragm may be a
hurdle for electrochemical reduction research, and its removal may
allow CO2 reduction with high Faradaic efficiency at a low applied
voltage. The diaphragm is suggested to be effective in controlling
hydrocarbon generation beyond CO and C1 compounds.34–36 Finally,
all the known processes (diaphragmꢀbased) for the electrochemical
The electrochemical reduction of CO2 is of increasing interest as an
alternative route for fuel production because of its environmental
and economic benefits. Its hydrocarbon and alcohol products will
become effective fossil fuel replacements as our energy resources
are depleted.1–3 CO2 is a thermodynamically stable compound, and
additional energy input is necessary to transform it by
electrochemical reduction.4 The reductive transformation of CO2
produces a variety of products according to the numbers of generated
electrons and protons. However, CO2 reduction competes with
hydrogen production, which occurs at a similar electrical potential.5,6
Therefore, an overpotential is needed to accomplish the reduction
efficiently.5,6 However, this overpotential for CO2 reduction results
in a dramatic decrease in energy efficiency, which has led many
researchers to develop methods to decrease applied voltages and
increase Faradaic efficiency.7–11 The approaches include
investigations of Cu electrodes, electrolytes (i.e., distilled water,
organic solvents/ionic liquids), alkaline salts (i.e., Li, Na, K, Rb, Cs,
and Fr), photocatalysts, and biological reduction.12–15 Despite all
these efforts, there has been no report of complete CO2 reduction
with high Faradaic efficiency at low applied voltage. To achieve
such results, we suggested an electrochemical reduction system for
This journal is © The Royal Society of Chemistry 2014
Chem. Sci., 2014, 00, 1-3 | 1

RSC Advances
Page 2 of 6
View Article Online
COMMUNICATION
RSC Advances
DOI: 10.1039/C4RA14427A
reductive transformation of CO2 to various hydrocarbons report intrinsic proton source. Accordingly, NaOH or KOH was used as the
difficulties in controlling the generation of specific products.37
electrolyte and methanol was used as the electrolytic solvent. The
Generally, the current density (CD) in an electrochemical reduction following reaction between these components produces alkoxides
is significantly affected by the number of electrons and protons. and water, as previously reported:39
Accordingly, additional voltage results in an increased CD, which
accelerates the reduction.
CH3OH + Na(K)OH ➛ CH3ONa(K) + H2O
(1)
Equation (1) describes the reaction of methanol and Na(K)OH upon
dissolution; water then dissociates to produce hydroxyl radicals
(OH•), protons, and H2. Furthermore, the rate of the production of
H2O with KOH is four times faster than with NaOH.40 Thus, it is
evident that the water produced via the reaction in Eq. (1) acts as a
proton source in the nonꢀdiaphragmꢀbased electrochemical system
(Figure S1). It is likely that the electrochemical reduction of CO2 by
combining with protons (H+) lowers the essential potential for the
reaction. In Equations (2) to (8), formal potentials have been
suggested for the standard state, defined as pH 7.0, 25°C, 1 atm, and
1 M solution.41 As these equations show, various intermediates are
formed during the reactions of protons and electrons with CO2.41
Until now, the reduction of CO2 to hydrocarbons has not been
selective, and was inefficient due to the generation of CO and
HCOOH. High efficiency and selectivity for particular products
during the reduction are strongly related to the electrodes and
electrolytes. However, the previous studies were limited by the
electrolyteꢀsolubility of CO2, which interferes with the reduction
Figure 1. Cyclic voltammogram on Cu electrode at a scan rate 50 reaction, and the generation of CO, which can poison the electrodes.
mV·s−1 and CO2 flow rate of 60 mL·min−1 and 25°C with different Interestingly, the previously observed CO, HCHO, and CH3OH
potentials, and impedance (IMP) values at a frequency of 10,000 Hz intermediates were not formed as final products within our system.
and amplitude of 500 mV in electrochemical systems with and After GCꢀMS analysis, only CH4 and methyl ester were produced in
without a diaphragm: (a) Voltammetric curve with 0.2 M KOH our electrochemical system and identified as intermediates (Figure
electrolyte; (b) Voltammetric curve with 0.2 M NaOH electrolyte; S2). With this result, it is clear that the products do not influence the
(c) IMP with 0.2 M KOH electrolyte; and (d) IMP with 0.2 M NaOH electrodes, confirming that the products are not affected by oxidation
electrolyte.
and/or reduction. Therefore, the main equations operating in this
study are Eq. (7) and (8), and the primary products are selectively
CH4 and H2.
The CDs of diaphragmꢀ and nonꢀdiaphragmꢀbased electrochemical
systems with 0.2 M KOH and 0.2 M NaOH electrolyte are shown in
Figure 1(a, b). The CD in the nonꢀdiaphragmꢀbased electrochemical
system was much higher than that in the diaphragmꢀbased cell. This
trend was also evident upon increasing the potentials. The
impedance (IMP) was measured to validate the generation of high
CDs in the nonꢀdiaphragmꢀbased electrochemical system. As shown
in Figure 1(c, d), the impedance results demonstrate that a
remarkably lowered resistance is the direct reason for the enhanced
CD in the nonꢀdiaphragmꢀbased electrochemical system in
comparison to that in diaphragmꢀbased one. Additionally, the
resistance with the 0.2 M NaOH electrolyte was lower than that with
the 0.2 M KOH electrolyte, which was consistent with the higher CD
observed for the NaOHꢀbased electrolyte system than that based on
KOH. Clearly, the NaOHꢀbased electrolyte produces more electrons
than the KOHꢀbased electrolyte because of its higher CD.
Additionally, without a diaphragm, the electrochemical system is
activated to generate electrons and protons and initiate their flow
within the electrolytes.
CO2 + e− → CO2
E0´ = −1.90 V
E0´ = −0.53 V
E0´ = −0.61 V
E0´ = −0.48 V
E0´ = −0.38 V
E0´ = −0.24 V
E0´ = −0.41 V
(2)
(3)
(4)
(5)
(6)
(7)
(8)
−
CO2 + 2H+ + 2e− → CO + H2O
CO2 + 2H+ + 2e− → HCOOH
CO2 + 4H+ + 4e− → HCHO + H2O
CO2 + 6H+ + 6e− → CH3OH + H2O
CO2 + 8H+ + 8e− → CH4 + 2H2O
2H+ + 2e− → 2H2
The diaphragm in an electrochemical system exchanges the alkaline
salt cations for protons; these protons are used to reduce CO2 and
generate hydrocarbons mixed with protons and H2. In the absence of
protons, the direct transfer of electrons and reduction requires an
overpotential, which reduces the efficiency of the transformation.
Therefore, protons play an important role in CO2 reduction.38 In the
absence of a diaphragm, our electrochemical system required an
2 | RSC. Adv., 2014, 00, 1-3
This journal is © The Royal Society of Chemistry 2014

Page 3 of 6
RSC Advances
RSC Advances
View Article Online
COMMUNICATION
DOI: 10.1039/C4RA14427A
Figure 2. Schematic diagrams for the electrochemical reduction of
CO2 with and without a diaphragm. The products were compared
according to the presence of a diaphragm under the same conditions,
using methanol as solvent, NaOH/KOH electrolytes, an applied
voltage range of 0.1–1 V, and a CO2 input rate of 60 mL·min−1 at
25°C.
Figure 2 illustrates the electrochemical CO2 reduction systems with
and without a diaphragm. It shows electrons at the applied voltage,
the types of products formed in the presence or absence of a
diaphragm, and the primary reaction equation for selective CH4 and
H2 production in the nonꢀdiaphragm electrochemical reduction
system. Generally, electrochemical reductions produce increased
numbers of electrons and protons as the applied voltage increases. A
system with or without a diaphragm would be expected to equally
mediate the same electrochemical reaction. However, the CO2
introduced in a diaphragmꢀcontaining electrochemical system is only
supplied to the cathode reaction area, isolated by the diaphragm,
where CO, CH3OH, HCOOH, HCOH, and H2 are produced during
the reduction reaction. On the other hand, there are no isolated
Figure 3. Faradaic efficiencies of the nonꢀdiaphragmꢀbased
electrochemical system. Comparison of Faradaic efficiencies at
various CO2 flow rates and applied voltages at 25°C. The left and
right columns show the Faradaic efficiencies when 0.2 M KOH and
NaOH electrolytes are used, respectively.
cathode and anode reaction areas in
a
nonꢀdiaphragm
electrochemical system. The nonꢀdiaphragm cell freely generates the
electrons and protons needed for the reduction of CO2 at low applied
voltage, and is the optimal system for selectively generating CH4 and
H2.
Figure 3 shows the effects of the type of electrolyte, CO2 flow, and
added voltage on CH4 and H2 generation in the nonꢀdiaphragm
system, expressed as Faradaic efficiency. Only CH4, H2, and nonꢀ
consumed reactants (CO2 and gaseous methanol) were generated in
the range of 0.1 to 1.0 V; this is attributed to the limited applied
voltage, which might be insufficient to transform CO2 to higher
hydrocarbons. 42, 43 As shown in Figure 3, the Faradaic efficiency
reached 96.8% (CH4, 35.6%; H2, 61.4%) at a 50 mL·min−1 CO2 flow
rate and 0.5 V in the nonꢀdiaphragmꢀbased electrochemical system
with 0.2 M KOH electrolyte. Similarly, the Faradaic efficiency was
96.1% (CH4, 64.3%; H2, 31.8%) under the same conditions with 0.2
M NaOH electrolyte. The Faradaic efficiency increased in the range
0.1–0.5 V and decreased in the range 0.6–1.0 V. This reduction
impaired the production of CH4 and H2 beyond 0.6 V at a 50
mL·min−1 CO2 flow rate. The Faradaic efficiency increased upon
increasing the CO2 flow rates to between 60 and 70 mL·min−1.
However, carbonate salts were formed when the flow rate was
increased above 80 mL·min−1 CO2 in the 0.2 M Na(K)OH
electrolyte, and the electrochemical reduction ceased. A higher
Faradaic efficiency for H2 production was obtained with KOH,
whereas a higher Faradaic efficiency for CH4 production resulted
with NaOH. The nonꢀdiaphragmꢀbased electrochemical system had
higher rates of production than the diaphragmꢀbased system. The
productionꢀrate trends are similar to those of Faradaic efficiency.
This journal is © The Royal Society of Chemistry 2014
RSC. Adv., 2014, 00, 1-3 | 3

RSC Advances
Page 4 of 6
View Article Online
COMMUNICATION
RSC Advances
DOI: 10.1039/C4RA14427A
CH4 can be controlled by using KOH and NaOH in the CO2
reduction reaction.
Experimental Section
Electrochemical reduction. The characteristics of the nonꢀ
diaphragmꢀbased electrochemical system for reducing CO2 are as
follows. The system, comprising acrylic materials, was 60 mm × 45
mm × 95 mm. CO2 (99.9999% pure) was introduced at rates of 50,
60, and 70 mL·min−1 through an inlet installed at the bottom of the
system using a mass flow controller (Sierra, C100L). The anode and
cathode consisted of insoluble Pt and insoluble Cu plates,
respectively, with dimensions of 40 mm × 40 mm × 1 mm; the two
electrodes were placed at the same height with a separation of 10
mm. A standard electrode (Ag/AgCl) was placed between these two
electrodes and the system was connected to an electrochemical
analyzer (PAR VersaSTAT3, AMETEK). Impedance (IMP) values
were measured and compared in the two electrochemical system
configurations. The experiments were conducted for 5 h using 0.2 M
NaOH or KOH in methanol (115 mL) as the electrolyte; methanol
was used instead of water because of the higher solubility of CO2 in
methanol.31
Figure 4. Production rates of CH4 and H2 in the nonꢀdiaphragmꢀ
based electrochemical system. The rates were measured at 25°C
under various CO2 flow rates and different applied voltages. The left
and right columns show the production rates using 0.2 M KOH and
NaOH electrolytes, respectively.
H2O analysis. The water content generated in the dissolution
reaction of 0.2 M NaOH or KOH in methanol (115 mL) was
measured using a Karl Fischer coulometer (Metrohm, Metrohm 737,
Switzerland).
Figure 4 shows that KOH in methanol affords electrochemical
reduction to H2 faster than NaOH in methanol, but the higher CD in
methanolic NaOH generates more CH4 than KOH in methanol. This
pattern is consistent with changes in the concentration of CH4 and H2
according to time (Figure S3). Additionally, methanol used as an
electrolyte was not electrochemically degraded due to its consistent
concentration during the experiment. Therefore, this demonstrates
that methanol is not produced as one of intermediates in our system,
which is inconsistent with Eq. (6) (Figure S4). Therefore, KOH is
responsible for the higher production of H2 and NaOH is responsible
for the higher production of CH4. Furthermore, the nonꢀdiaphragmꢀ
based electrochemical system produced not only H2 and CH4, but
also controlled their production rates using NaOH and KOH.
Taken together, the nonꢀdiaphragmꢀbased electrochemical system
reduced the voltage required to produce CH4 and H2 and enhanced
the Faradaic efficiency to >95%. Furthermore, it selectively
produced CH4 and H2 when NaOH or KOH electrolytes were
separately employed. In this system, oxidative gases such as CO
were not produced, thereby protecting the Cu anode from decay.
Accordingly, the absence of a diaphragm reduced the expected
problems, including limited control of the reduction and the
generation of undesirable intermediates, such as CO and
formaldehyde.
Comparison of the CDs. For this comparison, nonꢀdiaphragmꢀ and
diaphragm (SigmaꢀAldrich, Nafion membrane N117, 0.18 mm
thickness)ꢀbased electrochemical systems were used. The applied
voltage and generated current were measured using the
electrochemical analyzer in the range 0.1–1.0 V. The diaphragm was
installed in the same reactor. The atmospheric pressure was 1.2 atm.
CH4/H2 production under various conditions. An outlet and
sample collection site were installed in the upper part of the system;
the products in the collected samples were determined by gas
chromatography (GC) with flame ionization detection (FID, Agilent
HP6970) for CH4 and thermal conductivity detection (TCD,
PerkinElmer CALUS580) for H2. The intermediate products were
analyzed using a mass selective detector (MSD, Agilent HP6970).
After analysis of the products, the production rates and Faradaic
efficiencies were calculated.
Acknowledgements
This work was supported by a National Research Foundation of
Korea (NRF) grant funded by the Korean Government (NRFꢀ
2013R1A1A2008882) and the Research Fund, Kumoh National
Institute of Technology.
Conclusions
Removal of the diaphragm from the electrochemical reduction
system eliminates the electrical resistance it would otherwise
generate in the cell. The nonꢀdiaphragm system produces a higher
CD in contrast to the diaphragmꢀcontaining electrochemical system,
and it affords a high production rate, Faradaic efficiency, and
product selectivity. The proton sources in the nonꢀdiaphragm
electrochemical system are methanol and water; the latter is
produced by the dissolution reactions of the alkali bases. KOH and
NaOH contribute to the production of H2 and CH4, respectively.
These findings prove the possibility that the production of H2 and
Keywords: CO2 • Electrochemical Reduction • Selective • Nonꢀ
diaphragm • Low voltage
Notes and references
1
KwangꢀJin Yim, NamꢀGyu Kim, TaeꢀOh Kim
Department of Environmental Engineering
Kumoh National Institute of Technology
Daehakꢀro 61, Gumi, Gyeongbuk 730ꢀ701, Republic of Korea
4 | RSC. Adv., 2014, 00, 1-3
This journal is © The Royal Society of Chemistry 2014

Page 5 of 6
RSC Advances
RSC Advances
View Article Online
COMMUNICATION
DOI: 10.1039/C4RA14427A
Eꢀmail: tokim@kumoh.ac.kr,
15 B. B. Berkes, G. Inzelt, W. Schuhmann and A. S. Bondarenko, J.
Phys. Chem. C, 2012, 116, 10995–11003.
Tel: +82ꢀ54ꢀ478ꢀ7634, Fax: +82ꢀ54ꢀ478ꢀ7641
DongꢀKeun Song
2
16 J. Lin, Z. Ding, Y. Hou and X. Wang, Sci. Rep., 2013,
17 X. Cao, X. Huang, P. Liang, N. Boon, M. Fan, L. Zhang and X.
Zhang, Energy Environ. Sci.e, 2009, , 498–501.
3, 1056.
Department of EcoꢀMachinery Systems
Environmental and Energy Systems Research Division
Korea Institute of Machinery and Materials
156 Gajeongbukꢀro, Yuseong, Daejeon 305ꢀ343, Republic of Korea
ChanꢀSoo Kim
2
18 H. V. M. Hamelers, A. Ter Heijne, T. H. J. A. Sleutels, A. W.
Jeremiasse, D. P. B. T. B. Strik and C. J. N. Buisman, Appl.
Microbiol. Biotechnol., 2010, 85, 1673–1685.
3
4
5
Marine Energy Convergence & Integration Laboratory
Jeju Global Research Center
19 C. Schwandt and D. Fray, Electrochim. Acta, 2005, 51, 66–76.
20 F. Bidrawn, G. Kim, G. Corre, J. T. S. Irvine and J. M. Vohs
Solid-State Lett., 2008, 11, B167–B170.
Korea Institute of Energy Research, Republic of Korea
Kikuo Okuyama, Toru Iwaki, Takashi Ogi
Department of Chemical Engineering
Graduate School of Engineering, Hiroshima University
1ꢀ4ꢀ1 Kagamiyama, Higashi Hiroshima 739ꢀ8527, Japan
SungꢀEun Lee
21 D. Yuan, C. Yan, B. Lu, H. Wang, C. Zhong and Q. Cai,
Electrochim. Acta, 2009, 54, 2912–2915.
22 C. Costentin, S. Drouet, G. Passard, M. Robert and J. M. Savéant, J.
Am. Chem. Soc., 2013, 135, 9023–9031.
23 K. J. P. Schouten, Z. Qin, E. P. R. Gallent and M. T. Koper, M. J.
Am. Chem. Soc., 2012, 134, 9864–9867.
School of Applied Biosciences
Kyungpook National University
24 J. Wu, F. G. Risalvato, F. S. Ke, P. Pellechia and X. D. Zhou, J.
Electrochem. Soc., 2012, 159, F353–F359.
Daegu 702ꢀ701, Republic of Korea
Eꢀmail: selpest@knu.ac.kr,
25 A. A. Peterson and J. K. Nørskov, J. Phys. Chem. Lett., 2012, 3, 251–
Tel: +82ꢀ53ꢀ950ꢀ7768, Fax: +82ꢀ53ꢀ953ꢀ7233
258.
26 S. Kaneco, H. Katsumata, T. Suzuki and K. Ohta, Energy Fuels
2006, 20, 409–414.
,
†
These authors contributed equally to this work as first authors
*
These authors contributed equally to this work as corresponding
27 T. Mizuno, M. Kawamoto, S. Kaneco and K. Ohta, Electrochim.
Acta, 1997, 43, 899–907.
authors
28 S. Kaneco, K. Iiba, K. Ohta, T. Mizuno and A. Saji, Electrochim.
Acta, 1998, 44, 573–578.
References
1
D. T. Whipple and P. J. Kenis, J. Phys. Chem. Lett., 2010,
3458.
H. Li, P. H. Opgenorth, D. G. Wernick, S. Rogers, T.ꢀY. Wu, W.
1, 3451–
29 E. Barton Cole, P. S. Lakkaraju, D. M. Rampulla, A. J. Morris, E.
Abelev and A. B. Bocarsly, J. Am. Chem. Soc., 2010, 132, 11539–
11551.
2
Higashide, P. Malati, Y.ꢀX. Huo, K. M. Cho and J. C. Liao, Science
2012, 335, 1596–1596.
,
30 C, Finn, S. Schnittger, L. J. Yellowlees and J. B. Love, Chem.
Commun., 2012, 48, 1392–1399.
3
M. Gattrell, N. Gupta and A. Co, Energy Convers. Manage., 2007,
48, 1255–1265.
31 K. Nakata, T. Ozaki, C. Terashima, A. Fujishima and Y. Einaga,
Angew. Chem., 2014, 126, 890–893.
4
5
E. J. Maginn, J. Phys. Chem. Lett., 2010, 1, 3478–3479.
32 S. Gu, R. Cai, T. Luo, Z. Chen, M. Sun, Y. Liu, G. He and Y. Yan,
Angew. Chem. Int. Ed., 2009, 48, 6499ꢀ6502.
K. Xie, Y. Zhang, G. Meng and J. T. Irvine, J. Mater. Chem., 2011,
21, 195–198.
33 C. Oloman and H. Li, ChemSusChem, 2008,
34 S. Das and W. M. A. W. Daud, RSC Adv., 2014,
35 M. Fan, Z. Bai, Q. Zhang, C. Ma, X. Zhou and J. Qiao, RSC Adv.
2014, , 44583ꢀ44591.
1
, 385–391.
6
7
8
9
A. A. Peterson, F. AbildꢀPedersen, F. Studt, J. Rossmeisl and J. K.
4, 20856ꢀ20893.
Nørskov, Energy Environ. Sci., 2010, 3, 1311–1315.
,
,
T. Mogi, T. Ishii, K. Hashimoto and R. Nakamura, Chem. Commun.
,
4
2013, 49, 3967–3969.
36 I. Bors, J. Kaizer, G. Speier and M. Giorgi , RSC Adv., 2014,
4
Y. Chen, C. W. Li and M. W. Kanan, J. Am. Chem. Soc., 2012, 134
,
45969ꢀ45972.
19969–19972.
37 B. A. Rosen, A. SalehiꢀKhojin, M. R. Thorson, W. Zhu, D. T.
Whipple, P. J. A. Kenis and R. I. Masel, Science, 2011, 334, 643–
644.
C. W. Li and M. W. Kanan, J. Am. Chem. Soc., 2012, 134, 7231–
7234.
10 M. Rakowski Dubois and D. L. Dubois, Acc. Chem. Res., 2009, 42
,
38 S. A. Yao, R. E. Ruther, L. Zhang, R. A. Franking, R. J. Hamers and
J. F. Berry, J. Am. Chem. Soc., 2012, 134, 15632–15635.
39 F. Ma and M. A. Hanna, Bioresour. Technol., 1999, 70, 1–15.
1974–1982.
11 E. E. Benson, C. P. Kubiak, A. J. Sathrum and J. M. Smieja, Chem.
Soc. Rev., 2009, 38, 89–99.
40 L. Bai, Y. Zhao, Y. Hu, B. Zhong and S. Peng, J. Nat. Gas. Chem.
,
12 M. Lea, M. Ren, Z. Zhang, P. T. Sprunger, R. L. Kurtz and J. C.
Flake, J. Electrochem. Soc., 2011, 158, E45–E49.
1996, , 229–236..
5
41 J. Schneider, H. Jia, J. T. Muckerman and E. Fujita Chem. Soc. Rev.
,
13 K. P. Kuhl, E. R. Cave, D. N Abram and T. F. Jaramillo, Energy
2012, 41, 2036–2051.
Environ. Sci., 2012,
14 K. Schouten, Y. Kwon, C. Van der Ham, Z. Qin and M. Koper,
Chem. Sci., 2011, , 1902–1909.
5, 7050–7059.
42 R. Aydın, H. Ö. Doğan and F. Köleli, Appl. Catal. B, 2013, 140, 478–
482.
2
43 K. Leung, I. M. Nielsen, N. Sai, C. Medforth and J. A. Shelnutt, J.
Phys. Chem. A, 2010, 114, 10174–10184.
This journal is © The Royal Society of Chemistry 2014
RSC. Adv., 2014, 00, 1-3 | 5

RSC Advances
Page 6 of 6
View Article Online
COMMUNICATION
RSC Advances
DOI: 10.1039/C4RA14427A
Entry for the Table of Contents
Communication
One sentence highlight
Electrochemical CO2 reduction in a diaphragm-less cell
selectively afforded CH4 and H2 in methanolic NaOH and KOH
electrolytes, respectively.
6 | RSC. Adv., 2014, 00, 1-3
This journal is © The Royal Society of Chemistry 2014