Conversion of CO[sub 2] to CO by Electrolysis of Molten Lithium Carbonate

Kaplan, Valery; Wachtel, Ellen; Gartsman, K.; Feldman, Yishay; Lubomirsky, Igor

doi:10.1149/1.3308596

Cited by 135 publications

(142 citation statements)

References 21 publications

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“…• C. Kaplan et al [3][4] observed the conversion of CO 2 to CO by using a cell with a molten electrolyte consisting of lithium carbonate and lithium oxide, in which the electrodes were graphite (anode) and titanium (cathode), and the working temperature was 850-900…”

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confidence: 99%

Electrode Kinetics of the Ni Porous Electrode for Hydrogen Production in a Molten Carbonate Electrolysis Cell (MCEC)

Hu¹,

Lindbergh²,

Lagergren³

2015

J. Electrochem. Soc.

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The purpose of this study was to elucidate the kinetics of a porous nickel electrode for hydrogen production in a molten carbonate electrolysis cell. Stationary polarization data for the Ni electrode were recorded under varying gas compositions and temperatures. The slopes of these iR-corrected polarization curves were analyzed at low overpotential, under the assumption that the porous electrode was under kinetic control with mass-transfer limitations thus neglected. The exchange current densities were calculated numerically by using a simplified porous electrode model. Within the temperature range of 600-650 • C, the reaction order of hydrogen is not constant; the value was found to be 0.49-0.44 at lower H 2 concentration, while increasing to 0.79-0.94 when containing 25-50% H 2 . The dependence on CO 2 partial pressure increased from 0.62 to 0.86 with temperature. The reaction order of water showed two cases as did hydrogen. For lower H 2 O content (10-30%), the value was in the range of 0.47-0.67 at 600-650 • C, while increasing to 0.83-1.07 with 30-50% H 2 O. The experimentally obtained partial pressure dependencies were high, and therefore not in agreement with any of the mechanisms suggested for hydrogen production in molten carbonate salts in this study. Electrolysis in molten carbonate salts at high temperatures is a promising method for hydrogen and/or syngas (H 2 +CO) production, especially when combining it with renewable electricity resources such as solar energy and wind power. Due to the favorable thermodynamic and kinetic conditions, high-temperature electrolysis will attain higher overall efficiency and require lower applied voltage when compared to low-temperature electrolysis.1 Electrolysis in molten carbonates has been evidenced by some authors, mainly by converting CO 2 into CO.2-5 Peelen et al. 2 studied the electrochemical reduction of CO 2 into CO on a gold flag electrode in 62/38 mol% Li/K carbonate mixture in the temperature range 575-700• C. Kaplan et al.3-4 observed the conversion of CO 2 to CO by using a cell with a molten electrolyte consisting of lithium carbonate and lithium oxide, in which the electrodes were graphite (anode) and titanium (cathode), and the working temperature was 850-900• C. Chery et al. 5 presented thermodynamic calculations and experimental measurements on the reduction of CO 2 into CO on a gold flag or planar disk electrode with Li/K and Li/Na carbonate eutectics at temperatures from 575 to 650• C. However, most experiments were carried out on flag electrodes, which are different from porous electrodes when considering electrode surface and mass-transfer limitations. In our previous study 6 a cell operating at 650• C, with conventional molten carbonate fuel cell (MCFC) materials (Ni-based porous electrode and molten carbonate electrolyte), was investigated also for electrolysis. The cell was found to give lower polarization losses in MCEC mode than in MCFC mode, mainly due to the NiO electrode performing much better as anode in the electrolysis cell. Reversing...

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mentioning

confidence: 99%

Electrode Kinetics of the Ni Porous Electrode for Hydrogen Production in a Molten Carbonate Electrolysis Cell (MCEC)

Hu¹,

Lindbergh²,

Lagergren³

2015

J. Electrochem. Soc.

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“…The possibility of electrolysis in molten carbonate salts has been evidenced [15][16][17][18][19], but was initially investigated for carbon dioxide capture by converting CO2 into CO and/or C. Peelen et al [15] studied the electrochemical reduction of CO2 into CO on a gold flag electrode in Li/K carbonate eutectics at temperatures from 575 to 700 °C. Kaplan et al [16,17] studied the conversion of CO2 to CO in a cell operated at 850-900 °C.…”

Section: Introductionmentioning

confidence: 99%

Operating the nickel electrode with hydrogen-lean gases in the molten carbonate electrolysis cell (MCEC)

Lindbergh

Lagergren

2016

International Journal of Hydrogen Energy

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If a molten carbonate electrolysis cell (MCEC) is applied for fuel gas production it is important to know the polarization of the nickel electrode when operated at low concentration of hydrogen. Thus, the electrochemical performance of the Ni electrode was investigated under hydrogen-lean gases containing 1/24.5/24.5/50%, 1/49.5/24.5/25%, 1/24.5/49.5/25% and 1/49.5/49.5/0% H2/CO2/H2O/N2 in the temperature range of 600-650 °C and was then compared to the reference case with 25/25/25/25% H2/CO2/H2O/N2. The electrochemical measurements included polarization curve coupled with current interrupt, and electrochemical impedance spectroscopy. Polarization resistances of the Ni electrode obtained by the two different techniques agreed well. For the inlet gases containing low amounts of hydrogen the Ni electrode exhibited higher polarization losses than when using the reference case in the electrolysis cell. The electrochemical impedance measurements showed that both charge-transfer and mass-transfer polarizations were higher for hydrogen-lean gases at all measured temperatures.Except under the condition with 1/49.5/49.5% H2/CO2/H2O at 650 °C, the Ni electrode exhibited lower mass-transfer polarization when compared to the reference case. Furthermore, the mass-transfer polarization was strongly dependent on temperature under H2-lean gases, differing from the reference case when the temperature has almost no effect on mass-transfer polarization. The activation energy for hydrogen production was calculated to be in the range of 69-138 kJ·mol -1 under all measured gases, indicating that the Ni electrode is under kinetic and/or mixed control in the MCEC.

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“…9,10 Some researchers have investigated the conversion of CO 2 into carbon or carbon monoxide by electrolysis in a molten salt. 8,[10][11][12][13] Carbon deposition has typically been achieved through the formation of carbon powders or carbon film.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Behavior of Carbonate Ion in the LiF^|^ndash;NaF^|^ndash;Li2CO3 System

Shi

Gao

et al. 2014

Electrochemistry

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The electrochemical behavior of carbonate ion at a Ni electrode in LiF-NaF-Li 2 CO 3 molten salt was investigated using cyclic voltammetry, square wave voltammetry, and chronopotentiometry. The results show that the electrochemical reduction of carbonate ion to carbon is a simple four-electron transfer that occurs in a one-step process. The reduction of carbonate ion at a Ni-wire working electrode is an irreversible process with diffusioncontrolled mass transfer. The diffusion coefficient of carbonate ion at 973, 993, 1023, 1043, and 1063 K is 4.46 × 10 . The X-ray diffraction results show that hexagonally structured graphitized carbon can be obtained by potentiostatic electrolysis. Scanning electron microscopy images show that the deposits exhibit a spherical morphology.

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Conversion of CO[sub 2] to CO by Electrolysis of Molten Lithium Carbonate

Cited by 135 publications

References 21 publications

Electrode Kinetics of the Ni Porous Electrode for Hydrogen Production in a Molten Carbonate Electrolysis Cell (MCEC)

Electrode Kinetics of the Ni Porous Electrode for Hydrogen Production in a Molten Carbonate Electrolysis Cell (MCEC)

Operating the nickel electrode with hydrogen-lean gases in the molten carbonate electrolysis cell (MCEC)

Electrochemical Behavior of Carbonate Ion in the LiF^|^ndash;NaF^|^ndash;Li2CO3 System

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