Influence of Electrolyte Composition on Electrode Kinetics in the Molten Carbonate Fuel Cell

Ang, P. G. P.; Sammells, Anthony F.

doi:10.1149/1.2129873

Cited by 72 publications

(50 citation statements)

References 6 publications

(10 reference statements)

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“…8,15 The exchange current density (i 0 ), for a standard gas at 650°C in the present study is 70 A/m 2 , which is lower than other values given in the literature. 1,7,12,16 Here, n was set to 2, because this is the value obtained assuming the most likely reaction mechanisms occur. 14 Changing n will change the value of i 0 , although the partial pressure dependencies will still be the same.…”

Section: Kinetics Of the Hydrogen Reaction-mentioning

confidence: 99%

Experimental Investigation of the Porous Nickel Anode in the Molten Carbonate Fuel Cell

Lindbergh

Olivry

Sparr

2001

J. Electrochem. Soc.

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The electrochemical performance of the porous nickel anode in a molten carbonate fuel cell was experimentally investigated in this study. The electrode structure was studied by scanning electron microscope and Hg porosimetry. The effect of electrolyte filling, on overpotential at a constant current density, was also examined. Kinetics for the hydrogen reaction was studied by obtaining stationary polarization curves, for porous nickel anodes at varying temperatures and anode gas compositions. The slopes of these polarization curves were analyzed at low overpotentials, with the assumption that the porous anode was under kinetic control, and the corresponding exchange current densities were determined using a simplified porous electrode model. The obtained partial pressure dependencies of the exchange current density were high, and therefore, difficult to explain by the generally assumed mechanisms.The molten carbonate fuel cell ͑MCFC͒ operates at high temperatures ͑600-700°C͒, which gives it the potential to reach high overall efficiency in an integrated system. It is in general operated using natural gas as its fuel, although high concentrations of carbon monoxide and carbon dioxide can also be a part of the feed. This makes it very suitable for use with biogas, gasified coal, or gasified biomass feeds although the two latter fuels will result in much lower concentrations of hydrogen gas. Operation with a lower concentration of hydrogen increases the losses at the anode, providing a reason for investigating and optimizing the performance of the anode under such conditions. The overvoltage losses at the anode are considered to be relatively small, which is partly due to the relatively low current densities that present MCFC systems operate at. A significant increase in current density, which is desirable in order to improve the power density, would result in the increase of losses at the anode.A general procedure for elucidating the mechanism of the anode reaction is to determine the partial pressure dependency for the components, hydrogen, carbon dioxide, and water, that partake in the overall electrochemical reactionSeveral studies have previously been made to find out the reaction mechanism at the anode, 1-18 Table I. Most experiments were conducted on flag electrodes, which are quite different from porous electrodes, when regarding the electrode surface and mass transfer conditions. Despite this research, the reaction mechanism is still not well defined. One problem when evaluating the partial pressure dependency is the actual gas composition inside the cell, since different reactions can take place at the anode. One such reaction is the electrochemical reaction of carbon monoxideAnother possible reaction is the shift reaction, which is sum of Reactions 1 and 2According to Borucka and Appleby, 19 the reaction rate for direct carbon monoxide oxidation is extremely slow at a surface of 99.99% pure gold. They claimed that the most likely way for carbon monoxide to be utilized is through the shift reaction as that ...

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Section: Kinetics Of the Hydrogen Reaction-mentioning

confidence: 99%

Experimental Investigation of the Porous Nickel Anode in the Molten Carbonate Fuel Cell

Lindbergh

Olivry

Sparr

2001

J. Electrochem. Soc.

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“…By using the Arrhenius equation [26], the values of 4. For hydrogen production at the Ni electrode in the MCEC, the activation energy is calculated to be 69 kJ·mol -1 for the reference case, using the Arrhenius equation [27]. For the gases with low hydrogen concentration, higher values, 85, 112, 99 and 138 kJ·mol -1 are obtained for gases 2, 3, 4 and 5, respectively.…”

Section: Resultsmentioning

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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“…용융탄산염형 연료전지(MCFC)는 전해질로서 약 650 o C 고온의 용융탄산염을 사용하므로, 수소 산화반응의 교환 전류밀도가 약 100 mA/cm 2 정도이고, 1,2) 산소환원반응의 경우는 약 30 mA/cm 2 정도로서 3,4) 수용액 전해질의 산소환원반응속도에 비해 약 10 7 배 정도 빠르다고 할 수 있다. 5…”

Section: 서 론unclassified

Effect of Anode Thickness on the Overpotential in a Molten Carbonate Fuel Cell

Lee¹,

Lee²,

Ryu³

et al. 2010

Journal of the Korean Electrochemical Society

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: This work investigated the effect of anode thickness on the anodic overpotential with 100 cm 2 class MCFC single cells. The hydrogen oxidation rate in the molten carbonate is sufficiently high, which may lead to weak relation of overpotential with anode geometrical area. The relation of anode surface area and overpotential was analysed in terms of anode thickness in this work. Steady state polarization, inert gas step addition (ISA), and reactant gas addition (RA) methods were employed to the two cells with 0.77 mm and 0.36 mm thickness of anode. The result represented that the anodic overpotential at the cells were identical. It implied that the anodic overpotential was independent on the electrode thickness within the tested range.

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Influence of Electrolyte Composition on Electrode Kinetics in the Molten Carbonate Fuel Cell

Cited by 72 publications

References 6 publications

Experimental Investigation of the Porous Nickel Anode in the Molten Carbonate Fuel Cell

Experimental Investigation of the Porous Nickel Anode in the Molten Carbonate Fuel Cell

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

Effect of Anode Thickness on the Overpotential in a Molten Carbonate Fuel Cell

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