Abstract
Two parts are treated: one is the physical and chemical features of materials of molten carbonate fuel cells (MCFCs), and the other is performance analysis with a 100 cm2 class single cell. The characteristics of the fuel cell are determined by the electrolyte. The chemical and physical properties of the electrolyte with respect to gas solubility, ionic conductivity, dissolution of cathode material, corrosion, and electrolyte loss in the real cell are introduced. The reaction characteristics of hydrogen oxidation in molten carbonates and materials for the anode of the MCFC are reviewed. The kinetics of the oxygen reduction reaction in the molten carbonates and state of the art of cathode materials are also described. Based on the reaction kinetics of electrodes, a performance analysis of MCFCs is introduced. The performance analysis has importance with respect to the increase in performance through material development and the extension of cell life by cell development. Conventional as well as relatively new analysis methods are introduced.
This chapter was originally published as part of the Encyclopedia of Sustainability Science and Technology edited by Robert A. Meyers. DOI:10.1007/978-1-4419-0851-3
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Abbreviations
- Activation overpotential:
-
Voltage loss due to low charge-transfer rate on the electrode surface.
- Anode:
-
A porous electrode where hydrogen is oxidized with carbonate ions (CO 2−3 ) to steam and carbon dioxide.
- Basicity:
-
Log(k d) of molten carbonates where k d is the equilibrium constant of the reaction \( {\text{CO}}_3^{2 - }{ }\mathop { \rightleftharpoons }\limits^{{k_d}} { }{{\text{O}}^{2 - }} + {\text{ C}}{{\text{O}}_2} \) similar to the pH of aqueous solutions.
- Cathode:
-
A porous electrode where oxygen is reduced with carbon dioxide to carbonate ions (CO 2−3 ).
- Electrolyte:
-
Molten carbonates providing ionic paths for the electrode reactions with combinations of Li2CO3, Na2CO3, and K2CO3.
- Exchange current density (io):
-
An actual current density of an electrode at net zero current indicating catalytic activity of the electrode.
- Fuel cell:
-
A system of continuous electrochemical energy conversion from chemical energy to electricity mostly by oxidation of hydrogen and reduction of oxygen.
- Internal resistance:
-
Electrical resistance of cell components.
- Mass transfer:
-
Access of reactants to the electrode surface and departure of products mainly by diffusion and convection.
- Matrix:
-
Ceramic porous material holding molten carbonates by capillary forces.
- Ohmic loss (ηIR):
-
Voltage loss due to electrical resistance of cell components.
- Open circuit voltage (EOCV):
-
A cell voltage at net zero current determined by the relation of \( {E_{\text{OCV}}} = {E^{\text{o}}} + \displaystyle\frac{{RT}}{{2F}}\ln \left( {\frac{{p\left( {{{\text{H}}_2}} \right)p{{\left( {{{\text{O}}_2}} \right)}^{0.5}}p{{\left( {{\text{C}}{{\text{O}}_2}} \right)}_{\text{ca}}}}}{{p\left( {{{\text{H}}_2}{\text{O}}} \right)p{{\left( {{\text{C}}{{\text{O}}_2}} \right)}_{\text{an}}}}}} \right).\)
- Overpotential (η):
-
Voltage reduction from an open circuit voltage due to resistance of electrochemical reactions at an electrode.
- Polarization:
-
A state of deviation from open circuit voltage due to current flowing in the cell.
- Reaction kinetics:
-
Charge-transfer rates of electrochemical reactions on electrode surfaces.
- Three-phase boundary:
-
A site of electrode-carbonate electrolyte-gaseous reactants where electrochemical reactions take place.
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Lee, CG. (2013). Molten Carbonate Fuel Cells. In: Kreuer, KD. (eds) Fuel Cells. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-5785-5_8
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