Molten carbonate fuel cells cathodes

Fontes, E. Fontes, M. Lindbergh, G. Simonsson, D. Influence of gas phase mass transfer limitations on molten carbonate fuel cell cathodes. J. Appl. Electrochem. 1997,27(10), 1149-1156. 

Kunz, H.R., Bregoli, L.J., and Szymanski, S.T. (1984) A homoge-neous/agglomerate model for molten carbonate fuel cell cathodes. J. Electrochem. Soc., 131 (12), 2815-2821. 

Mitsushima S, Kuroe S, Matsuda S, Kamo T (1998) Polarization model for molten carbonate fuel cell cathodes. Denldkagaku Electrochemistry 66 817... 

Fang B, Chen H (2001) A new candidate material for molten carbonate fuel cell cathodes. J Electroantil Chem 501 128-131... 

Bregoli L.J. and Kunz H.R. (1982) The effect of thickness on the performance of molten carbonate fuel cell cathodes , Journal of the Electrochemical Society, 129(12), 2711-2715. 

Schoeler, A.C., Kaun, T.D., Bloom, I., Lanagan, M., Kmmpelt, M. (20(X)) Corrosion behavior and interfacial resistivity of bipolar plate materials under molten carbonate fuel cell cathode conditions. Journal of the Electrochemical Society, 147, 916 921. 

Molten Carbonate Fuel Cell. The electrolyte ia the MCFC is usually a combiaation of alkah (Li, Na, K) carbonates retaiaed ia a ceramic matrix of LiA102 particles. The fuel cell operates at 600 to 700°C where the alkah carbonates form a highly conductive molten salt and carbonate ions provide ionic conduction. At the operating temperatures ia MCFCs, Ni-based materials containing chromium (anode) and nickel oxide (cathode) can function as electrode materials, and noble metals are not required. 

Just as the aqueous, alkaline fuel cell can be adopted to C02 separation and concentration, the molten carbonate fuel cell (MCFC) can function in this application as well. Recall that the MCFC cathode operates with the net reaction... 

Molten Carbonate Fuel Cell The electrolyte in the MCFC is a mixture of lithium/potassium or lithium/sodium carbonates, retained in a ceramic matrix of lithium aluminate. The carbonate salts melt at about 773 K (932°F), allowing the cell to be operated in the 873 to 973 K (1112 to 1292°F) range. Platinum is no longer needed as an electrocatalyst because the reactions are fast at these temperatures. The anode in MCFCs is porous nickel metal with a few percent of chromium or aluminum to improve the mechanical properties. The cathode material is hthium-doped nickel oxide. 

Molten carbonate fuel cells (MCFCs) are currently being developed for natural gas and coal-based power plants for electrical utility, industrial, and military applications. MCFCs are high-temperature fuel cells that use an electrolyte composed of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic lithium aluminium oxide (LiAI02) matrix. Since they operate at extremely high temperatures of 650°C and above, non-precious metals can be used as catalysts at the anode and cathode, reducing costs. 

As a first example of the use of reaction mechanism graphs, consider the electrochemistry of molten carbonate fuel cell (MCFC) cathodes. These cathodes are typically nickel-oxide porous electrodes with pores partially filled with a molten carbonate electrolyte. Oxygen and carbon dioxide are fed into the cathode through the vacant portions of the pores. The overall cathodic reaction is 02 + 2C02 + 4e / 2C03=. This overall reaction can be achieved through a number of reaction mechanisms two such mechanisms are the peroxide mechanism and the superoxide-peroxide mechanism, and these are considered next. 

The molten carbonate fuel cells employ LijCOj-f CC (62.38 mol.%) electrolytes, porous Ni alloy, and lithiated nickel oxide as anodes and cathodes at an operating temperature of 723 K. The half-cell reactions of each side are, respectively... 

The electrolyte in this fuel cell is generally a combination of alkali carbonates, which are retained in a ceramic matrix of LiA102 [8], This fuel cell type works at 600°C-700°C, where the alkali carbonates form a highly conductive molten salt with carbonate ions providing ionic conduction. At the high operating temperatures in the molten carbonate fuel cell, a metallic nickel anode and a nickel oxide cathode are adequate to promote the reaction [9], Noble metals are not required. 

Molten carbonate fuel cells (MCFC), with alkali carbonate (in LiA102 matrixes) electrolyte, conduct C032 -anions, generated at an 02/C02 exposed cathode to electro-oxidise H2 at the anode and at high temperatures. 

Using a cell that was designed along the lines of a molten carbonate fuel cell (Fig. 22), the removal rates of SOj varied from 78 7o at 600 ppm of SO at the cathode to 24% at 2100 ppm of at the cathode. The same authors [103] also reported an improvement over their earlier study by using a ternary eutectic of lithium, potassium, and sodium sulfates as the electrolyte together with Li20-9Cr03 electrodes, which were found to be stable in the molten electrolyte. 

Lim and Winnick [110] examined removal of H2S from a simulated hot coal-gas stream fed to the cathode while elemental sulfur gas was evolved at the anode. This process was performed in a cell that was similar in construction to a molten carbonate fuel cell (Fig. 23). The electrolyte was a mixture of Na2S and Li2S retained in a porous inert matrix material (MgO). The cathodic reaction involved the two-electron reduction of hydrogen sulfide to hydrogen (information on the equilibrium potential for H2S reduction can be obtained from [111] ... 

Freni, S., Barone, F., Puglisi, M. (1998). The dissolution process of the NiO cathodes for molten carbonate fuel cells state-of-the-art. Int. J. Energy Res. 22,17-31. 

Pierce, R.D. Smith, J.L. Poeppel, R.B. A review of cathode development for molten carbonate fuel cells. In Molten Carbonate Fuel Cell Technology, Proceedings Electrochemical Society, 1984 Vol. 84-13, 147-174. 

Legergren, C. Lundblad, A. Bergman, B. Synthesis and performance of LiCo02 cathodes for the molten carbonate fuel cell (MCFC). J. Electrochem. Soc. 1994, 141 (11), 2959-2966. 

Giorgi, L. Carewska, M. Scaccia, S. Simonetti, E. Giacometti, E. Tulli, R. Development of molten carbonate fuel cell using novel cathode material. Int. J. Hydrogen Energy 1996, 21 (6), 491-496. 

Gourba, E. Cassir, M. Tessier, C. Chemical and electrochemical behaviour of Ni-Ti in the cathodic conditions used in molten carbonate fuel cells. J. Electroanal. Chem. 2001,505 (1-2), 69-77. 

Ganesan, P. Colon, H. Haran, B. Popov, N.B. Performance of Lao.8Sro.2Co03 coated NiO as cathodes for molten carbonate fuel cells. J. Power Sources 2003, 115 (1), 12-18. 

Janowitz, K. Kah, M. Wendt, H. Molten carbonate fuel cell research part I. Comparing cathodic oxygen reduction in lithium/potassium and lithium/sodium carbonate melts. Electrochim. Acta 1999, 45 (7), 1025-1037. 

Lithium aluminates are also important in the development of molten carbonate fuel cells (MCFC) [82, 83], In these fuel cells, a molten carbonate salt mixture is used as an electrolyte. These fuel cells operate through an anode reaction, which is a reaction between carbonate ions and hydrogen. A cathode reaction combines oxygen, C02, and electrons from the cathode to produce carbonate ions, which enter the electrolyte. These cells operate at temperatures of 650°C and the electrolyte, which is usually lithium and potassium carbonate, is suspended in an inert matrix, which is usually a lithium aluminate. 

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