Molten carbonate fuel cells conductivity

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. 

Molten carbonate fuel cell (MCFC) working at about 650°C with a mixture of molten carbonates (Li2C03/K2C03) as electrolyte, conducting by the C03= anion, both of them being high-temperature fuel cells. 

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. 

The most important fuel cells that are in use nowadays are the polymer electrolyte membrane fuel ceU (PEMFC), the molten carbonate fuel cell (MCFC), and the solid oxide fuel cell (SOFC). In a PEMFC, the electrolyte is a polymer membrane that conducts protons, in an MCFC the electrolyte is a carbonate melt in which oxygen is conducted in the form of carbonate ions, CO , and in an SOFC the electrolyte is a solid oxide that conducts oxygen ions, While a PEMFC can be operated at low temperatures of about 80 °C, an MCFC works at intermediate temperatures of about 650 °C, and an SOFC needs relatively high temperatures of 800-1000 °C (see next sections). 

Lagergren, C. Lindbergh, G. Experimental determination of effective conductivities in porous molten carbonate fuel cell electrodes. Electrochim. Acta 1998, 44 (2-3), 503-511. 

Molten carbonate fuel cell (MCFC) uses an electrolyte composed of a molten mixture of carbonate salts, e.g., lithium carbonate, potassium carbonate, and sodium carbonate, usually retained in a ceramic matrix, e.g., LiA102. When heated to a temperature of around 650° C, these salts melt and become conductive to carbonate ions (C03 ). Natural gas can be used directly... 

Current research is centred on making compact cells of high efficiency. They are described in terms of the electrolyte that is used. The principle types are alkali fuel cells, described above, with aqueous KOH as electrolyte, MCFCs (molten carbonate fuel cells), with a molten alkali metal or alkaline earth carbonate electrolyte, PAFCs (phosphoric acid fuel cells), PEMs (proton exchange membranes), using a solid polymer electrolyte that conducts ions, and SOFCs, (solid oxide fuel cells), with solid electrolytes that allow oxide ion, 0 , transport The... 

A third type of electrolyte, used for molten carbonate fuel cells at high temperatures, conducts carbide ions (COj -) and is associated with the electrode reactions in Table 1-5. 

Molten carbonate fuel cell (MCFC) L1/KC03 as molten salt, that conducts CO ions 650 °C Industrial applicatimis, power statimis, ships... 

There are several types of fuel cells, which are classified primarily by the kind of electrolyte they employ. The materials used for electrolytes have their best conductance only within certain temperature ranges (Hirschenhofer 1994). A few of the most promising types include phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), solid oxide fuel cell (SOFC), alkaline fuel cell (AFC), proton exchange membrane fuel cell (PEMFC), and direct methanol fuel cell (DMFC). 

Glugla P G and Decarlo V J (1982), The specific conductance of molten carbonate fuel cell tiles , J Electrochem Soc, 129,1745-1747. 

The two types of high temperature fuel cell are quite different from each other (Table 6). The molten carbonate fuel cell, which operates at 650°C, has a metal anode (nickel), a conducting oxide cathode (e.g. lithiated NiO) and a mixed Li2C03/K2C03 fused salt electrolyte. Sulphur attack of the anode, to form liquid nickel sulphide, is a severe problem and it is necessary to remove H2S from the fuel gas to <1 ppm or better. However, CO is not a poison. Other materials science problems include anode sintering and degradation, corrosion of cell components and evaporation of the electrolyte. Work continues on this fuel cell in U.S.A. and there is some optimism that the problem will be solved within 10 years. 

The section on intermediate temperature fuel cells has just one entry on each fuel cell type. With decreasing operation temperature, the Molten Carbonate Fuel Cell technology is critically discussed (Molten Carbonate Fuel Cells) before two related systems relying on the unique protrui conducting properties of phosphoric acid are described. While the well-established phosphoric acid fuel cell (PAFC) is developed for stationary applications (Phosphoric Acid Fuel Cells for Stationary Applications), polybenzimidazole (used as a matrix for phosphoric acid) fuel cells even have some potential for mobile and small applications (Polybenzimidazole Fuel Cell Technology). 

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 cm 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 reactirm 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. 

Baumgartner C (1984) Electronic conductivity decrease in porous NiO cathodes during operation in molten carbonate fuel cell. J Electrochem Soc 131 2607-2610... 

Many different types of fuel-cell membranes are currently in use in, e.g., solid-oxide fuel cells (SOFCs), molten-carbonate fuel cells (MCFCs), alkaline fuel eells (AFCs), phosphoric-acid fuel cells (PAFCs), and polymer-electrolyte membrane fuel cells (PEMFCs). One of the most widely used polymers in PEMFCs is Nalion, which is basically a fluorinated teflon-like hydrophobic polymer backbone with sulfonated hydrophilic side chains." Nafion and related sulfonic-add based polymers have the disadvantage that the polymer-conductivity is based on the presence of water and, thus, the operating temperature is limited to a temperature range of 80-100 °C. This constraint makes the water (and temperature) management of the fuel cell critical for its performance. Many computational studies and reviews have recently been pubhshed," and new types of polymers are proposed at any time, e.g. sulfonated aromatic polyarylenes," to meet these drawbacks. 

Molten carbonate fuel cells (MCFC) have the electrolyte composed of a combination of alkali (Li, Na, K) carbonates. Operating temperatures are between 600 and 700°C where the carbonates form a highly conductive molten salt, with carbonate ions providing ionic conduction. These fuel cells are in the precommercial / demonstration stage for stationary power generation [1]. 

Since the type of electrolyte material dictates operating principles and characteristics of a fuel cell, a fuel cell is generally named after the type of electrolyte used. For example, an alkaline fuel cell (AFC) uses an alkaline solution such as potassium hydroxide (KOH) in water, an acid fuel cell such as phosphoric acid fuel cell (PAFC) uses phosphoric acid as electrolyte, a solid polymer electrolyte membrane fuel cell (PEMFC) or proton exchange membrane fuel cell uses proton-conducting solid polymer electrolyte membrane, a molten carbonate fuel cell (MCFC) uses molten lithium or potassium carbonate as electrolyte, and a solid oxide ion-conducting fuel cell (SOFC) uses ceramic electrolyte membrane. 

The molten carbonate fuel cell (MCFC) operates at high temperature, which is about 600-700 °C. It consists of two porous conductive electrodes in contact with an electrolyte of molten carbonate. This type of cell allows the internal reform. The main advantage of the MCFC is its high efficiency (50-60%) without external reformer and metal catalyst, due to the high operating temperature (Farooque Maru, 2001). This cell is intolerant to sulfur and its launching is slow, these are its main disadvantages. 

Solid oxide fuel cells make use of the high-temperature oxides as electrolyte. Figure 2.1 compares the conductivities of common electrolytes that are utilized in various fuel cells namely, phosphoric acid fuel cells (PAFC), polymer electrolyte fuel cells (PEFC), molten carbonate fuel cells (MCFC), and solid... 

---