Molten carbonate fuel cells ionic 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. 

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. 

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. 

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]. 

In a later work, both the CuCl/KCl molten salt Wacker oxidation system and a [Bu4N][SnCl3] system (melting point 60 °C) was applied to the electrocatalytic generation of acetaldehyde from ethanol by co-generation of electricity in a fuel cell [56]. In the cell set-up, porous carbon electrodes supported with an ionic liquid catalyst electrolyte were separated by a proton conducting membrane (Fig. 5.6-4), and current efficiency and product selectivity up to 87% and 83%, respectively, were reported at 90 °C. 

Depending on the materials used for the separation membrane, the ionic conductivity is different as is the temperature at which the desirable ionic conductivity is obtained. Fuel cells can be classified as alkaline, phosphate, molten carbonate, solid oxides, and polymer electrolyte types. These all exhibit different characteristics, and research and development have been focusing on these differences. Readers interested in these aspects of fuel cells are referred to the works by Fueki and Takahashi [1], and Takahashi [2]. Discharge characteristics of various fuel cells are shown in Fig. 2. [3]... 

Molten KOH or NaOH is used as the electrolyte, which is contained within a metallic container. The metallic container acts as the cathode and a carbon rod dipped into electrolyte acts as both fuel and anode of the cell. Molten hydroxide electrolytes possess advantageous features such as high ionic conductivity, low overpotential and high carbon oxidation rate with a low operation temperature of 600°C for DCFC, which make its components fabrication economical. The dominant reaction product would be CO2 instead of CO. The ceU reactions are given as follows ... 

The DCFC with molten carbonate electrolytes are the most commercial type of fuel cells. Molten carbonate as an electrolyte has a number of advantages such as high ionic conductivity long-term stability of CO2 and catalysis of carbon oxidation. These DCFCs work at high operating temperatures of 600-850°C. Usually, mixed molten... 

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