Solid-oxide fuel cells reactions between

A solid oxide fuel cell (SOFC) consists of two electrodes anode and cathode, with a ceramic electrolyte between that transfers oxygen ions. A SOFC typically operates at a temperature between 700 and 1000 °C. at which temperature the ceramic electrolyte begins to exhibit sufficient ionic conductivity. This high operating temperature also accelerates electrochemical reactions therefore, a SOFC does not require precious metal catalysts to promote the reactions. More abundant materials such as nickel have sufficient catalytic activity to be used as SOFC electrodes. In addition, the SOFC is more fuel-flexible than other types of fuel cells, and reforming of hydrocarbon fuels can be performed inside the cell. This allows use of conventional hydrocarbon fuels in a SOFC without an external reformer. 

Fig. 1.6 Illustration of a planar-stack, solid-oxide fuel cell (SOFC), where an membrane-electrode assembly (MEA) is sandwiched between an interconnect structure that forms fuel and air channels. There is homogeneous chemical reaction within the flow channels, as well as heterogeneous cehmistry at the channel walls. There are also electrochemical reactions at the electrode interfaces of the channels. A counter-flow situation is illustrated here, but co-flow and cross-flow configurations are also common. Channel cross section dimensions are typically on the order of a millimeter.

An important difference exists between solid oxide fuel cells and other kinds of fuel cells in that various kinds of natural fuels or products of a relatively simple processing of such fuels may also be directly utilized. As we know, the original aim of all work on fuel cells has actually been precisely the direct transformation of the chemical energy of natural fuels to electrical energy. In seeking solutions to this problem, researchers have encountered numerous difficulties, which in many cases could not be overcome practically. These difficulties were associated with the very low rates of electrochemical oxidation of these fuels and, also, with the presence of various contaminants hindering and sometimes completely blocking these reactions. 

Porous media finds extensive application in chemical engineering. In certain cases they are simply used to increase the mass transfer rate between two distinct phases, while in certain other cases they are used to disperse the catalyst effectively. Catalytic packed beds are an integral part of any chemical production industry. Solid Oxide Fuel Cells are class of electrochemical devices where porous media finds important application. Over the years many models have been developed to study the transport processes in porous media, starting from simple Fickian approach to complex Dusty Gas Model GDGM). However, very little is done to validate the accuracy of these models under reaction conditions, especially with multi-component species mixtures. 

John M. Vohs is the Carl V.S. Patterson Professor and chair of the Department of Chemical and Biomolecular Engineering at the University of Pennsylvania. He joined the faculty there after receiving a B.S. degree from the University of Illinois and a Ph.D. from the University of Delaware. Dr. Vohs research interest is in the field of surface and interfacial science, particularly the relationships between the local atomic structure of surfaces and their chemical reactivity. His work on structure-activity relationships for metal-oxide catalysts, especially those used for selective oxidation reactions and automotive emissions control systems, is widely known. In recent years, he has collaborated in the development of solid-oxide fuel cells that run on readily available hydrocarbon fuels, such as natural gas and diesel. Dr. Vohs has received numerous honors, including an NSF Presidential Young Investigator Award and two Union Carbide Research Innovation Awards, vohs seas.upenn.edu)... 

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