Solid oxide fuel cell electrochemical reaction

Setoguchi, T. et al., Effects of anode materials and fuel on anodic reaction of solid oxide fuel-cells,/. Electrochem. Soc., 139, 2875-2880 (1993). 

Solid oxide fuel cells with reaction-selective electrodes. 192nd Meeting of the Electrochemical Society, Abstract No. 2191, p. 2562. 

Reactions (3.9) to (3.11) proceed rapidly to equilibrium in most anodic solid oxide fuel cell (SOFC) environments and thus H2 (Eq. 3.8) rather than CH4 is oxidized electrochemically resulting in low polarization losses. Upon doubling the stoichiometric coefficients of equation (3.8), summing equations (3.8) to (3.11) and dividing the resulting coefficients by two one obtains ... 

Tsipis EV, Kharton VV (2008) Electrode materials and reaction mechanisms in solid oxide fuel cells A brief review I. Performance-determining factors. J Solid State Electrochem 12 1039-1060 II. Electrochemical behavior vs. materials science aspects, ibid 1367-1391... 

In solid oxide fuel cells (SOFCs), the cathode is the material where pure oxygen or oxygen from air is reduced through the following electrochemical reaction [1]... 

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.

A solid oxide fuel cell is an electrochemical device which converts the Gibbs free enthalpy of the combustion reaction of a fuel and an oxidant gas (air) as far as possible directly into electricity. Hydrogen and oxygen are used to illustrate the simplest case. This allows the calculation of the reversible work for the reversible reaction. Heat must be transferred reversibly as well to the surrounding environment in this instance. 

Suzuki, M., Shikazono, N., Fukagata, K. and Kasagi, N. (2006) Numerical analysis of heat/mass transfer and electrochemical reaction in an anode supported flat-tube solid oxide fuel cell, in Proceedings of FUELCELL2006, The 4th International Conference on Fuel Cell Science Engineering and Technology, Irvine, CA, June 19-21. 

Hibino, T., Hashimoto, A., Yano, M., Suzuki, M., Yoshida, S., and Sano, M. A Solid Oxide Fuel Cell Using an Exothermic Reaction as the Heat Source, Journal of the Electrochem. Soc., 148, A544 (2001). 

The present availabihty of numerous types of solid electrolytes permits transport control of various kinds of mobile ionic species through those solid electrolytes in solid electrochemical cells, and permits electrochemical reactions to be carried out with the surrounding vapor phase to form products of interest. This interfacing of modem vapor deposition technology and solid state ionic technology has led to the recent development of polarized electrochemical vapor deposition (PEVD). PEVD has been applied to fabricate two types of solid state ionic devices, i.e., solid state potenfiometric sensors and solid oxide fuel cells. Investigations show that PEVD is the most suitable technique to improve the solid electrolyte/electrode contact and subsequently, the performance of these solid state ionic devices. 

Kuchynka et al. [125] studied the electrochemical oxidative dimerization of methane to C2 hydrocarbon species using perovskite anode electrocatalysts. Three designs of solid oxide fuel cells were used, including tubular and flat plate solid electrolytes. The maximum current density for the dimerization reaction at these electrocatalysts was related to the oxygen binding energies on the catalyst surface. The anodic reaction was ... 

Ihara, M., Kusano, T., Yokoyama, C. Competitive adsorption reaction mechanism of Ni/yttria-stabilized zirconia cermet anodes in H-2-H2O solid oxide fuel cells. J. Electrochem. Soc. 2001,148, A209-19. 

DjUah, N. and Lu, D., Mathematical modelling of the transport phenomena and the chemical/electrochemical reactions on solid oxide fuel cells, Int. J. Therm. Sci. 41 (2002) 29 0. 

The principles behind this membrane technology originate from solid-state electrochemistry. Conventional electrochemical halfceU reactions can be written for chemical processes occurring on each respective membrane surface. Since the general chemistry under discussion here is thermodynamically downhill, one might view these devices as short-circuited solid oxide fuel cells (SOFCs), although the ceramics used for oxygen transport are often quite different. SOFCs most frequently use fluorite-based solid electrolytes - often yttria stabUized zirco-nia (YSZ) and sometimes ceria. In comparison, dense ceramics for membrane applications most often possess a perovskite-related lattice. The key fundamental... 

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. 

The formed hydrogen by the water gas shift reaction can be electrochenticaUy oxidized in the fuel cell to water, electrical energy and heat. In solid oxide fuel cells the product water of the electrochemical oxidation of hydrogen is formed oti the anode site. This product water is available for the water gas shift reactimi on the anode side. At 650 to 850 °C reaction kinetics allows the water gas shift reaction without any catalyst or promoter. So carbon monoxide can be converted directly rai the anode side of the SOFC without any extra catalyst for promoting the water gas shift reaction. No extra converter is needed for the water gas shift reaction in SOFC fuel-cell heating appliances, which reduces the system effort. 

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