Electrocatalytic Operation of Solid Electrolyte Cells

Solid electrolyte fuel cells have been investigated intensively during the last three decades. Their operating principle is shown schematically in Fig. 4. The positive electrode (cathode) acts as an electrocatalyst to promote the electrocatalytic reduction of 02(g) to O  

Although several metals, such as Pt and Ag, can also act as electrocatalysts for the reaction in Eq. (7), the most efficient electrocatalysts known so far are perovskites such as Lai-jfSrjpMnOa. These materials are mixed conductors that is, they exhibit both anionic (0 ) and electronic conductivity. This, in principle, can extend the electrocatalytically active zone to include not only the tpb but also the entire gas-exposed electrode surface. 

The negative electrode (anode) acts as an electrocatalyst for the reaction of O with the fuel, for example, H2  

Fuel cells such as the one shown in Fig. 4a convert H2 to H2O and produce electrical power with no intermediate combustion cycle. Thus, their thermodynamic efficiency compares favorably with thermal power generation which is limited by Carnot-type constraints. One important advantage of solid electrolyte fuel cells is that, owing to their high operating temperature (typically 700°C to 11(X) C), they offer the possibility of internal reforming, which permits the use of fuels such as methane without a separate external neformer.  

In recent years, it was shown that solid electrolyte fuel cells with appropriate electrocatalytic anodes can be used for chemical cogeneration, that is, for the simultaneous production of electrical power and useful chemicals. This mode of operation, first demonstrated for the case of NH3 conversion to combines the concepts of a fuel cell and 

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Electrocatalytic Operation of Solid Electrolyte Cells. - Solid electrolyte cells based on YSZ can be used as fuel cells for electrical power generation One porous electrode... 

Decreasing operation temperature of solid oxide fuel cells (SOFCs) and electrocatalytic reactors down to 800-1100 K requires developments of novel materials for electrodes and catalytic layers, applied onto the surface of solid electrolyte or mixed conducting membranes, with a high performance at reduced temperatures. Highly-dispersed active oxide powders can be prepared and deposited using various techniques, such as spray pyrolysis, sol-gel method, co-precipitation, electron beam deposition etc. However, most of these methods are relatively expensive or based on the use of complex equipment. This makes it necessary to search for alternative synthesis and porous-layer processing routes, enabling to decrease the costs of electrochemical cells. Recently, one synthesis technique based on the use... 

PANI-NTs synthesized by a template method on commercial carbon cloth have been used as the catalyst support for Pt particles for the electro-oxidation of methanol [501]. The Pt-incorporated PANl-NT electrode exhibited excellent catalytic activity and stabUity compared to 20 wt% Pt supported on VulcanXC 72R carbon and Pt supported on a conventional PANI electrode. The electrode fabrication used in this investigation is particularly attractive to adopt in solid polymer electrolyte-based fuel cells, which arc usually operated under methanol or hydrogen. The higher thermal stabUity of y-Mn02 nanoparticles-coated PANI-NFs on carbon electrodes and their activity in formic acid oxidation pomits the realization of Pt-free anodes for formic acid fuel cells [260]. The exceUent electrocatalytic activity of Pd/ PANI-NFs film has recently been confirmed in the electro-oxidation reactions of formic acid in acidic media, and ethanol/methanol in alkaline medium, making it a potential candidate for direct fuel cells in both acidic and alkaline media [502]. 

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