Solid oxide fuel cell anodes conventional

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. 

A single-chamber solid oxide fuel cell (SC-SOFC), which operates using a mixture of fuel and oxidant gases, provides several advantages over the conventional double-chamber SOFC, such as simplified cell structure with no sealing required and direct use of hydrocarbon fuel [1, 2], The oxygen activity at the electrodes of the SC-SOFC is not fixed and one electrode (anode) has a higher electrocatalytic activity for the oxidation of the fuel than the other (cathode). Oxidation reactions of a hydrocarbon fuel can... 

The anodes consisting of a nickel catalyst and of cermet mixed with yttria-doped zirconia electrolyte that are used in conventional solid oxide fuel cells also lose their ability to work at lower temperatures because of a loss of conductivity by the ceramic. This suggests that, for the ceramic in the anode, a material having a higher conductivity at intermediate temperatures should be used. It was in fact shown that an anode made with a nickel/samaria-doped ceria cermet has a much lower polarization than the conventional variant. 

Lan and Tao [22] successfully applied a novel fuel cell type with an alkaline membrane to oxidize ammonia at room temperature. Compared to solid oxide fuel cells, the alkaline membrane fuel cell is less brittle and can be operated at low temperatures. As an advantage of alkaline membrane fuel cells over conventional alkaline fuel cells, no KOH-based electrolyte is needed. The researchers used two types of anodes first platinum and ruthenium deposited on carbon and sec-raid chromium-decorated nickel. The ammraiia sources were either ammraiia gas or a 35 wt% aqueous ammonia solution. 

Solid Oxide Fuel Cells, Direct Hydrocarbon Type, Fig. 3 F iedicted gas constitution versus position in the SOFC anode support, for a current density of 1 A/cm. The top shows a cell with a conventional NiYSZ support and the bottom a Sro.8Lao.2Ti03 support Both cell types had a NiYSZ anode functional layer, YSZ electrolyte, and LSMYSZ (LSM = Lao.8Sro.2Mn03) cathode (From Ref [34])... 

As constructive alternatives, SOFCs can be used as planar or tubular SOFCs, respectively. In the past period, the planar SOFCs become more attractive for the commercialization because of their high power density and low production costs [2]. The planar SOFCs may also be divided into (i) electrolyte-supported and (ii) anode-supported solid oxide fuel cells. Also, more and more attention was focused on solid oxide fuel cells operating at low and/or intermediate temperatures. The decrease of temperature demands an electrolyte with higher ionic conductivity than, for example, the conventional YSZ. 

In conclusion, despite some attractive properties for these embedded Pd Ce02/Al203 catalysts, they are not ideal for WGS. Still, there are clear indications that core-shell-type materials have very different properties from conventional catalysts. The easily reducible, ceria shell in this new type of material could allow these catalysts to find applications in other areas. Indeed, we will show later in this chapter how these materials exhibit superior stability in solid oxide fuel cell (SOFC) anodes (see Section 7.3.3). 

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]. 

The coplanar fuel ceU design is used primarily for fuel cells with a mixed-reactant supply. In this design both selective electrodes (anodes and cathodes) are situated on the same surface of the electrolyte (ion-conducting membrane, matrix filled with liquid electrolyte, or solid electrolyte). This surface also contacts the reactant mixture. Such an electrolyte is said to be single-faced. This is in contrast to the conventional MEAs used for almost all varieties of fuel cells, in which the electrolyte is dual-faced, contacting the anode and the fuel on one side and the cathode and the oxidizer on the other side. 

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