Ceramic and Sulfur Tolerant Anodes

As discussed earUer in Section 2.1.2, conventional cermet anodes suffer from issues of redox stability, coking and sulfur poisoning. In an effort to develop high durabiUty anodes that overcome these limitations the modification of typical cermet materials to offer greater resistance to coking and sulfur poisoning has been considered. Elsewhere novel ceramic anodes have been proposed to achieve the same objective. Each of these potential materials solutions are attractive and will be addressed in turn. 

A number of approaches have been adopted to modify the current Ni-based cermets including substitution of Ni with alternative metals. Replacement of Ni with Cu has been reported to reduce the affinity of Ni for hydrocarbon cracking that leads to coking of the anode. In developing Cu cermets many strategies have demonstrated successful anode performance. Park et al. pioneered the use of Cu-based cermets demonstrating that SOFCs can operate effectively with a Cu-ceria cermet, where the ceria acts as a catalyst for the oxidation of hydrocarbons and Cu is used as it is an excellent electronic conductor. Synthesis of the cermets has 

INORGANIC MATERIALS FOR SOLID OXIDE FUEL CELLS 

Cu-CeOi-ScSZ cermet was tested with Hi and C1H5OH/H1O environments, but poor performance resulted at all temperatures, achieving a maximum power density of 372 mW cm at 800 °C and only 130 mW cm at 700 °C. 

To illustrate the effect of Cu content on carbon formation a series of Cu-Ni alloys were incorporated into YSZ-based anodes and significant suppression of coking achieved. It was also noted that the use of alloys is a relatively unexplored domain and of interest as the catalytic activity of the alloy is not directly related to the properties of the parent metals, and hence the alloy activity is not simply a summation of the two metals individual properties.  

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