Potential electrode materials for symmetrical solid oxide fuel cells

Chromites, titanates and Pt-YSZ-CeO, cermets have been investigated as potential electrode materials for an alternative concept of Solid Oxide Fuel Cell (SOFC), the symmetrical SOFCs (SFC). In this Configuration, the same electrode material is used simultaneously as anode and cathode.

Interconnector materials, Such as chromites, Could be considered as potential SFC electrodes, at least Under pore hydrogen-fed at relatively high temperatures, as they do not exhibit significant catalytic activity towards hydrocarbon oxidation. This may be overcome by partially Substituting Cr in the perovskite B-sites by other transition metal Cations Such as Mn. La0.75Sr0.25Cr0.5Mn0.5O3-delta (LSCM) is a good candidate for such SFCs, rendering fuel cell performances in excess of 500 and 300mW/cm(2) using pure H-2 and CH4 as fuel, at 950 degrees C.

Similarly, typical n-type electronic conductors traditionally regarded as anode materials, Such as strontium titanates, may also operate under oxidising conditions as cathodes by substituting some Ti content for Fe to introduce p-type conductivity. Preliminary electrochemical experiments on La4Sr8Ti12-xFexO38-delta-based SFCs show that they perform reasonably well under humidified H-2, at high temperatures.

A third group of materials is the Support material of any typical cermet anode, i.e. YSZ, CeO2 plus a current collector. It has been found that this combination Could be optimised to operate as SFC electrodes, rendering performances of 400mW/cm(2) under humidified pore H-2 at 950 degrees C.