Improved catalytic properties of solid oxide fuel cell (SOFC) anodes by coated Ni/YSZ

The endothermal steam reforming reaction of methane within the anode chamber of solid oxide fuel cell (SOFC) stack (internal reforming) is favorably applied to reduce cost and improve the thermal balance within the stack. This reaction, catalysed by the Ni/YSZ anode material (substrate), is very fast and influences the temperature distribution in the stack considerably. In the fuel inlet area of the anode strong cooling can occur leading to large temperature gradients to the anode substrate. Therefore, the catalytic activity for reforming the Ni/YSZ has to be decreased at the top layer of the anode material which is in contact with the fuel gas mixture. On the other hand, at the interface between anode and electrolyte a high electrochemical activity is necessary. Hence, the anode has to be designed from a functionally graded material. To reduce the catalytic activity, YSZ coating was carried out without decreasing the gas permeability and the electrical conductivity of the substrate. Various sols prepared from precursors Y(NO sub 3 ) sub 3 bullet 6 H sub 2 O and Zr(OC sub 3 H sub 7 ) sub 4 were applied to the Ni/YSZ in order to verify the influence of the parameters mentioned above.