Classification criteria for solid oxide fuel cell electrode materials

In an attempt to establish comparison criteria for the electrocatalytical properties of electrode materials, systematic measurements were carried out on microelectrodes of simple shapes. The overpotential resistances were normalized with respect to the electrode triple-phase boundary length and the electrode capacitances to the electrode interface area. Results obtained on metals such as Ag, Pt, Au, and Ni, and on some oxides, under either cathodic or anodic atmospheres, show marked differences which allow us to classify them. The positions of several materials in the cathode and anode material lists can be significantly different, indicating different electrocatalytical requirements under solid oxide fuel cell cathode and anode atmospheres. The dearest example is silver, which exhibits excellent electrocatalytical properties for the oxygen electrode reaction and very poor properties for hydrogen oxidation.