addi-tive were studied by means of impedance spectroscopy in binary gas mixtures x% H2 + (100 – x)% H2O,
10%CO + 90% CO2 and multicomponent gas mixtures H2 + CO2 + H2O + CO + Ar of various composition at
the temperature of 900C. The Ni cermet electrode degradation rate in binary gas mixtures H2 + H2O was
shown to increase sharply at the partial water pressure over 45%. The Ni cermet electrode degradation rate in
the mixture of 10% CO + 90% CO2 was significantly lower than that in 10% H2 + 90% H2O. The major changes
in the electrode characteristics upon long exposure in working conditions were accounted for by changes in the
high-frequency partial polarization resistance. In the course of long testing, the electrode microstructure was
not significantly changed. In the presence of hydrogen-containing components (H2 and H2O), the carbon-con-
taining components (CO and CO2) were shown to make an insignificant contribution to the current generation
processes in Ni cermet electrode. It was suggested that strong degradation of Ni cermet electrode was caused
by poisoning its reaction sites with strongly linked adsorption forms of water (hydroxyls) at the positive charge
of electrode.