A tolerance criterion for tar concentration in a model wood gas for a nickel/scandia-stabilized zirconia cermet anode in a solid oxide fuel cell

Durability of a nickel and scandia-stabilized zirconia cermet anode against toluene in hydrogen was evaluated in this paper. Anode deterioration was judged by the loss of elemental nickel from a surface of an anode. Elemental nickel loss was observed when the toluene concentration was 3 or 10 g/Nm3, steam to carbon ratio was 1, and current density was 0.5 A/cm2 at both temperatures: 1073 K and 1173 K. Therefore the tolerance criterion must be less than 3 g/Nm3 in hydrogen in the experimental conditions. However, the deterioration can be mitigated to some extent by increasing the operating temperature, steam-to-carbon ratio, or current density. Anode deterioration was also mitigated when hydrogen concentration in the fuel gas was nearly identical to that of wood gas. The influence of hydrogen concentration in the fuel gas on deterioration may be substantial. The loss of elemental nickel could not be detected instantaneously by electrochemical diagnosis.

► The tolerance criterion was less than 3 g/Nm3 of toluene in hydrogen.
► Anode deterioration can be mitigated somewhat by controlling operating conditions.
► The anode deterioration could not be detected by electrochemical diagnosis.