Abstract
The cathodic polarization of the 
electrodes sputtered on yttria stabilized zirconia electrolyte was studied at 800°C in air. The 
system showed high electrode activity for oxygen reduction. The study of the electrode resistance as functions of 
and temperature revealed that the rate‐determining steps for oxygen reduction were as follows: the charge transfer process for 
, the dissociation of oxygen molecules on the surface for 
and 
, and the oxygen diffusion on the electrode surface for 
. The marked electrode activity of 
was explained by the large effective reaction surface area, which is caused by the high oxide ion diffusivity and the high dissociation ability of oxygen molecules. In 
, the ability of the dissociation of oxygen molecules was considered to be lower than that in 
. The low activity of Cr‐perovskite electrode was explained by the low diffusivity of oxygen ions.