Because of the large cathode polarization of solid oxide fuel cells (SOFCs) at intermediate operating temperatures, great efforts have been made in developing new cathode material and controlling the cathode microstructure to promote cell performance. The potential reaction and the mismatch of thermal expansion coefficient (TEC) between cathode and electrolyte requires a “barrier layer” inserted between them. Gadolinium doped ceria (GDC), owing to its good ionic conductivity and good match of TEC between cathode and electrolyte layer, is widely used as the barrier layer material. The barrier layer plays an important role in charge carrier transportation and electrochemical reaction at triple phase boundary. In this work, praseodymium and gadolinium co-doped ceria, Pr_0.1Gd_0.1Ce_0.8O_2-δ (PGCO), is used as a novel interlayer to optimize the cathode performance due to its better electronic conductivity than GDC and active Pr(III)/Pr(IV) couples in oxygen reduction reaction. Distribution of relaxation time is applied to analyze the mechanism of the enhanced performance.