Co-deficient PrBaCo2-xO6-delta perovskites (x = 0, 0.02, 0.06 and 0.1) are synthesized by a solid-state reaction, and the effects of Co-deficiency on the crystal structure, oxygen non-stoichiometry and electrochemical properties are investigated. The PrBaCo2-xO6-delta samples have an orthorhombic layered perovskite structure with double c axis. The degree of oxygen nonstoichiometry increases with decreasing Co content (0 <= x <= 0.06) and then slightly decreases at x = 0.1. All the samples exhibit the electrical conductivity values of >300 S cm(-1) in the temperature range of 100-800 degrees C in air, which match well the requirement of cathode. With significantly enhanced electrochemical performance and good chemical compatibility between PrBaCo2-xO6-delta a and CGO, this system of Co-deficient perovskite is promising cathode material for IT-SOFCs. Among all these components, PrBaCo1.94O6-delta gives lowest polarization resistance of 0.059 Omega cm(2) at 700 degrees C in air. When tested as cathode in fuel cell, the anode-supported Ni-YSZ vertical bar YSZ vertical bar CGO vertical bar PrBaCo1.94O6-delta cell delivers a maximum peak power density of 889 mW cm(-2) at 650 degrees C, which is higher than that of PrBaCo2-xO6-delta cathode-based cell (764 mW cm(-2)). The oxygen reduction kinetics at the PrBaCo1.94O6-delta cathode interface is also explored, and the rate-limiting steps for oxygen reduction reaction are determined. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.