Double perovskite oxides BaGd0.8La0.2Co2O6-delta (BGLC), BaGdCo1.8Fe0.2O6-delta (BGCF), BaPrCo2O6-delta (BPC) and BaPrCo1.4Fe0.6O6-delta (BPCF) were investigated as oxygen electrodes on mixed concluding BaZr0.7Ce0.2Y0.1O3 (BZCY72) electrolyte using impedance spectroscopy vs temperature, pO(2), and pH(2)O. We propose and have applied a novel approach to extract and parameterise the charge transfer and diffusion impedances of the electrode reactions in a system comprising charge transport of protons, oxide ions, and electrons. Given by the properties of the BZCY72, transport of protons dominates at lower temperatures and high pH(2)O, oxide ions at higher temperatures, and electron holes increasingly at high temperatures and high pO(2). The electrodes showed good performance, with the lowest total apparent polarisation resistance for BGLC/BZCY72 being 0.05 and 10 Omega cm(2) at 650 and 350 degrees C, respectively. The low temperature rate limiting reaction step is a surface related process, involving protonic species, with an activation energy of approximately 50 kJ mol(-1) for BGLC/BZCY72. The oxide ion transport taking over at higher temperatures exhibits a higher activation energy typical of SOFC cathodes. Thermogravimetric studies revealed that BGLC exhibits considerable protonation at 300-400 degrees C, which may be interpreted as hydration with an enthalpy of approximately -50 kJ mol(-1). The resulting mixed proton electron conduction may explain its good performance as electrode on BZCY72. (C) 2015 Elsevier B.V. All rights reserved.