High Temperature Steam Electrolysis using Proton Conducting Cells is a promising method for large-scale hydrogen production, but such system requires the development of new electrode materials ideally presenting Mixed Proton and Electron Conductivity. Different cobaltites were investigated in terms of durability and compatibility with the BaZr0.6Y0.1O3 proton conducting electrolyte. REBaCo2O5+delta (RE = Pr, Nd, Sm, Gd, Y),YBaCo4O7, Ca3Co4O9 and Ca3Co2O6, were considered, among which the vacancy ordered perovskites were found to be the most stable in wet air. Oxygen vacancy formation and hydration properties of REBaCo2O5+delta were studied by iodometry and TGA in dry and wet atmospheres, respectively. (C) 2014 Elsevier B.V. All rights reserved.