The mixed ionic-electronic conductor La2NiO4+delta was investigated as potential cathode material for protonic conducting solid oxide fuel cells (PC-SOFCs) based on La5.5WO11.25-delta electrolyte. Firstly the chemical compatibility between cathode and electrolyte phases (La2NiO4+delta and La5.5WO11.25-delta respectively) was studied. Then, the electrochemical properties of this cathode were improved by partially substituting La and/or Ni, specifically La1.5Pr0.5NiO4+delta and La(1.5)Pro(0.5)Nio(0.8)Co(0.2)O(4+delta) were considered. These two doped materials showed improved electrical conductivity and reduced polarization resistance, when tested as cathode in symmetrical cells. In a second step, the microstructure of La(1.5)Pro(0.5)Nio(0.8)Co(0.2)O(4+delta) was optimized by varying the firing temperature of the cathode. The performance of these mixed conductors is limited by medium frequencies associated processes while they show lower polarization resistances (Rp) than conventional composites based on La5.5WO11.25-delta and pure electronic conductors. La(1.5)Pro(0.5)Nio(0.8)Co(0.2)O(4+delta) cathode sintered at 1050 degrees C exhibits the best electrochemical performance on a La5.5WO11.25-delta-based PC-SOFC, achieving Rp = 0.62 Omega cm(2) at 750 degrees C in wet air. (C) 2013 Elsevier B.V. All rights reserved.