We report the optimization of the dopant concentration of gadolinia-doped ceria (GDC) to enhance the oxygen reduction reaction (ORR) kinetics for low-temperature solid oxide fuel cells (LTSOFCs). Crystalline GDC layers with uniform nano-granular structures were prepared by aerosol-assisted chemical vapor deposition (AACVD) on the cathode side of a GDC electrolyte. The current-voltage (I-V) characteristics and power performances of the AACVD GDC-treated cells were measured and their cathodic reactions were analyzed by electrochemical impedance spectroscopy (EIS) to investigate the effect of GDC treatments with various dopant compositions. The cell treated with Gd0.14Ce0.86O2-delta was found to show an optimized power performance with the best ORR kinetics, due to its nano-granular structure and high concentration of oxygen vacancies. (C) 2017 Published by Elsevier B.V.