The electric power produced by a Ni/Gd-doped ceria (GDC) anode-supported solid oxide fuel cell with a GDC electrolyte (40¯m thick) and a (La 0.8 Sr 0.2 )(Co 0.8 Fe 0.2 )O 3 (LSCF) cathode using a 3 vol % H 2 O-containing H 2 fuel was measured. The addition of 10 or 50 mass % GDC powder (Ce 0.8 Gd 0.2 O 1.9 ) to the LSCF cathode reduced the power density from 320 mW/cm 2 in the case of no GDC to 137 or 122 mW/cm 2 , respectively. The added GDC particles blocked the conduction path between LSFC particles. The as-prepared LSCF powder was ball-milled using ¡-Al 2 O 3 balls. The milling decreased the charge transfer resistance at the cathode and increased the power density of the fuel cell.©2014 The Ceramic Society of Japan. All rights reserved.Key-words : Solid oxide fuel cell, Cathode, Power density, Overpotential, Gd-doped ceria [Received September 2, 2013; Accepted December 24, 2013] Solid oxide fuel cells (SOFCs) are attractive electric power generators because of their high energy conversion efficiency, their ability to utilize a variety of fuels, the possibility of utilizing their high-temperature exhaust gas, and their leakage-proof property because of the use of solid electrolytes. A conventional SOFC with a yttria-stabilized zirconia (YSZ) electrolyte is typically operated at approximately 800°C to enhance the diffusion of oxide ions formed at its cathode. Gd-doped ceria (GDC) and Sm-doped ceria are also candidate electrolytes for SOFCs because they exhibit greater oxide-ion conductivity than YSZ. Decreasing the charge transfer resistance of electrochemical reactions at the electrodes (especially the cathode) is another strategy to increase the electric power generated by SOFCs. At the cathode, the diffusing oxygen molecules adsorb onto the cathode material and dissociate into oxygen atoms. The oxygen atoms react with electrons to form oxide ions at the triple-phase boundary (TPB, the gascathodeelectrolyte interface). The cathode material is a mixed conductor of electrons and oxide ions. A cathode composed of a mixture of GDC and LSCF is expected to exhibit enhanced electrocatalytic activity for the reaction of O 2 and electrons. Shah et al.3) measured the performance of a cathode fabricated by impregnating a porous GDC scaffold with a mixed nitrate solution of LSCF precursor. The formed nanometer-scale (50 nm) LSCF network reduced the charge transfer resistance at an operating temperature of 650°C over 300 h. Liu et al. 4) prepared an LSCFGDC composite cathode by impregnating the porous GDC scaffold with a mixed nitrate solution of La, Sr, Co, and Fe and measured the degradation in the composite cathode performance at 750°C in air over 500 h. The GDC scaffold method was effective in expanding the triple-phase boundary (GDC electrolyteLSCF cathodeO 2 gas). However, the charge transfer resistance and ohmic resistance increased because of grain growth of the LSCF nanoparticles. The authors suppressed the grain growth of LSCF by adding MgO and LaNi 0.6 Fe 0.4 O 3 particles.In this study, a GDCLSCF mixed cat...
