Within the framework of developing reversible solid oxide fuel cells/solid oxide electrolysis cells (SOFCs/ SOECs), we have engaged in the design of high-performance electrodes. Facile production of hollow spherical particles of samaria-doped ceria (SDC) decorated with Ni-Co alloy catalysts (Ni 100ÀX Co X /SDC, X ¼ 0-50 atom%), nanometers in size, was adopted. A distinctive microstructure was observed in the hydrogen electrode fabricated with this composite powder. The cobalt addition played a significant role in evolution of the microstructure and effectively enlarged the electrochemical reaction zone. Under SOFC/SOEC reversible operation, the optimal performance characterized by a comparatively low ohmic resistance and high electrocatalytic activity was achieved with the Ni 80 Co 20 /SDC composition. At 900 C and an overpotential of 0.1 V, the current density reached remarkably high values of 0.18 and 0.37 A cm À2 in SOFC and SOEC operation, respectively.

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We have synthesized nanometer-sized Ni100−XCoX (X = 0 to 50) alloy catalysts supported on hollow particles of samaria-doped ceria [SDC, (CeO2)0.8(SmO1.5)0.2] by spraying a mixed solution of the corresponding metal nitrates and acetates in an atmospheric pressure plasma. The performances of Ni80Co20/SDC catalyst in both an SOFC and a steam electrolysis (p[H2O] = 0.6 atm) were found to be the highest among alloys and pure Ni (X = 0) supported on the SDC at 800 to 900oC.