Development of Cu-Ni-YSZ SOFC Anodes by Direct and Pulse Electroplating for Internal Reforming of Methane

The Cu-Ni-YSZ cermet anodes were fabricated via Cu-electroplating for direct utilization of methane in solid oxide fuel cells. Cu is good electronic conductor and inert to carbon formation. The low melting temperatures of Cu (1085 ^oC) and Cu₂O (1235 ^oC) are obstacles in the fabrication of cermet anodes. So the adding of Cu to anode was achieved after sintering of Ni-YSZ cemet anode. The electroplating of Cu inside the anode was performed by using both direct current plating and pulse plating methods. The amount of Cu and the thickness of Cu plated layer could be controlled depending on the various plating time, current density, Cu ion concentration in CuSO₄∙5H₂O and H₂SO₄ solution, and current on/off time. In comparison with DC plating, the uniform distribution of Cu was obtained with pulse plating. Because a continuous repeated sequence of nucleation and growth was generated with pulse plating. On the other hand, DC plating has the one nucleation step and continuous growth of Cu grain. When the electroplated Ni-YSZ anodes were exposed to methane at 700 ^oC, the amount of carbon deposition on the anode decreased as the amount of Cu plated in the anode increased. In this work, a single cell was prepared by tape-casting and screen printing. The green tapes of Ni-YSZ anode, Ni-YSZ functional layer, and YSZ electrolyte were laminated, iso-pressed, and then co-fired to 1350 ^oC. The LSM-YSZ cathode was screen-printed on the anode-supported electrolyte and sintered to 1150 ^oC. The Cu-electroplating to single cell was performed after the reduction of Ni-YSZ anode layer at 800 ^oC. The power density of single cell with Cu-Ni-YSZ anode was 0.25 W/cm² at 700 ^oC in methane. The Cu-Ni-YSZ anode supported single cell was operated stably for 200 h in methane. The dissociation of methane during the single cell test in methane, the exhaust gas was analyzed by the gas chromatography to determine the nature of the anode reaction products. The single cell with Cu-Ni-YSZ anode showed the lower efficiency of methane utilization than that Ni-YSZ anode cell. From these results, the Cu-Ni-YSZ anode is a possible component for the use of methane in SOFCs.