Electrochemical and microstructural analysis of nickel-yttria-stabilized zirconia electrode operated in phosphorus-containing syngas

Trace impurities in coal-derived syngas pose a threat on the performance and durability of solid oxide fuel cells (SOFCs) operated in syngas. A Ni-YSZ/YSZ/Ni-YSZ (YSZ stands for yttria-stabilized zirconia) half-cell is constructed in order to evaluate the effects of a phosphorus impurity on the performance of the Ni-YSZ cermet anode in the simulated coal-derived syngas containing 30.6% H-2, 30% CO, 11.8% CO2, 27.6% H2O and 20 pprn PH3. Electrochemical impedance analysis shows that both the charge transfer resistance and the diffusion resistance increase with time during exposure to the P-containing syngas. The diffusion resistance increases faster than the charge transfer resistance. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies show that phosphorus is incorporated into the Ni-YSZ electrode, leading to the formation of secondary phases of nickel phosphate and zirconium phosphate. The incorporation of phosphorus into the anode is accelerated by an applied electric field. (C) 2008 Elsevier B.V. All rights reserved.