Electrochemical performance and carbon resistance comparison between Sn, Cu, Ag, and Rh-doped Ni/ScCeSZ anode SOFCs operated by biogas

Ni/ScCeSZ anode-supported SOFCs were fabricated via the reverse tape casting method and an LSCF (La0.6Sr0.4Cr0.2Fe0.8O3) cathode was applied. In order to prevent the chemical reaction of zirconia from the electrolyte and strontium from the cathode, a thin barrier layer of Gd0.1Ce0.9O1.95 (GDC) was painted on the ScCeSZ electrolyte. On the anode side, Sn, Cu, Ag, and Rh were doped into the Ni-based cermet by infiltration. Metal nitrate hydrates were used as precursors for the dopants. The prepared cells were tested in hydrogen (H2:N2=3:1) and then simulated biogas (CH4:CO2:N2=2:1:1) at intermediate operating temperature (600 to 750 °C). The tested cells used ambient air as the oxidant for the electrochemical reactions. The obtained cells were characterised by, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), and X-ray diffraction (XRD). The electrochemical performance of the prepared cells was characterised by OCV, I-V, operational stability (potentiostatic and galvanostatic), and electrochemical impedance spectroscopy (EIS).
According to our previous work, the carbon accumulation on the anode surface was successfully suppressed by infiltrating Sn, Ag, or Cu into the Ni/YSZ anode-supported cells under biogas operation at 750 °C. The addition of a small amount of Sn or Ag to the Ni/YSZ anodes can greatly improve the electrochemical performance and the operational stability of the cells operated on biogas. Due to the low melting point of Cu, the performance of Cu-Ni/YSZ anodes did not drastically improve. Hence, the Cu-doped Ni/ScCeSZ cells with LSCF cathode are expected to obtain better electrochemical results at slightly lower operating temperature.