Investigating the Influence of Ni, ZrO2, and Y2O3 from SOFC Anodes on Siloxane Deposition

Abstract

Siloxanes, as a type of impurity in biogas, can poison the Ni-YSZ anode of SOFCs. However, the influence of individual components of the anode, such as Ni, ZrO2, and Y2O3, on the siloxane deposition process has not been investigated extensively. In this study, Ni, ZrO2, and Y2O3 pellets were exposed to H2 + N2 + H2O + D4 (octamethylcyclotetrasiloxane, 2.5 ppmv) and H2 + N2 + D4 (2.5 ppmv siloxane) gas mixtures at 750 °C to investigate their affinity and tolerance for siloxane degradation. Surface morphology analysis and electrochemical analysis including electrochemical impedance spectroscopy (EIS), related distribution of relaxation times (DRT) analysis and equivalent circuit modeling with complex nonlinear least square (CNLS) fitting were conducted. A microstructure parameter—tortuosity factor to porosity ratio τ / ε calculated by diffusion polarization resistance was utilized for siloxane deposition evaluation. After comparing pellets surface morphology changes before and after experiments and τ / ε change following the contamination, Ni is considered as a major factor in siloxane deposition reactions in Ni-YSZ anode.