Influence of Microstructure on the Sulfur Tolerance of Ceria-Based Anodes in Low Temperature SOFC

Abstract

Hydrocarbon fuels such as natural gas or biogas commonly contain small amounts of impurities like sulfur which result in a strong degradation of the polarization resistance (R pol) in Ni/YSZ anodes. The sulfur poisons the nickel catalyst and hinders the electrooxidation of hydrogen. At common SOFC operation temperatures above 700 °C the R pol of a Ni/GDC anode is less influenced. The trend to a significantly lower operating temperature of SOFCs even below 600 °C raises the question to which extend the sulfur tolerance of ceria-based anodes is maintained. We analyzed the impact of H2S on the R pol of four ceria-based anodes, differing in their microstructure, at an operation temperature of 600 °C by electrochemical impedance spectroscopy (EIS). The distribution of relaxation times (DRT) analysis is applied to deconvolute the electrochemical processes followed by a complex nonlinear least square approximation to quantify the loss processes and the impact of sulfur.