Assessment of nickel cermets and La_0.8Sr_0.2Sc_0.2Mn_0.8O₃ as solid-oxide fuel cell anodes operating on carbon monoxide fuel

Ni-SDC, Ni-ScSZ, and La_0.8Sr_0.2Sc_0.2Mn_0.8O₃ (LSSM) anodes are investigated for SOFCs operating on CO. O₂-TPO and SEM results demonstrate LSSM is greatly superior to nickel cermet anodes in suppressing carbon deposition. H₂-TPR suggests there is strong chemical interaction between NiO and ScSZ, which helps to suppress the carbon deposition. Raman spectroscopy of the carbon-deposited nickel cermet anodes demonstrates the graphitization degree of carbon is enhanced with increasing temperature. The cell performance is much lower operating on CO as compared to H₂, and the reduction is the largest for the cell with Ni-SDC anode. Furthermore, steady performance degradation is observed for all three cells operating on pure CO which is irreversible for the cell with Ni-SDC anode while largely reversible for the cell with Ni-ScSZ anode. The degradation for the cell with an LSSM anode is found to be due to the phase instability of LSSM in pure CO atmosphere. By applying a mixture of CO and CO₂ as the fuel or under polarization, the phase of LSSM is stabilized; as a result, the cell is stably operated on CO under current polarization. This suggests that LSSM and Ni-ScSZ anodes are greatly superior to the Ni-SDC anode for operation on CO.