Aggravated test of Intermediate temperature solid oxide fuel cells fed with tar-contaminated syngas

Abstract

Abstract In the present work, the effects of a tar-containing simulated syngas on an IT-SOFC (Intermediate Temperature Solid Oxide Fuel Cell) are evaluated. Performance and degradation rate of a planar anode-supported cell, operating under a simulated syngas obtained from steam-enriched air gasification of biomass, have been studied. The simulated syngas was contaminated using toluene as a model tar. Polarization curves and electrochemical impedance spectroscopy have been carried out under different toluene concentrations. A cell was then operated under a constant current density on a long run. EIS measurements were made during the operation to analyze the degradation, and the voltage evolution of the cell was compared to that obtained from another identical cell operated in clean syngas for 1000 h under similar conditions. A deep post-mortem characterization was performed by means of XRD measurements, Raman spectroscopy and SEM/EDS analysis. Results show that the presence of tar dramatically reduces the electrochemical performances of the cell, affecting both activation and mass transport processes. Post-mortem analysis shows the formation of carbon deposits, oxidation of Ni to NiO, segregation of ZrO 2 from the YSZ phase, particle coarsening and enhanced fragility of the anode structure, in good agreement with what suggested from the electrochemical results.