Impact of trace contaminants on SOFC operated with bio-syngas: sulphur and siloxane-induced degradation

The energy valorisation of bio-syngas in Solid Oxide Fuel Cells (SOFCs) offers a highly efficient and sustainable alternative to conventional combustion-based systems. However, trace contaminants in syngas pose a challenge to long-term SOFC performance and durability (higher than in conventional ICEs). While most of previous works focused on hydrogen sulphide, other sulphur- and silicon-containing impurities, commonly found in bio-syngas, remain largely unexplored. This study investigates the impact of dimethyl sulphide (DMS), carbonyl sulphide (COS), and decamethylcyclopentasiloxane (D5), on the electrochemical performance of an anode-supported button-type SOFC operated with simulated bio-syngas at 750 °C. The degradation behaviour was assessed through periodic Electrochemical Impedance Spectroscopy (EIS), at different contaminant levels. Data were analysed using both equivalent circuit models and the Distribution of Relaxation Times (DRT) to distinguish degradation processes. Results reveal that sulphur-containing compounds significantly accelerate deterioration, primarily through increased charge transfer resistance associated with active site poisoning. In contrast, D5 causes a more moderate degradation trend, attributed to increased mass transport limitations at low frequencies. This comprehensive study provides valuable insights into the degradation mechanisms induced by representative syngas contaminants and highlights the critical need for effective syngas purification strategies to enable the reliable deployment of SOFC systems in biomass-integrated energy applications.