Dimethyl sulphide poisoning of a Ni-anode SOFC stack: concentration dependence and reversibility

Biomass-derived fuels enable low-carbon power generation through solid oxide fuel cells (SOFCs); however, sulphur species present in biogas can severely degrade Ni-based anodes. Although H 2 S poisoning has been extensively studied in single cells, the impact of other sulphur compounds at stack level and realistic load conditions remains poorly understood. This study exposes a six-cell Ni-anode SOFC short stack to dimethyl sulphide (DMS) under biogas-relevant condi tions, probing degradation through IV curves, electrochemical impedance spectroscopy (EIS), distribution of relaxa tion times (DRT) analysis, and equivalent circuit modelling (ECM). Tests were performed at 750 ◦ fuel utilisation. C, 0.4 Acm 2 and 65% Under load, DMS poisoning (0.5, 1, 2.5 and 5 ppm) reveals voltage degradation trends consistent with con centration- and time-dependence, though not fully separable from exposure history. Electrochemical analysis shows that the anode charge-transfer process is selectively and substantially impaired, while gas-diffusion impedance evolves more gradually. Recovery upon contaminant removal confirms this degradation remains largely reversible within the investigated time window. Sulphur surface coverage, estimated using a Temkin-type adsorption model, correlates linearly with voltage loss, suggesting a coverage threshold of almost 0.7, below which degradation remains negligible. Together, these operando descriptors provide a preliminary, model- dependent framework for interpreting DMS poisoning trends at stack scale.