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 cell (SOFCs); however, sulphur species present in biogas can severely degrade Ni-based anodes. Although H2S poisoning has been extensively studied in single cells, the impact of other sulphur compounds under 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 conditions, probing degradation through IV curves, electrochemical impedance spectroscopy (EIS), distribution of relaxation times (DRT) analysis, and equivalent circuit modelling (ECM).Under load, DMS poisoning (0.5, 1, 2.5 and 5 ppm) induces a clear concentration- and time-dependent voltage degradation. The electrochemical analysis shows that anode charge-transfer process is selectively and substantially impaired, while gas-diffusion impedance evolves more gradually. Recovery upon contaminant removal confirms that the dominant degradation mechanism remains largely reversible within the investigated time window. In addition, sulphur surface coverage, estimated using a Temkin-type adsorption model, correlates linearly with voltage loss, revealing a concentration threshold equal to 0.678 below which degradation remains negligible. Together, these operando descriptors establish a diagnostic and tolerance framework for DMS poisoning at stack scale.