Spatially resolved diagnostic in solid oxide cell short stack – multisampling analysis under pure hydrogen operation

This study presents a fully integrated diagnostic platform for a 10-cell electrolyte-supported solid oxide fuel cell short stack, enabling spatially resolved investigation of internal physicochemical phenomena under realistic operating conditions. The platform combines multisampling gas analysis, distributed temperature sensing, and per-cell electrochemical characterization within a single experimental framework. Eleven gas sampling ports along the fuel-electrode manifold and eleven thermocouples on the air side allow mapping of local hydrogen and water concentrations together with temperature distributions, while polarization curves and multichannel electrochemical impedance spectroscopy provide cell-resolved performance information. Statistical analyses based on correlation, partial correlation, and confidence interval assessment are employed to quantitatively link local gas composition, thermal behavior, and electrochemical response. The results show that compositional gradients are primarily governed by the fuel flow direction, with progressive hydrogen depletion and water accumulation along the anode channel, whereas temperature remains highly uniform across the stack, with minor gradients aligned with the air crossflow direction. Electrochemical analysis identifies an operating temperature of 835 °C as thermally and electrochemically optimal, minimizing activation and ohmic losses without significant performance gains at higher temperatures. While high cell-to-cell homogeneity is observed under reference conditions, localized performance effects emerge at extreme operating parameters such as high fuel utilization or elevated temperature. Overall, the proposed multi-domain diagnostic approach provides a robust experimental methodology for assessing chemical, thermal, and electrochemical non-uniformities in solid oxide fuel cell stacks, supporting improved stack design, control strategies, and durability assessment.