TY  - CONF
AU  - Edeh, Obinna
AU  - Schäfer, Dominik
AU  - Samsun, Remzi Can
AU  - Eichel, Rüdiger-A.
TI  - Impact of Gas Conversion Ratios on Impedance Response and Non-Linear Behavior of SOECs in Co-Electrolysis Mode
SN  - 2151-2043
PB  - RWTH Aachen
M1  - FZJ-2025-05668
PY  - 2025
AB  - High-temperature solid oxide electrolysis cells (SOECs) have emerged as a promising technology to produce green hydrogen and other valuable chemicals like syngas. SOECs offer several advantages over conventional electrolysis methods, including high efficiency, fuel flexibility, and the ability to operate at elevated temperatures, which favors the kinetics of electrochemical reactions.[1,2]However, the widespread adoption of SOEC technology faces challenges, particularly related to performance degradation and the complex interplay of operating parameters[3]. A crucial factor influencing SOEC performance is the gas conversion ratio (CR), which reflects the extent to which reactant gases (CO2 and H2O) are converted into products (CO and H2). While researchers have extensively studied the influence of CR using linear methods like EIS and nonlinear methods like THD in solid oxide fuel cells SOFCs[4], similar studies in SOECs have largely neglected the non-linear techniques. This creates a critical gap in understanding degradation mechanisms in SOECs, particularly those arising from nonlinearities such as mass transport limitations and beginning local reactant-starvation at high CR. By combining EIS and THD in our study, we provide an investigation of these effects in co-electrolysis mode, leveraging the strengths of both techniques to detect early nonlinear behavior and elucidating their impact on SOEC performance and durability at different CR.The study employs a comprehensive approach, utilizing electrochemical impedance spectroscopy (EIS) as the primary method, with distribution of relaxation times (DRT) analysis as a deconvolution tool for evaluating EIS spectra, along with the novel application of total harmonic distortion (THD) as a diagnostic tool.[4]. The findings reveal a strong correlation between increasing CR and significant changes in the impedance response of the SOEC stack. These changes point toward beginning localized reactant-starvation (CR getting close to 100 % locally) and mass transport limitations, as indicated by trends such as higher impedance values and elevated THD indices at high CR.Furthermore, this research proposes a mechanism linking the observed linear and non-linear behaviors to the dynamics of reactant and product transport within the SOEC. The insights gained from this investigation contribute to a more comprehensive understanding of SOEC operation under different CR, emphasizing the need to optimize operating conditions and electrode designs to mitigate mass transport limitations. This work aims to pave the way for enhancing SOEC performance, durability, and ultimately, the feasibility of large-scale implementation of this promising technology for a sustainable energy future.References[1] S. R. Foit, I. C. Vinke, L. G. J. de Haart, R.-A. Eichel, Angewandte Chemie International Edition 2017, 56, 5402–5411.[2] S. Gupta, M. Riegraf, R. Costa, M. P. Heddrich, K. A. Friedrich, Ind. Eng. Chem. Res. 2024, 63, 8705–8712.[3] B. Königshofer, M. Höber, G. Nusev, P. Boškoski, C. Hochenauer, V. Subotić, J. Power Sources 2022, 523, 230982.[4] H. Moussaoui, G. Hammerschmid, J. Van herle, V. Subotić, Journal of Power Sources 2023, 556, 232352.[5] G. Jeanmonod, S. Diethelm, J. Van Herle, J. Phys. Energy 2020, 2, 034002.[6] P. Caliandro, A. Nakajo, S. Diethelm, J. Van herle, Journal of Power Sources 2019, 436, 226838.[7] N. J. Steffy, S. V. Selvaganesh, M. Kumar L, A. K. Sahu, Journal of Power Sources 2018, 404, 81–88.[8] S. Thomas, S. C. Lee, A. K. Sahu, S. Park, International Journal of Hydrogen Energy 2014, 39, 4558–4565.
T2  - 19th International Symposium on Solid Oxide Fuel Cells
CY  - 14 Jul 2025 - 18 Jul 2025, Stockholm (Sweden)
Y2  - 14 Jul 2025 - 18 Jul 2025
M2  - Stockholm, Sweden
LB  - PUB:(DE-HGF)6
DO  - DOI:10.1149/MA2025-031253mtgabs
UR  - https://juser.fz-juelich.de/record/1049914
ER  -