Palliative effects of H2 on SOFCs operating with carbon containing fuels

• Published in: Journal of power sources Vol. 372; pp. 188 - 195
• Main Authors: Reeping, Kyle W., Bohn, Jessie M., Walker, Robert A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 31.12.2017
• Subjects: Biogas; Chlorine; Hydrogen; Methane; Raman; SOFC; Methane; Biogas; Raman; Chlorine; Hydrogen; SOFC
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2017.10.071

Chlorine can accelerate degradation of solid oxide fuel cell (SOFC) Ni-based anodes operating on carbon containing fuels through several different mechanisms. However, supplementing the fuel with a small percentage of excess molecular hydrogen effectively masks the degradation to the catalytic activity of the Ni and carbon fuel cracking reaction reactions. Experiments described in this work explore the chemistry behind the "palliative" effect of hydrogen on SOFCs operating with chlorine-contaminated, carbon-containing fuels using a suite of independent, complementary techniques. Operando Raman spectroscopy is used to monitor carbon accumulation and, by inference, Ni catalytic activity while electrochemical techniques including electrochemical impedance spectroscopy and voltammetry are used to monitor overall cell performance. Briefly, hydrogen not only completely hides degradation observed with chlorine-contaminated carbon-containing fuels, but also actively removes adsorbed chlorine from the surface of the Ni, allowing for the methane cracking reaction to continue, albeit at a slower rate. When hydrogen is removed from the fuel stream the cell fails immediately due to chlorine occupation of methane/biogas reaction sites. [Display omitted] •Hydrogen masks Cl induced SOFC anode degradation when operating with carbon based fuels.•A mechanism is proposed to explain chlorine contamination of SOFCs operating with H2.•Methane and biogas promote degradation via separate pathways when Cl is present.