Electrochemical evaluation of sulfur poisoning in a methane-fuelled solid oxide fuel cell: Effect of current density and sulfur concentration

• Published in: Journal of power sources Vol. 272; pp. 776 - 785
• Main Authors: HAGEN, Anke, JOHNSON, Gregory B, HJALMARSSON, Per
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 25.12.2014
• Subjects: Applied sciences; Charge transfer; Current density; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Fuels; Mass transfer; Materials; Poisoning; Reforming; Solid oxide fuel cells; Sulfur; Methane; Sulfur content; Internal reforming; Ni/ScYSZ anode; Anode; Poisoning; Electrode material; Sulfur; Current density; Solid oxide fuel cell; Electrochemical characteristic; Sulfur poisoning
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2014.08.125

A Ni/ScYSZ based SOFC was tested at 1, 0.5, 0.25, and 0 (OCV) A cm super(-2) in methane fuel containing 0-100 ppm H sub(2)S. Analysis of cell voltage loss during short-term H sub(2)S poisoning showed that SOFC performance loss was generally larger at higher current loads. Separating the effect of H sub(2)S on catalytic reforming and electrochemical activity by evaluating the relevant area specific resistances and charge transfer processes based on impedance spectroscopy revealed that the poisoning of electrochemical activity was not dependent on current density. Two major anode processes were significantly affected by the presence of H sub(2)S in the fuel; the lower frequency mass transfer/fuel reforming processes and higher frequency charge transfer/triple phase boundary (TPB) processes. At high current densities (0.5 and 1 A cm super(-2)), mass transfer/fuel reforming processes were the most sensitive to sulfur poisoning. At OCV, the effect of sulfur was less pronounced on mass transfer/fuel reforming processes but quite significant on the charge transfer/TPB processes. Overall, sulfur related performance loss was more severe at the highest current density (1 A cm super(-2)), due to the deactivation of catalytic fuel reforming reactions in the anode, leading to less available fuel and a higher fuel utilization. All poisoning effects were reversible after removing H2S from the fuel.