Effects of dry methane concentration on the methane reactions at Ni-YSZ anode in solid oxide fuel cell

The dry methane with different concentration was used to research the dry methane reactions at Ni-YSZ anode in solid oxide fuel cell (SOFC). The anode exhaust gases were measured by on-line chromatography. The reactions of dry methane with different concentration at SOFC Ni-YSZ anodes were analyzed by summarizing the anode exhaust gases regular pattern for different reactions. The mathematical relationships between dry methane concentration and current for different anode reaction were studied. As the oxygen ion concentration at the anode three-phase boundary increasing continuously, the following reactions with low concentration methane occurs in sequence of CH₄+O^2- → CO+2H₂+2e^-, CH₄+2O^2- → CO+H₂O+H₂+e^-, CH₄+3O^2- → CO+2H₂O+6e^- and CH₄+4O^2- → CO₂+2H₂O+8e^-. The first two or three reactions occurred with medium methane concentration, while the first reaction occurred only with high methane concentration. The judgment for methane in low, medium or high concentrations were q_v(CH₄)≤I/(4F)、I/(4F)≤q_v(CH₄)≤I/(2F)、q_v(CH₄)≥I/(2F) which are based on Faraday's first law and the relationship among the reactant species.