Effect of hydrogen and carbon dioxide on the performance of methane fueled solid oxide fuel cell

Recycling and reusing of exhaust gas from solid oxide fuel cell (SOFC) could enhance the fuel utilization of methane. In the present work, the effects of two main components of exhaust gas, viz. hydrogen and carbon dioxide, on the performance of exhaust gas reforming methane fueled cell were investigated. The cell with Ni/8 mol% Y2O3 doped zirconia (Ni/YSZ) as the anode was exposed to H2CO2CH4 atmospheres at 800 °C. DC techniques and impedance spectroscopy was used for characterization. Two kinds of cells with different fuel utilization factors (Uf) were used in experiments, which represented different relationship of power density/voltage with current density. The results indicated that electrooxidation of H* dominated the electrochemical reaction on the anode of the cell at low Uf value, while electrooxidation of C* becomes important at high Uf value. In the case of CO2H2 mixtures, CO2 improved the exchange current density, raised the value of Uf, and depressed anodic activation polarization. As for H2CH4CO2 system, H2, partly replacing CH4, reduced the heat loss in dry reforming, improved the exchange current density, raised Uf value, and depressed the activation and concentration polarization resistances of Ni/YSZ anode. But it had limited effect on the power density of the cell with high Uf value.