Solid oxide fuel cells fueled by simulated biogas: Comparison of anode modification by infiltration and reforming catalytic layer

Solid oxide fuel cell (SOFC) provides a new method for clean and efficient conversion and utilization of hydrocarbon fuels due to its high fuel flexibility. The utilization of biogas fuel through direct internal reforming (DIR) allows for a simplification of the SOFC system since no external reformer appears strictly necessary. Despite its considerable convenience and potential, at present, direct internal dry reforming is still not considered as a competitive process for commercial application, which is limited by the reaction difficulty and high risk of carbon deposition. To address the problem, in this study, conventional Ni-yttrium stabilized zirconia (YSZ) anodes of SOFCs are modified by two methods, i.e. Ce0.9Gd0.1O2-delta (GDC) infiltration and a Ni-GDC reforming catalytic layer. A comparative study between the modified cells and the bare cell is made under operation with humidified H-2 and simulated biogas. Both of these two modification methods lead to a slight but acceptable decrease of the cell performance under humidified H-2. In the case of simulated biogas, results show that GDC infiltration is only beneficial to the cell performance with very low or very high CO2/CH4 molar ratio. While with a moderate CO2/CH4 ratio of 0.5-1.5, GDC infiltration instead results in a decrease of cell performance. However, the cell modified by a Ni-GDC catalytic layer shows superior performance towards the direct utilization of simulated biogas than the bare one and the one modified by GDC infiltration. The anode modification by a Ni-GDC catalytic layer can also improve the stability of the cell under simulated biogas, which is verified under different operating currents, although serious carbon deposition is detected in the catalytic layer afterwards.