Investigating the Solid Oxide Fuel Cell Anode Degradation Under Siloxane Contamination

Abstract

Siloxane, a typical contaminant component in biogas from wastewater treatment plants and landfills, can negatively affect prime movers such as solid oxide fuel cells (SOFCs) and engines due to its deposition. In order to investigate the solid oxide fuel cell nickel-yttria stabilized zirconia (Ni-YSZ) anode degradation mechanism because of siloxane contamination, three different experimental methods were conducted. First, fuels with different components were utilized for SOFCs with ppmv level siloxane. The degradation rates among different experiments were analyzed and compared to assess the influence of reactants on the siloxane degradation process. Then, Pure YSZ and Ni pellets were utilized to investigate their roles in siloxane deposition process individually. The pellet experiments can also reduce the complexity of deposition composition analysis by various techniques used in this study such as scanning electron microscopy, wavelength-dispersive X-Ray spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy and Raman spectroscopy. Acceleration degradation experiments for SOFCs were accomplished with percentage level siloxane contamination. In this case, the exhaust gas for the siloxane deposition process was analyzed by gas chromatography (GC) for gas phase product identification. After considering the experimental results from the three methods mentioned before, a new anode degradation mechanism is proposed. The chemical adsorption process of siloxanes on the anode is hypothesized as an essential process in deposition reactions. Beside silicon deposition, carbon deposition is also assessed in this study, and it is also considered to play a critical role in SOFCs’ degradation process.