The effect of HCl in syngas on Ni-YSZ anode-supported solid oxide fuel cells

The Ni-YSZ cermet anode of the solid oxide fuel cell (SOFC) has excellent electrochemical performance in a clean blended synthetic coal syngas mixture. However, chloride, one of the major contaminants existing in coal-derived syngas, may poison the Ni-YSZ cermet and cause degradation in cell performance. Both hydrogen chloride (HCl) and chlorine (Cl(2)) have been reported to attack the Ni in the anode when using electrolyte-supported SOFCs. In this paper, a commercial anode-supported SOFC was exposed to syngas with a concentration of 100 ppm HCl under a constant current load at 800 degrees C for 300 h and 850 degrees C for 100 h. The cell performance was evaluated periodically using electrochemical methods. A unique feature of this experiment is that the active central part of the anode was exposed directly to the fuel without an intervening current collector. Post-mortem analyses of the SOFC anode were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results show that the 100 ppm concentration of HCl causes about 3% loss of performance for the Ni-YSZ anode-supported cell during the 400 h test. Permanent changes were noted in the surface microstructure of the nickel particles in the cell anode. (C) 2009 Elsevier B.V. All rights reserved.