Effect of PH_3 poisoning on a Ni-YSZ anode-supported solid oxide fuel cell under various operating conditions

摘要

The Ni-YSZ anode-supported solid oxide fuel cell (SOFC) can generate electrical power by using coal-derived syngas as the fuel. However, trace contamination of phosphine (PH_3) in the syngas can cause irreversible degradation in cell performance. A series of tests at l0ppm PH_3 in the fuel gas was carried out under a variety of operating conditions, viz, with/without electrochemical reaction in syngas and with/without H_2O in H_2 fuel at 750℃, 800℃ and 850℃ The poisoning effects were evaluated by both electrochemical methods and chemical analyses. The post-mortem analyses of the SOFC anode were performed by means of XRD, SEM/EDS, and XPS. The results show that the degradation rate is larger at the higher cell working temperature using syngas with PH_3 in a 200 h test though PH_3 is more reactive with Ni in the anode at lower working temperature and produces a secondary nickel phosphide (Ni_xP_y) phase. The dominant compositions of Ni_xP_y on the cell anode are Ni_5P_2 with the presence of H_2O, and Ni_(12)P_5 without the presence of H_2O. The production of Ni_xP_y can be generated on the cell anode using syngas or dry H_2 fuel with l0 ppm PH_3 contaminant. Further, the appearance of Ni_xP_y phases is independent of the electrochemical reactions in the cell.