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Deactivation and Recovery of Ni-YSZ Anode in H2 Fuel Containing H2S

2005; Electrochemical Society; Volume: 2005-07; Issue: 1 Linguagem: Inglês

10.1149/200507.1275pv

2576-1579

Shen Xia,

Electrocatalysts for Energy Conversion

The degradation of Ni-YSZ composite anodes in a single solid oxide fuel cell (SOFC) running on humidified H2 containing 10 ppm H2S, at 800°C, has been investigated, both at the open circuit potential (OCP) and under load. With exposure to H2S at the OCP, the series resistance (electrolyte plus interfacial contacts) and especially the polarization resistance increase with time. Anode degradation is enhanced when exposure occurs under a load, and the higher the current density, the more rapid the loss of performance, without reaching a steady-state. Partial or full recovery of the H2S-poisoned Ni-YSZ anode, determined by the extent of lowering of the series and polarization resistance, was achieved by exposure to pure H2, N2 or air at the OCP. Greater than 90% recovery was obtained in N2 or air, while only ~75 % recovery could be achieved in H2. Overall, the results indicate that the reversible component of H2S poisoning is caused by the blocking of the active Ni-YSZ sites by adsorbed sulfur or H2S, while the small, irreversible component may be due to the formation of a Ni-S compound in some areas within the anode structure.