Rapid degradation mechanism of Ni-CGO anode in low concentrations of H sub(2 at a high current density)

Cathode-supported solid oxide fuel cell (SOFC) consisting of a Ni-Gd sub(0.2Ce) sub(0).8O sub(1.9 (Ni-CGO) anode with a Sc) sub(2)O sub(3-doped ZrO) sub(2) (ScSZ) electrolyte on a (La sub(0.75Sr) sub(0).25) sub(0.95MnO) sub(3)-[delta] (LSM)+CGO cathode substrate was fabricated via a dual drying pressing followed by co-firing method. Open circuit voltage (OCV) of as-prepared cell in pure H sub(2 reached 1.238 at 800 [deg]C, indicating that the ScSZ electrolyte film prepared by the present method was dense enough and the cell was in a well-sealed state. Performance degradation phenomenon of Ni-CGO anode in low concentration of H) sub(2) was investigated by gradual loading of the system current. Re-oxidation of Ni, which was not caused by O sub(2 in the case of mechanical damage, was supposed to occur at a high current density. According to the EIS and SEM analysis results, it is inferred that the Ni could be oxidized by the oxygen ion at a high current density in low concentration of H) sub(2) as well as by the produced H sub(2O with a high p(H) sub(2)O)/p(H sub(2) ratio. In this case, the performance of the degraded cell was unable to be directly regenerated by hydrogen reduction unless the anode was firstly burnt in O) sub(2) before reduced in H sub(2. It is possible that H) sub(2)O molecules covered on the NiO due to oxidation of Ni by H sub(2O, which hindered NiO to be reduced by H) sub(2), could be moved out by O sub(2 burning.)