Rapid degradation mechanism of Ni-CGO anode in low concentrations of H 2 at a high current density
Rapid degradation mechanism of Ni-CGO anode in low concentrations of H 2 at a high current density
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DOI：
10.1016/j.ijhydene.2011.04.046
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发表时间：
2011-07
期刊：
影响因子：
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通讯作者：
Gang Chen;G. Guan;S. Abliz;Yutaka Kasai;A. Abudula
中科院分区：
文献类型：
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作者：
Gang Chen;G. Guan;S. Abliz;Yutaka Kasai;A. Abudula
阴极支撑固体氧化物燃料电池（SOFC）由Ni-Gd0.2Ce0.8O1.9（Ni-CGO）阳极和Sc2O3掺杂ZrO2（ScSZ）电解质组成，在（La0.75Sr0.25）0.95MnO3−δ（LSM）+CGO阴极基底上，通过双重干燥压制和共烧方法制备。所制备的电池在纯氢气中的开路电压（OCV）在800°C时达到1.238，表明本方法制备的ScSZ电解质膜足够致密，电池处于良好的密封状态。通过逐渐加载系统电流来研究Ni-CGO阳极在低浓度H2中的性能退化现象。在机械损伤的情况下，Ni 的再氧化不是由 O2 引起的，应该是在高电流密度下发生的。根据EIS和SEM分析结果，推断Ni可以在低浓度H2的高电流密度下被氧离子氧化，并产生高p(H2O)/p(H2)比的H2O。在这种情况下，除非阳极首先在O2中燃烧然后在H2中还原，否则劣化电池的性能无法直接通过氢还原来再生。可能是由于Ni被H2O氧化而覆盖在NiO上的H2O分子阻碍了NiO被H2还原，可以通过O2燃烧将其移出。
Cathode-supported solid oxide fuel cell (SOFC) consisting of a Ni-Gd0.2Ce0.8O1.9(Ni-CGO) anode with a Sc2O3-doped ZrO2(ScSZ) electrolyte on a (La0.75Sr0.25)0.95MnO3−δ(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 H2reached 1.238 at 800 °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 H2was investigated by gradual loading of the system current. Re-oxidation of Ni, which was not caused by O2in 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 H2as well as by the produced H2O with a high p(H2O)/p(H2) 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 O2before reduced in H2. It is possible that H2O molecules covered on the NiO due to oxidation of Ni by H2O, which hindered NiO to be reduced by H2, could be moved out by O2burning.