Abstract In various technological applications (solid oxide fuel cells, heterogeneous catalysis) ceria based mixed oxides are in contact with alumina used as support or additive. It is thus important to gain knowledge on the possible interactions between the mixed oxide and the alumina at temperatures and atmospheres, corresponding to real processing or working conditions. In this work, structure and chemical stability of Ce0.5Gd0.5O1.75 nanoparticles supported on a high surface γ-Al2O3 were studied in oxidizing and reducing atmosphere by XRD, TEM, SEM-EDS, STEM-EDS, Raman spectroscopy and H2-TPR. Application of a reverse microemulsion method enabled the synthesis of highly Gd-doped, homogeneous ceria particles with mean size ∼2 nm, ideal for the studies on effect of the interaction with Al2O3 support on chemical and structural stability od doped ceria. Poor tolerance of Ce0.5Gd0.5O1.75 nanoparticles to sintering is greatly improved by their dispersion on a high surface alumina support. In oxidizing atmosphere the particles were chemically stable on the alumina up to 1100 °C, undergoing little sintering with increase of the mean crystallite size to 7 nm. In hydrogen atmosphere, the stability is limited by complex, chemical interaction between Gd doped ceria and Al2O3 support, which has been studied in detail for the first time. Ce0.5Gd0.5O1.75 nanoparticles started to spread over the support at 600 °C into a nanometer thick amorphous layer, and at 900 °C crystallized into a mixed (Gd,Ce)4Al2O9 aluminate. The (Gd,Ce)4Al2O9 aluminate, which is an intermediate phase at the low ceria/alumina molar ratio used, decomposed at 1000 °C into tetragonal CeAlO3 and hexagonal GdAlO3. When deposited on Al2O3, Ce0.5Gd0.5O1.75 nanoparticles showed much improved reducibility, especially in low-temperature range (300–600 °C). This effect is further enhanced by the spreading of ceria over Al2O3 occurring during treatment in hydrogen atmosphere at elevated temperature. The nanocrystalline Ce-Gd-O/Al2O3 system prepared by the impregnation with an aqueous solution of Ce and Gd nitrates appeared to be chemically inhomogeneous and less stable in both oxidizing and reducing atmospheres.d

中文翻译：

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纳米晶 Ce-Gd 混合氧化物在 Al2O3 载体上的稳定性

摘要 在各种技术应用（固体氧化物燃料电池、多相催化）中，基于氧化铈的混合氧化物与用作载体或添加剂的氧化铝接触。因此，重要的是要了解混合氧化物和氧化铝在温度和气氛下可能发生的相互作用，这与实际加工或工作条件相对应。在这项工作中，通过XRD、TEM、SEM-EDS、STEM-EDS、拉曼光谱和H2-在氧化和还原气氛中研究了负载在高表面γ-Al2O3上的Ce0.5Gd0.5O1.75纳米颗粒的结构和化学稳定性。 TPR。反微乳液法的应用能够合成平均粒径约 2 nm 的高 Gd 掺杂的均质二氧化铈颗粒，非常适合研究与 Al2O3 载体的相互作用对掺杂氧化铈的化学和结构稳定性的影响。Ce0.5Gd0.5O1.75 纳米颗粒对烧结的耐受性差通过它们在高表面氧化铝载体上的分散而得到极大改善。在氧化气氛中，颗粒在氧化铝上的化学稳定性高达 1100 °C，随着平均微晶尺寸增加到 7 nm，几乎不会发生烧结。在氢气氛中，稳定性受到 Gd 掺杂的氧化铈和 Al2O3 载体之间复杂的化学相互作用的限制，这是首次详细研究的。Ce0.5Gd0.5O1.75 纳米粒子在 600°C 开始在载体上扩散成纳米厚的非晶层，并在 900°C 结晶成混合的 (Gd,Ce)4Al2O9 铝酸盐。(Gd,Ce)4Al2O9 铝酸盐，它是使用低氧化铈/氧化铝摩尔比的中间相，在 1000 °C 下分解成四方 CeAlO3 和六方 GdAlO3。当沉积在 Al2O3 上时，Ce0.5Gd0.5O1.75 纳米颗粒显示出大大提高的还原性，尤其是在低温范围 (300–600 °C)。在高温氢气气氛中处理过程中，二氧化铈在 Al2O3 上的扩散进一步增强了这种效果。通过用 Ce 和 Gd 硝酸盐水溶液浸渍制备的纳米晶 Ce-Gd-O/Al2O3 体系在氧化和还原气氛中似乎化学不​​均匀且稳定性较差。特别是在低温范围内（300–600 °C）。在高温氢气气氛中处理过程中，二氧化铈在 Al2O3 上的扩散进一步增强了这种效果。通过用 Ce 和 Gd 硝酸盐水溶液浸渍制备的纳米晶 Ce-Gd-O/Al2O3 体系在氧化和还原气氛中似乎化学不​​均匀且稳定性较差。特别是在低温范围内（300–600 °C）。在高温氢气气氛中处理过程中，二氧化铈在 Al2O3 上的扩散进一步增强了这种效果。通过用 Ce 和 Gd 硝酸盐水溶液浸渍制备的纳米晶 Ce-Gd-O/Al2O3 体系在氧化和还原气氛中似乎化学不​​均匀且稳定性较差。