The interactions of water vapor with rare earth oxide surfaces play a major role in many important practical processes, such as heterogeneous catalysis and corrosion phenomena, especially for “real life” metals (metals with thin oxide overlays). Generally, these interactions take place by two different routes, a pure ionic dissociation, producing only hydroxyls, and a redox reaction, producing atomic hydrogen and an oxidic oxygen (or hydroxyl). In the presence of oxygen, however, the redox route is eliminated and only the pure ionic dissociation prevails. In the present study, the effect of oxygen on the dissociation of water vapor over GdO_1.5 was investigated experimentally and theoretically using density functional theory (DFT) calculations. The DFT calculations revealed that water vapor will follow the redox route only on nonstoichiometric, oxygen-deficient surfaces by producing a hydroxyl and a reduced H^-δ moiety that relaxes into an oxygen vacancy site. This moiety may diffuse into the oxide-metal interface (for oxide-coated metals) to form hydrides or it may associate on the oxide surface into H₂. In the presence of oxygen, the formation of H^-δ is prevented and therefore the formation of hydrides on oxide-coated metals is not expected. The experimental results are in agreement with the DFT analysis for the reaction of gadolinium (coated by its native oxide) with humidity to form gadolinium hydride islands on the surface. However, in the presence of oxygen, the extent of this reaction was very limited.

中文翻译：

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吸附氧对氧化Ga表面水离解的影响：密度泛函理论计算和实验结果

水蒸气与稀土氧化物表面的相互作用在许多重要的实际过程中起着重要作用，例如多相催化和腐蚀现象，特别是对于“现实生活中的”金属（带有薄氧化物覆盖层的金属）。通常，这些相互作用通过两种不同的途径发生：纯离子离解，仅生成羟基；氧化还原反应，生成原子氢和氧化性氧（或羟基）。然而，在氧的存在下，氧化还原途径被消除，仅纯离子离解占优势。在本研究中，氧气对GdO _1.5上水蒸气离解的影响使用密度泛函理论（DFT）进行实验和理论研究。DFT计算表明，水蒸气将仅通过在非化学计量的缺氧表面上遵循氧化还原途径，产生的羟基和还原的H- ^δ部分会松弛进入氧空位。该部分可能扩散到氧化物-金属界面（用于氧化物涂层的金属）中以形成氢化物，也可能在氧化物表面缔合成H ₂。在氧的存在下，H- ^δ的形成可以防止氧化氢，因此不能预期在氧化物涂层的金属上形成氢化物。实验结果与DFT分析一致（由其天然氧化物包覆的ado）与湿度在表面上形成氢化g岛的反应。然而，在氧气的存在下，该反应的程度非常有限。