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Molecular or dissociative adsorption of water on clean and oxygen pre-covered Ni(111) surfaces

机译：分子或水的解离吸附清洁和氧气pre-covered倪(111)表面

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Water adsorption and dissociation on clean and oxygen pre-covered Ni(111) surfaces have been computed systematically by using density functional theory and ab initio atomistic thermodynamics. The adsorption of H, O and OH prefers 3-fold faced centered cubic hollow sites, and that of H2O prefers the top site. For (H2O)(n) aggregation, direct O-Ni interaction and H-bonding synergistically determine the adsorption energy, which is structure insensitive for large adsorbed clusters. At low coverage ( 0.25 ML), OH adsorbs perpendicularly and prefers remote distribution without H-bonding, and the OH saturation coverage should be 0.625 ML on the basis of H2O dissociative adsorption. The adsorption configuration for 4O (0.25 ML) prefers a p(2 x 2) structure, in agreement with the experiment, and the O saturation coverage should be 0.25 ML based on H2O dissociative adsorption. On the 0.25 ML O pre-covered Ni(111), H2O greatly prefers molecular adsorption [4O + 4H(2)O(s)] over dissociative adsorption [8OH] thermodynamically, and this is in agreement with the photoelectron spectroscopy results and in disagreement with previously and recently proposed results from single crystal adsorption calorimetry of D2O adsorption. It is noted that the computed bond energy and formation enthalpy of the supposed surface hydroxyls on the basis of the molecular adsorbed state [4O + 4H(2)O(s)] are much closer to the experimentally estimated results than those computed on the basis of the dissociatively adsorbed state [8OH]. Furthermore, the computed H2O desorption temperature on the basis of the molecular adsorbed state [4O + 4H(2)O(s)] is in excellent agreement with experimental results (284 vs. 275-300 K), while that from the dissociatively adsorbed state [8OH] differs strongly (197 K). All these support H2O molecular adsorption instead of dissociative adsorption, and this needs further experimental investigations and confirmations. The vibrational frequencies of 4O, 4O + 4H(2)O and 8OH adsorption configurations have been computed to aid experimental studies.
机译：水清洁和吸附和分离氧气pre-covered倪(111)表面通过使用密度计算系统功能理论和从头开始原子论的热力学。喜欢三倍面临心立方中空的网站,和水更喜欢网站顶部。(水)(n)聚合,直接O-Ni交互和H-bonding协同确定吸附能,结构不敏感对于大型吸附集群。0.25毫升),哦吸附垂直地,喜欢远程分布没有H-bonding,哦饱和度范围应该0.625毫升水解离吸附的基础。吸附配置4 o(0.25毫升)更喜欢p (2 x 2)结构,在协议实验,O饱和覆盖基于水解离吸附是0.25毫升。0.25毫升O pre-covered倪(111),水很大喜欢分子吸附[4 + 4 h (2) O (s)]在解离吸附(8哦)从热力学角度来看,这是同意光电子能谱结果与以前和最近的分歧提出了单晶吸附的结果D2O吸附量热法。能源和形成焓计算债券的表面羟基化的基础上分子吸附状态[4 + 4 h (2) O (s)]更接近实验估计结果比计算的基础上解离吸附状态(8哦)。计算出的水解吸温度上基础的分子吸附状态[4 o +4 h (2) O (s)]是在良好的协议实验结果(284和275 - 300 K)的解离吸附状态(8哦)不同强烈(197 K)。所有这些水的支持分子吸附而不是分离的吸附,这需要进一步的实验调查和确认。频率的4 O, O + 4 h (2) O和8哦吸附配置已计算的援助实验研究。

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