Hydroxy1 driven reconstruction of the polar NiO(111) surface

Rohr, F.; Wirth, K.; Libuda, Jörg; Cappus, D.; Bäumer, Marcus; Freund, Hans‐Joachim

doi:10.1016/0039-6028(94)90529-0

Cited by 166 publications

(116 citation statements)

References 9 publications

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“…34 Since the NiO(111) films were experimentally determined to be very thin, i. e., only a few atomic layers thick, a metastable character of the NiO(111) orientation has been postulated, in agreement with the growth of the thermodynamically stable, unpolar NiO(001) face at 500 K, i. e., at sufficiently high temperature. 33 In other studies, the stability of the NiO(111)-(1×1) surface has been related to the adsorption of hydroxyl species 32,35 that prevent the surface from undergoing a so-called "octopolar" (2×2) reconstruction leading to a compensation of the surface dipole.…”

Section: Resultsmentioning

confidence: 99%

“…Since hydroxyl species are easily removed by annealing to 600 K, 35 this scenario would provide an alternative explanation for the stability of the (1×1) phase at room temperature and the preferential growth of NiO(001) above 500 K. 32 Yet, it has still remained unclear whether the driving force for the (2×2) reconstruction at high temperature would be the same for thin 38 as well as moderately thick NiO(111) films-a question raised almost twenty years ago.…”

Section: 37mentioning

confidence: 99%

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Self-limited oxide formation in Ni(111) oxidation

et al. 2011

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The oxidation of the Ni(111) surface is studied experimentally with low energy electron microscopy and theoretically by calculating the electron reflectivity for realistic models of the NiO/Ni(111) surface with an ab initio scattering theory. Oxygen exposure at 300 K under ultrahigh-vacuum conditions leads to the formation of a continuous NiO(111)-like film consisting of nanosized domains. At 750 K, we observe the formation of a nano-heterogeneous film composed primarily of NiO (111) surface oxide nuclei, which exhibit virtually the same energy-dependent reflectivity as in the case of 300 K and which are separated by oxygen-free Ni(111) terraces. The scattering theory explains the observed normal incidence reflectivity R(E) of both the clean and the oxidized Ni(111) surface. At low energies R(E) of the oxidized surface is determined by a forbidden gap in the k = 0 projected energy spectrum of the bulk NiO crystal. However, for both low and high temperature oxidation a rapid decrease of the reflectivity in approaching zero kinetic energy is experimentally observed. This feature is shown to characterize the thickness of the oxide layer, suggesting an average oxide thickness of two NiO layers.

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Section: Resultsmentioning

confidence: 99%

Section: 37mentioning

confidence: 99%

Self-limited oxide formation in Ni(111) oxidation

et al. 2011

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“…[1]). Most of these studies indicate a surface stabilization by an octopolar p(2× 2) reconstruction [2][3][4] or by hydroxylation [5,6]. Yet, the situation for metal-supported Ni-oxide films with a thickness of only few atomic layers, which are often referred to as oxide nanolayers, is less clear.…”

Section: Introductionmentioning

confidence: 98%

Surface structure of nickel oxide layers on a Rh(111) surface

et al. 2013

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The formation of nickel oxide nanolayers by oxidizing Ni overlayers on Rh(111) has been investigated and their structures are reported as a function of the nickel coverage and oxygen pressure. Scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and diffraction (XPD), and high-resolution electron energy loss spectroscopy (HREELS) have been applied to characterize the structure and stoichiometry of the nickel oxide nanolayers. Several different phases have been observed depending on the strain state of the metallic Ni overlayers. For the pseudomorphic Ni monolayer, two distinctly different oxide phases with (6 ×1)-Ni 5 O 5 and (2√3×2)-Ni 8 O 10 structures have been identified at oxygen-poor (p=5×10 −8 mbar) and oxygen-rich (p≥1×10 −6 mbar) conditions, respectively. Above one monolayer, where the Ni layers are relaxed, bulk-like NiO(100) films form at the O-rich conditions, whereas chemisorbed-type p(2 ×2)O\Ni(111) layers develop in the O-poor regime. X-ray photoelectron diffraction analysis has provided additional insight into the relaxation mechanism and the detailed atomic structure of the Ni-oxide nanolayers.

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“…Polar surface planes can be stabilized by hydroxylation, because it reduces excess surface charge and, therefore, the electrostatic surface dipole moment (see Section 2.8). Upon dehydroxylation, these surface planes reconstruct, in order to establish a more stable configuration [64][65][66].…”

Section: Adsorption Processmentioning

confidence: 99%

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Weiß

Ranke

2002

Progress in Surface Science

584

610

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Metal-oxide based catalysts are used for many important synthesis reactions in the chemical industry. A better understanding of the catalyst operation can be achieved by studying elemantary reaction steps on well-defined model catalyst systems. For the dehydrogenation of ethylbenzene to styrene in the presence of steam both unpromoted and potassium promoted iron-oxide catalysts are active. Here we review the work done over unpromoted single-crystalline FeO(111), Fe 3 O 4 (111) and α-Fe 2 O 3 (0001) films grown epitaxially on Pt(111) substrates. Their geometric and electronic surface structures were characterized by STM, LEED, electron microscopy and electron spectroscopic techniques. In an integrative approach, the interaction of water, ethylbenzene and styrene with these films was investigated mainly by thermal desorption and photoelectron emission spectroscopy. The adsorptiondesorption energetics and kinetics depend on the oxide surface terminations and are correlated to the electronic structures and acid-base properties of the corresponding oxide phases, which reveal insight into the nature of the active sites and into the catalytic function of semiconducting oxides in general. Catalytic studies, using a batch reactor arrangement at high gas pressures and post reaction surface analysis, showed that only α-Fe 2 O 3 (0001) containing surface defects is catalytically active, whereas Fe 3 O 4 (111) is always inactive. This can be related to the elementary adsorption and desorption properties observed in ultrahigh vacuum, which indicates that the surface chemical properties of the iron-oxide films do not change significantly across the "pressure-gap". A model is proposed according to which the active site involves a regular acidic surface sites and a defect site next to it. The results on metal-oxide surface chemistry also have implications for other fields, such as environmental science, biophysics and chemical sensors.-2 -"2kyEi9FYSQjBVrZxIPQ.FHIAC_WRa02_review.doc", Datum: 19.02.03

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Hydroxy1 driven reconstruction of the polar NiO(111) surface

Cited by 166 publications

References 9 publications

Self-limited oxide formation in Ni(111) oxidation

Self-limited oxide formation in Ni(111) oxidation

Surface structure of nickel oxide layers on a Rh(111) surface

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

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