Engineering Bimodal Oxygen Vacancies and Pt to Boost the Activity Toward Water Dissociation

Mullite is an aluminium-silicate mineral of current interest since it is a potential candidate for high temperature applications in the ceramic materials field.In the present work, conditions under which the structure of mullite can be optimally imaged by means of High Resolution Electron Microscopy (HREM) have been investigated. Special reference is made to the Atomic Resolution Microscope at Berkeley which allows real space information up to ≈ 0.17 nm to be directly transferred; numerous multislice calculations (conducted with the CEMPAS programs) as well as extensive experimental through-focus series taken from a commercial “3:2” mullite at 800 kV clearly show that a resolution of at least 0.19 nm is required if one wants to get a straightforward confirmation of atomic models of mullite, which is known to undergo non-stoichiometry associated with the presence of oxygen vacancies.Indeed the composition of mullite ranges from approximatively 3Al2O3-2SiO2 (referred here as 3:2-mullite) to 2Al2O3-1SiO2, and its structure is still the subject of refinements (see, for example, refs. 4, 5, 6).

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Investigation of Some Characterizations of Black TiO\(_2\) Nanotubes Via Spectroscopic Methods

Communications in Physics ◽

10.15625/0868-3166/29/2/13762 ◽

2019 ◽

Vol 29 (2) ◽

pp. 189 ◽

Cited By ~ 1

Author(s):

Tho Truong Nguyen ◽

Thi Minh Cao ◽

Hieu Van Le ◽

Viet Van Pham

Keyword(s):

Water Splitting ◽

Oxygen Vacancies ◽

Light Response ◽

Nanotube Arrays ◽

Spectroscopic Methods ◽

Visible Light Response ◽

Uv Visible ◽

Visible Reflectance ◽

Splitting Effect ◽

Anodization Method

The black TiO\(_2\) with substantial Ti\(^3+\) and oxygen vacancies exhibit an excellent photoelectrochemical water-splitting performance due to the improved charge transport the extended visible light response. In this study, black TiO\(_2\) nanotube arrays synthesized by the anodization method, and then, they have been investigated some characterizations by spectroscopic methods such as UV-visible reflectance (UV-vis DRS), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and photoluminescence spectrum. The results showed that some highlighted properties of the black TiO2 nanotube arrays and they could apply for water-splitting effect.

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A First-Principles Computational Comparison of the Aqueous Anatase TiO2 (001) Interface and the Disordered, Fluorinated TiO2 Interface

10.26434/chemrxiv.7076816.v1 ◽

2018 ◽

Author(s):

Kyle Reeves ◽

Damien Dambournet ◽

Christel Laberty-Robert ◽

Rodolphe Vuilleumier ◽

Mathieu Salanne

Keyword(s):

Density Of States ◽

Density Functional ◽

Water Dissociation ◽

Water Molecules ◽

Chemical Doping ◽

Charge Balance ◽

Functional Theory ◽

Adsorption Of Water ◽

Properties Of Materials ◽

Computational Comparison

Chemical doping and other surface modifications have been used to engineer the bulk properties of materials, but their influence on the surface structure and consequently the surface chemistry are often unknown. Previous work has been successful in fluorinating anatase TiO2 with charge balance achieved via the introduction of Ti vacancies rather than the reduction of Ti. Our work here investigates the interface between this fluorinated titanate with cationic vacancies and a monolayer of water via density functional theory based molecular dynamics. We compute the projected density of states for only those atoms at the interface and for those states that fall within 1eV of the Fermi energy for various steps throughout the simulation, and we determine that the variation in this representation of the density of states serves as a reasonable tool to anticipate where surfaces are most likely to be reactive. In particular, we conclude that water dissociation at the surface is the main mechanism that influences the anatase (001) surface whereas the change in the density of states at the surface of the fluorinated structure is influenced primarily through the adsorption of water molecules at the surface.

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A First-Principles Computational Comparison of the Aqueous Anatase TiO2 (001) Interface and the Disordered, Fluorinated TiO2 Interface

10.26434/chemrxiv.7076816 ◽

2018 ◽

Author(s):

Kyle Reeves ◽

Damien Dambournet ◽

Christel Laberty-Robert ◽

Rodolphe Vuilleumier ◽

Mathieu Salanne

Keyword(s):

Density Of States ◽

Density Functional ◽

Water Dissociation ◽

Water Molecules ◽

Chemical Doping ◽

Charge Balance ◽

Functional Theory ◽

Adsorption Of Water ◽

Properties Of Materials ◽

Computational Comparison

Chemical doping and other surface modifications have been used to engineer the bulk properties of materials, but their influence on the surface structure and consequently the surface chemistry are often unknown. Previous work has been successful in fluorinating anatase TiO2 with charge balance achieved via the introduction of Ti vacancies rather than the reduction of Ti. Our work here investigates the interface between this fluorinated titanate with cationic vacancies and a monolayer of water via density functional theory based molecular dynamics. We compute the projected density of states for only those atoms at the interface and for those states that fall within 1eV of the Fermi energy for various steps throughout the simulation, and we determine that the variation in this representation of the density of states serves as a reasonable tool to anticipate where surfaces are most likely to be reactive. In particular, we conclude that water dissociation at the surface is the main mechanism that influences the anatase (001) surface whereas the change in the density of states at the surface of the fluorinated structure is influenced primarily through the adsorption of water molecules at the surface.

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