scholarly journals Femtosecond visualization of oxygen vacancies in metal oxides

2020 ◽  
Vol 6 (10) ◽  
pp. eaax9427 ◽  
Author(s):  
Xinping Zhang ◽  
Fawei Tang ◽  
Meng Wang ◽  
Wangbin Zhan ◽  
Huaxin Hu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Oxygen Vacancy ◽  
Metal Oxides ◽  
Oxygen Vacancies ◽  
Time Resolved ◽  
Tungsten Oxides ◽  
Structure Of Metal ◽  
Evolution Dynamics ◽  
Spatial Locations

Oxygen vacancies often determine the electronic structure of metal oxides, but existing techniques cannot distinguish the oxygen-vacancy sites in the crystal structure. We report here that time-resolved optical spectroscopy can solve this challenge and determine the spatial locations of oxygen vacancies. Using tungsten oxides as examples, we identified the true oxygen-vacancy sites in WO2.9 and WO2.72, typical derivatives of WO3 and determined their fingerprint optoelectronic features. We find that a metastable band with a three-stage evolution dynamics of the excited states is present in WO2.9 but is absent in WO2.72. By comparison with model bandstructure calculations, this enables determination of the most closely neighbored oxygen-vacancy pairs in the crystal structure of WO2.72, for which two oxygen vacancies are ortho-positioned to a single W atom as a sole configuration among all O─W bonds. These findings verify the existence of preference rules of oxygen vacancies in metal oxides.

Controlled oxygen vacancy engineering on In2O3−x/CeO2−y nanotubes for highly selective and efficient electrocatalytic nitrogen reduction

2020 ◽  
Vol 7 (19) ◽  
pp. 3609-3619
Author(s):  
Zengyao Wang ◽  
Jianfeng Shen ◽  
Wenzhi Fu ◽  
Jiangwen Liao ◽  
Juncai Dong ◽  
...  
Keyword(s):  
Transition Metal ◽  
Oxygen Vacancy ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Oxygen Vacancies ◽  
Reduction Reaction ◽  
Nitrogen Reduction

Introducing and adjusting the oxygen vacancies (VO) of transition metal oxides has been proposed as a significant and effective way to tackle the sluggish nitrogen reduction reaction (NRR) in the electrocatalysis process.

scholarly journals Quantitative analysis of time-resolved RHEED during growth of vertical nanowires

Nanoscale ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 5471-5482
Author(s):  
Julian Jakob ◽  
Philipp Schroth ◽  
Ludwig Feigl ◽  
Daniel Hauck ◽  
Ullrich Pietsch ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Quantitative Analysis ◽  
Time Resolved

In situ RHEED enables a height-resolved determination of the crystal structure of vertical nanowires via self-shadowing and ensemble shadowing.

scholarly journals Facile Strategy for Synthesizing Non-Stoichiometric Monoclinic Structured Tungsten Trioxide (WO3−x) with Plasma Resonance Absorption and Enhanced Photocatalytic Activity

Nanomaterials ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 553 ◽  
Author(s):  
Shihao Chen ◽  
Yang Xiao ◽  
Wei Xie ◽  
Yinhai Wang ◽  
Zhengfa Hu ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Oxygen Vacancy ◽  
Metal Oxides ◽  
Tungsten Trioxide ◽  
Oxygen Vacancies ◽  
Near Infrared ◽  
Treatment Method ◽  
Hydrogen Treatment ◽  
Vacancy Defects ◽  
And Control

Oxygen vacancy defects play an important role in improving the light-capturing and photocatalytic activity of tungsten trioxide (WO3). However, the hydrogen treatment method that is commonly used to introduce oxygen vacancies is expensive and dangerous. Therefore, the introduction and control of oxygen vacancy defects in WO3 remains a challenge. Here, we demonstrated that oxygen vacancies could be successfully introduced into WO3−x while using a facile method through low temperature annealing in alcohol. The obtained WO3−x samples with optimal oxygen vacancies showed strong absorption of light, extending from the ultraviolet to the visible and near-infrared regions, and exhibits strong plasmon resonance from 400–1200 nm peaking at approximately 800 nm. When compared to pristine WO3, the photocatalytic activity of WO3−x was greatly improved in the ultraviolet and visible regions. This study provides a simple and efficient method to generate oxygen vacancies in WO3 for photocatalysis, which may be applied in the photoelectrochemical, electrochromic, and photochromic fields. Because oxygen vacancy is a common characteristic of metal oxides, the findings that are presented herein may be extended to other metal oxides.

Controllable construction of oxygen vacancies by anaerobic catalytic combustion of dichloromethane over metal oxides for enhanced solar-to-hydrogen conversion

2019 ◽  
Vol 3 (10) ◽  
pp. 2742-2752 ◽  
Author(s):  
Sufen Zhang ◽  
Jianni Liu ◽  
Xiaoyang Dong ◽  
Xiaoxia Jia ◽  
Ziwei Gao ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Metal Oxides ◽  
Catalytic Combustion ◽  
Oxygen Vacancies ◽  
Combustion Method

A facile anaerobic catalytic combustion method is used for controllable oxygen vacancy construction of metal oxides for enhanced solar-to-hydrogen conversion.

Sulfur-doping tuning oxygen vacancies in ultrathin 2D Ni–V mixed metal oxides for exceptional oxidase mimic and antibacterial applications

2021 ◽  
Author(s):  
Yi Wang ◽  
Chao Chen ◽  
Dun Zhang
Keyword(s):  
Antibacterial Activity ◽  
Oxygen Vacancy ◽  
Metal Oxides ◽  
Oxygen Vacancies ◽  
Mixed Metal Oxides ◽  
Mixed Metal ◽  
Low Level ◽  
Sulfur Doping

Sulfur-doping ultrathin 2D Ni–V MMO nanosheets can be derived from LDHs. The obtained 2NiV-S-400 with rich oxygen vacancy exhibits the best OXD/POD-like and antibacterial activity by generating of ˙OH and ˙O2− radical with low level of H2O2.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

The protonation of the ethylenediphosphinetetraacetate anion and the crystal structure of the bis (hydrogen bromide) of ethylenediphosphinetetraacetic acid

1981 ◽  
Vol 46 (12) ◽  
pp. 3063-3073 ◽  
Author(s):  
Jana Podlahová ◽  
Bohumil Kratochvíl ◽  
Vratislav Langer ◽  
Josef Šilha ◽  
Jaroslav Podlaha
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Structure Determination ◽  
Free Acid ◽  
Hydrogen Bromide ◽  
Carboxyl Groups ◽  
Spectroscopic Methods ◽  
X Ray ◽  
Partial Formation

The equilibria and mechanism of addition of protons to the ethylenediphosphinetetraacetate anion (L4-) were studied in solution by the UV, IR, 1H and 31P NMR spectroscopic methods. A total of six protons can be bonded to the anion. They are added stepwise, first with partial formation of zwitterions containing P-H bonds, which then dissociate with formation of the free acid, H4L, where all four protons are bonded in carboxyl groups. The formation of zwitterions is strongly dependent on the concentration. In the final stage, the acid bonds two additional protons to form the bis-phosphonium cation, H6L2+. A number of isostructural salts containing this cation, H4L.2 HX (X = Cl, Br, I), have been prepared. The X-ray crystal structure determination of the bromide confirmed the expected arrangement. The bromide crystals are monoclinic, a = 578.2, b = 1 425.0, c = 1 046.7 pm, β = 103.07° with a space group of P21/c, Z = 2. The final R factor was 0.059 based on 1 109 observed reflections. The structure consists of H6L2+ cations containing protons bonded to phosphorus atoms (P-H distance 134 pm) and of bromide anions, located in gaps which are also sufficiently large for I- anions in the isostructural iodide. The interbonding of phosphonium cations proceeds through hydrogen bonds, C-OH...O=C, in which the O...O distance is 275.3 pm.

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