Tetraammonium μ-ethylenediaminetetraacetato-1κ3 O,N,O′:2κ3 O′′,N′,O′′′-bis[trioxidotungstate(VI)] tetrahydrate

The title compound, (NH4)4[W2(C10H12N2O8)O6]·4H2O, was obtained from a mixture of tungstic acid, ammonia and ethylenediaminetetraacetic acid (H4edta) in a 2:4:1 ratio. The anion of the complex contains two WO3 units and one bridging edta4− ligand. Each central metal atom is tridentately coordinated by nitrogen and two carboxylate groups of the edta4− ligand, together with the three oxido ligands, producing a distorted octahedral coordination environment around each tungsten atom. The center of the carbon–carbon bond of the ethylene bridge represents a crystallographic inversion center. The crystal structure consists of a three-dimensional supramolecular framework built up by the dinuclear cations, the ammonium counter-ions and the solvent water molecules via hydrogen bonds of the N—H...O and O—H...O type.

Scanning Tunneling Microscopy Observation of WSe2 Surface

The surface structure of the WSe2 were studied using scanning tunneling microscopy. Exfoliation method in an ultra-high-vacuum chamber method is used to obtain a clean surface of WSe2 samples with atomically smooth terraces and multi-layer steps. Atomic-resolution images revealed two types of atomic defects of surface or near surface. These defects have been identified as the defects in the tungsten atom layer just below the topmost selenium layer.

The electronic structure of phosphotungstic (H3PW12O40) heteropolyacids modified by Fe2+ cation

In this paper the influence of substituting the tungsten atom with an iron ion in the primary structure of the phosphotungstic heteropolyacid with the Keggin anion structure was investigated. Characterization of the electronic structure of the modified heteropolyacid was performed using: population analysis according to NBO scheme, total (TDOS) and partial (PDOS) density of states spectra, energy and chemical character of frontier orbitals (HOMO / LUMO) and the size of the HOMO-LUMO band gap. Additionally, the mechanism of interaction between the Fe2+ with H2O molecule, acting as a chemical reaction medium, was investigated. Most cases showed a significant effect of the introduced transition metal ion (Fe2+) on the above-mentioned properties in relation to the nonmodified heteropolyacid H3PW12O40.

Ultrahigh Photocatalytic CO2 Reduction Efficiency by Single Metallic Atom Oxide on TiO2

Photocatalytic carbon dioxide (CO2) reduction is a sustainable and energy-consumption-free route to directly convert the greenhouse gas into chemicals. Given the vast amount of greenhouse gases, numerous efforts have been devoted to developing inorganic photocatalysts due to their stable, low-cost and environmental-friendly properties. However, more efficient titanium dioxide (TiO2) without noble metal or sacrifice/organic agent is highly desirable for CO2 reduction practical application, and it is also difficult and urgently in demand for TiO2 producing selectively valuable compounds, i.e. industrial chemicals and fuels. Here, we develop a novel “adatom at step” strategy via anchoring single tungsten atom oxide (STAO) site on intrinsic steps of classic TiO2 nanoparticles. The composition of single-sites can be controlled by tuning the ratio of adatom W5+ to neighboring Ti3+, resulting in significant CO2 reduction efficiency and selectively yield of carbon monoxide (CO) or methane (CH4) as main products. The W5+-dominated catalysts can achieve an ultrahigh photocatalytic CH4 production of 59.3 μmol/g/h, while the Ti3+-dominated catalysts can achieve a CO production of 181.4 μmol/g/h, which both exceed those of pristine TiO2 by more than one order of magnitude. The mechanism relies on the accurate control of atomic sites with high coverage and the subsequent excellent electron-hole separation along with favorable adsorption-desorption of intermediates on sites. This approach not only provides a novel strategy for inorganic catalytic single-sites with superior performance, but also identifies the rational design mechanisms of the efficient site with controllable production.

MOLECULAR ADSORPTION OF NO ON WmMon (m + n≤6) CLUSTERS

Geometric and electronic properties of nitric oxide adsorption on WmMon ([Formula: see text] 6) clusters have been systematically calculated by density functional theory (DFT) at the generalized gradient approximation (GGA) level for ground-state structures. NO molecule prefers top site with nitrogen-end bridging a tungsten atom for W[Formula: see text]Mo[Formula: see text] and W3Mo2 clusters. While NO tends to locate on the hollow site for WMo5, W2Mo4 and W3Mo3 clusters, and dissociation of NO molecule happens on W3Mo, N–O bond lengths expand in accordance with the variation of adsorption energy with the increasing number of tungsten atoms, originating from metal [Formula: see text] back-donation. Electron transfer occurs among 4d state of Mo, 5d state of W, 2p state of N and 2p state of O.

Single tungsten atom supported on N-doped graphyne as a high-performance electrocatalyst for nitrogen fixation under ambient conditions

A promising highly efficient and inexpensive W@N-doped graphyne electrocatalyst for N2 fixation has been predicted by first-principle calculation.

Tungsten-Embedded Graphene: Theoretical Study on a Potential High-Activity Catalyst toward CO Oxidation

The oxidation mechanism of CO on W-embedded graphene was investigated by M06-2X density functional theory. Two models of tungsten atom embedded in single and double vacancy (W-SV and W-DV) graphene sheets were considered. It was found that over W-SV-graphene and W-DV-graphene, the oxidation of CO prefers to Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanism, respectively. The two surfaces exhibit different catalytic activity during different reaction stages. The present results imply that W-embedded graphene is a promising catalyst for CO oxidation, which provides a useful reference for the design of a high-efficiency catalyst in detecting and removing of toxic gases.