Theoretical Studies on the Mechanism of deNOx Process in Cu–Zn Bimetallic System—Comparison of FAU and MFI Zeolites

In the present study we propose a more promising catalyst for the deNOx process to eliminate harmful nitrogen oxides from the environment. The study was performed with a computer calculation using density functional theory (DFT) based on an ab initio method. Two zeolite catalysts, FAU and MFI, were selected with additional Cu–O–Zn bimetallic dimer adsorbed inside the pores of both zeolites. Based on the analysis of preliminary studies, the most probable way of co-adsorption of nitric oxide and ammonia was selected, which became the initial configuration for the reaction mechanism. Two types of mechanisms were proposed: with hydroxyl groups on a bridged position of the dimer or a hydroxyl group on one of the metal atoms of the dimer. Based on the results, it was determined that the FAU zeolite with a bimetallic dimer and an OH group on the zinc atom was the most efficient configuration with a relatively low energy barrier. The real advantage of the Cu–Zn system over FAU and MFI in hydrothermal conditions has been demonstrated in comparison to a conventional Cu–Cu catalyst.

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Activation of the Hydrogen-Terminated Diamond [100] by Hydrogen Atoms and Hydroxyl Groups

Materials Science Forum ◽

10.4028/www.scientific.net/msf.996.151 ◽

2020 ◽

Vol 996 ◽

pp. 151-156

Author(s):

Xiao Gang Jian ◽

Ji Bo Hu ◽

Xin Huang ◽

Pei Kang Yang ◽

Jun Peng Wang

Keyword(s):

Hydrogen Atom ◽

Low Temperature ◽

Density Functional ◽

Diamond Surface ◽

Hydroxyl Group ◽

Hydroxyl Groups ◽

Hydrogen Atoms ◽

Activation Rate ◽

Limiting Stage ◽

Rate Limiting

The process of producing active vacancies on a hydrogen-terminated diamond surface is the most important rate-limiting stage in CH4/H2 and CH4/H2/CO2 atmospheres. Hydrogen atom and the hydroxyl group can bone to the hydrogen atom on the diamond surface and create an active vacancy. Density functional theory (DFT) was used to study the extraction reaction by two reactants both hydrogen atom and the hydroxyl group. The result indicated that the hydroxyl group could reduce the energy required for diamond surface activation. What is more, the activation rate of the surface by the hydroxyl group was livelier at low temperature, while the activation rate of the hydrogen atom predicts on the contrary. The scanning electron microscope (SEM) and Raman spectra demonstrated that the introduction of CO2 in the CH4/H2 atmosphere could reduce the deposition temperature and raise the deposition rate at low temperature.

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Hydrolysis Mechanism of Bismuth in Chlorine Salt System Calculated by Density Functional Method

Revista de Chimie ◽

10.37358/rc.20.6.8182 ◽

2020 ◽

Vol 71 (6) ◽

pp. 178-193

Author(s):

Liao Chunfa ◽

Xu Zhenxin ◽

Zou Jianbai ◽

Jiang Pinguoo

Keyword(s):

Density Of States ◽

Density Functional ◽

Energy Gap ◽

Density Functional Method ◽

Covalent Bond ◽

Salt System ◽

Hydroxyl Group ◽

Partial Density ◽

Hydroxyl Groups ◽

Total Density

Based on the density functional theory, this paper presents the calculated cellular electronic properties of BiCl3, BiOCl and Bi3O4Cl, including unit cell energy, band structure, total density of states, partial density of states, Mulliken population, overlapping population, etc. Combined with the thermodynamic analysis of Bi3+ hydrolysis process in chlorine salt system, the conversion mechanism of oxychloride bond in BiCl3 to form BiOCl and Bi3O4Cl by hydrolysis, ethanololysis and ethylene glycol alcohololysis was obtained by infrared spectroscopy. The results indicate that the energy of Bi3O4Cl cell system was lower than that of BiOCl cell, indicating that the structure of Bi3O4Cl was more stable. From the analysis of bond fluctuation, the electron nonlocality in BiOCl belt was relatively large, and the orbital expansibility was strong; thus the structure of BiOCl was relatively active. The state density map of Bi3O4Cl had the widest energy gap, i.e., the covalent bond between Bi3O4Cl was stronger than BiOCl. Therefore, the hydrolysis of BiCl3 would preferentially generate Bi3O4Cl with a more stable structure. The number of charge arrangement, overlapping population and infrared spectrogram indicate that there were two basic ways in the hydrolysis and alcoholysis of BiCl3. Firstly, two chlorine atoms in BiCl3 were replaced by hydroxyl groups ionized by water and alcohol to form [Bi(OH)2Cl] monomer, and BiOCl and Bi3O4Cl were formed by intra-molecular dehydration or inter-molecular dehydration. The other way was that the Bi atom directly reacted with the OH ionized by water and alcohol to form the [Bi-OH] monomer, and the Cl atom replaced the H atom on the hydroxyl group in the [Bi-OH] monomer to further form BiOCl and Bi3O4Cl.

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Investigation of CO Adsorption on Hydroxyapatite (001) Surface Using Density Functional Theory

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1028.215 ◽

2021 ◽

Vol 1028 ◽

pp. 215-220

Author(s):

Liza Saharani Hamzah ◽

Juliandri ◽

Atiek Rostika Noviyanti ◽

Budi Adiperdana ◽

Risdiana

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Energy Surface ◽

Exchange Process ◽

Co Adsorption ◽

Hydroxyl Group ◽

Functional Theory ◽

Ion Exchange Process ◽

Phosphate Mineral ◽

Co Gas

Hydroxyapatite (HA) is a phosphate mineral with the chemical formula of Ca10(PO4)6(OH)2. The presence of pores in HA allows easy interaction with other compounds, so it can be used to detect the CO gas. Other than that, the hydroxyl group in hydroxyapatite allows the ion exchange process, a significant reaction in a gas sensor. The interaction of hydroxyapatite with CO gas has been studied using density functional theory. The HA adsorption potential energy surface was investigated using slab model with (001) expansion and 10 Å vacuum. CO gas kept fixed 1.0 Å above the HA surface and traced along the surface with grid 10×10. The result shows that the surface is divided into two main potentials that more likely and unlikely for CO to stay. The CO gas is most likely to stay between two oxygen from (PO3) tetrahedral that pointing down.

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Effects of Hydroxyl Group on the Interaction of Carboxylated Flavonoid Derivatives with S. Cerevisiae α-Glucosidase

Current Computer - Aided Drug Design ◽

10.2174/1573409914666181022142553 ◽

2020 ◽

Vol 16 (1) ◽

pp. 31-44

Author(s):

Huining Lu ◽

Yanjiao Qi ◽

Yaming Zhao ◽

Nengzhi Jin

Keyword(s):

Hydrogen Atom ◽

Charge Density ◽

Density Functional ◽

Noncovalent Interactions ◽

Hydroxyl Group ◽

Hydroxyl Groups ◽

Binding Affinities ◽

Functional Theory ◽

Density Analysis ◽

Hydroxyl Hydrogen

Introduction: Carboxyalkyl flavonoids derivatives are considered as effective inhibitors in reducing post-prandial hyperglycaemia. Methods: Combined with Density Functional Theory (DFT) and the theory of Atoms in Molecules (AIM), molecular docking and charge density analysis are carried out to understand the molecular flexibility, charge density distribution and the electrostatic properties of these carboxyalkyl derivatives. Results: Results show that the electron density of the chemical bond C14-O17 on B ring of molecule II increases while O17-H18 decreases at the active site, suggesting the existence of weak noncovalent interactions, most prominent of which are H-bonding and electrostatic interaction. When hydroxyl groups are introduced, the highest positive electrostatic potentials are distributed near the B ring hydroxyl hydrogen atom and the carboxyl hydrogen atom on the A ring. It was reported that quercetin has a considerably inhibitory activity to S. cerevisiae α-glucosidase, from the binding affinities, it is suggested that the position and number of hydroxyl groups on the B and C rings are also pivotal to the hypoglycemic activity when the long carboxyalkyl group is introduced into the A ring. Conclusion: It is concluded that the presence of three well-defined zones in the structure, both hydrophobicity alkyl, hydrophilicity carboxyl and hydroxyl groups are necessary.

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Chemical Stability of 2D-Nanostructured WO3 in Hydrogen Sensing Under Varied Operation Temperature

NANO ◽

10.1142/s1793292016500922 ◽

2016 ◽

Vol 11 (08) ◽

pp. 1650092 ◽

Cited By ~ 2

Author(s):

Taisheng Yang ◽

Hui Tian ◽

Yue Zhang ◽

Chen Li

Keyword(s):

Water Molecule ◽

Chemical Stability ◽

Density Functional ◽

Stable State ◽

Hydroxyl Group ◽

Hydroxyl Groups ◽

Surface Hydroxyl ◽

Hydrogen Sensing ◽

Operation Temperature ◽

Surface Hydroxyl Groups

Nanostructured metal oxide-based resistive-type gas sensors are of high research interest. Chemical stability is the most critical issue due to the surface electron species and density. In the present paper, 2D-nanostructured WO3 was prepared and characterized, and a WO3-based sensor was fabricated and analyzed. The results showed that the synthesized WO3 material exhibited nanosheet structure, and during hydrogen sensing testing, the current baseline shifted with various tendencies, even completely opposite directions under different operation temperatures. The chemistry analysis results indicated that water molecule and hydroxyl group were formed under low operation temperature but further oxidation occurred at higher temperatures. The adsorption of H2 on oxygen terminated WO3(0 0 1) surfaces by density functional theory (DFT) method indicated that a water molecule formed by adsorption of a hydrogen molecule at the O site with the most thermodynamically stable state, and two surface hydroxyl groups formed by dissociative adsorption with a thermodynamically less stable state. The water molecule and surface hydroxyl groups increased the conductivity of the WO3 film while that was decreased as the oxidation occurred.

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Investigations of the Effect of H2 in CO Oxidation over Ceria Catalysts

Catalysts ◽

10.3390/catal11121556 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1556

Author(s):

Arantxa Davó-Quiñonero ◽

Sergio López-Rodríguez ◽

Cristian Chaparro-Garnica ◽

Iris Martín-García ◽

Esther Bailón-García ◽

...

Keyword(s):

Co Oxidation ◽

Density Functional ◽

Hydrogen Transfer ◽

Surface Defects ◽

Co Adsorption ◽

Oxidation Mechanism ◽

Density Functional Theory Calculations ◽

Hydroxyl Groups ◽

Selective Co Oxidation ◽

Physicochemical Features

The preferential CO oxidation (so-called CO-PROX) is the selective CO oxidation amid H2-rich atmospheres, a process where ceria-based materials are consolidated catalysts. This article aims to disentangle the potential CO–H2 synergism under CO-PROX conditions on the low-index ceria surfaces (111), (110) and (100). Polycrystalline ceria, nanorods and ceria nanocubes were prepared to assess the physicochemical features of the targeted surfaces. Diffuse reflectance infrared Fourier-transformed spectroscopy (DRIFTS) shows that ceria surfaces are strongly carbonated even at room temperature by the effect of CO, with their depletion related to the CO oxidation onset. Conversely, formate species formed upon OH + CO interaction appear at temperatures around 60 °C and remain adsorbed regardless the reaction degree, indicating that these species do not take part in the CO oxidation. Density functional theory calculations (DFT) reveal that ceria facets exhibit high OH coverages all along the CO-PROX reaction, whilst CO is only chemisorbed on the (110) termination. A CO oxidation mechanism that explains the early formation of carbonates on ceria and the effect of the OH coverage in the overall catalytic cycle is proposed. In short, hydroxyl groups induce surface defects on ceria that increase the COx–catalyst interaction, revealed by the CO adsorption energies and the stabilization of intermediates and readsorbed products. In addition, high OH coverages are shown to facilitate the hydrogen transfer to form less stable HCOx products, which, in the case of the (110) and (100), is key to prevent surface poisoning. Altogether, this work sheds light on the yet unclear CO–H2 interactions on ceria surfaces during CO-PROX reaction, providing valuable insights to guide the design of more efficient reactors and catalysts for this process.

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Water in the Alluaudite Type-Compounds: Synthesis, Crystal Structure and Magnetic Properties of Co3(AsO4)0.5+x(HAsO4)2−x(H2AsO4)0.5+x[(H,□)0.5(H2O,H3O)0.5]2x+

Minerals ◽

10.3390/min11121372 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1372

Author(s):

Tamara Đorđević ◽

Ljiljana Karanović ◽

Marko Jagodič ◽

Zvonko Jagličić

Keyword(s):

Crystal Structure ◽

Tetrahedral Site ◽

Hydroxyl Group ◽

Dimensional Structure ◽

Site Symmetry ◽

Hydroxyl Groups ◽

X Ray Diffraction ◽

Hydrogen Atoms ◽

Hydrothermal Conditions ◽

Cobalt Ions

In this study, a new cobalt arsenate belonging to the alluaudite supergroup compounds with the general formula of Co3(AsO4)0.5+x(HAsO4)2−x(H2AsO4)0.5+x[(H,□)0.5(H2O,H3O)0.5]2x+ (denoted as CoAsAllu) was synthesized under hydrothermal conditions. Its crystal structure was determined by a room-temperature single-crystal X-ray diffraction analysis: space group C2/c, a = 11.6978(8), b = 12.5713(7), c = 6.7705(5) Å, β = 113.255(5)°, V = 914.76(11) Å3, Z = 2 for As6H8Co6O25. It represents a new member of alluaudite-like protonated arsenates and the first alluaudite-like phase showing both protonation of the tetrahedral site and presence of the H2O molecules in the channels. In the asymmetric unit of CoAsAllu, one of the two Co, one of the two As and one of the seven O atoms lie at 4e special positions (site symmetry 2). The crystal structure consists of the infinite edge-shared CoO6 octahedra chains, running parallel to the [101¯] direction. The curved chains are interconnected by [(As1O4)0.5(H2As1O4)0.5]2− and [HAs2O4]2− tetrahedra forming a heteropolyhedral 3D open framework with two types of parallel channels. Both channels run along the c-axis and are located at the positions (1/2, 0, z) and (0, 0, z), respectively. The H2 and H4 hydrogen atoms of O2H2 and O4H4 hydroxyl groups are situated in channel 1, while the uncoordinated water molecule H2O7 at half-occupied 4e special positions and hydrogen atoms of O6H6 hydroxyl group were found in channel 2. The results of the magnetic investigations confirm the quasi one-dimensional structure of divalent cobalt ions. They are antiferromagnetically coupled with the intrachain interaction parameter of J ≈ −8 cm−1 and interchain parameter of J’ ≈ −2 cm−1 that become effective below the Néel temperature of 3.4 K.

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Molecular Modeling of Ammonia Gas Adsorption onto the Kaolinite Surface with DFT Study

Minerals ◽

10.3390/min10010046 ◽

2020 ◽

Vol 10 (1) ◽

pp. 46 ◽

Cited By ~ 2

Author(s):

Qi Cheng ◽

Yongbing Li ◽

Xiaojuan Qiao ◽

Yang Guo ◽

Yang Zhao ◽

...

Keyword(s):

Hydrogen Atom ◽

Density Functional ◽

Gas Adsorption ◽

Hydroxyl Group ◽

Partial Density ◽

Hydroxyl Groups ◽

High Porosity ◽

Ammonia Gas ◽

Nh3 Adsorption ◽

Kaolinite Surface

With high porosity and being one of the most abundant clay minerals, dried kaolinite may be an excellent adsorbent to remove ammonia gas (NH3). Here, the plane wave pseudopotential method based on density functional theory (DFT) was used to explore the mechanism of ammonia gas adsorption on the dried kaolinite, the Mulliken electric charge, and the partial density of states of atoms of the NH3/kaolinite (001) system. NH3 adsorption on kaolinite can happen in three different type adsorption positions: “top”, “bridge” and “hollow”. The “hollow” position is enclosed by two "upright" hydroxyl groups perpendicular to the (001) surface of kaolinite and a "lying" hydroxyl group parallel to the surface. At this position, the adsorption is the most stable and has the highest adsorption energy. The nitrogen atom of the NH3 molecule bonds with the hydrogen atom in the "upright" hydroxyl group on the (001) surface and its hydrogen atom forms HN…O hydrogen bond with oxygen atom in the "lying" hydroxyl group, which leads to the NH3 stably adsorbed on kaolinite (001) surface. A small part of electrons transfer between NH3 molecules and kaolinite creates weakly electrostatic adsorption between them.

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Chemical Analysis of Ultra-Thin DLC Films and Lubricant/DLC Interface Using Plasmonic Sensors

2014 Conference on Information Storage and Processing Systems ◽

10.1115/isps2014-6908 ◽

2014 ◽

Author(s):

M. Yanagisawa ◽

M. Kunimoto ◽

T. Homma

Keyword(s):

Chemical Analysis ◽

Raman Spectra ◽

Density Functional ◽

Chemical Interaction ◽

Phenyl Group ◽

Hydroxyl Group ◽

Intensity Change ◽

Hydroxyl Groups ◽

Plasmonic Sensor ◽

Nitrogenated Carbon

The technical potential of a new plasmonic sensor, which can acquire surface-enhanced Raman spectra with high sensitivity by controlling surface plasmons is demonstrated for the chemical analysis of diamond-like carbon (DLC) films, lubricant films, and the DLC/lubricant interface on magnetic disks of sub-nanometer scale. The Raman spectra of thin DLC films and lubricated DLC carbon can be acquired with a high S/N ratio. Raman spectra of lubricated DLC carbon can also be acquired with the high S/N ratio. The wavenumber shift and intensity change of the Raman peaks of the phenyl and hydroxyl groups in the mixed lubricants (ADOH and Z-tetraol) show that the chemical interaction with the DLC surfaces of the phenyl group in the lubricant molecule decreases with increasing nitrogen content, whereas that of the hydroxyl group with the nitrogenated carbon increases. Raman spectra of nitrogenated DLC films are also acquired, the peaks show good agreement with density functional theory calculations. The calculated bonding energy indicates that the hydroxyl groups interact with the nitrogenated carbon.

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Nano-design of Zeolites Biomass Wastes Valorization: Dehydration of Lactic Acid into Acrylic Acid

Inżynieria Mineralna ◽

10.29227/im-2019-01-32 ◽

2021 ◽

Vol 1 (1) ◽

Author(s):

Izabela KURZYDYM ◽

Izabela CZEKAJ

Keyword(s):

Lactic Acid ◽

Acrylic Acid ◽

Density Functional ◽

Zeolite Catalysts ◽

Hydroxyl Group ◽

Generalized Gradient ◽

Bea Zeolite ◽

The Hierarchical Structure ◽

Bridge Oxygen ◽

Non Local

The valorization of waste from biomass currently arouses great interest. In the present study we concentrate on the design of innovative BEA zeolite catalysts with applied metal nanoparticles - copper, vanadium and manganese for the dehydration of lactic acid to acrylic acid. Th e ab initio method based on density functional theory (DFT) was used to calculate the electron structure of the analyzed molecules. The non-local generalized gradient corrected functionals GGA-RPBE was used to in order to account for electron exchange and correlation. The cluster model was represented by a hierarchical zeolite M2Al2Si12O40H22 (M = Cu, V, Mn). Th e stabilization of the M-Ob-M dimer complex in the hierarchical structure of BEA, mechanism of adsorption of lactic acid on BEA zeolite with applied metal dimers and formation of acrylic acid on these zeolites were investigated. Th e examined metals form stable dimers interconnected by a bridge oxygen (Ob). Adsorption of lactic acid takes place in the vicinity of a dimer of M-Ob-M.The dehydration of lactic acid to acrylic acid in all cases consists in the separation of the hydroxyl group and creating a connection with a metal center of dimer and disconnection of a single hydrogen atom from the methyl group and its interaction with bridge oxygen of dimer.

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