Dispersion-corrected Density Functional Theory Study Research Articles

Highly-selective Electrocatalytic Reduction of NO to NH3 using Cu Embedded WS2 Monolayer as Single-atom Catalyst: A DFT Study.

Electrocatalytic nitric oxide reduction reaction (NORR) is a promising method for generating NH3. However, developing a NORR catalyst for NH3 synthesis with low cost and high efficiency is still challenging. We here report a series of single-atom catalysts (SACs), designed by embedding nine different transition metals from Sc to Cu in S-vacant WS2 monolayer (TM@WS2), and investigate the electrocatalytic performance for NORR process using the dispersion-corrected density functional theory (DFT) calculations. Among them, Cu-based SACshows a strong binding to the WS2 surface and high selectivity towards NORR process, and also it greatly inhibits the competing hydrogen evolution reaction (HER). Through ab initio molecular dynamics (AIMD) simulations, the thermal stability of SAC is assessed and found no structure deformation even at 500 K temperature. All possible reactive pathways including distal and alternating mode at both N- and O-end configurations for NH3 production were explored. We predicted that the Cu@WS2 SAC exhibits remarkable catalytic activity and selectivity with lowest limiting potential of -0.41 V via the N-alternating pathway. Our study emphasize that the transition metal dichalcogenide (TMDC) based SACs are potential candidates for converting NO to NH3, and this opens a new avenue in designing NORR catalysts with high catalytic performance.

The effect of heterocyclization of 2-mercaptobenzimidazole on its strength of coordination to iron: A dispersion-corrected DFT study

Benzimidazole derivatives have been widely investigated as corrosion inhibitors due to their unique chemical reactivity with different metal surfaces. Herein, the effect of heterocyclization on corrosion inhibition mechanisms and bonding of two 2-mercaptobenzimidazole derivatives (MBIs) − 2,3-dihydrobenzo[4,5]imidazo[2,1-b]thiazole (2HBIT) and 3,4-dihydro-2H-benzo[4,5]imidazo[2,1-b]thiazole (3HBIT) – with Fe(110) surface was comprehensively evaluated using dispersion-corrected density functional theory (DFT). The interaction energies computed from DFT calculations successfully predicted the experimental inhibition performance. The effect of protonation on the adsorption strength of molecules was also investigated. We have found strong covalent bond formation between S, C, and N atoms of molecules and Fe-atoms. The excellent charge transfer between molecules’ atoms and Fe(110) surface was further confirmed by the projected density of states and electron density difference plots. The adsorption energy of MBI adsorbed on Fe(110) surface was also determined for comparison purposes. This study showed that the heterocyclization of 2-mercaptobenzimidazole increased the charge transfer and bonding between MBIs and the Fe(110) substrate, thereby improving their corrosion inhibition performance.

Facet-dependent catalytic activity of anatase TiO2 for the selective catalytic reduction of NO with NH3: A dispersion-corrected density functional theory study

Recently, the facet-dependent catalytic activity of anatase TiO2 for the selective catalytic reduction of NO with NH3 (NH3-SCR) has been observed experimentally. In this study, the NH3-SCR of NO on the TiO2 (001) and (101) surfaces was systematically investigated using dispersion-corrected density functional theory. We propose that the surface-assisted mechanism is predominant on the (001) surface, which involves the oxygen active sites playing a crucial role in facilitating the reaction. The NH3 dissociation step reveals the largest activation energy barrier (Ea) of 61 kJ/mol on the (001) surface, whereas the NH2NO decomposition step has the largest barrier, Ea ≈ 156 kJ/mol, on the (101) surface. The results obtained by calculation are consistent with the experimental results, which have shown that a TiO2 nanosheet with a dominant (001) facet shows superior catalytic performance in NH3-SCR of NO compared to TiO2 nanoparticles with dominant (101) facet.

Dispersion-corrected density functional theory studies on glycolic acid-metal complexes

The structure and metal complexation studies using dispersion-corrected density functional theory methods are performed for four stable glycolic acid conformers named SSC, GAC, SAC, and AAT. The condensed Fukui functions are calculated to study the favourable reactive site for metal binding on the glycolic acid conformers. The interaction of alkali metal ions (Na+, K+) with different binding sites (carboxyl, hydroxyl oxygen) of the glycolic acid conformers in the gas phase is investigated at the same level of theory. Our calculations show that the order of stability changes into SSC > AAT > GAC = SAC due to the binding of the metal ion. The relative energy values indicate that the AAT conformer is more stable than the GAC and SAC conformers. This occurs when a metal ion (Na+, K+) is bound with the carboxyl oxygen atom of glycolic acid. The QTAIM, RDG, NCI, ELF, LOL, and NBO analysis are employed in this work to understand the strength of intra- and intermolecular interactions in the glycolic acid metal complexes.

Corrosion inhibition assessment on API 5L X70 steel by preussomerin G immersed in saline and saline acetic

The spirodioxynaphthalene preussomerin G, obtained from the fungus Pyrenochaetopsis sp. T1-41 (Plesosporales), was evaluated as a corrosion inhibitor in API 5L X70 steel samples. According to the electrochemical impedance spectroscopy and polarization curves analysis, the natural product showed good corrosion inhibition properties under static conditions in two corrosive media. The maximum efficiency (η = 91%) was obtained in the NaCl 3% medium with a 5-ppm inhibitor concentration. In the NaCl 5% w/v-glacial acetic acid 0.5% v/v medium, the charge transfer resistance value decreased, and the inhibition efficiency was 75%. In addition, the polarization curves show that preussomerin G behaves as an anodic inhibitor in the saline medium but presents mixed (anodic/cathodic) characteristics in the saline-acetic medium. Moreover, the thermodynamic analysis indicates that preussomerin G is adsorbed onto the steel surface via chemisorption, according to the Langmuir isotherm. According to a dispersion-corrected density functional theory study, at the BPW91-D2/6-311++G(2d,2p) level, ether and carbonyl groups bond with the metal surface. Finally, the surface analysis by scanning electron microscopy shows that the corrosion in API 5L X70 steel decreased in the presence preussomerin G. Highlights Preussomerin G showed good corrosion inhibition properties under static conditions in two corrosive media. The adsorption of preussomerin G onto the steel surface via chemisorption obeys the Langmuir isotherm. Ether and carbonyl groups are responsible of the chemisorption of preussomerin G onto the metal surface. Preussomerin G provides an almost inert protective cover, towards nucleophilic and electrophilic attacks, to the metal surface.

Carboxyl- and amine-functionalized carboranethiol SAMs on Au(111): A dispersion-corrected density functional theory study

The morphological and electronic properties of isolated and monolayer phases of carboxyl- and amine-functionalized carboranethiols on unreconstructed Au(111) were determined using density functional theory calculations by including van der Waals interactions. The groups are effective in the assembly of pristine adlayers on gold and also offer functionality when exposed at the SAM-environment interface. Anisotropy brought by both functional groups increases tilting of carboranethiols relative to the surface normal and absolute values of the dissociative chemisorption energies. Positional isomerization and the functional groups modify the molecular dipole moments which influnce the adsorption characteristics. Even though carboxylic acid and amine groups have different chemical properties, they have similar effects on the adsoprtion characteristics of carboranethiols. Dense packing favors intermolecular interactions which gives a stronger binding relative to isolated adsorption. The carboranethiols with the functional groups can be arranged in the same lateral direction or in a dimer conformation with molecues facing each other. Carboxyl and amine groups offer functionalization of cabranethiol SAMs and in conjuction with positional isomerization shift tunability ranges of the work function of gold to higher energies.

Energetics of Hybrid Structures between Cycloparaphenylene and Carbon Nanotubes: A Dispersion-Corrected Density Functional Theory Study

Dispersion-corrected density functional theory (DFT) calculations examined energetically preferable hybrid structures between [13]cycloparaphenylene ([13]CPP) and an armchair (m,m) tube (5 ≤ m ≤ 9)...

Physi-Sorption of H2 on Pure and Boron–Doped Graphene Monolayers: A Dispersion–Corrected DFT Study

High-surface-area carbons are of interest as potential candidates to store H2 for fuel–cell power applications. Earlier work has been ambiguous and inconclusive on the effect of boron doping on H2 binding energy. Here, we describe a systematic dispersion–corrected density functional theory study to evaluate the effect of boron doping. We observe some enhancement in H2 binding, due to the presence of a defect, such as terminal hydrogen or distortion from planarity, introduced by the inclusion of boron into a graphene ring, which creates hydrogen adsorption sites with slightly increased binding energy. The increase is from −5 kJ/mol H2 for the pure carbon matrix to −7 kJ/mol H2 for the boron–doped system with the boron content of ~7%. The H2 binding sites have little direct interaction with boron. However, the largest enhancement in physi-sorption energy is seen for systems, where H2 is confined between layers at a distance of about 7 Å, where the H2 binding nearly doubles to −11 kJ/mol H2. These findings suggest that interplanar nanoconfinement might be more effective in enhancing H2 binding. Smaller coronene model is shown to be beneficial for understanding the dependence of interaction energy on the structural configurations and preferential H2 binding sites.

The investigation of optoelectronic, magnetic and dynamical properties of Ce and Ti doped 2D blue phosphorene: A dispersion corrected DFT study

The present study has been performed to investigate optoelectronic, magnetic and dynamical properties of pristine blue phosphorene (BP), (Ce, Ce–Ce, Ti, Ti–Ti) doped BP and single vacancy BP using the Cambridge Serial Total Energy Package (CASTEP) simulation code based on the density functional theory (DFT). The optical and vibrational properties were carried out by employing dispersion corrected density functional theory. The calculated lattice constants for pristine blue phosphorene a = b = 3.33 Å are found to be improved by Tkatchenko-Scheffler (TS) and Grimme (G06) schemes for 2D phosphorene. The band structures and density of states results have figured out indirect band gaps as 1.93eV (pristine), 0.35eV (with single vacancy), 0.37eV (Ce doped), 0.68eV (Ti doped), and 0.56eV (Ti–Ti doped) in blue phosphorene. Whereas, no band gap has been observed for Ce–Ce doped blue phosphorene. The phonon dispersion curves obtained by density functional theory perturbation theory presented dynamical stability of the studied materials without any imaginary modes of phonon spectra. The Raman active optical modes of vibrations are found at the highest frequency of 520 cm−1. The Spin polarized density of states portray that (Ce, Ti, Ti–Ti) doped blue phosphorene exhibit semi-metallic like behavior due to hybridization of 4f, 5d and 3d localized energy states. The optical properties show that the plasma frequencies occurred at 11.34eV (pristine), 8.6 eV (Ce-doped) and 9.03eV (Ti-doped) blue phosphorene. Moreover, significant shift of absorption peak towards high energy range is clear signature of the blue shift.

A DFT study of the ORR on M–N3 (M = Mn, Fe, Co, Ni, or Cu) co-doped graphene with moiety-patched defects

Graphene-based nanomaterials have potential as electrocatalysts for the oxygen reduction reaction (ORR) due to their unique physical and chemical properties. In this study, the mechanism of the ORR on M–N3 (M = Mn, Fe, Co, Ni, Cu) co-doped graphene with defects is investigated using dispersion-corrected density functional theory (DFT) computations. The results show that Mn-N3-Gra, Co-N3-Gra, and Ni-N3-Gra are more thermodynamically stable than Fe-N3-Gra and Cu-N3-Gra. Only Mn-N3-Gra exhibits some catalytic activity at pH < 11.327 while M-N3-Gra (M = Fe, Co, Ni, and Cu) are not suitable ORR catalysts. Under acidic conditions at pH = 0, the overpotentials of the optimal 4e− catalytic path are 0.56 V, 0.849 V, and 0.381 V for Mn-N3-Gra, Co-N3-Gra, and Ni-N3-Gra, respectively. These values are consistent with experimental results. These results indicate that Ni-N3-Gra, the optimal catalyst in this study, is comparable with Pt. The M-N3-Gra (M = Fe, Cu) catalysts cannot promote ORR under acid conditions.

Structural and elastic properties of CaCO3 hydrated phases: A dispersion-corrected density functional theory study

Structural and elastic properties of the two known hydrated phases of calcium carbonate (i.e., ikaite and monohydrocalcite) were investigated. A comparative study was conducted where computer atomistic simulations based on standard density functional theory (DFT-PBE) and dispersion-corrected density functional theory (DFT-D2) were performed. Properties such as the elastic constants, the bulk modulus, the Young modulus, the shear modulus, the Poisson ratio, the velocities of acoustic waves, and the Debye temperature were evaluated for the first time at the DFT level of theory. As most of the properties investigated have not been measured experimentally yet, the DFT-PBE and DFT-D2 values provide limits that allow bracketing of the unknown experimental values. The evolution with pressure of the structural and elastic properties of ikaite and monohydrocalcite was investigated in the range from 0 to 5 GPa. In monohydrocalcite, a brittle-ductile transition is predicted to occur between 1.3 and 2.2 GPa.

Si-coordinated nitrogen doped graphene: A robust and highly active catalyst for NO + CO reaction

A dispersion-corrected density functional theory study is performed about reaction pathways and energy barriers of NO reduction by CO over Si-coordinated nitrogen doped graphene (SiN4-Gr). The results indicate that NO molecule can be stably chemisorbed over the Si atom of SiN4-Gr due to the favorable hybridization of Si-3p and NO-2π* states. The coadsorption of NO molecules to form absorbed (NO)2 species is proved to be the initial step for the reduction of NO molecules over the title surface. The energy barriers for the (NO)2 → N2O + O* reaction are in the range of 0.38–0.60 eV, which seem to be overcome at ambient condition. According to our findings, NO reduction over SiN4-Gr is a thermodynamically favored process at a relatively wide range of temperatures.

Intercalation of transition metals in aluminene bi-layers: An ab initio study.

Using first principles calculations based on density functional theory (DFT), we probe various possible stacking arrangements of bilayer aluminene and intercalate six transition metal (TM) atoms (Ti, Cr, Mn, Fe, Co, and Ni) in unique bilayer aluminene systems. Further, we calculate valence charge density and electron localization function to ascertain the nature of bonding present in both the pristine and TM-intercalated composite systems. Intercalation of Cr, Mn, and Fe is found to result in the magnetic ground state. For Ti, Co, and Ni-intercalated systems, the starting trigonal symmetry has changed to a tetragonal symmetry. Co and Ni intercalated systems exhibit much higher (negative) formation energies compared to the other composite systems. In addition, nesting of the Fermi surface has been probed for the Co and Ni intercalated systems and observations indicate the possibility of the presence of charge density wave in the systems. A dispersion-corrected DFT study suggests that the van der Waals interaction is not likely to play a crucial role in determining the properties of both the pristine and TM-intercalated systems.

Carbene-Catalyzed Enantioselective Decarboxylative Annulations to Access Dihydrobenzoxazinones and Quinolones.

A direct decarboxylative strategy for the generation of aza-o-quinone methides (aza-o-QMs) by N-heterocyclic carbene (NHC) catalysis has been discovered and explored. This process requires no stoichiometric additives in contrast with current approaches. Aza-o-QMs react with trifluoromethyl ketones through a formal [4+2] manifold to access highly enantioenriched dihydrobenzoxazin-4-one products, which can be converted to dihydroquinolones through an interesting stereoretentive aza-Petasis-Ferrier rearrangement sequence. Complementary dispersion-corrected density functional theory (DFT) studies provided an accurate prediction of the reaction enantioselectivity and lend further insight to the origins of stereocontrol. Additionally, a computed potential energy surface around the major transition structure suggests a concerted asynchronous mechanism for the formal annulation.

Anion-π Architectures of HAT(CN)6 and 5d Polycyanidometalates: [W(CN)8]3–, [Re(CN)7]3–, and [Pt(CN)6]2–

Homoleptic polycyanido-complexes of 5d metal ions with high coordination numbers (C.N.), 8 for [W(CN)8]3–, 7 for [Re(CN)7]3–, and 6 for [Pt(CN)6]2–, are found to form supramolecular anion-π chains with the multisite anion receptor HAT(CN)6 (hexaazatriphenylenehexacarbonitrile). The chains adopt a zigzag topology in the case of (XPh4)3[W(CN)8]·HAT(CN)6 (X = P: 1, X = As: 2) and (PPh4)3[Re(CN)7]·HAT(CN)6 (3), and a linear arrangement in the case of (PPh4)2[Pt(CN)6]·HAT(CN)6·0.5CH3CN·2Et2O (4). The anion-π interactions consist of 3-fold {M–C≡N–···δ+centroidpyrazine,ring}3 or single {M–C≡N–···δ+centroidpyrazine,C–C bond} intermolecular contacts with separation distances in the range of 2.79–3.20 A. An M-(CN)− → HAT(CN)6 charge transfer (CT) along these anion-π contacts is evidenced in the solid state by the appearance of new absorptions in the visible range of UV–vis electronic absorption spectra, as compared to the starting materials, and by dispersion-corrected density functional theory studies. The CT anio...

A DFT study on the possibility of using a single Cu atom incorporated nitrogen‐doped graphene as a promising and highly active catalyst for oxidation of CO

AbstractUsing dispersion‐corrected density functional theory (DFT) calculations, a single Cu adatom incorporated nitrogen‐doped graphene (CuN3‐Gr) is proposed as a new and highly active noble‐metal‐free catalyst for carbon monoxide (CO) oxidation reaction. According to our results, the Cu adatom can be stably anchored onto the monovavancy site of the nitrogen‐doped graphene, and the resulting large diffusion barrier suggests that the metal clustering is avoided in CuN3‐Gr. Three possible reaction mechanisms for CO oxidation (ie, Eley–Rideal, Langmuir–Hinshelwood, and termolecular Eley–Rideal) are systematically studied. It is found that the activation energy for the rate‐determining step of the termolecular Eley–Rideal mechanism is only 0.13 eV, which is much smaller than those of others. The results of this study may provide a useful guideline for the design of highly active and promising single‐metal catalysts for the CO oxidation reaction based on graphene.

Adsorption behavior of CO2 on pristine and doped phosphorenes: A dispersion corrected DFT study

The density functional theory (DFT) method was used to study the adsorption of CO2 molecules on pristine and doped phosphorenes. Twenty dopants were considered during this study: Fe, Co, Ni, Ti, Cu, Au, Ag, Ca, Cr, Pd, Pt, V, Sr, Mn, B, C, N, O, Si, Ge, Se, and S. Two initial configurations of CO2 on the pristine and doped phosphorenes were also studied. The results for adsorption energy, isosurface of electron density difference, partial density of states, and charge transferring analysis indicated that pristine phosphorene had a very weak interaction with CO2. Some of transition metallic dopants, namely Fe, Co, Ti, Ni, Cr, and V, significantly improved the interactions between phosphorenes and CO2. Some other metallic dopants, however, namely Au, Ag, Pd, and Pt, and nonmetallic dopants, namely Ge, Si, Se, S, N, C, B, and O had negligible effect on the interactions between CO2 and phosphorene. Cr, Fe, Ti and V-doped phosphorenes had the potential to enhance CO2 adsorption with a particular CO2 configuration. The role of charge donor or acceptor changed between CO2 and (V- Cr-, Fe-, and Ti-) doped phosphorenes when the initial CO2 configuration changed. Thus, the use of transition metallic dopants was an effective way to enhance the interactions between CO2 and phosphorene. In particular, (V- Cr-, Fe-, and Ti-) doped phosphorenes showed the potential to sense or capture CO2 molecules.

CO2 interaction with violarite (FeNi2S4) surfaces: a dispersion-corrected DFT study.

The unbridled emissions of gases derived from the use of fossil fuels have led to an excessive concentration of carbon dioxide (CO2) in the atmosphere with concomitant problems to the environment. It is therefore imperative that new cost-effective catalysts are developed to mitigate the resulting harmful effects through the activation and conversion of CO2 molecules. In this paper, we have used calculations based on the density functional theory (DFT), including two semi-empirical approaches for the long-range dispersion interactions (-D2 and -D3), to explore the interaction of CO2 with the surfaces of spinel-structured violarite (FeNi2S4). This ternary sulfide contains iron ions in the highest possible oxidation state, while the nickel atoms are in the mixed 2+/3+ valence state. We found that CO2 interaction with violarite is only moderate due to the repulsion between the oxygen lone pairs and the electronic clouds of the sulfur surface atoms. This suggests that the CO2 activation is not dictated by the presence of nickel, as compared to the pure iron-isomorph greigite (Fe3S4). These results differ from findings in (Ni,Fe) ferredoxin enzymes, where the Ni/Fe ratio influences the redox potential, which suggests that the periodic crystal structure of violarite may hinder its redox capability.

Adsorption and Desulfurization Mechanism of Thiophene on Layered FeS(001), (011), and (111) Surfaces: A Dispersion-Corrected Density Functional Theory Study.

Layered transition-metal chalcogenides have emerged as a fascinating new class of materials for catalysis. Here, we present periodic density functional theory (DFT) calculations of the adsorption of thiophene and the direct desulfurization reaction pathways on the (001), (011), and (111) surfaces of layered FeS. The fundamental aspects of the thiophene adsorption, including the initial adsorption geometries, adsorption energies, structural parameters, and electronic properties, are presented. From the calculated adsorption energies, we show that the flat adsorption geometries, wherein the thiophene molecule forms multiple π-bonds with the FeS surfaces, are energetically more favorable than the upright adsorption geometries, with the strength of adsorption decreasing in the order FeS(111) > FeS(011) > FeS(001). The adsorption of the thiophene onto the reactive (011) and (111) surfaces is shown to be characterized by charge transfer from the interacting Fe d-band to the π-system of the thiophene molecule, which causes changes of the intramolecular structure including loss of aromaticity and elongation of the C–S bonds. The thermodynamic and kinetic analysis of the elementary steps involved in the direct desulfurization of thiophene on the reactive FeS surfaces is also presented. Direct desulfurization of thiophene occurs preferentially on the (111) surface, as reflected by the overall exothermic reaction energy calculated for the process (ER = −0.15 eV), with an activation energy of 1.58 eV.

The dynamics of benzene on Cu(111): a combined helium spin echo and dispersion-corrected DFT study into the diffusion of physisorbed aromatics on metal surfaces.

We use helium spin-echo spectroscopy (HeSE) to investigate the dynamics of the diffusion of benzene adsorbed on Cu(111). The results of these measurements show that benzene moves on the surface through an activated jump-diffusion process between the adsorption sites on a Bravais lattice. Density Functional Theory (DFT) calculations with van der Waals (vdW) corrections help us understand that the molecule diffuses by jumping through non-degenerate hollow sites. The results of the calculations shed light on the nature of the binding interaction between this prototypical aromatic molecule and the metallic surface. The highly accurate HeSE experimental data provide a quantitatively stringent benchmark for the vdW correction schemes applied to the DFT calculations and we compare the performances of several dispersion interaction schemes.