Search

Background: The removal of trace amount of BCl3 from SiHCl3 by adsorption is an efficient method in manufacture of electronic grade polysilicon. Objective: DFT simulations were used to investigate the adsorption mechanism of aliphatic amine adsorbents and to compare the performance of these adsorbents. Methods: The adsorption energies, mulliken charges, dipole moments and FMOs of aliphatic amines on SiHCl3 and BCl3 were calculated using the DFT method at the B3LYP/6‐311++G (2d, p) level, and on this basis the factors affecting the adsorption capacity and selectivity were explored in depth. Results: The results indicates that these adsorbents show good adsorption performance and high separation efficiency for BCl3. In particular, (CH3)2NH has the highest adsorption capacity for BCl3 at 298 K and 1 atm and achieves effective desorption at high temperatures to allow the adsorbent to be reused. Conclusions: The adsorption behaviors are strongly affected by frontier orbitals, dipoles and polarizabilities of aliphatic amines, among which HOMO of amines plays the decisive role for adsorbing BCl3, providing theoretical guidance for adsorbent design associated with removal of BCl3 from SiHCl3. [ABSTRACT FROM AUTHOR]

In order to reduce the CO2 content of gas pollution, it is necessary to develop more efficient, controllable and sensitive adsorption materials. In this work, the capture of CO2 by 3N‐M‐VG (3N doped mono‐vacancy graphene) nanosheets in the electric field of 0.000–0.040 a. u. were investigated by density functional theory (DFT) simulations. The interaction between CO2 and 3N‐M‐VG increased with increasing applied electric field and the adsorption of CO2 by 3N‐M‐VG underwent a transition from physical to chemisorption at electric field strengths of 0.020–0.030 a. u. In addition, the material allows the capture and release of CO2 by switching on and off an applied electric field. CO2 adsorption and selectivity of 3N‐M‐VG in CH4/H2/CO2 gas mixtures can be greatly improved by applying an electric field. Theoretical results of this study can provide guidance for the design of highly selective CO2 capture materials. [ABSTRACT FROM AUTHOR]

The effects of charging on the magnetic anisotropy energy (MAE) of rhenium atom in nitrogenized-divacancy graphene (Re@NDV) are investigated using density functional theory (DFT) calculations. High-stability and large MAE of 71.2 meV are found in Re@NDV. The more exciting finding is that the magnitude of MAE of a system can be tuned by charge injection. Moreover, the easy magnetization direction of a system may also be controlled by charge injection. The controllable MAE of a system is attributed to the critical variation in dz2 and dyz of Re under charge injection. Our results show that Re@NDV is very promising in high-performance magnetic storage and spintronics devices. [ABSTRACT FROM AUTHOR]

In this paper, the effect of Cu vacancy of Cu3Si(001) surface for the hydrogenation of silicon tetrachloride was systematically studied by density functional theory (DFT). The favorable adsorption sites and stable configurations of reaction species are obtained and three possible reaction paths of SiHCl3 formation were achieved by transition state search. For the perfect Cu3Si(001) surface(P), Path1 is the most favorable, with a reaction barrier of 158.15 kJ mol−1. For both the single Cu‐vacancy(SV) and double Cu‐vacancy Cu3Si(001) surface(DV), Path2 is the most favorable, with the reaction barriers of 130.07 kJ mol−1 and 124.81 kJ mol−1, respectively. The results reflect that the activation energy of the reaction decreased significantly with the increase of Cu‐vacancy on the Cu3Si(001) surface, which may be the reason for the higher catalytic activity of Cu3Si catalysts with smaller Cu−Si stoichiometric ratios. This study can provide a reasonable explanation for previously experimental observation and provide a guidance for future catalyst design. [ABSTRACT FROM AUTHOR]

At present, the use of hydrotalcite-like materials to remove fluoride from water is a relatively popular research topic. Herein, an experimental and theoretical study on the adsorption of F− on the surface of hydrotalcite was reported. The experiments indicate that adsorption reached equilibrium in 2 minutes. The experimental results of adsorption thermodynamics show that adsorption is spontaneous and endothermic. Calculations based on Density Functional Theory (DFT) and Molecular Dynamics (MD) simulation were used to research the adsorption of F− on the (0 0 3) crystal face of Cl−-hydrotalcite. The optimal geometric configuration of the adsorption of F− on different sites of the hydrotalcite surface was established. F− has the lowest adsorption energy (−300.565 kJ mol−1) at the vacancy above the aluminum atom and this configuration is the most stable. The analysis of the HOMO and LUMO and Fukui function results show that F− is more susceptible to electrophilic attack and adsorbed on the surface of hydrotalcite than Cl−. The calculation results of charge population and Partial Density Of States (PDOS) show that electron transfer occurred between F− and H on the surface of hydrotalcite laminates, and the strong hybridization of the F− 2p orbital with the H 1s orbital on the surface shows the formation of hydrogen bonds between them. The simulation results of adsorption thermodynamics are the same as the experimental results and the correctness of the experiment is verified. Finally, MD simulation was carried out to explain the effect of water on adsorption and confirmed the bonding mechanism. [ABSTRACT FROM AUTHOR]

In this paper, the mechanism of the deoxygenation of lignite model compounds in the aqueous phase under a CO atmosphere catalyzed by OH− ions was investigated at the M06-2X/6-311++G(d, p) level. The results revealed that for the deoxygenation of phenol, the activity of the H species follows H˙ > H− > H+, and the reaction of CO with OH− ions under aqueous conditions confirmed that H− is the dominating active species. The study of H− attacking carbon atoms at different positions on phenol indicated that deoxygenation via substitution to form benzene is preferred over hydrogenation via addition. The effect of the active species H− on the deoxygenation of the lignite model compounds phenol, benzenediols, and benzenetriols was also examined. This study provides valuable information for future research on lignite deoxygenation. [ABSTRACT FROM AUTHOR]

Abstract: The reaction mechanism of coal pyrolysis and hydrogen production in supercritical water (SCW) was investigated using the molecular dynamic simulations via the reactive force field (ReaxFF) method combined with the density functional theory (DFT) method. Our calculations present that the water clusters in SCW weaken the C–C bonds in aromatic rings, thus the C(ring)–C(ring) bond cracking energy decreases as much as 287.3kJ/mol and 94.6kJ/mol compared with that in pure coal pyrolysis and in coal pyrolysis in vapor state, respectively. After the aromatic rings break into small cyclic structures, such as quaternary rings and ternary rings, the water clusters in SCW further weaken their C–C ring bonds to induce the small cyclic rings to open. During this process, the water clusters (without any radicals) in SCW turn into H radical-rich water clusters after providing OH radicals to the cyclic rings. This is the main source for the production of hydrogen molecules in SCW–coal system. The combination of H radicals produced by coal with water clusters in SCW is another pathway which forms H radical-rich water clusters. Under the catalysis of water molecules or clusters, H radical-rich water clusters decompose into H2 and OH radicals. These OH radicals further bind with coal intermediates and result in the breaking of coal intermediates into smaller products. Therefore, the cooperative effects between SCW and coal form a virtuous circle, which greatly enhances the reaction rate of coal gasification, promotes the production of small molecules, and increases the yield of hydrogen. [Copyright &y& Elsevier]

With the increased demands of environmental protection, recycling/utilization of industrial byproducts has attracted much attention from both industry and academic communities. In this work, silicon carbide (SiC) was successfully synthesized from industrial waste silica fume (SF) during metallic silicon production. Following this, Ni nanoparticles with many defects were supported on the as-obtained SiC by conventional impregnation method. The results showed that defect-rich Ni nanoparticles were dispersed onto the surface of SiC. The as-obtained Ni/SF-SiC exhibited an enhanced metal-support interaction between Ni and SiC. Furthermore, the density functional theory (DFT) calculations showed that the H2 and CO adsorption energy on Ni vacancy (VNi) sites of Ni/SF-SiC were 1.84 and 4.88 eV, respectively. Finally, the Ni/SF-SiC performed high catalytic activity with CO conversion of 99.1% and CH4 selectivity of 85.7% at 350 °C, 0.1 MPa and a gas hourly space velocity (GHSV) of 18,000 mL·g−1·h−1. Moreover, Ni/SF-SiC processed good catalytic stability in the 50 h continuous reaction. [ABSTRACT FROM AUTHOR]

The biomass electrochemical oxidation has attracted worldwide attention owning to its carbon-neutral and sustainable nature. Here, different morphologies of CoCu-carbonate hydroxides (CH) electrodes are prepared through one-step hydrothermal method for 5-hydroxymethylfurfural electrocatalytic oxidation (HMF-ECO) to high-valued 2,5-furandicarboxylic acid (FDCA) for the first time. The results illustrate that Cu can regulate CoCu–CH morphologies from 1D nanorods to 2D ultra-thin nanosheets besides modulating the catalytic compositions. The optimal Co 1 Cu 1 –CH exhibits hybrid nanostructures containing the 1D nanorods and 2D ultra-thin nanosheets, which has the largest ECSA and specific surface area, as well as the smallest Tafel slope and impedance. The oxidation potential of HMF-ECO is 1.42 V vs RHE with the conversion of HMF 99.57%, the selectivity for FDCA 99.91%, and the FE 98.88%. In addition, Cu can promote the conversion of Co2+ to the favorable Co3+ for HMF-ECO on the catalyst surface. Density functional theory calculation indicates that Cu can improve charges transfer to HMF and lower its adsorption energy. In situ Raman spectra tests indicate that cobalt species is the active site for HMF-ECO. Furthermore, at 1.42 V vs RHE, the coupling of HMF-ECO and hydrogen evolution reaction shows that the cathodic hydrogen evolution rate is 92.33 L h−1 m−2, which is 3.69 times more than water splitting. This work provides a special structures material to process intensification of HMF electrooxidation coupling hydrogen production. [Display omitted] • Cu can regulate Co–CH forming different morphologies and nanostructures. • CoCu–CH catalysts exhibit highly efficient for HMF-ECO to FDCA. • HMF-ECO boosts H 2 evolution rate at 92.33 L h−1 m−2, 3.69 times than water splitting. • DFT illustrates Cu can improve charge transfer to HMF and lower its adsorption energy. • In situ Raman shows the cobalt species is the active site. [ABSTRACT FROM AUTHOR]

The solubility data of linezolid form II in five pure solvents (water, methanol, ethanol, 1-propanol, 2-propanol) and a binary (water + methanol) solvent were determined among the temperature range from 283.15 K to 318.15 K under atmospheric pressure. The results indicated that the solubility increased with the temperature increasing. Seven thermodynamic models were used here to correlate the experimental solubility data. Through the comparison of the experimental data in pure solvents with the calculated results, we found that the modified Apelblat equation fit the experimental data best. Furthermore, the density functional theory (DFT) calculations showed that the solubility in different solvents related to the interaction strength between the linezolid and the solvent molecules. Finally, the molar enthalpy change, molar entropy change and molar Gibbs free energy change of dissolution of linezolid in the different solvents were also calculated by van't Hoff equation in this paper. [ABSTRACT FROM AUTHOR]

Electrochemical reactions are important method for reducing the carbon footprint of large-scale chemical processes. Highly selective conversion of 5-hydroxymethylfurfural (HMF) to 2,5-dihydroxymethylfuran (DHMF) is achieved under mild conditions through electrocatalytic hydrogenation (ECH) over AgCu nanoalloys supported by the pyrolyzed biomass alginic acid sodium (PA), with the advantage of utilizing the active hydrogen intermediates in the process. The Ag 1 Cu 1 /PA exhibits outstanding performance in ECH of HMF with a selectivity of 94% toward DHMF at a conversion of 93.2% and the Faraday efficiency (FE) of 61.8%, which are significantly superior to those over Ag/PA (selectivity of 53.89%, conversion of 90.6%, and FE 25.79%). The incorporation of Cu into Ag nanoparticles boosts the charge transferability and lowers the onset potential of ECH. Density functional theory calculations reveal that AgCu alloy provides more electron transfer to HMF and lowers the energy barrier for HMF hydrogenation. [Display omitted] • AgCu nanoalloys exhibit outstanding performance in electrocatalytic hydrogenation of HMF. • AgCu nanoalloys achieve high selectivity, conversion, and faraday efficiency. • Cu-doping boosts the charge transferability and lowers the onset potential. • AgCu alloy lowers the energy barrier for HMF hydrogenation. [ABSTRACT FROM AUTHOR]

Various termination surfaces affect the valence states of Ir atoms, resulting in different NRR activities. The synergistic effects of decorated Ir atom and the surface O-terminations for Ir@ v -Mo 2 CO 2 leads to promoted NRR performance during the first hydrogenation. [Display omitted] The lack of the green, economical and high-efficient catalysts restrict the development of electrochemical nitrogen reduction reaction (NRR). By means of density functional theory (DFT) calculations, we have systematically investigated the NRR catalytic performance of single atoms decorated v -Mo 2 CT 2 (T = O, F, OH, Cl, and Li) MXene (TM@ v -Mo 2 CT 2). Our calculation results reveal the introduction of single atom can significantly improve the NRR activity and selectivity on v -Mo 2 CO 2 , and Ir@ v -Mo 2 CO 2 system possesses the lowest limiting potential of only −0.33 V among all studied systems. The termination effects of TM@ v -Mo 2 CT 2 are further discussed and a descriptor of the adsorption energy of *NNH species (ΔE(*NNH)) is proposed to establish the relationship with NRR limiting potential (U L (NRR)), in which a moderate (ΔE(*NNH)) is required for high NRR activity. Moreover, a good linear relationship between the ΔE(*NNH) and the excess electrons on Ir atom shows that different ΔE(*NNH) originates from the difference of valence state of Ir atom, which is due to the change of coordination environment. Importantly, the synergistic effects of Ir atom and the surface O-terminations during the first hydrogenation step lead to a promoted NRR performance. Our study might provide new possibilities for rational design of cost-effective MXene-based NRR electrocatalysts. [ABSTRACT FROM AUTHOR]

Ruthenium-based catalysts exhibit excellent catalyst activity in the acetylene hydrochlorination reaction and tend to be a good substitute for mercury-based catalysts due to their cheaper price among the precious metal catalysts. In this work, spin-polarized density functional theory (DFT) calculations were carried out to investigate the properties of the ruthenium single-atom catalysts supported on six different substrates (four pyridine nitrogen-doped carbon, four or three pyrrole nitrogen-doped carbon, C 2 N, CN and g-C 3 N 4), and the reaction mechanisms of acetylene hydrochlorination catalyzed by them at 453 K. According to the results of calculations, it could be found that the reaction had the lowest free energy barrier of 16.83 kcal/mol on the Ru@4 × N6 (pyridine nitrogen-doped carbon), while it had the highest free energy barrier of 49.06 kcal/mol on the Ru@g-C 3 N 4. This work will provide a theoretical support for the design of ruthenium single-atom catalysts for acetylene hydrochlorination reaction. • Six Ru single atom catalyst anchored on different substrates were established. • The reaction mechanism on each catalyst was explored by DFT calculations. • Ru single atom catalyst anchored by four pyridine nitrogen shows superior activity. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ru-based catalyst improved by quaternary ammonium IL has high catalytic performance in acetylene hydrochlorination. • TBAH IL enhanced the Ru dispersion and stabilized the Ru valence. • The interaction mechanism of TBAH IL with Ru active species and AC support has been revealed. Five quaternary ammonium ionic liquids (QAILs) were employed to synthesize Ru-based catalysts with the purpose of exploring an efficient non-mercuric catalyst for the acetylene hydrochlorination reaction. The activity and stability of Ru-QAILs/AC catalysts were investigated. Importantly, the method and sequence of impregnation were compared. The 0.1Ru15TBAH/AC catalyst prepared by co-impregnation method achieved 95% initial conversion of acetylene and 99.5% selectivity of vinyl chloride, and remained stable in the 200 h life evaluation under the conditions of T = 170 °C, GHSV (C 2 H 2) = 90 h−1 and V (HCl): V (C 2 H 2) = 1.1. A series of characterizations demonstrated that the addition of TBAH could improve the dispersion of Ru species, effectively prevent the appearance of coke deposition and increase the content of Ru4+ active species. Particularly, the mechanism of coke inhibition by adding TBAH IL was discussed via Temperature-programmed desorption (TPD) analysis, and the interaction mechanism of TBAH IL with the AC support and with the Ru species were revealed via XPS spectrum combined with density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • SiHCl 3 decomposition to Si is mainly formed on Si(1 1 1) facet due to the highest atomic density and the stronger Si-Si bond. • SiHCl 3 decomposition to SiCl 4 is more favorable than Si formation in gas phase reaction. • Promoting SiHCl 3 decomposition to Si through exposing more (1 1 1) surface area and optimizing the flow field and temperature distribution in the reactor. Clarifying the mechanism of SiHCl 3 decomposition on silicon rod and in gas phase has a remarkable impact on intensifying the technology of polycrystalline silicon production from SiHCl 3. Our work investigates the mechanism of SiHCl 3 decomposition on low index plane of silicon crystal—(1 1 1), (1 1 0) and (1 0 0) by density functional theory (DFT), and further explores the mechanism in gas phase. SiHCl 3 decomposition to Si is mainly formed on Si(1 1 1) facet due to the highest atomic density and the stronger Si-Si bond; the most favorable path is SiHCl 3 → SiCl 3 + H → SiCl 2 + Cl → SiCl + Cl → Si + Cl. The three coordination Si atoms on Si(1 1 0) and Si(1 0 0) are not in the same plane; Si(1 1 0) and Si(1 0 0) are not beneficial to SiHCl 3 decomposition to Si. In gas phase reaction, SiHCl 3 decomposition to SiCl 4 is more favorable than Si formation. In kinetics, when the temperature of silicon rod is higher than that in gas phase, the formation of Si has more advantages than SiCl 4. The findings enhance our understandings about the crystal facet structure-dependent performances of silicon crystal in polycrystalline silicon production, and provide a useful guidance for promoting SiHCl 3 decomposition to Si through exposing more (1 1 1) surface area of silicon rod and optimizing the flow field and temperature distribution in the reactor. [ABSTRACT FROM AUTHOR]

• Poly (butyl acrylamide-co-divinylbenzene) nanofiltration membrane was synthesized. • The toplayer regularly distributed oxygen and nitrogen groups to anchor metal ions. • Fe-binding treatment enhanced the permeance and dye rejection in organic solvents. • Changes of the void size and the charge density in the toplayer were disclosed. A new nanofiltration composite membrane poly (butyl acrylamide-co-divinylbenzene) (poly-TaDb) was synthesized via a facile photopolymerization on polyetherimide using the monomers of n- tert -butyl acrylamide and divinylbenzene, and evaluated the separation performance in organic solutions. The unique poly-TaDb toplayer has a feature of branch structure containing regularly distributed oxygen and nitrogen groups that work as the interacting sites with metal ions (Fe3+, Zn2+, and Cu2+), as reflected by the characterizations of ATR-FTIR, XPS, AFM, etc. Without the metal ion treatment, the optimal poly-TaDb membrane shows the permeance of 31, 17, 20.4 L m−2h−1 MPa−1 respectively for organic solutions of tetrahydrofuran (THF), methanol (MeOH) and acetonitrile (ACN), with the rejection rates higher than 90% toward EB dye (879.8 g.mol−1). After interacting with these metal ions, the obtained Fe-binding poly-TaDb membranes possess higher permeance, with the THF, MeOH, and ACN permeance enhanced respectively to 113, 35, and 24.2 L m−2h−1 MPa−1, meanwhile maintaining high dye rejection rate. While the Cu- and Zn-binding membranes show much higher permeance but lower dye rejection rate. Density functional theory (DFT) calculations disclose that the void size of the toplayer network increases in the order of: the pristine (11.40 Å) < Fe-binding (11.54 Å) < Zn-binding (11.60 Å) < Cu-binding membrane (11.63 Å). It is the suitable void size and charge density distribution in the toplayer network of Fe-binding membrane. that results in the superior nanofiltration performance. This work provides a facile route to explore new polymeric network materials for highly effective separation performance in organic solvents. [ABSTRACT FROM AUTHOR]

• The solubility of FA in twelve mono-solvents and a binary solvent were measured. • The solubility data of FA were discussed and correlated by thermodynamic models. • DFT calculations was performed to investigate the interactive energy. • The thermodynamic properties in the dissolution process of FA were analyzed. The solubility data of flonicamid (FA) in twelve mono-solvents (methanol (MA), ethanol (EA), n-propanol (NPA), isopropanol (IPA), n-butanol (NBA), isobutanol (IBA), ethyl acetate (EAC), butyl acetate (BAC), acetone (AT), acetonitrile (AN), tetrahydrofuran (THF), 1,4-dioxane (DX)) and a binary solvent of EA + EAC were experimentally measured by using a gravimetric method under atmospheric pressure. The tested temperature range for the studied solvents was from 283.15 K to 323.15 K except of 288.15–323.15 K for DX. Powder X-ray diffraction (PXRD) was applied to evaluate the crystal form of FA, and no solvate or new form formation were observed during the whole experiment. The experimental results show that the rising temperature leads to the increase of the FA solubility in all the studied mono and mixed solvents at the tested ranges. For mono-solvents, the solubility of FA at 293.15 K increases in the order: IBA (0.002641) < IPA (0.004243) < NPA (0.004361) < NBA (0.004750) < BAC (0.006844) < EA (0.006864) < EAC (0.01342) < MA (0.01394) < DX (0.01747) < AN (0.02455) < THF (0.03433) < AT (0.04645). For EA + EAC mixed solvents, the solubility of FA increases and then decreases with the rising mole fraction of EAC. That means addition of EAC to EA can alter the FA solubility. Density functional theory (DFT) calculations were performed to analyze the interactive energy between FA and the solvent molecules. Furthermore, the Apelblat equation, van't Hoff equation, λh equation are applied to correlate the experimental solubility data of FA in mono and mixed solvent systems, while NRTL model and Wilson model are selected for mono-solvents, CNIBS/R-K model and Jouyban-Acree model for mixed solvents. Correlated results demonstrate that the Apelblat model provides the best regression. In addition, the dissolution thermodynamic properties of FA in chosen solvents are analyzed by the van't Hoff equation. It suggests that the dissolution processes of FA are non-spontaneous, endothermic and entropy increase in these studied systems. [ABSTRACT FROM AUTHOR]

• The Cu-Si bond can promote SiHCl 3 formation more actively than Cl defect. • Cu-Si bond and Cl defect synergistically catalyze SiHCl 3 formation excellently. • Microkinetic modeling shows the formation rate of SiHCl 3 depends on intermediate SiCl 3. It is essential to convert SiCl 4 into SiHCl 3 over effective catalysts so as to construct a close-cycle sustainable polysilicon production process. However, the dissociation mechanism of SiCl 4 is elusive yet. Here we adopted density functional theory (DFT) calculation to study the dissociation pathway of SiCl 4 , taking into account the effect of possible Cu-Si bond as well as the existing Cl defects in CuCl 2 (1 0 0) surface. The first time we disclose that Cu-Si bond and Cl defect can synergistically catalyze the dissociation of SiCl 4 into SiHCl 3 , with the activity superior to either individual Cu-Si bond or Cl defect. The calculation results reflect that on the Si/CuCl 2 (1 0 0)-Ⅰ surface, SiCl 4 dissociation is inhibited, due to the lack of Cu-Si bond and low coordination Cu active sites; while the Si/CuCl 2 (1 0 0)-Ⅱ surface shows better catalytic activity towards SiHCl 3 formation, comparing with different Cl-defect CuCl 2 (1 0 0) surfaces. Microkinetic modeling indicates that the formation rate of SiHCl 3 depends on the intermediate SiCl 3 , and the most favorable pathway to generate SiHCl 3 is through SiCl 4 → SiCl 3 + Cl(+H) → SiHCl 3. This work can provide useful guidance on the rational design and synthesis of Cu-based catalysts for the dissociation of SiCl 4 into SiHCl 3 in the polysilicon production. [ABSTRACT FROM AUTHOR]

• Cl vacancy in CuCl 2 (0 0 1) catalyst affects the species adsorption and SiCl 4 dissociation mechanism. • Double Cl-vacancy has better SiCl 4 decomposition into SiHCl 3 , comparing with single Cl-vacancy one. • Double Cl-vacancy CuCl 2 (0 0 1) has more exposed Cu active sites to promote species adsorption and dissociation. In order to elucidate the role of chlorine vacancy on CuCl 2 catalyst in species adsorption and the mechanism of SiCl 4 dissociation into SiHCl 3 , density functional theory (DFT) calculations were performed over the CuCl 2 (0 0 1) surfaces with single and double Cl-vacancy, comparing with those over the perfect CuCl 2 (0 0 1). The calculation results show that Cl vacancies on the CuCl 2 (0 0 1) surface cause low-coordination site Cu atoms and the exposed Cu atoms work as the actually catalytic active sites, which can promote species adsorption and dissociation. The CuCl 2 catalyst enriched with exposed Cu active sites exhibits higher catalytic activity and higher selectivity of SiHCl 3. Bader charge analysis indicates that the smaller positive charge leads to the higher species adsorption energies and better catalytic selectivity and activity of SiCl 4 dissociation into SiHCl 3. The closer the d -band center is to the Fermi level, the higher the species adsorption energy and the better catalytic selectivity and activity of SiCl 4 dissociation into SiHCl 3. It suggests that the double Cl-vacancy CuCl 2 (0 0 1) catalyst has better activity and selectivity to produce SiHCl 3 via SiCl 4 decomposition, and the favorable pathway is SiCl 4 → SiCl 3 + Cl+(H) → SiHCl 3 , which can provide useful guidance on the development of efficient catalysts for SiCl 4 dissociation into SiHCl 3. [ABSTRACT FROM AUTHOR]

Here, transition-metal-embedded (TM = Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Rh, Pd and Ag) graphdiyne monolayer (TM@GDY) has been systematically investigated as nitrogen (N 2) Reduction Reaction (NRR) based on Density Functional Theory (DFT) calculations. Our study indicates that the catalytic activity of Mo@GDY can not be evaluated only by the N 2 adsorption strength on the surface of the catalyst. Instead, the interactions between hydrogen and the next nearest nitrogen atoms (H-N2) should also be considered during the first hydrogenation. • The Mo@GDY has excellent electrocatalytic activity to reduce N 2 into NH 3. • The interactions between hydrogen and its next nearest nitrogen atom are important. • NRR proceeds with ultra-low onset potential (−0.33 V) by distal mechanism. • High adsorption energy of N 2 not mean low onset potiential. The production of ammonia (NH 3) at ambient conditions has always faced enormous challenges in chemical industry. In this study, the potential of the electrocatalysts of transition-metal-embedded (TM = Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Rh, Pd and Ag) graphdiyne monolayer (TM@GDY) has been systematically investigated as nitrogen (N 2) Reduction Reaction (NRR) by Density Functional Theory (DFT). The results reveal that Mo-embedded graphdiyne monolayer (Mo@GDY) has high stability, high electrical conductivity and excellent catalytic activity with ultra-low onset potential (−0.33 V) by distal mechanism. The ultra-low onset potential is attributed to much stronger interactions between hydrogen and the next nearest nitrogen atoms (H-N2) for the distal mechanism compared with the enzymatic mechanism (−1.03 V) during the first hydrogenation. Moreover, Mo@GDY can also effectively suppress the Hydrogen Evolution Reaction (HER) during the entire NRR process. This study may provide a new approach for electrochemical N 2 reduction to form NH 3 at ambient conditions. [ABSTRACT FROM AUTHOR]