BN Sheet Research Articles

Functionalization of B33N33H22 Nanosheets with α-Amidino Carboxylic Acids: A DFT Study

Using density functional theory calculations (based on the B3LYP/6-31G(d) method), we investigated the functionalization of a BN nanosheet (B33N33H22) by different α-amidino carboxylic acids (ACA). It was found that the pristine BN sheet can be noncovalently functionalized by the ACA with an adsorption energy of about − 2.7 kcal/mol. Also, the results showed that structural Stone–Wales (SW) defects significantly increase the adsorption energy. The SW-BN nanosheet transforms from an insulator to a semiconductor by covalent functionalization. Incorporating –NH2 and –NO2 groups in the structure of the ACA molecule increases and decreases the adsorption energy, respectively. The –NH2 group compared to the –NO2 was found to be more favorable for covalent functionalization especially when it is substituted at the meta position of phenyl group of ACA molecule. Investigating the effect of some other electron donating groups showed that the favorability order of applied groups for functionalization is as follows: –N(CH3)2 > –OH > –NH2 > –OCH3 > –Phenyl > –F. Furthermore, it was found that the solubility of BN nanosheets significantly increases, depending on the type of functional group.

Investigation of Sarin Nerve Agent Adsorption Behavior on BN Nanostructures: DFT Study

The adsorption behavior and electronic response of BN nanosheet, nanotube, and nanocage to sarin gas, a nerve agent, were studied using density functional theory calculations. The adsorption energy is increased by increasing the BN nanostructure curvature, and it is about − 0.5, − 1.6, and − 3.4 kcal/mol for BN sheet, tube, and cage, respectively. The BN sheet and tube are insensitive to sarin gas. Although the BN cage is sensitive, it suffers from a weak interaction, and low adsorption capacity. To overcome this problem the BN cage is doped with different impurity atoms including, Sc, Al, Si, and C. The Sc and Al dopings significantly increase the reactivity of BN cage to sarin but the sensitivity is not increased sensibly. The Si and C dopings make the BN cage more reactive and sensitive to sarin gas. The C-doped BN nanocage may be a promising sensor because of its higher sensitivity, compared to the Si-doped one. After the sarin adsorption on the C-doped BN cage, its gap decreases by about 64.0% which exponentially increases the electrical conductivity, creating an electrical signal. Also, the recovery time is about 7.9 × 1015, 1.4 × 1023, 0.004, and 0.013 s for Sc, Al, Si, and C-doped BN cages, respectively.

Single Si atom supported on defective boron nitride nanosheet as a promising metal‐free catalyst for N2O reduction by CO or SO2 molecule: A computational study

AbstractThe low‐temperature reduction of N2O plays a significant role for solving the growing environmental and health issues caused by emission of this greenhouse gas. The aim of this study is to investigate the possible reaction pathways for the reduction of N2O by CO or SO2 molecule over Si‐doped boron nitride nanosheet (Si‐BNNS). According to our results, a B or N‐vacancy defect in BN sheet could be able to greatly stabilize the single Si adatom. The relatively large diffusion barrier for the Si atom over the defective BN sheet also indicates Si‐BNNS is stable enough to be utilized in catalytic reduction of N2O. The large charge‐transfer from the surface to N2O leads to the spontaneous dissociation of this molecule into N2 molecule and an activated oxygen atom (Oads). The Oads moiety is then eliminated by CO or SO2 molecule. The calculated activation energies and reaction energies reveal that the Si atom located on top of the B‐vacancy site has a large catalytic activity toward the reduction of N2O by CO or SO2.

Designing BN sheets of X-G//(h-BN)<SUB align="right">n//X-G (X = B, N) and GO/h-BN/GO structures for based anodes material to improve the performance of lithium-ion batteries

We have investigated theoretically the efficiency of lithium-ion batteries (LIBs), aiming to remove some problems such as fire and explosion of the LIBs in view point of based anode materials. Nano-boron nitride compounds have displayed great potential as anode materials for LIBs due to their unique structural, mechanical, and electrical properties. The measured reversible lithium ion capacities of graphene/(h-BN)n/graphene(G/h-BN/G) based anodes are considerably improved compared to the conventional graphite(G)-based anodes. In this study boron nitride sheet has been localised inside the graphene as an option to enhance electrochemical ratio. Additionally, we have found that the structure of G/h-BN/G can be provide a suitable strategy for improving the performance of B-N-G based anodes because of its assembling into free-standing electrodes without any binder or current collector, which will lead to increased specific energy density for the overall battery design. In addition the modification of BN sheets and designing of X-G/h-BN/X-G structures (X = B and N) provides an extra strategy to improve the performance of LIBs. This study will help to create better anode materials which can replace graphite for higher capacity and better cycling performance in LIBs.

Efficient charge separation and visible-light response in bilayer HfS2-based van der Waals heterostructures.

Two-dimensional (2D) hafnium disulfide (HfS2) has been synthesized and is expected to be a promising candidate for photovoltaic applications, and at the same time the hexagonal BN sheet (h-BN) and graphene-like C3N4 sheet (g-C3N4) have also been fabricated and are expected to be applied in photocatalysis. In this work, we employ hybrid density functional theory to investigate HfS2-based van der Waals (vdW) heterojunctions for highly efficient photovoltaic and photocatalytic applications. HfS2/h-BN and HfS2/g-C3N4 heterostructures with direct bandgaps and efficient charge separation are both typical type-II semiconductors and have potential as photovoltaic structures for solar power. Moreover, compared with h-BN and g-C3N4 single-layers, HfS2/h-BN heterostructures with 6% tensile strain and HfS2/g-C3N4 heterostructures with 9% tensile strain have moderate bandgaps, whose optical absorption is obviously enhanced in the ultraviolet-visible (UV-VIS) light range and whose bandedges are suitable for photocatalytic water splitting. HfS2/h-BN heterostructures with 6% applied strain, being different from HfS2/g-C3N4 heterostructures with 9% strain, possess a direct bandgap and show complete separation of the photoinduced electron–hole pairs. Thus the HfS2/h-BN heterojunction with 6% strain has bright prospects for use in visible light photocatalytic water splitting to produce hydrogen.

Adsorption modes of molecular iodine on defected boron nitrides: A DFT study

The interaction of molecular iodine with pristine and monovacant boron-nitride quantum dots (QDs) have been investigated using density functional theory. It was found that removing one B or N single atom significantly decreased the calculated Eg values at various exchange functional. In B-defected BN system, the localized spin densities canceled each other and overall polarization of system was found to be equal to unity. For N-defected system there was smaller spin densities localized on each closest B atoms. Both B- and N-vacancies caused appearance of new states in gap region. Our calculation revealed that spin density and polarization of defected system are localized on vacancy region and other atoms did not take part in this polarization. The results of electron localization function for N-DBN showed there was high density region at the position of removed nitrogen atom. The calculated adsorption energies implied that there was no significant chemical interaction between iodine molecule and pristine BN sheet. We suggested that when a deficiency was imposed to the BN sheet, the reactivity of the modified system toward iodine molecule significantly could increase. We found strong interaction between iodine and nitrogen atoms of B-DBN system. In the case of I2/N-DBN system the neighbor atoms had no contribution in spin polarization of the system and it seemed that all spin density of system transferred to the iodine molecule after adsorption. Strong correlation between molecular iodine orientation and BN-QDs via their interactions type has been clarified in this work. These findings may provide a deeper insight into halogen molecules interactions with low dimensional defected boron nitrides.

Orientational order and dynamics of interfacial water near a hexagonal boron-nitride sheet: An ab initio molecular dynamics study.

Structural and dynamical properties of interfacial water molecules near a hexagonal boron nitride sheet (h-BN) are investigated by means of Born-Oppenheimer molecular dynamics simulations. Orientational profiles in the interfacial regions reveal two distinct types of water molecules near the BN surface. Depending on the positions of the water molecules, on top of either N or B atoms, one type contains water molecules that are oriented with one OH bond pointing toward the N atoms and the other type contains water molecules that remain parallel to the BN sheet. Distinct hydrogen bonding and stabilization energies of these two types of water molecules are found from our calculations. In order to see the effects of dispersion interactions, simulations are performed with the BLYP (Becke-Lee-Yang-Parr) functional and also BLYP with Grimme's D3 corrections (BLYP-D3). An enhancement of water ordering near the surface is observed with the inclusion of dispersion corrections. Further analysis of the diffusion coefficients, rotational time correlation functions, and hydrogen bond dynamics shows that water molecules near the h-BN sheet move faster compared to bulk water molecules both translationally and rotationally. The water molecules in the first layer are found to show substantial lateral diffusion. The escape dynamics of water from the solvation layer at the BN surface is also looked at in the current study. We have also investigated some of the electronic properties of interfacial water such as the charge density and dipole moment. It is found that the water molecules at the surface of the BN sheet have a lower dipole moment than bulk molecules.

Hydrogen Release from NH3 in the Presence of BN Graphene: DFT Studies

<p>Using density functional theory, we investigated the interaction<br />of an NH3 molecule with a pristine and antisite defected BN sheet<br />(g-BN) in terms of energetic, geometric, and electronic properties.<br />The adsorption energy of NH3 on defected g-BN was calculated to be<br />in the range of −0.70 to −2.46 eV, which is considerably more negative<br />than that on the pristine sheet. It was found that the adsorption<br />of NH3 adsorption on the defected sheet may cause the release of an<br />H2 molecule. The electronic properties of the defected BN sheet were<br />significantly changed after the adsorption process so that its HOMO/<br />LUMO energy gap was changed from 3.31 to 3.60-4.97 eV. Moreover,<br />the Fermi level of the defected sheet shifts to higher energies after the<br />interaction, which results in reduced potential barrier of the electron<br />emission for the sheet surface, enhancing the field emission because<br />of the decreased work function.</p>

Substitutional carbon doping of free-standing and Ru-supported BN sheets: a first-principles study

The development of spatially homogeneous mixed structures with boron (B), nitrogen (N) and carbon (C) atoms arranged in a honeycomb lattice is highly desirable, as they open the possibility of creating stable two-dimensional materials with tunable band gaps. However, at least in the free-standing form, the mixed BCN system is energetically driven towards phase segregation to graphene and hexagonal BN. It is possible to overcome the segregation when BCN material is grown on a particular metal substrate, for example Ru(0 0 0 1), but the stabilization mechanism is still unknown. With the use of density-functional theory we study the energetics of BN/Ru slabs, with different types of configurations of C substitutional defects introduced to the h-BN overlayer. The results are compared to the energetics of free-standing BCN materials. We found that the substrate facilitates the C substitution process in the h-BN overlayer. Thus, more homogeneous BCN material can be grown, overcoming the segregation into graphene and h-BN. In addition, we investigate the electronic and transport gaps in free-standing BCN structures, and assess their mechanical properties and stability. The band gap in mixed BCN free-standing material depends on the concentration of the constituent elements and ranges from zero in pristine graphene to nearly 5 eV in free-standing h-BN. This makes BCN attractive for application in modern electronics.

The creation of racks and nanopores creation in various allotropes of boron due to the mechanical loads

Two-dimensional (2D) materials have recently attracted a great attraction. This paper provides a detailed discussion on the rupture mechanisms of different allotropes of boron. As a new 2D material by using a reactive molecular dynamics model, probable types of rupture for borophene sheets were studied, among which two dominant mechanisms were observed: creation of the cracks and formation of nanopores. The results obtained are compared to those for graphene and h-BN nano sheets, although the rupture mechanism was completely different from the graphene and h-BN sheets. The simulations suggested that borophene might remain more stable against external mechanical loads than graphene and BN sheets. Cracking leads to larger strain along the loading direction, whereas the creation of local pores spends the imposed energy for breaking the internal bonds and so flowing the external energy into the various bonds increases the number of pores. For the armchair-types, cracking is a dominant mechanism while for the zigzag-type the common mechanism is the creation of nanopores. These interesting results may help to design a new class of semiconductors that remain stable even when are sustaining uncontrollable external stresses.

Transferable single-crystal GaN thin films grown on chemical vapor-deposited hexagonal BN sheets

Single-crystal gallium nitride (GaN) layers were directly grown on centimeter-scale hexagonal boron nitride (h-BN). Using chemical vapor deposition (CVD), centimeter-scale h-BN films were synthesized on a single-crystal Ni(111) and readily transferred onto amorphous fused silica supporting substrates that had no epitaxial relationship with GaN. For growing fully coalescent GaN layers on h-BN, the achievement of high-density crystal growths was a critical growth step because the sp2-bonded h-BN layers are known to be free of dangling bonds. Unlike GaN layers grown on a typical heterogeneous sapphire substrate, the morphological and microstructural results strongly suggest a high-density growth feature that is driven by the atomic cliffs inherent in the CVD-grown h-BN layers. More importantly, the GaN layers grown on CVD-grown h-BN exhibited a flat and continuous surface morphology with well-aligned crystal orientations both along the c-axis and in-plane, indicating the characteristics of GaN heteroepitaxy on h-BN.

Graphene/(h-BN) n/X-doped graphene as anode material in lithium ion batteries (X=Li, Be, B and N)

Abstract: In this study Boron nitride sheet has been localized inside two X-graphene electrodes as an option to enhance the electrochemical ratio. Additionally, we have found the structure of X-G/(h-BN)n/X-G (N = 2–5) can improve the capacity and electrical transport in C-BN sheet-based LIBs. Therefore, the modification of BN sheets and design of X-G/ (h-BN)n/X-G structure provide strategies for improving the performance of BN-G-based anodes. X-G/(h-BN)n/X-G could also be assembled into free- standing electrodes without any binder or current collector, which will lead to increased specific energy density for the overall battery design. In this work the measured reversible lithium ion capacities of X-G//(h-BN)//X-G (X = Be, B, N) based anodes are considerably improved compared to the conventional graphite-based anodes

Force constants of BN, SiC, AlN and GaN sheets through discrete homogenization

The force constants related to the bond stretching and angular variation of boron nitride, silicon carbide, aluminium nitride and gallium nitride nanosheets are directly evaluated from ab-initio reference solutions of the Young’s modulus and the Poisson’s ratio. To this end, the analytical expressions of the elastic constants of a generic monolayer hexagonal diatomic sheet are derived, starting from its sticks-and-springs molecular mechanics model, through proper tools of the homogenization of periodic discrete media. Numerical benchmark assessments are given.

Electronic and transport properties of 2H1−x1Tx MoS2 hybrid structure: A first-principle study

The impure 1T phase (mixed with 2H phase) MoS2 electrodes adopted in 2H phase MoS2-based Field effect transistors (FETs) has been demonstrated efficiently decreasing the contact resistance in recent experiment. Here, first principles calculations are carried out to reveal the electronic and transport properties of the hybrid electrode 2H1−x1Tx MoS2 with different 1T compositions. Our calculated results show that the stability of hybrid 2H1−x1Tx MoS2 system is decreased as increasing the concentration of 1T phase. The band gaps are largely reduced as introducing 1T phase to 2H phase MoS2. The occurrence of flat band around the Fermi level of the hybrid 2H1−x1Tx MoS2 system is not beneficial for the electronic transport. Different transmission performances of each configuration indicate that transmission probabilities are not only subjected to the concentration of 1T phase, but also depending on the specific arrangement of the two phase structure. It is found that binding energies of O2 molecule adsorbed on the phase boundaries of the hybrid 2H1−x1Tx MoS2 is enlarged compared with that on pure 2H and 1T MoS2, accompanying with charge transfer from the substrate to adsorbate. To protect the hybrid 2H1−x1Tx MoS2 state from molecule adsorption, we predict that BN sheet can be used as an effective encapsulating material.

First-principle study of graphyne-like BN sheet: Electronic structure and optical properties

The stability, electronic and optical properties of α-, β-, γ- and 6,6,12-graphyne-like BN sheets (labeled as BNyne) are systematically investigated by the first-principles calculations based on density functional theory (DFT). The combination of phonon dispersions and Molecular Dynamic (MD) reveals that these four BNynes are stable. All the BNynes structures are direct wide band gap semiconductor. As for optical properties, the dielectric function ε(ω), absorption coefficient α(ω), reflectivity R(ω) and the refractive index n(ω) were investigated using the electric field vector both perpendicular and parallel to the sheet. All of these four kinds of BNynes show remarkable anisotropic behaviors in a quite wide energy range and reveal a strong optical response in wide ultraviolet. Also, the reflectivities are very weak for all the BNynes. All of these properties indicated that BNyne sheets maybe potential short-wavelength optoelectronic device and UV-light protection materials.

Boosting the adsorption performance of BN nanosheet as an anode of Na-ion batteries: DFT studies

Despite the high advance in the Li-ion battery technology, there exist great concerns about its lifetime, safety, cost, and low-temperature performance. It is expected that the Li-ion batteries may be replaced by Na-ion batteries (NIB) because of the low cost, nontoxicity, and wide availability of sodium. Here, we investigated the potential application of BN nanosheets in anode of NIBs by means of density functional theory calculation and introduced a strategy to increase their performance. It was shown that the Na and Na+ are mainly adsorbed on the center of a hexagonal ring of BN sheet with adsorption energies of −0.08 and −33.7 kcal/mol, respectively. Replacing three N atoms of the hexagonal ring with larger P atoms significantly increases the performance of the sheet as an anode of a NIB but the replacement of B by Al decreases the performance. The initial cell voltage of LIB is increased by about 0.67 V after the P-doping which causes a high storage performance with long discharge time. The results are discussed based on the energetic, structural, orbital, charge transfer and electronic properties and provide guidelines to build better high-capacity anode materials for NIBs.

Cyclosarin nerve agent interaction with the pristine, Stone Wales defected, and Si-doped BN nanosheets: Theoretical study

Never agent identification and disposal is vital for both civilian and military defense resources. Herein, using density functional theory calculations, the reactivity and electronic sensitivity of pristine, Stone Wales (SW) defected, and Si-doped BN (Si-BN) nanosheets toward cyclosarin nerve agent were investigated. It was found that the interaction of cyclosarin with the pristine BN sheet is very weak and also that is not energetically favorable with SW defected one. Unlike the SW defect, replacing a B atom by Si atom significantly makes the cyclosarin adsorption energetically favorable. Calculations show that the carbonyl and etheric oxygen atoms of cyclosarin attack the Si atom of Si-BN with the adsorption energies of −73.5 and −136.9kJ/mol, respectively. The cyclosarin nerve agent can be decomposed by the Si-BN sheet which is thermodynamically highly favorable. Upon this process, the HOMO and LUMO levels are significantly unstabilized and the HOMO-LUMO gap significantly changed by about 24.2%. The cyclosarin presence and its decomposition by Si-BN sheet can be recognized because of the electrical conductivity change of the sheet.

N과 AlN 시트에 다양한 기체(COx, NOx, SOx)의 흡착에 관한 이론 연구

N과 AlN 시트에 다양한 기체(CO_x, NO_x, SO_x)의 흡착에 관한 이론 연구

A Density functional theory study of the sensitivity of two-dimensional BN nanosheet to nerve agents cyclosarin and tabun

We investigated the reactivity and sensitivity of pristine, and Al-doped boron nitride (Al-BN) nanosheets to nerve agents including cyclosarin (GF) and tabun (GA) by means of density functional calculations. A weak interaction is predicted for both GF and GA with the pristine BN sheet with adsorption energies of −12.0 and −10.9kcal/mol, respectively. Calculations show that the carbonyl oxygen atom of both GF and GA are the most nucleophile active site. The electronic sensitivity of the BN nanosheet is predicted to be negligible to these nerve agents. To overcome this problem, we have replaced a B atom of the sheet by an Al atom and investigated the adsorption process. It was found that the reactivity of the sheet in significantly increased to these agents after the Al-doping while the electronic sensitivity is improved only for GA gas. By adsorbing the GA on the Al-BN, its electrical conductivity is largely increased because of a decrease about 32.6% in the HOMO-LUMO energy gap. We have concluded that the Al-doping process helps the BN sheet to detect the GA gas and may be used in its sensor devices.

Most effective way to improve the hydrogen storage abilities of Na-decorated BN sheets: applying external biaxial strain and an electric field.

Density functional calculations were used to investigate the hydrogen storage abilities of Na-atoms-decorated BN sheets under both external biaxial strain and a vertical electric field. The Na atom generally has the weakest binding strength to a given substrate compared with the other elements in the periodic table [PANS, 2016, 113, 3735]. Consequently, it is understudied in comparison to other elements and there are few reports about the hydrogen storage abilities of Na-decorated nanomaterials. We calculated that the average binding energy (Eb) of Na atoms to the pure BN sheet is 1.08 eV, which is smaller than the cohesive energy of bulk Na (1.11 eV). However, the Eb can be increased to 1.15 eV under 15% biaxial strain, and further up to 1.53 eV with the control of both 15% biaxial strain and a 5.14 V nm-1 electric field (E-field). Therefore, the application of biaxial strain and an external upward E-field can prevent clustering of the Na atoms on the surface of a BN sheet, which is crucial for the hydrogen storage. Each Na atom on the surface of a BN sheet can adsorb only one H2 molecule when no strain or E-field is applied; however, the absorption increases to five H2 molecules under 15% biaxial strain and six H2 molecules under both 15% biaxial strain combined with a 5.14 V nm-1E-field. The average adsorption energies for H2 of BN-(Na-mH2) (m = 1-6) are within the range of practical applications (0.2-0.6 eV). The hydrogen gravimetric density of the periodic BN-(Na-6H2)4 structure is 9 wt%, which exceeds the 5.5 wt% value that should be met by 2017 as specified by the US Department of Energy. On the other side, removal of the biaxial strain and E-field can help to desorb the H2 molecule. These findings suggest a new route to design hydrogen storage materials under near-ambient conditions.