Borophene Sheet Research Articles

Enhanced near-field radiative heat transfer between borophene sheets on different substrates

Abstract Near-field radiative heat transfer (NFRHT) has the potential to exceed the blackbody limit by several orders of magnitude, offering significant opportunities for energy harvesting. In this study, we have examined the NFRHT between two borophene sheets through the calculation of heat transfer coefficient (HTC). Due to the tunneling of evanescent waves, borophene sheet allows for enhanced heat flux and adjustable NFRHT by varying its electron density and electron relaxation time. Additionally, the near field coupling is further examined when the borophene is deposited on dielectric or lossy substrates. The maximum HTC is closely related to the real part of the dielectric substrate. As a case study, the HTC on the lossy substrate of MoO3, ZnSe and SiC are calculated for comparison. Our results indicate that MoO3 is the optimal substrate to get the enhanced energy transfer coefficient. It results in a remarkable value of 1737 times higher than the blackbody limit owing to the enhanced photon tunneling probability. Thus, our study reveals the effect of substrate on the HTC between borophene sheets and provides a theoretical guidance for the design of near-field thermal radiation devices.

Flat-band Friedrich-Wintgen bound states in the continuum based on borophene metamaterials.

Many applications involve the phenomenon of a material absorbing electromagnetic radiation. By exploiting wave interference, the efficiency of absorption can be significantly enhanced. Here, we propose Friedrich-Wintgen bound states in the continuum (F-W BICs) based on borophene metamaterials to realize coherent perfect absorption with a dual-band absorption peak in commercially important communication bands. Metamaterials consist of borophene gratings and a borophene sheet that can simultaneously support a Fabry-Perot plasmon resonance and a guided plasmon mode. The formation and dynamic modulation of the F-W BIC can be achieved by adjusting the width or carrier density of the borophene grating, while the strong coupling leads to the anti-crossover behavior of the absorption spectrum. Due to the weak angular dispersion originating from the intrinsic flat-band characteristic of the deep sub-wavelength periodic structure, the proposed plasmonic system exhibits almost no change in wavelength and absorption at large incident angles (within 70 degrees). In addition, we employ the temporal coupled-mode theory including near- and far-field coupling to obtain strong critical coupling, successfully achieve coherent perfect absorption, and can realize the absorption switch by changing the phase difference between the two coherent beams. Our findings can offer theoretical support for absorber design and all-optical tuning.

Electrodialysis desalination: Borophene membrane for ion separation using non-equilibrium molecular dynamics

Utilizing non-equilibrium molecular dynamics simulations, we examined the ion separation facilitated by an electric field through a borophene sheet with pores. This research was inspired by the potential use of such a system in membrane-driven desalination of sea and ocean waters. Our findings indicate a marked improvement in separating both negative and positive ions from water, contingent upon electric field strength and the radius of the membrane pore. Notably, beyond a specific pore radius, this enhancement reaches a saturation point. The results highlight the potential of a high-efficiency system for producing fresh water from saline sources, emphasizing the synergistic effect of membrane porosity and the strength of the applied electric field.

Multi-doped borophene catalysts with engineered defects for CO2 reduction: A DFT study

Carbon dioxide reduction reaction (CO2RR) to convert carbon dioxide (CO2) into value-added products via the electrochemical method is a conducive way to tackle the hazard of high CO2 emissions. The present DFT study reports a novel dual chromium-anchored tri-vacancy borophene (Cr2/TV-β12) electrocatalyst, which showed high selectivity and stability for CO2RR. A tri-vacancy defect was introduced in β12 borophene to create an 11-membered ring borophene sheet (TV-β12), and 28 different electrocatalysts were explored via doping various transition metals (Co, Cr, Cu, Fe, Mn, Ni, Zn). Density functional theory simulation results revealed that the Cr2/TV-β12 electrocatalyst adsorbs and activates CO2 efficiently, which was validated by the partial density of states, charge density difference, Bader charge, and crystal orbital Hamilton population analyses. The limiting potential for CO2RR was evaluated to be −0.45 V, against hydrogen evolution reaction (HER) (0.57 V), with the main product being formaldehyde. The catalyst showed selectivity towards CO2 reduction and suppressed HER. The usual problem of carbon monoxide poisoning encountered in CO2 reduction was also assessed and a high resistance against the same was established. At the outset, the research revealed that dual atom-doped tri-vacancy β12 borophene has tremendous potential to be utilized as an efficient catalyst for CO2RR.

Prediction and simulation of mechanical properties of borophene-reinforced epoxy nanocomposites using molecular dynamics and FEA

Abstract The purpose of this work is to predict the mechanical properties of single- to few-layered borophene (η-LB)/epoxy composites using molecular dynamics modelling. An epoxy matrix was used to hold borophene in layers, and a borophene sheet was homogeneously incorporated into the epoxy matrix to generate borophene/epoxy nanocomposites. In this work, the mechanical properties of borophene/epoxy nanocomposites have been analysed in further detail. In addition to the mechanical properties of the nanocomposites, the impacts of borophene on the density distribution of epoxy polymers in the nanocomposites led to the observation that the local density is relatively high near the borophene–β12 interface and gradually declines to the bulk value as one advances away from the interface. The mechanical properties of the borophene-layered nanocomposites were superior to those of their substitutes, with the former having a higher Young’s modulus and a lower thermal expansion coefficient. This is due to the fact that borophene layer loading may result in a significant quantity of high-density polymer being present in the nanocomposites, which enhances the overall properties of the nanocomposites. In addition, the interaction between the three to four layers of loaded borophene layer provides the greatest reinforcement among the two nanocomposites systems. Finite element analysis analyses on the preferred results of the β12 LB were in excellent agreement with those of the experimental simulation data, demonstrating that this computational technique may be used to reliably predict the characteristics of borophene/epoxy composites in the future.

Single B-vacancy enriched α1-borophene sheet: an efficient metal-free electrocatalyst for CO2 reduction.

By employing first principles calculations, we have studied the electronic structures of pristine (α1) and different defective (α1-t1, α1-t2) borophene sheets to understand the efficacy of such systems as metal-free electrocatalysts for the CO2 reduction reaction. Among the three studied systems, only α1-t1, the defective borophene sheet created by removal of a 5-coordinated boron atom, can chemisorb and activate a CO2 molecule for its subsequent reduction processes, leading to different C1 chemicals, followed by selective conversion into C2 products by multiple proton coupled electron transfer steps. The computed onset potentials for the C1 chemicals such as CH3OH and CH4 are low enough. On the other hand, in the case of the C2 reduction process, the C-C coupling barrier is only 0.80 eV in the solvent phase which produces CH3CHO and CH3CH2OH with very low onset potential values of -0.21 and -0.24 V, respectively, suppressing the competing hydrogen evolution reaction.

An investigation of halogen induced improvement of β12 borophene for Na/Li storage by density functional theory

Pristine and halogen doped β12 borophene, as anode of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), was considered by first-principles study based on density functional theory. Li and Na were adsorbed on β12 borophene with adsorption energies of −3.18 eV and −2.33 eV, respectively. The effect of halogen addition, X = F, Cl, Br, and I, to borophene sheet on adsorption and also diffusion pathways of Li and Na was studied. The adsorption energy calculations show that the halogen atoms improve Li/Na adsorption on borophene sheet. Also, the results indicate that Li/Na adsorption energies on Brominated borophene sheet are higher compared to other halogen types. Diffusion calculations show that Br addition induces an electron deficiency on BoBr surface which lowers the energy barrier of migration of Li and Na ions compared to the pristine borophene. According to density of states analysis, electron charge is transferred from Li and Na atoms toward halogenated borophene sheet. Also, it can be concluded that electron transfer from Li/Na to borophene host in BoX is higher compared to pristine borophene which is in agreement with adsorption energies. The fully lithiated/sodiated complexes of BoBr are Li0.71BoBr and Na0.50BoBr which is equivalent to theoretical specific capacities of 1401 and 981 mAh/g which are about 3.5 and 2.6 times higher than graphite for Li and Na adsorption, respectively. Higher specific capacity of Li compared to Na is mainly attributed to steric hindrance of Na regarding its greater size. Open circuit voltage values of 1.6 V and 1.4 V were obtained for Li and Na intercalation processes, respectively, into halogen added β12 borophene indicating that this structure can be applied as anode for both LIB and SIB systems.

Tunable narrow transparency windows induced by the coupled quasi-guided modes in borophene plasmonic nanostructure

A grating-assisted triple-layer continuous borophene sheets structure is presented to investigate the phase-coupled plasmon-induced transparency (PIT) effect at the near-infrared communication band. In the proposed structure, the diffraction grating is utilized to couple the normal incident waves, which excites the quasi-guided mode in triple-layer continuous borophene sheets. Compared to the patterned structure, the requirement of complicated processing techniques and extra doping configurations for tuning carrier density can be avoided by using the continuous borophene sheet. Additionally, the narrower transparency windows are shown in the spectral responses via the phase coupling between two detuned quasi-guided modes with high quality factors. The transparency windows can be efficiently tuned by adjusting the carrier densities in borophene sheets or the separation distances between the borophene sheets. The analytical results based on temporal coupled mode theory and transfer matrix method are consistent with the numerical simulations via finite-difference time-domain calculations. The proposed scheme provides the promising design of a tunable PIT component that is compatible with optical communication technology.

Application of borophene as catechol sensor: a computational study.

The efficacy of borophene (BP) as catechol (CC) sensor was explored using density functional theory (DFT) method. All calculations were performed at B3LYP level of theory and 6-31 + G(d) basis set employing the dispersion correction term of Grimme to consider dispersion interactions. The CC molecule is adsorbed on top of BP horizontally with the adsorption energy (Eads) of about - 13.5kcal·mol-1. The HOMO and LUMO levels of nanosheet destabilize by about 0.36 and 0.14eV, respectively, going from bare BP to BP-CC complex. Therefore, the Eg value decreases by about 10.5% upon adsorption process, which is a reasonable energy gap change for detection of CC. The negligible difference between the work function values (Φ, defined as the minimum amount of the energy needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface) of BP and its complex with CC indicates that the BP sheet is not an appropriate Φ-type sensor (in these sensors, adsorption of a chemical changes the gate voltage and produces an electrical signal that leads to the detection of chemical agent) for CC detection. The electrical conductivity of BP becomes 72 times higher after CC adsorption. The time needed for CC desorption from BP sheet is 7.6ns, based on conventional transition state theory, showing that BP benefits from a short recovery time. The effect of CC concentration was explored by adsorption of 2 and 3 CC molecules on top of BP nanosheet and the results showed that the sensor response does not change by increasing the CC concentration. Also, the effect of lateral dimensions of BP on the adsorption energy was explored and it was shown that Eads increases by enlargement of the nanosheet.

Ab-initio and Monte Carlo study of Fe-based two-dimensional magnets at borophene supported by Ag(111) surface

Two-dimensional (2D) magnetic crystals are ideal platforms for the employment of simple physical models in the exploration of magnetism in a 2D limit. Instead of examining 2D van der Waals materials, the focus of our study is on adatoms that carry intrinsic magnetic moments and are assembled into 2D arrays at a suitable surface. We applied density functional theory (DFT) to investigate Fe nanostructures formed on a borophene sheet deposited at Ag(111) surface and identified stable Fe-based 2D magnets formed either on top of the borophene or at the interface between the borophene and Ag(111) surface. The structures are composed of close-packed Fe wires, featuring ferromagnetism within the chain and the interchain antiferromagnetic coupling. Exchange- and single-ion anisotropy constants extracted from DFT calculations are used to describe these systems with the classical Ising and Heisenberg models. The corresponding Monte Carlo simulations revealed finite temperature magnetic ordering, with the estimates of critical temperatures of 105 and 30 K derived from the anisotropic Heisenberg model, for the Fe-based magnets grown above and under borophene, respectively.

Contact strength and deformation of straining free-standing borophene

We apply nanoindentation using molecular dynamics simulation to investigate the contact strength, deformation behaviour, anisotropic cracking propagation and self-reforming mechanism of a single-layer borophene (SLB). The effects of indenter shape, indenter size, borophene membrane size, boundary conditions, temperature, and loading rate on the indentation force, strain and stress distributions, crack directions, and the self-reform ratio of SLB are considered. Especially a cyclic indentation process on the borophene monolayer is also analysed to evaluate its long-term dynamic reliability. The single/multi loading–unloading processes show that the SLB has a perfect elastic deformation when the indentation depth is below or equal to the critical indentation depth. We found that the crack direction is not influenced when changing spherical indenter diameter from 1 to 4 nm or loading rate from 1 to 15 m/s. However, with a conical indenter, the smallest substrate size, and FTE(y) boundary condition, the cracks develop not only in the armchair direction but also in the zigzag direction. Furthermore, the borophene sheet has a high self-reform ratio of 90% (with v = 15 m/s) after being cracked along the armchair direction. Meanwhile, the cracks in the zigzag direction have no possibility of self-reform. At 100 K, after the tenth cycle indentation, the borophene sheet can still preserve its shape while it is broken at 300 K. In summary, this study further highlights the mechanical, long-term dynamic behaviour and potentially speeds up the promising applications of the SLB.

Half-Auxeticity and Anisotropic Transport in Pd Decorated Two-Dimensional Boron Sheets.

Upon strain, most materials shrink normal to the direction of applied strain. Similarly, if a material is compressed, it will expand in the direction orthogonal to the pressure. Few materials, those of negative Poisson ratio, show the opposite behavior. Here, we show an unprecedented feature, a material that expands normal to the direction of stress, regardless if it is strained or compressed. Such behavior, namely, half-auxeticity, is demonstrated for a borophene sheet stabilized by decorating Pd atoms. We explore Pd-decorated borophene, identify three stable phases of which one has this peculiar property of half auxeticity. After carefully analyzing stability and mechanical and electronic properties we explore the origin of this very uncommon behavior and identify it as a structural feature that may also be employed to design further 2D nanomaterials.

First principles details into the grafting of aryl radicals onto the free-standing and borophene/Ag(1 1 1) surfaces

We suspect that a possible interaction of the aryl radicals with the borophene surface is important for the stabilization and functionalization of the surface. Therefore, the grafting of aryl radical onto the borophene film is investigated using first-principles calculations based on density functional theory. The binding energy of the phenyl radicals on the borophene sheet, population analysis, and electron energy difference studies indicate a covalent nature of the bond between the B atom of the borophene and the C atom of the phenyl radical. Electron localization function analysis (ELF) is applied to estimate the nature of the bond between the borophene and the grafted phenyl moiety. The Mulliken charge population is used to evaluate the possible electron transfer at the bond-forming atoms (B and C) during this process. The obtained results helped to shed light on the grafting mechanism, activation energy, stabilization, and nature of the formed chemical bond between borophene and para-substituted phenyl moieties.

A first-principle study of FeB6 monolayer as a potential anode material for Li-ion and Na-ion batteries

Two-dimensional (2D) graphene-like hexagonal borophene sheet (HBS) is a kinetically unstable configuration since the electrons of π-valence orbitals of HBS are less than those of graphene. Inspired by the planar hexacoordinate wheel-type Fe©B6H6, we theoretically designed a novel 2D material FeB6 where the HBS can be stabilized by Fe atoms located at the center of partial boron rings. Moreover, we also investigated the possibility of using FeB6 monolayer as a potential anode for Li-ion batteries (LIBs) and Na-ion batteries (NIBs). Our calculations showed that FeB6 monolayer had strong adsorption energies (2.89 eV for Li and 2.39 eV for Na), low diffusion barriers (0.24 eV for Li and 0.10 eV for Na) and high theoretical specific capacities (991 mAh/g for Li and 622 mAh/g for Na), which indicates that FeB6 monolayer can be a potential anode material for LIBs/NIBs.

Three-Fold Enhancement of In-Plane Thermal Conductivity of Borophene through Metallic Atom Intercalation

We studied the thermal conductivity of Al-intercalated bilayer δ4 borophene sheet by solving phonon Boltzmann transport equation based on density functional theory. Although the overall atomic density of Al-intercalated borophene is larger than that of δ4 borophene, it possesses significant enhancement in in-plane thermal conductivity. With metallic atom intercalation, the armchair-direction thermal conductivity increases from 53.8 to 160.2 Wm-1K-1, and that along zigzag direction increases from 115.7 to 157.2 Wm-1K-1, respectively. This pronounced enhancement is attributed to the bunching of the acoustic branches in the Al-intercalated borophene, which decreases the phase space for the high frequency three acoustic phonons scattering processes. In addition to the pronounced increased thermal conductivity, the Al-intercalation also tune the in-plane anisotropy. This study illustrates the importance of metallic atom intercalation in the in-plane thermal conductivity of 2D van der Waals materials, and also has practical implications for fields ranging from thermal management to thermoelectrics design.

Nitrogen-decorated borophene: An empowering contestant for hydrogen storage

Hydrogen (H2) being, pure source of energy with high energy capacity is an excellent candidate for the energy future resource. In this study, we systematically investigate the H2storage capacity of pristine, nitrogen (N)-decorated and N-doped borophene sheets by means of first-principles calculations based on density functional theory (DFT).Semi-empirical dispersion correction (D2) has also been incorporated in all calculations for the consideration of the long-range interaction. The adsorption site, adsorption energy, electronic structure, charge transfer and hydrogen storage performance of pristine, N-decorated and N-doped borophenesheets are discussed in detail. N atom binds strongly with borophene sheet without the issue of clustering. The decoration of N atom significantly enhances the H2 adsorption strength of borophene sheet compared to the pristine one. Further insight into the interaction of H2 with considered systems is elaborated by calculating projected density of states (PDOS) and charge density plots. Our calculation shows that N-doped and N-decorated borophene sheets achieve 1.51 wt% and 6.22 wt% gravimetric density, respectively for the H2 storage.

Metallic and intra-band investigation of optical properties for Borophene nano-sheet: a DFT study

In this paper, using the density functional theory framework with the FP-LAPW + lo method by GGA approximation, the electronic and optical properties such as band structure, density of states, dielectric function, energy loss function, absorption and reflection have been investigated for borophene nano-sheet. The optical properties of the borophene have been changed as the incident light direction whereas has the metallic and semiconductor behavior, in the borophene sheet and perpendicular light angles, respectively. Therefore, it can be said that the optical properties of this material are anisotropic.

Effect of point defects and functionalization on structural stability and electron properties of borophene as investigated by means of density functional theory

The discovery of a new two dimensional material is a new trend emerged after the discovery of graphene in 2004. Hundreds of new materials have been predicted, designed and investigated during last decade. Many of them have outstanding properties for potential application in new technologies. One of those materials is so-called borophene, being isolated atomically thin boron. This material can show different electronic properties, including semiconducting, semi-metallic, and metallic states due to its unique structure. Borophene demonstrates unusually high in-plane elasticity and strength. The crucial point for application of borophene is its low structural stability at room temperature. A possible way to solve this problem is the functionalization of its surface by external atoms like hydrogen and fluorine. This work presents a study on the effect of O dopants and the presence of vacancy defects on electronic properties of borophene by using first-principles calculations. It was revealed that unlike other 2D materials, the band structure of borophene is stable by respect to the above-mentioned factors. However, the doping by O atoms is found as an effective way to increase the stability of the borophene sheet.

Enhancing gas adsorption properties of borophene by embedding transition metals

Synthesis of two dimensional (2D) monolayer of boron, called borophene has added a new potential material. We explore the gas adsorption properties of borophene by performing a series of first principles calculations using density functional theory (DFT). The generalized gradient approximation (GGA) as parameterized by Perdew-Burke-Ernzerhof (PBE) is employed in the form of exchange correlation functional. Gas adsorption properties of borophene have been investigated in terms of adsorption energy of adsorbed gas (CO, NO, CO2, NO2, H2S, and NH3) molecules. Calculated negative value of adsorption energy indicates strong adsorbing feature. Further, to enhance gas adsorption property, transition metal (TM) atom has been embedded into borophene. Interestingly, the adsorption energies for TM embedded borophene were predicted lower in comparison to pure borophene thus improves gas adsorption properties. We have predicted that physisorption process followed by gases while adsorbing over borophene sheet. To understand bonding between borophene and adsorbed gas molecules, Bader charge calculations have been performed. The incorporation of TM atoms introduce magnetic character into borophene. Our theoretical predictions may motivate experimentalists to grow borophene based gas sensors and spintronic devices.

Solid-state platform for space-time engineering: The 8Pmmn borophene sheet

We construct the most generic Hamiltonian of the $8Pmmn$ structure of borophene sheet in presence of spin-orbit, as well as background electric and magnetic fields. In addition to spin and valley Hall effects, this structure offers a framework to conveniently manipulate the resulting "tilt" of the Dirac equation by applying appropriate electric fields. Therefore, the tilt can be made space-, as well as time-dependent. The border separating the low-field region with under-tilted Dirac fermions from the high-field region with over-tilted Dirac fermions will correspond to a black-hole horizon. In this way, space-time dependent electric fields can be used to design the metric of the resulting space-time felt by electrons and holes satisfying the tilted Dirac equation. Our platform offers a way to generate analogues of gravitational waves by electric fields (instead of mass sources) which can be detected in solid state spectroscopies as waves of enhanced superconducting correlations.