Honeycomb Borophene Research Articles

High‐Entropy‐Stabilized Platinum Diborides for Poison‐Resistant Catalysis

AbstractAlloying and solid‐solution formation is a powerful technique that enhances and adds properties through elemental mixing, but unfortunately, some elements simply cannot mix as their chemical nature prevents a thermodynamically stable structure. For example, the inherent nobility of platinum group metals does not favor bond formation and precludes their incorporation into higher (boron‐rich) metal borides. However, we demonstrate that when using five or more constituents, the higher mixing entropy will overcome these chemical limitations and form a stable high‐entropy alloy, demonstrating the formation of new compounds with substituents that are seemingly impossible with a traditional metal alloying approach. The high‐entropy boride (HEB) Al0.2Nb0.2Pt0.2Ta0.2Ti0.2B2 was synthesized, where platinum was forced to occupy a 12‐coordinate site, sandwiched between honeycomb borophene sheets. In addition to the unusual coordination, the boron serves as a poison panacea. Pure platinum is strongly susceptible to sulfur poisoning by adsorption, rendering a platinum catalyst ineffective. Boron is known to be resistant to sulfur poisoning. The boron sheets present in the HEB shield the platinum from sulfur while maintaining high catalytic activity. This is confirmed with the facile hydrogenation of thiol‐containing nitro compounds, where the HEB resists sulfur poisoning while retaining its high catalytic activity.

Unraveling the enhanced sodium-storage mechanism in a strongly bonded 2D honeycomb borophene/boron phosphide heterostructure

The growing modern demand for battery capacity is driving the development of high-capacity metal-ion battery anodes for future energy storage. Two-dimensional (2D) material-based heterostructures have shown advantages as alternative anodes due to their enhanced adsorption capacity. The lightweight nature of honeycomb borophene (HB) is beneficial for serving as a high-capacity anode but is constrained by structural instability arising from electron deficiency. In this study, using first-principles calculations, we propose a HB/boron phosphide (BP) heterostructure as an anode for both lithium-ion batteries and sodium-ion batteries (SIBs). The heterostructure engineering not only stabilizes the HB structure but also leads to a bonding heterostructure instead of common van der Walls type. The HB/BP demonstrates robust structural stability and reversibility when multiple ions are stored. In addition, the HB/BP offers stable storage sites and low diffusion barriers for lithium (0.31 eV) and sodium (0.28 eV), indicating rapid charging–discharging performance. Notably, the predicted maximum sodium storage capacity reaches 2402 mAh/g, surpassing that of the constituent monolayers and most 2D heterostructures. The underlying mechanism for high storage capacity is elucidated through detailed charge image model analysis, offering atomistic-scale insights for constructing high-capacity anodes. All results suggest that the presented HB/BP is a promising anode candidate for SIBs and opens an avenue for stabilizing HB in energy storage.

Borophene–MXene heterostructures as supercapacitor

We report the electrochemical characteristics of honeycomb borophene (HB) heterostructure with various MXenes, including Ti3C2O2, Ti3C2F2, and Ti3C2(OH)2. The stability of these heterostructures is also investigated. Our approach involves utilizing joint density functional theory to merge electronic DFT with a solution model (CANDLE) for simulating immersed electrodes in a 1 M NaF electrolyte. We obtain the quantum capacitance, an essential component of total capacitance in 2D materials, as well as integral and differential capacitance. Furthermore, we determine adsorbed charges on surfaces and stored energies. Our findings demonstrate that bare HB exhibits superior performance as a supercapacitor compared to individual MXenes, and its capacity can be notably improved by integrating with Ti3C2(OH)2 by more than 30%.

Heterostructure design on honeycomb borophene/Mo2C: A novel strategy for nitrogen fixation

In terms of its ecological and sustainable nature, electrochemical nitrogen reduction reaction (e-NRR) is widely recognized as the ideal solution to replace conventional ammonia production techniques. Unfortunately, poor Faraday efficiency (FE) with lower e-NRR selectivity limits its large-scale application. Previous studies have identified Mo2C as an optimistic electrocatalyst for e-NRR, exhibiting great ammonia yield. However, Mo2C suffers from Mo leaching during the electrochemical reaction process, thus reducing the stability of the catalyst. Herein, we propose a new electrocatalyst based on first-principles calculations: HB/α-Mo2C. This heterostructure is composed of Mo2C covered with a layer of Honeycomb Borophene (HB). The HB layer serves two purposes: to ensure the stability of the catalyst and improve the FE of the reaction. Our findings demonstrate the HB/α-Mo2C performs the highest catalytic activity via a mixed mechanism with a limiting potential as low as -0.16 V, which was determined to be caused by the transfer of electrons from the active sites of the boron atoms to the adsorbate. Furthermore, the limiting potential of HER, a competing reaction, was found to be as high as −0.56 V, confirming the high efficiency of HB/α-Mo2C towards e-NRR. This present work contributes to the development of new strategies for e-NRR catalyst design.

First-principles calculations of the structural and optoelectronic properties of honeycomb borophene: strain and many-body effects

First-principles calculations of the structural and optoelectronic properties of honeycomb borophene: strain and many-body effects

Heterogeneous-Structured Molybdenum Diboride as a Novel and Promising Anode for Lithium-Ion Batteries.

With the development of electric vehicles, exploiting anode materials with high capacity and fast charging capability is an urgent requirement for lithium-ion batteries (LIBs). Borophene, with the merits of high capacity, high electronic conductivity and fast diffusion kinetics, holds great potential as anode for LIBs. However, it is difficult to fabricate for the intrinsic electron-deficiency of boron atom. Herein, heterogeneous-structured MoB2 (h-MoB2) with amorphous shell and crystalline core, is prepared by solid phase molten salt method. As demonstrated, crystalline core can encapsulate the honeycomb borophene within two adjacent Mo atoms, and amorphous shell can accommodate more lithium ions to strengthen the lithium storage capacity and diffusion kinetics. According to theoretical calculations, the lithium adsorption energy in MoB2 is about -2.7 eV, and the lithium diffusion energy barrier in MoB2 is calculated to be 0.199 eV, guaranteeing the enhanced adsorption capability and fast diffusion kinetic behavior of Li+ ions. As a result, h-MoB2 anode presents high capacity of 798 mAh g-1 at 0.1 A g-1, excellent rate performance of 183 mAh g-1 at 5 A g-1 and long-term cyclic stability for 1200 cycles. This work may inspire ideas for the fabrication of borophene analogs and two-dimensional metal borides.

Seeking borophene on Ni3Al(111): an experimental characterization of boron segregation and oxidation

Synthesis of a stable, well ordered honeycomb borophene (hB) phase has been achieved to date by exploiting Al(111) as a growth substrate, which provides the necessary charge doping to compensate the high hexagonal-holes density. However, B/Al(111) is governed by a strong B–Al interaction so to yield the actual formation of an AlB2 hB phase. Dilution of aluminum by alloying could then in principle weaken the boron-support bonding. By means of a combined spectroscopy and microscopy experimental approach, we find instead that the growth of boron layers on the Ni3Al(111) alloy termination is driven by B dissolution into the bulk and surface segregation mechanisms. While no long-range ordered boron-induced phase is observed, locally ordered superstructural units with triangular appearance are stabilized by substrate pinning, following the chemical p(2 × 2) surface order. Oxidation involves both boron and aluminum, inducing surface segregation of B, while nickel remains in its metallic form.

Attraction-Induced superlubricity and its detection

A nanoscale friction test using an atomic force microscope (AFM) is modelled as a diatomic tip in sliding contact with a 2D monolayer supported by a metal substrate. This test is simulated by ab initio DFT calculations. The simulation results show that, when a silver tip slides on a honeycomb borophene (HB) monolayer supported by a titanium substrate, the friction force varies nonlinearly with the prescribed height of the tip or, equivalently, the corresponding normal force exerted by the tip on the HB monolayer. In particular, the friction force turns out to be almost null when the height of the tip sufficiently approaches a critical height of the prescribed height, which corresponds to a critical normal attraction force. This nanoscale friction-free sliding phenomenon is thus qualified as attraction-induced superlubricity (AISL). Further, the origin of AISL is discussed and analyzed in terms of electron redistributions. Finally, the feasibility of AISL detection is argued by analyzing the potential energy surface (PES), the adsorption strength of the tip on HB surface and the binding strength of HB to its substrate.

Computational screening of two-dimensional substrates for stabilizing honeycomb borophene

Honeycomb borophene (hc-B) has received extensive attention due to its potential applications in energy storage, sensors, and superconductivity. However, due to the indecisive kinetic and thermodynamic stability of the freestanding hc-B, its further development is limited. To enhance the stability of hc-B, the substrates engineering is more straightforward and feasible in practice without changing the intrinsic hc-B structure. Herein, steered via first-principle calculations, we perform a computational screening of two-dimensional (2D) substrates for stabilizing the hc-B from the Computational 2D Materials Database. Consequently, we find 8 new candidates with improved stability, whose structural integrity of hc-B is well-maintained. The strong interactions between the hc-B and the substrates play a critical role in the stability enhancement, confirmed by the large binding energy and charge transfer. In addition, the preferential migration pathway of boron atoms on the substrates is restricted by the potential energy surface, benefiting the epitaxial growth of hc-B. Our results suggest that the 2D layered substrates are promising for stabilizing and growing planar hc-B structure, which may facilitate its applications in 2D fields.

Ab Initio Study of High-Capacity Hydrogen Storage in Lithium-Shrouded Honeycomb Borophene Oxide Nanosheet

Here, we investigate the hydrogen storage performance of Li alkali metal-shrouded two-dimensional (2D) honeycomb borophene oxide (h-B3O) using the Tkatchenko–Scheffler method, an accurate and parameter-free method to determine the long-range van der Waals interactions. Each Li atom can strongly bind three H2 molecules to the substrate with an average adsorption energy of −0.22 eV/H2, and the theoretical weight density of the Li-shrouded h-B3O structure can reach 9.84 wt %. In particular, a maximum hydrogen storage capacity of 12.71 wt % is achievable by moderately increasing the external pressure. Lattice thermal conductivity calculations show efficient thermal transport and good adsorption/desorption behavior of H2 molecules. Furthermore, the study of possible defects in the material showed that the hydrogen storage performance of the Li-shrouded h-B3O nanosheet is insensitive to the presence of defects in the material, which has important implications for its experimental synthesis. Our findings indicate that Li-shrouded 2D h-B3O is a promising material for reversible H2 storage.

Growing borophene on metal substrates: A theoretical study of the role of oxygen on Al(111)

Charge transfer from a metal substrate stabilizes honeycomb borophene, whose electron deficit would otherwise spoil the hexagonal order of a $\pi$-bonded 2D atomic network. However, the coupling between the substrate and the boron overlayer may result in the formation of strong chemical bonds that would compromise the electronic properties of the overlayer. In this paper we present a theoretical study, based on state-of-the-art density-functional and genetic-optimization techniques, of the electronic and structural properties of borophene grown on Al(111), with emphasis on the impact of oxygen on the strength of the coupling between substrate and overlayer. While our results confirm the formation of Al-B bonds, they also predict that oxygen doping reduces charge transfer between aluminum and borophene, thus allowing modulation of their strength and paving the way to engineering the electronic properties of 2D-supported borophene sheets for industrial applications. Our study is completed by a thorough study of the thermodynamic stability of the oxygenated borophene-Al(111) interface.

Anomalous strain-dependent charge density in honeycomb borophene

The electronic properties of honeycomb borophene under strain were investigated using first principles. The biaxial tensile strain was found to alter the interlayer interaction between the substrate layer and the sample layer, manifested as controlled by strain in a commensurate contact state intralayer and interlayer coupling strength. In addition, honeycomb borophene was found to have an anomalous strain-dependent charge density. We explain that this charge density fluctuation is determined by the electron-deficient nature of borophene itself and the change in the amount of electron injection into the borophene layer under strain. This study provides new insights into the changes in the interaction between two-dimensional materials and substrate layers under strain.

Reversible hydrogen storage for NLi4-Decorated honeycomb borophene oxide

The boron-based two-dimensional (2D) materials decorated with functional groups NLi4 has been numerically investigated for hydrogen storage via first principles calculations method. Strain-energy analysis and molecular dynamics simulations shows the pristine planar honeycomb B2O has strong mechanical and thermal stability. Crystal Orbital Hamiltonian Population analysis confirmed that there exist stronger B–B/B–O covalent bonds within B2O monolayer. In functional material, a local electric field around each lithium atom can be formed and the overall electronic structure is favorably changed for gas adsorptions. Both electrostatic forces and the van der Waals interaction are the dominant hydrogen-attached mechanisms of lithium cation. An anchored functional group NLi4 can adsorb at most 11 hydrogen molecules, and the average adsorption energy per hydrogen molecules is around −0.20 eV, indicating high hydrogen storage capacity and reversible applicability. The highest hydrogen storage capacity can reach to 9.1 wt%. The study shows the investigated material is a good candidate for hydrogen storage.

First-Principles Study of Honeycomb Borophene on the Mo2C Substrate

First-Principles Study of Honeycomb Borophene on the Mo₂C Substrate

A novel ultra-low friction heterostructure: Aluminum substrate-honeycomb borophene/graphene heterojunction

As a new type of two-dimensional material with excellent mechanical and electronic properties, borophene is worthy of discussion on its interfacial tribological behavior. We studied the tribological properties of the honeycomb borophene/graphene heterostructure attached to the Al substrate and found that this heterostructure exhibits ultra-low friction during the sliding process. Using quantitative analysis, it was found that the charge flow at the interface hindered the interlayer sliding of this heterostructure. In addition, this heterostructure can be combined with the experimental preparation of honeycomb borophene grown on an Al (111) surface, which provides feasibility analysis and guidance for experimentally realizing the ultra-low friction of this novel heterostructure.

Reversible Hydrogen Storage in Metal-Decorated Honeycomb Borophene Oxide.

Two-dimensional (2D) boron-based materials are receiving much attention as H2 storage media due to the low atomic mass of boron and the stability of decorating alkali metals on the surface, which enhance interactions with H2. This work investigates the suitability of Li, Na, and K decorations on 2D honeycomb borophene oxide (B2O) for H2 storage, using dispersion corrected density functional theory (DFT-D2). A high theoretical gravimetric density of 8.3 wt % H2 is achieved for the Li-decorated B2O structure. At saturation, each Li binds to two H2 with an average binding energy of −0.24 eV/H2. Born–Oppenheimer molecular dynamics simulations at temperatures of 100, 300, and 500 K demonstrate the stability of the Li-decorated structure and the H2 desorption behavior at different temperatures. Our findings indicate that Li-decorated 2D B2O is a promising material for reversible H2 storage and recommend experimental investigation of 2D B2O as a potential H2 storage medium.

Effect of edge contact on electronic transport in lateral Borophene/WTe2/Borophene heterojunctions

The contact between two-dimensional materials and metal plays an important role in the electronic devices. Using two dimensional metallic materials, such as borophene, to replace metal can avoid large electrode volume and possibly improve contact quality. Thus, in this work, we study the electronic transport properties of the in-plane hetorojunctions based on WTe2 and electrode materials boropheneβ12, boropheneχ3, boropheneΔ and honeycomb borophene by the first principle calculations. The different borophene structures result in different electronic structures and transport. It is found that the external electric field effectively reduces the height of Schottky barrier and induces the ohmic contact between borophene and WTe2. The results provide an insight into designing high-performance devices with electrode material borophene.

Enhanced Stability and Epitaxial Growth Mechanism of the Honeycomb Borophene Monolayer on a Two-Dimensional Ti2C Substrate

The stability enhancement mechanism of honeycomb borophene on a typical MXene material, known as Ti2C, was investigated systematically by theoretical energetic and kinetic studies. On this basis, t...

Ultra-Low Friction of Graphene/Honeycomb Borophene Heterojunction

The recently discovered and prepared honeycomb borophene is one of the many forms of borophene. For the first time, we studied the tribological properties of honeycomb borophene based on first principles and found that it has excellent tribological performance. As a two-dimensional material, honeycomb borophene has potential applications in the field of tribology. Correspondingly, we studied interlaminar charge transfer in several common heterojunctions and then explored its internal friction mechanism. The present work indicts that honeycomb borophene, a new type of two-dimensional material, may help broaden the research field of two-dimensional materials in tribology.

Ferromagnetic Dirac half-metallicity in transition metal embedded honeycomb borophene.

Exploring two-dimensional (2D) ferromagnetic materials with intrinsic Dirac half-metallicity is crucial for the development of next-generation spintronic devices. Based on first-principles calculations, here we propose a simple valence electron-counting rule to design such materials and endow them with good stability and desirable magnetic properties. Taking honeycomb borophene as a prototype, we demonstrate that embedding open-shell transition metal (like Cr) atoms in the hexagonal ring of boron atoms can provide two valence electrons to fully occupy the in-plane σ and out-of-plane π bands of B atoms. The remaining four valence electrons reside in d orbitals that split under C6v symmetry, yielding a magnetic moment of ∼2 μB per Cr atom. The resulting CrB2 monolayer exhibits a Dirac half-metal band structure, a high Curie temperature of 175 K, and a large out-of-plane magnetic anisotropy energy of 4 meV per Cr simultaneously. Our work establishes a feasible route for the experimental realization of ferromagnetic Dirac half-metallicity in 2D materials and provides new opportunity to realize high-speed devices with low consumption.