BlueP encapsulated Janus MoSSe as a promising heterostructure anode material for LIBs

In this work, the significance of BlueP-Janus MoSSe heterostructures in LIBs is explored in detail by using density functional theory calculations. The Janus MoSSe possesses two different atomic layers, and hence two different heterostructures, BlueP-SMoSe and BlueP-SeMoS, are taken into account. The heterostructure formation energies are computed to check their stability. Besides, ab initio molecular dynamics simulations and phonon studies are done to check their thermal and dynamical stabilities, respectively. The adsorption and diffusion of Li at different surfaces of both the heterostructures are calculated. Our study reveals that the heterostructures show strong Li intercalation capability with ultrafast Li diffusion barrier energies. The electronic properties of the lithiated heterointerfaces are also explored. Both the heterostructures can hold a maximum of two layers of Li ions on each side of both BlueP and MoSSe to give a large storage capacity, signifying their extraordinary potential to be appropriate as an anode material for Li-ion batteries. Additionally, due to their strong mechanical strength, the 2D BlueP-Janus MoSSe heterostructures can withstand massive volume expansion during the lithiation-delithiation reaction, which is remarkably beneficial for manufacturing flexible anodes. Based on the above findings, the newly designed heterostructures are expected to open a new avenue for the next generation of electronic devices.

Haeckelite phosphorus: an emerging 2D allotrope of phosphorus for potential use in LIBs/SIBs

A large surface-to-volume ratio is an essential feature of 2D materials used in many potential electronic applications. This work proposed that the haeckelite-structured phosphorus can be another promising alternative to the known phosphorus allotropes by DFT calculations. This allotrope can be considered a suitable anode material that may provide outstanding performance in LIBs and SIBs. Our simulations confirm that the haeckelite-structured P, composed of alternate square and octagonal rings, is thermally and mechanically stable. The phosphorus haeckelite exhibits a semiconductor with a bandgap of 2 eV and converts to a metallic phase after Li/Na adsorption, which is profoundly the basis for ideal performance of a battery. It provides a high specific capacity and a small OCV with a minimal volume expansion during lithiation/sodiation. The haeckelite-structured P exhibits much higher Li/Na adsorption properties with a small Li/Na migration barrier, which are highly essential in the charge-discharge performance of LIBs/SIBs. Based on the details mentioned above, our study would supply supportive guidelines to advance better opportunities to design and develop flexible Li/Na-ion batteries for future energy conversion and storage applications.

Adsorption and diffusion of magnesium on nitrogen-doped Mo2C monolayer

The Mg adsorption and diffusion behaviors on nitrogen-doped (N-doped) Mo₂C monolayer have been investigated by the first principles based on density functional theory (DFT). To investigate the effect of nitrogen concentration on adsorption energies, Mo₂C_1-xN_x (x=0.0625, 0.125, 0.1875, and 0.25) with four different nitrogen doping concentrations have been considered in the present work. The results show that N-doped Mo₂C is benefit for Mg adsorption. In particular, when the doping concentration reaches to 14.29%, the adsorption energies of Mg on Mo₂C_0.875N_0.125 are in the region between -1.639 and -1.517 eV, e.g., the adsorption energies of Mg on T_C1 and H₂ sites are -1.639 eV and -1.625 eV, which are decreased by 16.49% and 18.43% as compared with the pristine Mo₂C. The calculations on diffusion behaviors show that the Mg diffusing between two adjacent favored sites via a high-symmetry site along H₃-B-H₄ and H₁-B-H₁ paths possesses the barriers of 0.021 eV and 0.028 eV. Additionally, the partial density of states (PDOS) reveals the interaction between Mg and Mo₂C_0.875N_0.125, and indicates that nitrogen doping causes the PDOS peaks transfer to a lower energy level, which is benefit for the bonding between Mg and Mo₂C_0.875N_0.125. These results suggest that the adsorption and diffusion behaviors of Mg have been enhanced by nitrogen doping.

Monolayer Mo2C as anodes for magnesium-ion batteries

The adsorption and diffusion behaviors of magnesium (Mg) on monolayer Mo₂C have been investigated by the first principles method based on density functional theory (DFT). The structural stability and theoretical capacity of monolayer Mo₂C as anodes for magnesium-ion batteries (MIBs) have also been investigated. The results show that Mg prefer to occupy the H and T_C sites with the adsorption energies of - 1.439 and - 1.430, respectively, followed by B and T_Mo sites on Mo₂C monolayer. The Mg prefers to diffuse along the H-T_C-H path, furthermore, the other two possible paths (along H-B-H and H-T_Mo-H) also possess quite low energy barrier with the value of about 0.039 eV. The present results demonstrate that the adsorption energy per Mg atom and the volume expansion change mildly. The volume expansions change slightly from 0.7 to 7.08% with the variety of x, ranging from 0.167 to 2.0. The theoretical gravimetric capacity reaches to 469.791 mAhg^-1 with relatively small deformation and expansion as x = 2.0. The results mentioned above suggest that Mo₂C monolayer is one of the promising candidates for anode material of MIBs.

Strain-engineered BlueP-MoS2 van der Waals heterostructure with improved lithiation/sodiation for LIBs and SIBs

Innovative van der Waals (vdW) heterostructures formed from various monolayers exhibit exceptional physical properties relevant to their corresponding individual layers. In addition, the strain engineering of 2D materials is significantly exciting because they have the potential to sustain much larger strain in comparison to their bulk counterparts. In this work, the influence of strain on a BlueP-MoS2 van der Waals heterostructure was studied in order to explore its performance in LIBs/SIBs by first-principles DFT calculations. To ascertain the influence of strain on the performance of the BlueP-MoS2 van der Waals heterostructure for electrodes in LIBs/SIBs, we gathered vertically aligned monolayers of MoS2 and BlueP with different amounts of strain and studied the Li/Na storage properties of the said material. The application of strain could effectively enhance the adsorption capability of both Li/Na at the surfaces/interface of the BlueP-MoS2 heterostructure in comparison to that of the pristine BlueP-MoS2 heterostructure along with improved storage capacity. On the other hand, the application of strain is robust to the high mobility of both Li/Na inside and outside surfaces of BlueP-MoS2 heterostructure which ensures the fast charge/discharge process and improved rate performance. The calculated electronic structure revealed that the applied strain converted the BlueP-MoS2 heterostructure from a semiconductor to a metal, indicating enhanced conductivity compared to that for the pristine BlueP-MoS2 heterostructure. All the above-mentioned findings suggest the high potential application of the BlueP-MoS2 vdW heterostructures for flexible nanoelectronic devices.

Performance of Monolayer Blue Phosphorene Double-Gate MOSFETs from the First Principles

We systematically study the device characteristics of the monolayer (ML) blue phosphorene metal-oxide semiconductor field-effect transistors (MOSFETs) by using ab initio quantum-transport simulations. The ML blue phosphorene MOSFETs show superior performances with ultrashort-channel length. We first predict the ultrascaled ML blue phosphorene MOSFETs with proper doping concentration and underlap structures are compliant with the high-performance (HP) and low-power (LP) requirements of the International Technology Roadmap for Semiconductors in the next decade in the aspects of the on-state current, delay time, and power dissipation. Encouragingly, the performances of the ML blue phosphorene MOSFETs are superior to that of the MOSFETs based on arsenene, antimonene, InSe, etc. in terms of the on-state current at similar device size. We also consider the electron-phonon scattering in 10.2 nm gate ML blue phosphorene MOSFET. It is found that the on-state current with the scattering of the blue phosphorene device is degraded by 25.4 and 23.6% for HP and LP applications, which can also fulfill the HP and LP application target. Therefore, we can deduce that ML blue phosphorene is an alternative channel material to silicon for ultrascaled FETs if the large-scale and high-quality blue phosphorene can be achieved.

Gas adsorption on monolayer blue phosphorus: implications for environmental stability and gas sensors

Monolayer blue phosphorus has recently been synthesized by molecular beam epitaxial growth on Au(111) substrate. It is intriguing to compare this new 2D phase of phosphorus with phosphorene as to both fundamental properties and application prospects. Here, first-principles calculations are carried out to explore the adsorption behaviors of environmental gas molecules on monolayer blue phosphorus, including O₂, NO, SO₂, NH₃, H₂O, NO₂, CO₂, H₂S, CO, and N₂, and address their effects on the electronic properties of the material. Our calculations show that O₂ is prone to dissociate and tends to chemisorb on the blue phosphorus sheet, phenomena which has also been observed in phosphorene. The other gas molecules can stably physisorb on monolayer blue phosphorus, showing different interaction strengths with the monolayer. These molecules induce distinct modifications to the band gap, carrier effective mass, and work function, which also depends on the molecular coverage. The responses of the electronic properties are subject to the charge transfer as well as alignment of the frontier molecular orbital levels of the gaseous molecules and band edges of the parent sheet. These results suggest that monolayer blue phosphorus is a promising candidate for novel gas sensors.