The quest for a suitable
material with the potential of capturing
toxic nitrogen-containing gases (NH3, NO, and NO2) has motivated us to explore the structural, electronic, and gas-sensing
properties of transition metal dichalcogenides (TMDs); MoSe2 and MoTe2. Spin-polarized density functional theory (DFT)
calculations demonstrate weak binding of nitrogen-containing gases
(NCGs) with the pristine TMDs, which limits the use of the latter
as efficient sensing materials. However, suitable elemental substitutions
improve the binding mechanism enormously. Our dispersion-corrected
DFT calculations revealed that Se (Te) substitution with Ge (Sb) in
MoSe2 (MoTe2) not only enhances the binding
energies but also causes a significant variation in the electronic
properties and work functions. A charge-transfer mechanism based on
Bader analysis indicates that transfer of charges from MoSe2–Ge (MoTe2–Sb) to the NCGs is responsible
for the improvement in the binding characteristics. Based on our findings,
it is evident that 2.08% of elemental substitutional makes both MoSe2 and MoTe2 promising materials for NH3, NO, and NO2 gas sensing.
The framework of density functional theory has been applied to predict the formal potential of 137 molecules and identify promising candidates for the application as the organic electrode of rechargeable batteries.
The unique structural characteristics make the 2D materials potential candidates for designing negative electrodes for rechargeable energy storage devices. Here, by employing density functional theory (DFT) calculations, we study the precise viability of using Si 2 BN, a graphene-like 2D material, as a high-capacity anode material for Mg-ion battery (MIB) application. The favorable Mg-adsorption sites with maximum possible coverage effect are explored in detail. It is found that the Si 2 BN sheet can be adsorbed to a configuration of Mg 8 Si 16 B 8 N 8 , which proposes a theoretical capacity of 647.896 mA h g −1 for divalent Mg 2+ -ion battery applications. The average open-circuit voltage of 0.6−0.7 V and intercalation migration energy barrier in the range of 0.08−0.35 eV make Si 2 BN one of the most promising anode materials for MIB applications. The porous Si 2 BN with high structural stability and metallic electronic structures along with the low Mg 2+ -ion migration barrier energies predict high electron and Mg-ion conductivity, ensuring fast charge/discharge cyclic performance. The above-mentioned findings validate that the Si 2 BN sheet can work as an excellent high-performance anode material for MIBs.
This work aims to efficiently capture CO2 on two-dimensional (2D) nanostructures for effective cleaning of our atmosphere and purification of exhausts coming from fuel engines. Here, we have performed extensive first principles calculations based on density functional theory (DFT) to investigate the interaction of CO2 on a recently synthesized ZnO monolayer (ZnO-ML) in its pure, defected and functionalized form. A series of rigorous calculations yielded the most preferential binding configurations of the CO2 gas molecule on a ZnO-ML. It is observed that the substitution of one oxygen atom with boron, carbon and nitrogen on the ZnO monolayer resulted into enhanced CO2 adsorption. Our calculations show an enriched adsorption of CO2 on the ZnO-ML when substituting with foreign atoms like B, C and N. The improved adsorption energy of CO2 on ZnO suggests the ZnO-ML could be a promising candidate for future CO2 capture.
We have used density functional theory to investigate the adsorption efficiency of a hydrogenated graphene (graphane) sheet for H2S and NH3 gases. We find that neither the pristine graphane sheet nor the sheet defected by removing a few surface H atoms have sufficient affinity for either H2S or NH3 gas molecules. However, a graphane sheet doped with Li adatoms shows a strong sensing affinity for both the mentioned gas molecules. We have calculated the absorption energies with one [referred to as half coverage] molecule and two molecules [referred to as full coverage] for both gases with the Li-doped graphane sheet. We find that for both the gases, the calculated absorption energies are adequate enough to decide that the Li-doped graphane sheet is suitable for sensing H2S and NH3 gases. The Li-doped sheet shows a higher affinity for the NH3 gas compared to the H2S gas molecules due to a stronger Li(s)-N(p) hybridization compared to that of Li(s)-S(p). However, while going from the half coverage effect to the full coverage effect, the calculated binding energies show a decreasing trend for both the gases. The calculated work function of the Li-doped graphane sheet decreases while bringing the gas molecules within its vicinity, which explains the affinity of the sheet towards both the gas molecules.
The sensitive nature of molecular hydrogen (H) interaction with the surfaces of pristine and functionalized nanostructures, especially two-dimensional materials, has been a subject of debate for a while now. An accurate approximation of the H adsorption mechanism has vital significance for fields such as H storage applications. Owing to the importance of this issue, we have performed a comprehensive density functional theory (DFT) study by means of several different approximations to investigate the structural, electronic, charge transfer and energy storage properties of pristine and functionalized graphdiyne (GDY) nanosheets. The dopants considered here include the light metals Li, Na, K, Ca, Sc and Ti, which have a uniform distribution over GDY even at high doping concentration due to their strong binding and charge transfer mechanism. Upon 11% of metal functionalization, GDY changes into a metallic state from being a small band-gap semiconductor. Such situations turn the dopants to a partial positive state, which is favorable for adsorption of H molecules. The adsorption mechanism of H on GDY has been studied and compared by different methods like generalized gradient approximation, van der Waals density functional and DFT-D3 functionals. It has been established that each functionalized system anchors multiple H molecules with adsorption energies that fall into a suitable range regardless of the functional used for approximations. A significantly high H storage capacity would guarantee that light metal-doped GDY nanosheets could serve as efficient and reversible H storage materials.
An
in-depth understanding of the practical sensing mechanism of
two-dimensional (2D) materials is critically important for the design
of efficient nanosensors toward environmentally toxic gases. Here,
we have performed van der Waals-corrected density functional theory
(DFT) simulations along with nonequilibrium Green’s function
(NEGF) to investigate the structural, electronic, transport, thermodynamic,
and gas-sensing properties of pristine and defect-crafted bismuthene
(bBi) sheets toward sulfur- (H2S, SO2) and nitrogen-rich
(NH3, NO2) toxic gases. It is revealed that
the electrical conductivities of pristine and defective bBi sheets
are altered upon the adsorption of incident gases, which have been
verified through transport calculation coupled with the work function
and electronic density of states. Our calculations disclose that bBi
sheets show superior and selective gas-sensing performance toward
NO2 molecules among the studied gases due to a significant
charge redistribution and more potent adsorption energies. We find
that the mono- and divacancy-induced bBi sheets have enhanced sensitivity
because the adsorption behavior is driven by a considerable change
in the electrostatic potential difference between the sheets and the
gas molecules. We further performed statistical thermodynamic analysis
to quantify the gas adsorption abilities at the practical temperature
and pressures for the studied gas samples. This work divulges the
higher sensitivity and selectivity of bBi sheets toward hazard toxins
such as NO2 under practical sensing conditions of temperature
and pressure.
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