Adsorption Distance Research Articles

Effect of strain on electrochemical performance of Janus MoSSe monolayer anode material for Li-ion batteries: First-principles study* *Project supported by the Education Department of Jiangxi Province, China (Grant No. GJJ160337).

First-principles calculations are performed to investigate the effect of strain on the electrochemical performance of Janus MoSSe monolayer. The calculation focuses on the specific capacity, intercalation potential, electronic structure, and migration behavior of Li-ion under various strains by using the climbing-image nudged elastic band method. The result shows that the specific capacity is nearly unchanged under strain. But interestingly, the tensile strain can cause the intercalation potential and Li-ion migration energy barrier increase in MoSSe monolayer, whereas the compressive strain can lead to the intercalation potential and energy barrier decreasing. Thus, the rate performance of the MoSSe anode is improved. By analyzing the potential energy surface of MoSSe surface and equilibrium adsorption distance of Li-ion, we explain the physical origin of the change in the intercalation potential and migration energy barrier. The increase of MoSSe potential energy surface and the decrease of adsorption distance caused by tensile strain are the main reason that hinders Li-ion migration.

Ultra-fast and accurate binding energy prediction of shuttle effect-suppressive sulfur hosts for lithium-sulfur batteries using machine learning

The shuttle effect of lithium polysulfides (LiPS) leads to fast capacity loss in lithium-sulfur batteries, which hinders the practical applications and makes the discovery of shuttle effect-suppressive sulfur host materials highly significant. Here, we proposed a machine learning (ML) method to rapidly and accurately predict the binding energies towards LiPS including Li2S4, Li2S6, and Li2S8 adsorbed on the surface of sulfur hosts with arbitrary configurations and active sites. As a case study, MoSe2 was selected as a sulfur host to predict the binding energy when absorbing the LiPS. The ML method shows six orders of magnitude faster than the conventional density functional theory (DFT), with a low predicted mean absolute error (MAE) of 0.1 eV. Based on the transfer learning (TL), we demonstrated that the presented ML method can be transferred to other layered compounds with a similar AB2 structure to MoSe2, and can efficiently predict their binding strengths with hosts. WSe2 was employed as a case to validate the TL method, with the results showing that MoSe2 had a stronger binding strength than WSe2 when adsorbing the LiPS, and only one-seventh of the ML training data was required. The impacts of different adsorption sites, configurations and distances on the binding energy were analyzed when LiPS is absorbed, which is of great significance to understand the adsorption mechanism of LiPS with hosts. The proposed work provides an efficient ML method to screen and discover new AB2 typed two-dimensional layered materials for suppressing the shuttle effect in lithium-sulfur battery.

New insight into absorption characteristics of CO2 on the surface of calcite, dolomite, and magnesite

An electrochemical method and multiscale simulations were used to study adsorption performances of CO2 on the surface of three minerals (calcite, dolomite, and magnesite). Experimental results show that dolomite has the optimum adsorption performance at different temperatures due to shorter adsorption time and larger adsorption capacity. The adsorption process of CO2 can be described by the pseudo-first-order kinetic model. The adsorption rate constant of magnesite is the largest and that of calcite is the smallest, but the adsorption rate constant of dolomite is closer to that of magnesite. Unexpectedly, multiscale simulations show that the adsorption interface of CO2 can be divided into strong and weak adsorption layers. Under saturated adsorption conditions, the adsorption capacity of CO2 is determined by the weak adsorption layer. Results highlight the importance of the effective adsorption distance for the first time. Furthermore, it confirms that the effective adsorption distance of calcite is the longest and that of magnesite is the shortest, but the effective adsorption distance of dolomite is closer to that of calcite. These findings could contribute to design advanced CO2 capture and sequestration techniques for achieving both improved shale gas production as well as alleviate the greenhouse effect.

First Principle Study of Adsorption Behavior of PF5 Gas Molecule on S and Mo Vacancy MoS2 Monolayer

The molybdenum disulfide monolayer (MoS2) is gaining more attention due to its attractive electronic property, and it is extensively used in different electronic applications. The presence of vacancies on the MoS2 monolayer leads to an increase in the conductivity of the material. In this work, we have investigated the adsorption behavior and estimated the gas-sensing properties of the S-vacancy (VS) and the Mo-vacancy (VMo) MoS2 monolayers and the two-probe MoS2 devices with phosphorus pentafluoride (PF5) gas molecule. To explore the sensing and electronic properties of VS and VMo MoS2 towards PF5 gas adsorption, the adsorption distance, adsorption energy, charge transfer, band structure, and density of the states have been analyzed using density functional theory in combination with Non-Equilibrium Green's Function. The results show that the PF5 gas molecule is allowed to adsorb on the S- and Mo-vacancy MoS2 monolayers through van der Waals interaction. The PF5 gas molecule shows adsorption distances of 3.3274 A and 2.8673 A, adsorption energies of − 0.1640 eV and − 0.3489 eV, and charge transfers of − 0.025 Q (e) and − 0.053 Q (e) on the VS/VMo MoS2 monolayers. To study the electron transport properties, the device density of the states, the transmission spectra, and the current–voltage characteristics of the VS/VMo MoS2 two-probe devices have been analyzed. The results predicted that the Mo-vacancy MoS2 device shows relatively more adsorption towards the PF5 gas molecule when compared with the VS MoS2 device.

Adsorption mechanism of decomposition gas of SF6 circuit breaker on MOF-505 analogue

The decomposition gas of SF6 circuit breaker adsorbed on MOF-505 analogue had been analyzed and studied in this paper by using the first principles of density functional theory (DFT) to analyze adsorption mechanism. The adsorption structures of organic ligands and metal sites were established and optimized. Through analyzing the adsorption energy, adsorption distance difference, charge transfer, density of states, Charge density difference and electron localization function, the results show that organic ligands and metal sites have excellent adsorption effect on H2S and SO2, belonging to chemical adsorbent, and the adsorption capacity is far greater than that of SF6. The MOF-505 analogue will be a potential adsorbent for the fault recovery of SF6 circuit breaker.

Study on the hydrogen storage performance of graphene(N)–Sc–graphene(N) structure

The electronic properties of a sandwich graphene(N)–Sc–graphene(N) structure and its average adsorption energies after the adsorption of 1, 3, 5, 7, 10, and 14H2 molecules were investigated by first principles. The average binding energies and adsorption distances of Sc atoms at different adsorption sites in N-doped bilayer graphene (N–BLG) were calculated. It was found that Sc atoms located at different adsorption sites of BLG generated metal clusters. The binding energy of the Sc atom located at the TT position of N–BLG (5.19 eV) was higher than the experimental cohesion energy (3.90 eV), and eliminated the impact of metal clusters on adsorption properties. It was found that the G(N)–Sc–G(N) system could stably adsorb 10 hydrogen molecules with an average adsorption energy of 0.24 eV. Therefore, it can be speculated that G(N)–Sc–G(N) is an excellent hydrogen storage material.

Dihydrogen molecule adsorption with the platinum alloys based on transition metal PtX {1 1 1} (X = Mo, W) surface for catalysis purpose: Density functional theory

We reported the density functional theory investigations of the potentiality of platinum alloys with a transition metal PtX {111} (X = Mo, W) to catalyze the dissociative adsorption reaction of the dihydrogen molecule. We have analyzed the electron density, the density of state (DOS), the Mulliken population, the adsorption energy as well as the adsorption distance. Our aim was to describe the kinetic of the catalysis reactions and see if there is dissociation of the dihyrogen molecule. Also determine the adsorption site position on the upper surface. The most suitable site for dissociation and adsorption of the dihydrogen is the top site. The platinum alloy achieves a significant adsorption and dissociation distance compared to the pure surface. In addition, the most important adsorption energy is attributed to the tungsten alloy, followed by molybdenum alloy and then pure platinum. The initial emitted hypothesis is that the best configuration that favors the dissociation of dihydrogen is the top site in the case of the molybdenum alloy.

The distances measurement problem for an underwater robotic swarm: a semi-experimental trial, using power LEDs, in unknown sea water conditions

In a preceding paper, we have showed as swarm robotics displacement can be related to the deformation of a continuum material, discretized by a lattice network representing the swarm. To reach this aim, it is fundamental to know the swarm configuration, i.e., its shape; this can be computed from the knowledge of the relative distances between its elements and it is studied as a geometry distances problem. Typically, ultrasonic devices are employed to measure the distances. We propose a method based on light signal exchanged between the machines and the computing of the unknown water adsorption coefficient and distance. Aim of this paper is, therefore, to measure distances between underwater elements of the swarm using cheap power LEDs as light source and photodiode as receiver. The receiving photodiode produces a current we can correlate with distance and water adsorption coefficient; we can be able to estimate the two unknown parameters by moving the robots and stressing the emission conditions of the LED diode. Actual work is based on a previous paper where we stressed work conditions of a power LED in shallow water to change its emission characteristics; now, using these results, we can now perform a set of measurements leading to the knowledge of distances d and adsorption coefficient a(lambda ). The method we propose here can be a possible support to traditional ultrasonic devices

Impact of fluorination on interface energetics and growth of pentacene on Ag(111).

We studied the structural and electronic properties of 2,3,9,10-tetrafluoropentacene (F4PEN) on Ag(111) via X-ray standing waves (XSW), low-energy electron diffraction (LEED) as well as ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS). XSW revealed that the adsorption distances of F4PEN in (sub)monolayers on Ag(111) were 3.00 Å for carbon atoms and 3.05 Å for fluorine atoms. The F4PEN monolayer was essentially lying on Ag(111), and multilayers adopted π-stacking. Our study shed light not only on the F4PEN–Ag(111) interface but also on the fundamental adsorption behavior of fluorinated pentacene derivatives on metals in the context of interface energetics and growth mode.

A novel high-performance methane sensor based on Ti-Decorated 2D γ-graphyne: A dispersion-corrected DFT insight

In the present theoretical study, the effect of methane adsorption on the electronic properties of titanium (Ti)-decorated γ-graphyne (γ-GY) is investigated. To this end, the dispersion-corrected density functional theory (DFT-D2) is employed to explicitly include the van der Waals interactions (vdW) in the computations. The results show that the methane is physisorbed on the γ‒GY owing to the low binding energy and relatively long adsorption distance. According to our calculations, Ti atom is chemically bound to four sp carbon atoms with the binding energy of −4.960 eV (per supercell) and provide an appropriate adsorption site for reducing gas molecule such as methane. We also observe that the methane molecule chemisorbed on the Ti-decorated γ-GY with the binding energy of −0.594 eV per supercell. Moreover, upon methane adsorption, the electronic bandgap of Ti-decorated γ-GY reduces about 0.051 eV. Our results reveal that Ti-decorated γ-GY has excellent sensing efficiency for CH4 gas with high selectivity and fast recovery time. Therefore, the present work encourages the growing use of Ti-decorated γ-GY for the development of thermopower-based, resistive-based, or quartz crystal microbalances-based methane sensors.

Determination of Pairwise Interaction of Atoms from the Interaction of an Adatom with Graphene

A problem of identification of parameters of the Mie–Lennard-Jones and Morse pairwise interatomic potentials from the interaction of a single metal atom with perfect one-layer graphene has been considered for the first time. Numerical calculations have been performed for different heteroatomic pairs. The potential parameters were calculated from the equilibrium adsorption energy and distances in the adatom–graphene system and the data of numerical calculations performed by the density functional theory method. The Levenberg–Marquardt algorithm was used for optimization. The calculations are consistent with available literature data on melting points of metal carbides and ionic and covalent radii. The results obtained are of significant practical interest since they open up a new opportunity for evaluating the parameters of pairwise potentials. The advantage of the method is that the empirical combining rules are not used to calculate the parameters of potentials.

Pt-doped armchair graphene nanoribbon as a promising gas sensor for CO and CO2: DFT study

Abstract In this work, four armchair graphene nanoribbon (AGNR) based sensor materials were built using Atomistic ToolKit Virtual NanoLab (ATK-VNL) and utilized to detect carbon monoxide (CO) and carbon dioxide (CO2) gases. First, the effect of passivating AGNR on the sensing performance toward CO and CO2 gases has been investigated, where AGNR was passivated with hydrogen (H-AGNR) and nitrogen (N-AGNR). The obtained results reflected no significant changes in the adsorption parameters of CO and CO2 molecules on H-AGNR and N-AGNR. Particularly, the adsorption energies between H-AGNR and N-AGNR systems and CO were found to be −0.446 and −0.436 eV, while for the case of CO2, the adsorption energies were found to be −0.426 and −0.432 eV, respectively. To enhance the sensing performance, both H-AGNR and N-AGNR systems were doped with platinum (Pt) forming another two systems: Pt–H-AGNR, and Pt–N-AGNR. After doping, the results revealed a significant increase in the adsorption energy to almost 9 times than the non-doped systems for the cases of CO on Pt–N-AGNR as well as CO2 on both Pt–H-AGNR and Pt–N-AGNR. Moreover, an increase of almost 13 times was observed in the adsorption energy for the case of CO on Pt–H-AGNR. Besides to the adsorption energy ( E a d s ), the adsorption distance (( D ), charge transfer ( Δ Q ), the density of states (DOS), as well as the band structure have been examined to confirm the adsorption of CO and CO2 on the four systems.

The adsorption of divalent heavy metal ions on (8,0) carbon nanotubes: The first-principles study

In order to explore new ways to detect and remove heavy metal ions from industrial wastewater, the first-principles method based on density functional theory has been used to investigate the performance of carbon nanotubes (CNTs) in adsorbing divalent heavy metal ions which include Zn[Formula: see text], Cu[Formula: see text], Pb[Formula: see text] and Sn[Formula: see text]. Results show that the adsorption of Zn[Formula: see text] on CNTs is weak and only physical adsorption forms between them. However, for Cu[Formula: see text], Pb[Formula: see text] and Sn[Formula: see text], the final adsorption distance with CNTs is greatly decreased, and the adsorption energy and charge transfer amount with CNTs are significantly increased. In addition, the charge density of Cu[Formula: see text], Pb[Formula: see text] and Sn[Formula: see text] overlaps effectively with that of CNTs. These indicate the formation of strong chemisorption between these ions and CNTs. Therefore, CNTs could be used as a sensing material to detect and remove Cu[Formula: see text], Pb[Formula: see text] and Sn[Formula: see text] from wastewater. The research provides theoretical guidance for the application of CNTs in heavy metal ions treatment.

First principle investigation of H2Se, H2Te and PH3 sensing based on graphene oxide

Detecting toxic gases is of great importance to protect our health and preserve the quality of life. In this work, graphene (G) and graphene oxide with three different modifications (G–O, G–OH, and G–O–OH) have been used to detect hydrogen selenide (H2Se), hydrogen telluride (H2Te), and phosphine (PH3) molecules based on Atomistic ToolKit Virtual NanoLab (ATK-VNL) package. The adsorption energy (Eads), adsorption distance (D), charge transfer (ΔQ), density of states (DOS), and band structure have been investigated to confirm the adsorption of H2Se, H2Te, and PH3 on the surface of G, G–O, G–OH, and G–O–OH systems. The results of G revealed highest Eads for the case of H2Te with −0.143 eV. After the functionalization of G surface, the adsorption parameters reflected an improvement due to the presence of the functional groups. Particularly, the highest adsorption energy was found between G–O system and H2Se gas with Eads of −0.319 eV. The smallest adsorption distance was found between G–OH system and H2Se gas. The highest charge transfer was found for the case of H2Se gas adsorbed on G–O–OH system. By thorough comparison of the adsorption energy, adsorption distance, and charge transfer between G, G–O, G–OH, and G–O–OH systems and the three gases, G–O–OH system can be considered as a potential sensor for H2Se gas.

Quantum Chemical Study on the Influence of Dodecyl Trimethyl Ammonium Bromide on the CH4 Adsorption of Coal

The adsorption of dodecyl trimethyl ammonium bromide (DTAB) on coal can affect the wettability of coal and change the water absorption of coal. After DTAB treatment, the change in the CH4 adsorption capacity of coal is worth further study. To reveal the microscopic mechanism of the influence of DTAB on the CH4 adsorption capacity of coal, we employed the density functional theory (DFT) with the 6-311 G (d, p) basis set. DFT-based computations interpreted the adsorption process of CH4 and DTAB on coal molecules and determined the stable structure, adsorption distance, Mulliken overlapping populations, and adsorption energies of the two adsorption configurations. The results showed that the adsorption energies of CH4 and DTAB on the molecular model of coal were 2.15 and 42.69 kJ/mol and the adsorption stability distances were 0.261 and 0.238 nm, respectively. The DTAB–coal configuration was more stable than the CH4–coal configuration. When there was competitive adsorption between DTAB and CH4 on coal, the coal molecules preferentially adsorb the DTAB. Infrared spectroscopy and adsorption experiments were also carried out, and the calculation results of quantum chemistry are consistent with the experimental results.

Highly sensitive gas sensing material for polar gas molecule based on Janus group-III chalcogenide monolayers: A first-principles investigation

Gas sensors play an indispensable role in industrial, personal safety and environmental protection, and have been widely investigated by researchers. In some cases, the sensitivity of a two-dimensional material sensor can be enhanced by generating vacancies or applying an external electric field. Similar results can be achieved using Janus 2D materials, which have an inherent electric field and are good candidates for high-sensitivity gas sensors. In this study, the electronic and transport properties of Janus group-III chalcogenide monolayers (Ga2SSe, In2SSe) were investigated for detecting CO2 and NO2 using first-principles calculations. For several parameters that affect the performance of gas sensors, such as adsorption distances, adsorption energies, charge transfers and density of states (DOS), a detailed comparison of Janus group-III chalcogenide monolayers has been provided with their pristine systems, Janus group-III chalcogenide monolayers (Ga2SSe, In2SSe) have high selectivity. It was mainly ascribed to the built-in electric field caused by the out-of-plane asymmetric structure of Janus monolayer which enhances the dipole-dipole interaction between the polar gas molecule and the 2D materials. And the variation of transmission spectra of the Janus group-III chalcogenide monolayer before and after adsorbing molecules further proves the feasibility of this kind of material as a high-sensitivity gas sensor.

Effects of monohydric alcohols of varying chain lengths and isomeric structures on magnesite and dolomite flotation by dodecylamine

Monohydric alcohols with varying chain lengths and isomeric structures, which had significant effects on improving the magnesite and dolomite flotation, were added separately to replace part of dodecylamine (DDA). The intensified effects of alcohols differ with different chain lengths and isomeric structures. Alcohols can enhance the adsorption of DDA and reduce the adsorption distance of DDA on both surfaces of magnesite and dolomite. And the adsorption energy of the mixed collector decreased with the increasing chain length of alcohol. The isomeric alcohols presented more significant effects on lowering the adsorption energy of the collectors. The co-adsorption of alcohol compressed the hydration layer and dilute the water concentration in the hydration layer. Changes of the hydration layer were greater with adding alcohol with a long carbon chain and isomeric structure. Thus, alcohols with long chain lengths and isomeric structures performed better in improving the flotation of magnesite and dolomite.

DFT investigation of H2S adsorption on graphenenanosheets and nanoribbons: Comparative study

Graphenenanosheet (GNS), armchair graphenenanoribbon (AGNR), and zigzag graphenenanoribbon (ZGNR) systems were investigated by first principle calculations using the density functional theory (DFT). The DFT calculations explored the potential of utilization of these materials as gas sensors to detect hydrogen sulfide (H 2 S) gas. H 2 S gas adsorption was explored using: the adsorption energy (E ads ), adsorption distance (D), charge transfer (ΔQ), density of states (DOS), and band structure of the generated systems before and after adsorption of H 2 S. The results showed that E ads of bare ZGNR was the highest of −0.171 eV as compared with GNS and AGNR. The surfaces of GNS, AGNR, and ZGNR have been modified with epoxy and then with a hydroxyl groups. The adsorption capacity of the three systems has been enhanced after the modifications with both the epoxy and hydroxyl groups. Based on the adsorption energy and charge transfer results, hydroxyl modified ZGNR system can be used effectively for detection applications of H 2 S since it exhibits the highest charge transfer and large adsorption energy. • Graphene nanosheet, armchair nanoribbon, and zigzag nanoribbon were investigated by DFT. • The materials were then used as gas sensors to detect H 2 S gas. • Adsorption energy, adsorption distance, charge transfer, density of states, and band structure were investigated. • The surfaces of graphene systems were modified with epoxy and hydroxyl groups. • The adsorption capacity of the three systems has been enhanced after the modifications.

Enhancing the Sensing Performance of Zigzag Graphene Nanoribbon to Detect NO, NO2, and NH3 Gases

In this article, a zigzag graphene nanoribbon (ZGNR)-based sensor was built utilizing the Atomistic ToolKit Virtual NanoLab (ATK-VNL), and used to detect nitric oxide (NO), nitrogen dioxide (NO2), and ammonia (NH3). The successful adsorption of these gases on the surface of the ZGNR was investigated using adsorption energy (Eads), adsorption distance (D), charge transfer (∆Q), density of states (DOS), and band structure. Among the three gases, the ZGNR showed the highest adsorption energy for NO with −0.273 eV, the smallest adsorption distance with 2.88 Å, and the highest charge transfer with −0.104 e. Moreover, the DOS results reflected a significant increase of the density at the Fermi level due to the improvement of ZGNR conductivity as a result of gas adsorption. The surface of ZGNR was then modified with an epoxy group (-O-) once, then with a hydroxyl group (-OH), and finally with both (-O-) and (-OH) groups in order to improve the adsorption capacity of ZGNR. The adsorption parameters of ZGNR were improved significantly after the modification. The highest adsorption energy was found for the case of ZGNR-O-OH-NO2 with −0.953 eV, while the highest charge transfer was found for the case of ZGNR-OH-NO with −0.146 e. Consequently, ZGNR-OH and ZGNR-O-OH can be considered as promising gas sensors for NO and NO2, respectively.

Promoting sensitivity and selectivity of NO2 gas sensor based on metal (Pt, Re, Ta)-doped monolayer WSe2: A DFT study

In this paper, the interactions of small gas molecules (H2O, CO2, SO2 and NO2) with pure WSe2, Pt-WSe2, Re-WSe2 and Ta-WSe2 monolayer were investigated through using the DFT calculations to explore their potential applications as gas sensing. The adsorption energies, charge transfers and electronic properties of the gas adsorption systems had been calculated to model the gas adsorption behaviors on monolayer WSe2 (pristine and Pt, Re, Ta atom doping), and the band gaps of Pt, Re, Ta doped monolayer WSe2 were all decreased, while monolayer Re-WSe2 was found to be metallic. The results predicted that the adsorption effect of NO2 gas molecule was the best, and the adsorption energy of monolayer Ta-WSe2 was found to be the largest of the molecules studied. Calculations also shown that there were shorter adsorption distance and more charge transfer for Pt-, Re- and Ta-doped systems than that of pure monolayer WSe2. The results confirmed that monolayer Ta-WSe2 could be used as effective and potential adsorbents for toxic NO2 gas molecule.