Absolute Value Of Adsorption Energy Research Articles

Sensing behavior of modified two-dimensional GeTe monolayer to detect air discharge components: A first-principles study

It is crucial to determine the operating condition of air-insulated equipment by monitoring air discharge components (O3, NO2, CO) to detect any occurrence of partial discharges (PD). Although GeTe is widely applied in gas sensing technology, its performance in selective detection is relatively subpar. This study investigatesthe modification of structures of GeTe monolayers by doping single transition-metal (TM) atom (Fe, Co, Ir, Pt, Pd, and Rh) to enhance its gas adsorption capability and selectivity of different doped GeTe monolayers to gases according to competitive adsorption. Multiple properties such as adsorption energy, charge transfer, charge difference density (CDD), density of states (DOS), occupation function, desorption time, and work function were discussed, indicating that doped GeTe exhibits greater adsorption capabilities. Specifically, Ir-GeTe demonstrates the highest absolute value of adsorption energy for O3 at 2.75 eV, while Co-GeTe exhibits the highest absolute value of adsorption energy for NO2 at 2.13 eV. Furthermore, the analysis of atomic orbital overlap reveals stronger chemical interactions between Ir-GeTe and O3, as well as Co-GeTe and NO2. Considering selectivity and working function, Fe-GeTe emerges as a potential sensing material for detecting NO2. This research offers promising and practical applications for single TM atom-doped GeTe as gas-sensitive materials.

Theoretical evaluation of gas sensing and capturing characteristics on the point defective diboron dinitride monolayer

Defects can significantly alter the properties of 2D material surfaces, thereby affecting the application results. In this work, the adsorption behaviors of H2S, SO2, NH3, and NO2 gas molecules on rationally defective diboron dinitride (n-BN) monolayers in the presence and absence of an external electric field and moisture condition are studied by the first-principles calculation approach. The results demonstrate that the boron and nitrogen defects are more likely to be generated and both defective monolayers have strong absorption effects on SO2 and NO2 gas molecules with absolute values of adsorption energy above 2.5 eV. And the conductivity change after adsorption of NO2 molecule is particularly pronounced in nitrogen defect monolayer, thus greatly increasing the sensitivity to the gas molecule. Based on the high sensitivity, the defective monolayer could be an ideal one-time scavenger for SO2 and NO2 gas molecules. While the H2S and NH3 molecules could obtain the appropriate adsorption energy and the adjustable recovery time on the defective monolayer under the dry or existent external electric field environment. These results make it possible to design a useable gas device with good gas sensing and capturing characteristics on the defective n-BN monolayer.

Structural, electronic, and thermoelectric properties of hydroxyl groups adsorption on SnO2 (110) surface: A first‐principles study

Structural, electronic, and thermoelectric properties of bridging OHb and terminal OHt groups adsorbed on stoichiometric SnO2 (110) surfaces have been investigated using density functional theory and semiclassical Boltzmann transport theory with effective core pseudopotential implemented in CRYSTAL17 program. Our results indicate that H and OH yield significant structural relaxation around the adsorption sites O2c and Sn5c. The results have shown that the absolute value of adsorption energy increases with decreasing the coverage from 1 to 1/4 monolayer. Mulliken charge analysis, band structures, and density of states were calculated and discussed. We found that H and OH adsorption increases the band gap energy from 2.81 eV for clean surfaces to 3.04, 2.95, and 2.89 eV with, respectively, 1, 1/2 and 1/4 monolayer surface coverages. Thermoelectric properties revealed that the presence of hydroxyl groups on the SnO2 (110) surfaces may enhance the Seebeck coefficient, electrical conductivity, and electronic thermal conductivity.

Effects of Flotation Reagents on the Morphology of Magnesium Hydroxide: Experimental and Simulation Study

The flotation process to extract potassium salt from carnallite ores could produce the MgCl2 mother liquor with flotation reagents─octadecyl amine hydrochloride (ODA) and dodecyl morpholine (DMP). The organic impurities would further affect MgCl2 resource-integrated utilization for preparing magnesium hydroxide (MH). In this study, the effects of flotation reagents with different concentrations on the morphology of MH were investigated at a hydrothermal temperature of 200 °C for 6 h with the hydrothermal medium of a 4 mol/L NaOH solution. It was observed that the average thickness of MH crystal plates increased and the morphology of crystals changed from regular hexagonal plates to irregular polygonal plates with the increase of ODA and DMP concentrations. Molecular dynamics (MD) simulation was applied to further explain the effect mechanism. The results indicated that ODA and DMP molecules were more likely to be adsorbed on the (1 1 0) plane in contrast to the (0 0 1) plane due to the larger absolute values of adsorption energy on the (1 1 0) plane. The long carbon chains far away from the (1 1 0) plane would form steric hindrance to affect the growth rate of MH crystals in the [1 1 0] direction.

Investigation on removal of multi-component volatile organic compounds in a two-stage plasma catalytic oxidation system - Comparison of X (X=Cu, Fe, Ce and La) doped Mn2O3 catalysts

Mn2O3-X catalysts (X = Cu, Fe, Ce and La) were prepared based on γ-Al2O3 for the mixture degradation of muti-component volatile organic compounds (VOCs) composed of toluene, acetone, and ethyl acetate. The catalysts were characterized, and the density functional theory (DFT) simulation of ozone adsorption on Mn2O3-X were carried out to investigate the influence of adsorption energy on catalytic performance. The results showed that the removal efficiency (RE) of each VOC component was similarly improved by Mn2O3-X catalysts, and the greatest increase in VOCs' removal efficiency was obtained (7.8% for toluene, 86.2% for acetone, and 82.5% for ethyl acetate) at a special input energy (SIE) of 700 J L−1 with Mn2O3–La catalyst. Characterization results demonstrated that Mn2O3–La catalyst had the highest content of low valence Mn elements and the greatest Oads/Olatt ratio, as well as the lowest reduction temperature. Mn2O3–La catalyst also presented superior catalytic effect in improving carbon balance (CB) and CO2 selectivity (SCO2). The CB and SCO2 were increased by 47.7% and 12.61% respectively with Mn2O3–La at a SIE of 400 J L−1 compared with that when only γ-Al2O3 was applied. The DFT simulation results of ozone adsorption on Mn2O3-X catalysts indicated that the adsorption energy of catalyst crystal was related to the catalytic performance of the catalyst. The Mn2O3–La/γ-Al2O3 catalyst, which had the highest absolute value of adsorption energy, presented the best performance in improving VOCs’ RE.

Molecular simulation of thermodynamic properties of CH4 and CO2 adsorption under different moisture content and pore size conditions

In order to further clarify the thermodynamic properties of CH4 and CO2 adsorption in coal, a Monte Carlo method with a giant regular system was used to simulate the adsorption behavior of CH4 and CO2 in coal at different moisture contents and pore sizes. The results show that the adsorption of CH4 and CO2 in coal molecules is negatively correlated with the moisture content. As the pore size increases, the wall superimposed effect decreases, the stability of adsorption becomes less stable, and the selectivity of CO2 adsorption decreases, but the space to accommodate gas molecules becomes larger, which makes the adsorption amount rise. The average heat of adsorption of CH4 and CO2 showed a decreasing and then increasing relationship with the moisture content, and a negative correlation with the pore size, and the effect of H2O on CO2 is stronger than that of CH4. With the increase of moisture content, the absolute value of adsorption energy increases overall, and the high potential of water clusters tends to attract CO2 molecules more. With the increase of pore size, the wall superimposed effect weakens and the adsorption stability becomes worse, which makes the absolute value of adsorption energy smaller. The overall adsorption entropy of CH4 and CO2 has a negative correlation with moisture content and a positive correlation with pore size. The comparison of the slope of the fitted curves of adsorption entropy at different moisture contents adds that CO2 mainly displaces CH4 molecules in the middle of the pores at 3% moisture content.

Inhibition Effect and Mechanism Explanation of Perilla Seed Extract as a Green Corrosion Inhibitor on Q235 Carbon Steel.

The development of environmentally friendly corrosion inhibitors has become a research hotspot. Aiming at the potential corrosion inhibition effect of perilla seed extract on Q235 carbon steel, the corrosion inhibition effect was quantitatively evaluated by various research methods, and the effective corrosion inhibition composition and mechanism were discussed. The research methods include potentiodynamic polarization curve method, HPLC-MS, FT-IR, XPS and chemical calculation. The experimental results show that the inhibitor prepared from perilla seed extract is a mixed inhibitor, and its adsorption behavior accords with Langmuir adsorption theory and its adsorption free energy is −22.70 kJ/mol. Combined with the experimental results and theoretical calculation, the effective corrosion inhibiting components are luteolin and apigenin. Theoretical calculation shows that both of them are adsorbed parallel to the surface of carbon steel to form thin films. The adsorption mechanism is that carbonyl O atoms in luteolin and apigenin hybridize with the 3 d empty orbit of Fe. From the point of view of quantum chemistry, the smaller the HOMO value and the energy gap value, the better the adsorption of corrosion inhibitor on the surface of carbon steel. From the point of view of molecular dynamics simulation, the greater the absolute value of adsorption energy, the better the adsorption of corrosion inhibitor on carbon steel surface.

Catalytic conversion and DFT analysis of post DDBD-catalysis system for degradation of toluene, ethyl acetate and acetone with different metal-oxides catalysts

A series of multiphase metal-oxide catalysts (MnOx/γ-Al2O3, CuOx/γ-Al2O3, FeOx/γ-Al2O3, CeOx/γ-Al2O3 and LaOx/γ-Al2O3) were prepared for plasma-catalyst degradation of multicomponent volatile organic compounds (VOCs, such as toluene, acetone and ethyl acetate). The results reveal that the degradation efficiency (DE) of acetone, toluene and ethyl acetate in the DDBD system can be arranged as follows: Mn2O3/γ-Al2O3> Fe2O3/γ-Al2O3> CuO/γ-Al2O3> CeO2/γ-Al2O3> La2O3/γ-Al2O3> γ-Al2O3, and the highest DE (49.5% for acetone, 93.3% for toluene and 79.8% for ethyl acetate) is obtained in Mn2O3/γ-Al2O3+double dielectric barrier discharge (DDBD) system at specific input energy (SIE) of 700 J/L. Compared with the other catalysts, Mn2O3/γ-Al2O3 also exhibits the most significant inhibitory effect on the production of ozone (O3). On the other hand, CeO2/γ-Al2O3 and La2O3/γ-Al2O3 catalysts display different catalytic selectivity. Both catalysts can slightly raise the DE of VOCs and remarkably facilitate VOCs' mineralization. The carbon balance (CB) is increased by 30.2% and 38.8%, and the CO2 selectivity (SCO2) is raised by 70.5% and 11.9% in the CeO2/γ-Al2O3+DDBD system and La2O3/γ-Al2O3+DDBD system at SIE of 700 J/L, respectively. To further understand the catalytic effect of the catalysts, the adsorption of O3 on different catalysts was simulated by a DFT model. According to the results of the DFT model, it is found that the adsorption energy of other metal oxides seems to be used as a reference for catalytic effect to a certain extent except CeO2. The higher the absolute values of adsorption energy, the higher the improvement of VOCs degradation efficiency by catalyst.

Study on Sensitivity and Drug Loading Characteristics of Graphene‐like BN Nanosheets to Indomethacin Based on DFT

AbstractThe sensitivity and the drug loading characteristics of the doped BN nanosheet (BNNS) to indomethacin (INDO), a analgesic, anti‐inflammatory and antipyretic drug, were studied by using density functional theory. The adsorption energy calculated results show that the pristine BNNS can't be used to detect INDO, so that it can't be used as a potential efficient sensing materials to INDO. C, Si, Al, Ga doping enhances the absolute value of adsorption energy, and the recovery time is acceptable in practical application. All the elements studied (C, Si, Al, Ga, P, Cl) narrow the effective band gap, resulting in an increase of the electrical conductivity of INDO/BNNS complexes. These findings indicate the suitable doping improves the sensitivity of BNNS as sensing material to INDO, Si is the most efficient element. The INDO load on BNNS can be increased by the C, Si, Al, Ga doping. The sustained or controlled release of the INDO may be achieved by adjusting the doping of BNNS. Analysis of global reactivity descriptors show that the C, Si doping leads to the most reactive complexes. The solubility of INDO/doped BNNS complex can be modulated by the doping, and therefore BNNS can be as the carriers for poorly water‐soluble drugs. Comprehensive consideration of the adsorption energy, global reactivity descriptors and solubility, it is concluded that Si doped BNNS is most suitable as an INDO carrier.These results encourage a further investigation of BN nanosheet as a drug nanocarrier.

Molecular dynamics study of three amino acids as corrosion inhibitor for copper in hydrochloric acid solution.

Molecular dynamics (MD) simulation is used to study the corrosion inhibition mechanism of cysteine (Cys), glutamic (Glu) and glycine (Gly) for copper in hydrochloric acid solution. The adsorption energy and radial distribution function results show that all three amino acids can spontaneously adsorb on Cu (111) surface by chemical adsorption. The absolute value of adsorption energy and intensity is Cys > Glu > Gly. The diffusion coefficient and relative concentration curve show that all the three amino acids can inhibit the diffusion and aggregation ability of corrosion particles, so the three amino acids not only can slow down the aggregation of corrosive particles, but also effectively repel corrosive particles to protect the substrate. The inhibition ability obtained by the MD simulation shows the trend of Cys > Glu > Gly, which is consistent with the experimental results. The inhibition efficiency is determined by both the adsorption strength on the substrate surface and inhibition ability for the diffusion and aggregation ability of corrosion particles.

A combined quantum chemical, molcular dynamics and Monto Carlo study of three amino acids as corroison inhibitors for aluminum in NaCl solution

The performance of arginine (Arg), glutamine (Glu), and asparagine (Asp) in inhibiting the corrosion of aluminum in NaCl solution and the inhibition mechanism at atomic level are investigated via the combination of the quantum chemistry (QM) calculations, molecular dynamics (MD) and Monte Carlo (MC) simulations to reveal the relationship among chemical structure, composition and performance. QM results show that differences in EHOMO, ELUMO, ΔEgap, dipole moment, global softness and hardness, and ESP charge lead to differences in inhibition efficiency. MC results show that the adsorption energy in aqueous environment for Arg, Glu, and Asp is −210.39, −69.22, and −66.88 Kcal mol−1, respectively. Results showed that inhibition efficiency is high when the absolute value of adsorption energy is high. MD simulation show that the peak distance of relative concentration function of Cl- is 17.45, 18.96, and 20.06 Å for Arg, Glu and Asp, respectively. The diffusion coefficient of Cl- in inhibitor film for Arg, Glu, Asp is 5.18 × 10−8, 8.01 × 10−8, 1.22 × 10−7 cm2 s−1, respectively. Both the adsorption energy and the ability to inhibit the diffusion and aggregation of corrosion particles determine the corrosion inhibition performance. The theoretical calculated inhibition ability is Arg＞Glu＞Asp, in good agreement with the experiment results. This paper provides a theoretical reference for further research on amino acid corrosion inhibitors.

Comparison of Adsorption Conformation of Comb‐Shaped Polycarboxylate on Tricalcium Aluminate (100) and Ettringite (100) Surfaces: A Molecular Dynamics Study

AbstractThe adsorption conformations of three comb‐shaped polycarboxylate (PCE) with different numbers of grafted side‐chains on the tricalcium aluminate (C3A) and ettringite surface is studied by all‐atom molecular dynamics (MD) simulations with INTERFACE‐PCFF forcefield. The similarity of absorbed PCEs on both surfaces is backbones of PCEs absorbed on the surface and the side‐chains extended to liquid phase. The difference is that side‐chains of PCEs keep a tilt angle with the C3A crystal but maintain parallel and closer to ettringite crystals. The absolute value of adsorption energy of PCEs on C3A surface is greater than that on ettringite surface, which indicate the stronger interaction between PCEs and C3A than ettringite. PCE with less side chains is favorable for the adsorption due to stronger electrostatic interaction with surface. Adsorption capacity and water‐reducing ability of PCEs are contradictory. Density of water near the solid–liquid interface is more severely decreased by PCE with more side chains. Correlation of the adsorption conformation of PCEs with the flow behaviors of fresh cement paste is summarized.

How does the defect ZnO@Au surface activate the methane via the precursor-mediated mechanism?

It is imperative to explore advanced catalysts that could activate methane in a mild manner. Herein, using density function theory (DFT), we have investigated the activation mechanism for the dissociation of methane, which is adsorbed on the triangle defect surface of ZnO@Au, where the defect ZnO(001) nanosheet is supported by Au(111). We found that the triangle defects induced coordination unsaturated O and Zn on the ZnO@Au are of great importance for this dissociation process, as the coordination unsaturated O and Zn not only can stabilize the methane, but also can polarize the CH bond through the dynamic frustrated Lewis pairs. Compared with perfect ZnO@Au heterojunction, the defect ZnO@Au can activate methane via precursor-mediated mechanism where the activation energy (0.21 eV) is lower than the absolute value of adsorption energy (0.48 eV). Such outstanding activation mainly originates from the electronic interaction between the methane and the coordination unsaturated O as well as Zn. Overall, the result not only provide a vital insight into the catalytic mechanism of the methane activation on ZnO@Au, but also give a new thought to develop catalysts for the facile methane activation.

An alternative electrolyte of deep eutectic solvent by choline chloride and ethylene glycol for wide temperature range supercapacitors

In present work, we present a novel deep eutectic solvent electrolyte for supercapacitors simply by mixing choline chloride and ethylene glycol. It unveils that the molar ratio of choline chloride and ethylene glycol exerts crucial effect on the viscosity, electrical conductivity and capacitive behaviors under extreme conditions (−40–115 °C). With the increase of temperature, the viscosity of electrolyte decreases along with the enhancement of electrical conductivity; similar phenomenon toward capacitive behaviors under extreme conditions also occurs. The electrolyte with molar ratio of 1:2 (choline chloride:ethylene glycol) under 115 °C shows a specific capacitance of 362 F g−1 (with energy density of 50.33 Wh kg−1), which can remain as 102 F g−1 (with energy density of 14.13 Wh kg−1) even at −40 °C. In addition, density functional theory also confirms that the electrolyte with molar ratio of 1:2 has larger absolute value of adsorption energy as 4.42 eV. The present deep eutectic solvent by choline chloride and ethylene glycol can extend to other electrolytes especially for wide temperature range supercapacitors.

Combined Density Functional Theory and Reduction Kinetics Investigation of Enhanced Adsorption of Hydrogen onto Fe2O3 by Surface Modification with Nickel

Based on the density functional theory, the geometric structure, adsorption energy and density of states of H2/α-Fe2O3 (001) system and (H2 + Ni)/α-Fe2O3 (001) system were determined. The results showed that the absolute value of adsorption energy between H2 molecule and α-Fe2O3 (001) surface and the bond length of H2 molecule were increased by the presence of Ni atom. The presence of Ni atom promotes the adsorption of H2 molecule on α-Fe2O3 (001) surface. Reduction behavior of iron and nickel oxides in H2 atmosphere was determined by thermogravimetric analysis. The samples included Fe2O3, Fe2O3-NiO and Fe2O3-Ni systems. The effect of Ni and NiO on the reduction behavior of Fe2O3 was investigated. The ease of reduction within the following three systems decreases sequentially: Fe2O3-Ni > Fe2O3-NiO > Fe2O3. The activation energy of Fe2O3-Ni, Fe2O3-NiO and Fe2O3 systems at two temperature stages (viz. < 400 °C and > 400 °C) were 172 kJ·mol−1, 197 kJ·mol−1 and 263 kJ·mol−1 respectively.

Dewetting Kinetics of Thin Polymer Films with Different Architectures: Effect of Polymer Adsorption

We have investigated the influence of the adsorption process on the dewetting behavior of the linear polystyrene film (LPS), the 3-arm star polystyrene film (3SPS) and the ring polystyrene film (RPS) on the silanized Si substrate. Results show that the adsorption process greatly influences the dewetting behavior of the thin polymer films. On the silanized Si substrate, the 3SPS chains exhibit stronger adsorption compared with the LPS chains and RPS chains; as a result, the wetting layer forms more easily. For LPS films, with the decrease of annealing temperature, the kinetics of polymer film changes from exponential behavior to slip dewetting. As a comparison, the stability of 3SPS and RPS films switches from slip dewetting to unusual dewetting kinetic behavior. The adsorbed nanodroplets on the solid substrate play an important role in the dewetting kinetics by reducing the driving force of dewetting and increase the resistant force of dewetting. Additionally, Brownian dynamics (BD) simulation shows that the absolute values of adsorption energy (e) gradually increase from linear polymer (−0.3896) to ring polymer (−0.4033) and to star polymer (−0.4264), which is consistent with the results of our adsorption experiments.

Catalytic hydrolysis of COS over CeO2 (110) surface: A density functional theory study

Density functional theory (DFT) calculations were performed to investigate the reaction pathways for catalytic hydrolysis of COS over CeO2 (110) surface using Dmol3 model. The thermodynamic stability analysis for the suggested routes of COS hydrolysis to CO2 and H2S was evaluated. The absolute values of adsorption energy of H2O-CeO2 are higher than that of COS-CeO2. Meanwhile, the adsorption energy and geometries show that H2O is easier adsorbed on the surface of CeO2 (110) than COS. H2O plays a role as a bridge in the process of joint adsorption. H2O forms more CeOH groups on the CeO2 (110) surface. CeO2 decreases the maximum energy barrier by 76.15kcal/mol. The migration of H from H2O to COS is the key for the hydrolysis reaction. CO channel is easier to occur than CS channel. Experimental result shows that adding of CeO2 can increase COS removal rate and prolong the 100% COS removal rate from 180min to 210min. The difference between Fe2O3 and CeO2 for the hydrolysis of COS is characterized in the atomic charge transfer and the formation of HO bond and HS bond. The transfer effect of H in H2O to S in COS over CeO2 decreases the energy barriers of hydrolysis reaction, and enhances the reaction activity of COS hydrolysis.