Large Adsorption Energy Research Articles

Insights of the Multimode Orientation-Dependent Initial Oxidation of Aluminum by First-Principles Theory Calculations.

A fundamental understanding of the oxidation mechanisms of aluminum (Al) alloys is of great importance for its applications in corrosion, catalysis, sensors, etc. In this work, we systematically investigated the first-stage oxidation behaviors of three low-index Al facets with O coverage up to two monolayers (ML) by using density-functional theory (DFT). The large negative adsorption energies indicated favorable oxidation on all three facets. However, distinctive structural and electronic changes induced by the adsorption of oxygen have led to different oxidation modes. More specifically, the oxidation process proceeded by "intercalating" into the subsurface region along the (111) plane out of the (110) facet with spontaneous O ingress into (110) far below one ML, as revealed by the electron density distribution, whereas the oxide ad-layer grew in a "layer-by-layer" mode on Al(111) and (001) facets. Moreover, various Al-O complexes with different atomic coordination numbers (CN), configurations, and sizes may be indicators of the tendency of an Al surface to be oxidized. Besides, the oxide phases formed on (111)/(001) and (110) assembled the Al-O bond distribution within α-Al2O3 and γ-Al2O3, respectively.

Comparison of gas-sensitive properties of Pb, Pd and Pt metal-doped Ti3C2X2 for aqueous zinc ion battery H2 gas

This work aims to provide early warning of uncontrolled reactions in aqueous zinc-ion batteries by timely and effectively detecting H2 gas. The large specific surface area and rich pore structure of Ti3C2X2 (X = F, O, and OH) make it a good gas-sensitive sensing material, and the gas-sensitive properties of the material can be improved by metal doping. Therefore, in this paper, the gas-sensitive response properties of Pb, Pd and Pt metal-doped Ti3C2X2 (M-Ti3C2X2) to H2 are compared based on density functional theory (DFT) calculations. The adsorption mechanism was analyzed by structure optimization, density of states, frontier molecular orbital theory and differential charge density, and the results were in high agreement. Doping of three metals, Pb, Pd and Pt, improved the adsorption capacity of Ti3C2X2 for H2 gas to different degrees. The simulation results show that the energy gap of Pb-Ti3C2(OH)2 adsorbed gas changes most obviously, and the maximum change value of energy gap (Eg) is 297.56 %. And Pt-Ti3C2F2 and Pt-Ti3C2O2 adsorbed H2 with large adsorption energies and large charge transfers indicating that they can be used as H2 removers. The energy gaps after the adsorption of H2 by M-Ti3C2O2 are 0.109 eV, 0.163 eV, and 0.082 eV, and the change of Eg is 24.77 %, 16.56 %, and 67.07 %, respectively. The change of Eg for the adsorption of H2 by Pt-Ti3C2O2 adsorbed H2 with a resistivity change of 67.07 %. This is caused by the irreversibility of adsorption due to too strong adsorption resulting in elongation of Pt-O bond length after adsorption. For the detection of H2, the properties of several doped materials were ranked as follows: Pb-Ti3C2(OH)2 > Pt-Ti3C2O2 > Pb-Ti3C2F2 > Pb-Ti3C2O2 > Pd-Ti3C2O2 > Pd-Ti3C2(OH)2 > Pt-Ti3C2F2 > Pt-Ti3C2(OH)2 > Pd-Ti3C2F2. In summary, it is shown that Ti3C2X2 doped with Pb, Pd and Pt metals is a potential H2 gas-sensitive material that can be a new material for online monitoring of fault gas content in aqueous zinc-metal energy storage batteries.

Selection of the Lubricating Oil Components Based on the Molecular Adsorption Characteristics

Abstract The adsorption characteristics of the lubricating oil near the solid surface play crucial roles in the lubricating performance. In this paper, the molecular dynamics simulation implemented by MS software was carried out to reveal the adsorption properties of different lubricants on Fe2O3 surfaces. Several kinds of lubricating oil molecules were employed, namely, n-eicosane, 2, 6, 11, 15-tetramethylhexadecane, 2-decyldecahydronaphthalene and tetradecylcyclohexane. The results show that 2, 6, 11, 15-tetramethylhexadecane and 2-decyldecahydronaphthalene are relatively more favorable as the lubricant components. This is because they both have relatively high adsorption density, low molecular diffusivity and large adsorption energy. These results can provide a theoretical basis for the selection of future lubricant components as well as lubricant performance enhancement for blending.

A computational study of the role of cobalt in thiophene adsorption on small Mo and MoCo clusters as site models for the HDS process

Non periodic density functional theory calculations are used to investigate the role of cobalt atoms in the adsorption of thiophene on small Mo and MoCo clusters. Metallic aggregates play the role of those active sites found in the true catalysts. Two interaction modes between thiophene and metallic sites are considered, namely, the S-mode, in which the organosulfur molecule interacts through the S atom, and the R-mode, in which the interaction takes place through the thiophene ring. A large number of sites, in which thiophene effectively adsorbs, was found, both in the monometallic case and in the bimetallic one. Considerably larger adsorption energies were found when thiophene interacts via the R-mode than when adsorption occurs through the S-mode. The activation of C-S bonds is also more important for R-mode cases than for S-mode ones. Further analysis made on some selected systems and based on density of states and molecular orbital overlap population-projected density of states reveals that thiophene and metallic clusters interact in an energy range around −6.0 eV with respect to the Fermi energy. Bands observed at energies below −6.0 eV correspond to thiophene states that become shifted with respect to the values obtained for isolated thiophene depending on the strength of the interaction. Bands above -6.0 eV describe how C and S atoms interact with Co and Mo ones, providing both bonding and antibonding patterns that helps to understand the overall interaction. Most important is the finding that cobalt atoms seem to play no relevant role during the adsorption of thiophene on metallic sites. Thus, present results obtained using non periodic GGA density functional theory seem to point to cobalt taking part in another step of the overall HDS process, hydrogen adsorption or hydrogen attack to C-S bonds, for instance.

Study on the Gas-Chromic Character of Pd/TiO2 for Fast Room-Temperature CO Detection.

As a widely used support, TiO2 has often been combined with Pd to form highly sensitive gas-chromic materials. Herein, we prepared a series of Pd/TiO2 catalysts with different Pd content (from 0.1 to 5 wt.%) by the impregnation method for their utilization in fast room-temperature CO detection. The detection was simply based on visible color change when the Pd/TiO2 was exposed to CO. The sample with 1 wt.% Pd/TiO2 presented an excellent CO gasochromic character, associated with a maximum chromatic aberration value of 90 before and after CO exposure. Systematic catalyst characterizations of XPS, FT-IR, CO-TPD, and N2 adsorption-desorption and density functional theory calculations for the CO adsorption and charge transfer over the Pd and PdO surfaces were further carried out. It was found that the interaction between CO and the Pd surface was strong, associated with a large adsorption energy of -1.99 eV and charge transfer of 0.196 e. The color change was caused by a reduction in Pd2+ to metallic Pd0 over the Pd/TiO2 surface after CO exposure.

Influence of defect and doping on the sensitivity and adsorption capacity of Zr2CO2 toward PH3 gas

In this study, the potential application of the Zr2CO2-MXene structures as PH3 sensors and adsorbents for industrial or living applications was investigated using the first-principles approach of density functional theory (DFT). The adsorption of PH3 on pristine, O-defected, and transition metal (TM; such as Cr, Mn, Fe, Co, Y, Mo, Ru, Rh)-doped Zr2CO2 structures was explored. The results showed that the introduction of TM dopant improved the Zr2CO2 activity more than the O-vacancy. The large adsorption energy, short interaction distance, and high charge transfer suggested chemisorption of PH3 molecules on TM-doped Zr2CO2. After the PH3 molecule was adsorbed, the band gap of Zr2CO2 with O-vacancies, Co-doped Zr2CO2, and Ru-doped Zr2CO2 decreased by 0.132 eV, and increased by 0.065 eV, 0.073 eV, respectively. The changes in band gap generated an electrical signal that were used for PH3 detection; thus, Zr2CO2 with O-vacancies and Co– and Ru-doped Zr2CO2 can be used as effective PH3 sensors because of their high sensitivity. Fe- and Rh-doped Zr2CO2 also showed promising function as adsorbents for PH3 gas molecules because of their high adsorption stabilities and long recovery times. After adsorption of six PH3 molecules, their adsorption energies on Fe- and Rh-doped Zr2CO2 were −1.142 eV and −1.135 eV, with recovery times of 1.49 × 107 s and 1.12 × 107 s, respectively. The findings of this study offer novel insights for the development of MXene-based sensors and adsorbents.

Porphyrin like porous fullerene functionalized with Ga as an effective adsorbent for the removal of methylene blue from wastewater effluent

Removal of dyes is a significant aspect of environmental remediation to ensure clean water and atmosphere. In this study, we report Ga decorated porphyrin like porous fullerene (Ga@C24N24) for effective removal of cationic dye (methylene blue) using density functional theory calculations. The calculations show that the Ga are strongly anchored at the surface of the C24N24 system with stronger binding energies and larger positive charges. The molecular dynamics simulations evince that the Ga@C24N24 are thermally stable and withstand high temperatures as 500K. The application of Ga@C24N24 as adsorbent for the removal of MB dye shows that the dye could strongly adsorbed over the Ga@C24N24 surface with stronger electrostatic covalent bonds and larger adsorption energies (-2.71 and -1.89 eV for MB@Ga-C24N24 from N site and S site) compared to bare C24N24 system. The electron density difference, partial density of states, and atom in molecule analysis give evidence of the presence of stronger electrostatic covalent bonds between the Ga@C24N24 and MB. This stronger bonding leads to the chemisorption of MB over the Ga@C24N24 surface. The maximum uptake capacity analysis shows that the studied adsorbent can successfully adsorbed 6MB molecules. The solvation effect decreases the desorption time of the MB molecules from Ga@C24N24. These results show that this study will help the experimentalists to explore the Ga@C24N24 system as a new metalloid doped adsorbent for the removal of toxic pollutants from wastewater.

Gas sensitivity research of transition metal (Fe, Zr, Ta, Tc) doped boron nitride nanosheets to indoor toxic gases (CH2O, NH3, Benzene): A DFT perspective

Indoor air quality affects human health, with CH2O, NH3 and Benzene being the three most common indoor toxic gases. In this work, we investigated the adsorption of transition metal (Fe, Zr, Ta, Tc) doped boron nitride nanosheets (BNNSs) for three indoor toxic gases based on density functional theory (DFT). Through a series of analyses after simulation, the results show that the adsorption of pristine BNNSs for the three toxic gases is low, whereas the adsorption of transition metal doped BNNSs for all the three gases are significantly enhanced. Among them, Ta-BNNSs is the structure with a large change in band gap after adsorption of CH2O and Benzene. For NH3, the band gap change after adsorption of Tc-BNNSs is the largest. We have analyzed the recovery time of these three adsorption systems at 298 K, 398 K and 498 K. The results showed that the recovery time of Ta-BNNSs for adsorption of CH2O or Benzene at all three temperatures was large, while the recovery time of Tc-BNNSs at 498 K was small. Thus Tc-BNNSs are a potentially recyclable NH3 sensor material. Finally, the relative adsorption energy analyses showed that Fe-BNNSs had large adsorption energies for all three toxic gases at room temperature and the desorption temperatures were all around 700 K. Therefore, Fe-BNNSs are promising as a recyclable adsorbent material for the three toxic gases.

Atomic-level into the microscopic mechanism of gold capture by FeS during gold collection in matte process

Understanding the microscopic mechanisms involved in gold capture by FeS at the atomic level is crucial for optimizing the matte process and improving the gold recovery from gold concentrate containing arsenic and antimony. Herein, the DFT method was employed to explore the adsorption structure and electronic characteristics of a gold (Au) atom on the FeS surface. Furthermore, the effects of Fe/S vacancy and As/Sb dopant on Au adsorption were also investigated. The results reveal that the FeS(100) with S termination exhibits the smallest surface energy (0.56 J/m2) and possesses the highest stability amongst the low-index surfaces. Furthermore, the Au atom exhibits a preference for adsorption on the Fe-bridge site of FeS(100) through chemisorption due to the formation of a strong Au-Fe metallic bond, large adsorption energy (−5.40 eV), and small adsorption distance. Moreover, the presence of S vacancy enhances the Au capture capability of FeS(100) with an adsorption energy of −6.35 eV, while the Fe vacancy slightly weakens it. Additionally, the doping of As and Sb enhances the adsorption of Au atoms on FeS(100), and the Sb doping showcases a more distinct enhancement in Au capture efficiency. The findings of this work contribute to the advancement of matte processing technology, enabling enhanced gold recovery and potentially opening new avenues for the treatment of refractory gold ores.

Dry reforming of methane over Ni5 nanocluster supported on double perovskite surface − A DFT study

The opportunity for efficient hydrogen extraction from natural gas through perovskite-supported Ni5 nanocluster has been investigated using first-principles calculations. The reaction dynamics of dry reforming of methane (DRM) has been studied, and all the elementary steps are assessed to locate the transition states. The obtained results demonstrate a high affinity of CH4 and CO2 towards the supported nanocluster as predicted by reasonably large adsorption energies. Chromium and Molybdenum on the perovskite surface play an essential role, in conjunction with Nickel, in methane CH bond activation. Ni2Cr and Ni2Mo are identified as the sites where methane reaction begins and ends, or vice versa. The dissociation of CO2 is also facilitated by the nanocluster, with the rate-limiting step in the two pathways being CH4 dissociation. The study suggests that decorating the anode with Ni-nanoclusters can effectively promote hydrogen extraction from hydrocarbon fuels in solid-oxide fuel cells.

Nanosheets adsorption and antiviral activity of Favipiravir drug against envelope proteins of yellow fever virus: DFT and molecular docking simulation study

Our previous research investigated the delivery of Favipiravir (FAV) drug through the encapsulation of FAV into 1D nanomaterials (NMs), AlN, BN, and carbon nanotubes, now we evaluated the possibility of using 2D NMs carbon nanosheets (GPNS), boron nitride nanosheets (BNNS), and aluminum nitride nanosheets (AlNNS) as drug delivery systems. The adsorption of FAV drug in its two tautomeric forms over the surfaces of these NSs is conducted. The adsorption energies are in the range of − 0.681 to − 2.469 eV. FAV binds to BNNS and GPNS through stacking interactions, while it chemisorbs to AlNNS. NCI and QTAIM analyses confirmed the dominance of vdW interactions. The recovery times over NSs were shorter than those inside NTs, and they indicated that NSs are better for drug release while NTs bind better and have larger adsorption energies. MD simulations revealed that FAV showed a good level of resistance to yellow fever virus (YFV) infections.

Ti3C2Tx (T = F, O, OH) as a sensor for dissolved gas in transformer oil: A theoretical study

Power transformer is the hub of power grid energy transmission, and its safe and reliable operation is very important to power grid. In this paper, based on density functional theory, Ti3C2Tx (T = F, O, OH) material was used as sensing material. The adsorption models of Ti3C2Tx and dissolved characteristic gases (H2, CH4, C2H4, C2H6, C2H2, CO, and CO2) in transformer oil are constructed. The adsorption distance, bond length change, adsorption energy, charge transfer and density of states (DOS) of the adsorption system were analyzed. The results showed that the gases can adsorb on the surface of Ti3C2Tx spontaneously. Specifically, CO2, CO, C2H2 and C2H4 exhibit a strong adsorption effect on Ti3C2(OH)2, forming hydrogen bonds or chemical bonds, accompanied by large charge transfer and adsorption energy, indicating Ti3C2(OH)2 shows a good sensing performance for these gases.

Adsorption behavior of gas molecules on B and Mo co-doped graphitic carbon nitride: A first-principles study

Adsorption mechanism studies of toxic gases (CH2O, SO2, NH3, CO, NO, and NO2) on pristine, one B-atom and Mo-atom (1B/Mo) and two B-atom and Mo-atom (2B/Mo) co-doped g-C3N4 were investigated based on the density functional theory. It is shown that gases adsorbed on the 1B(2B)/Mo-g-C3N4 surface exhibit a variety of bandgap types such as magnetic half-metal, magnetic metal, and magnetic semiconductor, and the magnetic properties change considerably. The partial density of states suggests strong hybridization between gas molecules with Mo-4d (B1-2p and B2-2p) and C-2p (N-2p). NH3 gas adsorbed on the 1B(2B)/Mo-g-C3N4 surface acts as a donor and the remaining five gas molecules act as acceptors. CH2O gas adsorbed on 1B/Mo-g-C3N4 has suitable adsorption energy, large charge transfer, short recovery time, and large conductivity change. Therefore 1B/Mo-g-C3N4 can be used as a good sensor to detect CH2O. Lower sensitivity, long recovery times, or insignificant conductivity changes make 1B/Mo-g-C3N4 unsuitable for the detection of CO, NO, NH3, and SO2 gases. However, 1B/Mo-g-C3N4 can be used as a one-time detection for NO2 gas. The recovery time of gases adsorbed on the surface of 2B/Mo-g-C3N4 ranges from 1.93 × 1020 h to 6.43 × 1068 h. However, the large adsorption energies (−2.12 eV to −4.99 eV), the high sensitivity, and the high electrical conductivity allow the use of 2B/Mo-g-C3N4 as a disposable assay for gas molecules.

High switching characteristics and sensing-performance improvement of two-dimensional MN4 (M = Be, Mg, Ga) monolayer based nanodevices

Beryllium tetrazolium nitride (BeN4) has recently been synthesized under high pressure by laserheated diamond anvil electrodes as a new class of two-dimensional layered materials. Inspired by this, we perform first-principles calculations to investigate the electronic transport properties of MN4 (M = Be, Mg and Ga) monolayers and their gas sensing properties towards nitride-gases (NH3, NO2, NO). The obtained results show that BeN4 exhibits semi-metallic properties, MgN4 is a semiconductor with a bandgap of 0.13 eV, and the GaN4 monolayer presents strong metallic properties. Interestingly, the BeN4 and MgN4 monolayers are found to have anisotropic Dirac cones. The MN4-based 2D devices all exhibit excellent conductance as well as strong anisotropic transport, with maximum switching ratios of 107 and 104 for MgN4 and BeN4, respectively. The adsorption properties indicate that the adsorption of NH3, NO2, and NO molecules on MN4 monolayers are all chemisorptions, with the system owning much larger adsorption energies and bader charge transfers of the NO2 and NO molecules than those for the NH3 molecules, suggesting the MN4 monolayer has strong selective adsorption and responsiveness to NO2 and NO molecules. The designed gas sensor based on MgN4 show good response characteristics for NO molecules, as evidenced by the maximum current changes before and after adsorption of 30.31 µA, respectively. In summary, MN4 (M = Be, Mg and Ga) monolayers can be important candidates for high switching ratio devices and for the detection and trapping of toxic gas molecules NO.

Transition-metal-doped Hf2CO2 as a promising sensor for methane: a DFT study

Density functional theory (DFT) methods were used to study the atomic and electronic structures of methane molecules adsorbed on pristine, vacancy-defective, and transition-metal (TMs: Mn, Fe, Y, Mo, Ta, W)-doped Hf2CO2. The interaction distance between the methane molecules and original substrate was large, and the adsorption energy was small, suggesting that the a physisorption adsorption. After introducing O-vacancy, the adsorption of CH4 changed into chemisorption. Through the doping with TM dopants, the methane molecule adsorbed onto the Ta-doped Hf2CO2 exhibited the highest stability and the largest adsorption energy. In addition, the W-doped Hf2CO2 changed from being a semiconductor to being a conductor after the adsorption of methane molecules onto the material; this phenomenon suggests that the change can be used as a signal for sensors in detecting methane gas. These results are expected to provide new insights into the design of gas sensors based on MXenes materials.

Computational insights of promising Pd atomic clusters modified WS2 for detecting environmentally toxic gases

Developing highly sensitive, power-efficient, and recoverable materials are significant for the detection of toxic gases in the environment. Herein, a comprehensive computation of the CH4, CO, H2S, NH3, NO, and NO2 adsorption performance for the intrinsic and Pd atomic clusters decorated WS2 (Pdn/WS2, n = 1–4) was carried out using density functional theory. The larger adsorption energies and more charge transfer indicate that Pdn/WS2 species are more sensitive than the intrinsic WS2. Remarkably, Pd2/WS2 and Pd3/WS2 exhibit distinguished adsorption performance, suggesting that Pd2/WS2 and Pd3/WS2 are the potential ideal candidates for gas sensors. It is also noticed that combined with the moderate adsorption energies, relative high charge transfer, and short recovery time, the Pd2/WS2 and Pd3/WS2 are ideal candidates as CH4 gas detection with the excellent sensitivity and rapid response in coal mines at room temperature. This finding paves the way to develop high-sensitivity gas sensors, making them suitable for the gas sensing application.

Adsorption of NO and NO2 on MoSeS/GaN heterojunction: a first-principles study

The adsorption behaviors of gas molecules such as Cl2, CO, NO, NO2 and SO2 on MoSSe/GaN, as well as their adsorption energies, charge transfer and adsorption distances are investigated based on the first-principles calculation. The large adsorption energies of Cl2, NO, NO2 and SO2 on MoSSe/GaN indicate that the gas molecules have strong interaction forces with MoSSe/GaN. Probing the changes in the electronic structure, the adsorption of NO and NO2 on MoSSe/GaN introduces magnetism into their systems and reduces the band gaps. The magnetism mainly originates from the O atoms in NO and NO2, while the decrease of the band gap is due to the hybridization of orbitals near the bottom of the conduction band and the top of the valence band with the p orbitals of Ga atoms in MoSSe/GaN. This suggests that MoSSe/GaN can be applied to detect NO and NO2 gas molecules and has potential as a semiconductor gas sensor for these gases.

First-principles calculation of electronic properties and diffusion barriers of Sc2CCl2 and Sc2CF2 for metal (Li, Na, K) ion batteries

MXenes have emerged as promising candidate for energy storage devices because of their superior properties. In this work, the electronic properties, low open circuit voltage (OCV) and diffusion barrier of Li, Na, K adsorption on Sc2CCl2 and Sc2CF2 monolayers are investigated by density functional theory. The most stable adsorption site is confirmed because of the shortest adsorption height and largest adsorption energy. The adsorptions of Li/Na/K on Sc2CCl2 and Sc2CCF2 induce the semiconductor–metal transition. Na-Sc2CF2 and Li-Sc2CF2 have higher theoretical capacity (CM), low open circuit voltage (OCV) and diffusion barriers, so they are more suitable as anode materials for Na-ion and Li-ion batteries. The analysis of charge transfer indicates that the adsorbed atoms in Sc2CF2 monolayer lose more electrons than the adsorbed atoms in Sc2CCl2 system because of stronger electronegativity of F.

Improvement in efficiency of MoS2 nanoflower based ethylene gas sensor on transition metal doping: An experimental and theoretical investigation

There is an immense need for inexpensive, accurate, and repeatable ethylene sensors for post-harvest management. This paper presents resistive-type sensors based on transition metal (Ni, Fe, Co) doped molybdenum disulfide (MoS2) nanoflowers synthesized via simple hydrothermal route. A comparative study of sensing properties of pristine MoS2 and doped (Ni, Fe, Co)-MoS2 was performed in natural ambient conditions. The results reveal that Ni-doped MoS2 shows the optimized result in sensitivity as well as lower detection limit, compared to other three materials. Density functional theory (DFT) studies were carried out to evaluate interaction of ethylene molecules with MoS2 and doped MoS2. The sensing mechanism for all the materials was investigated in terms of adsorption energy, density of states (DOS), and charge transfer. The calculated results indicate large adsorption energy and higher charge transfer in the case of Ni-doped MoS2 supporting the experimental findings.

Enhancing the carbon dioxide sensing performance of LaFeO3 by Co doping

Owing to the poor oxidizing and reducing properties of carbon dioxide (CO2), there are few materials suitable for developing CO2 semiconductor gas sensors, among which LaFeO3 (LFO) has been proven to have CO2 sensing properties. To enhance the CO2 sensing performance of LFO, a Co doping strategy is proposed in this work. Specifically, the LFO and LaCo0.1Fe0.9O3 (LCFO) nanoparticles were prepared via a simple sol-gel method, and the corresponding LFO and LCFO sensors were fabricated. The test results showed that the LCFO sensor exhibited wide detection range (25–10,000 ppm CO2), fast response/recovery time (6/42 s), and higher response (6.69% to 1% CO2) than that of LFO sensor at the optimal working temperature of 220 °C (51.9% relative humidity (RH)). In addition, the LCFO sensor showed good resistance to wide humidity range of 0–86.7% RH. Finally, the reasons for the enhanced CO2 sensing performance of LCFO were analyzed combining characterization and theoretical calculation, which could mainly be attributed to the enhancement of oxygen vacancy and large adsorption energy caused by Co doping. This work provides a useful strategy to develop high-performance semiconductor CO2 gas sensor.