Stable Adsorption Configurations Research Articles

Study of carbon monoxide adsorption on B-N doped hydrogenated Sn nanoribbons towards nanosensor applications

This study utilized Van der Waals corrected density functional theory (DFT) and nonequilibrium Green's function (NEGF) to consider the potential of hydrogenated Armchair stanene nanoribbons of width 8 (HASnNR(8)) for CO gas detection. The study analyzed the most stable adsorption configuration, charge transfer, electronic transport, adsorption energy, sensitivity and electronic properties of CO gas molecules on HASnNR(8), both before and after B-N doping. The results showed that B-N doping led to a significant increase in adsorption energy and a gap opening at the Gamma point, resulting in semiconductor behavior. Analysis of charge transfer indicated that CO molecules acted as donors to HASnNR(8). Moreover, there was a notable change in the transmission functions of CO adsorbed on B-N doped HASnNR(8) compared to pure HASnNR(8). Based on the I-V characteristics, the study concluded that CO molecules could be easily detected after B-N doping. Finally, the study performed a recovery time analysis and sensitivity CO adsorbed on bare and B-N doped HASnNR(8) surfaces, with the results indicating that B-N doped HASnNR is a promising material for CO molecule sensing applications.

Metal oxide modified MCM-41 on simultaneous removal of HF and HCl: Experimental and theoretical studies

To address the issue of harmful gases Hydrogen fluoride (HF) and hydrogen chloride (HCl) in metallurgical waste gas, this study utilized metal oxide modified molecular sieve (MCM-41) for their simultaneous removal. The adsorption and removal of HF and HCl are mainly influenced by alkaline sites and pore structure, with alkaline sites having a greater impact. MgO affects the alkaline site strength and pore structure, thereby facilitating the removal of HF and HCl. On the surface of the adsorbent, HF and HCl react to form MgF2 and MgCl2, which gradually reduces the adsorbent's performance. HF and HCl have a higher adsorption strength on the MgO surface, and the H…O interaction causes a more stable adsorption configuration. There is a competitive adsorption effect between HF and HCl, with HF having a preference for adsorbing on the MgO surface over HCl. The adsorption energies of HF and HCl are unlimited by adsorption effects. When the O atom in MgO is replaced by HF and HCl, Mg-F bonds, Mg-Cl bonds, and H-O bonds are formed, resulting in the formation of MgF2, MgCl2, and H2O. HF is easier to prioritize removal than HCl

First-principles study of adsorption, dissociation, and diffusion of hydrogen on α-U (110) surface

According to the equilibrium crystal shape of α-U, the surface of α-U (110) is more stable and has a larger area fraction than α-U (001). Therefore, the adsorption, dissociation, and diffusion behaviors of H atoms and H2 molecules on the α-U (110) surface were systematically studied by first-principles calculations. The results show that there are only two stable adsorption sites for the H atom: the surface short-bridge site (SB1) and the subsurface short-bridge site (SB2). The adsorption of H2 molecules is divided into chemical adsorption of dissociated H2 molecules and physical adsorption of undissociated H2 molecules, and the LB2-ParL adsorption configuration is the most stable adsorption configuration for H2 molecule adsorption, with an adsorption energy of −0.250 eV. The work function and charge transfer show that adsorption of the H atom or H2 molecule leads to an increase in the work function value of the α-U (110) surface, which enhances the electronic stability of the α-U (110) surface. The projected density of states shows that when the H atom or H2 molecule is close to the α-U (110) surface, the 1s orbital electrons of the H atom will hybridize with the 5f/6d orbital electrons of the nearby surface and subsurface U atoms, and new hybridized orbital peaks appear near the −4.5 eV or −7.3 eV energy level. The climbing image nudged elastic band study shows that the surface free H atoms are very easy to diffuse between the surface short-bridge sites and the subsurface short-bridge sites but the diffusion between the short-bridge site and the triangular center site is extremely difficult.

A first principle study of the heterogeneous catalysis mechanism of NaCl/KCl powder in suppressing combustion

Studies have shown that alkali metal ultrafine water mist additives, such as NaCl and KCl, are highly effective in inhibiting explosion and combustion. In order to further study the heterogeneous catalytic inhibition of NaCl and KCl, the 100 most stable surfaces of NaCl and KCl were selected as the research objects. Three typical free radicals (H, O, OH) were selected as surface adsorbents with different coverages, and the most stable adsorption sites and configurations were located. The NEB method was used to calculate the minimum energy paths of H and O recombination on two surfaces. The molecular dynamics of two surface combustion radicals were simulated by the AIMD method. The results indicated that NaCl and KCl have strong adsorption capacity for the O free radical, while the two surfaces have weaker adsorption capacity for the H free radical; NaCl and KCl, two catalytic active substances, which can eliminate H radicals through the continuous adsorption of H free radical to generate H2, and H radical is inactivated. The catalytic fire-extinguishing effect by eliminating O free radical is weak. Molecular dynamics calculations on the two surfaces revealed that Cl atoms precipitate differently under the adsorption of various radicals.

Investigating the Mechanism of Diethylenetriamine Pentamethylene Phosphonic Acid as a Depressant for Calcite Flotation of Fluorite.

Fluorite and calcite have been attracting research attention for a long time. This paper reports on an investigation of the use of diethylene triamine pentamethylphosphonic acid (DTPMPA) as a chelating inhibitor. DTPMPA was used as a chelating inhibitor to study the flotation, separation, and adsorption behaviors of fluorite and calcite minerals. The microflotation experiment showed that the maximum separation of fluorite and calcite can be achieved with a DTPMPA dosage of 1.5 × 10-4 mol/L under weakly alkaline conditions (pH = 8). Zeta potential measurement, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to confirm that DTPMPA was adsorbed on the surface of calcite, inhibiting NaOl adsorption. Additionally, density functional theory calculations showed that oxygen in the DTPMPA phosphate group formed the most stable bidentate binuclear adsorption configuration by chelating with calcium on the calcite surface. Through detection analysis and simulation calculations, the results showed that DTPMPA exhibited significantly weaker adsorption on fluorite compared to that on calcite, highlighting its selective inhibition ability on calcite.

Dissociative Adsorption of Hydrogen Molecules at Al2O3 Inclusions in Steels and Its Implications for Gaseous Hydrogen Embrittlement of Pipelines

Hydrogen embrittlement (HE) of steel pipelines in high-pressure gaseous environments is a potential threat to the pipeline integrity. The occurrence of gaseous HE is subjected to associative adsorption of hydrogen molecules (H2) at specific “active sites”, such as grain boundaries and dislocations on the steel surface, to generate hydrogen atoms (H). Non-metallic inclusions are another type of metallurgical defect potentially serving as “active sites” to cause the dissociative adsorption of H2. Al2O3 is a common inclusion contained in pipeline steels. In this work, the dissociative adsorption of hydrogen at the α-Al2O3(0001)/α-Fe(111) interface on the Fe011¯ plane was studied by density functional theory calculations. The impact of gas components of O2 and CH4 on the dissociative adsorption of hydrogen was determined. The occurrence of dissociative adsorption of hydrogen at the Al2O3 inclusion/Fe interface is favored under conditions relevant to pipeline operation. Thermodynamic feasibility was observed for Fe and O atoms, but not for Al atoms. H atoms can form more stable adsorption configurations on the Fe side of the interface, while it is less likely for H atoms to adsorb on the Al2O3 side. There is a greater tendency for the occurrence of dissociative adsorption of O2 and CH4 than of H2, due to the more favorable energetics of the former. In particular, the dissociative adsorption of O2 is preferential over that of CH4. The Al-terminated interface exhibits a higher H binding energy compared to the O-terminated interface, indicating a preference for hydrogen accumulation at the Al-terminated interface.

Reticular poly(pyrrole methylene)s synthesized by synchronous-cross-linking process for the capture of Hg(ll) from water: Adsorption performance and mechanism

The development of novel high-capacity porous materials is critical to advancing the treatment of mercury-containing wastewater. In this study, two reticular poly(pyrrole methylene) adsorbent materials (PPB2E and PPD2E) were synthesized by a synchronous cross-linking method and successfully employed for Hg(II) adsorption in water. Their adsorption performance on Hg(II) in water was investigated. The results showed that PPB2E and PPD2E have large specific surface areas (535.43 m2/g and 523.23 m2/g, respectively) and are abundant microporous, with the molecular chains partially cross-linked and partially oxidized to form a conjugated structure. The adsorption of Hg(II) by the two adsorbents could reach equilibrium within 120 min, and the adsorption behavior followed the pseudo-second-order model. The adsorption isotherms were more in line with the Langmuir model, and the maximum adsorption capacities of PPB2E and PPD2E for Hg(II) were up to 1537.46 mg/g and 1511.94 mg/g (298 K, pH = 4), respectively. The two adsorbents exhibited excellent adsorption selectivity for Hg(II) in mixed metal salt solutions with good cycling stability. The primary adsorption mechanism of the synthesized materials for Hg(II) was jointly verified by characterization and DFT calculations: Hg(OH)2 molecules were adsorbed by forming hydrogen bonds with pyrrole N and carboxyl O in the adsorbents. Compared with other metal ions, the materials have more active sites for Hg(II) adsorption, higher utilization, and easier formation of stable adsorption configurations, thus exhibiting highly selective adsorption.

A theoretical approach to the corrosion inhibition of iron in acidic solution by a green formulation derived from Nigella sativa L seeds oil

A theoretical approach combining density functional theory (DFT) computation, Monte Carlo (MC) methods, and molecular dynamics (MD) simulations was used to investigate and validate the iron corrosion inhibition performances in the acidic medium of a green formulation based on the oil extracted from Nigella sativa L. DFT calculations allowed to determine the energetic, global, and local chemical reactivity parameters. The most stable adsorption configuration of the fatty acids components of the Nigella sativa L. formulation was determined by the Monte Carlo methods with the adsorption locator module and by molecular dynamics simulations. Results indicated that all the compounds are absorbed with a totally flat orientation on the first layer of the metal surface.The active sites of molecules were effectively established by using DFT through the analysis of frontier molecular orbitals (FMO), the Hirshfeld population analysis (HPA), the electrostatic potential (ESP), molecular electron density analysis (MED), and Fukui indices (FI). The solvent effect was investigated by using the conductor-like polarizable continuum model (CPCM). Protonation effects were also analysed through the protonation energy (PE), the proton affinity (PA), and the absolute gas phase basicity (GB). The formation of a coating on the iron surface validated the good protective action of the green formulation derived from Nigella sativa L.The computational and theoretical approaches substantiate our experimental electrochemical and spectroscopic studies [1].

Periodic DFT calculations for the heterogeneous formation of 2-chlorothiophenoxy radical from 2-chlorothiophenol on Cu(111) surface in fly ash

Copper plays a crucial role in the heterogenous dissociation of chlorothiophenols (CTPs) to form chlorothiophenoxy radicals (CTPRs), which is the initial and critical step in the formation of polychlorinated thianthrenes/dibenzothiophenes (PCTA/DTs). Here, first-principles calculations were performed to investigate the activity of Cu(111) surface towards the formation of adsorbed 2-CTPR from 2-CTP. The interaction between 2-CTP and Cu(111) surface was explored to find stable adsorption configurations. Besides, the decomposition routes of 2-CTP on the Cu(111) surface were further explored. Moreover, the effects of water on the formation of absorbed 2-CTPR on the Cu(111) surface were examined. Our results demonstrate that the flat adsorption of 2-CTP on the surface with adsorption energy in the range of −33.21 kcal/mol to −28.37 kcal/mol is more stable than the vertical adsorption with adsorption energy ranging from −23.53 kcal/mol to −13.38 kcal/mol. The Cu(111) surface catalyzes the conversion of 2-CTP into the adsorbed 2-CTPR with a modest energy barrier of 9.46 kcal/mol. Furthermore, water molecules exhibit stronger catalytic activity in this process with a decreased energy barrier of 5.87 kcal/mol through “water bridge” and hydrogen bonding. Specifically, the water accepts the hydrogen atom from 2-CTP and donates another hydrogen to the surface via “water bridge”. This research provides a molecular-level understanding of the heterogeneous formation of PCTA/DTs by fly ash, suggesting novel approaches for control strategy and legislation of dioxin analogues.

A DFT investigation of hydrazine nitrate dissociation mechanism on MoN(0 0 1)

Hydrazine nitrate (HN) is an important additive for hydrazine-based monopropellant. In this work, density functional theory (DFT) was adopted to calculate the decomposition process of HN components on MoN (001) catalyst surface. Firstly, two stable adsorption configurations of hydrazine nitrate were identified and determined the catalytic decomposition pathway of the thermodynamically favorable configuration. Pathway analysis revealed that the nitric acid group preferentially decomposes in all pathways. Moreover, due to the high activation and desorption energies, H2O molecules are more likely to be generated in the gas phase rather than preferentially adsorbed on the surface. By calculating the activation energies of each elementary reaction, it can be concluded that the cleavage of the NO bond in NO3– with the barrier energy of 0.32 eV plays a decisive role in the decomposition of the HN molecule.

The Adsorption Behavior of Hydrogen on the PuO2(111) Surface: A DFT+U Study

Based on density functional theory, a first-principles study of the adsorption behavior of hydrogen atoms on the PuO2(111) surface is carried out in this work. Models for three different surface morphologies of PuO2(111) are established. It is found that the surface with the outermost oxygen atom (sub outer Pu atom) morphology has the best stability. Based on this model, the adsorption energy, bader charge, and electronic density of the states of a hydrogen atom at different adsorption sites are calculated. Finally, we analyzed the process of hydrogen dissociation into hydrogen atoms on the surface using the cNEB method. The results indicate that the top position of the outermost oxygen atom and the bridge position of the second outermost plutonium atom are relatively stable adsorption configurations, where hydrogen atoms lose electrons and release heat, forming O-H bonds with oxygen atoms. The density of states of O-p orbital electrons will undergo significant changes, reflecting the hybridization of O-p and H-s orbital electrons, forming a stable bonding effect. The dissociation of hydrogen molecules into two hydrogen atoms adsorbed on the top of oxygen atoms requires crossing an energy barrier of 1.06 eV. The decrease in total energy indicates that hydrogen tends to exist on the PuO2(111) surface in a hydrogen atom state. The research results lay the foundation for theoretically exploring the hydrogenation corrosion mechanism of the PuO2(111) surface, providing theoretical support for exploring the corrosion aging of plutonium oxide, predicting the material properties of plutonium oxide under extreme and special environments.

Adsorption mechanism and compatibility of environmentally friendly insulating gas CF3I and its main decomposition products with Al and Cu(1 1 1) surfaces

Good environmental compatibility and excellent insulation performance make trifluoroiodomethane (CF3I) have the potential to replace SF6 in gas-insulated equipment. The gas–solid compatibility of CF3I, its main decomposed products (I2, C2F6, C3F8, C2F4, HF, CF3H, COF2), and environmental molecule H2O with the Al and Cu(111) surfaces is investigated based on first-principles calculations. The most stable adsorption configurations of Al and Cu(111) surfaces adsorbed by all gas molecules are constructed, and the interaction types between gas molecules and two metal surfaces are determined by adsorption energy (E ad), charge transfer, and charge density difference. The absolute E ad of CF3I and I2 adsorbed on Al(111) surfaces are 4.09 and 3.76 eV, respectively. In contrast, the absolute E ad of other gases adsorbed on Al(111) surfaces do not exceed 0.99 eV, indicating that CF3I and I2 have strong chemical interactions and poor gas–solid compatibility with Al(111) surfaces, while other gases exhibit good gas–solid compatibility with the Al surface. The absolute E ad of I2 (1.15 eV) adsorbed on Cu(111) surface is significantly larger than that of other gases-adsorbed systems (not exceeding 0.99 eV) including CF3I-adsorbed system, proving that the gas–solid compatibility of I2 with Cu(111) surfaces is worse than that of other gases. In addition, the reasons for the different compatibility of CF3I with Al and Cu(111) surfaces are analyzed in depth through the density of states.

Understanding the hydrolysis mechanism of cyanogen chloride on copper and chromium surfaces

AbstractCyanogen chloride (CNCl) is a highly toxic agent, but there is currently a lack of research on the catalytic hydrolysis reaction of CNCl on metal surfaces. The low efficiency and unclear mechanism of CNCl hydrolysis reaction have hampered the development and enhancement of protective equipment. In this work, we focused on investigating the adsorption behavior and hydrolysis mechanism of CNCl on copper and chromium surfaces through first‐principle methods. Our findings revealed the most stable adsorption configuration of CNCl on metal surfaces and its terminal flipping behavior during the hydrolysis process. Subsequently, we designed and studied a series of CNCl hydrolysis reaction pathways, primarily involving C‐terminal intermediates. Notably, the adsorption energy of CN* displayed strong linear scaling relationships with that of other key reaction intermediates, directly influencing the activity and selectivity of CNCl hydrolysis. By employing the adsorption energy expression based on the intrinsic properties of substrates and adsorbates, we extended them to identify the adsorption energies of various complex reaction intermediates involved in CNCl hydrolysis. This comprehensive understanding of the reaction mechanism on metal surfaces provides a theoretical foundation and innovative perspective for the further exploration of CNCl hydrolysis catalysts.

ADSORPTION OF DIBENZOXAZEPINE GAS ON TRANSITION METAL-DOPED SILICON CARBIDE NANOTUBES: A THEORETICAL INVESTIGATION

Dibenzoxazepine (CR) molecule is highly toxic gas, therefore, the development of highly sensitive materials for their adsorption and detection is desirable. Density functional theory (DFT) calculation was performed to study the adsorption behavior of CR gas on the pristine and transition metal (TM=Sc, Ti, Y, Zr, La, and Hf) –doped silicon carbide nanotubes (SiCNT) at both Si and C sites. The most stable adsorption configurations, adsorption distances, adsorption energies, charge transfers, energy gaps, orbital distributions, and density of states are obtained to understand the impacts of CR gas on the adsorption abilities and electronic properties of the pristine and TM–doped SiCNT surfaces. The results show that the pristine SiCNT exhibits low adsorption ability to CR gas. Conversely, the SiCNT doping with TM atom at Si and C sites enhances adsorption ability to CR gas. The strong adsorption of CR gas on TM–doped SiCNT surface is due to more favorable orbital interaction as well as shorter adsorption distance and larger charge transfer than pristine SiCNT. Moreover, the results reveal that the adsorption of CR gas significant changes in the electronic properties of TM–doped SiCNT. Therefore, the doping of TM atoms on SiCNT at both Si and C sites could enhance the adsorption ability and suitable for use as sensors for detecting CR gas.

Ab-initio electronic, magnetic, and optical properties of Fe-phthalocyanine on NiO(001)

The adsorption of organic molecules on antiferromagnetic surfaces forms interfaces with potential applications in organic spintronics devices. Molecules modify the dispersion of spin excitations in the substrate through charge transfer and crystal deformations, and offer the possibility to couple them to light excitations. Here, we follow an ab initio approach to the study of the interface between the magnetic organo-metallic molecule Fe-phthalocyanine and the (001) surface of NiO. By applying Hubbard-corrected density-functional theory (DFT+U) calculations we determine the most stable adsorption configuration as that with the molecule lying flat with Fe above a surface O atom. We find a strong hybridization between Fe orbitals and surface ones, with the Fe spin coupled antiferromagnetically to subsurface Ni through the O atom. Moderate changes to the magnetic structure of the components and charge displacements are shown. Optical spectra show reduced absorption onsets and are investigated for the possibility of a coupling with the system spin properties.

First-principles study of CO2 hydrogenation on Cd-doped ZrO2: Insights into the heterolytic dissociation of H2.

Cd-doped ZrO2 catalyst has been found to have high selectivity and activity for CO2 hydrogenation to methanol. In this work, density functional theory calculations were carried out to investigate the microscopic mechanism of the reaction. The results show that Cd doping effectively promotes the generation of oxygen vacancies, which significantly activate the CO2 with stable adsorption configurations. Compared with CO2, gaseous H2 adsorption is more difficult, and it is mainly dissociated and adsorbed on the surface as [HCd-HO]* or [HZr-HO]* compact ion pairs, with [HCd-HO]* having the lower energy barrier. The reaction pathways of CO2 to methanol has been investigated, revealing the formate path as the dominated pathway via HCOO* to H2COO* and to H3CO*. The hydrogen anions, HCd* and HZr*, significantly reduce the energy barriers of the reaction.

Elucidating the corrosion inhibition mechanisms: A computational and statistical exploration of the molecular structure-efficiency relationship for phenolic Schiff bases in acidic medium on the mild steel surface

This study investigated mild steel corrosion inhibition using four Schiff bases in a theoretical framework. The study used statistical analysis to relate the experimental inhibitor's efficacy to theoretical data, revealing the corrosion inhibition process. Density functional theory (DFT) was used to assess the global reactivity of the four inhibitors' neutral, protonated, and complex forms. Where, Fukui functions were used for local reactivity study of the four inhibitors in neutral and protonated forms. To study system dynamics at the inhibitor-steel contact, a Monte Carlo simulation was performed. The experimental and quantum results are strongly correlated when the global quantum features of the neutral and protonated forms, such as the dipole moment μ, EHOMO, and ELUMO, are examined. The PA and pKa protonation parameters demonstrate that the protonation of the compounds strongly influences the inhibition efficiency. According to Fukui functions, the amine function (N) is the highest nucleophilic reactivity, making it highly sensitive to electrophilic attack, for all four inhibitors. The stability and predominance of complex forms in the medium were interpreted using thermodynamic characteristics of PSBi-FeCl2 complexes. Monte Carlo simulation yielded the most stable adsorption configurations, which were geometrically and energetically examined to explain experimental data. QSAR shows a significant linearity between theoretical parameters and experimental inhibitory efficiency.

Adsorption behavior of H4POn (n = 8,7,6) groups on the F,Si-doped reduced CeO1.979(100) surfaces investigated by first-principles calculations

The adsorption properties of F,Si-doped reduced CeO1.979(100) surfaces to H4POn (n = 8,7,6) groups on KDP surfaces were studied by DFT+U method. The adsorption potential energy surfaces, stable adsorption configurations and electronic structures were calculated and analyzed. The results indicate that the surface O vacancy formation energy (EOv) was lower than the subsurface EOv on three CeO1.963(100) surfaces. The EOv of Ce0.926Si0.074O1.963(100) surface decreased, while the EOv of CeO1.926F0.037(100) surface increased. The adsorption energy of reduced CeO1.979(100) surface was higher than that of CeO2(100) surface. The stable adsorption sites of H4PO8, H4PO7, and H4PO6 groups have changed from Obri, Cebri, and Ot sites on CeO2(100) surface to Ot, Ot, and Obri sites on reduced CeO1.979(100) surface. Compared to CeO1.979(100) surface, the number of Ce-O(H4POn) bonds increased to 4 after H4POn groups were adsorbed on CeO1.958F0.021(100) surface, and the number of Ce-O(H4POn) bonds decreased by 1 after H4POn groups were adsorbed on Ce0.979Si0.021O1.979(100) surface. The reduced surfaces adsorbed with H4POn groups exhibited semi-metal properties. In H4PO7 and H4PO6 adsorption systems, the electron cloud presented irregular distribution, the spin up and down electronic states became asymmetric, so the systems appeared a certain magnetism. In symmetrical H4PO8 adsorption systems, the Ce4f and O2p states were closest to the Fermi level, and the Bader charge transfer between bonded Ce and O(H4PO8) atoms was the largest. Density of states of Ce0.979Si0.021O1.979(100) and CeO1.958F0.021(100) surfaces adsorbed with H4POn groups shifted towards high and low energy levels, respectively, indicating that F doping made the adsorption structure more stable.

Crn (n=1–4) clustered (8, 0) single-walled CNT: Comparison of gas-sensitive properties to air discharge pollutants (CO, NOx)

Air is a good insulating medium under normal conditions. The insulation performance of many electrical equipment is closely related to air. The detection of air decomposition pollutants is considered to be one of the effective ways to diagnose the fault of air insulated power equipment. Based on the first-principles, the adsorption and sensing characteristics of Single-walled CNT modified by transition metal clusters (Crn) for air discharge pollutants (CO, NOx) were analyzed. Firstly, through the modeling and analysis of different doping sites, four most stable models of Crn doped SWCNT are obtained, and their resistance is briefly analyzed. On the basis of these four configurations, the most stable adsorption configurations were found. The corresponding adsorption energy, adsorption distance and transfer charge are obtained. Then, the differential charge density, frontier molecular orbitals, adsorption selectivity and desorption properties of each system were analyzed. The result is that Crn-SWCNT surface has a good adsorption capacity for pollutants. The theoretical recovery time is not ideal at room temperature. However, CO can be rapidly desorbed from the surface of Crn-SWCNT at extremely high temperatures. Interestingly, Crn-SWCNT can be used as solid adsorption materials for purifying CO, NOx. This work provides a new idea for clean air to treat air discharge pollutants.

Adsorption and dissociation of CH3SH on FeS surface: A DFT study

Methyl mercaptan (CH3SH) is a common sulfide in oil and natural gas, easily corroded in transportation pipes and storage containers. In this paper, the adsorption and dissociation processes of CH3SH on FeS (0 0 1), (0 1 1), (1 0 0) and (1 1 1) surfaces have been studied by the density functional theory (DFT). And the characteristics of the adsorption and dissociation processes were elucidated. The calculated surface energies show that the order of surface stability is (0 0 1) > (0 1 1) > (1 0 0) > (1 1 1). The stability of CH3SH adsorption is (1 1 1) > (1 0 0) > (0 1 1) > (0 0 1) by the adsorption energy, and the most stable adsorption configurations are obtained. Compared with the changes in electron density and the partial density of states (PDOS) before and after adsorption, there is an obvious electron orbital hybrid phenomenon between CH3SH and FeS (1 0 0), (1 1 1) surface, and its adsorption is stronger than that of the other two surfaces. It can be seen from the calculation of the transition state that the dissociation reaction of CH3SH is endothermic on the (0 0 1) and (0 1 1) surfaces, while the exothermic reaction on the (0 1 1) and (0 0 1) surfaces. CH3SH will dissociate preferentially on the FeS (1 0 0) surface because the reaction of Ea and ΔE on this surface is the smallest. Overall, the adsorption and dissociation processes are exothermic, the increase in temperature makes the crystal surface unstable and susceptible to spontaneous combustion, and the phenomenon occurs first on the FeS (1 0 0) and FeS (1 1 1) surfaces. These findings increase the understanding of the electronic structure and energy of the sulfides' action on the FeS surface and also have a reference value for flame retardant research.