High Adsorption Energy Research Articles

Au, Ag, Pb, Pt −doped MoTe2 monolayer as a novel sensor for dissolved gases (CH4, and C2H2): A first-principles study

In this study, C2H2 and CH4 gas molecules adsorption on intrinsic MoTe2 and Au, Ag, Pb, Pt doped MoTe2 by density functional theory (DFT). The adsorption energy, bond length, charge transfer, PDOS and work function are calculated, it can be proved that Ag-MoTe2 have excellent C2H2 and CH4 adsorption performance than Au-MoTe2, Pb-MoTe2 and Pt-MoTe2. However, C2H2 gas molecule can be chemisorbed onto the doped Ag in the modified MoTe2 with a high adsorption energy of 0.923 eV, capturing approximately 0.65 e from the sensing material. Ag-MoTe2 has the better C2H2 and CH4 adsorption performance than Au-MoTe2, Pb-MoTe2 and Pt-MoTe2, as evidenced by the strong overlap of the s, p, d orbitals and the significant reduction of the energy gap from the PDOS. Therefore, suggesting that the Ag-MoTe2 could have potential application in the capture and dissociation of C2H2 and CH4.

High-performance fluoride removal by Fe/N co-doped microporous carbon: Mechanism of capacitive deionization with FeNx sites

Fluoride pollution is becoming increasingly serious with industrial growth. Controlling fluoride pollution have become important environmental issues of global concern. Transition metal nitrides are excellent CDI electrode materials due to their excellent conductivity and electrochemical stability. In this study, FeNx/C was synthesized as an electrode material for using the capacitive deionization (CDI) technique to achieve the effective removal of fluoride ions from wastewater. Its high specific surface area (463.278 mg/g) and high capacitance (44.29 F/g) were demonstrated and it had a high adsorption capacity of 158.33 mg/g. FeN3 and FeN4 were used as the main sites as capacitive deionization for removing fluoride from the water by chemisorption and hydrogen bonding. The higher adsorption energy by density functional calculation also indicated that the existence of Fe-N coordination bond effectively improved its electrosorption capacity. This study is beneficial to provide references and research ideas for removing fluoride in the CDI field.

VS2/ Blue Phosphorus composites for high speed lithium ions storage

Based on first-principles calculations, the potential of the H-VS2/Blue P heterojunction composite as a lithium-ion battery anode is systematically investigated. This heterojunction composite enhances the stability of the VS2 structure and increases its overall mechanical strength.The Young's modulus of the composite is 144.69 N/m, markedly exceeding that of the single layer. Furthermore, it modifies the electronic properties of the Blue P monolayer, converting it from an insulating to a metallic state.The H-VS2/Blue P heterojunction composite exhibits a high lithium adsorption energy of 4.34 eV and a low diffusion barrier of 0.15–0.19 eV, facilitating rapid lithium-ion migration during charge/discharge cycles. And the theoretical capacity of the heterojunction composite is up to 1211 mAh/g. The combination of elevated adsorption energy, low diffusion barrier, and high theoretical capacity indicates that the H-VS2/Blue P heterojunction composite is a highly promising anode material for lithium-ion batteries.

Removal of phosphate from wastewater using zirconium/iron embedded chitosan/alginate hydrogel beads: An experimental and computational perspective

Adsorptive removal of phosphate plays a crucial role in mitigating eutrophication. Herein, the Zr/Fe embedded chitosan/alginate hydrogel bead (Zr/Fe/CS/Alg) is reported as an effective phosphate adsorbent. This polymer nanocomposite is synthesized by the in-situ reduction of the metals on the polymer matrix. The synthesized adsorbent was characterized by the FTIR, SEM-EDX, TGA, BET, and XPS. The adsorbent showed a maximum phosphate adsorption capacity of 221.72 mg/g at pH 3. The experimental data fit well with the Freundlich isotherm and pseudo-second-order kinetics model, indicating a heterogeneous multilayer surface formation and a chemisorption-dominated adsorption process. Density Functional Theory (DFT) and Monte Carlo (MC) calculations revealed high negative adsorption energy due to the chemisorption of phosphate on the adsorbent. Hence, the major interactions such as electrostatic attraction, hydrogen bonding, and inner-sphere complexation of phosphate adsorption and Zr/Fe/CS/Alg hydrogel beads were investigated from the experimental and computational analysis. The negative values of thermodynamic parameters indicated a spontaneous, exothermic, and less random adsorption process. The synthesized adsorbent exhibited excellent selectivity toward phosphate and maintained 73 % efficiency after six adsorption/desorption cycles. The Zr/Fe/CS/Alg hydrogel beads reduced the phosphate concentration in real wastewater samples from 19.02 mg/L to 0.985 mg/L, suggesting that these nanocomposite hydrogel beads could be a promising adsorbent for real-world applications.

Vitreous silica supported metal catalysts for direct non-oxidative methane coupling

Direct non-oxidative methane coupling (NMC) transforms methane into valuable chemicals and hydrogen, which is a promising pathway to boost industrial decarbonization. The reaction, however, is challenged by high C-H bond activation temperature, catalyst coking, and low selectivity towards hydrocarbon products. Here we studied the efficacy of five vitreous silica supported 3d transition metal (Mn, Fe, Co, Ni, and Cu) catalysts (denoted as M/SiO2-v) for NMC. These catalysts were prepared by flame fusion of mixtures of quartz and metal silicate precursors. The metal species in the as-synthesized catalysts were fully or partially oxidized, with their stability following the order of Mn > Fe ≈ Co > Ni > Cu in the NMC reaction. The Cu species has low methane reaction rate, due to the high adsorption and dissociation energies of methane. The Mn and Ni species have high methane reaction and coke formation rates, which is supported by easy kinetics of methane deep dehydrogenation to carbon. In contrast, Fe and Co species showed the best hydrocarbon product selectivity. Particularly, the Co species emerged as the optimal catalyst for NMC, showcasing a balanced methane activation, hydrocarbon formation, and low coke yield. The relationship between the evolved metal species under reaction conditions and their NMC performance was discussed. The present study screens and provides effective catalyst formulations for NMC reactions.

Pore Space Characteristics and Migration Changes in Hydrocarbons in Shale Reservoir

The pore structure and mineral characteristics affect the accumulation and migration of hydrocarbons in shale, which determines the production capacity of shale oil. In this study, shale samples from the Chang 7 member of the Ordos Basin in China were selected to investigate the pore space characteristics, the effect of hydrocarbon accumulation on pore heterogeneity, and the hydrocarbon migration changes based on fractal theory, and a series of experiments were conducted involving X-ray diffraction (XRD), total organic carbon (TOC), Soxhlet extraction, and low-temperature nitrogen (N2) and carbon dioxide (CO2) adsorption. Then, the factors affecting extraction efficiency in shale pores were discussed. The interparticle pores contributed most to the accumulation of shale oil, and the organic matter (OM) pores contributed positively to the adsorption of hydrocarbons. The accumulation of hydrocarbons in the pore space did not increase the heterogeneity of the shale pore structure. The contents, states, and positions of hydrocarbons changed during the extraction process. Hydrocarbons were redistributed on the pore surface after Soxhlet extraction, and the heterogeneity of hydrocarbon adsorption and pore surface roughness were improved. Some heavy hydrocarbons and adsorbed components were pyrolyzed, resulting in the gradual escape of the adsorbed layer in the large pores. However, the free oil in the small pores diffused to the large pores and reaggregated on the surface, restoring a stable adsorption layer. The extraction rate was closely related to the pore throat structure and the wettability of mineral surfaces. The configuration between pores and throats had a crucial influence on the extraction rate. A high proportion of meso-pores, which effectively connect micro- and macro-pores, had a higher diffusion efficiency and a higher extraction rate. The OM pores with high energy adsorption were located in the micro-pores, and the shale oil existed in a dissolved state with high mobile capacity. The wettability of mineral surfaces affected the adsorption behavior during extraction, and strong oil wetting promoted hydrocarbon re-adsorption in clay minerals, so that the volume of micro-pores was smaller after extraction.

The relationship between the high-frequency performance of supercapacitors and the type of doped nitrogen in the carbon electrode

Nitrogen doping has been widely used to improve the performance of carbon electrodes in supercapacitors, particularly in terms of their high-frequency response. However, the charge storage and electrolyte ion response mechanisms of different nitrogen dopants at high frequencies are still unclear. In this study, melamine foam carbons with different configurations of surface-doped N were formed by gradient carbonization, and the effects of the configurations on the high-frequency response behavior of the supercapacitors were analyzed. Using a combination of experiments and first-principle calculations, we found that pyrrolic N, characterized by a higher adsorption energy, increases the charge storage capacity of the electrode at high frequencies. On the other hand, graphitic N, with a lower adsorption energy, increases the speed of ion response. We propose the use of adsorption energy as a practical descriptor for electrode/electrolyte design in high-frequency applications, offering a more universal approach for improving the performance of N-doped carbon materials in supercapacitors

Theoretical and experimental studies on the electrochemical behavior of steel in HCl solution in the presence of two bio-inhibitor mixtures

In this new study, the inhibitory effectiveness of two bio-inhibitor mixtures has been studied on the corrosion characteristics of carbon steel in an HCl environment. The inhibitors were derived from a plant seed (quinoa seed-QS) and an insect extract (Oestrus ovis larvae-OOL). The total inhibitor concentration was a variable factor even the ratio of bio-inhibitor concentration was a fixed parameter. The electrochemical behavior of steel substrate was investigated through the Tafel polarization and electrochemical impedance spectroscopy measurements. Fourier transform infrared spectroscopy and field emission scanning electron microscopy were performed to identify bonds and analyze the morphology of the corroded surface of the steel. Additionally, molecular dynamics (MD) simulation and quantum calculations were applied to investigate the inhibitory influence of utilized bio-inhibitors. The experimental results indicated that the corrosion resistance decreased to 85 % when the optimum total concentration of the bio-inhibitor was 1 g L−1. The Langmuir model was used to illustrate the adsorption mechanism on the steel surface when physical adsorption occurred. Quantum chemical calculations revealed that the QS-inhibitor adsorbed more effectively onto the metal surface than the OOLE-inhibitor, due in part to a lower energy gap and higher HOMO energy. MD simulation and Monte Carlo calculations further confirmed that the QS-inhibitor was adsorbed on the Fe (110) surface with higher adsorption energy than the OOLE-inhibitor.

Study on highly selective NO2 gas sensors based on (Fe, Mo)-doped monolayer WSe2

The two-dimensional (2D) material WSe2 is frequently employed in gas sensors due to its excellent electrical properties. However, the weak interaction between the pristine WSe2 and gas molecules limits its application. Therefore, in this paper, the adsorption behavior of transition metal X (X = Fe, Mo) atom-doped monolayers WSe2 on H and O atoms and molecules of NO2, HCN, and CO gases is investigated to gain insights into the physical mechanisms of adsorbent-substrate interactions. Doping significantly improves the adsorption properties between the substrate and the gas molecules, with the best adsorption showing for NO2 gas molecules and O atoms. The relationship between transition metals and the improvement of adsorption performance is explored by the center position of transition metal d orbitals in different systems, and it is found that the higher the center position of the transition metal d band, the stronger the adsorption between adsorbent and substrate. Compared to pristine WSe2, Mo atom doping in the transition metal doped system has higher adsorption sensitivity to gas molecules and exhibits highly selective adsorption and chemisorption behaviors through high adsorption energies and electron transfer to NO2 molecules. It is demonstrated that X (X = Fe, Mo) doped WSe2 can be used as a gas-sensitive material for efficient gas detection.

The adsorption characteristic of As2, As2O3, Pb, PbO on double transition-metal pyridine-tetranitrogen-annulene membrane

The arsenic and lead compounds produced by coal combustion have serious impacts on human health and the environment, making it urgent to simultaneously remove arsenic and lead. In this work, the adsorption characteristics of As2, As2O3, Pb and PbO on 2D Double Transition-Metal Pyridine-Tetranitrogen-Annulene membrane (DTM-PTA, TM=Co, Cu, Zn) are investigated through density functional theory calculations. The adsorption energy, bonding mechanism, electronic and magnetic properties are analyzed in detailed. Firstly, the distribution density of transition metal atoms as adsorption active sites is high, which is conducive to the adsorption of molecules. The results demonstrate that the DCo-PTA is a promising adsorbent for simultaneously removing As2, As2O3, Pb and PbO with highest adsorption energy. According to the variation of magnetic moment, DCu-PTA and DZn-PTA can detect the adsorption of PbO in the mixture of As2, As2O3, Pb and PbO. In addition, the adsorbed molecules can regulate the array of spin electron. Although temperature hinders the adsorption process of molecules, DCo-PTA can still spontaneously adsorb these molecules within the temperature range of 300–1000 K. This indicates that DCo-PTA is an excellent adsorbent which can work in high temperature.

Highly sensitive room-temperature ammonia sensor based on PbS quantum dots modified SnS2 nanosheets and theoretical investigation on its sensing mechanism by DFT calculation

Real-time accurate detection of hazardous gases is an urgent issue for industrial development and safeguarding public health. However, large-scale application of gas sensors in the network requires low-power consumption of sensing device for successful integration in smart platform. Although traditional ammonia (NH3) sensors based on semiconductor materials possess various advantages, it still remains the challenge in high operating temperature. Herein, PbS quantum dots (QDs) with higher adsorption energy were used to sensitize SnS2 nanosheets with electron transport capacity to achieve excellent NH3 sensing performance. PbS QDs with an approximately diameter of 10 nm were dispersed on SnS2 nanosheets with an average thickness of 14 nm. Impressively, the optimal sensor employing PbS QDs/SnS2 nanocomposites exhibited high sensor response of 8.5 to 100 ppm NH3, good response/recovery times of 9 s/720 s, as well as excellent selectivity, repeatability, and long-term stability at room temperature of 25 °C. The adsorption behavior and electronic structure of PbS QDs/SnS2 nanocomposites before and after NH3 adsorption were investigated based on density functional theory calculation. Moreover, the sensing mechanism of PbS QDs/SnS2 nanocomposites was also discussed. The designed PbS QDs/SnS2 nanocomposites hold considerable promise as a candidate in realizing superior NH3 sensing performance at room temperature.

Selective regulation of nanosheets inside or outside carbon nanoboxes for advanced supercapacitors

Rational structure control is an effective route to boost electrochemical performance of energy storage materials and devices. Confining composite materials with core–shell structure in hollow carbon nanomaterils is challenging and valuable in the field of energy storage. Herein, driving inward formation of core–shell structured Fe3O4@MnO2 in hollow carbon nanoboxes is achieved for superior supercapacitor electrodes. It’s found that when small Fe3O4 nanoparticles are reserved in carbon nanoboxes in advance, the MnO2 nanosheets only grow on the internal Fe3O4 nanoparticles to form Fe3O4@MnO2 core–shell structure in the carbon nanoboxes (Fe3O4@MnO2@C NBs) or only on the outer shell of carbon nanoboxes (Fe3O4@C@MnO2) or on both Fe3O4 nanoparticles and the carbon shell (Fe3O4@MnO2@C@MnO2), which can be selectively regulated. The density functional theory (DFT) calculation reveals that Fe3O4@MnO2@C NBs have higher conductivity, higher adsorption energy and lower diffusion energy barrier for sodium ions due to the core–shell structure of Fe3O4@MnO2 in carbon nanoboxes, which could promote the reaction kinetics efficiently. The asymmetric quasi-solid supercapacitor based on Fe3O4@MnO2@C NBs electrode achieves an energy density of 49.75 Wh kg−1 at a power density of 820 W kg−1 and demonstrates excellent stability. The route may provide a method for achieving complex internal structure control in hollow carbon material to enhance the electrochemical properties.

Assessment of doped graphene in the removal of atrazine from water

Atrazine is a widely used toxic herbicide that poses a threat to both the environment and human health. This study investigates the removal of Atrazine from water through armchair-hexagonal hexagonal graphene quantum dots (AHEX) simulations. The investigations are performed using density functional theory at the exchange–correlation hybrid functional B3LYP/3-21G level of theory. The activity of pristine AHEX, with a total dipole moment of 0.0 (debye), is enhanced by doping with boron (B), nitrogen (N), and sulfur atoms (S), resulting in increased total dipole moments of 8.99, 5.29, and 4.14 Debye respectively. This enhancement occurs without any structural deformation due to the doping process. Our results show significant adsorption capacity of the doped nanographene for Atrazine, evidenced by the high adsorption energies of 0.52 eV for boron, 0.62 eV for nitrogen, and 2.97 eV for sulfur. Charge distribution on the atrazine complexes further confirms effective interaction, with values of 0.03, − 0.018, and 0.032 (e). UV–vis spectroscopy reveals that the prominent absorption peaks of boron and nitrogen-doped samples, initially at ~ 658.8 and 431 nm, undergo a redshift to ~ 676 and 444.3 nm after adsorption, respectively. This redshift aligns with the dominant excitation moving to lower energies following adsorption. Conversely, the sulfurated nanographene shows a blue shift from 980.66 to 485.41 nm. These findings highlight the potential of doped nanographene as an effective treatment for atrazine-contaminated water.

The invisible hand of pre-adsorbates: Unveiling oxygen's role in sculpting Cu–TiN interfaces

Copper (Cu) binding to titanium nitride (TiN) surfaces is important for applications in catalysis, sensing, and electronics. However, achieving controlled and stable Cu attachment remains challenging. In this study, Density Functional Theory with Hubbard U corrections (DFT + U) is employed to investigate how pre-adsorbed oxygen (O) and sulfur (S) influence Cu attachment and the resulting interfacial properties. Contrary to initial expectations, our calculations reveal that the presence of pre-adsorbed O and S significantly weakens the Cu–TiN interface. Direct adsorption of Cu on the TiN surface, without pre-adsorbed species, results in a much higher adsorption energy (−13.94 eV), demonstrating stronger interfacial stability compared to systems with O (−2.06 eV) or S (−1.84 eV) pre-adsorption. Although pre-adsorbed O and S can modify the interface's electronic structure, the introduction of these species ultimately weakens the Cu–TiN interaction rather than enhancing it, as initially hypothesized. Analysis of the density of states (DOS) and charge transfer shows that direct Cu–TiN bonding maintains a more robust interaction, making it more suitable for applications requiring strong metal-ceramic interfaces. These findings highlight the critical role of surface chemistry in controlling the strength of Cu–TiN interfaces. The use of DFT + U calculations provides valuable insights into the bonding mechanisms and electronic changes at these interfaces, informing future design strategies for Cu–TiN systems with tailored properties for advanced technological applications.

Mn-Ce solid solution growth on Mn2O3 surface to form heterostructure catalysts with multiple active sites for toluene degradation

A solid solution-heterostructure catalyst with abundant active sites was successfully constructed in this study by in situ growth of Mn-Ce solid solution on the surface of Mn2O3. The solid solution structures with optimum physical and chemical properties were synthesized initially by controlling the Mn-Ce ratios. Subsequently, the reaction time was controlled to realize the orderly growth of the solid solution on the Mn2O3 surface. The catalyst (M−CeMn0.5) with solid solution-heterostructure formed by the reaction of Ce3Mn1 and Mn2O3 for 0.5 h could reach more than 90 % toluene degradation rate at 183 °C and was operated continuously for 15 h without deactivation. XRD showed that the appropriate reaction time resulted in the active components on the catalyst surface exhibiting lower crystallinity and reduced grain size. The reduction capacity (2.28 → 10.47 mmol/g) and the mobility of lattice oxygen were significantly enhanced in the M−CeMn0.5 catalyst compared to the Mn-Ce solid solution. Meanwhile, a high content of low valent metal ions (Ce3+/Ce4+ 0.33, Mn3+/Mn4+ 1.64) and reactive oxygen species (Oads/Olatt 0.53) were also present on the catalyst surface. The DFT demonstrated that the Mn atoms and Mn-O bridge sites on the solid solution surface exhibited high adsorption energy values for toluene (−0.8402/-0.8406 eV) and oxygen (−1.6546/-1.661 eV) molecules. The TEM indicated that lattice distortion and oxygen vacancies were formed at the interface between the solid solution and Mn2O3 at the interface. The synergy of multiple active sites favors the generation of reactive oxygen species and thus promotes p-methyl dehydrogenation. Meanwhile, the high mobility of lattice oxygen facilitates the breakage of benzene ring. This study provides a new strategy for the synthesis of efficient Mn-Ce-based catalysts.

Synergistic degradation of p-nitrophenol using peroxymonosulfate activated with a bimetallic Mn3O4–Cu2O catalyst: Investigation of strong interactions between metal oxides

The use of efficient, eco-friendly catalysts is essential for activating peroxymonosulfate (PMS) to degrade organic contaminants in aqueous media. In this study, we developed a novel approach to fabricating bimetallic MnCu catalysts (Mn:Cu molar ratios: 10:1, 5:1, 3:1, and 2:1) comprising tetragonal Mn3O4 and cubic Cu2O. MnCu-5:1 exhibited superior catalytic activity for the degradation of p-nitrophenol (PNP) using PMS because of the synergistic interplay between Mn and Cu. Experimental and density functional theory (DFT) calculation data revealed that the mixed valence states and strong interactions between Mn and Cu in the MnCu-5:1 system increased the electron transfer efficiency and promoted electron transfer to PMS. The results of quenching experiments elucidated a primary radical mechanism and minor nonradical pathway for the PNP degradation over the MnCu-5:1/PMS system. DFT calculations confirmed a relatively high adsorption energy of the Mn3O4–Cu2O (MnCu) composite, indicating enhanced catalytic performance. The superior reactivity of the composite was verified by analyzing its density of states and electrostatic difference potential. Our findings offer fresh perspectives for harnessing the synergistic potential of less toxic mixed metal oxides for controlling catalytic properties and help achieve a better understanding of the activation mechanism for contaminant degradation over MnCu catalysts.

Calcium oxide adsorption of gas phase PCDD/Fs and its impact on the adsorption properties of activated carbon

Calcium oxide (CaO), utilized in semi-dry/dry desulfurization systems at municipal solid waste incineration (MSWI) plants, demonstrates some capability to remove polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study assessed the gas-phase PCDD/F removal performance of CaO, activated carbon (AC) and CaO-AC mixtures. Alone, CaO achieved removal efficiencies of only 31.9% for mass and 50.8% for I-TEQ concentration. However, CaO-AC mixtures exhibited significantly higher efficiencies, reaching 96.0% and 92.5% for mass and I-TEQ concentrations, respectively, surpassing those of AC alone, which were 74.7% and 58.5%. BET analysis indicated that CaO's limited surface area and pore structure are major constraints on its adsorption performance. Density functional theory (DFT) calculations revealed that the π-π electron donor-acceptor (EDA) interaction enhances the adsorption between AC and PCDD/F, with adsorption energies ranging from −1.02 to −1.24 eV. Additionally, the induced dipole interactions between CaO and PCDD/F contribute to adsorption energies ranging from −1.13 to −1.43 eV. Moreover, with increasing chlorination levels, PCDD/F molecules are more predisposed to accept electron transfers from the surfaces of AC or CaO, thereby facilitating adsorption. The calculation for mixed AC and CaO showed that CaO modifies AC's properties, enhancing its ability to adsorb gas phase PCDD/Fs, with the higher adsorption energy and more electrons transfer, aligning with gas phase PCDD/Fs adsorption experiments. This study provides a comprehensive understanding of how CaO influences the PCDD/F adsorption performance of AC.

Synthesis of Pd-Doped SnO2 and Flower-like Hierarchical Structures for Efficient and Rapid Detection of Ethanolamine.

In this study, we successfully synthesized a Pd-doped SnO2 (Pd-SnO2) material with a flower-like hierarchical structure using the solvothermal method. The material's structural proper-ties were characterized employing techniques such as XRD, XPS, FESEM and HRTEM. A gas sensor fabricated from the 2.0 mol% Pd-SnO2 material demonstrated exceptional sensitivity (Ra/Rg = 106) to 100 ppm ethanolamine at an operating temperature of 150 °C, with rapid response/recovery times of 10 s and 12 s, respectively, along with excellent linearity, selectivity, and stability, and a detection limit down to 1 ppm. The superior gas-sensing performance is attributed to the distinctive flower-like hierarchical architecture of the Pd-SnO2 and the lattice distortions introduced by Pd doping, which substantially boost the material's sensing characteristics. Further analysis using density functional theory (DFT) has revealed that within the Pd-SnO2 system, Sn exhibits strong affinities for O and N, leading to high adsorption energies for ethanolamine, thus enhancing the system's selectivity and sensitivity to ethanolamine gas. This research introduces a novel approach for the efficient and rapid detection of ethanolamine gas.

Research on Residual Gas Adsorption on Surface of Hexagonal Boron Nitride-Based Memristor.

As a promising nonvolatile memory device with two ends, the memristor has received extensive attention for its industrial manufacture. Density functional theory was used to analyze the adsorption properties of residual gas on hexagonal boron nitride (h-BN)-based memristor model surfaces with Stone-Wales-5577 grain boundary defects [h-BN(SW)]. First, by calculating the adsorption energy, geometric parameters, and charge transfer, we identified the most stable adsorption sites for hydrogen atoms (H-TB1) and H2 molecules (H2-TN2). We observed a tendency toward chemisorption for hydrogen atoms and physical adsorption for H2 molecules at these sites. Furthermore, two coadsorption configurations were formed by introducing H2 molecules and hydrogen atoms into single adsorption configurations: namely H-TB1_H2-TN1TN2 and H2-TN2_H-TB1TN1TN3. In the case of hydrogen-based configuration, there is weak dissociation of the H2 molecule, which does not facilitate hydrogen atom adsorption. However, adjacent hydrogen atoms tend to form stable dimers, while excess hydrogen atoms have a tendency to weakly chemisorb in the case of H2-based configuration. The pristine h-BN surface is more favorable for hydrogen atom migration compared to the h-BN(SW) surface due to its higher adsorption energy. On the h-BN(SW) surface, hydrogen atoms tend to migrate inward from the center of adjacent heptagonal boron nitride rings while coadsorption has a minimal impact on their vertical migration as well as that of H2 molecules. This work provides theoretical insights into the H/H2 trace gas interaction during h-BN wafer-level fabrication for memristor devices.

DFT study of gas responses to CH4, H2S, and CO on TM Atom (Sc, V, Cr, Mn)-modified HfSe2 monolayers

In this study, the adsorption of waste gases (CH4, H2S, CO) generated during the extraction, processing, and utilization of natural gas on TM atom (Sc, V, Cr, Mn)-modified HfSe2​ surfaces were analyzed using Density Functional Theory (DFT) calculations. Initially, the doping effects of the four TM atoms were examined, followed by a detailed investigation of the adsorption of these three gases in terms of adsorption energy, band structure, density of states (DOS), charge transfer, and recovery time. Among the TM atoms, Sc doping was found to be the most favorable due to its highest adsorption energy. However, in subsequent gas adsorption processes, it was observed that V and Mn-modified HfSe2 surfaces exhibited better adsorption performance for H2S and CO. Furthermore, it was discovered that at high temperatures, V-HfSe2 can function as a gas sensor for CO, while at room temperature, V-HfSe2 and Mn-HfSe2 can serve as high-precision real-time monitoring sensors for H2S and CO, respectively.