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[Display omitted] • All the formation energies in Sn poor environment are negative, with Fe exhibiting the largest absolute value. • The charge transfer of the Pd-doped S n O 2 (110) system is the greatest. • Fe-doped S n O 2 (110) system (penta-coordinated position) has the highest magnetic moments. Inspired by the unprecedented surface chemical reaction activity of single-atom catalysts (SAC), this research presents a theoretical study on the doping of S n O 2 (110) surface with transition metal group VIII atoms (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt). Using density functional theory (DFT), the formation energy, electronic structure, charge transfer and magnetic moments of the S n O 2 (110) system before and after doping were investigated. The formation energies of the different doped systems vary depending on the doping position. The doping of transition metal (TM) atoms can induce produces both charge transfer and magnetic moment. The charge transfer is largest in the Pd-doped system, with + 0.68 e at the position of the penta-coordinated Sn atom ( S n 5 c position) and + 0.67 e at the position of the hexa-coordinated Sn atom ( S n 6 c position), while the Co-doped system exhibits the smallest charge transfer of + 0.19 e ( S n 6 c position). Fe, Co, Ni, Ru and Os atoms introduce magnetic moments, with the Fe-doped system ( S n 5 c position) having the highest magnetic moments of 2.91 μ B. In the S n O 2 (110) surface system doped with TM atoms, there are varying degrees of orbital overlap between the TM atoms and their surrounding O atoms. This theoretical work provides valuable insights into the physical properties of metal oxide based single-atom catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Among the penta-coordinate Ru, Rh and Pd single atom structure (SAS), Ru-SAS has the lowest formation energy. • Ru-SAS and Rh-SAS enhanced the chemical stability of adsorbed O* (O−) species on SnO 2 (1 1 0). • All three SAS can induce electronic sensitization, while only Ru-SAS and Rh-SAS exhibit chemical sensitization. Surface oxygen species play a key role in determining the chemi-resistive gas sensing performance of SnO 2. Through surface modification, the type of oxygen species at different working temperatures can be modulated, leading to changes in carrier concentration and surface activity. Single atom structures (SAS) hold enormous potential in the gas sensing domain; however, the impact of different SAS on surface oxygen species on SnO 2 remains unclear, resulting in inconsistent improvements in sensing properties. This study conducted a theoretical investigation of different 4d noble metal SAS (Ru, Rh, and Pd) modified SnO 2 (1 1 0) surface, encompassing both electronic and chemical sensitization. All three SAS, when substituting penta-coordinated Sn atom (Sn 5c), can inject holes and create a thicker depletion layer to varying degrees. Ru and Rh SAS can accelerate the decomposition of adsorbed O 2 and O 3. More importantly, Ru and Rh can hinder the combination of adsorbed O* species with adjacent two-coordinated lattice oxygen (O 2c), enhancing the chemical stability of O*, which plays a decisive role in detecting reducing gases, with Ru exhibiting a better effect. This theoretical work not only enhances methods and mechanisms for adjusting surface oxygen species and improving the sensing performance of SnO 2 -based gas sensors, but also provides useful guidance for screening and designing SAS in experimental procedures on different semiconductor metal oxide surfaces. [ABSTRACT FROM AUTHOR]

[Display omitted] Lithium-sulfur (Li-S) batteries are considered as new generation of energy storage which offer cost-effectiveness and high energy density. However, their commercialization is restricted due to a host of challenges associated with the cathode material which usually contains sulfur with several drawbacks, including a low electronic conductivity of sulfur, the 'shuttle effect', and a large volume expansion during discharge. Herein, a novel two-dimensional porphyrin-like square metal organic framework (MOF) was explored as a promising cathode material using first principles density function theory (DFT) assisted by genetic global search. The DFT results show that, among 7 kinds of transition-metal organic framework (TM-MOF), only V-MOF and Ru-MOF is found to possess considerable chemical interactions with S 8 and lithium polysulfides (LiPSs) in both vacuum and in electrolytic solvents, demonstrating distinguishable anchoring performance. The genetic global search and further DFT calculations indicate that the lithiation process on V-MOF exhibited a nearly constant open-circuit voltage of about 1.92 V to 1.95 V, and the theoretical energy density could reach up to 1469 Wh kg−1 when lithiation of S 8 is considered on both sides of the substrate. The volume expansion of V-MOF during discharge is found to be about 34%, much smaller than 80% for solid sulfur. The band structure and density of states of V-MOF suggest metallic properties or a small band gap for bare surface or during the lithiation process. These results indicate that two-dimensional (2D) V-MOFs can serve as high-performance cathode material with distinguished anchoring performance to block polysulfide dissolution and thereby reduce the 'shuttle effect', and help attain ultra-high energy density. Our work points the way for designing and providing experimental realization of 2D layered materials applied in cathode with high energy density and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrochemical nitrogen reduction reaction (NRR) in ambient condition is an efficient and sustainable method to synthesize NH 3. In this work, first-principles study was used to discuss the NRR process on B atom doped SbN monolayer. The adsorption of N 2 on B-Sb 17 N 18 and B-S 18 N 17 was calculated including the adsorption energy, adsorption distance, and the charge density difference (CDD). Five different reaction pathways of NRR were taken into consideration and the stability of B-SbN was investigated. The results show that, because the energy of unoccupied orbital in sp3 hybridization of B atom is much lower than that in 2p z orbitals, the adsorption of N 2 on B-Sb 18 N 17 shows much larger adsorption energy (−1.01 eV with end-on pattern) compared to that of the adsorption on B-Sb 17 N 18. For five different pathways, the 1, 2, and 4 pathways have a smaller limiting potential of about 0.52 V and the limiting step is: *N 2 + H+ + e− → *NNH. The 3 and 5 pathways have a larger limiting potential of 0.57 V with hydrogenation step: *NHNH 2 + H+ + e− → *NH 2 NH 2. The B-Sb 18 N 17 is structurally and thermally stable even at 500 K. Our theoretical prediction indicates that B atom substitutionally doped SbN monolayer can be a kind of high-performance metal-free NRR catalyst for NH 3 synthetization, and the work provides attempts for designing and exploring 2D metal-free NRR catalysts. [ABSTRACT FROM AUTHOR]

Polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) are incompatible with the 4 V class cathodes such as LiCoO2 due to the limited electrochemical oxidation window of PEO. Herein, a number of binders including commonly used binders PEO, polyvinylidene fluoride (PVDF), and carboxyl‐rich polymer (CRP) binders such as sodium alginate (Na‐alginate) and sodium carboxymethyl cellulose, are studied for application in the 4 V class all‐solid‐state polymer batteries (ASSPBs). The results show ASSPBs with CRP binders exhibit superior cycling performance up to 1000 cycles (60% capacity retention, almost 10 times higher than those with PEO and PVDF binders). Synchrotron‐based X‐ray absorption spectroscopy (XAS), morphology studies and density functional theory studies indicate that, with their carboxyl groups, CRPs can strongly bind the electrode materials together, and work as coating materials to protect the cathode/SPE interface. Cyclic voltammetry studies indicate that CRP binders are more stable at high voltage compared to PEO and PVDF. The stability under high voltage and the coating property of CRP binders contribute to stable cathode/SPE interfaces as disclosed by the X‐ray photoelectron spectroscopy and Co L‐edge XAS results, enabling long cycling life, high performance 4 V class ASSPBs. [ABSTRACT FROM AUTHOR]

Polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) are incompatible with the 4 V class cathodes such as LiCoO2 due to the limited electrochemical oxidation window of PEO. Herein, a number of binders including commonly used binders PEO, polyvinylidene fluoride (PVDF), and carboxyl‐rich polymer (CRP) binders such as sodium alginate (Na‐alginate) and sodium carboxymethyl cellulose, are studied for application in the 4 V class all‐solid‐state polymer batteries (ASSPBs). The results show ASSPBs with CRP binders exhibit superior cycling performance up to 1000 cycles (60% capacity retention, almost 10 times higher than those with PEO and PVDF binders). Synchrotron‐based X‐ray absorption spectroscopy (XAS), morphology studies and density functional theory studies indicate that, with their carboxyl groups, CRPs can strongly bind the electrode materials together, and work as coating materials to protect the cathode/SPE interface. Cyclic voltammetry studies indicate that CRP binders are more stable at high voltage compared to PEO and PVDF. The stability under high voltage and the coating property of CRP binders contribute to stable cathode/SPE interfaces as disclosed by the X‐ray photoelectron spectroscopy and Co L‐edge XAS results, enabling long cycling life, high performance 4 V class ASSPBs. [ABSTRACT FROM AUTHOR]

Abstract The density functional theory (DFT) is used to investigate the gas sensing properties of both pristine and n-type InSe monolayers to SF 6 decomposition products. The adsorption energy, electron transfer, the band structure and the density of states (DOS) of both types of InSe monolayers are analyzed. In addition, the response and recovery properties, and the selectivity of these InSe monolayers to five types of gas molecules (SO 2 , SOF 2 , SO 2 F 2 , H 2 S and HF) are investigated. In the study, the n-type InSe monolayers are doped with F and I atom, respectively. The results show that the interactions between the pristine InSe monolayer and the gas molecules are relatively weak. After only being doped with F atom, the chemical interaction between InSe and SO 2 is dramatically enhanced, with significantly increased adsorption energy and enhanced electron transfer. The adsorption of SO 2 also leads to conspicuous changes of electronic properties of the F and I doped InSe monolayers, making the strong n-type properties disappear. The high selectivity and acceptable recovery properties of InSe-F monolayer to SO 2 indicate that it is promising to use the InSe-F monolayer for detecting SF 6 decomposition products. This study provides a theoretical basis for future application of InSe monolayers or ultra-thin InSe based gas sensing devices. Graphical abstract Unlabelled Image Highlights • Pristine InSe monolayer had slight response only to H 2 S but too fast desorption process. • InSe-F monolayer lost its strong n-type property only after adsorbing SO 2. • InSe-F monolayer had high selectivity only to SO 2 and well recovery properties. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cu atom prefers to be adsorbed on the T N site of the pristine InN monolayer. • Cu adatom can adjust the chemical interactions between InN monolayer and different gas molecule. • The desorption time and change of the conductivity was evaluated for future application in gas sensor or adsorbent. Abstract We carried out the first-principle study of four types of SF 6 decompositions adsorbed on pristine and Cu atom decorated hexagonal InN monolayer. The adsorption structures, adsorption energy, electron transfer, band structure, density of states and desorption properties were discussed to evaluate the possible application of InN monolayer in field of adsorbent and gas sensor. The results revealed that the pristine InN monolayer has the largest adsorption energy to SO 2 with evident chemical interactions. The introduction of Cu adatom on InN monolayer significantly enhanced the chemical interactions between the InN monolayer and the SO 2 , SOF 2 , SO 2 F 2 gas molecule but declined the adsorption energy of HF. We also investigated the electronic properties of all adsorption configurations and estimated the desorption time of every gas molecule from pristine and Cu decorated InN monolayer to evaluate the potential application in noxious gas detecting and scavenging in gas insulated switch-gear (GIS). [ABSTRACT FROM AUTHOR]

[Display omitted] • Cr-graphene was used to detect CO and NO x for the first time. • The adsorption properties of Cr-graphene for gases (CO, NO x) were discussed. • The sensing performance of Cr-graphene for gases (CO, NO x) was compared. • This work supports a new idea of detection of PD. The adsorption and sensing abilities of air decomposition components such as CO, NO, and NO 2 on a Cr-graphene monolayer were investigated using the first principles of density functional theory. Firstly, three possible doping points of Cr atoms on the surface of graphene were studied, and the most stable Cr-graphene monolayer was obtained through modeling and computational analysis. Then, various adsorption structures were constructed and optimized based on the model. The most stable adsorption structure of Cr-graphene monolayer for the three characteristic gases was determined by comparing their adsorption energy and other relevant parameters. Furthermore, state density, differential charge, and molecular orbital theory analyze the gas sensing mechanism and desorption time. The results show that the surface of the pristine graphene has a weak adsorption effect on these gases, and the Cr-graphene monolayer has good adsorption performance for the three gases. Although the calculation results show that Cr-graphene monolayer has strong adsorption and gas sensitivity performance for the three components, the recovery performance of the Cr-graphene monolayer needs to be improved because of the immense adsorption energy of Cr-graphene monolayer for the three components. The calculation can provide a theoretical guidance for gas sensors based on graphene and its modified materials. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Four kinds of Ag cluster all loss electrons to graphyne when adsorption. • Ag 1 , Ag 3 or Ag 4 adsorption on graphyne brings strong n-type doping. • The chemical interactions are mainly between the p x –p y π, p z π orbitals of graphyne and the 4d orbitals of Ag cluster. Abstract Based on the density functional theory study, we investigated the adsorption behavior of small Ag n nanoclusters (n = 1 to 4) on γ-graphyne including the adsorption configurations with the minimum total energy, the charge transfer and charge density. The electronic properties including the band structure and density of states (DOS) were also discussed. The results indicated that Ag 2 cluster had the minimum adsorption energy and charge transfer which might result in difficult adsorption process. Except for Ag 2 , all the introduction of Ag cluster exhibited n-type doping. For different Ag cluster, the interactions of atomic orbitals between Ag and C atom also varied. Our results can have certain guidance meaning for future study of the physical and chemical properties of modified graphyne or other monolayer materials. [ABSTRACT FROM AUTHOR]

We performed density functional theory study on the adsorption properties of five typical SF6 decomposition products in gas-insulated switchgear on single-layer HfS2. The adsorption structure, adsorption energy, and electron transfer were discussed. We also considered the physical and chemical interactions between the adsorbed gas molecule and the HfS2 monolayer with the discussion of the charge density difference configurations, the electron localization functional configurations, and the density of states (DOSs). To assess the sensing property of single-layer HfS2-based gas sensor, we built a simulated device with three parts, including left lead, scattering region, and right lead and the response to different gas molecules was evaluated. The results indicated that the SO2F2 molecule exhibited the largest adsorption energy but the HF molecule had the largest electron transfer. Only H2S adsorption leads to the obvious decrease of the bandgap. All the gas molecules could have chemical interactions with the HfS2 monolayer with different degrees based on the DOS analysis. For the simulated sensing device, according to the nonequilibrium Green’s function method, it showed better response and selectivity in the voltage range between 1.2 and 1.6 V. The device exhibited the maximum current after HF adsorption and the minimum current after SO2F2 adsorption. [ABSTRACT FROM AUTHOR]

In this work, we investigated the adsorption behaviour of sulfur dioxide on pristine and Au dimer decorated γ-graphyne (γ-GY). From comparing the adsorption energy, electron transfer and band gap, the most energetically adsorption configurations were gained. Then we made a further discussion of charge density difference, electron localization function (ELF), band structure, density of states (DOS) to evaluate the chemical and physical interactions between the SO 2 and the γ-GY. The results indicated that the SO 2 adsorption on the pristine γ-GY just exhibited van der Waals force with very weak chemical interactions. But SO 2 could be adsorbed on Au dimer decorated γ-GY with relatively stronger chemical interactions due to the larger adsorption energy, larger electron transfer, the obvious change of SO 2 molecular orbitals and many hybridizations between the Au and the S atom in DOS. Because of the unchanged band gap of Au dimer decorated γ-GY, it is more suitable for Au 2 -GY to be applied in QCM gas sensor to detect SO 2 rather than resistance type gas sensor. [ABSTRACT FROM AUTHOR]

The gas sensing properties of (8,0) SWCNT on which a Co atom substitutes one carbon atom towards four types of SF 6 decomposed components (SO 2 ，SOF 2 ，SO 2 F 2 ，H 2 S) are investigated using density functional theory calculations. The adsorption structures, adsorption energies, charge transfers, magnetic moments, valence electron occupations, band structures and density of states (DOS) have been discussed. The results are as follows: (1) All adsorptions are exothermic processes with little structural deformation of SO 2 and H 2 S gas molecule while comparatively obvious bond ruptures are taken place towards SOF 2 and SO 2 F 2 . Co-SWCNT loses electrons when interacting with SO 2 , SOF 2 or SO 2 F 2 but serves as an electron acceptor to H 2 S. (2) The adsorption of SO 2 or SOF 2 introduces a great degree of magnetism transfer from Co-SWCNT to gas molecule while the magnetism is still mainly concentrated in Co-SWCNT after SO 2 F 2 or H 2 S adsorption. (3) Valence electron occupation changes at different levels with different gas molecule adsorption and electron transfer between Co’s own orbitals is observed. (4) The adsorptions of four kinds of gas molecule have different influences on band structures and density of states. The introduction of SO 2 , SOF 2 or SO 2 F 2 increases the bandgap in various degrees. The results of DOS are in good accordance with the above results and band structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single Ni atom can stably locate on the S vacancy site of defective WS 2 monolayer. • The adsorption energies of H 2 , C 2 H 2 and CO on WS 2 experience dramatical increase after the doping of Ni. • Ni-WS 2 can be served as sensing material in resistance-type and work function gas sensor to detect dissolved gases in transformer oil. Insulation defects and equipment failure often exist in power transformer, and insulating oil in transformer will experience decomposition with a series reaction. By detecting the dissolved gases in insulating oil, the operation status of transformer can be evaluated. In this study, the adsorption and gas sensing of several kinds of typical dissolved gas molecule (H 2 , C 2 H 2 , and CO) on pristine and single Ni atom doped WS 2 monolayer (Ni-WS 2) was theoretically investigated based on first-principles density functional theory. To discuss the adsorption behavior, the structures, adsorption energies, and electron transfers were calculated and compared. As to the electronic properties and chemical interactions between gas molecule and Ni-WS 2 , the band structures, density of states (DOS), and work functions were studied. The results show that, after the doping of Ni, the adsorption energies of H 2 , C 2 H 2 and CO on WS 2 monolayer increase dramatically, from −0.06 eV to −0.52 eV, −0.23 eV to −1.44 eV, and −0.15 eV to −1.68 eV, respectively. On Ni-WS 2 , H 2 and C 2 H 2 lose electrons while CO shows little electron transfer. Only the adsorption of C 2 H 2 obviously reduces the band gap of Ni-WS 2. For all three kinds of gas adsorption, hybridization of states between Ni 3d and atomic orbitals in molecule can be observed in DOS, indicating considerable chemical interactions. In addition, the adsorption of CO increases the work function of Ni-WS 2 from 5.56 eV to 5.80 eV. Based on the change of different physical and chemical properties, the Ni-WS 2 as sensing material in different gas sensors was evaluated and the desorption time was compared in order to shed light on the experimental realization to detect dissolved gas molecule in insulating oil with high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

The man-made gas sulfur hexafluoride (SF 6) is an excellent and stable insulating medium. However, some insulation defects can cause SF 6 to decompose, threatening the safe operation of power grids. Based on this, it is of great significance to find and effectively control the decomposition products of SF 6 in time. Gas sensors have proven to be an effective way to detect these decomposition gases (SO 2 , SOF 2 , SO 2 F 2 , H 2 S, and HF). Nanomaterials with gas-sensitive properties are at the heart of gas sensors. In recent years, data-driven machine learning (ML) has been widely used to predict material properties and discover new materials. However, it has become a major challenge to establish a common model between material properties derived from various types of calculations and intelligent algorithms. In order to make some progress in addressing this challenge. In this work, 250 data sets were extracted from 52 publications exploring the detection of SF 6 decomposition products by nanocomposites based on relevant work over the past 10 years, and the adsorption behavior of SF 6 decomposition products can be predictively analyzed. By comparing six different algorithmic models, the best model for predicting the adsorption distance (XGBoost: R2 = 91.94 %) and adsorption energy (GBR: R2 = 78.63 %) of SF 6 decomposed gas was identified. Subsequently, the importance of each of the selected feature descriptors in predicting the gas adsorption effect was explained. This work combines first-principles computational results and machine-learning algorithms with each other to provide a new research idea for evaluating the gas sensing capability of nanocomposites. [Display omitted] ● A series of machine learning descriptors are proposed. ● Breaking the tradition and combining first principles calculation with ML. ● Descriptors of the adsorption of SF 6 decomposition products are revealed. ● This work provides a new approach to gas adsorption research. [ABSTRACT FROM AUTHOR]

This study explores the diffusion behavior of one Pt atom on graphene as well as the interaction mechanism between two types of gas molecule (SO2 and H2S) and Pt-graphene based on density functional theory (DFT) considering a dispersion correction about van der Walls force. Results suggest that one Pt atom shows high mobility with low activation energy and Pt doped graphene exhibits relatively stronger interaction with H2S than SO2 according to adsorption energy. SO2 accepts electrons from Pt-graphene while H2S losses electrons. Both two molecules introduce obvious hybridization with Pt-graphene in density of states. The charge density difference and Electron Localization Function (ELF) configurations indicate evident changes in the distribution of electrons about Pt-graphene and gas molecule before and after gas adsorption. H2S is easy to dissociate on Pt-graphene due to the much lower energy barrier compared to SO2. The work provides quantum chemistry methods to investigate the chemical interaction between Pt decorated graphene and two typical gases to shed light on practical application of Pt-graphene in adsorbing and detecting these two kinds of gases or other types of gases. [ABSTRACT FROM AUTHOR]

We explored the adsorption of SO2, SOF2, and SO2F2 on Pt- or Au-doped MoS2 monolayer based on density functional theory. The adsorption energy, adsorption distance, charge transfer as well as density of states were discussed. SO2 and SOF2 exhibit strong chemical interactions with Pt-doped MoS2 based on large adsorption energy, charge transfer, and changes of electron orbitals in gas molecule. SO2 also shows obvious chemisorption on Au-doped MoS2 with apparent magnetism transfer from Au to gas molecules. The adsorption of SO2F2 on Pt-MoS2 and SOF2 on Au-MoS2 exhibits weaker chemical interactions and SO2F2 losses electrons when adsorbed on Pt-MoS2 which is different from other gas adsorption. The adsorption of SO2F2 on Au-MoS2 represents no obvious chemical interaction but physisorption. The gas-sensing properties are also evaluated based on DFT results. This work could provide prospects and application value for typical noble metal-doped MoS2 as gas-sensing materials. [ABSTRACT FROM AUTHOR]

Sulfur dioxide, carbon disulfide, and hydrogen sulfide are important decomposition products of insulating gas sulfur hexafluoride, and their types and contents are of great significance for the fault diagnosis of SF6 insulated equipment. In this paper, a method of combining ultraviolet absorption spectroscopy and least squares fitting is proposed for the quantitative calculation of sulfur dioxide, carbon disulfide, and hydrogen sulfide mixed gases. All three gases have absorption peaks in the ultraviolet band and they overlap with each other which makes it hard to determinate the concentrations of the three gases directly. During the experiment, we found that high concentrations of sulfur dioxide and carbon disulfide interfered with the hydrogen sulfide calculation and the magnitude of this interference was positively correlated with these two gas concentrations. Therefore, we found a modified equation for the correction of hydrogen sulfide. Combined with this equation, accurate quantitative detection of three gases can be achieved. The detection ranges are 0.5–10 parts per million for sulfur dioxide and hydrogen sulfide, and 10–300 parts per billion for carbon disulfide. This paper provides a simple and efficient detection method, which is convenient for integration into detection equipment and it provides a support method for the diagnosis of sulfur hexafluoride decomposition gases. [ABSTRACT FROM AUTHOR]

As the insulating medium, SF6 is widely used in gas insulation equipment. Partial discharge and local overheating can cause the decomposition of SF6, resulting in a decrease in insulation strength of the equipment. The detection of SF6 decomposition gas can be used for on-line insulation detection of gas insulation equipment in electric power industry. In order to develop a new sensor gas sensing material for gas detecting. In this work, based on the first-principles density functional calculation (DFT) method of DMol3, the adsorption of SF6 decomposition gas on (5,0) Z-type Rh-BNNT in different ways was explored. The adsorption energy, adsorption distance, charge transfer as well as density of states were discussed. The results show that the adsorption strength between SO2 molecule with Rh-BNNT is larger than with SOF2 molecule, combined with desorption time, theoretically predicts Rh -BNNT have the potential to be a material for SO2 gas sensors. [ABSTRACT FROM AUTHOR]

In this paper, the sensing property of Ni-BNNT to SO2, SOF2 and SO2F2 were investigated based on the DFT method to explore its potential as a chemical gas sensor. Our results show that Ni-doping could significant deform the electronic behavior of the BNNT, reducing its bandgap largely, from 3.712 eV to 0.601 eV. Ni-BNNT behaves strong chemisorption upon SO2 molecule with adsorption energy of -0.864 eV, while weak physisorption upon SOF2 and SO2F2 molecules with adsorption energy of -0.522 and -0.223 eV. The DOS analysis suggests the strong electron hybridization in SO2 system, while weak orbital interaction in the SOF2 and SO2F2 systems. Upon SO2, the Ni-BNNT could be a promising sensors for sensitive detection while it is unsuitable for detecting SOF2 or SO2F2 due to the weak interaction and extremely short recovery time. This work provides a first insight into the application of Ni-BNNT for detecting SF6 decomposed components, which would be beneficial for effectively evaluating the operation status of SF6 insulated devices. [ABSTRACT FROM AUTHOR]

Based on the first principle, the adsorption and decomposition process of SF 6 gas molecules on the surface of BaTiO 3 (0 0 1) was calculated. The results show that there is a strong interaction between SF 6 molecule and BaTiO 3 surface, and the adsorption energy reached 4.453–4.963 eV, which is likely to be a chemical adsorption process. According to Mulliken analysis, about 1.6 e of electrons transferred from BaTiO 3 surface to the SF 6 gas molecule, the SF 6 molecule behaved as an electron acceptor. According to density of states calculation results, there were obvious electron orbital interactions between SF 6 and BaTiO 3 surface atoms, especially F and O atoms, and the charge transfer process was also confirmed by the differential charge density results. The SF 6 molecules interacted strongly with the BaTiO 3 surface, which led to the elongation of S F bonds and made SF 6 tend to undergo a decomposition process. The results indicate that BaTiO 3 may have a catalytic potential for SF 6 abatement and provide a simulation support for the experimental study of efficient and harmless treatment of SF 6 gas. • The interaction mechanism of the SF 6 on the BaTiO 3 (0 0 1) surface is studied. • SF 6 and BaTiO 3 (0 0 1) have obvious charge transfer processes and electron orbital overlaps. • The S F bonds of SF 6 are elongated due to chemical adsorption on BaTiO 3 (0 0 1). [ABSTRACT FROM AUTHOR]

Highlights • PtPd co-doped CNT is proposed to study the sensing mechanism upon SOF 2 and SO 2 F 2. • Pt 2 Pd 2 clustering effect on CNT and its behavior on gas adsorption are analyzed. • Frontier molecular orbital theory is employed to analyze the conductivity response of Pt n Pd n -CNT (n = 1–2) upon two gases. Abstract Pt or Pd decorated CNTs have received considerable attention in recent years as gas adsorbent and sensors due to their strong catalytic property towards gas interaction. In this work, we theoretical simulated the adsorption process of SF 6 decomposed species, namely SOF 2 and SO 2 F 2 onto Pt and Pd co-decorated CNT (PtPd-CNT) based on density functional theory (DFT) method, in order to propose novel kind of sensing material applied in the field of electrical engineering. To further elucidate the co-decoration effect of Pt and Pd atoms on the adsorption performance of CNT upon two gases, a cluster of Pt 2 Pd 2 is applied to decorate the CNT surface with gas adsorption process simulated as well. Results indicated that such material has better sensitivity upon SOF 2 than SO 2 F 2 , given the stronger adsorption behavior and larger change in conductivity after adsorption, showing its potential to be exploited as gas sensors for detection of the former gaseous substance. Our calculation would be meaningful to suggest novel material realizing the operation state evaluation of SF 6 devices. [ABSTRACT FROM AUTHOR]

Highlights • Carbonyl oxygen atom in C5-PFK has strong reactivity with aluminum and silver. • Interaction between C5-PFK and Ag (1 1 1) surface is weaker than that of Al (1 1 1). • The metal acts as electron donor and the gas molecule gain electrons. • The use of silver is more reliable than aluminum for GIS with C5-PFK mixture. Abstract The ketone C 5 F 10 O (C5-PFK) has been considered as substitute for SF 6 in the past two years. And there are few reports on the interaction between C5-PFK and materials used in electrical equipment, which may have an influence on its long term behavior. In this paper, we explored the interaction between C5-PFK molecule and aluminum, silver based on the density functional theory (DFT). The adsorption energy, charge transfer, adsorption distance, density of states (DOS), electron localization function (ELF) and electron density difference were calculated and analyzed. It was found that the interaction between C5-PFK and Al (1 1 1) is stronger than that of Ag (1 1 1), which belongs to chemical adsorption according to the electronic properties results. And the interaction mechanism between C5-PFK and Ag (1 1 1) belongs to physical interaction. The van der Waals force plays a major role. Thus the use of silver is more reliable than aluminum for gas insulated switchgear with C5-FPK gas mixture. [ABSTRACT FROM AUTHOR]

Metal-N x embedded CNT have aroused considerable attention in the field of gas interaction due to their strong catalytic behavior, which provides prospective scopes for gas adsorption and sensing. Detecting SF 6 decomposed species in certain devices is essential to guarantee their safe operation. In this work, we performed DFT method and simulated the adsorption of three SF 6 decomposed gases (SO 2 , SOF 2 and SO 2 F 2 ) onto the PtN 3 embedded CNT surface, in order to shed light on its adsorption ability and sensing mechanism. Results suggest that the CNT embedded with PtN 3 center has strong interaction with these gas molecules, leading to high hybridization between Pt dopant and active atoms inner gas molecules. These interactions are assumed to be chemisorption due to the remarkable E ad and Q T , thus resulting in dramatic deformations in electronic structure of PtN 3 -CNT near the Fermi level. Furthermore, the electronic redistribution cause the conductivity increase of proposed material in three systems, based on frontier molecular orbital theory. Our calculations attempt to suggest novel sensing material that are potentially employed in detection of SF 6 decomposed components. [ABSTRACT FROM AUTHOR]

Pt-clustered CNTs have been considered to be superior gas sensors due to their enhanced catalytic property towards gas interaction. Cluster size which would affect the catalytic property, geometric and electronic structure of metal cluster is an important factor determining the adsorption performance of the whole system. In this work, we performed theoretical calculations about Pt n (n = 1–4) cluster adsorption onto CNT (Pt n -CNT), to comprehensively understand the Pt clustering effect on CNT. Additionally, adsorption of SOF 2 molecule on the Pt n -CNT surface was studied as well, in order to give fundamentally adsorption and sensing principle of this gaseous species. Results shows decoration of Pt n with n larger than 1 on the sidewall of CNT would make the tube metallic, redistributing the electron and improving the conductivity dramatically. Simultaneously, the adsorption behavior of Pt 3 -CNT towards SOF 2 is the strongest among four Pt n -CNT systems, implying its good suitability for remove such gaseous substance in SF 6 devices. Our calculation not only provided a prior insight upon the generation of Pt n -CNT from the molecular level in a theoretical manner when depositing Pt metal onto CNT surface, but also shed light on potential application for the prepared material. [ABSTRACT FROM AUTHOR]

CF 4 and COF 2 are the two main decomposition products of fluorocarbon gas insulating medium. We explored the gas sensing properties of Ni-MoS 2 to CF 4 and COF 2 based on the density functional theory calculations. The adsorption energy, charge transfer, density of states and electron density difference have been discussed. It was found that the interaction between COF 2 molecule and Ni-MoS 2 is strong, and the adsorption energy is 0.723 eV. Ni-MoS 2 acts as the electron donor and transfers some electrons to COF 2 molecule during the interaction. The adsorption energy of CF 4 on Ni-MoS 2 is lower than that of COF 2 , and the interaction between them belongs to physical adsorption. Ni-MoS 2 has the potential to be used as a gas sensor for COF 2 detection using in the field of gas insulated switchgear on-line monitoring. [ABSTRACT FROM AUTHOR]

SF 6 is extensively used in electrical applications because of its excellent insulation and arc extinguishing performance, but its strong greenhouse effect has negative impact on the atmosphere. The excellent performance of C 3 F 7 CN in greenhouse effect, insulation ability, safety, and thermal stability has been demonstrated, indicating that this compound can replace SF 6 in electrical applications. However, little information is available on the compatibility of C 3 F 7 CN with metals, such as copper and aluminum, in devices. Material compatibility between new gas mixtures and materials used in Gas Insulated Switchgear (GIS) should be investigated to determine the long-term behavior of materials. In this paper, dissociative adsorption of C 3 F 7 CN on Cu (1 1 1) and Al (1 1 1) surfaces were analyzed based on density functional theory. Adsorption energy, charge transfer, density of states, and electron density difference of interaction between C 3 F 7 CN and two metals were analyzed. It was found that the adsorption energy of C 3 F 7 CN adsorbed on Cu (1 1 1) and Al (1 1 1) is both below 0.8 eV. This value indicates that the interaction between them is not very strong. In addition, the dissociation reaction path of gas molecules after adsorption requires certain activation energy. Therefore, C 3 F 7 CN and copper or aluminum have certain compatibility and the compatibility of C 3 F 7 CN with aluminum is better than that of copper. Related results provide a reference for predicting the aging mechanism of equipment and the selection or modification of major materials for equipment. [ABSTRACT FROM AUTHOR]

Carbon nanotubes decorated by transition metals have accepted considerable attention because of their improved physicochemical properties. In this paper, the geometric and electronic structure of Pt 3 clustered (8, 0) semiconducting SWCNT was researched in order to obtain the most stable configuration for Pt 3 -CNT and related electron distribution. Simultaneously, the adsorption performance of proposed complex toward H 2 S molecules were studied as well, for the purpose of comprehending the combined effect of catalytic behavior for Pt clusters and adsorbing ability for CNT. All the results are obtained in the basis of density functional theory. The calculated results indicated that the dopant of Pt 3 cluster can effectively enhance the conductivity of carbon nano-support and electron affinity. In the meanwhile, Pt 3 -CNT that has good sorption upon H 2 S molecules is a promising sensing material to be exploited as gas sensors for detecting the presence of hydrothion. Our calculations are meaningful not only lies in illustrating the catalytic nature of Pt doped CNT, but also suggesting favorable material to design device employed for gas detection. [ABSTRACT FROM AUTHOR]

In the electrical industry, there are many hazardous gases that pollute the environment and even jeopardize human health, so timely detection and effective control of these hazardous gases is of great significance. In this work, the gas-sensitive properties of Pd-modified g-C 3 N 4 interface for each hazardous gas molecule were investigated from a microscopic viewpoint, taking the hazardous gases (CO, NO x) that may be generated in the power industry as the detection target. Then, the performance of Pd-modifiedg-C 3 N 4 was evaluated for practical applications as a gas sensor material. Novelly, an unconventional means was designed to briefly predict the effect of humidity on the adsorption properties of this sensor material. The final results found that Pd-modified g-C 3 N 4 is most suitable as a potential gas-sensitizing material for NO 2 gas sensors, followed by CO. Interestingly, Pd-modified g-C 3 N 4 is less suitable as a potential gas-sensitizing material for NO gas sensors, but has the potential to be used as a NO cleaner (adsorbent). Unconventional simulation explorations of humidity effects show that in practical applications Pd-modified g-C 3 N 4 remains a promising material for gas sensing in specific humidity environments. This work reveals the origin of the excellent properties of Pd-modified g-C 3 N 4 as a gas sensor material and provides new ideas for the detection and treatment of these three hazardous gases. [Display omitted] • The sensing properties of Pd-modified g-C 3 N 4 interface were evaluated for CO, NO x. • A new experiment for the prediction of humidity-influenced interface performance was designed. • This work enriches new schemes for the preparation of g–C 3 N 4 –based gas sensors. • This work provides new ideas for addressing hazardous gases generated in the electrical industry. [ABSTRACT FROM AUTHOR]

Insulation performance testing of gas-insulated switchgear (GIS) and treatment of SF 6 decomposition products under partial discharge are two crucial studies. In this paper, the adsorption behavior and sensor properties of five characteristic decomposition gases of SF 6 (HF, H 2 S, SO 2 , SOF 2 , SO 2 F 2) on intrinsic and CoO-doped SnSe monolayers are investigated in detail based on density-functional theory. The results showed that the adsorption behaviors of HF, H 2 S, SOF 2 and SO 2 F 2 on SnSe monolayers were all physisorption among which the best adsorption was SO 2 with an adsorption energy of −0.618 eV, which is a weak chemisorption. After doping with CoO, the adsorption capacity of SnSe monolayer for five gases was significantly enhanced, in which the adsorption energies for SO 2 and SOF 2 reached −1.356 eV and −1.175 eV, respectively. In addition, the conductivity of the system is greatly improved, with the bandgap changing from 1.129 eV to 0 eV. The microscopic mechanism of the interaction of gas molecules with CoO-SnSe monolayers has been revealed by energy band structure (E g), density of states (DOS), Milligan charge analysis (∆ Q) and electrostatic potential. Finally, the sensitivity (S) and desorption time (τ) of the five adsorption systems were calculated to illustrate the macroscopic gas-sensitive properties of the system. This work will help to explore the application of CoO-SnSe monolayers in SF 6 decomposition gas sensing detection and adsorption treatment. [Display omitted] • Doping greatly improves the conductivity of the system, and the adsorption effect of doped system on SO 2 and SOF 2 is significantly improved. • The change of electronic characteristics of doped system is expounded. • The sensing characteristics of adsorption system are calculated, and the possibility of SOF 2 as the target gas for CoO-SnSe sensing device to evaluate GIS insulation performance is explored. [ABSTRACT FROM AUTHOR]

It is challenging to extract satisfactory building outlines from LiDAR data due to the unorganized point cloud and complex building shapes. To solve the issues, a method using adaptive tracing alpha shapes (ATAS) and contextual topological optimization is proposed. First, the ATAS method is used to extract sequential boundary points. After that, a method based on point cloud distribution analysis is developed to obtain building dominant directions and line segments of outlines. Finally, regularized outlines are obtained by adjusting all line segments simultaneously under the framework of global energy optimization that considers the geometric errors and contextual geometric relationships between adjacent line segments. Experimental results verify that the proposed ATAS method can efficiently extract sequential boundary points with a minimum 98.49% correctness. In addition, the extracted outlines are attractive and the minimum values of the RMSE , PoLiS, and RCC metrics of the extracted outlines are 0.48 m, 0.44 m, and 0.31 m, respectively, showing the effectiveness of the proposed method. • Adaptive tracing alpha shapes method (ATAS) is proposed to efficiently extract sequential boundary points directly from unorganized building point clouds with complex shapes, without pre-processing (e.g., triangulation, gridding). • A method based on point cloud distribution analysis is proposed to detect accurate and reliable building dominant directions, which is beneficial to subsequent outline extraction. • The proposed method can extract smooth and attractive outlines from complex buildings by formulating outline regularization as an optimal labeling problem under the framework of global energy optimization, which balances geometric errors of boundary points and contextual geometric relationships between adjacent line segments. [ABSTRACT FROM AUTHOR]

To realize a high response and high selectivity gas sensor for the detection dissolved gases in transformer oil, in this study, the adsorption of four kinds of gases (H2, CO, C2H2, and CH4) on Pd-graphyne was investigated, and the gas sensing properties were evaluated. The energetically-favorable structure of Pd-Doped γ-graphyne was first studied, including through a comparison of different adsorption sites and a discussion of the electronic properties. Then, the adsorption of these four molecules on Pd-graphyne was explored. The adsorption structure, adsorption energy, electron transfer, electron density distribution, band structure, and density of states were calculated and analyzed. The results show that Pd prefers to be adsorbed on the middle of three C≡C bonds, and that the band gap of γ-graphyne becomes smaller after adsorption. The CO adsorption exhibits the largest adsorption energy and electron transfer, and effects an obvious change to the structure and electronic properties to Pd-graphyne. Because of the conductance decrease after adsorption of CO and the acceptable recovery time at high temperatures, Pd-graphyne is a promising gas sensing material with which to detect CO with high selectivity. This work offers theoretical support for the design of a nanomaterial-based gas sensor using a novel structure for industrial applications. [ABSTRACT FROM AUTHOR]

C6F12O (heptafluoroisopropyl pentafluoroethyl ketone) has been considered as a potential eco-friendly gas insulating medium to replace SF6, the most potent greenhouse gas, used in medium-voltage equipment. In this paper, we explored the compatibility between the C6F12O-air gas mixture and metals such as copper and aluminum to evaluate the long-term behavior of the new gas. Aging tests for the C6F12O-air gas mixture and metal were conducted, and the composition as well as the microstructure was analyzed. It was found that the interaction between C6F12O-air and copper results in the decomposition of C6F12O and corrosion of copper. Several by-products including CO2, C3F6, C4F8O, and C6F12 can be detected. Obvious color modifications and corrosion points exist after interaction. The compatibility between C6F12O-air and aluminum is superior to that between C6F12O-air and copper. Their interaction did not lead to the corrosion of aluminum. As for engineering applications, anticorrosion measures should be taken on copper to avoid the occurrence of negative chemical interactions. [ABSTRACT FROM AUTHOR]

Using first-principles theory, we theoretically investigate the most stable doping site of Ni atom on pristine InN monolayer and adsorption behavior of Ni-doped InN (Ni-InN) monolayer upon four noxious gases (NO, CO 2 , H 2 S and NH 3). Electron localization function (ELF), electron deformation density (EDD) as well as density of state (DOS) are considered to further understand the adsorption behavior of Ni-InN monolayer towards gas molecules. For possible application of our proposed material, work function and band structure of the isolated and gas adsorbed Ni-InN monolayer are analyzed as well. It is found that the Ni dopant prefers to be adsorbed on the pristine InN monolayer at the T N site with the lowest biding force (E b) of −3.02 eV. Four gases could be stably adsorbed on the Ni-InN monolayer surface wherein the chemisorption is identified due to the large adsorption energy (E ad) and charge transfer (Q T). ELF, EDD and DOS analyses corroborate the strong chemical interaction between Ni dopant and activated atoms in gas molecules. The band structure analysis provides the sensing mechanism of Ni-InN based resistance-type chemical sensor for detection of such four gaseous species. Our calculations can supply some guidance to explore promising novel gas sensors using group III-V nitrides in the gas-sensing field and environmental monitoring fields. Unlabelled Image • The Ni-doping behavior on InN monolayer is elucidated to enrich the principle of TM-InN. • Adsorption and sensing behaviors of Ni- InN monolayer upon common pollutant gases were analyzed. • Our calculation can accelerate development of chemical sensors in environment monitoring and industrial manufacturing. [ABSTRACT FROM AUTHOR]

Based on the first principle, the interaction process between SF6 molecule and α-Al2O3 (0 0 0 1) surface was calculated. The results show that, under five adsorption sites, SF6 can form a relatively stable chemical adsorption at the O-3 site on α-Al2O3 (0 0 0 1) surface, while the other sites mainly showed physical adsorption processes. At O-3 site, 0.664 e electrons were transferred from α-Al2O3 to the SF6 molecule, and DOS analysis indicates that there was a strong electron orbital interaction between S and F atoms in SF6 and Al and O atoms on α-Al2O3 surface. After the adsorption, the molecule structure of SF6 changed significantly, the S–F bonds were elongated and partially broken, and the whole SF6 showed a tendency to be close to the surface of α-Al2O3. The energy barrier for SF6 decomposition was 0.147 eV. The results show the adsorption and decomposition process of SF6 molecules on the surface of α-Al2O3, which proves that α-Al2O3 has certain catalytic properties. The results indicate a simulation support for the efficient and harmless treatment of SF6 gas with Al2O3 catalysts. [ABSTRACT FROM AUTHOR]

• C 4 F 7 N-N 2 gas mixture has great compatibility with heated aluminum. • Interaction between C 4 F 7 N-N 2 and copper cause gas decomposition and metal corrosion. • Accumulation of F, CF x and CN particles on the metal surface can be found. • Anti-corrosion treatment should be applied on the copper before application. The thermal interaction mechanism between C 4 F 7 N (fluorinated nitrile)-N 2 gas mixture using as substitute to SF 6 with metal was investigated. We found that interaction between C 4 F 7 N-N 2 and copper leads to surface corrosion or gas decomposition with interface temperature at 120℃-220℃. The oxidation of copper and accumulation of F, CF x and CN can be found and gaseous by-products such as C 3 F 6 , CF 3 H, C 3 F 6 O is produced. C 4 F 7 N-N 2 has better compatibility with aluminum than that of copper due to the existence of alumina. The interaction between C 4 F 7 N and alumina surface has the lowest adsorption energy, charge transfer compared with that of copper and aluminum. [ABSTRACT FROM AUTHOR]

Highlights • The LC50 (rat, 4 h) of C 4 F 7 N was higher than 15,000 ppm and lower than 20,000 ppm. • C 4 F 7 N caused certain damage to lung, kidney, intestine and brain tissues of rat. • Researchers are recommended to take adequate protection for C 4 F 7 N. Abstract C 4 F 7 N (fluorinated nitrile) gas mixture has been utilized as the gas insulating medium to replace the most greenhouse gas SF 6 (sulphur hexafluoride). Nowadays, there are few reports on the toxicity mechanism of C 4 F 7 N and studies on the application risk of C 4 F 7 N is insufficient. In this paper, we carried out acute toxicity tests for C 4 F 7 N gas systematically. The changes of vital signs of rats after exposure to C 4 F 7 N were analyzed and the influence of C 4 F 7 N on the main organs of rats was revealed for the first time. It was found that rats developed symptoms of respiratory rate decrease, respiratory mucosa damage, movement systems impairment and abnormal blood cell count after exposure to C 4 F 7 N. Pathological section results showed that 1.5% C 4 F 7 N could damage the lung, kidney, intestine and brain tissues of rats to a certain extent, but has little influence to the eye, skin, heart and liver. The LC50 (rat, 4 h) of C 4 F 7 N gas is in the range of 15,000 ppm (1.5%) and 20,000 ppm (2%). Relevant research results not only reveal the acute toxicity mechanism of C 4 F 7 N, but also provide important reference for the safety protection of scientific researcher, equipment production, engineering operation and maintenance personnel. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Decomposition of C 6 F 12 O-CO 2 mainly produces CF 4 , C 2 F 6 , C 3 F 8 , C 3 F 6 and C 5 F 12. • The main decomposition particles produced are CF 3 , CF 2 , CF, C 3 F 7 , CO, COF 2 , C 5 F 9 O and F. • C 3 F 7 COCF 2 and C 3 F 7 COCF 2 are the main intermediates produced by C 6 F 12 O. • Results provide guidance for clarifying decomposition characteristics of C 6 F 12 O/CO 2. Abstract C 6 F 12 O (1,1,1,2,2,4,5,5,5-Nonafluoro-4-(trifluoromethyl)-3-pentanone) is an environmental friendly gas insulating medium with the potential to replace the strong greenhouse gas SF 6 for medium and low pressure gas insulated equipment. In this paper, the decomposition mechanism of C 6 F 12 O-CO 2 gas mixture under different temperature and pressure conditions were explored based on the ReaxFF molecular dynamics. The thermal decomposition characteristics of C 6 F 12 O-CO 2 gas mixture were also tested. We found that the main decomposition particles of C 6 F 12 O-CO 2 gas mixture incudes CF 3 , CF 2 , CF, C 3 F 7 , CO, COF 2 , C 5 F 9 O and F, and the content of CF 3 , CF 2 , CF, C 3 F 7 , CO and F is high. The thermal decomposition of C 6 F 12 O-CO 2 gas mixture mainly produces CF 4 , C 2 F 6 , C 3 F 8 , C 3 F 6 and C 5 F 12 , among which the content of C 2 F 6 and C 3 F 6 are the highest, followed by C 3 F 8 and the content of CF 4 is the lowest. Relevant results not only reveal the decomposition mechanism of C 6 F 12 O-CO 2 gas mixture comprehensively, but also provide an important reference for exploring the decomposition characteristics and engineering applications of C 6 F 12 O-CO 2 gas mixture. [ABSTRACT FROM AUTHOR]

Abstract Fluorinated nitrile (C 4 F 7 N) has received much attention as substitute gas for sulfur hexafluoride (SF 6) using in electrical equipment over the past two years. In this paper, we explored the compatibility between C 4 F 7 N and silver theoretically and experimentally. The interaction mechanism between C 4 F 7 N and silver was investigated based on the density functional theory (DFT) and the composition characteristics of C 4 F 7 N and silver after long term interaction were also revealed. It was found that the most energetically favorable adsorption structure has the adsorption energy of 0.69 eV with 0.024e charge transfer. Electron localization function (ELF) also shows evidently electron delocalization region between C 4 F 7 N and Ag (1 1 1). Thus the interaction mechanism belongs to physisorption and the van der Waals force plays a major role. The gas composition of C 4 F 7 N, the morphology and crystal structure of silver did not have any obvious change after 70 days' interaction, which indicates the compatibility between C 4 F 7 N and silver is great. Graphical abstract Image 1 Highlights • Composition of C 4 F 7 N and silver did not have any change after 70 days' interaction. • ELF shows evidently electron delocalization region between C 4 F 7 N and Ag (1 1 1). • Interaction between C 4 F 7 N and silver belongs to physisorption. • The use of silver is reliable for C 4 F 7 N gas insulated equipment. [ABSTRACT FROM AUTHOR]

SF6 as a greenhouse gas, how to efficiently decompose it becomes a hotpot in the environmental field. Based on the first-principles calculations, this paper studied the interaction mechanism of SF6 gas molecules on transition metal (TM) doped MoS2 surface. The adsorption energy, energy barrier, charge transfer, density of states and electron density difference have been discussed. The results show that TM doping can enhance the interaction of MoS2 surface with SF6 molecules compared to undoped MoS2. Among the four (Au, Pt, Ag, Ni) doping conditions, the adsorption energies of SF6 molecules in the Au-MoS2 and Pt-MoS2 systems were 0.306 eV and 0.249 eV, the charge transfer process was weak, and the SF6 molecule did not change significantly. In the Ag-MoS2 and Ni-MoS2 systems, the adsorption energies reached 0.464 eV and 0.473 eV, and the DOS and differential charge analysis show that there were strong charge transfer process and electron orbital interaction between SF6 and MoS2. The decomposition energy barriers of SF6 on Ag-MoS2 and Ni-MoS2 surface were 0.696 eV and 0.432 eV, respectively. The S-F bonds were obviously elongated. The results show that Ag-MoS2 and Ni-MoS2 have catalytic potentials for the decomposition of SF6. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) method was employed in this work to theoretically study the adsorption behavior of borophene towards SO2 molecules. The adsorption systems for one molecule and up to eight molecules were conducted to comprehensively understand adsorption ability and capacity of borophene upon SO2. The density of state (DOS) was also analyzed to help understand the electronic behavior of adsorption processes. Results indicate that the borophene has good adsorption ability and capacity towards SO2 molecule that up to seven molecules could be adsorbed on its surface by chemisorption according to the relaxed adsorption configuration combined with large values of Ead and QT in this system. Our calculations would be meaningful for exploitation of such material being applied as SO2 adsorbent in the near future. [ABSTRACT FROM AUTHOR]

Seeking environmentally friendly gas-insulated medium has become a research hotspot in recent years. At present, C3F7CN (Heptafluoro-iso-butyronitrile) is considered to be a potential SF6 environment-friendly alternative gas and some achievements have been made in the study of its insulation and decomposition characteristics, but there are few reports on the compatibility between its characteristic decomposition products and materials. The investigation of compatibility between gas-insulated medium and material is an important part of evaluating its comprehensive performance. In this paper, we investigated the interaction between C2F5CN, CF3CN, COF2 and CF4 with the aluminium widely used in electrical equipment. It was found that the interaction between C2F5CN, CF3CN and Al (1 1 1) surface is strong. There are obvious charge transfer and electron orbital overlap between the C atom, N atom in CN group and Al (1 1 1). The interaction between COF2, CF4 and Al (1 1 1) surface is weak and van der Waal’s forces play the major role. Relevant results reveal the characteristics of C3F7CN decomposition products and provide theoretical guidance for evaluating the material compatibility between C3F7CN decomposition products and aluminium. [ABSTRACT FROM AUTHOR]

As a kind of gas insulation medium, SF 6 is widely used in the power industry. Due to its high global warming potential value, the degradation and recycle of SF 6 has become a research hotspot in recent years. At present, there have been some achievements in the experimental study on the degradation of SF 6 , but there is little research on the catalytic degradation of SF 6 by metal catalysts. Based on the first-principle, this paper investigated the interaction between SF 6 and Ag(1 1 1) and evaluated the possibility of using Ag as a catalyst in SF 6 degradation. It is found that SF 6 can interact with Ag(1 1 1) surface with eight initial configurations. After the interaction, the distance between the F atom in the SF 6 molecule and the Ag surface is significantly shortened and the S F bond is elongated. There is a strong charge exchange process between the Ag metal interfaces and SF 6 molecule. Ag (1 1 1) transfers electrons of about 1.1e− to the SF 6 molecule and the dissociation of SF 6 by Ag metal shows a catalytic effect. The related research results provide a theoretical reference for the silver-catalyzed degradation of SF 6 . [ABSTRACT FROM AUTHOR]

C 4 F 7 N is under wide consideration as an environment-friendly gas insulating medium to replace the strong greenhouse gas SF 6 using in medium-voltage and high-voltage gas insulated equipment. At present, there are few reports on the compatibility between C 4 F 7 N characteristic decomposition products and materials used in the equipment. Investigations about the material compatibility between new gas and materials used in equipment are required to decide about a long term behavior. In this paper, we studied the interaction between characteristic decomposition products of C 4 F 7 N and copper, silver based on the density functional theory. The adsorption energy, charge transfer and density of states of C 2 F 5 CN, CF 3 CN, COF 2 , CF 4 gas molecules adsorbed on Cu (1 1 1) and Ag (1 1 1) surfaces were obtained. It was found that the interaction between C 2 F 5 CN, CF 3 CN and Cu (1 1 1) is stronger than that of COF 2 and CF 4 . But there is no chemical bond formation process occurs between gas molecules and Cu (1 1 1) surface. And the interaction between characteristic decomposition products of C 4 F 7 N with Ag (1 1 1) is weaker than that of Cu (1 1 1). Relevant results not only reveal the interaction between C 4 F 7 N decomposition products and copper, silver, but also provide guidance for the engineering application and long term behavior assessment of C 4 F 7 N gas mixture. [ABSTRACT FROM AUTHOR]

The high-temperature effect gas SF6 is used in the power industry, and its emissions are increasing daily. Therefore, the degradation of SF6 is particularly important. In this work, SF6 with a high concentration of 2% was degraded using the catalytic principle of TiO2 under UV light at normal temperature and pressure. Experimental results proved that this method can effectively degrade SF6. Moreover, the addition of TiO2 can effectively increase the degradation rate of SF6. The degradation of eight pieces of TiO2 with a unit area of 3 cm2 was 8.98% after 3 h of catalysis. FTIR spectral analysis showed that the main degradation products were SO2F2, SiF4, SF4, and SO2. Adding H2O can further increase the degradation rate, which can reach 27.22% in 3 h. The main degradation products were SO2F2, SiF4, SF4, SiH4, HF, and SO2. Finally, simulations verified the catalytic decomposition of SF6 on the surface of TiO2. [ABSTRACT FROM AUTHOR]

C5-PFK has drawn much attention in recent years as an environmental friendly gas-insulated medium. Many studies have proved that it has the potential to replace SF 6 using in medium voltage electrical equipment. However, there are few reports about the compatibility between C5-PFK and materials used in the gas-insulated switchgear. C5-PFK may react with materials such as metal inside the equipment due to the strong activity of carbonyl group (C = O) in its molecular structure. Investigations about the material compatibility between C5-PFK and the materials are required to decide about a long term behavior. In this paper, the interaction between C5-PFK and copper, a common metallic material in electrical equipment, is discussed based on the density functional theory. We found that the interaction between the O atom in the C5-PFK molecule and Cu (1 1 1) surface is strong. The interaction between F atom and Cu (1 1 1) surface is weak, which belongs to physical adsorption. Relevant results not only clarify the compatibility between C5-PFK and copper but also provide guidance for prediction of long-term behavior of C5-PFK gas mixture and the selection or modification of materials used in the equipment. [ABSTRACT FROM AUTHOR]

In recent years, many scholars have been devoted to the search for environmentally friendly gas-insulated medium to gradually replace robust greenhouse gases, such as sulfur hexafluoride (SF 6 ), which are widely used in the power industry at this stage, and thus promote the green development of power industry. In this study, the decomposition characteristics of C5-PFK (C5-perfluoroketone), a potential environmentally friendly alternative gas, were theoretically investigated. First, the bond order and Fukui functions of C5-PFK were calculated based on density functional theory, and the reactivity and stability of C5-PFK were revealed from a molecular viewpoint. Second, the decomposition characteristics of C5-PFK/CO 2 gas mixture were examined through reactive molecular dynamics theory. The decomposition mechanism of C5-PFK/CO 2 gas mixture and the yield and distribution of the main decomposition products at different temperatures and mixing ratios were obtained. Results show that chemical bonds between carbonyl and its linked carbon atoms in C5-PFK molecule are weak but with robust reactivity. C5-PFK/CO 2 gas mixture decomposes mainly above 2600 K, producing CF 3 , CO, C 3 F 7 CO , CF , CF 2 , C 3 F 7 , F , CF 3 , and C , among which the CF 3 and CO contents are the highest. The decomposition characteristics of the gas mixture with a larger content of C5-PFK are inferior to those of the smaller content under the same condition. Relevant research results provide guidance for further clarifying the electrical characteristics, such as self-recovery and arc suppression performance of C5-PFK/CO 2 gas mixtures and engineering applications. [ABSTRACT FROM AUTHOR]

Transition metal decorated carbon nanotubes (CNTs) applied in the field of gas adsorption and storage have in recent years accepted considerable attentions because of their superior adsorbing performance. In electrical engineering, they are employed as adsorbents to remove the decomposed products of SF 6 caused by partial discharge, for guaranteeing the insulation status of gas insulation switchgear (GIS). In this paper, Rh doped SWCNT is introduced to investigate its adsorption properties towards typical gases of SF 6 based on density functional theory (DFT) method. Both single and double molecules adsorbing systems were performed to investigate the adsorption ability of proposed material. Results indicate that Rh-CNT, which has strong interaction with defined gas molecules, is a promising material for SF 6 decompositions adsorption especially SO 2 and SOF 2 that exhibit topmost sensitivity to the modified surface. Therefore, we suggest the Rh-CNT to be an adsorbent to be applied in GIS for guaranteeing the operation state of such devices and even to be exploited as gas sensor to evaluate the insulation state of the power system. Our calculations would provide experimentalist with a first insight into physicochemical properties of this material. [ABSTRACT FROM AUTHOR]

As a novel eco-friendly gas insulation medium, perfluoroisobutyronitrile (C 4 F 7 N) has been utilized in various gas insulated equipment. Considering the biological toxicity of C 4 F 7 N, it is of great engineering significance to develop highly sensitive sensors for leakage detection scenarios. Herein, we fabricated the first SnO 2 nanoparticles based highly sensitive C 4 F 7 N gas sensor that realized a superior response of 65.01% within 21 s for 50 ppm C 4 F 7 N exposure and a detection limit of 0.25 ppm. Meanwhile, successive response-recovery tests were performed to confirm its durability and stability. We also explored the sensing mechanism of SnO 2 nanoparticles towards C 4 F 7 N and explained the superior sensing performance compared with other gases based on the density functional theory. It was found that the O vacancy demonstrates strong interaction with the -CN group in C 4 F 7 N that promotes the detection response, which was also confirmed by sensing experiments for SnO 2 with different O vacancy density. We believe this paper provides convincing support for lowering the potential operation risk brought by C 4 F 7 N in electrical engineering and the application scenarios of SnO 2 based gas sensors. [Display omitted] • The pristine SnO 2 nanoparticles based C 4 F 7 N gas sensor is proposed for the first time. • A response of 28.41% in 64.96 s when exposed to 1 ppm C 4 F 7 N was achieved. • A linear response in the concentration of 2–10 ppm C 4 F 7 N was achieved. • Results provide a convincing support for lowering the potential operation risk brought by C 4 F 7 N. [ABSTRACT FROM AUTHOR]

• Thermal decomposition of C 4 F 7 N-N 2 generated C 3 F 6 firstly at 350℃. • CF 4 and C 3 F 8 were generated at temperatures higher than 450℃. • C 3 F 6 , C 3 F 8 , CF 4 , CF 3 CN, (CN) 2 and COF 2 are the main decomposition products. • Thermal stability of C 4 F 7 N-N 2 gas mixture at high gas pressure conditions is great. We explored the thermal decomposition properties of Fluoronitriles-N 2 (C 4 F 7 N-N 2) gas mixture using as SF 6 substitute gas in GIE. The yield of main decomposition products of 10 %C 4 F 7 N-90 %N 2 gas mixture under different overheating temperature and gas pressure conditions were detected and analyzed. We found that thermal decomposition of C 4 F 7 N-N 2 mainly produces C 3 F 6 , C 3 F 8 , CF 4 , CF 3 CN, (CN) 2 and COF 2. C 3 F 6 is the first detected by-product at 350℃, while CF 4 and C 3 F 8 were generated at temperatures higher than 500℃. The yield and formation rate of C 3 F 6 , (CN) 2 increases with temperatures lower than 450℃ then decreases at higher temperatures, while the generation of C 3 F 8 , CF 4 , CF 3 CN and COF 2 has positive correlation with temperature. C 4 F 7 N-N 2 gas mixture has great thermal stability at high pressure. The increase of gas pressure could effectively reduce the decomposition of C 4 F 7 N, which ensures the insulation strength of gas mixture. [ABSTRACT FROM AUTHOR]