SF6 Decomposition Products Research Articles

SF6 decomposed gas sensing performance of van der Waals layered cobalt oxyhydroxide: insights from a computational study.

The detection of SF6 decomposition products plays a significant part in identifying and assessing the electric discharge faults in SF6 insulation equipment. We performed dispersion corrected density functional theory calculations to study the adsorption performance of CoOOH upon SO2, SF4, SOF2, CF4, and SO2F2 toxic gases, to investigate their potential application as a gas sensor. The results clearly show a weak force between the CoOOH sheet, and the molecular gas with moderate adsorption strength enhances the desorption processes. According to Löwdin charge population analysis, electrons transfer from the molecular gas to the CoOOH surface, where the molecular gas behaves like an electron donor. The lower bandgap energy of the adsorption systems compared with pristine CoOOH significantly increases its electrical conductivity and gas sensing performance. The higher charge transfer and adsorption energy of the SOF2 adsorption system compared with the other four molecular gas is due to orbital hybridization around the Fermi energy. The theoretical computed adsorption energy with ultrahigh sensitivity and fast recovery time suggests that SF6 decomposed gases reusability is achieved with CoOOH as a resistance-type gas sensor.

Sc doped arsenene as adsorbent for the detection and removal of SF6 decomposition gases: A DFT study

Arsenene has two stable allotropes, phosphorene-like puckered structure (α-As) and phosphorene-like buckled structure (β-As), showing potential prospects in gas sensing. In this work, we systematically investigate the pristine and metal-atom-doped arsenene as potential adsorbate candidates of three SF6 decomposition products (SO2, SOF2 and SO2F2) based on first-principles theory. Our results reveal pristine arsenene, α-As and β-As, has poor detecting performance due to the relatively weak interaction toward gas molecules. After introducing transition metal dopants (TM = Sc, Ti, V, Cr, Mn, Fe, Co and Ni) on arsenene, Sc doped systems show the strongest structural stability. Analysis results of adsorption energies and electronic properties indicate that Sc doped α-As monolayer possesses quite strong adsorption behaviors towards SO2 and SOF2, while the similar strong adsorption behaviors are found in Sc doped β-As for the three gases, which makes it possible to develop monolayer arsenene-based adsorbent to remove the polluted gases in SF6 insulation devices. Therefore, our research shows that Sc doped arsenene is a novel potential adsorbate material that can be used to evaluate SF6 insulation devices’ working status.

Gas-sensing properties of Ptn-doped WSe2 to SF6 decomposition products

Two-dimensional transition metal disulfides (TMDs) has attracted considerable attention due to its excellent physicochemical properties. In order to detect the SF6 decomposition products, transition metal Pt cluster doping was chosen to enhance the adsorption property of intrinsic WSe2 monolayer. The adsorption of SO2, SOF2 and SO2F2 on Ptn (n=1–3) doped WSe2 monolayer is studied based on the first-principle calculation. The adsorption energy, charge transfer, and density of states of the interaction between the target gas molecules and Ptn-WSe2 were studied. The calculation results showed that Pt3 doping dramatically enhances the adsorption of WSe2 to SO2 and SOF2 and SO2F2 molecules. Meanwhile, electrons transfer from Ptn-WSe2 surface to these three kinds of target gas molecules, reducing the conductivity of the adsorption system in different degrees. The results of this study not only have important significance for explaining the sensing mechanism of Ptn-WSe2 adsorption to SF6 gas decomposition products, but also provide a potential material for further development of gas sensing sensors.

Raman Spectra of SF6Decomposed Characteristic Products Based on Density Functional Theory

SF6decomposition product analysis is one of the most convenient and efficient methods to diagnose the potential faults of SF6insulated electric equipment in the early stage. Based on SF6decomposition characteristic gas analysis, the operation state of SF6insulated power equipment can be judged by on-line monitoring, so as to ensure its normal operation. Raman spectrum analysis technology can realize the nondestructive detection of gas samples with a single wavelength laser. It has excellent applicability and high efficiency for the detection of SF6decomposition characteristic components. In this paper, molecular configurations of CF4, CO, H2S, SO2were obtained by B3LYP functional that based on density functional theory (DFT), and the Raman frequency and intensity characteristics were calculated by 6-31G (2df, p) basis group. The results were compared with National Institute of Standards and Technology (NIST) standard frequencies and it was found that the optimized configuration has no virtual frequency. The characteristic peaks of CO, CF4, SO2and H2S that were identified by Raman spectrum are respectively 2221.11, 908.97, 1175.24 and 2688.82 cm-1, which are basically consistent with the corresponding NIST standard values. This study not only shows that the Raman spectrum of SF6decomposition products calculated by B3LYP functional function is reliable, but provides a reference for the quantitative detection of SF6decomposition products based on Raman spectrum.

Study on the mechanism and influencing factors of SF6 decomposition products

The decomposition products of GIS basin insulators have characteristic components under four conditions: different defects of GIS basin insulators, cracks and surface discharge of insulation parts inside GIS, abnormal heating of silicon packing basin insulators under steady state current, and particulate discharge of insulation parts. The characteristic components of decomposition products of SULFUR hexafluoride are introduced. Different mechanisms of decomposition products in partial discharge defects and abnormal heating defects were analyzed. The effects of partial discharge defects, abnormal heating defects and adsorbents on the decomposition products were studied.

The Adsorption and Sensing Performances of Ir-modified MoS2 Monolayer toward SF6 Decomposition Products: A DFT Study.

In this paper, the Ir-modified MoS2 monolayer is suggested as a novel gas sensor alternative for detecting the characteristic decomposition products of SF6, including H2S, SO2, and SOF2. The corresponding adsorption properties and sensing behaviors were systematically studied using the density functional theory (DFT) method. The theoretical calculation indicates that Ir modification can enhance the surface activity and improve the conductivity of the intrinsic MoS2. The physical structure formation, the density of states (DOS), deformation charge density (DCD), molecular orbital theory analysis, and work function (WF) were used to reveal the gas adsorption and sensing mechanism. These analyses demonstrated that the Ir-modified MoS2 monolayer used as sensing material displays high sensitivity to the target gases, especially for H2S gas. The gas sensitivity order and the recovery time of the sensing material to decomposition products were reasonably predicted. This contribution indicates the theoretical possibility of developing Ir-modified MoS2 as a gas sensor to detect characteristic decomposition gases of SF6.

Morphological Characteristics of Molybdenum Disulfide and Current Application on Detecting SF6 Decomposing Products

MoS2 has been considered a potential novel material in various fields due to thelarge specific surface area, high carrier mobility and tunable electronic properties. However, with the increasing demand for substrate properties, different strategies have been made to achieve its high performances, usually by adopting the method of controling microstructure. SF6 gas-insulated electrical equipment has gained considerable attention in electric system with the advantages of small volume, high security, strong breaking performance and fracture tolerance high-pressure. Nevertheless, in the process of equipment operation, the SF6 gas will occur inevitably decomposition due to partial discharge, resulting in the deterioration of insulation performance of the equipment. Therefore, detecting SF6 decomposition products is of positive significance for the safe and stable operation of power system. In this mini-review, we start from the synthesis of various MoS2 morphological structures. Then, the beneficial characteristics of the unique synthesized nanostructures at present are analyzed. Besides, we focus on the gas-sensing mechanisms and applications of the MoS2 based sensors for detecting SF6 decomposition products. Finally, the future development in this field is proposed.

Tellurene Nanoflake-Based Gas Sensors for the Detection of Decomposition Products of SF6

Tellurene has a phosphorene-like puckered configuration and exhibits great air stability. This characteristic makes it highly sensitive to some gases, and therefore, it has a huge potential in gas sensing applications. In this paper, the sensing performance of tellurene-based gas sensors toward SF6 decomposition products, including H2S, SO2, SO2F2, and SOF2, was systematically investigated. Three types of tellurene-based gas sensors were fabricated: single tellurene flake with ohmic contact (RCTF sensor), single tellurene flake with nonohmic contact (DCTF sensor), and drop-cast tellurene flakes with heat function (HTF sensor). The RCTF sensor exhibited good sensitivity and selectivity toward hydrogen sulfide but slow recovery speed like most two-dimensional materials. The DCTF sensor exhibited a significant improvement in sensitivity, selectivity, and recovery speed compared with the RCTF sensor. Finally, the HTF sensor demonstrated the fastest recovery speed of all tellurene-based sensors. This work showed that the nonohmic contact and heat pulse are easy and efficient methods to enhance the performance of tellurene-based gas sensors toward hydrogen sulfide, which supports the application potential of tellurene in gas sensors.

Adsorption and gas-sensing properties of Pt2–GaNNTs for SF6 decomposition products

Partial electric discharge faults in gas-insulated switchgear (GIS) seriously affect the operational stability of power systems. In this study, H2S, SO2, SO2F2, and SOF2 were selected as characteristic SF6 decomposition products to characterize the partial electric discharge faults in a GIS. Pt cluster-modified gallium nitride nanotubes (Pt2–GaNNTs) were selected as the gas-sensing material to study their adsorption and gas-sensing performance for SF6 decomposition products H2S, SO2, SO2F2, and SOF2. Calculation results showed that Pt2 clusters presented stable doping structures on GaNNTs that greatly enhanced the surface activity for gas adsorption. The adsorption structures, adsorption energy, charge transfer, energy band, density of states, and molecular orbit were analyzed on the basis of density functional theory. Gas molecules formed stable structures on the surfaces of Pt2–GaNNTs through chemical adsorption. The order of adsorption ability was SO2 > H2S > SOF2 > SO2F2, and that of gas-sensing ability was SOF2 > SO2 > H2S > SO2F2. In this article, a new method to detect the partial electric discharge in GIS is proposed. The proposed method helps enhance the running stability of GIS.

Palladium modified MoS2 monolayer for adsorption and scavenging of SF6 decomposition products: A DFT study

Based on the first principle calculation, Pd-doped MoS2 (Pd–MoS2) monolayer has been proposed to adsorb the main decomposition products of SF6: SOF2 and SO2F2. Pd–MoS2 monolayer, SF6 adsorbed Pd–MoS2 monolayer, SOF2 and SO2F2 adsorbed Pd–MoS2 monolayer are built and optimized to obtain the most stable structures. In order to meet to the actual situation, both of single and double gas molecules adsorption were considered in this study. The adsorption energy, charge transfer amount, total density of states (TDOS), projected density of states (PDOS), and the molecular orbits were calculated to analyze the adsorption mechanism of Pd–MoS2 monolayer to SOF2 and SO2F2. The results show that Pd–MoS2 monolayer can only adsorb a single molecule at one Pd doping site. Both of SOF2 and SOF2 adsorptions belong to chemisorption due to the strong chemical activity of the doped Pd atom. The simulation results show that Pd–MoS2 adsorbent could be a potential material for SOF2 and SO2F2 removing. This study lays a key foundation to design Pd–MoS2 monolayer adsorbent using in SF6-insulated equipment.

Tunable SO2-sensing performance of arsenene induced by Stone-Wales defects and external electric field

Reported here is a first-principle study of the adsorption of four SF6 decomposition products on pristine arsenene and arsenene with Stone-Wales defects (SW). The results revealed that pristine arsenene exhibited high sensitivity and selectivity to SO2, and Stone-Wales defects enhanced the SO2-sensing performance. The presence of ambient O2, H2O, and SF6 only slightly affected the adsorption on both pristine and SW arsenene. We also investigated the effect of biaxial strain and an external electric field on the SO2 detection of SW arsenene. The SO2 adsorption strength on SW arsenene was drastically enhanced or weakened, depending on the direction of the electric field, which is desirable for realizing the ultra-sensitive adsorption and desorption of SO2.

Adsorption and Gas Sensing Properties of the Pt3-MoSe2 Monolayer to SOF2 and SO2F2.

SF6 acts as an insulation gas in gas-insulated switchgear (GIS), which inevitably decomposes under partial discharge caused by insulation defects. This work is devoted to finding a new gas-sensing material for detecting two characteristic SF6 decomposition products: SOF2 and SO2F2. The platinum-cluster-modified molybdenum diselenide (Pt3-MoSe2) monolayer has been proposed as a gas sensing material. Based on first-principles calculations, the adsorption properties and the mechanism were studied by analyzing the adsorption structures, adsorption energy, charge transfer, density of states, and molecular orbitals. The adsorption ability of Pt3-MoSe2 to SO2F2 is stronger than that to SOF2 due to its chemisorption property. The obvious change of conductivity of the adsorption system during the gas adsorption process shows that Pt3-MoSe2 is sensitive to both of the gas molecules. In addition, the modest adsorption energy signifies that the gas adsorption process can be reversible, which confirms the feasibility of Pt3-MoSe2-based gas sensors. Our calculation suggests that Pt3-MoSe2-based gas sensors can be employed in GIS for partial discharge detection.

Theoretical investigation of neutral decomposition by-products of SF6 + CO2 mixture in the existence of H2O

Investigation of the decomposition products of SF6–CO2 gas mixture, which is a promising binary gas mixture with dilute SF6 content to be used in gas-insulated systems in power electrical systems, is very important in terms of the sustainability of operating conditions, environmental and human health. This study determines the decomposition products of the SF6–CO2 gas mixture in the presence of H2O, depending on the reaction paths by the B3LYP method at 6-311 + G(d,p) level set employing the density functional theory method. The decomposition products obtained by this method have been confirmed by the findings of experimental studies in the literature. Decomposition pathways of SF6 + CO2 mixture in the absence and presence of H2O are constructed in order to analyze relative energy changes of the decomposed by-products to select the most probable ones.

Influence of Pd Clusters Doping on Gas Sensing Properties of TiO₂(101) Nanotubes to SF₆ Decomposition Products

Detection and analysis of sulfur hexafluoride (SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> ) decomposition components is one of the most used methods to realize online monitoring of gas insulated switchgear (GIS) faults. In this paper, Pd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -doped anatase TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (101) surface was constructed, and studied about its geometric and electronic properties to characteristic SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> decomposition products: SOF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> based on DFT calculations. Comparing with intrinsic TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (101), the conductivity of Pd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (101) surface decreases dramatically. Studies on adsorption energy, charge transfer, and adsorption distance show that Pd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (101) shows strong chemisorption to SOF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> molecules. Based on density of states and molecular orbital theory analysis, it is found that the adsorption of SOF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> can dramatically change the conductivity in different degrees. As a result, the Pd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (101) surface exhibits high gas sensitivity and selectivity to SOF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> molecules. Our calculations would be meaningful for the development of new sensing materials for SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> decomposition components detection.

Research on Environmental Protection Treatment for Ex-Service SF6 Adsorbent

SF6 adsorbents absorb many toxic SF6 decomposition products, such as SOF2, SO2F2, and H2S. Ex-service SF6 adsorbents that did not undergo environmentally friendly processing will seriously harm the environment. In this work, thermogravimetric analysis and Fourier transform infrared spectroscopy were used to investigate the adsorbates of ex-service SF6 adsorbents. Adsorbent recycling based on the thermal method was also studied. The vacuum thermal method increased the recycling efficiency of ex-service SF6 adsorbents to 85%-90%. In addition, the adsorbents recovered through thermal method could be reused in SF6-gas-insulated equipment. Considering their influence on equipment operation and maintenance, a harmless treatment technology for ex-service SF6 adsorbents with Ca(OH)2 was proposed. The adsorption and desorption behaviors of SF6 adsorbents were predicted via destiny functional theory. The best treatment effect could be obtained when the Ca(OH)2 amount was equal to 20% of the treatment weight of the adsorbents, and the treatment temperature was maintained at 90 °C. The economic feasibility of the harmless treatment for ex-service SF6 adsorbents with Ca(OH)2 was higher than that of the thermal method.

DFT study of SF6 decomposed products on Pd–TiO2: gas sensing mechanism study

Detecting the species and concentrations of SF6 decomposed products is crucial for on-line monitoring the running status of SF6-insulated equipment. TiO2-based gas sensing material shows a great potential in SF6 decomposed products detection. In order to improve the sensitivity and selectivity of TiO2-based gas sensing material, Pd atom modified TiO2 (Pd–TiO2) was proposed to analyze its adsorption properties to three characteristic decomposition products of SF6: SO2, SOF2, and SO2F2. The results show that Pd–TiO2 possesses strong adsorption property to these gas molecules because of the high chemical activity of the doped Pd atom. Density of states, differential charge density, and molecular orbits are studied to analyze the gas sensing mechanism of Pd–TiO2 to the gas molecules. It is found that gas molecules adsorption raises an increase of conductivity to different extents, which can be applied to identify the species and concentrations of SF6 decomposed products under electric discharge. Therefore, Pd–TiO2 can be a promising gas sensing material using in SO2, SOF2 and SO2F2 detection with high selectivity and sensitivity. This plays an important role in the detection of SF6 decomposition gas.

Au Catalyst-Modified MoS2 Monolayer as a Highly Effective Adsorbent for SO2F2 Gas: A DFT Study.

To ensure the stable operation of gas-insulated equipment, removal of SF6 decomposition products of sulfur hexafluoride (SF6) is one of the best methods. SO2F2 is one of the typical decomposition products of SF6, while the Au-modified MoS2 (Au–MoS2) monolayer is a novel gas adsorbent. Therefore, based on the first-principles calculation, the adsorption properties of the SO2F2 molecule on the Au–MoS2 monolayer are calculated. Furthermore, the adsorption energy, charge transfer, and structure parameters were analyzed to obtain the most stable adsorption structure. These results indicate that all of the adsorption processes are exothermic. To better study the adsorption mechanism between the SO2F2 molecule and the Au–MoS2 monolayer, the density of states, the highest occupied molecular orbital, the lowest unoccupied molecular orbital, and electron density difference were obtained. At last, we conclude that the interaction between the SO2F2 molecule and the Au–MoS2 monolayer was chemisorption. This study provides a theoretical basis to prepare the Au–MoS2 monolayer for the removal of SF6 decomposition products.

Effect of Nickel Doping on Adsorption of SF6 Decomposition Products over MoS2 Surface

To ensure the operating stability of SF6-insulated equipment, an Ni-MoS2 monolayer has been used as an adsorbent to remove the characteristic decomposition products of SF6, viz. SOF2 and SO2F2 gases, from SF6-insulated equipment. All of the calculations are carried out in the density functional theory (DFT) framework. Several adsorption configurations are built and optimized to determine the most stable adsorption structure. In addition, the adsorption geometry, adsorption energy, density of states (DOS), charge transfer, transition states, and electron density difference are calculated to analyze the adsorption properties. The results show that the Ni-MoS2 monolayer exhibits excellent adsorption properties towards both target gases. SOF2 adsorbs on the Ni-MoS2 monolayer by nondissociative chemisorption, while SO2F2 adsorption occurs via dissociative chemisorption. Due to the strong chemical activity of Ni, it significantly increases the electrical conductivity and enhances the adsorption properties of MoS2. The Ni-MoS2 monolayer shows excellent sensitivity to SOF2 and SO2F2, reflected in decreases of the electrical conductivity after adsorption of SOF2 and SO2F2. The Ni-MoS2 monolayer could thus be a promising material for removal of these characteristic SF6 decomposition products under partial discharge conditions. The results of these calculations provide a new approach to ensure the operational stability of SF6-insulated gas-insulated switchgear (GIS) equipment.

A DFT study on the adsorption of Ga-BNNT to SF6 decomposition products under partial discharge

Abstract Detecting the partial discharge by analyzing the decomposition products of SF6 is very important for diagnosing and evaluating the operating state of GIS. Ga-doped single-walled boron nitride nanotube (Ga-BNNT) gas sensing material was proposed to analyze its adsorption properties to SOF2 and SO2F2 gases based on DFT calculations. The calculation results show that the conductivity of BNNT improves after Ga atom doping. Ga dopant acts as the active site to adsorb gas molecules, which greatly enhances the sensitivity and selectivity of BNNT material to SOF2 and SO2F2. Both of gas molecules interact with Ga-BNNT by chemisorption, while no chemical bonds of gas molecule break during the adsorption process. SOF2 adsorption reduces the conductivity of the adsorption system. On the contrary, the SO2F2 acts as an electron contributor, which enhances the conductivity after adsorption. This study provides a theoretical basis for gas sensor design.

DFT-based study on H2S and SOF2 adsorption on Si-MoS2 monolayer

H2S and SOF2 gas are two typical decomposition products of SF6 gas under partial discharge condition. Based on the density functional theory (DFT), several doping structures of Si-MoS2 and adsorption structures of gas adsorbed Si-MoS2 were investigated. The electronic property, adsorption energy, charge transfer, and electron density difference were calculated to analyze the adsorption mechanism. Compared with the structure of pristine MoS2 monolayer, Si doping improves the surface activity of MoS2 monolayer. Moreover, the introduction of Si atom increases the effects of orbital hybridization between gas molecules and MoS2 monolayer, and promotes the charge transfer. Especially, SOF2 possesses a large adsorption energy with Si-MoS2 by crossing a small energy barrier. In addition, the good compatibility of Si-MoS2 with SF6 atmosphere, makes it a promising adsorbent for SF6 decomposition products removal.