Gas sensor for early partial discharge detection of low-oil equipment and sensing performance simulation method thereof

Abstract

The invention discloses a gas sensitive sensor for early partial discharge detection of low-oil equipment and a sensing performance simulation method thereof, the gas sensitive sensor comprises a SnS modified SnO2 composite structure, and the composite structure comprises SnO2 superunit cells and SnS molecules doped into the SnO2 superunit cells. According to the sensing performance simulation method, the experiment cost can be reduced, and important guidance and technical support are provided for improvement of the performance of the gas sensor; according to the sensing performance simulation method, the gas sensitive sensor has the advantages of stable doping performance and good adsorption detection efficiency due to the adoption of the SnS modified SnO2 composite structure, and the gas sensitive sensing performance on H2 and C2H2 can be enhanced, so that the detection capability on early partial discharge is improved.

Description

Technical Field

[0001] The present invention belongs to the field of online monitoring of electrical equipment, and in particular relates to a gas sensor for early partial discharge detection of low-oil equipment and a method for simulating its sensing performance. Background Art

[0002] In power systems, transformer bushings, a typical low-oil device, are insulating devices used to conduct internal voltage from or to the transformer, connecting power lines to the transformer's internal conductive components. Their stable and reliable operation is crucial to the safety and stability of the power system. A transformer bushing failure can cause a serious power outage, impacting the continuity of power supply.

[0003] The continuous development of power technology has placed higher demands on the operating status monitoring and fault diagnosis of high-voltage insulation equipment, smart microgrids, and energy storage systems. Metal oxide semiconductors, due to their excellent gas-sensing properties, high stability, and cost-effectiveness, have occupied a key position in applications such as high-voltage insulation equipment diagnosis, smart microgrid monitoring, and energy storage systems.

[0004] Two-dimensional metal oxide semiconductors (such as SnO2) offer significant advantages in gas detection due to their unique physical and chemical properties. For example, their stability and selectivity enable accurate detection of dissolved gases in oil at relatively low concentrations. This makes them valuable for condition monitoring of oil-poor equipment such as transformer bushings and reactors.

[0005] In oil-poor equipment, such as transformer bushings, dissolved gases provide crucial information about the insulation status of the equipment. When insulation failures occur within the equipment, such as arcing or thermal damage to the insulation material, characteristic gases such as hydrogen (H2) and acetylene (C2H2) are generated. Changes in the concentration and type of these gases can serve as early warning signals of equipment failure. By monitoring the concentration and type of dissolved gases in oil, equipment health can be assessed promptly, potential faults identified in advance, and appropriate maintenance measures implemented to prevent further escalation of equipment failures.

[0006] Currently, intrinsic SnO2 semiconductor sensing materials have found limited application in oil-reduced equipment such as transformer bushings and reactors. However, in practical applications, the sensitivity of existing two-dimensional SnO2 metal oxide gas sensors still cannot meet the demands of high-precision detection due to the complexity of the equipment's operating environment and the increasing precision required for gas detection. Further improving the sensitivity of two-dimensional SnO2 metal oxide gas sensors in practical applications, thereby enhancing the accuracy of dissolved gas detection in oil and enabling more accurate assessment of equipment status, remains a key research challenge. Furthermore, minimizing experimental costs and improving research efficiency are also of great concern. Summary of the Invention

[0007] In order to overcome the shortcomings of the existing technology, the present invention proposes a gas sensor for early partial discharge detection of low-oil equipment and a sensing performance simulation method thereof, so as to enhance the gas sensing performance of H2 and C2H2, effectively improve the detection capability of SnO2-based gas sensors for early partial discharge, and at the same time reduce experimental costs and improve research efficiency.

[0008] The first aspect of the present invention relates to a gas sensor for early detection of partial discharge in oil-depleted equipment. The gas sensor comprises:

[0009] A SnS-modified SnO2 composite structure comprises a SnO2 supercell and SnS molecules doped into the SnO2 supercell.

[0010] Preferably, the SnO2 supercell is a rutile tetragonal structure with the (110) crystal plane as the characteristic plane.

[0011] Preferably, in the SnS-modified SnO2 composite structure, the SnS molecules are doped in a horizontal posture at the top sites or holes of the surface atoms of the SnO2 supercell or at the bridge sites of the chemical bonds between the surface atoms.

[0012] The second aspect of the present invention relates to a method for simulating the sensing performance of a gas sensor for early partial discharge detection in low-oil equipment, as described in the first aspect of the present invention. The method comprises the following steps:

[0013] Establish a geometry-optimized intrinsic SnO2 supercell model, geometry-optimized free-state models of H2 and C2H2 molecules, and geometry-optimized free-state SnS single-molecule model for doping.

[0014] The SnS-modified SnO2 composite doping model was constructed using the geometrically optimized intrinsic SnO2 supercell model and the geometrically optimized free SnS single molecule model for doping.

[0015] The adsorption site models of H2 and C2H2 molecules were constructed using the SnS-modified SnO2 composite doping model and the geometrically optimized free-state models of H2 and C2H2 molecules, respectively.

[0016] By using the constructed adsorption site model of H2 and C2H2 molecules, combined with the state density, charge transfer amount, adsorption energy, doping energy, band structure and work function, the adsorption performance and electronic behavior characteristics of the SnO2 gas sensor for H2 and C2H2 are analyzed, thereby determining the sensing performance of the SnO2 gas sensor.

[0017] Preferably, the step of establishing a geometrically optimized intrinsic SnO2 supercell model comprises:

[0018] The periodic boundary model is used to construct an intrinsic SnO2 supercell containing 27 Sn atoms and 54 O atoms. The crystal plane of the intrinsic SnO2 supercell is (110) and the size of the vacuum plane layer is The height of the vacuum plane layer is

[0019] The intrinsic supercell model is geometrically optimized, including:

[0020] The generalized gradient approximation method and PBE function are used to describe the electron exchange correlation in the intrinsic SnO2 supercell, and the iterative convergence of the electron self-consistent field is performed based on the electron exchange correlation; wherein the convergence accuracy of the electron self-consistent field is set to

[0021] The van der Waals forces and long-range interactions in the intrinsic SnO2 supercell are treated using a dual numerical plus polarization basis set and the Grimme method. During the treatment, the convergence accuracy of the maximum stress and displacement is set to and

[0022] The DFT functional semi-core pseudopotential is used to eliminate the nuclear relativistic effect of metal atoms in the intrinsic SnO2 supercell; in the calculations related to the DFT functional semi-core pseudopotential, the Brillouin k-point is set to 4×4×1.

[0023] Preferably, in the intrinsic SnO2 supercell model after geometry optimization, the bandwidth is 0.888 eV, and the bond lengths between the surface Sn atoms and the three nearest oxygen atoms are and

[0024] Preferably, in the free state model of the H2 molecule after geometry optimization, the HH bond length is

[0025] Preferably, in the free state model of the C2H2 molecule after geometry optimization, the C-C and C-H bond lengths are and

[0026] Preferably, in the geometry-optimized free SnS single molecule model for doping, the Sn-S bond length is

[0027] Preferably, in the SnS-modified SnO2 composite doping model: the initial doping distance of the SnS molecules is set to SnS molecules are doped in a horizontal posture at the top positions or holes of the surface atoms of the SnO2 supercell or at the bridge positions of the chemical bonds between the surface atoms.

[0028] Preferably, in the SnS modified SnO2 composite doping model, when the SnS molecules are doped in a horizontal posture at the top position of the Sn atoms on the surface of the SnO2 supercell: the Sn-S bond in the SnS molecules after doping is The S atoms in the doped SnS and the two nearest O atoms in the surface layer of the SnO2 supercell 1s and O 3s The bond lengths between and The S atoms in the doped SnS and the two nearest Sn atoms in the surface layer of the SnO2 supercell 1s and Sn 2s The bond lengths between and The Sn atoms in the doped SnS and the nearest O atoms in the surface layer of the SnO2 supercell 2s The bond length between

[0029] Preferably, in the adsorption site model of H2 molecules: the initial adsorption distance of H2 molecules is set to The H2 molecule is arranged at the top position or bridge position of the Sn-S bond in the SnS molecule in a vertical or parallel posture.

[0030] Preferably, in the adsorption site model of C2H2 molecules: the initial adsorption distance of C2H2 molecules is set to C2H2 molecules are arranged at the top, bridge and hole positions of the O atoms on the surface of SnO2 in horizontal and vertical positions respectively.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. Intrinsic SnO2 with a rutile tetragonal structure with the (110) crystal plane as the characteristic plane is used. Its band structure has good continuity and is a good direct band gap semiconductor, which is easy to modify and adsorb. By doping the homologous sulfide SnS at the top or hole positions of the surface atoms of the SnO2 supercell or the bridge positions of the chemical bonds between the surface atoms, especially doping at the top positions of the Sn atoms on the surface of the SnO2 supercell, the doping performance can be stabilized, thereby effectively improving the adsorption performance and electronic properties of the SnO2-based gas sensor. The charge transfer amount of the SnO2-based gas sensor during the doping and adsorption process is further improved, the state density distribution is optimized, the work function is improved, and the gas sensing performance of H2 and C2H2 is enhanced, thereby improving the detection capability of early partial discharge.

[0033] 2. Based on first-principles calculations, a geometrically optimized intrinsic SnO2 supercell model, geometrically optimized free-state models of H2 and C2H2 molecules, and a geometrically optimized free-state SnS single-molecule model for doping were established. Furthermore, a SnS-modified SnO2 composite doping model and adsorption site models for H2 and C2H2 molecules were constructed. The adsorption performance and electronic behavior of the SnS-modified SnO2 gas sensor for H2 and C2H2 were analyzed by combining state density, charge transfer, adsorption energy, doping energy, band structure, and work function, thereby determining the sensing performance of the SnS-modified SnO2 gas sensor. This approach allows highly accurate simulation data to be obtained through simulation alone, without consuming extensive human and material resources. This provides important guidance and technical support for improving gas sensor performance and significantly reduces experimental costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the intrinsic rutile SnO2(110) molecular layer model after geometric optimization of the present invention; Figure 1 The parts numbered (a) to (c) correspond to the front view, top view and left view respectively;

[0035] Figure 2 It is the molecular model of free H2 and C2H2 after geometry optimization; Figure 2 The parts numbered (a) and (b) correspond to H2 and C2H2, respectively;

[0036] Figure 3 is the free SnS molecule after geometry optimization, and its Sn-S bond length is

[0037] Figure 4(a) is the density of states diagram of intrinsic SnO2 and free SnS, H2 and C2H2;

[0038] Figure 4(b) is the band structure diagram of the SnO2 monolayer in the intrinsic SnO2 supercell model;

[0039] Figure 5 It is a composite doping model of SnO2 modified by SnS at different doping sites; Figure 5 The composite doping models corresponding to numbers (a) to (f) are denoted as 1-SnS@SnO2 to 6-SnS@SnO2;

[0040] Figure 6 It is the 1-SnS@SnO2 composite doping model after geometry optimization; Figure 6 The parts numbered (a) and (b) correspond to the front view and the left view respectively;

[0041] Figure 7 It is the density of states diagram of intrinsic SnO2, SnS and SnS modified SnO2 composite structure;

[0042] Figure 8 is the local density of states diagram of intrinsic SnO2 and SnS-modified SnO2; Figure 8 The parts numbered (a) and (b) correspond to the intrinsic SnO2 and SnS-modified SnO2 composite structures, respectively;

[0043] Figure 9 This is a schematic diagram of the five adsorption sites of H2 on intrinsic SnO2 molecules;

[0044] Figure 10 Schematic diagram of the four adsorption sites of H2 on SnS-modified SnO2 composite structure;

[0045] Figure 11 This is the geometrically optimized SnS-modified SnO2 composite structure model with H2 adsorption, in which H2 is adsorbed horizontally at the bridge position of the Sn-S bond in the SnS molecule; Figure 11 The numbers (a) and (b) in the figure correspond to the main view and the left view, respectively;

[0046] Figure 12 It is the density of states diagram of the intrinsic SnO2 adsorbed with H2 and the SnS modified SnO2 composite structure adsorbed with H2;

[0047] Figure 13 It is the local density of states diagram of SnO2 adsorbed with H2 and SnS modified with H2 adsorbed SnO2 composite structure; Figure 13 The parts numbered (a) and (b) correspond to the intrinsic SnO2 adsorption system and the SnS-modified SnO2 adsorption system, respectively;

[0048] Figure 14 This is a schematic diagram of the five adsorption sites of intrinsic SnO2 molecules adsorbing C2H2;

[0049] Figure 15Schematic diagram of the four adsorption sites of C2H2 on SnS-modified SnO2 composite structure;

[0050] Figure 16 This is the geometrically optimized SnS-modified SnO2 composite structure model with C2H2 adsorbed, where C2H2 is adsorbed horizontally at the top position of the S atom in the SnS molecule. Figure 16 The parts numbered (a) and (b) correspond to the main view and left view respectively;

[0051] Figure 17 It is the density of states diagram of SnO2 adsorbed with C2H2 and SnS-modified SnO2 adsorbed with C2H2;

[0052] Figure 18 It is the local density of states diagram of SnO2 adsorbed with C2H2 and SnS-modified SnO2 adsorbed with C2H2; Figure 18 The distributions numbered (a) and (b) correspond to the intrinsic SnO2 adsorption system and the SnS-modified SnO2 adsorption system, respectively. DETAILED DESCRIPTION

[0053] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without making creative efforts are all within the scope of protection of the present invention.

[0054] Example 1

[0055] This embodiment provides a gas sensor for early detection of partial discharge in low-oil equipment. The gas sensor includes:

[0056] A SnS-modified SnO2 composite structure comprises a SnO2 supercell and SnS molecules doped into the SnO2 supercell.

[0057] In this embodiment, the doping of the homologous sulfide SnS with high ductility and surface activity can effectively improve the adsorption performance and electronic properties of the SnO2-based gas sensor, further improve the charge transfer amount of the SnO2-based gas sensor during the doping and adsorption process, optimize the state density distribution, improve the work function, enhance the H2 and C2H2 gas sensitive sensing performance, and thus improve the detection capability of early partial discharge.

[0058] Preferably, the SnO2 supercell is a rutile tetragonal structure with the (110) crystal plane as the characteristic plane. The rutile intrinsic SnO2 band structure of this structure has good continuity, which has the advantage of being easy to subsequently modify and adsorb.

[0059] Preferably, in the SnS-modified SnO2 composite structure, the SnS molecules are doped in a horizontal posture at the top positions or hole positions of the surface atoms of the SnO2 supercell or the bridge positions of the chemical bonds between the surface atoms. More preferably, the SnS molecules are doped in a horizontal posture at the top positions of the Sn atoms on the surface of the SnO2 supercell. Such doping sites can stabilize the doping performance, thereby effectively improving the adsorption performance and electronic properties of the SnO2-based gas sensor, further improving the charge transfer amount of the SnO2-based gas sensor during the doping and adsorption process, optimizing the state density distribution, improving the work function, enhancing the gas-sensitive sensing performance of H2 and C2H2, and thus improving the detection capability of early partial discharge. The differences between different doping sites are described in detail in the sensing performance simulation method of Example 2.

[0060] Example 2

[0061] This embodiment provides a method for simulating the sensing performance of a gas sensor for early partial discharge detection in low-oil equipment as described in Embodiment 1.

[0062] This method involves geometric optimization and electronic performance analysis of the binding energy, adsorption energy, bond length, band structure, lowest unoccupied molecular orbital and highest occupied molecular orbital, work function, etc. of SnS, SnO2 and doping structures and adsorption systems through molecular theoretical simulation.

[0063] Doping distance (d d ) and adsorption distance (d a ) is a visual representation of the plane distance between the lowest part of the dopant and target gas molecules and the nearest atom of the substrate. d and d a The smaller the value, the more intense the doping and adsorption process is, and the more stable the system structure is after the reaction.

[0064] The most stable doping system was obtained by analyzing different sites on the SnO2 substrate structure. The binding energy of SnS and SnS (E bin ) is calculated by the following formula.

[0065]

[0066] Wherein, SnS@SnO2 is the doping system after SnS is doped into SnO2; is the doping system energy after SnS is doped into SnO2; is the energy of intrinsic SnO2; E SnS is the energy of SnS nanostructure.

[0067] Adsorption energy of target gas molecules on intrinsic SnO2 and SnS@SnO2 (E ads )for:

[0068]

[0069] Where, is the overall energy of intrinsic SnO2 or SnS@SnO2 after adsorbing the target molecule; is the doping system energy after SnS is doped into SnO2; E Gas is the energy of a single targeted gas molecule.

[0070] The Mulliken charge transfer capacity (Q Tra ) is calculated by the following formula.

[0071] Q Tra =Q aft -Q bef (3)

[0072] Where Q bef and Q aft are the charges of the intrinsic SnO2 monolayer before and after adsorption. Tra When Q > 0, it means that the electrons are transferred from the gas molecules (dopants) to the substrate gas-sensitive material (intrinsic SnO2 monolayer). On the contrary, when Q Tra When <0, it indicates that electrons are transferred from the substrate gas-sensitive material (intrinsic SnO2 monolayer) to the gas molecules (dopants).

[0073] The work function of different doping structures and adsorption systems can be determined by formula (4)

[0074]

[0075] Among them, E f is the Fermi energy, E Vac is the electrostatic potential in vacuum.

[0076] In order to better illustrate the effects achieved by the present invention, the specific steps of the method involved in this embodiment are given below.

[0077] Step 1: Establish the geometrically optimized intrinsic SnO2 supercell model, the geometrically optimized free-state models of H2 and C2H2 molecules, and the free-state SnS single-molecule model for doping.

[0078] Specifically, the geometrically optimized intrinsic SnO2 supercell model is established including:

[0079] Step 11: construct an initial SnO2 supercell containing 27 Sn atoms and 54 O atoms using a periodic boundary model; the crystal plane of the intrinsic SnO2 supercell is (110) crystal plane, and the size of the vacuum plane layer is The height of the vacuum layer is

[0080] Among them, the size setting of the intrinsic SnO2 supercell comprehensively considers the calculation time, the possibility of calculation failure or distortion, and the existence and stability of the cell at the microchemical level. Specifically, the size of the cell will directly affect the calculation time. A cell that is too large will result in a longer calculation time. At the same time, a cell that is too large or too small may not exist or cannot exist stably at the microchemical level. Furthermore, a cell that is too large or too small will cause simulation failure or distortion. Therefore, in this step, the intrinsic supercell is constructed to contain 27 Sn atoms and 54 O atoms. This is a structural size that is stable and conforms to the actual chemical microstructure after specific microscopic verification and continuous attempts at different sizes in the simulation software.

[0081] In addition, the crystal plane of the intrinsic SnO2 supercell is set to (110) because it is the most stable crystal plane; the size of the vacuum plane layer is set to The height of the vacuum layer is This is to prevent gas molecules from causing crosstalk between the circulating vacuum layers.

[0082] Step 12: geometrically optimizing the intrinsic SnO2 supercell model, including:

[0083] The generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE) function are used to describe the electron exchange correlation in the intrinsic SnO2 supercell, and the iterative convergence of the electron self-consistent field is performed based on the electron exchange correlation; preferably, the convergence accuracy of the electron self-consistent field is set to

[0084] The double-numeric basis with polarization functions (DNP) and the Grimme method are used to treat the van der Waals forces and long-range interactions in the intrinsic SnO2 supercell. Preferably, the convergence accuracy of the maximum stress and displacement is set to and

[0085] DFT functional semi-core pseudopots (DSSP) are used to eliminate the nuclear relativistic effects of metal atoms in the intrinsic SnO2 supercell. Preferably, the Brillouin k-point is set to 4×4×1 in calculations related to DFT functional semi-core pseudopotentials.

[0086] In the above-mentioned geometric optimization process, by carefully setting the convergence accuracy of the electronic self-consistent field, the convergence accuracy of the maximum stress and displacement, and the Brillouin k-point, more accurate and stable geometric optimization results can be obtained, ensuring the efficiency of the optimization process and better saving computing resources.

[0087] like Figure 1 Shown are the specific atomic arrangements and bonding characteristics of the intrinsic SnO2 supercell model after geometry optimization, where the red atoms are O atoms and the gray atoms are Sn atoms. The intrinsic SnO2 unit cell after geometry optimization has a regular symmetrical structure, in which tin atoms and oxygen atoms are distributed in a staggered manner. The main body of the unit cell is a three-layer structure composed of separate upper and lower oxygen atom layers. After geometry optimization, it was observed that the bond lengths of the chemical bonds Sn1-O1, Sn1-O2 and Sn1-O3 between the four key atoms on the surface of the model (i.e., the tin atom Sn1 and the three surrounding oxygen atoms O1~O3) were and

[0088] The establishment of the free-state models of H2 and C2H2 molecules after geometry optimization and the free-state SnS single-molecule model for doping after geometry optimization can refer to the establishment process of the intrinsic SnO2 supercell model after geometry optimization.

[0089] Figure 2 The free-state models of H2 and C2H2 molecules after geometric optimization are shown. Among them, the HH bond length in the free-state model of the optimized H2 molecule is The C—C and C—H bond lengths in the optimized free-state model of C2H2 molecules are and It can be seen that the C2H2 molecule has a high degree of symmetry.

[0090] Since the SnO2 supercell itself is cyclic, a free SnS single molecule for doping was constructed according to the geometric configuration of SnS, and each supercell contains only one doped SnS molecule. Figure 3 is the free SnS molecule after geometry optimization, and its Sn-S bond length is

[0091] Figure 4(a) shows the DOS (Density of States) of the SnO2 monolayer and free SnS, H2, and C2H2 in the intrinsic SnO2 supercell model. It can be seen that the energy distribution of SnO2 near the Fermi level (0 eV) is relatively continuous, and the integrated energy near the Fermi level is high, demonstrating its excellent conductivity as a semiconductor metal oxide. Figure 4(b) shows the band structure of the SnO2 monolayer in the intrinsic SnO2 supercell model. The valence band maximum is located at the Γ point, while the conduction band minimum is located at the X point. The band structure is very continuous, indicating that it is a good direct bandgap semiconductor, which is easy to modify and adsorb. During the subsequent adsorption process, electrons can jump from the top of the valence band to the bottom of the conduction band. The excellent semiconductor properties reflect the good conductivity of SnO2.

[0092] Step 2: Use the geometrically optimized intrinsic SnO2 supercell model and the geometrically optimized free SnS single molecule model for doping to construct a SnS-modified SnO2 composite doping model.

[0093] In this step, when constructing the SnS-modified SnO2 composite model (denoted as SnS@SnO2), the initial doping distance is set to Nearby, preferably In the process of metal oxide doping, doping is generally performed at the top position (T position), bridge position (B position) and hole position (V position) of the surface atoms of the metal oxide. Therefore, according to the molecular configuration of SnS, three doping sites (a total of six doping sites) are selected for doping at the O atoms and Sn atoms on the surface of SnO2, corresponding to six doping configurations, such as Figure 5 As shown. Figure 5 In the figure, the composite structures corresponding to numbers (a) to (f) are denoted as 1-SnS@SnO2 to 6-SnS@SnO2, respectively.

[0094] like Figure 6 The figure shows the geometrically optimized 1-SnS@SnO2 doping configuration (this configuration corresponds to the SnS molecule being doped in a horizontal position at the top of the Sn atom on the SnO2 surface). It can be observed that when SnS is introduced to the SnO2 surface, the O and Sn atoms on the surface undergo interlayer displacement, while the O atom on the top undergoes a more obvious deformation. This is because the strong semiconductor properties of SnS as a homologous sulfide produce a more obvious interaction with the O atoms on the SnO2 surface. The doping of SnS further changes the electronic properties of the doped substrate, which will be beneficial to the subsequent gas adsorption process. During the doping process, new chemical bonds are generated between the S atoms in SnS and the Sn atoms and the substrate. The bond length of the Sn-S bond (Bond-1) in the SnS doped molecule is pulled by the substrate atoms. Stretch to 1- Newly generated SO in SnS@SnO2 1s Bond-2 and S-Sn 1s Bond (Bond-3) and S-Sn 2s The bond lengths of Bond-4 are and Sn-O 2s Bond (Bond-5) and SO 3s The bond lengths of Bond-6 are and The relevant bond lengths of the SnS and SnO2 surfaces also changed to varying degrees before and after doping. Mulliken charge analysis shows that the SnS and SnO2 unit cell structures are not charged before adsorption, but charge transfer occurs between the doped structure and the substrate structure after adsorption.

[0095] like Figure 7 The figure shows the DOS energy distribution (i.e., density of states) of intrinsic SnO2, SnS, and the SnS-modified SnO2 composite structure after doping (denoted as SnS@SnO2). It can be seen from the figure that the energy distribution of each energy level in the DOS energy distribution of the SnS-modified SnO2 composite structure after doping has not changed significantly, and the energy near the Fermi level still has a continuous energy distribution. The energy near -1.05eV is significantly enhanced, which is due to the strong interaction between the SnS molecules and the orbits of Sn and O atoms. The characteristic peak near -11.2eV in the SnS-modified SnO2 composite structure is transformed from the characteristic peak of -10.2eV of intrinsic SnS, which means that the doping process causes the energy level near -10.2eV to produce an energy level transition, which is reflected in the DOS as a left shift of the characteristic peak, further proving the success of the chemical doping process.

[0096] like Figure 8The PDOS energy distribution (i.e., local density of states) diagram of intrinsic SnO2 and SnS-modified SnO2 composite structures is shown. The dashed line represents the Fermi level. The figure shows that with the doping of SnS molecules, significant orbital peak overlap occurs near -11.2eV, -7.3eV, -1.3eV, 0.91eV, 3.2eV, and 4.6eV. This is due to the high hybridization of the substrate and dopant molecular orbitals caused by the chemical bond between the SnS dopant molecules and the substrate, further demonstrating the successful doping process. The electron energy arrangement near the Fermi level directly determines the conductivity of the system. Compared with the intrinsic SnO2 molecule, the horizontal axis position of the orbital characteristic peak of the SnS@SnO2 system has shifted slightly to the right, thereby increasing the height and width of the characteristic peak of the electron energy near the Fermi level, further leading to an increase in the conductivity of the system, which is reflected macroscopically as a decrease in the resistance value of the sensing system.

[0097] Step 3. Using the SnS-modified SnO2 composite doping model and the geometrically optimized free state models of H2 and C2H2 molecules, the adsorption site models of H2 and C2H2 molecules are constructed respectively. Combined with the state density, charge transfer amount, adsorption energy, doping energy, band structure and work function, the adsorption performance and electronic behavior characteristics of the SnO2 gas sensor for H2 and C2H2 are analyzed to determine the sensing performance of the SnO2 gas sensor.

[0098] like Figure 9 The figure shows the original adsorption site model of intrinsic SnO2 molecules adsorbing H2. Due to the high symmetry of H2 molecules, five adsorption sites are set on the Sn atoms and O atoms on the SnO2 surface, which are recorded as 1-H2 / SnO2 to 5-H2 / SnO2. Figure 9 The initial adsorption distance is set to Preferably The length of the HH bond of H2 molecules at the five adsorption sites is stretched to varying degrees after adsorption. Figure 9 From the geometric structure corresponding to number (a), the distance between H2 molecule and O on the substrate surface is 1s and O 2s The distances are and The geometrical framework of SnO2 has not changed significantly. According to the Mulliken charge analysis, SnO2 acts as an electron acceptor and H2 molecules act as electron donors. 1-H2 / SnO2 (in this structure, the adsorption site of H2 is the top position of the Sn atom on the SnO2 surface) has the highest adsorption energy E ads =-0.580eV, and also has the highest charge transfer capacity Q Tra=0.033e, and the adsorption performance and electronic behavior of 1-H2 / SnO2 will be used for comparison with the modified SnO2 in the subsequent comparison.

[0099] like Figure 10 The four adsorption sites of H2 on SnS@SnO2 are shown as 1-H2 / SnS@SnO2~4-H2 / SnS@SnO2, respectively. Figure 10 The numbers (a) to (d) correspond to the four adsorption sites. Among these four adsorption sites, H2 is set at the T position (top position) and B position (bridge position) of SnS in a vertical or parallel posture. The initial adsorption distance is set to More preferably After adsorption, SnS@SnO2 and H2 both deformed to varying degrees. Among them, the HH bond of 2-H2 / SnS@SnO2 (in this structure, the adsorption site of H2 is horizontally positioned at the B position of the Sn-S bond) was stretched to the maximum length. At the same time, it has the largest adsorption energy (-0.813eV), while 1-H2 / SnS@SnO2 (in this structure, H2 is set at the B position of the Sn-S bond in a vertical posture) has the smallest adsorption distance The maximum charge transfer capacity (0.182e) was achieved, but the deformation of the substrate was large, indicating that the structure could not be stable for a long time. Therefore, considering the adsorption energy, charge transfer capacity, and stability of the adsorption system, 2-H2 / SnS@SnO2 was finally selected for subsequent adsorption performance and electronic property analysis.

[0100] exist Figure 11 In the 2-H2 / SnS@SnO2 composite structure model, the Sn-S bond is changed from the original Stretch to It can be observed that the geometric configuration of H2 molecules is more inclined to Sn atoms. This is because Sn 2+ Sn has stronger chemical activity 2+ The stronger interaction with the H2 molecule results in a high degree of orbital hybridization between the 1s orbital of the H atom and the 4d and 4p orbitals of the Sn atom, which in turn results in the highest adsorption energy and a higher charge transfer amount. Compared to the intrinsic H2 / SnO2 adsorption system, the adsorption energy increases by 1.402 times, and the charge transfer amount increases by 5.424 times. This significant increase in charge transfer is due to the fact that SnS intervenes in the adsorption process and can act as a strong electron acceptor to receive electrons from the H2 molecule. However, due to the small number of extranuclear electrons in a single H2 molecule, the total charge transfer amount remains small. In summary, the homologous sulfide SnS can reliably modify SnO2 and effectively improve the adsorption properties of SnO2-based hydrogen sensors.

[0101] like Figure 12 The DOS energy distribution diagram (i.e., density of states diagram) of the H2 / SnO2 and H2 / SnS@SnO2 adsorption systems is shown. It can be seen that in the H2 / SnS@SnO2 adsorption system, the doping of SnS causes the energy of the adsorption system to be rearranged near the Fermi level. The energy characteristic peaks of -1.7eV, -3.4eV, 2.0eV, and 3.3eV near the Fermi level are further increased. At the same time, the energy distribution of the DOS curve also shifts slightly to the right, which is all due to the activation effect of SnS as a metal sulfide homologous to SnO2. The large electronic state near the Fermi level leads to strong hybridization between the 1s orbital of the H2 molecule and the Sn-4d and Sn-4p orbitals, thereby promoting the charge transfer between the H2 molecule and SnS@SnO2, which is also the main reason for the continuous increase in the metal abundance of the system.

[0102] In order to further explore the effect of H2 adsorption on the electronic properties of the doped structure, Figure 13 The PDOS of the H2 / SnO2 and H2 / SnS@SnO2 adsorption systems are shown. It can be seen that compared to the H2 / SnO2 adsorption system, the energy peaks of SnS@SnO2 at locations far from the Fermi level (e.g., near -18 eV) are reduced, while the characteristic peaks near the Fermi level are significantly increased. The peaks of Sn-4d, H-1s, Sn-5p, S-2p, and O-2p at -3.7 eV overlap significantly, indicating significant hybridization between H2 and the molecular orbitals of SnS@SnO2, resulting in a large adsorption energy (-0.813 eV). Notably, a new energy characteristic peak with a large amplitude appears near the Fermi level (-0.1 eV) in the H2 / SnS@SnO2 adsorption system. A similar phenomenon occurs near 0.9 eV, but the energy distribution of the adsorption system at this energy level is relatively low, but the peak overlap is high. This suggests that H2 adsorption directly affects the changes in the conductivity and adsorption energy of the system.

[0103] like Figure 14 The five adsorption sites of intrinsic SnO2 molecules for C2H2 are shown as 1-C2H2 / SnO2 to 5-C2H2 / SnO2, corresponding to Figure 14 In the five adsorption sites, C2H2 molecules are placed on the O layer of SnO2 molecules in horizontal and vertical positions. 1s The top (T), bridge (B) and hole (V) positions of the atoms in the intrinsic SnO2 surface layer have changed. The C2H2 molecule is more inclined to form a horizontal and slightly tilted posture on the O 1s and O 2sThe B site is adsorbed on the SnO2 surface. The CC bond in 4-C2H2 / SnO2 is stretched to the maximum extent. This is because the C2H2 molecular configuration with the V-position vertical posture as the initial adsorption position is easier to exchange electrons with SnO2, and thus has a higher adsorption energy and a more obvious adsorption effect. In the subsequent comparison of adsorption performance and electronic properties, 3-C2H2 / SnO2 will be used as a control for comparative analysis. It can be seen that after the intrinsic SnO2 completes the adsorption of the C2H2 molecule, the length of the substrate chemical bond does not change significantly, and there is a small interaction between the C2H2 molecule and SnO2. Therefore, it is crucial to modify SnO2 (i.e., doping SnS molecules) to improve its adsorption properties for C2H2 molecules.

[0104] like Figure 15 The four adsorption sites of SnS@SnO2 for C2H2 are shown, which are denoted as 1-C2H2 / SnS@SnO2 to 4-C2H2 / SnS@SnO2, corresponding to Figure 15 In these four adsorption sites, C2H2 molecules are placed at the T and B positions of SnS in a vertical or parallel posture, and the initial adsorption distance is set to Preferably Similar to the H2 adsorption system, SnS@SnO2 and C2H2 both experienced different degrees of deformation after adsorption. 3-C2H2 / SnS@SnO2 (in this structure, C2H2 is placed vertically at the B position of the Sn-S bond in the SnS molecule) has the smallest adsorption distance. The maximum charge transfer capacity (0.518e) and higher adsorption energy (-1.340eV) indicate that C2H2 can act as a good electron donor to transport electrons to the substrate during the adsorption process. The C-C bond of 2-C2H2 / SnS@SnO2 is stretched to the maximum length. While it possesses the highest adsorption energy (-1.403 eV), the deformation of the gas molecules and substrate at the end of the adsorption process is too large to be considered a suitable configuration for gas-sensitive materials. Therefore, in the subsequent discussion of adsorption and electronic properties, 3-C2H2 / SnS@SnO2 will be used for analysis.

[0105] like Figure 16 The figure shows the geometrically optimized 3-C2H2 / SnS@SnO2 composite structure model. Different from the H2 / SnS@SnO2 adsorption system, C2H2 tends to react with S 2- The combination of H2 and Sn 2+ This is due to the difference in metallicity and electronegativity between different atoms. After adsorption, the length of the Sn-S bond is reduced from the original becomes The adsorption of C2H2 does not significantly affect the geometric configuration of SnS@SnO2, and the bond lengths show less change than in the H2 / SnS@SnO2 system. Results show that the adsorption energy of the 3-C2H2 / SnS@SnO2 composite is -1.403 eV, and the charge transfer capacity is 0.518 eV. These are 1.372 times the adsorption energy (-1.023 eV) and 1.497 times the charge transfer capacity (0.346 e) of the intrinsic C2H2 / SnO2 system. SnS doping effectively enhances the adsorption properties of SnO2. Considering the adsorption configuration, adsorption energy, and charge transfer capacity, calculations indicate that SnS@SnO2 exhibits superior adsorption performance for C2H2 over H2.

[0106] Figure 17 The DOS energy distribution diagrams (i.e., density of states diagrams) of C2H2 / SnO2 and C2H2 / SnS@SnO2 are shown. It can be seen from the figure that after SnS@SnO2 completes the adsorption of C2H2, the DOS curve shifts significantly to the right compared to the C2H2 / SnO2 system. This is because the strong interaction between SnS and SnO2 causes the energy of each energy level of the doped structure to be rearranged. A similar situation also occurs near -13.3eV. The new characteristic peak energy is due to the high degree of hybridization of the molecular orbitals of C2H2 molecules and SnS@SnO2. In addition, in the C2H2 / SnS@SnO2 adsorption system, the energy peak near -0.68eV is further enhanced, which means that the chemically active SnS after adsorption keeps the energy near the Fermi level of the doped system at a high level.

[0107] Figure 18 Shown are the PDOS energy distribution diagrams (i.e., local density of states diagrams) of C2H2 / SnO2 and C2H2 / SnS@SnO2. Due to the activation effect of SnS molecules, a clear peak waveform can be observed on the right side of the Fermi level before and after doping, moving toward the side close to the Fermi level. During the adsorption process, electrons can jump more from the top of the valence band to the bottom of the conduction band, proving that SnS molecules can promote the adsorption process, which is consistent with the aforementioned conclusion that SnS can promote the adsorption of C2H2 by SnO2. In the C2H2 / SnS@SnO2 system, the peaks of the five orbitals Sn-5p, O-2p, Sn-4d, S-2p, and C-2p can be observed to overlap at the Fermi level, proving that the molecular orbitals between C2H2 and SnS@SnO2 are highly hybridized. There are many overlaps of orbital characteristic peaks and enhancement of peak energy near -1.47eV and 1.75eV on both sides of the Fermi level, which further illustrates the strong interaction between the two.

[0108] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0109] 1. Intrinsic SnO2 with a rutile tetragonal structure with the (110) crystal plane as the characteristic plane is used. Its band structure has good continuity and is a good direct band gap semiconductor, which is easy to modify and adsorb. By doping the homologous sulfide SnS at the top or hole positions of the surface atoms of the SnO2 supercell or the bridge positions of the chemical bonds between the surface atoms, especially doping at the top positions of the Sn atoms on the surface of the SnO2 supercell, the doping performance can be stabilized, thereby effectively improving the adsorption performance and electronic properties of the SnO2-based gas sensor. The charge transfer amount of the SnO2-based gas sensor during the doping and adsorption process is further improved, the state density distribution is optimized, the work function is improved, and the gas sensing performance of H2 and C2H2 is enhanced, thereby improving the detection capability of early partial discharge.

[0110] 2. Based on first-principles calculations, a geometrically optimized intrinsic SnO2 supercell model, geometrically optimized free-state models of H2 and C2H2 molecules, and a geometrically optimized free-state SnS single-molecule model for doping were established. Furthermore, a SnS-modified SnO2 composite doping model and adsorption site models for H2 and C2H2 molecules were constructed. The adsorption performance and electronic behavior of the SnS-modified SnO2 gas sensor for H2 and C2H2 were analyzed by combining state density, charge transfer, adsorption energy, doping energy, band structure, and work function, thereby determining the sensing performance of the SnS-modified SnO2 gas sensor. This approach allows highly accurate simulation data to be obtained through simulation alone, without consuming extensive human and material resources. This provides important guidance and technical support for improving gas sensor performance and significantly reduces experimental costs.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A gas sensor for early partial discharge detection of low-oil equipment, characterized by: include: A SnS-modified SnO2 composite structure comprises a SnO2 supercell and SnS molecules doped into the SnO2 supercell.

2. The gas sensor for early partial discharge detection of low-oil equipment according to claim 1 is characterized in that: The SnO2 supercell is a rutile tetragonal structure with the (110) crystal plane as a characteristic plane.

3. The gas sensor for early partial discharge detection of low-oil equipment according to claim 1 is characterized in that: In the SnS-modified SnO2 composite structure, the SnS molecules are doped in a horizontal posture at the top sites or holes of the surface atoms of the SnO2 supercell or at the bridge sites of the chemical bonds between the surface atoms.

4. A method for simulating the sensing performance of a gas sensor for early partial discharge detection in low-oil equipment according to any one of claims 1 to 3, characterized in that: The steps include: Establish a geometry-optimized intrinsic SnO2 supercell model, geometry-optimized free-state models of H2 and C2H2 molecules, and geometry-optimized free-state SnS single-molecule model for doping. The SnS-modified SnO2 composite doping model was constructed using the geometrically optimized intrinsic SnO2 supercell model and the geometrically optimized free SnS single molecule model for doping. Using the SnS-modified SnO2 composite doping model and the geometrically optimized free state models of H2 and C2H2 molecules, the adsorption site models of H2 and C2H2 molecules were constructed respectively. Combined with the state density, charge transfer amount, adsorption energy, doping energy, band structure and work function, the adsorption performance and electronic behavior characteristics of the SnO2 gas sensor for H2 and C2H2 were analyzed, thereby determining the sensing performance of the SnO2 gas sensor.

5. The sensing performance simulation method according to claim 4, characterized in that: The step of establishing the geometrically optimized intrinsic SnO2 supercell model comprises: The periodic boundary model is used to construct an intrinsic SnO2 supercell containing 27 Sn atoms and 54 O atoms. The crystal plane of the intrinsic SnO2 supercell is (110) and the size of the vacuum plane layer is The height of the vacuum plane layer is The intrinsic supercell model is geometrically optimized, including: The generalized gradient approximation method and PBE function are used to describe the electron exchange correlation in the intrinsic SnO2 supercell, and the iterative convergence of the electron self-consistent field is performed based on the electron exchange correlation; wherein the convergence accuracy of the electron self-consistent field is set to The van der Waals forces and long-range interactions in the intrinsic SnO2 supercell are treated using a dual numerical plus polarization basis set and the Grimme method. During the treatment, the convergence accuracy of the maximum stress and displacement is set to and The DFT functional semi-core pseudopotential is used to eliminate the nuclear relativistic effect of metal atoms in the intrinsic SnO2 supercell; in the calculations related to the DFT functional semi-core pseudopotential, the Brillouin k-point is set to 4×4×1.

6. The sensing performance simulation method according to claim 4, characterized in that: In the intrinsic SnO2 supercell model after geometry optimization, the bandwidth is 0.888eV, and the bond lengths between the surface Sn atoms and the three nearest O atoms are and In the free state model of the H2 molecule after geometry optimization, the HH bond length is In the free-state model of the C2H2 molecule after geometry optimization, the CC and CH bond lengths are and In the geometry-optimized free SnS single-molecule model for doping, the Sn-S bond length is 7. The sensing performance simulation method according to claim 4, characterized in that: In the SnS-modified SnO2 molecular layer model: the initial doping distance of the SnS molecule is set to SnS molecules are doped in a horizontal posture at the top positions or holes of the surface atoms of the SnO2 supercell or at the bridge positions of the chemical bonds between the surface atoms.

8. The sensing performance simulation method according to claim 7, characterized in that: In the SnS-modified SnO2 molecular layer model, when the SnS molecules are doped horizontally at the top positions of the Sn atoms in the surface layer of the SnO2 supercell, the Sn-S bonds in the doped SnS molecules are The S atoms in the doped SnS and the two nearest O atoms in the surface layer of the SnO2 supercell 1s and O 3s The bond lengths between and The S atoms in the doped SnS and the two nearest Sn atoms in the surface layer of the SnO2 supercell 1s and Sn 2s The bond lengths between and The Sn atoms in the doped SnS and the nearest O atoms in the SnO2 surface layer 2s The bond length between 9. The sensing performance simulation method according to claim 4, characterized in that: In the adsorption site model of H2 molecules: the initial adsorption distance of H2 molecules is set to The H2 molecule is arranged at the top position or bridge position of the Sn-S bond in the SnS molecule in a vertical or parallel posture.

10. The sensing performance simulation method according to claim 4, characterized in that: In the adsorption site model of C2H2 molecules: the initial adsorption distance of C2H2 molecules is set to The C2H2 molecules are arranged at the top, bridge and hole positions of the O atoms on the surface of the SnO2 supercell in a horizontal or vertical posture.

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