Evaluation Method for Detection of Formaldehyde and Vinyl Chloride by Ni-doped Modified Hafnium Sulfide Selenide Sensor

Abstract

The present invention relates to an evaluation method for detecting formaldehyde and vinyl chloride by a nickel-doped modified hafnium sulfide selenide sensor, which optimizes the molecules of formaldehyde and vinyl chloride; determines a stable doping structure, calculates the charge transfer value of the stable nickel-doped structure; calculates the adsorption energy of the stable doping structure on formaldehyde and vinyl chloride; draws an energy band structure diagram, an atomic state density diagram, and a work function diagram after the stable doping structure adsorbs formaldehyde and vinyl chloride; calculates the sensing response and recovery performance of the stable doping structure when adsorbing formaldehyde and vinyl chloride, and evaluates the effect of the nickel-doped modified hafnium sulfide selenide sensor on detecting formaldehyde and vinyl chloride. The present invention can accurately and effectively simulate the ability and response characteristics of the nickel-doped modified hafnium sulfide selenide sensor to detect formaldehyde and vinyl chloride, thereby facilitating the accurate grasp of the characteristics of the nickel-doped modified hafnium sulfide selenide sensor, and facilitating the accurate characterization of the thermal dynamic characteristics of the dry-type reactor when subsequently monitoring formaldehyde and vinyl chloride.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical materials, in particular to an evaluation method for detecting formaldehyde and vinyl chloride by a nickel-doped modified hafnium sulfide selenide sensor. Background Art

[0002] Dry-type reactors are key equipment in power systems. They are used for current limiting in series circuits and for reactive power compensation in parallel circuits. In such devices, epoxy resin is used as the insulating medium to avoid possible insulation defects such as local discharge and local overheating, ensuring the safe operation of dry-type reactors. At the same time, epichlorohydrin (ECH) is also added to the epoxy resin to prevent resin combustion accidents. However, dry-type reactors that have been running for a long time will inevitably have local insulation defects, causing the internal temperature to rise, causing the epoxy resin to decompose into various gases. Specifically, the decomposition products of epichlorohydrin are formaldehyde and vinyl chloride. These toxic gases will diffuse from the reactor into the environment, causing harm to operation and maintenance personnel. Therefore, detecting formaldehyde and vinyl chloride is an ideal way to evaluate the insulation stability of epoxy resin inside dry-type reactors, and can ensure the good operation of dry-type reactors and safe working conditions for maintenance personnel.

[0003] In recent years, the research and development of new sensing materials based on two-dimensional materials has been a hot topic in the field of gas detection. Specifically, transition metal dichalcogenides (TMDs) have been widely used in gas sensing technology research due to their large surface area and strong chemical reaction when interacting with gases. It has been proven that TMDs have ideal semiconductor behavior and adjustable electronic properties similar to graphene. For example, the monolayer of the two-dimensional material MX2 (M = Hf and Mo, X = S, Se and Te) has been confirmed theoretically and experimentally to have good gas molecule adsorption and sensing performance. The gas-sensitive detection accuracy of this two-dimensional material can be further enhanced by surface doping modification. With the discovery of molybdenum sulfide selenide, tungsten sulfide selenide and hafnium sulfide selenide monolayers, there have been certain theoretical calculations on their structures and electronic properties. The sensing properties of molybdenum sulfide selenide and tungsten sulfide selenide monolayers for toxic gases have also been reported in many reports, but the sensing properties of hafnium sulfide selenide monolayers have not been systematically studied. Given the highly controllable electronic properties of HfSSe monolayers, it can be expected that HfSSe monolayers, especially their metal dopants, will have good sensing properties for gases.

[0004] Density Functional Theory (DFT) is the most popular first principle in quantum chemistry and computational chemistry. The theory itself is based on the basic equation of quantum mechanics, the Schrödinger equation. Due to its superiority in computational effort and computational accuracy, density functional theory has practical application value in the field of computational simulation, is widely used and has a long history, and can be used for gas adsorption research. However, there is no evaluation method combining these two situations in the prior art. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and propose an evaluation method for detecting formaldehyde and vinyl chloride by a nickel-doped modified hafnium sulfide selenide sensor, which can improve the sensitivity and accuracy of detecting characteristic gases of overheating faults of power equipment such as dry-type reactors and dry-type transformers, comprehensively evaluate the operating status of the equipment, and has significant practical value and broad application prospects.

[0006] The present invention solves the technical problem by adopting the following technical solutions:

[0007] The evaluation method of nickel-doped modified hafnium sulfide selenide sensor for detecting formaldehyde and vinyl chloride comprises the following steps:

[0008] Step 1: construct an optimization process to optimize the molecular structures of formaldehyde and vinyl chloride to obtain a stable molecular model;

[0009] Step 2, determining a stable doping structure in hafnium sulfide selenide Ni-HfSSe based on doping formation energy, and calculating a charge transfer value of the stable nickel doping structure;

[0010] Step 3, calculating the adsorption energy of the stable doping structure to formaldehyde and vinyl chloride;

[0011] Step 4, drawing the energy band structure diagram, atomic state density diagram and work function diagram of the stable doping structure after adsorbing formaldehyde and vinyl chloride;

[0012] Step 5: Calculate the sensing response and recovery performance of the stable doping structure when adsorbing formaldehyde and vinyl chloride, and combine with step 4 to evaluate the effect of the nickel-doped modified hafnium sulfide selenide sensor in detecting formaldehyde and vinyl chloride.

[0013] Moreover, the optimization process in step 1 is: using Materials Studio software to draw the molecular structure, and based on the DMol of Materials Studio software 3 The module constructs and executes density functional theory, and selects Perdew-Burke-Ernzerhof and generalized gradient approximation functions to optimize the molecular structure to obtain a stable molecular model.

[0014] Furthermore, the step 2 comprises the following steps:

[0015] Step 2.1. Calculate the doping formation energy E of nickel-doped hafnium sulfide selenide form :

[0016] E form =E Ni-HfSSe -E HfSSe -E Ni +μ sub

[0017] E Ni-HfSSe 、E HfSSe and E Ni represent the energies of Ni-HfSSe monolayer, isolated HfSSe monolayer and Ni atom, μ sub The chemical potential of the replaced atom;

[0018] Step 2.2, ranking the doping formation energies of the various hafnium sulfide selenide structures, and taking the doped hafnium sulfide selenide structure with the smallest doping performance as a stable doping structure;

[0019] Step 2.3: Use the Hirshfeld method to calculate the charge transfer value when the stable doping structure adsorbs formaldehyde and vinyl chloride.

[0020] Furthermore, the step 3 comprises the following steps:

[0021] Step 3.1, placing formaldehyde and vinyl chloride close to the surface of the doped structure stabilized in step 2 in different postures, and continuing to optimize the molecules of the hafnium sulfide selenide doped structure that adsorbs formaldehyde and vinyl chloride according to step 1;

[0022] Step 3.2: Use DMol in Materials Studio software 3 The module calculates the energy and electron transfer amount of formaldehyde and vinyl chloride by the optimized doping structure;

[0023] Step 3.3, calculate the adsorption energy of formaldehyde and vinyl chloride by the stable doping structure:

[0024] E ab =E tot (ab) - E tot (molecule)-E tot (Ni-HfSSe)

[0025] E ab 、E tot (ab), E tot (molecule) and E tot(Ni-HfSSe) represent the adsorption energy, the total energy of the doped structure after adsorption of molecules, the total molecular energy of the adsorbed gas, and the energy of the hafnium sulfide selenide unit cell after doping with nickel atoms, respectively.

[0026] Furthermore, the step 5 comprises the following steps:

[0027] Step 5.1, calculate the sensor response S:

[0028] S=(σ gas -1 -σ pure -1 ) / σ pure -1

[0029] σ=λ·e (-Bg / 2KBT)

[0030] Among them, σ gas is the resistance value of Ni-HfSSe after adsorbing formaldehyde or vinyl chloride, σ pure is the resistance value of Ni-HfSSe, σ is the resistance value, λ is a constant, Bg is the band gap width, KB is the Boltzmann constant, and T is the temperature;

[0031] Step 5.2: Calculate the recovery performance τ:

[0032] τ=A -1 e (-Eab / KBT)

[0033] Where A is the frequency, E ab is the adsorption energy;

[0034] Step 5.3: Evaluate the feasibility of nickel-doped modified hafnium sulfide selenide sensor for detecting formaldehyde and vinyl chloride by using the sensing response S, recovery performance τ and combining the energy band structure diagram, atomic state density diagram and work function diagram drawn in step 4.

[0035] The advantages and positive effects of the present invention are:

[0036] 1. The present invention optimizes the molecules of formaldehyde and vinyl chloride; determines a stable doping structure, calculates the charge transfer value of a stable nickel doping structure; calculates the adsorption energy of the stable doping structure on formaldehyde and vinyl chloride; draws the energy band structure diagram, atomic state density diagram and work function diagram after the stable doping structure adsorbs formaldehyde and vinyl chloride; calculates the sensing response and recovery performance of the stable doping structure when adsorbing formaldehyde and vinyl chloride, and evaluates the effect of the nickel doped modified hafnium sulfide selenide sensor on detecting formaldehyde and vinyl chloride. The present invention can accurately and effectively simulate the ability and response characteristics of the nickel doped modified hafnium sulfide selenide sensor to detect formaldehyde and vinyl chloride, thereby facilitating the accurate grasp of the characteristics of the nickel doped modified hafnium sulfide selenide sensor, and facilitating the subsequent monitoring of formaldehyde and vinyl chloride, and accurately characterizing the thermal dynamic characteristics of the dry reactor.

[0037] 2. Based on density functional theory, the present invention comprehensively studies the gas adsorption and sensing characteristics of formaldehyde and vinyl chloride by nickel-doped modified hafnium sulfide selenide (Ni-HfSSe) monolayer, and proposes a new method for developing Ni-HfSSe sensors to detect characteristic gases of reactor failure. The present invention selects nickel as a dopant because it has good catalytic properties and strong chemical reactivity in gas adsorption systems, and embeds hafnium sulfide selenide monolayers by replacing sulfur or selenium atoms to establish Ni-HfSSe monolayers. The present invention can lay a theoretical foundation for further exploring gas sensors based on hafnium sulfide selenide with high sensitivity and good electrical response. DETAILED DESCRIPTION

[0038] The present invention is further described below.

[0039] The present invention simulates and analyzes the adsorption behavior of formaldehyde and vinyl chloride on nickel-doped modified hafnium sulfide selenide based on density functional theory. The molecular structures of formaldehyde and vinyl chloride are constructed and optimized in the Materials Studio (MS) platform, and their structures are optimized based on the Perdew-Burke-Ernzerhof (PBE) function and generalized gradient approximation (GGA) in density functional theory, and the energy of each molecule is obtained by energy calculation. The nickel-doped modified hafnium sulfide selenide is also optimized by this method. The optimized gas molecules are placed near the nickel-doped modified hafnium sulfide selenide to simulate the adsorption process. This analysis lays a theoretical foundation for using nickel-doped modified hafnium sulfide selenide for dry reactor status detection.

[0040] The evaluation method of nickel-doped modified hafnium sulfide selenide sensor for detecting formaldehyde and vinyl chloride comprises the following steps:

[0041] Step 1: Construct an optimization process to optimize the molecular structures of formaldehyde and vinyl chloride to obtain a stable molecular model.

[0042] The optimization process is as follows: use Materials Studio software to draw the molecular structure and use the DMol 3 The module constructs and executes density functional theory, and selects Perdew-Burke-Ernzerhof and generalized gradient approximation function (GGA) to optimize the molecular structure to obtain a stable molecular model.

[0043] The parameters selected during the optimization process are: energy convergence accuracy is 1×10 -5 Ha, the maximum stress is 2× The maximum displacement is 5× DMol 3 In the module's Calculation, in the "Setup" tab, select the highest option for optimizing accuracy / quality (Quality): "Fine", and change "Task" to "Geometry Optimization". The self-consistent field tolerance is 1×10 -6 , set the DIIS size to 6 to speed up SCF convergence.

[0044] The optimization option is set to: DMol 3 In the Calculation of the module, in the "Properties" sub-option page, check the four options "Density ofstates", "Electron density", "Electrostatics", and "Populationanalysis".

[0045] Step 2: Determine the stable doping structure in hafnium sulfide selenide Ni-HfSSe based on the doping formation energy, and calculate the charge transfer value of the stable nickel doping structure.

[0046] Step 2.1. Calculate the doping formation energy E of nickel-doped hafnium sulfide selenide form :

[0047] E form =E Ni-HfSSe -E HfSSe -E Ni +μ sub

[0048] E Ni-HfSSe 、E HfSSe and E Ni represent the energies of Ni-HfSSe monolayer, isolated HfSSe monolayer and Ni atom, μ sub The chemical potential of the replaced atom;

[0049] Step 2.2, ranking the doping formation energies of the various hafnium sulfide selenide structures, and taking the doped hafnium sulfide selenide structure with the smallest doping performance as a stable doping structure;

[0050] Step 2.3: Use the Hirshfeld method to calculate the charge transfer value when the stable doping structure adsorbs formaldehyde and vinyl chloride.

[0051] Step 3: Calculate the adsorption energy of the stable doping structure for formaldehyde and vinyl chloride.

[0052] Step 3.1, formaldehyde and vinyl chloride are brought close to the surface of the doped structure stabilized in step 2 in different postures, and the molecules of the hafnium sulfide selenide doped structure that adsorbs formaldehyde and vinyl chloride are continuously optimized according to step 1.

[0053] Step 3.2: Use DMol in Materials Studio software 3 The module calculates the energy and electron transfer amount of formaldehyde and vinyl chloride after the optimized doping structure.

[0054] In this step, the DMol of Materials Studio software 3 The module is set as follows: the energy convergence accuracy is 1×10 -5 Ha, the maximum stress is 2× The maximum displacement is DMol 3 In the Calculation, in the "Setup" sub-option page, optimize the precision / quality (Quality) and select the highest option: "Fine"; in the "Properties" sub-option page, change "Task" to "Energy", and then change the MP K point of the "Electronic" sub-option page to 1×1×1. In the "Properties" sub-option page, only check Orbitals and ensure the HOMO and LUMO of Orbitals.

[0055] Step 3.3, calculate the adsorption energy of formaldehyde and vinyl chloride by the stable doping structure:

[0056] E ab =E tot (ab) - E tot (molecule)-E tot (Ni-HfSSe)

[0057] E ab 、E tot (ab), E tot (molecule) and E tot(Ni-HfSSe) represent the adsorption energy, the total energy of the doped structure after adsorption of molecules, the total molecular energy of the adsorbed gas, and the energy of the hafnium sulfide selenide unit cell after doping with nickel atoms, respectively.

[0058] Step 4: Draw the energy band structure diagram, atomic state density diagram and work function diagram of the stable doping structure after adsorbing formaldehyde and vinyl chloride.

[0059] During the drawing process of this step, the Brillouin zone integration of the charge transfer value in step 2 and the electron transfer amount in step 3 uses a Monkhorst-Pack k-point 10×10×1 grid, and the energy tolerance accuracy, self-consistent cycle energy, and global orbital cutoff radius are defined as 10 -5 Ha, 10 -6 Ha and A 3×3×1HfSSe supercell containing 9 Hf atoms, 9 S atoms, and 9 Se atoms is modeled. The vacuum area is used to avoid the interaction between adjacent cells.

[0060] Step 5: Calculate the sensing response and recovery performance of the stable doping structure when adsorbing formaldehyde and vinyl chloride, and combine with step 4 to evaluate the effect of the nickel-doped modified hafnium sulfide selenide sensor in detecting formaldehyde and vinyl chloride.

[0061] Step 5.1, calculate the sensor response S:

[0062] S=(σ gas -1 -σ pure -1 ) / σ pure -1

[0063] σ=λ·e (-Bg / 2KBT)

[0064] Among them, σ gas is the resistance value of Ni-HfSSe after adsorbing formaldehyde or vinyl chloride, σ pure is the resistance value of Ni-HfSSe, σ is the resistance value, λ is a constant, Bg is the band gap width, KB is the Boltzmann constant, and T is the temperature;

[0065] Step 5.2: Calculate the recovery performance τ:

[0066] τ=A -1 e (-Eab / KBT)

[0067] Where A is the frequency, E ab is the adsorption energy;

[0068] Step 5.3: Evaluate the feasibility of nickel-doped modified hafnium sulfide selenide sensor for detecting formaldehyde and vinyl chloride by using the sensing response S, recovery performance τ and combining the energy band structure diagram, atomic state density diagram and work function diagram drawn in step 4.

[0069] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation manner. Any other implementation manners derived by those skilled in the art based on the technical solution of the present invention also fall within the scope of protection of the present invention.

Claims

1. Evaluation method for detecting formaldehyde and vinyl chloride using nickel-doped modified hafnium sulfide selenide sensor, characterized in that: The following steps are involved: Step 1: construct an optimization process to optimize the molecular structures of formaldehyde and vinyl chloride to obtain a stable molecular model; The optimization process in step 1 is: use Materials Studio software to draw the molecular structure, and based on the DMol 3 The module constructs and executes density functional theory, and selects Perdew-Burke-Ernzerhof and generalized gradient approximation functions to optimize the molecular structure to obtain a stable molecular model; Step 2, determining a stable doping structure in hafnium sulfide selenide Ni-HfSSe based on doping formation energy, and calculating a charge transfer value of the stable nickel doping structure; Step 2 includes the following steps: Step 2.

1. Calculate the doping formation energy E of nickel-doped hafnium sulfide selenide form : AND form =And Ni -HfSSe-E HfSSe -AND Ni +μ sub E Ni-HfSSe 、E HfSSe and E Ni represent the energies of Ni-HfSSe monolayer, isolated HfSSe monolayer and Ni atom, μ sub The chemical potential of the replaced atom; Step 2.2, ranking the doping formation energies of the various hafnium sulfide selenide structures, and taking the doped hafnium sulfide selenide structure with the smallest doping performance as a stable doping structure; Step 2.3, using the Hirshfeld method to calculate the charge transfer value when the stable doping structure adsorbs formaldehyde and vinyl chloride; Step 3, calculating the adsorption energy of the stable doping structure to formaldehyde and vinyl chloride; Step 3 includes the following steps: Step 3.1, placing formaldehyde and vinyl chloride close to the surface of the doped structure stabilized in step 2 in different postures, and continuing to optimize the molecules of the hafnium sulfide selenide doped structure that adsorbs formaldehyde and vinyl chloride according to step 1; Step 3.2: Use DMol in Materials Studio software 3 The module calculates the energy and electron transfer amount of formaldehyde and vinyl chloride by the optimized doping structure; Step 3.3, calculate the adsorption energy of formaldehyde and vinyl chloride by the stable doping structure: AND ab =And tot (ab)-And tot (molecule)-E tot (Ni-HfSSe) E ab 、E tot (ab), E tot (molecule) and E tot (Ni-HfSSe) represents the adsorption energy, the total energy of the adsorbed molecules in the doping structure, the total energy of the adsorbed gas molecules, and the energy of the unit cell of hafnium sulfide selenide after doping with nickel atoms, respectively; Step 4, drawing the energy band structure diagram, atomic state density diagram and work function diagram of the stable doping structure after adsorbing formaldehyde and vinyl chloride; Step 5, calculating the sensing response and recovery performance of the stable doping structure when adsorbing formaldehyde and vinyl chloride, and combining with step 4 to evaluate the effect of the nickel-doped modified hafnium sulfide selenide sensor in detecting formaldehyde and vinyl chloride; Step 5 includes the following steps: Step 5.1, calculate the sensor response S: S=(σ gas -1 -s pure -1 ) / s pure -1 σ=λ·e (-Bg / 2KBT) Among them, σ gas is the resistance value of Ni-HfSSe after adsorbing formaldehyde or vinyl chloride, σ pure is the resistance value of Ni-HfSSe, σ is the resistance value, λ is a constant, Bg is the band gap width, KB is the Boltzmann constant, and T is the temperature; Step 5.2: Calculate the recovery performance τ: τ=A -1 e (-Eab / KBT) Where A is the frequency, E ab is the adsorption energy; Step 5.3: Evaluate the feasibility of nickel-doped modified hafnium sulfide selenide sensor for detecting formaldehyde and vinyl chloride by using the sensing response S, recovery performance τ and combining the energy band structure diagram, atomic state density diagram and work function diagram drawn in step 4.