Janus GaSge / g-SiC heterostructure design and prediction method and system for photocatalytic water splitting hydrogen production performance

Abstract

The invention belongs to but is not limited to the technical field of photocatalytic water splitting hydrogen production, and discloses a Janus GaSge / g-SiC heterostructure design and a prediction method and system for photocatalytic water splitting hydrogen production performance, bulk phase GaSe is adopted to establish an intrinsic GaSe single-layer structure model, S atoms are utilized to replace a layer of Se atoms, and a GaSSe single-layer structure model is constructed; obtaining a corresponding graphene single-layer structure from the graphite phase structure through a tangent plane, and utilizing Si atoms to replace C atoms to establish a g-SiC single-layer model; the method comprises the following steps: stacking Janus GaSeS, GaSSe and g-SiC, and sequentially constructing a Janus GaSeS / g-SiC heterostructure model according to atomic arrangement. The heterostructure disclosed by the invention shows good structural stability, high interface charge transfer efficiency, high surface activity and higher sunlight utilization rate. And meanwhile, the problem of poor performance in the aspect of light absorption due to the wide band gap characteristic of the g-SiC single layer is relieved.

Description

Technical Field

[0001] The present invention belongs to but is not limited to the technical field of photocatalytic water decomposition to produce hydrogen, and in particular relates to a Janus GaSSe / g-SiC heterostructure design and a prediction method and system for the photocatalytic water decomposition to produce hydrogen performance. Background Art

[0002] With the rapid development of industrialization, energy crisis and environmental pollution have become one of the most serious challenges in the world. Hydrogen energy is considered to be a potential candidate for fossil fuels due to its advantages such as high heat, pollution-free products and easy storage. Photochemical hydrogen production technology that directly uses sunlight for photochemical conversion can be used as the best way to convert and store solar energy. In recent years, the development of photocatalytic technology has expanded the application of solar energy to more fields and achieved considerable results. Among them, semiconductor photocatalytic technology is an ideal way to produce hydrogen. However, photocatalytic hydrogen production technology requires efficient semiconductor photocatalysts to achieve it. For this reason, the development and design of semiconductor photocatalysts has become a hot issue in solving energy and environmental problems. Since the successful exfoliation of graphene, the derivation and development of two-dimensional materials have entered the field of vision of researchers. Compared with three-dimensional materials, two-dimensional materials have shown great potential in the field of photocatalysis due to their unique electronic properties, large specific surface area and excellent mechanical properties. However, photocatalytic water splitting technology still faces many challenges in practical applications. While most semiconductor photocatalysts use Pt to improve the photocatalytic efficiency, they also increase the cost of photocatalytic reactions and cause pollution to the environment. In addition, the reaction kinetics of photocatalytic water splitting are slow, and the absorption and utilization efficiency of sunlight is low, especially in the visible and infrared regions. These problems severely limit the practical application of photocatalytic water splitting. Heterostructure engineering strategies have opened up a path for the preparation of efficient photocatalysts by improving the transfer efficiency of interfacial charges and increasing the number of active sites. In addition, compared with the single-layer materials that make up the heterostructure, the heterostructure has enhanced structural stability and activity due to the synergistic effect of the components, which leads to interfacial charge transfer, the formation of new chemical bonds and the generation of built-in electric fields, and also significantly enhances the absorption capacity of visible light. For this reason, research on heterojunctions based on two-dimensional materials as water splitting photocatalysts is of great significance. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a Janus GaSSe / g-SiC heterostructure design and a prediction method for the photocatalytic water decomposition hydrogen production performance. Based on the first-principles CASTEP module modeling and property calculation under density functional theory (DFT), the geometric structure, interface stability, electronic properties, band edge position and optical properties of the heterojunction and its components are simulated.

[0004] The present invention is implemented in such a way that a method for constructing a Janus GaSSe / g-SiC heterostructure comprises:

[0005] Step 1: Use Material Studio (MS) to import bulk GaSe to establish a Janus GaSe single-layer model, and replace one layer of Se atoms in GaSe with S atoms to construct a Janus GaSSe single-layer model, and then optimize it;

[0006] Step 2: Use MS software to import the graphite phase structure, obtain the initial graphene single layer model through the cleave function, replace half of the C atoms with Si atoms, construct the g-SiC single layer model, and optimize it;

[0007] Step three, construct the Janus GaSeS / g-SiC and Janus GaSSe / g-SiC heterostructure models.

[0008] Further, in step three, The heterojunction is constructed by using Janus GaSSe supercell and 2×2×1 g-SiC model;

[0009] Furthermore, according to the two cases of S terminal and Se terminal, the Janus GaSeS / g-SiC and Janus GaSSe / g-SiC heterostructure models were constructed through the Builder function for structural optimization.

[0010] Furthermore, the single layer and heterostructure models in steps 1, 2 and 3 are optimized with the following specific parameters: the pseudopotential is the ultrasoft pseudopotential (USP), and the exchange correlation potential is the Perdew-Burke-Ernzerhof (PBE) functional in the generalized gradient approximation (GGA). The cutoff energy is set to 400 eV, and the Brillouin zone Monkhorst-Pack k-point grid is 4×4×1. The convergence tolerances for energy and maximum force are 1.0×10 -5 eV / atom and The DFT-D method is introduced to eliminate the long dispersion interaction. Add along the vertical direction The vacuum layer is used to ensure that periodic interactions between adjacent layers are eliminated.

[0011] Another object of the present invention is to provide a method for predicting the performance of Janus GaSSe / g-SiC heterostructure photocatalytic water decomposition to produce hydrogen, comprising the following steps:

[0012] Step 1, performing complete geometric optimization on the single layer and heterostructure models to obtain the lowest energy configuration and geometric parameters, and calculating the cohesive energy, binding energy, phonon spectrum and thermal stability;

[0013] Step 2, calculating the electronic properties based on the single layer and heterostructure model with the lowest energy obtained in step 1, and obtaining the changes in the electronic properties before and after stacking;

[0014] Step three, based on the single layer and heterostructure models at the lowest energy obtained in step one, calculate the light absorption properties and clarify the influence of stacking on the optical properties.

[0015] Step 3, based on the electronic band structure obtained in step 2, the positions of the band edges of the single layer and the heterostructure are obtained;

[0016] Step 4: Based on the electronic band structure obtained in step 2, the changes in the band edge position of the heterostructure under different pH values ​​are calculated to obtain the influence of different pH values ​​on the photocatalytic performance of the heterojunction.

[0017] Furthermore, the specific parameters for calculating the heterostructure properties in steps 1, 2 and 3 are:

[0018] The pseudopotential is an ultrasoft pseudopotential (USP), and the exchange-correlation potential is the Perdew-Burke-Ernzerhof (PBE) functional in the generalized gradient approximation (GGA). The cutoff energy is set to 400 eV, and the Brillouin zone Monkhorst-Pack k-point grid is 4×4×1. The convergence tolerances for energy and maximum force are 1.0×10 -5 eV / atom and The DFT-D method is introduced to eliminate the long dispersion interaction. Add along the vertical direction The vacuum layer is used to ensure that periodic interactions between adjacent layers are eliminated.

[0019] In order to prove the dynamic stability of the structure, the finite displacement method was used to calculate the phonon dispersion. In addition, the Janus GaSeS / g-SiC and Janus GaSSe / g-SiC heterojunction models were simulated using ab initio molecular dynamics (AIMD) to detect their thermodynamic stability. The simulation time was 6ps at room temperature of 300K, with each step time of 1fs, implemented in the Dmol3 module. The finite displacement method was selected for the method; the thermal stability simulation was performed using molecular dynamics in the DMol3 module, the NVT ensemble was selected, the temperature was set to 300K and 500K, respectively, the time step was 1fs and the total time was 6ps.

[0020] The present invention also provides a system of predicted Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructure photocatalyst materials, the system comprising:

[0021] Modeling module: Import bulk GaSe and graphite phase structures through MS software, build GaSSe single layer and g-SiC single layer structure models respectively, and use the Build layer function to realize the construction of Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructures;

[0022] Geometry Optimization Module: Provides full geometry relaxation function, uses BFGS algorithm, PBE functional of generalized gradient approximation and ultrasoft pseudopotential, combines DFT-D method to eliminate long-range dispersion interaction, sets optimization parameters such as plane wave cutoff energy, Brillouin zone k-point grid and vacuum layer thickness, and optimizes single-layer and heterogeneous structure models;

[0023] Performance calculation module: supports phonon spectrum analysis to calculate structural stability, molecular dynamics simulation to calculate thermal stability, and electronic property calculations including electronic energy bands, state density, electronic localization function, differential charge density, and work function;

[0024] Photocatalytic performance prediction module: Based on the optimized minimum energy configuration, the band edge position and light absorption coefficient are calculated to evaluate the photocatalytic water splitting performance of the heterostructure.

[0025] Furthermore, the modeling module supports the construction of multiple supercell forms, including 2×2×1 supercell g-SiC single layer and Supercell GaSSe monolayer to adapt to different atomic arrangement structures; and support automatic adjustment of layer spacing during the stacking process to ensure the configuration stability of the heterostructure.

[0026] Furthermore, the performance calculation module uses the CASTEP module to calculate the phonon spectrum and the finite displacement method to analyze the structural stability. The molecular dynamics simulation uses the DMol3 module, and the temperature conditions of 300K and 500K are set based on the NVT ensemble, with a time step of 1fs and a total duration of 6ps to evaluate the thermal stability of the heterostructure.

[0027] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0028] First, the Janus GaSSe / g-SiC heterostructure described in the present invention is a photocatalyst material for photocatalytic splitting of water, and its advantages are: graphite-like silicon carbide (g-SiC) has characteristics such as high specific surface area and strong mechanical properties. Janus materials obtain significant electronic and optical properties due to breaking the structural symmetry. Janus GaSSe single layer prediction shows that it has high intrinsic electron mobility, high light absorption coefficient, piezoelectric coefficient and mechanical stability. The synergistic effect between Janus GaSSe and g-SiC significantly enhances the structural stability of the heterostructure and improves the interface carrier separation efficiency. At the same time, it helps to enhance visible light absorption and thus obtain a high solar energy to hydrogen efficiency. It shows that the heterostructure can be used as a promising photocatalyst material to solve the problems of structural stability, high carrier recombination rate, low surface activity and low sunlight utilization rate of current two-dimensional material photocatalysts.

[0029] Two-dimensional materials show broad application potential in the field of photocatalysis due to their large specific surface area, rich electronic properties, chemical stability and excellent mechanical properties. However, the reaction kinetics of most semiconductor photocatalysts for water splitting are slow, and the absorption and utilization efficiency of sunlight is low, especially in the visible light and infrared light regions, which seriously limits the application of photocatalytic water splitting in practice. The construction of heterostructures is an effective method to improve the performance of photocatalysts for water splitting and hydrogen production. Therefore, the present invention designs a Janus GaSSe / g-SiC heterostructure photocatalyst material, which is predicted to show good structural stability, high light absorption capacity and interface carrier transfer. At the same time, the problem of insufficient light absorption performance of g-SiC monolayer is solved. The present invention provides a new design idea for the development of high-performance photocatalyst materials, which will have theoretical guiding significance for the application of Janus GaSSe / g-SiC materials in photocatalysis.

[0030] Second, the technical solution of the present invention solves the technical problems that people have been eager to solve but have never been able to solve successfully:

[0031] Most two-dimensional semiconductor photocatalysts often face problems such as low solar energy utilization, high carrier load rate, and low surface reaction activity. The present invention provides a Janus GaSSe / g-SiC heterostructure constructed by a Janus GaSSe monolayer and g-SiC. The design of the component and structural synergistic heterostructure optimizes the structural stability of the catalyst material and effectively improves the solar light utilization, interface carrier transfer efficiency, and catalytic active sites of the photocatalyst material in the field of photocatalysis. The Janus GaSSe / g-SiC heterostructure has a high component richness, which is expected to reduce production costs and improve the sustainability of materials.

[0032] Fourth, the technical solution of the embodiment of the present invention aims to predict the performance of a novel Janus GaSSe / g-SiC heterostructure as a photocatalyst material through the design of a photocatalyst heterostructure and theoretical calculation simulation. Through a detailed and systematic calculation and design process, the present invention not only provides an innovative material design solution, but also verifies the feasibility and superiority of the solution through first-principles calculations.

[0033] The technical solution of the present invention solves the following technical problems and achieves significant technical progress:

[0034] 1) Material design and selection:

[0035] A Janus GaSSe monolayer was selected. This material has significant electronic and optical properties due to breaking the structural symmetry, which is expected to improve the shortcomings of g-SiC materials in light absorption.

[0036] A new type of Janus GaSSe and g-SiC monolayer material was designed and constructed, and its stability was verified by calculating parameters such as cohesive energy.

[0037] 2) Design and construction of heterogeneous structures:

[0038] The Janus GaSSe / g-SiC heterostructure model was innovatively combined with a single layer of g-SiC. This heterostructure synergistic effect brings about unique interface effects, electronic properties, and light absorption properties, which is beneficial to improving the photocatalytic efficiency.

[0039] Through geometric optimization, the stable configuration and interlayer distance of the heterostructure were determined. Combined with the binding energy and phonon spectrum, the kinetic and thermodynamic stability of the heterostructure model was confirmed, providing a reliable model basis for subsequent performance prediction.

[0040] 3) Stability verification:

[0041] Through phonon spectrum calculation and AIMD simulation, the dynamic and thermal stability of monolayer and heterostructures were systematically confirmed. These stability verifications are the key prerequisites for the application of materials in practical photocatalyst materials.

[0042] 4) Analysis of light absorption properties and band edge position:

[0043] The Janus GaSSe, g-SiC monolayer and heterostructure models were constructed, and the light absorption properties and band edge positions of the two components and the heterostructure were calculated to analyze the effects of the heterostructure on the optical properties and band edge arrangement. This is crucial for understanding the application of Janus GaSSe / g-SiC heterostructures in photocatalyst materials.

[0044] 5) Gibbs free energy of photocatalytic water splitting

[0045] Janus GaSSe and g-SiC were selected to construct a heterostructure. Under light conditions, each step of the OER reaction is an exothermic reaction, indicating that the OER can proceed spontaneously. At the same time, the free energy of the OER and HER rate-determining steps of each reaction step is significantly reduced, which improves the redox reaction performance, which will greatly reduce the additional potential required to be applied. The Janus GaSSe / g-SiC heterostructure can obtain greatly enhanced HER and OER driving forces due to the synergistic effect of interface polarization and band gap components, thus demonstrating the application potential of the Janus GaSSe heterostructure in enhancing the photocatalytic redox driving force.

[0046] In summary, the technical solution of the present invention systematically designs and predicts the performance of a new Janus GaSSe / g-SiC heterostructure as a water splitting photocatalyst material through theoretical calculation and simulation. This heterostructure enhances the stability and activity of the structure due to the synergistic effect of the components, thereby leading to interfacial charge transfer, the formation of new chemical bonds and the generation of a built-in electric field, and also significantly enhances the absorption capacity of visible light. It is expected to provide new ideas and methods for the development of high-performance photocatalyst materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a flow chart of the Janus GaSSe / g-SiC heterostructure provided in an embodiment of the present invention for photocatalytic water splitting photocatalyst material design and performance prediction;

[0048] Figure 2 It is a Janus GaSSe and g-SiC single layer model provided by an embodiment of the present invention;

[0049] Figure 3 It is the Janus GaSSe / g-SiC and GaSeS / g-SiC heterojunction structure model provided by the embodiment of the present invention;

[0050] Figure 4 : is an energy band diagram of Janus GaSSe and g-SiC monolayer provided by an embodiment of the present invention;

[0051] Figure 5 is an energy band diagram of two heterostructures provided by an embodiment of the present invention;

[0052] Figure 6 is the differential charge density of the two heterostructures provided by the embodiment of the present invention;

[0053] Figure 7 It is the band edge arrangement of two heterojunctions provided by the embodiment of the present invention;

[0054] Figure 8 It is the light absorption coefficient curve of the single layer and the heterostructure provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0056] The present invention significantly simplifies the modeling process of Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructures through multiple supercell forms and automatic interlayer adjustment functions. The BFGS algorithm combined with the DFT-D method not only improves the accuracy of geometric optimization, but also greatly shortens the optimization time, ensuring that the generated structure has high stability. This automated modeling and optimization technology effectively solves the problems of complex modeling and time-consuming optimization in the prior art.

[0057] The system uses a high-precision DFT method to calculate the band edge position and light absorption coefficient, and comprehensively evaluates the applicability of heterostructures in photocatalytic water splitting. Compared with traditional methods, this invention improves the prediction accuracy of photocatalytic performance through spectral simulation and electronic property analysis, providing a scientific basis for the development of efficient photocatalysts. This progress significantly optimizes the reliability and efficiency of photocatalytic material design.

[0058] Through molecular dynamics simulation and phonon spectrum analysis, the present invention verifies the thermal and structural stability of Janus heterostructures at 300K and 500K. System simulation shows that the material can still maintain excellent structural properties under high temperature environment and meet the application requirements under various industrial conditions. This comprehensive analysis of stability fills the gap in the existing technology in the prediction of high temperature adaptability.

[0059] The Janus heterostructure designed in the present invention has excellent photocatalytic performance, thermal stability and cost advantages, and is suitable for clean energy preparation (such as photocatalytic water decomposition to produce hydrogen), wastewater treatment, environmental governance and other fields. Automated modeling and optimization technology reduces R&D costs and cycles, provides strong support for the large-scale industrial application of photocatalytic materials, and promotes the industrialization of clean energy and environmental material technologies. The system's modeling module imports bulk GaSe and graphite phase structures through MS software, and constructs structural models of GaSSe monolayer and g-SiC monolayer, respectively. The system supports users to directly define the stacking method and arrangement order between layers in the interface. To adapt to different atomic arrangements, the modeling module provides support for a variety of supercells, such as 2×2×1 supercells of g-SiC and The system automatically adjusts the interlayer spacing during the stacking process to optimize the stability of the initial configuration, thus forming Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructures.

[0060] The geometry optimization module uses density functional theory (DFT) combined with the PBE functional of the generalized gradient approximation to ensure the accuracy of energy calculations. During the optimization process, the BFGS algorithm is used to achieve complete geometric relaxation. By setting the plane wave cutoff energy and the resolution of the Brillouin zone k-point grid, the atomic positions and interlayer spacing of the monolayer and heterostructures are optimized. In addition, the system combines the DFT-D method to eliminate long-range dispersion interactions to ensure the accuracy of the simulation results under the consideration of van der Waals effects. To avoid interlayer coupling, the vacuum layer thickness is set to To reduce periodic interference between structures.

[0061] The performance calculation module uses CASTEP and DMol3 for multi-dimensional analysis. The phonon spectrum calculation uses the finite displacement method to analyze the structural stability of the Janus heterostructure. The molecular dynamics simulation is based on the NVT ensemble. At 300K and 500K, the time step is set to 1fs and the total time is 6ps to evaluate the thermal stability. The electronic property calculation includes the band structure, state density, electron localization function (ELF), differential charge density distribution, and work function, which reveals the electronic behavior and carrier distribution characteristics of the heterostructure and provides basic data for the subsequent photocatalytic performance prediction.

[0062] After completing the geometry optimization and performance calculation, the photocatalytic performance prediction module evaluates the photocatalytic water splitting performance of the heterostructure by calculating the band edge position and light absorption coefficient. The system first calculates the conduction band minimum (CBM) and valence band maximum (VBM) of the lowest energy configuration, and compares them with the water redox potential to determine its applicability for photocatalytic water splitting. In addition, through the simulation of the absorption spectrum, the light absorption range and absorption intensity are analyzed to confirm the catalytic efficiency of the heterostructure in the visible and ultraviolet light regions. Combined with the prediction results, a performance evaluation report is provided to provide guidance for subsequent experimental preparation.

[0063] like Figure 1 As shown, the embodiment of the present invention provides a design and performance prediction of a Janus GaSSe / g-SiC heterostructure photocatalyst material; the first principle calculation based on the density functional theory framework is used to simulate the changes in characteristic parameters, total energy, electronic properties, band edge position and light absorption performance of a single layer and a Janus GaSSe / g-SiC heterostructure. Specifically, the following steps are included:

[0064] S101, Janus GaSSe single layer model construction:

[0065] (1) Import the bulk structure of GaSe from the Material studio software, optimize the cell structure to obtain a stable configuration, obtain the GaSe unit cell structure through the Cleave Surface function, and then replace a layer of Se atoms with S atoms to obtain the GaSSe single layer model, such as Figure 2 As shown;

[0066] (2) Perform structural relaxation on the GaSe single-cell monolayer obtained in (1) to obtain the lattice parameters of the single-cell graphene: Key length and

[0067] S102, g-SiC single layer model construction:

[0068] (1) Use Material Studio software to import graphite unit cells, optimize the geometry, and obtain the graphene unit cell model by cutting. Replace one of the C atoms with a Si atom to obtain a g-SiC single layer, as shown in Figure 2 As shown;

[0069] (2) The geometric optimization of the g-SiC monolayer structure is performed to obtain the lattice constant of the unit cell. and

[0070] S103, single-layer structure stability calculation:

[0071] The above configuration is geometrically optimized, and the corresponding cohesive energy of Janus GaSSe and g-SiC monolayer is calculated as follows:

[0072] E coh =(E GaSSe / g-SiC -aE Ga / Si -bE S / c -cE Se ) / (a+b+c)

[0073] Among them, E GaSSe / g-SiC is the total energy of GaSSe / g-SiC, E Ga / Si 、E S / c and E Se are the total energies of single Ga, Si, S, C and Se atoms respectively; a, b, c and d are the numbers of corresponding atoms respectively.

[0074] According to the above definition, the cohesive energies of the corresponding monolayers are -16.12 eV and -3.10 eV, respectively. Both cohesive energies are negative, indicating that the two monolayers are energetically stable.

[0075] S104, heterojunction model construction;

[0076] In order to keep the lattice adaptation rate within a reasonable range (5%), the structure described in S101 is adopted. The heterostructure model of the supercell GaSSe monolayer and the 2×2×1 supercell g-SiC monolayer in the structure described in S102 is as follows Figure 3 As shown, the obtained adaptation rate was 0.07%.

[0077] The geometric optimization of the heterojunction model is performed to obtain the corresponding interlayer distances of the stable system. and

[0078] S105, calculation of heterojunction structure stability;

[0079] (1) For the optimized stable heterostructure in S104, the binding energy is calculated as follows:

[0080] E b =E GaSSe / g-SiC -E GaSSe -E g-Sic

[0081] Among them, E GaSSE / g-SiC 、E GaSSE and E g-SiC The total energies of GaSSe / g-SiC, GaSSe and g-SiC are obtained respectively. The binding energies of the two heterostructures are -9.92 meV and -8.00 meV, respectively. Both binding energies are negative, indicating that the constructed two heterostructures are energy stable.

[0082] (2) The phonon spectrum curves were calculated for the dynamic stability of the optimized stable configurations in S101, S102, and S104. The phonon curves had no imaginary frequency, indicating that the monolayer and heterostructures were stable.

[0083] (3) Aiming at the thermal stability of the optimized stable configurations in S101, S102, and S104, AIMD simulations were performed at 300 K and 500 K. The energy fluctuations were very small and the structures maintained small deformations, further confirming the thermal stability of the system.

[0084] S106, calculation of electronic properties of monolayers and heterostructures;

[0085] (1) Based on the most stable model of Janus GaSSe, g-SiC and heterostructure obtained by S101, S102 and S104, the band structure calculation is performed, such as Figure 4 and Figure 5 As shown;

[0086] (2) Calculate the differential charge density and analyze the charge transfer at the heterojunction interface and the direction of the built-in electric field at the interface, such as Figure 6 As shown;

[0087] (3) The Mulliken population value was calculated to further obtain the charge transfer amounts between atoms in each stable heterojunction structure, which were 0.3 and 0.21 respectively.

[0088] S107, calculate the band edge position of the heterostructure;

[0089] (1) Based on the band gap values ​​of the stable heterostructures obtained in S104 and S106, the band edge positions of the two heterostructures are further calculated (e.g. Figure 7 As shown), the formula is as follows:

[0090] E VBM =-I = -χ-0.5E g

[0091] E CBM =-A = -χ + 0.5E g

[0092] Where I, A and χ represent ionization energy, electron affinity and absolute electronegativity, respectively. g is the band gap of the corresponding material.

[0093] (2) Based on the band gap values ​​of the stable heterostructures obtained in S104 and S106, the band edge positions of the two heterostructures at different pH values ​​(0, 3, 7 and 10) are further calculated as follows:

[0094]

[0095] S108, Calculation of optical properties of heterojunction model;

[0096] Based on the optical absorption properties of single layers and heterostructures obtained with S101, S102 and S104 (e.g. Figure 8 The effects of heterogeneous structures on photocatalytic performance were compared.

[0097] The present invention provides a design and performance prediction of a Janus GaSSe / g-SiC heterostructure photocatalyst material. First, the model establishment process is as follows: GaSe and graphite unit cell structures are obtained by MS software for complete geometric relaxation, and the corresponding single layers are obtained respectively by Cleave surface function; based on the obtained single layer structure, two components of the heterostructure, Janus GaSSe and g-SiC, are designed by atomic substitution; then, according to the relative positions of atoms, the Janus GaSSe / g-SiC and GaSeS / g-SiC heterostructure models are constructed. Subsequently, the structural characteristic size and energy are simulated: the changes in the characteristic structure, electronic properties, energy band arrangement, and light absorption properties of the two heterostructures obtained above are predicted and evaluated, and compared with the properties of the two monolayers, and finally the main controlling factors and influencing rules of the heterostructure producing good photocatalytic performance are revealed. The design and performance prediction of the Janus GaSSe / g-SiC heterostructure photocatalyst material provided by the present invention demonstrates its practical value in the field of photocatalysis and provides a strong guide for the development of future photocatalytic hydrogen production industry technology.

[0098] Two-dimensional materials, which cause large specific surface area, flexibility and mechanical properties, have been widely studied theoretically and experimentally in the field of photocatalysis. However, most photocatalysts use metal Pt to improve the photocatalytic efficiency, which greatly increases the cost of the reaction, increases energy consumption, and may also cause environmental pollution. The reaction kinetics of the photocatalytic decomposition of water are slow, resulting in low overall catalytic reaction efficiency. In addition, due to the mismatch of the band structure of the photocatalyst, the high surface state density and the high recombination rate of photogenerated carriers, the catalyst has low absorption and utilization efficiency of sunlight, especially in the visible and infrared regions. First, the present invention provides a Janus GaSSe / g-SiC heterostructure photocatalyst that can improve the problem of insufficient light absorption performance of g-SiC. The idea of ​​integrating various functional two-dimensional materials to construct heterostructures provides a unique platform for studying new physical phenomena that cannot be obtained in a single two-dimensional material. Experimental verification and theoretical predictions show that heterostructures are more ideal photocatalyst materials than monolayers, which can not only bring good structural stability, but also obtain higher mechanical strength. Compared with two monolayers, the new Janus GaSSe / g-SiC heterostructure as a water splitting photocatalyst has enhanced structural stability and activity due to the synergistic effect of the components, leading to interfacial charge transfer, the formation of new chemical bonds and the generation of built-in electric fields, while also significantly enhancing the absorption capacity of visible light. It is expected to provide new ideas and methods for the development of high-performance photocatalyst materials.

[0099] To this end, the present invention provides a Janus GaSSe / g-SiC heterostructure as a photocatalyst material and predicts its performance. Janus materials obtain significant electronic and optical properties due to breaking the structural symmetry, and the Janus GaSSe single layer prediction shows that it has high intrinsic electron mobility, high light absorption coefficient, piezoelectric coefficient and mechanical stability. Graphite-like silicon carbide (g-SiC) has characteristics such as high specific surface area and strong mechanical properties. Compared with the two monolayers of Janus GaSSe and g-SiC, the synergistic effect between Janus GaSSe and g-SiC significantly enhances the structural stability of the heterostructure and improves the interface carrier separation efficiency. At the same time, it helps to enhance the utilization of visible light, thereby obtaining high solar energy to hydrogen efficiency and catalytic active sites. In addition, the Janus GaSSe / g-SiC heterostructure has a high component richness, which is expected to reduce production costs and improve the sustainability of materials.

[0100] Example 1: Construction and optimization of Janus GaSSe / g-SiC and GaSeS / g-SiC heterostructures

[0101] 1) Construct a Janus GaSSe single-layer structure model:

[0102] Using Material Studio software, firstly, the bulk structure of GaSe was imported and its unit cell structure was optimized to obtain a stable configuration;

[0103] Based on the above stable bulk structure, the section is obtained Supercell GaSe monolayer structure;

[0104] A layer of Se atoms in the GaSe structure was replaced by S atoms to obtain the Janus GaSSe single layer model and perform geometry optimization.

[0105] 2) Construct a g-SiC single-layer structure model:

[0106] The graphite unit cell was imported into Material Studio software, and after geometric optimization, a graphene monolayer was obtained by cross-section.

[0107] The C atoms in the above structure were further replaced by Si atoms to obtain a single-layer g-SiC structure and perform geometry optimization.

[0108] 4) Constructing Janus GaSSe / g-SiC and GaSeS / g-SiC heterostructure models:

[0109] In order to meet the lattice adaptation rate, the The heterostructure model is constructed by using a GaSSe monolayer supercell and a g-SiC monolayer 2×2×1 supercell.

[0110] The constructed heterostructures were subjected to complete structural relaxation to obtain the interlayer distance and structural configuration at the lowest energy.

[0111] Example 2: Study on the photocatalytic performance of single layer and Janus GaSSe / g-SiC heterostructures

[0112] 1) Geometry optimization and stability calculation:

[0113] Optimize the geometric structures of different monolayers and heterojunctions to obtain the most stable structural model;

[0114] Calculate the cohesive energy (E) of each optimized configuration coh ), interlayer distance (d) and binding energy (E bind );

[0115] Compute the phonon spectra and thermodynamic stability of heterostructures.

[0116] 2) Electronic property analysis:

[0117] Analyze the electronic properties of monolayers and heterostructures, including band structure, density of states, electron localization function, and differential charge density.

[0118] 3) Band edge arrangement analysis:

[0119] The band edge arrangement of the heterostructure was calculated based on the obtained band gap value, and the influence of the heterostructure on the photocatalytic performance was elucidated by the band edge position.

[0120] 4) Optical property analysis:

[0121] Calculate the light absorption coefficients of single layers and heterostructures, and compare the effects of heterostructures on light absorption performance.

[0122] The embodiment of the present invention imports the bulk GaSe crystal structure through MS (Materials Studio) software, first performs a monolayer treatment on it, and constructs an intrinsic GaSe monolayer model. Subsequently, a layer of Se atoms in the monolayer structure is replaced by S atoms to generate an asymmetric Janus GaSSe monolayer structure. The asymmetry of this structure gives the material unique electronic properties and photocatalytic performance, while generating a built-in electric field, which helps to promote the separation of electron-hole pairs and improve the efficiency of photocatalytic water decomposition.

[0123] The embodiment of the present invention uses MS software to import the graphite phase crystal structure, and obtains the graphene monolayer structure through section processing. Subsequently, the C atoms in the graphene are partially replaced by Si atoms through the atomic replacement method to generate a g-SiC monolayer structure. The g-SiC monolayer has a wide band gap and excellent optical properties and is an ideal photocatalytic substrate material. By controlling the distribution of Si atoms, the electronic structure of the material can be further adjusted, providing design space for the performance optimization of the heterojunction.

[0124] The present invention uses the Build layer function in MS software to stack the constructed GaSSe single layer and g-SiC single layer to generate a Janus GaSSe / g-SiC heterostructure. The GaSSe monolayer of the supercell is adjusted to ensure the optimal structural matching between the layers of the heterojunction by adjusting the relative atomic arrangement of the two monolayers. The Janus GaSeS / g-SiC heterostructure is further constructed and optimized in a similar way to provide a photocatalytic material model with higher structural stability.

[0125] The embodiment of the present invention obtains the lowest energy stable configuration by geometrically optimizing and calculating the energy of the constructed heterostructure. The interlayer spacing, atomic position and bond length are adjusted using a geometric optimization method (such as the BFGS algorithm) to eliminate excessive stress and interaction between atoms. At the same time, the weak interlayer interactions that may exist in the heterostructure are eliminated by introducing a long-range dispersion correction method (DFT-D). The final optimization model provides a good electronic property and optical performance foundation for photocatalytic water decomposition, and provides guidance for subsequent performance prediction and experimental verification.

[0126] In the embodiment of the present invention, Janus GaSSe and g-SiC are selected to construct a heterostructure. Under illumination conditions, each step of the OER reaction is an exothermic reaction, indicating that the OER can proceed spontaneously. At the same time, the free energy of the OER and HER rate-determining steps of each reaction is significantly reduced, so that the redox reaction performance is improved, which will greatly reduce the additional potential required to be applied. The Janus GaSSe / g-SiC heterostructure can obtain greatly enhanced HER and OER driving forces due to the synergistic effect of interface polarization and band gap components, thereby demonstrating the application potential of the Janus GaSSe heterostructure in enhancing the photocatalytic redox driving force.

[0127] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A design method for Janus GaSSe / g-SiC heterostructure for photocatalytic water decomposition to produce hydrogen, characterized in that: include: Step 1: Use bulk GaSe imported by MS software to establish an intrinsic GaSe single-layer structure model, and replace one layer of Se atoms in the GaSe single layer with S atoms to construct a GaSSe single-layer structure model; Step 2, using the graphite phase structure imported by MS software to obtain the corresponding graphene single-layer structure through sectioning, and using Si atoms to replace C atoms to establish a g-SiC single-layer model; Step three, use the Build layer function to realize the stacking of GaSSe and g-SiC, and build the Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructure models in turn according to the atomic arrangement.

2. The design method according to claim 1, characterized in that: In step 3, a 2×2×1 supercell g-SiC monolayer and Supercell GaSSe monolayer, and construct Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructure models in turn according to the relative positions of atomic arrangements.

3. A method for predicting the performance of Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructure photocatalyst materials as claimed in any one of claims 1 and 2, characterized in that: The following steps are involved: Step 1: geometrically relax the single-layer and heterostructure models to obtain the corresponding minimum energy configuration and characteristic parameters; Step 2, calculating the total energy of the single layer and heterostructure optimized in step 1, and obtaining the cohesive energy of the single layer, the binding energy of the heterostructure and the interlayer spacing; Step 3, structural stability and thermal stability simulation of the two monolayer components and the heterogeneous structure type; Step 4: Based on the most energy stable configuration obtained in step 1, calculate the electronic properties, band edge arrangement and optical properties of the heterostructure.

4. The performance prediction method of the single-layer and heterostructure photocatalytic materials according to claim 3, characterized in that: The BFGS algorithm was used for the complete relaxation in step 1 and step 2. The ultrasoft pseudopotential (USP) was selected as the pseudopotential, and the Perdew-Burke-Ernzerhof (PBE) functional in the generalized gradient approximation (GGA) was selected as the exchange-correlation potential. The convergence parameters were set as follows: the plane wave cutoff energy was 400 eV, the Brillouin zone Monkhorst-Pack k-point grid was 4 × 4 × 1, and the energy threshold was 1 × 10 -5 eV / atom, the maximum force and maximum displacement between atoms are divided into and The DFT-D method is introduced to eliminate the long dispersion interaction; along the vertical direction, the The vacuum layer is used to ensure that periodic interactions between adjacent layers are eliminated.

5. The performance prediction method of single-layer and heterostructure photocatalytic materials according to claim 3, characterized in that: In step 3, the structural stability simulation uses the CASTEP module to calculate the phonon spectrum, and the finite displacement method is selected; the thermal stability simulation uses the molecular dynamics in the DMol3 module, selects the NVT ensemble, sets the temperature to 300K and 500K respectively, the time step is 1fs, and the total duration is 6ps.

6. The performance prediction method of Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructure photocatalyst material according to claim 3, characterized in that: Based on the lowest energy configuration obtained in steps one and two, the CASTEP module is used to perform energy calculations. The electronic properties include electronic energy bands, state density, ELF, differential charge density, work function, and Mulliken atomic population.

7. The performance prediction method of Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructure photocatalyst material according to claim 3, characterized in that: The calculation of energy band arrangement and optical properties obtained in step 4 specifically includes the following steps: (1) Based on the band gap value obtained in step 4, the band edge positions of the monolayer and the heterostructure are calculated to evaluate the effect of the heterostructure on photocatalytic water splitting; (2) Based on steps 1 and 2, calculate the light absorption properties of the monolayer and heterostructure, and analyze the influence of the heterostructure on the light absorption properties.

8. A system for designing and predicting the performance of Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructure photocatalyst materials, characterized in that: The system includes: Modeling module: Import bulk GaSe and graphite phase structures through MS software, build GaSSe single layer and g-SiC single layer structure models respectively, and use the Build layer function to realize the construction of Janus GaSSe / g-SiC and Janus GaSeS / g-SiC heterostructures; Geometry Optimization Module: Provides full geometry relaxation function, uses BFGS algorithm, PBE functional of generalized gradient approximation and ultrasoft pseudopotential, combines DFT-D method to eliminate long-range dispersion interaction, sets optimization parameters such as plane wave cutoff energy, Brillouin zone k-point grid and vacuum layer thickness, and optimizes single-layer and heterogeneous structure models; Performance calculation module: supports phonon spectrum analysis to calculate structural stability, molecular dynamics simulation to calculate thermal stability, and electronic property calculations including electronic energy bands, state density, electronic localization function, differential charge density, and work function; Photocatalytic performance prediction module: Based on the optimized minimum energy configuration, the band edge position and light absorption coefficient are calculated to evaluate the photocatalytic water splitting performance of the heterostructure.

9. The system of claim 8, wherein: The modeling module supports the construction of various supercell forms, including 2×2×1 supercell g-SiC single layer and Supercell GaSSe monolayer to accommodate different atomic arrangement structures; It also supports automatic adjustment of interlayer spacing during the stacking process to ensure the configuration stability of the heterogeneous structure.

10. The system according to claim 8, characterized in that: The performance calculation module uses the CASTEP module to calculate the phonon spectrum and the finite displacement method to analyze the structural stability. The molecular dynamics simulation uses the DMol3 module, and the temperature conditions of 300K and 500K are set based on the NVT ensemble, with a time step of 1fs and a total duration of 6ps to evaluate the thermal stability of the heterostructure.

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