阅读说明：本技术 一种负载型单层水滑石结构研究方法 (Method for researching structure of supported single-layer hydrotalcite ) 是由 夏盛杰 方镭 倪哲明 于 2019-08-29 设计创作，主要内容包括：本发明提供了一种负载型单层水滑石结构研究方法,利用Material Studio,构建出不同负载构型的单层水滑石结构,利用Castep程序包对不同负载的单层水滑石结构性能进行表征,根据表征数据筛选得到负载型单层水滑石的合理结构；本发明利用密度泛函理论模拟方法,成功构建单层水滑石的单原子催化剂模型、合金团簇负载模型以及氧化物负载模型,通过量子化学软件Castep可以快速预测不同负载结构单层水滑石的稳定性,缩短实验合成周期,且可以分析不同负载金属对单层水滑石催化活性的影响,为实验中制备高效催化剂提供有效的理论基础。(The invention provides a method for researching a loaded single-layer hydrotalcite structure, which comprises the steps of constructing single-layer hydrotalcite structures with different load configurations by using Material Studio, representing the structural performance of the single-layer hydrotalcite structures with different loads by using a Castep program package, and screening according to representation data to obtain a reasonable structure of the loaded single-layer hydrotalcite; according to the invention, a single-atom catalyst model, an alloy cluster load model and an oxide load model of the single-layer hydrotalcite are successfully constructed by using a density functional theory simulation method, the stability of the single-layer hydrotalcite with different load structures can be rapidly predicted through quantum chemistry software Castep, the experimental synthesis period is shortened, the influence of different load metals on the catalytic activity of the single-layer hydrotalcite can be analyzed, and an effective theoretical basis is provided for preparing a high-efficiency catalyst in an experiment.)

1. A method for researching a supported single-layer hydrotalcite structure is characterized by comprising the following steps:

(1) the method for constructing the single-layer hydrotalcite load model comprises the following steps: the single-layer hydrotalcite load model is zinc-aluminum hydrotalcite, and a hydrotalcite laminate with Zn/Al of 3 is constructed and is expressed as [ Zn ]₁₂Al₄(OH)₃₂]⁴⁺And has D_3dSymmetry, space group of which is R-3 m; the hydrotalcite main body laminated plate structure is expressed by adopting a molecular cluster model, wherein all Zn and Al are in a uniform plane, and 6 Zn form a regular hexagon structure around an Al atom because of the Al³⁺Isomorphously substituted for Zn²⁺The octahedral unit is charged with a positive charge, so that Al ions are far away from each other and distributed in short distanceHomogenizing; to balance the positive charges on the laminate surface and make the structure electrically neutral, NO is selected₃ ^-The hydrotalcite main body laminate obtained by optimization is orderly arranged along the direction of unit cell c to form a single-cell-sized single-layer hydrotalcite structure;

(2) constructing a single-atom loaded single-layer hydrotalcite, an alloy cluster loaded single-layer hydrotalcite and an oxide loaded structure by using Material Studio, and then optimizing the configuration of the single-atom loaded single-layer hydrotalcite, the alloy cluster loaded single-layer hydrotalcite and the oxide loaded structure to explore the optimal configuration of the alloy cluster loaded single-layer hydrotalcite;

(3) performing geometric optimization and property analysis on the configuration through a first-nature principle software package Castep, and performing optimization calculation on the system by adopting a DFT-D2 method in order to better consider van der Waals force in the system; wherein the electron exchange correlation functional is based on a Perew-Burke-Ernzerhof functional of generalized gradient integral, inner layer electrons of multi-element hydrotalcite atoms are subjected to frozen core treatment and are replaced by effective nuclear potential pseudopotential, a valence electron wave function is expanded by a double-numerical polarization function, and electron spin is not limited; the smearing is set to 0.005hartree, and the self-consistent field calculation error is 1 multiplied by 10^-6Ha, setting k vector points of the Brillouin zone as 6 multiplied by 1; the criterion of the rationality of the structure optimization is as follows: energy difference less than 1 x 10^-5hartree, forces on individual atoms less thanAtomic shift of less thanAnd zero point energy correction is considered in all calculations, and the specific algorithm is as follows:

(4) different loaded single-layer hydrotalcite configurations have different structural constants, and the most obvious change is reflected in the change of bond length and bond angle, one reason is that different loads generate different coordination actions on the surface and the periphery of the single-layer hydrotalcite, so that part of metal ions which are originally +2 valence exhibit a sub-divalent stateThe structural stability of the multi-element hydrotalcite is specifically discussed by introducing binding energy, E_total、E_A、E_B、and E_OHRespectively optimizing Total Energy of the multi-element hydrotalcite, Energy of all A metals in a super cell, Total Energy of all B metals in the super cell, Total Energy of all nitrate radicals in a system and Total Energy of hydroxyl in the system; the energy is recorded in an output file castep, and the structural stability of different loaded single-layer hydrotalcite can be described specifically through bond length bond angles and binding energy;

(5) prediction of electronic activity of different loaded single-layer hydrotalcite: the electronic activity of the compound is described by adopting the center of a d electronic band, and the formula is as follows:the d-band center can well describe the electronic activity of the material, the strength of the catalyst activity and the maximum promotion of the electronic activity of the single-layer hydrotalcite by which load is the most are judged by judging the size of the d-band center, and the state density diagrams of different orbital electrons of the material can be specifically analyzed to determine the overall electronic distribution condition of the material;

(6) prediction of electron transfer difficulty: the work function can well show the difficulty of electron transfer of different loaded hydrotalcites, and the work function W is the vacuum energy level E_v-Fermi level E_fAnd after the optimal calculation of the vacuum energy level and the Fermi energy level in the castep module is finished, deriving potential in analysis to obtain the vacuum energy level and the Fermi energy level. The improvement of the electron transfer capability of different loads to the single-layer hydrotalcite can be shown; in addition, electrons in the Castep module can be clarified through Charge diversity difference and Mulliken ChargeTransferring and analyzing the bonding strength;

(7) for different configuration loaded single-layer hydrotalcite models: the electronic localization function is a favorable tool for analyzing the bond type and the lone pair electron distribution so as to express the localized distribution characteristics of electrons, and has the advantages that the local molecular orbit does not need to be calculated, and the calculation amount is small; the electron localization function diagram ELF can more intuitively express the transfer direction of electrons in a material system and the electron transfer condition between carriers and load atoms in the single-layer hydrotalcite with different load configurations.

2. The method for studying the structure of supported single-layered hydrotalcite according to claim 1, wherein the density of states diagram and d-band center in step (5) are visually analyzed by MS on the output file, PDOS diagram of s, p, d electron orbitals are plotted, and the value of d-band center is obtained by the formula in step (5).

3. The method for researching the structure of the supported single-layer hydrotalcite as claimed in claim 1, wherein in the step (7), when the electronic localization function of the supported hydrotalcite with different configurations is plotted, the electronic localization function analysis is performed on the structure file under a Castep module, after electronic information is introduced, the structure is cut, and the threshold value in the color maps is adjusted, so that an electronic localization function graph can be obtained.

(I) technical field

The invention relates to the technical field of load type single-layer hydrotalcite structure building and property calculation, and relates to a load type single-layer hydrotalcite structure research method.

(II) background of the invention

The layered double hydroxide is a general name of hydrotalcite and hydrotalcite-like compound, causes a special layered structure, and has the characteristics of adjustable chemical composition of a host layer plate, adjustable types and quantity of interlayer object anions, adjustable particle size and distribution of an intercalation assembly body and the like. In the presence of catalytic hydrogenation, CO₂The method has a plurality of applications in the aspects of reducing and degrading organic pollutants by photocatalysis. The single-layered hydrotalcite (mono-LDHs) is a new material with excellent specific surface area and catalytic activity, which is recently reported, and the single-layered hydrotalcite structure is mainly obtained by carrying out laminate peeling on the original hydrotalcite. In order to improve the stability and catalytic activity of the single-layer hydrotalcite, the single-layer hydrotalcite is usually modified by loading metals, oxides and the like with different sizes on the single-layer hydrotalcite in literature reports, so as to obtain a catalyst with better performance.

However, how metals or oxides with different sizes are loaded on the surface of the single-layer hydrotalcite is rarely reported, and a multi-metal loaded single-layer hydrotalcite model is not reported. Therefore, it is particularly important to elaborate the model of the single-layer hydrotalcite supported system. According to the invention, the structures of single-layer hydrotalcite loaded single metal atoms, single-layer hydrotalcite loaded alloy clusters and single-layer hydrotalcite loaded oxides can be clearly illustrated through a first-principle calculation software Castep, the stability, the electronic activity and other properties of the single-layer hydrotalcite are researched, and sufficient theoretical basis can be provided for experimental preparation of the loaded single-layer hydrotalcite.

The Density Functional Theory (DFT) is one of the most important theories in the first principle, has wide application in predicting the activity of the catalyst, researching and developing novel functional materials and drug research and development, and can greatly shorten the experimental period and the experimental cost. According to the invention, a single-atom catalyst model (SACs), an alloy cluster loading model and an oxide loading model of the single-layer hydrotalcite are studied in detail by using a first-principle software package Castep, and loading structures of catalysts with different sizes and different forms on the single-layer hydrotalcite are clarified. The theoretical calculation can indicate the direction for preparing the single-layer hydrotalcite catalyst with excellent performance in the experiment.

Disclosure of the invention

The invention provides a method for researching a loaded single-layer hydrotalcite structure, which comprises the steps of constructing single-layer hydrotalcite structures with different load configurations by using Material Studio (MS), representing the structural performance of the single-layer hydrotalcite structures with different loads by using a Castep program package, and screening according to representation data to obtain the reasonable structure of the loaded single-layer hydrotalcite.

The technical scheme of the invention is as follows:

a method for researching a supported single-layer hydrotalcite structure, which comprises the following steps:

(1) the method for constructing the single-layer hydrotalcite load model comprises the following steps: the single-layer hydrotalcite supported model is specifically, for example, zinc-aluminum hydrotalcite, and a hydrotalcite laminate with Zn/Al of 3 is constructed, and is represented as [ Zn ]₁₂Al₄(OH)₃₂]⁴⁺And has D_3dSymmetry, space group of which is R-3 m; the hydrotalcite main body laminated plate structure is expressed by adopting a molecular cluster model, wherein all Zn and Al are in a uniform plane, and 6 Zn form a regular hexagon structure around an Al atom because of the Al³⁺Isomorphously substituted for Zn²⁺The octahedral unit is provided with a positive charge, so that Al ions are far away from each other and are uniformly distributed in a short distance; to balance the positive charges on the laminate surface and make the structure electrically neutral, NO is selected₃ ^-The hydrotalcite main body laminate obtained by optimization is orderly arranged along the direction of unit cell c to form a single-cell-sized single-layer hydrotalcite structure;

(2) constructing a single-atom loaded single-layer hydrotalcite, an alloy cluster loaded single-layer hydrotalcite and an oxide loaded structure by using Material Studio (MS), and then optimizing the configuration of the single-atom loaded single-layer hydrotalcite, the alloy cluster loaded single-layer hydrotalcite and the oxide loaded structure to explore the optimal configuration of the alloy cluster loaded single-layer hydrotalcite;

(3) geometric optimization and property analysis are carried out on the configuration through a first-nature principle software package Castep, and in order to better consider van der Waals force in the system, the DFT-D2 method is adopted to carry out optimization calculation on the system; wherein the electron exchange correlation functional is based on Perew-Burke-Ernzehof (PBE) functional of generalized gradient integral (GGA), inner layer electrons of multi-element hydrotalcite atoms are subjected to frozen core treatment and are replaced by effective nuclear potential pseudopotential (ECP), valence electron wave function is expanded by adopting a double numerical polarization function (DNP), and electron spin is not limited; the smearing is set to 0.005hartree, and the self-consistent field calculation error (SCF tolerance) is 1 × 10^-6Ha, Brillouin zone (Brillouin zone) k vector (k-point set) point is set to 6 x 1; the criterion of the rationality of the structure optimization is as follows: energy difference less than 1 x 10^-5hartree, eachForce on one atom less thanAtomic shift of less thanAnd zero point energy correction (ZPE) is considered for all calculations, and the specific algorithm is as follows:

(4) the configuration of different loaded single-layer hydrotalcite has different structural constants, which are most obviously reflected in the change of bond length and bond angle, one reason is that different loads generate different coordination on the surface and the periphery of the single-layer hydrotalcite, so that part of metal ions which are originally in a valence of +2 are in a state of a subvalence state, the structural stability of the multi-element hydrotalcite is specifically discussed by introducing binding energy, E_total、E_A、E_B、and E_OHRespectively optimizing Total Energy of the multi-element hydrotalcite, Energy of all A metals in a super cell, Total Energy of all B metals in the super cell, Total Energy of all nitrate radicals in a system and Total Energy of hydroxyl in the system; the energy is recorded in an output file castep, and the structural stability of different loaded single-layer hydrotalcite can be described specifically through bond length bond angles and binding energy;

(5) prediction of electronic activity of different loaded single-layer hydrotalcite: the electronic activity of the compound is described by adopting the center of a d electronic band, and the formula is as follows:d the center of the belt canThe electronic activity of the hydrotalcite is well described, the strength of the catalyst activity and which kind of load has the largest improvement on the electronic activity of the single-layer hydrotalcite are judged by judging the center size of the d-band, and the state density diagrams of different orbital electrons of the material can be specifically analyzed to determine the overall electronic distribution condition of the material;

(6) prediction of electron transfer difficulty: the work function can well show the difficulty of electron transfer of different loaded hydrotalcites, and the work function W is the vacuum energy level E_v-Fermi level E_fAnd after the optimal calculation of the vacuum energy level and the Fermi energy level in the castep module is finished, deriving potential in analysis to obtain the vacuum energy level and the Fermi energy level. The improvement of the electron transfer capability of different loads to the single-layer hydrotalcite can be shown; in addition, the electron transfer condition can be determined through the Charge densitydifference and Mulliken Charge under the Castep module, and the bonding strength of the electron transfer condition can be analyzed;

(7) for different configuration loaded single-layer hydrotalcite models: the electronic localization function is a favorable tool for analyzing the bond type and the lone pair electron distribution so as to express the localized distribution characteristics of electrons, and has the advantages that the local molecular orbit does not need to be calculated, and the calculation amount is small; the electron localization function diagram ELF can more intuitively express the transfer direction of electrons in a material system (as shown in FIG. 4), and the electron transfer condition between carriers and load atoms in the single-layer hydrotalcite with different load configurations.

And (5) performing visual analysis on the output file by using the MS to draw a PDOS (polymer dispersed oxide) graph of electronic tracks such as s, p, d and the like by using the state density graph and the d-band center in the step (5), and solving the value of the d-band center by using the formula in the step (5).

When the electronic localization function of the loaded hydrotalcite with different configurations is plotted in the step (7), the structure file is subjected to electronic localization function analysis under a Castep module, after electronic information is introduced, the structure is subjected to tangent planes (Creat slices), and the threshold value in the color maps is adjusted, so that an electronic localization function graph (ELF) in the graph 4 can be obtained.

The invention has the beneficial effects that: the invention successfully constructs single-atom catalyst models (SACs), alloy cluster load models and oxide load models of the single-layer hydrotalcite by using a density functional theory simulation method. The stability of the single-layer hydrotalcite with different load structures can be rapidly predicted through quantum chemistry software Castep, and the experimental synthesis period is shortened. And the influence of different loaded metals on the catalytic activity of the single-layer hydrotalcite can be analyzed, and an effective theoretical basis is provided for preparing the high-efficiency catalyst in an experiment.

(IV) description of the drawings

FIG. 1 is a top and side view of a ZnAl single layered hydrotalcite;

FIG. 2 is ZnAl single-layer hydrotalcite with different loading configurations; (a) a single-atom supported single-layer hydrotalcite structure (Au/mono-ZnAl-LDHs), (b) a multi-metal supported single-layer hydrotalcite structure (Au/M/mono-ZnAl-LDHs), (c) an oxide supported single-layer hydrotalcite structure (NiO/mono-ZnAl-LDHs);

FIG. 3 is a state density diagram of ZnAl single-layer hydrotalcite loaded in different sizes;

FIG. 4 is an Electron Localization Function (ELF) diagram of ZnAl single-layer hydrotalcite structures with different gold cluster loading sizes;

FIG. 5 shows a single-gold-supported hydrotalcite structure (Au)₁mono-ZnAl-LDHs).

(V) detailed description of the preferred embodiments

Although there are many experimental reports on single-layer hydrotalcite supported catalysts, there are few reports on how different supports are supported on the surface of the catalyst. The invention specifically describes a model construction method of three different load single-layer hydrotalcite and a structure research method thereof, and further describes the method by specific examples.