Directional design and screening method for nitrogen doping-organic group coordinated regulation and control of MXene non-noble metal hydrogen evolution electrocatalyst

Abstract

The invention discloses a nitrogen-doped-organic group coordinated regulation MXene non-noble metal hydrogen evolution electrocatalyst oriented design and screening method, which is characterized by comprising the following steps: 1, by taking nitrogen-doped Ti3C2O2 MXene as a substrate, selecting an organic group for modification, and constructing an adsorption type coordinated model; and 2, analyzing the HER activity and site accessibility of the adsorption type collaborative model constructed in the step 1, and screening out an optimal adsorption type collaborative model to obtain the MXene non-noble metal hydrogen evolution electrocatalyst. According to the directional design and screening method, nitrogen-doped Ti3C2O2 MXene is taken as a substrate, organic groups are selected for modification, an adsorption type collaborative model is constructed, and two indexes of HER activity and site accessibility are combined for common screening, so that the research and development period is effectively shortened, the stability and active site density are both considered, and the method is suitable for the field of preparation of electrochemical catalysts.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of electrochemical catalysis and new materials, and in particular relates to a method for the directional design and screening of nitrogen-doped and organic groups synergistically regulating MXene non-noble metal hydrogen evolution electrocatalysts. Background Technology

[0002] In the development of catalysts for hydrogen production through water electrolysis, while single-doped non-noble metal MXene catalysts have shown improved activity, they still face two key challenges: first, poor accessibility of active sites, with MXene layers easily stacking and some active sites being masked; second, limited electron transfer efficiency, as single doping has insufficient ability to regulate the electron distribution of Ti-3d orbitals, making it difficult to achieve ΔG H* Approaching the thermodynamic ideal state, and the localization of electrons easily leads to excessively strong or weak H adsorption, affecting reaction kinetics.

[0003] Organic group modification is an effective means to optimize catalyst performance, but existing studies mostly use single organic molecule modification, which has drawbacks such as poor modification stability (organic molecules are prone to desorption), unclear electron transport pathways, and low active site density. In addition, traditional design methods lack systematic research on the matching between organic group structure (such as conjugation degree and polar groups) and nitrogen-doped substrate, which makes it difficult to fully realize the synergistic effect and simultaneously optimize the catalyst activity, stability and site accessibility.

[0004] Therefore, it is urgent to construct a "nitrogen doping-organic group" synergistic regulation system, and through the synergistic effect of electronic structure regulation and spatial structure optimization, to break through the performance limitations of single modification strategies and achieve efficient and precise design of non-metallic HER catalysts. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for the directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts. This method uses nitrogen-doped Ti3C2O2MXene as a substrate, selects organic groups for modification, constructs an adsorption-type synergistic model, and combines HER (hydrogen evolution reaction) activity and site accessibility as two major indicators for screening. This effectively shortens the research and development cycle and solves the problems of poor stability, unclear electron transport pathways, and low active site density in organic-group modified catalysts.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a method for the directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts, characterized in that the directional design and screening method includes the following steps: Step 1: Using nitrogen-doped Ti3C2O2MXene as a substrate, select organic groups for modification to construct an adsorption-type synergistic model; Step 2: Analyze the HER activity and site accessibility of the adsorption-type synergistic model constructed in Step 1, screen out the optimal adsorption-type synergistic model, and obtain the MXene non-noble metal hydrogen evolution electrocatalyst.

[0007] This invention modifies the substrate with organic groups. The polar groups in the organic groups act as electron acceptors, forming a directional electron transfer channel of "Ti→substrate→organic molecule→H*". The steric hindrance effect can suppress the stacking of MXene layers, which greatly increases the density of active sites and solves the problem of accessibility of active sites.

[0008] The above-mentioned method for the directional design and screening of nitrogen-doped and organic group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts is characterized in that, in step one, the number of N atoms in the nitrogen-doped Ti3C2O2MXene accounts for 16.6% to 22.2% of the total number of N and C atoms.

[0009] This invention utilizes nitrogen-doped Ti3C2O2MXene with an N / C atomic ratio of 16.6%~22.2% as a substrate. This substrate uses Ti3C2O2MXene as a support, with nitrogen atoms replacing carbon sites in the crystal lattice as dopant. When the N / C atomic ratio is 16.6%~22.2%, the substrate itself has an E... form <0eV、|ΔG H* With a voltage of ≤0.10eV, it possesses dispersed Ti-N bonds and optimized Ti-3d orbital electronic state density, and has no lattice distortion, thus providing a stable electronic environment for organic group modification.

[0010] The above-mentioned method for the directional design and screening of nitrogen-doped organic group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts is characterized in that, in the adsorption-type synergistic model described in step one, the organic group is combined with nitrogen-doped Ti3C2O2MXene through coordination bonds.

[0011] This invention modifies organic groups by employing coordinate bond adsorption, which significantly reduces ΔG compared to doping modification. H* (Hydrogen adsorption free energy).

[0012] The above-mentioned method for the directional design and screening of nitrogen-doped and organic groups synergistically regulated MXene non-noble metal hydrogen evolution electrocatalysts is characterized in that the organic groups are modified only in the active site region of nitrogen-doped Ti3C2O2MXene.

[0013] This invention designs a "site loading" strategy to control the modification of organic groups only in the active site region, thereby reducing ineffective loading and improving the mass activity of the electrocatalyst by more than 25%.

[0014] The above-mentioned method for the directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts is characterized in that the organic groups are selected from -NH2, CH3NHC2H5NH, CH3NH, CH3N, C2H5NH, C2H5N, C3H7NH, C3H7N, C6H5NH, C 12 H 11 NH, C 12 H8NH.

[0015] The above-mentioned method for the directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts is characterized in that the screening method in step two is: calculating ΔG using first-principles calculations. H* And interlayer spacing, according to |ΔG H* Under the condition of |≤0.10eV, combined with the interlayer spacing, systems with hindered electron transfer and interlayer stacking were excluded, and the optimal adsorption-type synergistic model was selected.

[0016] This invention utilizes ΔG H* Controlling the catalytic activity of the electrocatalyst model, when |ΔG H* |≤0.10eV, approaching the thermodynamic optimum, close to the ideal catalytic activity of Pt(111); by controlling the interlayer spacing to improve site accessibility, the original state of the nitrogen-doped Ti3C2O2MXene substrate is prone to tight stacking due to interlayer forces, which leads to the shielding of active sites between layers, making it difficult for reactants to enter the interlayer to contact active sites. By screening an adsorption-type synergistic model with an interlayer spacing adapted to the reaction system, it can expose hidden active sites and build efficient transport channels; by combining the two indicators, the optimal adsorption-type synergistic model that balances stability and catalytic activity is screened.

[0017] The above-mentioned method for the directional design and screening of nitrogen-doped and organic group-synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts is characterized by verifying the optimal adsorption-type synergistic model described in step two to obtain the non-noble metal hydrogen evolution electrocatalyst.

[0018] The above-mentioned method for the directional design and screening of nitrogen-doped and organic group-synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts is characterized by the following verification method: the amount of transferred electrons is analyzed by differential charge density, the root mean square shift is obtained by molecular dynamics simulation, and the hybridization degree of Ti-3d and N-2p orbitals is combined to comprehensively verify the HER activity and stability.

[0019] This invention comprehensively verifies the activity and stability of HER through differential charge density analysis, root-mean-square shift, and the degree of hybridization of Ti-3d and N-2p orbitals; it uses differential charge density analysis to determine the amount of transferred electrons; it obtains the root-mean-square shift through molecular dynamics simulations to determine the degree of interlayer stacking and long-term catalytic stability; and it determines ΔG through the degree of hybridization of Ti-3d and N-2p orbitals. H* Due to ΔG H* ΔG is positively correlated with the degree of hybridization of Ti-3d and N-2p orbitals; the higher the degree of hybridization of Ti-3d and N-2p orbitals, the greater the ΔG. H* The closer it gets to 0 eV, the closer it is to the ideal catalytic activity of Pt(111).

[0020] The above-mentioned method for the directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts is characterized in that the amount of electrons transferred by the non-noble metal hydrogen evolution electrocatalyst in step two is >1.3. Interlayer spacing > 1.0 nm, velocity-limiting step free energy barrier < 0.03 eV, Tafel slope < 35 mV / dec.

[0021] Compared with the prior art, the present invention has the following advantages: 1. This invention constructs a synergistic regulatory system of "nitrogen doping-organic groups". By using nitrogen-doped Ti3C2O2MXene as a substrate, the distribution of Ti-3d orbital electrons is regulated by Ti-N bonds, thereby controlling ΔG H* Approaching 0 eV and exhibiting good stability, combined with the enhanced catalytic performance of organic groups, breakthroughs in the activity and stability of non-precious metal hydrogen evolution electrocatalysts can be achieved; then, by combining HER activity and site accessibility, non-precious metal hydrogen evolution electrocatalysts that balance activity, stability, and site accessibility are screened.

[0022] 2. This invention comprehensively verifies the stability of the screening results through differential charge density analysis, root mean square displacement, and the degree of hybridization of Ti-3d and N-2p orbitals. By constructing a complete directional design and screening system, it achieves the precise design of non-noble metal hydrogen evolution electrocatalysts and realizes triple optimization of "activity-stability-site accessibility", ultimately obtaining ΔG. H* The potential for hydrogen evolution is -0.002 eV, the hydrogen evolution overpotential is 0.08 V, and the amount of electrons transferred is >1.3. Non-noble metal hydrogen evolution electrocatalysts with interlayer spacing >1.0 nm, rate-limiting step free energy barrier <0.03 eV, and Tafel slope <35 mV / dec exhibit significantly better performance than single-modified non-metallic catalysts, providing a universal principle for the design of non-metallic catalytic systems.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 The MXene non-noble metal hydrogen evolution electrocatalyst of this invention is modified with N2 and NH2. 16.6% Differential charge density plot of @Ti3C2O2.

[0025] Figure 2 The MXene non-noble metal hydrogen evolution electrocatalyst of this invention is modified with N3H7N. 22.2% Differential charge density plot of @Ti3C2O2.

[0026] Figure 3 The MXene non-noble metal hydrogen evolution electrocatalyst of this invention is modified with N2 and NH2. 16.6% @Ti3C2O2 density of states results.

[0027] Figure 4 The MXene non-noble metal hydrogen evolution electrocatalyst of this invention is modified with N3H7N. 22.2% @Ti3C2O2 density of states results.

[0028] Figure 5 N modified with different organic groups in this invention 16.6% @Ti3C2O2's ΔG H* Result image.

[0029] Figure 6 N modified with different organic groups in this invention 22.2% @Ti3C2O2's ΔG H* Result image.

[0030] Figure 7 For the present invention N 16.6% @Effective catalytic range diagram of Ti3C2O2. Detailed Implementation

[0031] Example 1 The targeted design and screening method in this embodiment includes the following steps: Step 1: Construct a 3×3×1 supercell model using density functional theory (DFT). Using VASP software, a nitrogen-doped Ti3C2O2MXene substrate with N / C atomic ratios of 16.6% and 22.2% was used as the substrate. The following parameters were selected: -NH2, CH3NHC2H5NH, CH3NH, CH3N, C2H5NH, C2H5N, C3H7NH, C3H7N, C6H5NH, and C... 12 H 11 NH, C 12H8NH coordinates and adsorbs Ti atoms on the substrate surface, constructing an adsorption-type co-adsorption model. The nitrogen-doped sites in this model are internal carbon sites within the crystal lattice, and coordination adsorption occurs only in the active site region. The nitrogen-doped Ti3C2O2MXene adsorption-type co-adsorption model, where N atoms account for 16.6% of the total N and C atoms, is denoted as N. 16.6% @Ti3C2O2, a nitrogen-doped Ti3C2O2 with N atoms accounting for 22.2% of the total number of N and C atoms, denoted as N in the MXene adsorption cooperative model. 22.2% @Ti3C2O2; Step 2: Calculate ΔG of the adsorption-type cooperative model constructed in Step 1 using first-principles calculations. H* Based on the interlayer spacing, the optimal adsorption-type synergistic model was selected as: NH2-modified N 16.6% @Ti3C2O2 and C3H7N modify N 22.2% @Ti3C2O2; Measurements showed that NH2 modified N 16.6% @Ti3C2O2's ΔG H* The value is -0.002 eV, and the amount of electrons transferred is 1.45. The interlayer spacing is 1.1 nm, and the hybridization degree of Ti-3d and N-2p orbitals is the highest; the C3H7N-modified N 22.2% @Ti3C2O2's ΔG H* The voltage is -0.002 eV, and the interlayer spacing is 1.2 nm. The optimal adsorption-type synergistic model was validated: (1) Differential charge density analysis was used, and the results are as follows: Figure 1 and Figure 2 As shown (yellow area represents electron accumulation, blue area represents electron loss), the measured N2 modified with NH2 was... 16.6% The amount of electrons transferred from -NH2 in Ti3C2O2 is 1.45. Electrons accumulate and concentrate in N atoms (grayish-blue); measurements show that C3H7N modifies N atoms. 22.2% The number of electrons transferred from C3H7N in Ti3C2O2 is 1.33. This indicates that local charge transfer significantly alters the electron density around the catalytic active site and directly affects hydrogen bonding. In contrast, C3H7N gains 1.33 electrons, and its longer alkyl chain introduces steric hindrance, limiting charge migration on the catalyst surface. (2) The root mean square displacement (RMSD) was analyzed by molecular dynamics simulation. NH2-modified N 16.6% @Ti3C2O2 has an RMSD < 0.15 Å, and C3H7N modifies N. 22.2%The RMSD of @Ti3C2O2 is 0.08 Å, which is significantly lower than that of the original substrate (RMSD=0.3 Å), thus improving the interlayer stacking phenomenon and significantly enhancing the structural stability. (3) The results of detecting the density of states are as follows: Figure 3 and Figure 4 As shown, -NH2 modifies N 16.6% @Ti3C2O2 and C3H7N modify N 22.2% The Ti-3d and N-2p orbitals of @Ti3C2O2 are strongly hybridized in the range of -3eV to 0eV, forming a continuous electronic state, which promotes electron exchange between H* and active sites; Based on differential charge density analysis, molecular dynamics simulation analysis, and density of states analysis, the MXene non-noble metal hydrogen evolution electrocatalyst is determined to be NH2-N. 16.6% @Ti3C2O2 and C3H7N-N 22.2% @Ti3C2O2.

[0032] In step one of this embodiment, N is modified with different organic groups. 16.6% @Ti3C2O2 and N 22.2% @Ti3C2O2's ΔG H* like Figure 5 and Figure 6 As shown, -NH2 modifies N 16.6% @Ti3C2O2 and C3H7N modify N 22.2% @Ti3C2O2's ΔG H* The lowest values ​​were all -0.002 eV, which is better than other organic group-modified adsorption-type synergistic models, further verifying the accuracy of the MXene non-noble metal hydrogen evolution electrocatalyst screened in this embodiment; Active sites were identified using Bader charge analysis and ΔGH* mapping. 16.6% The effective catalytic range of the Ti3C2O2 system is as follows: Figure 7 As shown, the Ti atom adjacent to the central -NH2 (point 1) and the Ti atom at the substrate edge (point 3) are active sites, with ΔGH* values ​​of -0.002 eV and -0.005 eV, respectively; while the ΔGH* value of the Ti atom adjacent to the first cyclic amino group (point 2) is -0.12 eV, which is an inactive site. This verifies the correctness of the present invention in modifying organic groups only in the active site region, reducing ineffective loading, optimizing molecular loading, and improving the catalyst's mass activity by 25%. Upon testing, the ΔG of the MXene non-noble metal hydrogen evolution electrocatalyst in this embodiment was determined. H* The potential for hydrogen evolution is -0.002 eV, the hydrogen evolution overpotential is 0.08 V, and the amount of electrons transferred is >1.3. Interlayer spacing > 1.0 nm, velocity-limiting step free energy barrier < 0.03 eV, Tafel slope < 35 mV / dec.

[0033] Comparative Example 1 This comparative example uses organic group doping modification to construct a synergistic model.

[0034] Testing revealed that the comparative sample's doping modification ΔG H* The value is -0.05 eV to -0.15 eV, while in Example 1, adsorption modification of ΔG was used. H* The voltage range is -0.002 eV to -0.05 eV. This is because the insertion of organic groups into the lattice during doping modification leads to the breakage of Ti-N bonds, thereby increasing ΔG. H* Large fluctuations and a decrease in active site density of over 30%; however, during adsorption modification, organic groups bind to the substrate through coordination bonds, without disrupting the MXene lattice structure, ΔG H* The small fluctuation range indicates the correctness of the adsorption modification chosen in this invention.

[0035] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for the directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts, characterized in that, This targeted design and screening method includes the following steps: Step 1: Using nitrogen-doped Ti3C2O2 MXene as a substrate, select organic groups for modification to construct an adsorption-type synergistic model; Step 2: Analyze the HER activity and site accessibility of the adsorption-type synergistic model constructed in Step 1, screen out the optimal adsorption-type synergistic model, and obtain the MXene non-noble metal hydrogen evolution electrocatalyst.

2. The method for directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts according to claim 1, characterized in that, In step one, the number of N atoms in the nitrogen-doped Ti3C2O2MXene accounts for 16.6% to 22.2% of the total number of N and C atoms.

3. The method for directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts according to claim 1, characterized in that, In the adsorption-type synergistic model described in step one, the organic groups are combined with nitrogen-doped Ti3C2O2MXene through coordination bonds.

4. The method for directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts according to claim 3, characterized in that, The organic groups are modified only in the active site region of nitrogen-doped Ti3C2O2 MXene.

5. The method for directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts according to claim 1, characterized in that, The organic groups are selected from -NH2, CH3NHC2H5NH, CH3NH, CH3N, C2H5NH, C2H5N, C3H7NH, C3H7N, C6H5NH, C 12 H 11 NH, C 12 H8NH.

6. The method for directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts according to claim 1, characterized in that, The screening method described in step two is as follows: ΔG is calculated using first-principles calculations. H* And interlayer spacing, according to |ΔG H* Under the condition of |≤0.10eV, combined with the interlayer spacing, systems with hindered electron transfer and interlayer stacking were excluded, and the optimal adsorption-type synergistic model was selected.

7. The method for directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts according to claim 1, characterized in that, The optimal adsorption-type synergistic model described in step two was verified to obtain the MXene non-noble metal hydrogen evolution electrocatalyst.

8. The method for directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts according to claim 7, characterized in that, The verification method is as follows: the amount of transferred electrons is analyzed by differential charge density, the root mean square shift is obtained by molecular dynamics simulation, and the hybridization degree of Ti-3d and N-2p orbitals is combined to comprehensively verify the activity and stability of HER.

9. The method for directional design and screening of nitrogen-doped and organic-group synergistic regulation of MXene non-noble metal hydrogen evolution electrocatalysts according to claim 1, characterized in that, The amount of transferred electrons in the MXene non-noble metal hydrogen evolution electrocatalyst described in step two is >1.

3. Interlayer spacing > 1.0 nm, rate-limiting step free energy barrier < 0.03 eV, Tafel slope < 35 mV / dec.

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