Directional design and screening method of nitrogen-doped MXene supported non-noble electrocatalyst for hydrogen fuel cell

Abstract

The invention discloses an oriented design and screening method of a nitrogen-doped MXene supported non-noble electrocatalyst for a hydrogen fuel cell, and the oriented design and screening method comprises the following steps: 1, by taking Ti3C2O2 MXene as a carrier, selecting nitrogen atoms to replace and dope through lattice carbon sites, and constructing a series of N / C proportion electrocatalyst models; and 2, carrying out thermodynamic stability and catalytic activity analysis on the series of N / C ratio electrocatalyst models, and screening out an electrocatalyst model with optimal stability and activity to obtain the nitrogen-doped MXene supported non-noble electrocatalyst. According to the directional design and screening method, Ti3C2O2 MXene is used as a carrier to construct a series of N / C proportional electrocatalyst models doped with nitrogen, and two indexes of thermodynamic stability and catalytic activity are combined for common screening, so that the research and development period is effectively shortened, both activity and stability are considered, and the method is suitable for the field of preparation of electrochemical catalysts.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis and hydrogen energy technology, and in particular relates to a method for the directional design and screening of nitrogen-doped MXene supported non-precious electrocatalysts for hydrogen fuel cells. Background Technology

[0002] Hydrogen energy, as a clean and efficient secondary energy source, is one of the core carriers for achieving the goal of "carbon neutrality." Electrolysis of water to produce hydrogen has become the mainstream technological route for hydrogen production due to its mild reaction conditions and high product purity. Electrocatalysts are the core components of hydrogen production via water electrolysis. Traditional hydrogen evolution reaction catalysts mostly rely on precious metals such as Pt and Ir, whose high cost and scarcity severely limit their large-scale application. Non-precious metal catalysts have become a research hotspot due to their low cost and environmental friendliness; however, existing non-metallic systems generally suffer from core bottlenecks such as insufficient activity and poor stability.

[0003] MXene materials, with their high conductivity, tunable surface functional groups, and excellent structural stability, have shown great potential in the field of electrocatalysis. Among them, MXene, due to the efficient electron transfer channels constructed by its surface -O functional groups, has become an ideal carrier for non-metallic catalysts. However, the HER (hydrogen evolution reaction) activity of single MXene is limited, requiring optimization of its electronic structure through doping modification. Currently, the design of nitrogen-doped MXene catalysts largely relies on empirical trials, lacking precise control over the structure-activity relationship between doping ratio, doping sites, and catalytic performance. This leads to a highly arbitrary screening process, long development cycles, and difficulty in simultaneously achieving high activity and high stability. Establishing a directional correlation between doping parameters and electronic structure and catalytic performance, enabling the rational design of non-metallic catalysts, will provide crucial support for the low-cost, large-scale application of water electrolysis for hydrogen production. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for the targeted design and screening of nitrogen-doped MXene-supported non-precious electrocatalysts for hydrogen fuel cells. This method constructs a series of nitrogen-doped N / C ratio electrocatalyst models using Ti3C2O2MXene as a carrier, and combines thermodynamic stability and catalytic activity as two major indicators for screening, effectively shortening the research and development cycle and solving the problem of the difficulty in simultaneously achieving activity and stability in traditional non-metallic catalysts.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a method for the directional design and screening of nitrogen-doped MXene-supported non-noble electrocatalysts for hydrogen fuel cells, characterized in that the directional design and screening method includes the following steps: Step 1: Using Ti3C2O2MXene as a support, nitrogen atoms were selected for doping through lattice carbon sites to construct a series of N / C ratio electrocatalyst models; Step 2: Perform thermodynamic stability and catalytic activity analysis on the series of N / C ratio electrocatalyst models constructed in Step 1, and screen out the electrocatalyst model with the best stability and activity to obtain the nitrogen-doped MXene supported non-noble electrocatalyst.

[0006] This invention selects Ti3C2O2MXene as a carrier, allowing the surface -O functional groups to form highly efficient "O→electron→Ti" transfer channels. The metallic conductivity and structural stability are superior to Ti3C2MXene terminated with -F / -OH groups. Furthermore, because the Ti-3d orbitals are E... F The main contributor to electronic states near the Fermi level is Ti3C2O2MXene. By doping Ti3C2O2MXene with nitrogen atoms, the density of electronic states of Ti-3d orbitals can be significantly increased, forming an "electron library" that promotes H adsorption.

[0007] The above-mentioned method for the directional design and screening of nitrogen-doped MXene supported non-precious electrocatalysts for hydrogen fuel cells is characterized in that, in the series of N / C ratio electrocatalyst models described in step one, the number of N atoms accounts for 5.5% to 100% of the total number of N and C atoms.

[0008] The above-mentioned method for the directional design and screening of nitrogen-doped MXene supported non-noble electrocatalysts for hydrogen fuel cells is characterized in that the screening method in step two is: calculating E using first-principles calculations. form and ΔG H* According to E form <0eV and |ΔG H* By excluding systems with lattice distortion and sluggish HER kinetics under the condition of |≤0.10eV, the electrocatalyst model with optimal stability and activity was selected.

[0009] This invention utilizes E form and ΔG H* The optimal N / C doping ratio range was determined through screening, ensuring that the selected electrocatalyst model balances stability and catalytic activity; specifically, this was achieved through 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); through E form Controlling the thermodynamic stability of the electrocatalyst model, when E form A negative value indicates that the system can form spontaneously; and based on the electrocatalyst model structure generated by VASP software, electrocatalyst models with obvious distortion are screened out. Combined with the moderate covalent effect of Ti-N bonds, it is ensured that the electrocatalyst has no significant activity decay during long-term HER.

[0010] The above-mentioned method for the directional design and screening of nitrogen-doped MXene-supported non-precious electrocatalysts for hydrogen fuel cells is characterized by verifying the electrocatalyst model with optimal stability and activity described in step two to obtain nitrogen-doped MXene-supported non-precious electrocatalysts.

[0011] The above-mentioned method for the directional design and screening of nitrogen-doped MXene supported non-precious electrocatalysts for hydrogen fuel cells is characterized by the following verification method: obtaining the electron transfer amounts of Ti and O atoms through Bader charge analysis, obtaining the electronic state density of Ti-3d orbitals through DOS analysis, and characterizing the Ti-N bond strength through COHP analysis, thereby comprehensively verifying the HER activity.

[0012] This invention verifies the HER activity of the electrocatalyst using Bader charge analysis, DOS (density of states) analysis, and COHP (Hamiton configuration) analysis. Specifically, Bader charge analysis can obtain the electron transfer amounts of Ti and O atoms, and the electron transfer amount of Ti atoms is controlled at 0.53. ~0.80 During this process, excessive electron accumulation leading to overly strong H adsorption can be avoided, thus optimizing the HER reaction kinetics. When a directional electron transfer channel of "Ti→N→O" is formed, the H adsorption energy is optimized. The Ti-3d orbital electronic density of states (including total and partial densities of states) is obtained through DOS analysis. The Ti-3d orbital electronic density of states is related to ΔG. H* There is a positive correlation; the greater the density of electronic states in the Ti-3d orbitals, the greater ΔG. H* The closer to 0 eV; the stronger the Ti-N bond is, the better, as the bonding orbitals of the Ti-N bond approach 0 eV; COHP analysis is used to characterize the Ti-N bond strength. F When the following conditions are met, the active site stability can be ensured and excessive H adsorption can be avoided, provided that the antibonding orbitals are not significantly occupied and the bond energies are moderate.

[0013] The above-mentioned method for the directional design and screening of nitrogen-doped MXene-supported non-precious electrocatalysts for hydrogen fuel cells is characterized in that, in step two, the nitrogen-doped MXene-supported non-precious electrocatalysts form dispersed Ti-N bonds, with a rate-limiting free energy barrier of <0.05 eV and an overpotential of less than 0.1 V.

[0014] Compared with the prior art, the present invention has the following advantages: 1. This invention uses Ti3C2O2MXene with optimized surface functional groups as a carrier to ensure basic conductivity and structural stability. It also achieves precise control of nitrogen doping sites and ratios through lattice carbon substitution, constructing a series of N / C ratio electrocatalyst models. Then, by combining thermodynamic stability and catalytic activity, the optimal active sites and doping ranges are screened, thereby selecting an electrocatalyst model that balances stability and catalytic activity, effectively shortening the electrocatalyst development cycle.

[0015] 2. This invention optimizes the support, controls the nitrogen doping ratio and doping sites in the catalyst model, and combines E... form and ΔG H* Screening was conducted, and catalytic performance was verified through Bader charge analysis, DOS analysis, and COHP analysis to ensure the stability of the screening results. A complete directional design and screening system was constructed from the four dimensions of "support optimization, doping regulation, structure-activity relationship, and stability assurance" to achieve precise design of electrocatalysts. The final product possesses |ΔG H* With advantages such as ≤0.10eV, excellent electronic conductivity, and high active site density, it exhibits highly efficient catalytic performance in water electrolysis for hydrogen production; moreover, its cost is reduced by more than 80% compared to precious metal catalysts, providing a low-cost and efficient electrocatalyst for green hydrogen energy production and carbon neutrality.

[0016] 3. This invention also reveals the electronic state density of the Ti-3d orbital in the electrocatalyst and the relationship between ΔG H* The correlation between these parameters contributes new parameters to the design and screening of electrocatalysts.

[0017] 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

[0018] Figure 1 This is a structural diagram of the 18 doping models in Embodiment 1 of the present invention.

[0019] Figure 2 E represents the 18 doping models in Embodiment 1 of this invention. form Result image.

[0020] Figure 3 ΔG is the result of 18 doping models in Embodiment 1 of this invention. H* Result image.

[0021] Figure 4 The diagram shows the electronic density of states results for 18 doping models in Example 1 of this invention.

[0022] Figure 5The image shows the COHP curves of the Ti-N bond in Example 1 of this invention, where the number of N atoms accounts for 22.2%, 66.6%, 72.2%, and 94.4% of the total number of N and C atoms, respectively. Detailed Implementation

[0023] Example 1 The targeted design and screening method in this embodiment includes the following steps: Step 1: Using Ti3C2O2MXene as a substrate, a 3×3×1 supercell model was constructed using density functional theory (DFT). Nitrogen atoms were then progressively replaced with C atoms in the lattice using VASP software to generate a supercell model. Figure 1 The 18 doping models shown range from 5.5% to 100% in terms of the percentage of N atoms to the total number of N and C atoms (the percentage of N atoms to the total number of N and C atoms is denoted as the N / C ratio, and the specific N / C ratios are: 5.5%, 11.1%, 16.6%, 22.2%, 27.7%, 33.3%, 38.8%, 44.4%, 50.0%, 55.5%, 61.1%, 66.6%, 72.2%, 77.7%, 83.3%, 88.8%, 94.4%, and 100%). Each doping model randomly generates 20 initial configurations, and the 17 configurations with the lowest energy for each doping model are selected for subsequent analysis to ensure statistical independence and structural reliability. Step 2: Calculate E for different N / C ratio configurations form The result is as follows Figure 2 As shown, E for all configurations form All values ​​are negative, indicating that the thermodynamics is stable. Calculate ΔG for different N / C ratio configurations H* The result is as follows Figure 3 As shown: When the N / C ratio is 5.5%~11.1%, ΔG H* A large absolute value (>0.15 eV) indicates insufficient activity; when the N / C ratio is 16.6%~22.2%, the dispersed Ti-N bond regulates the electron distribution of the Ti-3d orbitals, ΔG H* The voltage dropped to -0.09 eV to -0.10 eV, close to the ideal value; the N / C ratio was 66.6% to 72.2%, although ΔG H* It can reach -0.02 eV, but lattice stress causes structural distortion (due to...). Figure 1 It can be seen that when the N / C ratio is 94.4%~100%, ΔG H* The value rebounded to positive values, but the catalytic activity decreased. Combined with ΔG H* and E form The electrocatalyst model with an N / C ratio of 22.2% was selected as having the best stability and activity. The electrocatalyst model with an N / C ratio of 22.2% was validated: (1) Using Bader charge analysis, the amount of electrons transferred from Ti atoms increased from 0.53% to 0.53% of the original Ti3C2O2MXene. Increased to 0.80 The number of electrons gained by the O atom increased from 0.03 Increased to 0.06 (2) Using DOS analysis, Ti-3d and N-2p orbitals undergo strong hybridization in the range of -5eV to 0eV, enhancing electron delocalization and making the H adsorption-desorption kinetics of the electrocatalyst model match the requirements of HER; (3) Using COHP analysis to characterize the Ti-N bond strength, the bonding orbitals of Ti-N bonds are in the range of E F The following are fully occupied, with no obvious occupation of antibonding orbitals and moderate bond energy (|ICOHP|=1.1363), indicating that the active sites of this electrocatalyst model are stable and avoid excessive H adsorption; finally, a nitrogen-doped MXene supported non-noble electrocatalyst with an N / C ratio of 22.2% was obtained.

[0024] Upon testing, the nitrogen-doped MXene supported non-precious electrocatalyst obtained in this embodiment forms dispersed Ti-N bonds, has a rate-limiting step free energy barrier of <0.05 eV, and an overpotential of less than 0.1 V, and exhibits highly efficient catalytic performance in water electrolysis for hydrogen production.

[0025] The structures of the 18 doping models constructed in step one of this embodiment are as follows: Figure 1 As shown (top view above, front view below, brown spheres - C atoms, blue spheres - N atoms, gray spheres - Ti atoms, red spheres - O atoms), when the N / C ratio is 16.6% and 22.2%, N atoms are distributed in a monolayer; when the N / C ratio is >60%, N atoms begin to replace the lower layer of C atoms, accompanied by local lattice distortion. Therefore, the lattice of the model is stable when the N / C ratio is 16.6% and 22.2%. In comparison, the lattice of the model is more stable when the N / C ratio is 22.2%, further verifying the accuracy of the screening in this embodiment. The total density of states (TDOS) and partial density of states (PDOS) of these 18 doping models are both derived from... Figure 4 It can be seen that all doping models are in E F The presence of a significant density of electronic states at this point proves that the metallic conductivity is preserved; PDOS shows that the Ti-3d orbital is an E F N doping, a major contributor to nearby electronic states, can significantly increase the electronic state density of Ti-3d orbitals, forming an electron pool that promotes H adsorption. COHP curves of the doped Ti-N bond are shown below. Figure 5 As shown, where, Figure 5(a) has an N / C ratio of 22.2%. Figure 5 (b) has an N / C ratio of 66.6%. Figure 5 (d) has an N / C ratio of 72.2%. Figure 5 (c) has an N / C ratio of 94.4%. When the N / C ratio is 22.2%, the Ti-N bond length is 2.20 Å, and |ICOHP| = 1.1363, indicating moderate covalent interaction. When the N / C ratio is 66.6% and 72.2%, the bond length shortens to 2.16 Å~2.17 Å, and |ICOHP| > 1.24, indicating enhanced covalent interaction accompanied by lattice stress. When the N / C ratio is 94.4%, the bond length shortens to 2.14 Å, and |ICOHP| = 1.3058. Excessive covalent interaction leads to the occupation of antibonding orbitals, and the excessively strong bond energy makes it difficult for H to desorb, reducing catalytic stability. In summary, through structural, DOS, and COHP analyses of various doping models, the nitrogen-doped MXene-supported non-noble electrocatalyst selected in this embodiment is further verified as the optimal model in terms of stability and catalytic activity, thus demonstrating the reliability of the directional design and screening method of this invention.

[0026] Comparative Example 1 This comparative example generates an electrocatalyst model by gradually replacing nitrogen atoms through surface oxygen functional group sites.

[0027] ΔG was calculated using DFT for this comparative electrocatalyst model. H* The range is -0.25eV to -0.30eV, |ΔG H* The |ΔG is significantly larger than that of the doping model with lattice carbon site substitution in Example 1. H* Therefore, the lattice carbon site doping model is closer to the ideal value, indicating the correctness of using lattice carbon sites as doping sites in this invention.

[0028] 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 MXene-supported non-precious electrocatalysts for hydrogen fuel cells, characterized in that, This targeted design and screening method includes the following steps: Step 1: Using Ti3C2O2 MXene as a support, nitrogen atoms were selected for doping through lattice carbon sites to construct a series of N / C ratio electrocatalyst models; Step 2: Perform thermodynamic stability and catalytic activity analysis on the series of N / C ratio electrocatalyst models constructed in Step 1, and screen out the electrocatalyst model with the best stability and activity to obtain the nitrogen-doped MXene supported non-noble electrocatalyst.

2. The method for directional design and screening of nitrogen-doped MXene-supported non-precious electrocatalysts for hydrogen fuel cells according to claim 1, characterized in that, In the series of N / C ratio electrocatalyst models described in step one, the number of N atoms accounts for 5.5% to 100% of the total number of N and C atoms.

3. The method for directional design and screening of nitrogen-doped MXene-supported non-precious electrocatalysts for hydrogen fuel cells according to claim 1, characterized in that, The screening method described in step two is as follows: E is calculated using first-principles calculations. form and ΔG H* According to E form <0eV and |ΔG H* By excluding systems with lattice distortion and sluggish HER kinetics under the condition of |≤0.10eV, the electrocatalyst model with optimal stability and activity was selected.

4. The method for directional design and screening of nitrogen-doped MXene-supported non-precious electrocatalysts for hydrogen fuel cells according to claim 1, characterized in that, The electrocatalyst model with optimal stability and activity described in step two was verified to obtain a nitrogen-doped MXene-supported non-noble electrocatalyst.

5. The method for directional design and screening of nitrogen-doped MXene-supported non-precious electrocatalysts for hydrogen fuel cells according to claim 4, characterized in that, The verification method is as follows: the electron transfer amount of Ti and O atoms is obtained by Bader charge analysis, the electronic state density of Ti-3d orbitals is obtained by DOS analysis, and the Ti-N bond strength is characterized by COHP analysis, so as to comprehensively verify the HER activity.

6. The method for directional design and screening of nitrogen-doped MXene-supported non-precious electrocatalysts for hydrogen fuel cells according to claim 1, characterized in that, In step two, the nitrogen-doped MXene-supported non-noble electrocatalyst forms dispersed Ti-N bonds, with a rate-limiting free energy barrier of <0.05 eV and an overpotential of less than 0.1 V.

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