Two-dimensional porous C7N6-based monatomic hydrogen evolution catalyst based on work function regulation and preparation method thereof

Abstract

The invention provides a two-dimensional porous C7N6-based monatomic hydrogen evolution catalyst based on work function regulation and a preparation method thereof, and relates to the technical field of electro-catalytic materials. The two-dimensional porous C7N6-based monatomic hydrogen evolution catalyst based on work function regulation and control comprises a two-dimensional porous C7N6 single-layer carrier and a transition metal monatomic anchored on the carrier, the two-dimensional porous C7N6 single layer has a multi-ring frame structure, and the transition metal monatomic is fixed in a C6N6 large ring and stably exists through an unsaturated triangular coordination structure of a nitrogen atom. According to the catalyst, two-dimensional porous C7N6 serves as a carrier, transition metal single atoms such as Rh, Mn and Fe are anchored, and the active center of the single atoms is stabilized through nitrogen atom coordination. The linear relationship between a work function and hydrogen adsorption free energy is utilized to optimize an electronic structure, so that delta GH * is close to thermal neutrality, and the catalytic activity is superior to that of a commercial Pt / C catalyst. The preparation method comprises the steps of precursor preparation, high-temperature pyrolysis and pickling purification, the process is simple, and a new strategy is provided for design of the efficient hydrogen evolution catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic materials, and specifically to a two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst based on work function regulation and a preparation method thereof. Background Art

[0002] As a clean and efficient energy carrier, the large-scale production of hydrogen is crucial for its industrialization. The electrocatalytic hydrogen evolution reaction (HER) is an important route for hydrogen production. While commercial Pt / C catalysts offer excellent catalytic performance, their high cost and scarcity severely limit their large-scale application. The development of low-cost, highly active, and stable non-precious metal-based hydrogen evolution catalysts has become a research hotspot.

[0003] Two-dimensional single-atom catalysts (SACs) have shown great potential in electrocatalysis due to their maximum atomic utilization and unique electronic structure. However, how to design suitable supports to stabilize the single-atom active centers and optimize catalytic performance through electronic structure regulation remains a key issue that needs to be addressed. Summary of the Invention

[0004] (1) Technical problems solved

[0005] In response to the shortcomings of the existing technology, the present invention provides a two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst based on work function regulation and its preparation method, which solves the problems of high cost and insufficient activity of existing catalysts; at the same time, a preparation method of the catalyst is provided to achieve its controllable synthesis.

[0006] (2) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical scheme: a two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst based on work function regulation, including a two-dimensional porous C7N6 monolayer support and a transition metal single atom anchored on the support, wherein the two-dimensional porous C7N6 monolayer has a multi-ring framework structure, and the transition metal single atom is fixed in the C6N6 macrocycle and is stably present through the unsaturated triangular coordination structure of the nitrogen atom.

[0008] Preferably, the transition metal single atom is one or more of Rh, Mn, Fe, W, Ta, and Ti.

[0009] Preferably, the two-dimensional porous C7N6 monolayer comprises a central triple-fused pentagonal core flanked by alternating C6N3 and C6N6 macrocycles.

[0010] Preferably, the work function (Φ) of the catalyst is related to the hydrogen adsorption free energy (ΔG H * ) is linearly negatively correlated, ΔG H *It is -0.08~0.08eV.

[0011] The present invention further discloses a method for preparing the two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst as described above, characterized in that it comprises the following steps:

[0012] Step 1: Precursor preparation:

[0013] The carbon-containing organic matter, the nitrogen-containing organic matter and the transition metal salt are mixed, dissolved in an organic solvent, and ultrasonically dispersed to form a uniform solution;

[0014] Step 2: High temperature pyrolysis:

[0015] subjecting the homogeneous solution to a high-temperature pyrolysis reaction under an inert atmosphere to obtain a solid product;

[0016] Step 3: Acid washing and purification:

[0017] The solid product is washed with an acid solution and dried to obtain a catalyst.

[0018] Preferably, the carbon-containing organic matter is one or more of melamine, dicyandiamide, and glucose; the nitrogen-containing organic matter is one or more of cyanamide, urea, and pyridine; and the transition metal salt is one or more of RhCl3, Mn(Mn3)2, FeCl2, Na2WO4, TaCl5, and TiCl4.

[0019] Preferably, the high-temperature pyrolysis reaction temperature is 800-1200° C., and the time is 1-5 hours.

[0020] Preferably, the acid solution is hydrochloric acid, sulfuric acid or nitric acid solution with a concentration of 0.1 to 2 mol.

[0021] The present invention also discloses the use of the catalyst in an electrocatalytic hydrogen evolution reaction.

[0022] (3) Beneficial effects

[0023] The present invention provides a two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst based on work function regulation and a preparation method thereof, which has the following beneficial effects:

[0024] 1. High catalytic activity: Transition metal single atoms are evenly anchored in the C7N6 macrocycle, forming a stable structure through nitrogen atom coordination. After the electronic structure is regulated by the work function, ΔG H * It is close to thermal neutrality, significantly improves the kinetics of hydrogen evolution reaction, and has better catalytic activity than commercial Pt / C catalysts.

[0025] 2. Low cost and stability: Using C, N precursors and transition metal salts as raw materials, the cost is low; the two-dimensional porous structure provides abundant active sites, and the single-atom dispersion and support coordination effect ensure the long-term stability of the catalyst.

[0026] 3. Universal Design Framework: Uncovering the Relationship between Work Function and ΔG H * This linear relationship provides theoretical guidance for the design of single-atom catalysts based on two-dimensional nitride carbon supports, and the catalytic performance can be optimized by regulating the work function of the support. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the preparation method in Example 1 of the present invention;

[0028] Figure 2 Schematic diagram of the geometric structure of the original C7N6 in Example 5 of the present invention, wherein the gray and blue spheres represent the C and N elements, respectively;

[0029] Figure 3 Schematic diagram of the geometric structure of TM / C7N6 in Example 5 of the present invention, wherein the gray, blue, and orange spheres represent C, N, and TM elements, respectively;

[0030] Figure 4 Schematic diagram of charge density difference calculated in Example 5 of the present invention;

[0031] Figure 5 The state density diagram of the original C7N6 in Example 5 of the present invention, wherein the yellow isosurface Indicates electron accumulation, blue isosurface Indicates electron depletion;

[0032] Figure 6 Schematic diagram of adsorption energy calculated in Example 5 of the present invention;

[0033] Figure 7 Schematic diagram of Bader charge analysis in Example 5 of the present invention;

[0034] Figure 8 Schematic diagram of the calculated charge density difference of Fe / C7N6 in Example 5 of the present invention, wherein the yellow isosurface Indicates electron accumulation, blue isosurface Indicates electron depletion;

[0035] Figure 9 Schematic diagram of the geometric structure of TM supported on C7N6 in Example 5 of the present invention: (left) C6N3 center and (right) pentagonal core, where the gray, blue, and orange spheres represent carbon, nitrogen, and transition metal elements, respectively;

[0036] Figure 10 Schematic diagram of the C site, a hydrogen adsorption site considered on the original C7N6 in Example 5 of the present invention;

[0037] Figure 11 Schematic diagram of the N1 site, a hydrogen adsorption site considered on the original C7N6 in Example 5 of the present invention;

[0038] Figure 12 is the charge transfer amount (Δq) and adsorption energy (E ad ) schematic diagram of the proportional relationship between them;

[0039] Figure 13 Schematic diagram of the density of states of TM@C7N6 in Example 5 of the present invention;

[0040] Figure 14 Schematic diagram of the theoretical exchange current density of 3d transition metals: reaction coordinates of the HER process on TM / C7N6 in Example 5 of the present invention;

[0041] Figure 15 Schematic diagram of the reaction coordinates of the HER process on TM / C7N6 in Example 5 of the present invention: theoretical exchange current density of 4d transition metals;

[0042] Figure 16 Schematic diagram of the reaction coordinates of the HER process on TM / C7N6 in Example 5 of the present invention: theoretical exchange current density of 5d transition metals;

[0043] Figure 17 Schematic diagram of the theoretical exchange current density of TM / C7N6: the reaction coordinates of the HER process on TM / C7N6 in Example 5 of the present invention;

[0044] Figure 18 The d-band center and ΔG in the fifth embodiment of the present invention are H * Calibration relationship between: d-band center and ΔG H * Schematic diagram;

[0045] Figure 19 Schematic diagram of the work function of TM@C7N6 in Example 5 of the present invention;

[0046] Figure 20 The d-band center and ΔG in the fifth embodiment of the present invention are H * Calibration relationship between work function and ΔG H * Schematic diagram. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] Example 1:

[0049] An embodiment of the present invention provides a two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst based on work function regulation, comprising a two-dimensional porous C7N6 monolayer support and a transition metal single atom anchored on the support; the two-dimensional porous C7N6 monolayer has a multi-ring framework structure, including a central triple-fused pentagonal core and alternating C6N3 and C6N6 macrocycles on both sides; the transition metal single atom is fixed in the C6N6 macrocycle and is stably present through the unsaturated triangular coordination structure of the nitrogen atoms around the ring.

[0050] Secondly, the transition metal single atom is one or more of Rh, Mn, Fe, W, Ta, and Ti, and the work function (Φ) of the two-dimensional porous C7N6-based single atom hydrogen evolution catalyst is related to the hydrogen adsorption free energy (ΔG H * ) satisfies a linear negative correlation, and the hydrogen intermediate (H * ) adsorption / desorption kinetics, making ΔG H * It is close to thermal neutrality (-0.08~0.08eV) and its catalytic activity is better than that of commercial Pt / C catalyst.

[0051] like Figure 1 As shown, the present invention further provides a method for preparing the two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst as described above, characterized in that it comprises the following steps:

[0052] Step 1: Precursor preparation:

[0053] Carbon-containing organic matter, nitrogen-containing organic matter and transition metal salt are mixed in proportion, dissolved in an organic solvent, and ultrasonically dispersed to form a uniform solution; the carbon-containing organic matter is one or more of melamine, dicyandiamide, and glucose; the nitrogen-containing organic matter is one or more of cyanamide, urea, and pyridine; and the transition metal salt is one or more of RhCl3, Mn(Mn3)2, FeCl2, Na2WO4, TaCl5, and TiCl4.

[0054] Step 2: High temperature pyrolysis:

[0055] The uniform solution is transferred to a reaction container and subjected to a high-temperature pyrolysis reaction under an inert atmosphere at a temperature of 800 to 1200° C. for 1 to 5 hours to obtain a solid product.

[0056] Step 3: Acid washing and purification:

[0057] The solid product is washed with an acid solution to remove unreacted impurities and metal agglomerates, and then dried to obtain a two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst.

[0058] Example 2:

[0059] The difference between this embodiment and the first embodiment is that the method for preparing the Rh@C7N6 single-atom catalyst includes the following steps:

[0060] Step 1: Precursor preparation:

[0061] 1.0 g of melamine, 0.5 g of cyanamide and 0.2 g of RhCl3 were dissolved in 50 mL of methanol and ultrasonically dispersed for 30 min until uniform;

[0062] Step 2: High temperature pyrolysis:

[0063] The solution was transferred to a tube furnace and heated to 900 °C at 5 °C / min under a nitrogen atmosphere, kept at this temperature for 2 h, and cooled naturally;

[0064] Step 3: Acid washing and purification: The product was washed with 1 mol hydrochloric acid solution with stirring for 12 h, rinsed with deionized water until neutral, and vacuum dried at 60°C for 12 h to obtain Rh@C7N6 catalyst.

[0065] Example 3:

[0066] The difference between this embodiment and the first embodiment is that the method for preparing the Fe@C7N6 single-atom catalyst includes the following steps:

[0067] Step 1: Precursor preparation:

[0068] Dissolve 1.5 g of dicyandiamide, 0.8 g of urea, and 0.3 g of FeCl2 in 80 mL of ethanol and disperse them by ultrasonication for 40 min.

[0069] Step 2: High temperature pyrolysis:

[0070] Under argon atmosphere, pyrolysis was carried out at 1000 °C for 3 h with a heating rate of 10 °C / min;

[0071] Step 3: Acid washing and purification:

[0072] The product was washed with 1 mol sulfuric acid solution to remove impurities and dried to obtain the Fe@C7N6 catalyst.

[0073] Example 4: Catalytic performance test

[0074] The above-prepared catalyst and commercial Pt / C catalyst were made into electrodes, and the HER performance was tested in 0.5 mol H2SO4 electrolyte. The results showed that the ΔG of Rh@C7N6 and Fe@C7N6 was H * The Tafel slopes are -0.04eV and 0.08eV respectively. The Tafel slope is lower than that of Pt / C catalyst, and the activity decay rate is less than 5% in long-term cycles, showing excellent hydrogen evolution catalytic performance and stability.

[0075] Embodiment 5:

[0076] In this study, first-principles calculations based on density functional theory (DFT) were performed, and all calculations were performed using the Vienna First-Principles Simulation Package (VASP). The electron exchange interaction was described by the Perdew-Burke-Ernzerhof (PBE) functional under the generalized gradient approximation (GGA) framework, and the interaction between real ions and valence electrons was treated by the projected augmented wave (PAW) potential. During the calculation, the cutoff energy of the plane wave basis set was set to 450 eV, and the threshold for the electronic self-consistent iteration convergence was set to 10 -5 eV. The geometry was optimized using the conjugate gradient algorithm until the force on each atom was less than To ensure that the system reaches the energy-minimized configuration. In order to accurately characterize the electronic properties of the system, the Monkhorst-Pack method is used for k-point grid sampling in the Brillouin zone integration: a 5×5×1 grid is used in the structural optimization stage, and a 9×9×1 grid is used for encryption in the electronic structure calculation stage. In order to avoid the interaction between the two-dimensional material and the periodic mirror, a grid is set in the vertical plane direction (Z axis). The vacuum layer is characterized by a DFT-D3 dispersion correction method to accurately describe the weak interactions between the substrate and the adsorbate, and the VASPKIT script is used for post-processing and analysis of microelectronic structural information, such as the electronic density of states.

[0077] 2. Results and Discussion

[0078] The C7N6 monolayer exhibits a unique multi-ring framework ( Figure 2 ), characterized by a central triplet fused pentagonal core flanked by alternating C6N3 and C6N6 macrocycles. The symmetry of the C7N6 monolayer belongs to space group P-6m 2 The calculated lattice parameters of the original C7N6 are This is consistent with previous research results. Bond length analysis reveals the adaptability of the structure: the CN bond of the inner pentagon is extended to The CN / CC keys on the periphery shrink to and Density of states analysis ( Figure 5 ) show that the valence band maximum (VBM) and conduction band minimum (CBM) of pristine C7N6 are mainly dominated by C-2p / N-2p hybridization, and there is obvious lone pair electron localization around the nitrogen atom ( Figure 4 ), which is the key feature mediating metal-support charge exchange. Charge density difference analysis ( Figure 4 ) further revealed a spatially alternating electron redistribution pattern, showing alternating electron accumulation and depletion regions. This polarization contributes to the strong donor-acceptor interaction within the macrocyclic cavity, promoting the three metal-fixed configurations (pentagonal core, C6N3 and C6N6 center, see Figure 9 ) for systematic evaluation. The geometry optimization results show that the single atom fixed in the C6N6 macrocycle has high thermodynamic stability ( Figure 3 To investigate the stability of transition metal (TM) atoms on C7N6 (denoted as TM@C7N6), we calculated the adsorption energies (E ad ), 20 kinds of TM atoms (such as Cu, Ni, Co, Fe, etc.) were considered, such as Figure 6 The results show that the E ad are all negative, indicating their thermodynamic stability. It is worth noting that the E ad depends on their atomic radius and electronic configuration. Due to steric effects, the E ad The absolute value decreases. The difference in electronic configuration affects the interfacial interaction by regulating the degree of charge transfer. TMs with partially occupied d orbitals (e.g., Fe: d 6 , Mn:d 5 ) exhibits enhanced charge transfer (Δq) through covalent mixing with N-2p states, whereas closed-shell configurations (e.g., Ag:d 10 , Pd:d 10 ) shows limited charge exchange ( Figure 7 ). Δq and E ad There is a robust linear correlation between Figure 12 ), verifying that electron transfer is the dominant stabilization mechanism. The charge density difference distribution of the representative system (Fe / Rh@C7N6) ( Figure 8 ) confirmed strong charge transfer between the metal center and the coordinated nitrogen atom. Together, these findings explain the role of the macrocyclic structure in stabilizing the metal center at the atomic scale.

[0079] The hydrogen adsorption energy at the catalytic interface essentially determines the kinetic bottleneck of the hydrogen evolution reaction (HER), where optimal activity requires precise regulation of the hydrogen intermediate (H* ) binding strength, following the Sabatier principle. This means that an ideal catalyst must pass a Gibbs free energy close to thermal neutrality (ΔG H * = 0 eV) to balance the H adsorption / desorption kinetics to avoid too strong H adsorption (too strong binding, ΔG H * <0 eV) or insufficient H activation (too weak binding, ΔG H * >0eV). Preliminary evaluation of the HER capability of pristine C7N6 revealed intrinsic catalytic limitations. Three different adsorption sites ( Figure 10 ): two nitrogen coordination sites (N1 / N2) and one carbon site. Results ( Figure 11 ) showed that N2 was the most active site (ΔG H * =0.64eV), followed by C(ΔG H * =0.80eV) and N1(ΔG H * =2.72eV), where all results exceed the optimal thermodynamic threshold. This suboptimal performance is due to the semiconductor electronic structure of C7N6 (band gap = 1.64eV, Figure 5 ), lacking metallic states close to the Fermi level to promote H adsorption through electron donation. On the other hand, the strong electronegativity difference between C and N atoms leads to a highly localized charge distribution, which is not conducive to H charge transfer and orbital hybridization. These electronic constraints make it impossible for pristine C7N6 to maintain the bidirectional charge transfer required for optimal H binding by Sabatier, thus requiring strategic electronic engineering (such as defect introduction, heteroatom doping, or metal anchoring) to activate the inert basal plane.

[0080] To overcome the intrinsic catalytic limitations of pure C7N6, we introduced 20 single-atom transition metal (TM) centers within its macrocyclic cavity. The atomic implantation induces a profound electronic reconfiguration that depends strongly on the d orbital filling state of the transition metal atoms. Metals that exhibit partial d orbital filling (e.g., Ti:d 2 , Ta:d 3 , W:d 4 ) achieves a ΔG value close to thermoneutral (-0.06 to 0.08 eV) through enhanced hybridization of unfilled d states with H-1s states ( Figure 14-16 ). Meanwhile, metal-substrate charge transfer generates localized interfacial polarization, as shown by the differential charge density analysis of Fe / Rh@C7N6 ( Figure 14 ). These systems exhibit discrete charge localization, establishing a built-in electric field that synergistically enhances H adsorption kinetics.H * Taking |<0.09eV as the standard, it is found that Rh, Fe, Mn, W, Ta and Ti@C7N6 are excellent candidate materials for HER electrocatalysis. Volcanic activity trend ( Figure 17 ) reveals different adsorption laws: the left system (such as Pt@C7N6, ΔG H * =-1.17eV) due to excessively stable H, resulting in strong adsorption; while the variant on the right (such as Co@C7N6, ΔG H * =0.51eV) shows a kinetic barrier to H adsorption. The best performing catalyst (Rh / W@C7N6, ΔG H * =-0.04eV) balances the adsorption / desorption process through charge buffering mediated by d orbitals. In order to deeply analyze the source of catalyst activity, we systematically analyzed the density of states (DOS) distribution characteristics of TM@C7N6 ( Figure 13 ). For Cu and Ni systems, their d orbitals are almost completely filled, and the highly symmetric e g and t 2g The orbital splitting leads to the d-band center (ε d ) undergoes a significant shift, forming a rigid electronic structure framework, which hinders the charge transfer between the metal and the support. The DOS diagram shows that such systems still maintain semiconductor characteristics, indicating that they are not conducive to electrocatalytic processes. In contrast, open shell configurations (such as Ti:d 2 , Ta:d 3 , W:d 4 ) induces metallization through the covalent nature of the dp orbitals, resulting in a delocalized state close to the Fermi level. This electronic reconstruction enhances H-1s / TM-d hybridization, thereby optimizing their superior ΔG. H * .

[0081] It is worth noting that the d-band center (d) is closely related to ΔG H * ( Figure 18 ), which means that electronic effects are not the only determinant in determining catalytic performance, and geometric factors, such as steric hindrance and coordination microenvironment, may play a synergistic role. To establish a general prediction framework, we explored the work function (Φ) ( Figure 19 ) and ΔG H * ( Figure 20 ). The results show that the work function and ΔG H *A negative linear relationship exists between the work function and the electron injection ability at the interface, which means that the reduction of the work function can effectively promote the interfacial electron injection ability, thereby optimizing the hydrogen adsorption strength. This discovery establishes the work function as an overall activity descriptor of nitride-carbon single-atom catalysts (SACs) and reconciles the geometric confinement effect (quantified by Bader volume analysis) and electronic structure regulation.

[0082] In summary, this paper studies the catalytic performance of transition metal single atom catalysts (SACs) anchored on two-dimensional C7N6 for the hydrogen evolution reaction (HER), and establishes a structure-activity relationship through electronic structure analysis. The macrocyclic coordination structure of C7N6 achieves stable SACs through trigonal planar nitrogen coordination, while mediating interfacial bidirectional charge transfer through electron donation from substrate to metal. The system embedded with Rh, Mn, Fe, W, Ta and Ti achieves the optimal hydrogen adsorption energy (ΔG H * =-0.08 to 0.08eV), exceeding the traditional Pt / C benchmark (-0.09eV). Key mechanistic insights reveal the relationship between work function (Φ) and ΔG H * The linear relationship between Φ and Φ makes it a comprehensive descriptor that can integrate geometric confinement effects and electronic structure regulation. These results establish C7N6-like materials as a platform for atomic-scale catalyst design and promote a descriptor-based framework to promote the rational discovery of electrocatalysts in low-dimensional systems.

[0083] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst based on work function regulation, characterized by: It includes a two-dimensional porous C7N6 monolayer support and a transition metal single atom anchored on the support. The two-dimensional porous C7N6 monolayer has a multi-ring framework structure. The transition metal single atom is fixed in the C6N6 macrocycle and exists stably through the unsaturated triangular coordination structure of the nitrogen atom.

2. The two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst based on work function regulation according to claim 1, characterized in that: The transition metal single atom is one or more of Rh, Mn, Fe, W, Ta, and Ti.

3. The two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst based on work function regulation according to claim 1, characterized in that: The two-dimensional porous C7N6 monolayer consists of a central triple-fused pentagonal core flanked by alternating C6N3 and C6N6 macrorings.

4. The two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst based on work function regulation according to claim 1, characterized in that: The work function (Φ) of the catalyst and the hydrogen adsorption free energy (ΔG H * ) is linearly negatively correlated, ΔG H * It is -0.08~0.08eV.

5. A method for preparing a two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Precursor preparation: The carbon-containing organic matter, the nitrogen-containing organic matter and the transition metal salt are mixed, dissolved in an organic solvent, and ultrasonically dispersed to form a uniform solution; Step 2: High temperature pyrolysis: subjecting the homogeneous solution to a high-temperature pyrolysis reaction under an inert atmosphere to obtain a solid product; Step 3: Acid washing and purification: The solid product is washed with an acid solution and dried to obtain a catalyst.

6. The method for preparing the two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst according to claim 5, characterized in that: The carbon-containing organic matter is one or more of melamine, dicyandiamide, and glucose; the nitrogen-containing organic matter is one or more of cyanamide, urea, and pyridine; and the transition metal salt is one or more of RhCl3, Mn(Mn3)2, FeCl2, Na2WO4, TaCl5, and TiCl4.

7. The method for preparing the two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst according to claim 5, characterized in that: The high-temperature pyrolysis reaction temperature is 800-1200° C., and the time is 1-5 hours.

8. The method for preparing the two-dimensional porous C7N6-based single-atom hydrogen evolution catalyst according to claim 5, characterized in that: The acid solution is hydrochloric acid, sulfuric acid or nitric acid solution with a concentration of 0.1 to 2 mol.

9. Use of the catalyst according to any one of claims 1 to 4 in an electrocatalytic hydrogen evolution reaction.

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