A bimetallic single-atom catalyst, and a preparation method and application thereof

Abstract

The application discloses a kind of bimetallic single-atom catalyst based on three-dimensional carbon aerogel and its preparation method and application.The bimetallic single-atom catalyst disclosed in the application is based on three-dimensional porous carbon material, and loaded with bimetallic single-atom active ingredients, and has good catalytic activity.It has been verified through experiments that the catalyst disclosed in the application has an oxygen evolution reaction efficiency better than that of commercial RuO2.In addition, the catalyst preparation method disclosed in the application has a simple production process, and the raw materials are cheap and easy to obtain, the reaction conditions are mild and no special equipment is needed, so it has the potential to be applied to large-scale industrial production, and is an effective solution to the problems of Cl ‑ corrosion and efficient oxygen evolution in seawater electrolysis engineering.

Description

Technical Field

[0001] This invention relates to a catalyst, specifically to a bimetallic single-atom catalyst based on three-dimensional carbon aerogel, its preparation method, and its application. Background Technology

[0002] Since the beginning of the 21st century, the world economy has developed rapidly, and at the same time, the demand for fossil fuels has increased. The resulting energy crisis and environmental pollution problems have attracted widespread attention around the world. It can be said that energy and environment are the two major themes facing sustainable development in today's society.

[0003] A key measure to address these issues is the development and utilization of green and renewable energy sources such as solar, wind, and tidal power. However, these renewable energy sources suffer from problems such as large fluctuations in production capacity and intermittency, thus requiring advanced energy conversion and storage technologies for efficient utilization. Among these, water electrolysis for hydrogen production technology, as a green and effective energy conversion and storage method, has received widespread attention and research.

[0004] Water electrolysis technology involves two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. From the product perspective, the hydrogen produced at the cathode can be used in hydrogen fuel cells, making it an ideal energy source for addressing the energy and environmental crises; simultaneously, the high-purity oxygen produced at the anode has wide applications in chemical, medical, and energy fields, possessing significant economic value. However, because the oxygen evolution reaction at the anode is a four-electron-proton coupled reaction, it faces significant kinetic resistance and requires much higher energy. Therefore, water electrolysis technology strongly relies on highly efficient and stable anode OER catalyst materials.

[0005] On the other hand, current water electrolysis technology typically uses purified freshwater (treated with acid or alkalization depending on the process) as raw material, which undoubtedly increases the cost of the process. However, seawater, which accounts for over 96% of the Earth's water resources, is a more suitable raw material for water electrolysis. However, seawater contains a large number of free ions, including Cl-. - It has a low oxidation potential at the anode, which may compete with OER for the reaction, while Cl... - It is highly corrosive and will corrode the electrodes during electrolysis, greatly affecting the lifespan of water electrolysis equipment. Therefore, it is of great significance to develop catalytic materials that can operate stably in seawater and have high catalytic selectivity.

[0006] Currently, most energy and environment-related chemical processes utilize catalysis technology to increase reaction rates or improve the selectivity of reaction products. Among these, metal catalysts hold a significant share due to their superior performance and flexible controllability. With the continuous deepening and refinement of chemical processes, single-atom catalysts (SACs) have become a research hotspot in recent years. These catalysts immobilize active components on a support in an atomically dispersed manner to form heterogeneous catalysts. Because the active components are at the atomic level, they possess advantages such as high activity, good stability, and strong catalytic selectivity. Furthermore, if a second metal component is introduced to prepare a bimetallic single-atom catalyst, its catalytic performance will be further improved.

[0007] Therefore, based on the above advantages, developing an OER catalyst that simultaneously possesses high catalytic activity and corrosion resistance holds promise for solving the problem of Cl in seawater electrolysis engineering. - Effective solutions to problems such as corrosion and efficient oxygen evolution are needed. However, there are few reported methods for preparing bimetallic single-atom catalysts in the literature, and most of these methods are complex, costly, and the activity and stability of the resulting catalysts need to be improved. Therefore, it is particularly important to develop a more efficient, low-cost, and simple method for preparing bimetallic single-atom catalysts. Summary of the Invention

[0008] To address the aforementioned problems, this invention proposes a method for synthesizing high-performance bimetallic single-atom supported carbon aerogel catalysts using supramolecular hydrogels as precursors. This method is simple and easy to implement, yielding catalysts that are low-cost, exhibit excellent catalytic performance, and possess high activity and good selective catalysis (thus avoiding Cl...). - Its characteristics (the influence of the environment) can be used for the catalytic oxygen evolution reaction in seawater.

[0009] A first aspect of the present invention is to provide a bimetallic single-atom catalyst.

[0010] The catalyst uses nitrogen-doped three-dimensional porous carbon aerogel as the matrix material, and loads bimetallic single atoms on the matrix material.

[0011] Among them, bimetals can be selected from any two of Fe, Co, Ni, Cu, Zn, and Ru.

[0012] A second aspect of the present invention is to provide a method for preparing the above-mentioned catalyst, specifically comprising the following steps:

[0013] S1, a suspension of a group consisting of biomass material and pore-forming agent;

[0014] S2, two metal phenanthrene complexes are added sequentially to the suspension to obtain the precursor;

[0015] S3, after drying the precursor, perform a heat treatment operation;

[0016] S4, after removing the pore-forming agent, yields a nitrogen-doped porous carbon aerogel supported by a bimetallic single atom, which is the catalyst described above.

[0017] In this process, through steps S1 and S2, a biomass hydrogel precursor is obtained. The hydrogel is then subjected to thermal treatment and carbonization to obtain a nitrogen-doped three-dimensional carbon aerogel with bimetallic single atoms attached. Finally, the pore-forming agent used as a sacrificial template is removed to obtain a carbon aerogel matrix material with a porous structure.

[0018] Preferably, the biomass material of the present invention includes chitosan, and the pore-forming agent includes nano-sized silica. The silica is preferably 12-25 nm in size, thereby providing sufficient porous structure for the matrix material. Chitosan can also be replaced with lignocellulose.

[0019] More preferably, the mass ratio of chitosan to nano-sized silica is 3:(1-3), and when preparing the suspension, it is preferable to use an acetic acid solution with a volume fraction of 1-5% as a dispersant, and the ratio of chitosan to acetic acid solution is preferably (20-25) mg:1 mL.

[0020] Optionally, before preparing the suspension, the present invention may pre-add conductive components such as carbon black to the acetic acid solution and prepare a stable and uniformly dispersed suspension by means of stirring, vibration, and ultrasound, wherein the ratio of carbon black to acetic acid solution is 2mg:(1-2)mL.

[0021] Preferably, in step S2, the volume ratio of the 1:1 of the two metal phenanthrene complexes is 1:1, and the two metals are any two selected from Fe, Co, Ni, Cu, Zn, and Ru. For example, a certain volume of iron-1,1-phenanthrene complex is first added to the suspension, followed by an equal volume of nickel-1,1-phenanthrene complex, and the mixture is stirred continuously until a hydrogel precursor is obtained.

[0022] More preferably, the total ratio of chitosan to the two o-phenanthroline complexes is 1 mg:(2.5-3) μL.

[0023] In step S3 of this invention, the heat treatment operation for carbonizing the hydrogel is carried out in an inert environment, such as an Ar atmosphere. The optimal heating and cooling rate is 5°C / min. After heating to 460-500°C, the temperature is held for 1-3 hours, and then the temperature is lowered.

[0024] Preferably, in step S4, the method for removing the pore-forming agent is to soak it in a NaOH solution. The NaOH solution can effectively etch away silicon dioxide, thereby forming a porous structure. The specific operation of the NaOH solution treatment can be carried out according to common requirements in the art, for example, using a 0.5 mol / L NaOH solution.

[0025] The final aspect of this invention is to provide the application of the above-described bimetallic single-atom catalyst. The bimetallic single-atom catalyst prepared according to the method of the first aspect of this invention, or the bimetallic single-atom catalyst prepared according to the method of the second aspect of this invention, can be used to catalyze the oxygen evolution reaction.

[0026] Preferably, the catalyst can be used to carry out the catalytic oxygen evolution reaction in alkaline media, such as alkaline seawater.

[0027] The bimetallic single-atom catalyst disclosed in this invention uses a three-dimensional porous carbon material as a matrix and supports a bimetallic single-atom active component. It possesses a variety of unique physical and chemical properties, such as nearly 100% metal atom utilization, abundant coordinated unsaturated atoms, excellent electrical conductivity, high specific surface area, good catalytic selectivity, and structural stability, thus exhibiting ideal catalytic activity. Experimental verification shows that the catalyst disclosed in this invention has a higher oxygen evolution reaction efficiency than commercial RuO2.

[0028] The bimetallic single-atom catalyst disclosed in this invention operates at 10 mA cm⁻¹. -2 The tests were conducted in simulated seawater with 1 mol / L KOH aqueous solution and 1 mol / L KOH and 0.5 mol / L NaCl. The potentials required for water decomposition were 1.556 V and 1.549 V, respectively, and the water decomposition efficiency remained high even after 100 h of stability testing.

[0029] The technical solution of this invention provides a simple production process for preparing nitrogen-doped three-dimensional porous carbon aerogels supported by bimetallic single atoms. The raw materials are inexpensive and readily available, the reaction conditions are mild, and no special equipment is required. Therefore, it has the potential for large-scale industrial production, solving the problem of Cl in seawater electrolysis engineering. - Effective solutions to problems such as corrosion and efficient oxygen evolution. Attached Figure Description

[0030] Figure 1 The image shows a SEM image of the bimetallic single-atom catalyst prepared in Example 2.

[0031] Figure 2 This is a TEM image of the bimetallic single-atom catalyst prepared in Example 2;

[0032] Figure 3This is a high-angle annular dark-field scanning transmission electron microscope image of the bimetallic single-atom catalyst prepared in Example 2;

[0033] Figure 4 The distribution diagram of each element in the bimetallic single-atom catalyst prepared in Example 2 is shown.

[0034] Figure 5 The XRD patterns of the catalysts prepared in Example 2 and Comparative Examples 1-2 are shown below.

[0035] Figure 6 The Raman spectra of the catalysts prepared in Example 2 and Comparative Examples 1-2 are shown below.

[0036] Figure 7 XPS images of the catalysts prepared in Example 2 and Comparative Example 1;

[0037] Figure 8 The LSV curves of the catalysts in Examples 2 and Comparative Examples 1-3 for the oxygen evolution reaction catalyzed by 1 mol / L KOH solution are shown.

[0038] Figure 9 Electrochemical activity area curves of the catalysts prepared in Example 2 and Comparative Examples 1-2;

[0039] Figure 10 The graphs show the catalytic activity and stability of the catalysts in Example 2 and Comparative Example 3.

[0040] Figure 11 The graphs show the performance of the catalysts in Example 2 and Comparative Example 3 in simulated seawater. Detailed Implementation

[0041] To better explain the present invention, the following specific embodiments are provided for explanation and description.

[0042] Example 1

[0043] A bimetallic single-atom catalyst is based on nitrogen-doped three-dimensional porous carbon aerogel, on which single atoms of Fe and Ni are loaded.

[0044] Example 2

[0045] The bimetallic single-atom catalyst preparation method in Example 1 uses chitosan as a biomass material, silica with an average particle size of 15 nm as a pore-forming agent, carbon black as a conductive agent, and a 1% (v / v) acetic acid solution as a dispersant. The specific steps are as follows:

[0046] S1, 6 mg of carbon black was added to 3 mL of acetic acid solution and sonicated for 20 min to prepare a suspension in which carbon black was uniformly dispersed; then 60 mg of chitosan and 40 mg of silica were mixed and added to a container, the above suspension was slowly added to the container and stirred continuously for 40 min to obtain a uniform and stable suspension.

[0047] S2, while stirring, 80 μL of iron-o-phenanthroline complex and 80 μL of nickel-o-phenanthroline complex were added sequentially to the homogeneous and stable suspension obtained in S1 to obtain the hydrogel precursor.

[0048] S3, freeze-dry the hydrogel precursor, then heat it to 500℃ at a rate of 5℃ / min in an Ar atmosphere, hold it at that temperature for 2h, and then continue to cool it to room temperature at a rate of 5℃ / min.

[0049] S4. The heat-treated product is ground and then soaked in 0.5 mol / L NaOH solution for 2 hours to remove the silica nanoparticles, resulting in a nitrogen-doped porous carbon aerogel supported by a bimetallic single atom, which is the desired catalyst, named NCA / FeNi.

[0050] Figure 1 and Figure 2 The images show the carbon aerogel framework morphology of the bimetallic single-atom catalyst prepared by SEM and TEM characterization, respectively. It can be seen that the matrix material of the catalyst is mainly a three-dimensional porous structure composed of mesopores with a pore size of about 20-30 nm.

[0051] Images of bimetallic single-atom catalysts obtained by high-resolution scanning transmission microscopy with double spherical aberration correction are shown below. Figure 3 As shown, the uniformly dispersed white dots in the atomic phase diagram indicate that a particle with a size of approximately [missing information] is loaded within the porous framework of the aerogel. single metal atoms; Figure 4 The distribution diagram of various elements shows that C, N, O, Fe, and Ni are uniformly distributed in the carbon aerogel.

[0052] Based on the above analysis, the three-dimensional hierarchical porous carbon aerogel generated by pore formation through hydrogel precursors can effectively regulate the size of metal particles, thereby optimizing the metal electron regulation ratio, achieving efficient metal utilization and full exposure of active sites. At the same time, the three-dimensional porous aerogel can effectively stabilize the active sites of metal atoms, exhibiting good self-sustaining capacity during electrocatalysis, protecting the active sites from interference from the external environment, and thus achieving ultra-long-lasting and stable electrocatalytic function.

[0053] Comparative Example 1

[0054] The preparation method is the same as in Example 2, except that only the iron-1,000 phenanthrene complex is added in step S2, instead of the nickel-1,000 phenanthrene complex. The resulting catalyst is named NCA / Fe.

[0055] Comparative Example 2

[0056] The preparation method is the same as in Example 2, except that only the nickel-o-phenanthroline complex is added in step S2, instead of the iron-o-phenanthroline complex. The resulting catalyst is named NCA / Ni.

[0057] The structural composition of the catalysts prepared in Example 2 and Comparative Examples 1-2 was characterized by XRD, Raman spectroscopy and ICP.

[0058] from Figure 5 As can be seen, XRD did not detect any metal diffraction peaks, indicating that no metal nanoparticles were detected in the carbon aerogel framework. Raman spectroscopy further confirmed this. Figure 6 The bimetallic single-atom catalyst NCA-FeNi obtained in Example 2 has I D / I G The ratio was 0.86, slightly higher than that of comparative examples 1-2, indicating that the introduction of the second metal may have promoted the formation of defects on the carbon surface, which is beneficial to the formation of metal active sites.

[0059] The metal element content in the prepared carbon aerogel was quantitatively analyzed using inductively coupled plasma-emitting emission spectroscopy (ICP-OES). The results showed that the Fe content in NCA / FeNi was 1.06 wt% and the Ni content was 1.85 wt%. This result is consistent with the result obtained by XPS.

[0060] Further analysis of the catalyst's elemental composition and valence electronic states was conducted using X-ray photoelectron spectroscopy (XPS). Figure 7 (a) Fitting the high-resolution N1s spectra of NCA / FeNi and NCA / Fe shows that the introduction of metallic Ni increases the peak area of ​​metallic nitrogen. Figure 7 (b) It can be seen that the introduction of Ni metal species shifts the Fe(II) peak to a lower field by 0.3 eV, while Figure 7 (c) shows that the Ni(III) peak shifted to a higher field by 0.1 eV, indicating that there may be a phenomenon of Ni atom electron transfer to Fe atom in NCA / FeNi.

[0061] To further verify the structure of the catalyst obtained in this invention, X-ray near-edge structure analysis (XANES) and extended X-ray absorption fine structure analysis (EXAFS) were used to analyze and determine the presence forms of Fe and Ni elements in the NCA / FeNi catalyst prepared in Example 2 of this invention. It was found that the K-edge X-ray near-edge structure analysis pattern of Fe in NCA / FeNi is similar to that of FePc, while showing significant differences from Fe foil, indicating that the oxidation state of Fe is closer to that of FePc, and there are no aggregates of Fe metal atoms. Similarly, Ni is also dispersed as single atoms.

[0062] Application Example 1

[0063] To verify the performance of the single-atom bimetallic catalyst prepared in this invention, the performance of Example 2, Comparative Examples 1-2, and a commercially available RuO2 catalyst (hereinafter referred to as "Comparative Example 3") was studied and analyzed. Details are as follows.

[0064] The catalytic treatment medium was a 1 mol / L KOH solution. The electrocatalytic activities of NCA / FeNi, NCA / Fe, NCA / Ni, and RuO2 for oxygen evolution were tested using linear sweep voltammetry (LSV). Figure 8 As shown. When the catalytic current density reaches 10 mA cm⁻¹ -2 At that time, the overpotential of NCA / FeNi was only 0.288V, much smaller than that of NCA / Fe (0.321V), NCA / Ni (0.345V), and the 0.361V of the commercial RuO2 catalyst. Furthermore, the Tafel slope of the NCA / FeNi-catalyzed oxygen evolution reaction was 61.2 mV dec. -1 This is far lower than the 93.4 mV dec of RuO2. -1 The relative magnitude of electrochemical impedance values ​​reflects the rate of charge transfer during catalysis. From... Figure 8 As shown in (c), the radius of the semicircular portion in the EIS spectrum of NCA / FeNi is significantly smaller than that of the semicircular portions of other materials, proving that NCA / FeNi has a relatively low internal resistance, which helps to improve catalyst activity. Therefore, it can be determined that the oxygen evolution performance of the NCA / FeNi catalyst prepared in Example 2 of this invention is superior to most reported carbon-based transition metal single-atom catalysts.

[0065] Figure 9 Electrochemical active area curves at different scan rates within the non-Radidatic window of Examples 2, Comparative Examples 1-2, and Comparative Example 3 are shown. These curves were obtained at 10, 20, 30, 40, and 50 mV / s. -1 The CV curve was scanned in the non-Radida region at a scan rate of [value missing], and the Cdl value, an important parameter of ECSA, was obtained by fitting. It can be seen that the Cdl value of NCA / FeNi is 7.8 mF cm⁻¹.-2 Greater than NCA / Fe(5.2mF cm⁻¹) -2 ), NCA / Ni (5.4mF cm) -2 This indicates that NCA / FeNi has a higher ECSA.

[0066] Figure 10 This demonstrates that the catalyst prepared in Example 2 of the present invention possesses good catalytic activity and stability. Using a 1 mol / L KOH solution as the electrolyte, and with working electrodes prepared from the NCA / FeNi sample of Example 2 and the RuO2 sample from Comparative Example 3, respectively, and a Pt / C electrode as the counter electrode, the LSV polarization curves of the two-electrode system for water electrolysis were constructed, as shown below. Figure 10 (a) shows that under the same conditions, only 1.556V is needed to achieve 10mA cm⁻¹ when using NCA / FeNi as the working electrode. -2 Its current density is higher than that of the benchmark catalyst RuO2. Figure 10 (b) As shown, NCA / FeNi at 10 mA cm -2 Under the same conditions, the catalytic performance remained basically constant after more than 100 hours of constant current electrolysis. However, in contrast, commercial RuO2 showed a significant performance degradation within just 28 hours. Figure 10 (c) shows that the LSV polarization curve of the electrode was tested after electrolysis, and NCA / FeNi was electrolyzed for 105 h at a current density of 10 mA cm⁻¹. -2 The overpotential of the sample decreased by only 20mV, while the overpotential of commercial RuO2 decreased by 80mV in just 28 hours.

[0067] Application Example 2

[0068] Earth's water resources are primarily seawater, making it a suitable electrolyte for hydrogen production via electrolysis. This application example uses a mixed solution of 1.0 mol / L KOH and 0.5 mol / L NaCl to simulate alkaline seawater, and electrolysis is performed using the catalysts from Example 2 and Comparative Example 3. The results are as follows: Figure 11 As shown.

[0069] Figure 11 (a) This indicates that only 1.549V is required to achieve 10mA cm in a two-electrode system. -2 The current density is superior to that of RuO2. Furthermore, due to the presence of more free ions in the solution, the conductivity of the electrolyte is further improved, such as... Figure 11 As shown in (b), the Tafel slope of NCA / FeNi in alkaline seawater further decreases to 59.7 mV dec. -1This indicates that the electrochemical reaction kinetics of the electrode materials are faster in alkaline seawater, which is more conducive to energy conversion. NCA / FeNi can achieve an electrolysis efficiency of 10 mA cm⁻¹ in alkaline seawater. -2 The NCA / FeNi prepared in this method maintains stability for over 130 hours at a given current density, while commercial RuO2 showed significant performance degradation after only 22 hours. This indicates that the NCA / FeNi prepared in this method exhibits excellent corrosion resistance in alkaline seawater environments, particularly against Cl. - It has excellent corrosion resistance.

[0070] Example 3

[0071] A method for preparing a Co and Ru supported bimetallic single-atom catalyst, the specific steps of which are as follows:

[0072] S1, 200mg of lignocellulose and 1500mg of silica are mixed and added to a container, then 10mL of 2% acetic acid solution is added, and the mixture is sonicated for 15min to obtain a uniform and stable suspension.

[0073] S2, while stirring, 260 μL of cobalt-o-phenanthroline complex and 260 μL of ruthenium-o-phenanthroline complex were added sequentially to the homogeneous and stable suspension obtained in S1 to obtain the hydrogel precursor.

[0074] S3, freeze-dry the hydrogel precursor, then heat it to 460°C at a rate of 5°C / min in an Ar atmosphere, hold it at that temperature for 3 hours, and then continue to cool it to room temperature at a rate of 5°C / min.

[0075] S4. The heat-treated product is ground and then soaked in 0.8 mol / L NaOH solution for 1.2 h to remove the silica nanoparticles, thus obtaining a nitrogen-doped porous carbon aerogel catalyst supported by a bimetallic single atom, wherein the bimetals are Co and Ru.

[0076] Application Example 3

[0077] The performance of the bimetallic single-atom catalyst supported on Co and Ru obtained in Example 3 was determined according to the method of Application Example 2.

[0078] In alkaline seawater, the catalyst obtained in Example 3 exhibits a Tafel slope of 67.1 mV dec. -1 Compared to Example 2, it is higher, but significantly better than RuO2, and also has the effect of promoting a faster electrochemical reaction; and it can achieve 10 mA cm⁻¹ when electrolyzing alkaline seawater. -2 The catalyst maintained stability for more than 152 hours at a current density, which is superior to NCA / FeNi in Example 2, indicating that the catalyst obtained in Example 3 also has excellent corrosion resistance in alkaline seawater environment.

[0079] Examples 4-10

[0080] The bimetallic single-atom catalyst, wherein the supported bimetal, the biomass material used, and the pore-forming agent are as follows, can be prepared according to the method of Example 2.

[0081] Example 4 Fe Co Chitosan <![CDATA[12nm SiO2]]> Example 5 Fe Zn Lignocellulose <![CDATA[20nm of SiO2]]> Example 6 Co Ni Chitosan <![CDATA[12nm SiO2]]> Example 7 Fe Ru Chitosan <![CDATA[25nm of SiO2]]> Example 8 Zn Ru Chitosan <![CDATA[20nm of SiO2]]> Example 9 Cu Zn Lignocellulose <![CDATA[25nm of SiO2]]> Example 10 Ni Cu Chitosan <![CDATA[25nm of SiO2]]>

[0082] Comparing the performance of the bimetallic single-atom catalysts obtained in Examples 2-10 in the catalytic oxygen evolution reaction, it can be found that the bimetallic single-atom catalyst supported on FeNi prepared in Example 2 and the bimetallic single-atom catalyst supported on CoRu obtained in Example 3 have better performance and are better choices with development potential.

Claims

1. A method for preparing a bimetallic single-atom catalyst, characterized in that, The preparation method includes the following steps: S1, prepare a suspension of biomass material and pore-forming agent; the biomass material includes chitosan, the pore-forming agent includes nano-sized silica, the mass ratio of chitosan to nano-sized silica is 3:(1-3), the dispersant for preparing the suspension is a 1-5% volume fraction acetic acid solution, the volume ratio of chitosan to acetic acid solution is (20-25) mg:1 mL; carbon black is pre-added to the acetic acid solution and dispersed evenly, the volume ratio of carbon black to acetic acid solution is 2 mg:(1-2) mL; S2, two metal phenanthrene complexes are added sequentially to the suspension to obtain a precursor; the two metals are Fe and Ni; the volume ratio of the two metal phenanthrene complexes is 1:1; S3, After drying the precursor, perform a heat treatment operation; the heat treatment operation is carried out in an inert environment, and the heat treatment operation includes a heating and cooling process at a rate of 5℃ / min, and a holding process between the heating and cooling processes, wherein the holding process is to hold at 460-500℃ for 1-3 hours. S4. Remove the pore-forming agent to obtain a nitrogen-doped porous carbon aerogel supported by a bimetallic single atom, which is the catalyst.

2. The preparation method according to claim 1, characterized in that, In step S2, the ratio of chitosan to the o-phenanthroline complex is 1 mg:(2.5-3) μL.

3. The preparation method according to claim 1, characterized in that, In step S4, the pore-forming agent is removed by treatment with NaOH solution.

4. A bimetallic single-atom catalyst, characterized in that, The catalyst is prepared by the method described in claim 1. The catalyst uses nitrogen-doped three-dimensional porous carbon aerogel as the matrix material and supports bimetallic single atoms, wherein the bimetal is Fe and Ni.

5. The application of the bimetallic single-atom catalyst according to claim 4, characterized in that, The catalyst is used to catalyze the oxygen evolution reaction.

6. The application according to claim 5, characterized in that, The catalyst is used to catalyze the oxygen evolution reaction in alkaline seawater.

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