Iron monatomic catalyst with hydrogen passivated carbon edge as well as preparation method and application of iron monatomic catalyst

Abstract

The invention relates to the technical field of electro-catalytic materials, in particular to an iron monatomic catalyst with a hydrogen passivated carbon edge, a preparation method and application, iron in the catalyst is anchored in a nitrogen-doped carbon carrier in an atomic-scale dispersion form, Fe-N4 active sites are formed, and rich active centers are provided; the nitrogen-doped carbon carrier has a rich edge structure, and carbon atoms on the edge structure are passivated by hydrogen atoms. The abundant edge structure provides an open coordination environment and relatively high electron density for Fe-N4 active sites, and is beneficial to adsorption and activation of oxygen molecules. The hydrogen passivation treatment only aims at edge carbon atoms, does not change the geometrical configuration of Fe-N4 active sites, does not generate negative effects on the catalytic activity of the Fe-N4 active sites, can enable the catalyst to still show excellent oxygen reduction reaction catalytic activity on the premise of keeping high stability, and realizes perfect balance of activity and stability.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, specifically to a hydrogen passivation carbon edge iron single-atom catalyst, its preparation method, and its application. Background Technology

[0002] Under the dual pressures of soaring global energy demand and dwindling fossil fuel reserves, the energy crisis has become a key bottleneck restricting the sustainable development of human society. Over-reliance on traditional fossil fuels has not only led to accelerated resource depletion but has also triggered a series of severe environmental problems. Against this backdrop, developing green, clean, and sustainable new energy conversion devices has become an important way to address the energy crisis and environmental issues.

[0003] Proton exchange membrane fuel cells (PEMFCs) and zinc-air batteries, as typical representatives of novel energy conversion devices, have shown broad application prospects in transportation, distributed power generation, and portable electronic devices due to their significant advantages such as high energy conversion efficiency and zero or low emissions. PEMFCs use hydrogen as fuel, directly converting chemical energy into electrical energy through an electrochemical reaction, producing only water in the process, achieving true zero pollution emissions. Zinc-air batteries, on the other hand, use zinc as the negative electrode and oxygen from the air as the positive electrode active material, featuring high energy density, low cost, safety, and environmental friendliness, making them particularly suitable for scenarios with high energy density requirements.

[0004] However, both proton exchange membrane fuel cells and zinc-air batteries face a common challenge in performance improvement—the slow kinetics of the cathode oxygen reduction reaction (ORR). As a crucial step in the battery discharge process, the ORR's reaction rate directly determines the overall battery performance, including power density, energy efficiency, and lifespan. Due to the stable double-bond structure of oxygen molecules, its reduction process requires multiple electron transfers and proton coupling reactions, resulting in extremely complex and slow reaction kinetics. Therefore, developing efficient and stable ORR catalysts has become a core task for improving battery performance.

[0005] Platinum-based noble metal catalysts have long been widely used in oxygen reduction reaction (ORR) catalysis due to their excellent catalytic activity and stability. Platinum-based catalysts can significantly reduce the activation energy of ORR, accelerate the reaction process, and thus improve the overall performance of the battery. However, platinum is a rare metal with limited global reserves, and its mining and purification processes are complex, resulting in its high price. Therefore, the high cost and scarcity of platinum-based catalysts have become major obstacles to their large-scale commercial application.

[0006] Iron single-atom catalysts, due to their unique structure and performance advantages, can disperse iron atoms in single-atom form on the surface of a support, maximizing the utilization of metal atoms and significantly increasing the number and utilization rate of catalytic active sites. This makes the catalytic activity of iron single-atom catalysts comparable to platinum-based catalysts, and they are considered promising alternative materials due to their low cost and abundant resources. Although iron single-atom catalysts have shown great potential in the field of oxygen reduction reaction catalysis, stability issues have become the main factor restricting their practical application. The degradation of iron single-atom catalysts mainly stems from three mechanisms: demetallization, carbon corrosion, and the Fenton reaction. Among these, carbon corrosion is the key factor affecting the lifetime of iron single-atom catalysts. Theoretical studies indicate that M-N4 sites (where M represents a metal atom, such as iron) located at the edge of the carbon plane usually have higher intrinsic activity, but edge carbon atoms are more likely to adsorb oxygen-containing species, thus initiating carbon corrosion and leading to decreased stability. Therefore, how to effectively inhibit corrosion while exposing abundant active edge sites is the core challenge in designing high-performance, high-stability iron single-atom catalysts.

[0007] Currently, strategies for improving the stability of iron single-atom catalysts mainly focus on optimizing the coordination environment of the metal center or constructing a protective layer. Optimizing the coordination environment aims to improve corrosion resistance by adjusting the types and numbers of coordinating atoms around the iron atom, thereby altering the electronic structure and geometry of the active sites. Constructing a protective layer involves coating the catalyst surface with a stabilizing material (such as a carbon layer or oxide layer) to isolate the catalyst from direct contact with the electrolyte and reduce corrosion reactions. However, these strategies often come at the cost of sacrificing some activity, making it difficult to achieve simultaneous improvements in activity and stability. Therefore, there is an urgent need to develop a universal strategy that can significantly enhance the durability of iron single-atom catalysts without sacrificing activity. This strategy needs to balance the exposure of active sites with the improvement of corrosion resistance, achieving a balance between activity and stability, and laying a solid foundation for the widespread application of iron single-atom catalysts in novel energy conversion devices. Summary of the Invention

[0008] To address the problem of low stability of edge-type iron single-atom catalysts in existing technologies, this invention provides a hydrogen passivation carbon edge iron single-atom catalyst, its preparation method, and its application.

[0009] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a hydrogen passivated carbon edge iron single-atom catalyst, comprising a nitrogen-doped carbon support and iron; wherein, iron is anchored in the nitrogen-doped carbon support in an atomically dispersed form to form Fe-N4 active sites; the nitrogen-doped carbon support has abundant edge structures, and the carbon atoms on the edge structures are passivated by hydrogen atoms.

[0010] This invention also provides a method for preparing an iron single-atom catalyst with hydrogen passivation of carbon edges as described above, comprising: Ferric acetylacetone, zinc chloride, and formamide were mixed and subjected to a hydrothermal reaction to obtain a precursor powder. The precursor powder was pyrolyzed to obtain an iron-nitrogen-carbon single-atom catalyst. The iron-nitrogen-carbon single-atom catalyst was dispersed in a solvent, and then hydrothermal etching was performed after adding hydrogen peroxide solution to obtain the etched catalyst. The etched catalyst was heat-treated in an inert atmosphere containing hydrogen to obtain a hydrogen passivated carbon edge iron single-atom catalyst.

[0011] Optionally, after mixing ferric acetylacetone, zinc chloride, and formamide, the molar concentration of zinc chloride is (0.05-0.15) mol / L, and the molar concentration of ferric acetylacetone is (0.004-0.006) mol / L.

[0012] Optionally, the hydrothermal reaction temperature is 160-190℃, and the hydrothermal reaction time is 10-18h.

[0013] Optionally, the pyrolysis treatment is performed under an inert atmosphere, at a temperature of 800-1000℃, at a heating rate of 3-6℃ / min, and for a duration of 1.6-2.5h.

[0014] Optionally, the solvent is an aqueous ethanol solution, wherein the volume ratio of ethanol to water in the aqueous ethanol solution is 1:(0.5-2); the mass concentration of the hydrogen peroxide solution is 25%-40%, and after adding the hydrogen peroxide solution, the volume ratio of the hydrogen peroxide solution to the solvent is 1:(40-60).

[0015] Optionally, the temperature of the hydrothermal etching process is 100-120℃, and the time of the hydrothermal etching process is 3-12h.

[0016] Optionally, the hydrogen-containing inert atmosphere is a mixture of hydrogen and argon; wherein, in the mixture of hydrogen and argon, the volume fraction of hydrogen is 8%-12%.

[0017] Optionally, the heat treatment temperature in the inert atmosphere containing hydrogen is 800-1000℃, the heat treatment heating rate is 3-6℃ / min, and the heat treatment time is 1.6-2.5h.

[0018] The above-mentioned hydrogen passivation of carbon edge iron single-atom catalysts is used in proton exchange membrane fuel cells or zinc-air batteries.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a hydrogen-passivated iron single-atom catalyst with carbon edges. In this catalyst, iron is anchored in a nitrogen-doped carbon support in an atomically dispersed form, forming Fe-N4 active sites. This ensures extremely high atomic utilization of iron atoms, allowing each iron atom to fully participate in the catalytic reaction and providing abundant active centers. The nitrogen-doped carbon support has abundant edge structures, and the carbon atoms on these edge structures are passivated by hydrogen atoms. The abundant edge structures provide an open coordination environment and high electron density for the Fe-N4 active sites, which is beneficial for the adsorption and activation of oxygen molecules and promotes the oxygen reduction reaction. The hydrogen passivation treatment only targets the edge carbon atoms and does not change the geometry of the Fe-N4 active sites themselves. Therefore, it does not negatively affect their catalytic activity, enabling the catalyst to maintain high stability while still exhibiting excellent oxygen reduction reaction catalytic activity, achieving a perfect balance between activity and stability.

[0020] This invention also provides a method for preparing an iron single-atom catalyst with hydrogen passivated carbon edges as described above. This method involves mixing iron acetylacetone, zinc chloride, and formamide, followed by hydrothermal reaction and pyrolysis to obtain an iron-nitrogen-carbon single-atom catalyst. Then, the iron-nitrogen-carbon single-atom catalyst is subjected to hydrothermal etching and heat treatment in an inert atmosphere containing hydrogen to obtain an iron single-atom catalyst with hydrogen passivated carbon edges. This method first involves mixing iron acetylacetone, zinc chloride, and formamide, followed by hydrothermal reaction and pyrolysis, causing complex chemical reactions and structural reorganization among the raw materials. This constructs a structure in which iron is anchored in an atomically dispersed form on a nitrogen-doped carbon support, possessing abundant active sites. Then, controlled etching creates abundant carbon edges to expose more active sites. Finally, heat treatment in a hydrogen atmosphere passivates these edges, effectively removing adsorbed oxygen-containing species and inhibiting subsequent carbon corrosion. This method is simple, easy to operate, and highly controllable. It is not only applicable to the Fe-NC system but also effective for other single-atom catalyst systems such as Co-NC, providing a general approach for designing various high-durability non-precious metal catalysts. Testing revealed that the hydrogen-passivated carbon-edge iron single-atom catalyst prepared using this method exhibited an ORR half-wave potential as high as 0.90 V in alkaline media, superior to commercial Pt / C, and retained 93% of its initial current after a 12-hour potentiostatic test. The assembled zinc-air battery achieved a peak power density of 312 mW / cm². -2 The peak power density of the proton exchange membrane fuel cell reached 383 mW / cm³. -2 It demonstrates excellent application potential.

[0021] The above-mentioned hydrogen-passivated carbon-edge iron single-atom catalyst is applied in proton exchange membrane fuel cells or zinc-air batteries. Due to its excellent performance, the hydrogen-passivated carbon-edge iron single-atom catalyst of this invention can serve as a highly efficient cathode oxygen reduction reaction catalyst in proton exchange membrane fuel cells, improving the power density and energy efficiency of the battery and meeting the demand for high-performance, long-range fuel cells in the transportation sector. In zinc-air batteries, it can enhance the charge-discharge performance and cycle stability of the battery, extending its lifespan, and is suitable for distributed power generation and portable electronic devices. Furthermore, this catalyst can be extended to other energy conversion and storage devices involving oxygen reduction reactions, such as metal-air batteries and biofuel cells, providing strong catalytic support for the development of new energy technologies in various fields. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of a method for preparing a hydrogen passivation carbon edge iron single-atom catalyst according to the present invention.

[0023] Figure 2 The X-ray diffraction pattern of H@Fe-NC-3 obtained in Example 1 of this invention is shown.

[0024] Figure 3 The images shown are transmission electron microscope images of H@Fe-NC-3 prepared in Example 1, with different magnifications in Figures a and b.

[0025] Figure 4 The image shows the elemental mapping of H@Fe-NC-3 obtained in Example 1, where a is the TEM image, b is the C elemental mapping, c is the N elemental mapping, and d is the Fe elemental mapping.

[0026] Figure 5 This is a spherical aberration electron microscope image of H@Fe-NC-3 obtained in Example 1.

[0027] Figure 6 Linear sweep voltammetry curves of the H@Fe-NC-3 catalyst prepared in Example 1, the Fe-NC catalyst prepared in Comparative Example 1, and the H@Fe-NC-12 catalyst prepared in Example 2.

[0028] Figure 7 Tafel slope diagrams for the H@Fe-NC-3 catalyst prepared in Example 1, the Fe-NC catalyst prepared in Comparative Example 1, and the H@Fe-NC-12 catalyst prepared in Example 2.

[0029] Figure 8The current-time curves of the H@Fe-NC-3 catalyst prepared in Example 1 and the O@Fe-NC-3 catalyst prepared in Comparative Example 2 in O2-saturated 0.1M KOH solution at 0.6V vs. RHE potential are shown.

[0030] Figure 9 The linear sweep voltammetry curves of the H@Fe-NC-3 catalyst prepared in Example 1 and the O@Fe-NC-3 catalyst prepared in Comparative Example 2 are obtained before and after 10,000 cycles in an O2-saturated 0.1M KOH solution at a potential range of 0.6V-1.0V vs. RHE. Among them, a is the linear sweep voltammetry curve of the H@Fe-NC-3 catalyst prepared in Example 1, and b is the linear sweep voltammetry curve of the O@Fe-NC-3 catalyst prepared in Comparative Example 2.

[0031] Figure 10 The graph shows the power density of a zinc-air battery assembled with the H@Fe-NC-3 catalyst prepared in Example 1.

[0032] Figure 11 Power density curve of proton exchange membrane fuel cell assembled with H@Fe-NC-3 catalyst prepared in Example 1. Detailed Implementation

[0033] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0034] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0035] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0036] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0037] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0038] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0039] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0040] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0041] This invention provides a hydrogen passivated carbon edge iron single-atom catalyst, comprising a nitrogen-doped carbon support and iron; wherein, iron is anchored in the nitrogen-doped carbon support in an atomically dispersed form to form Fe-N4 active sites; the nitrogen-doped carbon support has abundant edge structures, and the carbon atoms on the edge structures are passivated by hydrogen atoms.

[0042] See Figure 1 The present invention also provides a method for preparing the hydrogen passivation carbon edge iron single-atom catalyst as described in claim 1, comprising: S1: Ferric acetylacetone, zinc chloride, and formamide are mixed and subjected to a hydrothermal reaction to obtain a precursor powder; wherein, after mixing ferric acetylacetone, zinc chloride, and formamide, the molar concentration of zinc chloride is (0.05-0.15) mol / L, preferably 0.1 mol / L; the molar concentration of ferric acetylacetone is (0.004-0.006) mol / L, preferably 0.005 mol / L; the temperature of the hydrothermal reaction is 160-190℃, and the time of the hydrothermal reaction is 10-18h, preferably 180℃ for 12h.

[0043] S2: The precursor powder is subjected to pyrolysis to obtain an iron-nitrogen-carbon single-atom catalyst; wherein the pyrolysis conditions are inert atmosphere, the pyrolysis temperature is 800-1000℃, the pyrolysis heating rate is 3-6℃ / min, and the pyrolysis time is 1.6-2.5h, preferably pyrolysis at 5℃ / min to 900℃ for 2h.

[0044] S3: Disperse the iron-nitrogen-carbon single-atom catalyst in a solvent, add hydrogen peroxide solution and perform hydrothermal etching to obtain the etched catalyst; wherein, the solvent is an aqueous ethanol solution, and the volume ratio of ethanol to water in the aqueous ethanol solution is 1:(0.5-2); the mass concentration of the hydrogen peroxide solution is 25%-40%, and after adding the hydrogen peroxide solution, the volume ratio of hydrogen peroxide solution to solvent is 1:(40-60), the volume ratio of ethanol to water is preferably 1:1, the mass concentration of hydrogen peroxide solution is preferably 30%, and the volume ratio of hydrogen peroxide solution to solvent is 1:50.

[0045] S4: The etched catalyst is heat-treated in an inert atmosphere containing hydrogen to obtain a hydrogen-passivated iron single-atom catalyst with carbon edges. The inert atmosphere containing hydrogen is a mixture of hydrogen and argon, with a hydrogen volume fraction of 8%-12%, preferably 10%. The heat treatment temperature in the hydrogen-containing inert atmosphere is 800-1000℃, the heating rate is 3-6℃ / min, and the heat treatment time is 1.6-2.5h, preferably a heating rate of 5℃ / min to 900℃ for 2h.

[0046] The above-mentioned hydrogen-passivated carbon-edge iron single-atom catalyst is applied in proton exchange membrane fuel cells or zinc-air batteries. Due to its excellent performance, the hydrogen-passivated carbon-edge iron single-atom catalyst of this invention can serve as a highly efficient cathode oxygen reduction reaction catalyst in proton exchange membrane fuel cells, improving the power density and energy efficiency of the battery and meeting the demand for high-performance, long-range fuel cells in the transportation sector. In zinc-air batteries, it can enhance the charge-discharge performance and cycle stability of the battery, extending its lifespan, and is suitable for distributed power generation and portable electronic devices. Furthermore, this catalyst can be extended to other energy conversion and storage devices involving oxygen reduction reactions, such as metal-air batteries and biofuel cells, providing strong catalytic support for the development of new energy technologies in various fields.

[0047] Example 1 0.162 g of ferric acetylacetone and 1.224 g of anhydrous zinc chloride were added to 90 mL of formamide and ultrasonically dispersed for 30 min until completely dissolved. The solution was then transferred to a 150 mL high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 180 °C for 12 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting black solid product was washed several times by centrifugation with deionized water and ethanol, and then dried in a vacuum oven at 60 °C for 12 h to obtain the precursor powder.

[0048] The precursor powder was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere (flow rate 50 sccm), the temperature was increased to 900℃ at a rate of 5℃ / min, and then held at this temperature for pyrolysis for 2 hours. After natural cooling to room temperature, the resulting black powder was ground uniformly to obtain an iron-nitrogen-carbon single-atom catalyst, denoted as Fe-NC.

[0049] 100 mg of iron-nitrogen-carbon single-atom catalyst was weighed and dispersed in a mixed solvent of 25 mL deionized water and 25 mL ethanol. The mixture was ultrasonically treated for 1 h to form a uniform dispersion. 1 mL of 30 wt% hydrogen peroxide solution was added to the dispersion, and the mixture was stirred continuously for 30 min. The mixture was then transferred to a 100 mL high-pressure reactor and subjected to hydrothermal etching at 110 °C for 3 h. After the treatment, the product was washed and dried to obtain the etched catalyst, denoted as Fe-NC-3.

[0050] Fe-NC-3 powder was placed in a ceramic boat and then placed in a tube furnace. Under a mixed atmosphere of 10% H2 and 90% Ar (volume fraction) (total flow rate 50 sccm), the temperature was increased to 900℃ at a rate of 5℃ / min and held for 2 hours for heat treatment. After heat treatment, the powder was cooled to room temperature under a mixed atmosphere to obtain a hydrogen-passivated carbon-edge iron single-atom catalyst, denoted as H@Fe-NC-3.

[0051] See Figure 2 X-ray diffraction pattern analysis of H@Fe-NC-3 prepared in this example showed that H@Fe-NC-3 only had two broadened carbon diffraction peaks, and no sharp diffraction peaks belonging to metallic iron or its oxides were observed, indicating that iron exists in an atomically dispersed form.

[0052] See Figure 3 Transmission electron microscopy was performed on the H@Fe-NC-3 prepared in this embodiment. It was found that the H@Fe-NC-3 catalyst, after etching and hydrogen passivation treatment, maintained its overall morphology while a large number of nanoscale pores appeared on the carbon layer (marked with red circles), indicating that the etching process successfully introduced rich edge and mesoporous structures.

[0053] See Figure 4 Elemental mapping analysis of H@Fe-NC-3 prepared in this embodiment revealed that Fe, C, and N elements were highly uniformly distributed throughout the carbon support, and no Fe aggregation regions were observed, confirming the single-atom dispersion state of Fe.

[0054] See Figure 5 Aberration electron microscopy was performed on the H@Fe-NC-3 prepared in this embodiment, and atomically dispersed Fe single atoms (highlights in the figure, marked with red arrows) were found in the H@Fe-NC-3 catalyst. These single-atom highlights are mostly located at the edges of the carbon layer or near the pores.

[0055] Example 2 0.162 g of ferric acetylacetone and 1.224 g of anhydrous zinc chloride were added to 90 mL of formamide and ultrasonically dispersed for 30 min until completely dissolved. The solution was then transferred to a 150 mL high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 180 °C for 12 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting black solid product was washed several times by centrifugation with deionized water and ethanol, and then dried in a vacuum oven at 60 °C for 12 h to obtain the precursor powder.

[0056] The precursor powder was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere (flow rate 50 sccm), the temperature was increased to 900℃ at a rate of 5℃ / min, and then held at this temperature for pyrolysis for 2 hours. After natural cooling to room temperature, the resulting black powder was ground uniformly to obtain an iron-nitrogen-carbon single-atom catalyst, denoted as Fe-NC.

[0057] 100 mg of iron-nitrogen-carbon single-atom catalyst was weighed and dispersed in a mixed solvent of 25 mL deionized water and 25 mL ethanol. The mixture was ultrasonically treated for 1 h to form a uniform dispersion. 1 mL of 30 wt% hydrogen peroxide solution was added to the dispersion, and the mixture was stirred continuously for 30 min. The mixture was then transferred to a 100 mL high-pressure reactor and subjected to hydrothermal etching at 110 °C for 12 h. After the treatment, the product was washed and dried to obtain the etched catalyst, denoted as Fe-NC-12.

[0058] Fe-NC-12 powder was placed in a ceramic boat and then placed in a tube furnace. Under a mixed atmosphere of 10% H2 and 90% Ar (volume fraction) (total flow rate 50 sccm), the temperature was increased to 900℃ at a rate of 5℃ / min and held for 2 hours for heat treatment. After heat treatment, the powder was cooled to room temperature under a mixed atmosphere to obtain a hydrogen-passivated iron single-atom catalyst at the carbon edge, denoted as H@Fe-NC-12.

[0059] Comparative Example 1 0.162 g of ferric acetylacetone and 1.224 g of anhydrous zinc chloride were added to 90 mL of formamide and ultrasonically dispersed for 30 min until completely dissolved. The solution was then transferred to a 150 mL high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 180 °C for 12 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting black solid product was washed several times by centrifugation with deionized water and ethanol, and then dried in a vacuum oven at 60 °C for 12 h to obtain the precursor powder. The precursor powder was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere (flow rate 50 sccm), the temperature was increased to 900℃ at a rate of 5℃ / min, and then held at this temperature for pyrolysis for 2 hours. After natural cooling to room temperature, the resulting black powder was ground uniformly to obtain an iron-nitrogen-carbon single-atom catalyst, denoted as Fe-NC.

[0060] The products prepared in Examples 1 and 2 were compared with those prepared in Comparative Example 1. See [link to relevant documentation]. Figure 6 Linear sweep voltammetry curves showed that the untreated Fe-NC catalyst had a half-wave potential of 0.83 V. After etching and hydrogen passivation, the performance was significantly improved, with H@Fe-NC-3 exhibiting the best activity and a half-wave potential as high as 0.90 V. The activity decreased when the etching time was too long (H@Fe-NC-12).

[0061] See Figure 7 The Tafel slope plot shows that the Tafel slope of H@Fe-NC-3 prepared in Example 1 is 77 mVdec. -1 This demonstrates the relatively fast reaction kinetics of H@Fe-NC-3.

[0062] Comparative Example 2 0.162 g of ferric acetylacetone and 1.224 g of anhydrous zinc chloride were added to 90 mL of formamide and ultrasonically dispersed for 30 min until completely dissolved. The solution was then transferred to a 150 mL high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 180 °C for 12 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting black solid product was washed several times by centrifugation with deionized water and ethanol, and then dried in a vacuum oven at 60 °C for 12 h to obtain the precursor powder.

[0063] The precursor powder was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere (flow rate 50 sccm), the temperature was increased to 900℃ at a rate of 5℃ / min, and then held at this temperature for pyrolysis for 2 hours. After natural cooling to room temperature, the resulting black powder was ground uniformly to obtain an iron-nitrogen-carbon single-atom catalyst, denoted as Fe-NC.

[0064] 100 mg of iron-nitrogen-carbon single-atom catalyst was weighed and dispersed in a mixed solvent of 25 mL deionized water and 25 mL ethanol. The mixture was ultrasonically treated for 1 h to form a uniform dispersion. 1 mL of 30 wt% hydrogen peroxide solution was added to the dispersion, and the mixture was stirred continuously for 30 min. The mixture was then transferred to a 100 mL high-pressure reactor and subjected to hydrothermal etching at 110 °C for 3 h. After the treatment, the product was washed and dried to obtain the etched catalyst, denoted as Fe-NC-3.

[0065] Fe-NC-3 powder was placed in a ceramic boat and then placed in a tube furnace. Under a 100% Ar atmosphere (total flow rate 50 sccm), the temperature was increased to 900℃ at a rate of 5℃ / min and held for 2 hours for heat treatment. After heat treatment, the powder was cooled to room temperature under a protective atmosphere to obtain a hydrogen-passivated iron single-atom catalyst at the carbon edge, denoted as O@Fe-NC-3.

[0066] Comparative Example 2 and Example 1 were compared and tested; see [link / reference]. Figure 8 A comparison of the current-time curves for H@Fe-NC-3 and O@Fe-NC-3 (heat-treated in argon only) shows that, after 12 hours of continuous testing at 0.6 V vs. RHE potential, H@Fe-NC-3 retained 93% of its initial current, while O@Fe-NC-3 only retained 84%. See also... Figure 9 By comparing the linear sweep voltammetric curves of H@Fe-NC-3 and O@Fe-NC-3 before and after 10,000 cycles of cyclic voltammetry testing, it was found that the half-wave potential of H@Fe-NC-3 decreased by 14 mV, while that of O@Fe-NC-3 decreased by 18 mV. This strongly demonstrates the crucial role of hydrogen passivation treatment in removing unstable oxygen-containing groups, inhibiting carbon corrosion, and thus significantly improving catalyst durability.

[0067] The H@Fe-NC-3 catalyst prepared in Example 1 was used as an air cathode to assemble a liquid zinc-air battery for testing. See [link to example]. Figure 10 (The discharge polarization curve and corresponding power density curve of the battery) show that the peak power density of the battery reaches 312 mW cm⁻¹. -2 It demonstrates excellent potential for practical application.

[0068] The H@Fe-NC-3 catalyst prepared in Example 1 was used as the cathode to assemble a proton exchange membrane fuel cell for testing. (See [link to relevant documentation]). Figure 11 (The discharge polarization curve and corresponding power density curve of the battery) show that the peak power density of the battery reaches 383 mW cm⁻¹. -2 It demonstrates excellent potential for practical application.

[0069] In summary, through a series of comparisons between the embodiments and comparative examples of this invention, the following conclusions can be clearly drawn: the method for preparing the hydrogen-passivated carbon-edge iron single-atom catalyst provided by this invention, employing a "controllable etching combined with hydrogen passivation" approach, is an effective strategy. It successfully resolves the inherent contradiction in iron single-atom catalysts where "high-activity edges are accompanied by high corrosion risk." The prepared hydrogen-passivated carbon-edge iron single-atom catalyst exhibits significant improvements in activity, kinetics, and stability, demonstrating excellent performance in practical devices. This lays the material foundation for the development of next-generation high-performance, long-life non-precious metal fuel cells and metal-air batteries.

[0070] Example 3 0.1271 g of ferric acetylacetone and 0.6133 g of anhydrous zinc chloride were added to 90 mL of formamide and ultrasonically dispersed for 30 min until completely dissolved. The solution was then transferred to a 150 mL high-pressure reactor lined with polytetrafluoroethylene and reacted in a 160 °C oven for 18 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting black solid product was washed several times by centrifugation with deionized water and ethanol, and then dried in a 60 °C vacuum oven for 12 h to obtain the precursor powder.

[0071] The precursor powder was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere (flow rate 50 sccm), the temperature was increased to 800℃ at a rate of 4℃ / min, and then pyrolyzed at this temperature for 2.5 h. After natural cooling to room temperature, the resulting black powder was ground uniformly to obtain an iron-nitrogen-carbon single-atom catalyst.

[0072] 100 mg of iron-nitrogen-carbon single-atom catalyst was weighed and dispersed in a mixed solvent of 30 mL deionized water and 20 mL ethanol. The mixture was ultrasonically treated for 1 h to form a uniform dispersion. 1 mL of 25 wt% hydrogen peroxide solution was added to the dispersion, and the mixture was stirred continuously for 30 min. The mixture was then transferred to a 100 mL high-pressure reactor and subjected to hydrothermal etching at 110 °C for 3 h. After the treatment, the product was washed and dried to obtain the etched catalyst.

[0073] The etched catalyst powder was placed in a ceramic boat and then placed in a tube furnace. Under a mixed atmosphere of 8% H₂ and 92% Ar (volume fraction) (total flow rate 50 sccm), the temperature was increased to 800°C at a rate of 4°C / min and held for 2.5 hours for heat treatment. After heat treatment, the powder was cooled to room temperature under a mixed atmosphere to obtain the hydrogen-passivated carbon-edge iron single-atom catalyst.

[0074] Example 4 0.1907 g of ferric acetylacetone and 1.8398 g of anhydrous zinc chloride were added to 90 mL of formamide and ultrasonically dispersed for 30 min until completely dissolved. The solution was then transferred to a 150 mL high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 190 °C for 10 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting black solid product was washed several times by centrifugation with deionized water and ethanol, and then dried in a vacuum oven at 60 °C for 12 h to obtain the precursor powder.

[0075] The precursor powder was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere (flow rate 50 sccm), the temperature was increased to 1000℃ at a rate of 6℃ / min, and then pyrolyzed at this temperature for 1.6 h. Afterward, it was naturally cooled to room temperature, and the resulting black powder was ground uniformly to obtain an iron-nitrogen-carbon single-atom catalyst.

[0076] 100 mg of iron-nitrogen-carbon single-atom catalyst was weighed and dispersed in a mixed solvent of 40 mL deionized water and 20 mL ethanol. The mixture was ultrasonically treated for 1 h to form a uniform dispersion. 1 mL of 40 wt% hydrogen peroxide solution was added to the dispersion, and the mixture was stirred continuously for 30 min. The mixture was then transferred to a 100 mL high-pressure reactor and subjected to hydrothermal etching at 100 °C for 5 h. After the treatment, the product was washed and dried to obtain the etched catalyst.

[0077] The etched catalyst powder was placed in a ceramic boat and then placed in a tube furnace. Under a mixed atmosphere of 12% H₂ and 88% Ar (volume fraction) (total flow rate 50 sccm), the temperature was increased to 1000℃ at a rate of 6℃ / min and held for 1.6 h for heat treatment. After heat treatment, the powder was cooled to room temperature under a mixed atmosphere to obtain the hydrogen-passivated carbon-edge iron single-atom catalyst.

[0078] Example 5 0.1907 g of ferric acetylacetone and 1.4718 g of anhydrous zinc chloride were added to 90 mL of formamide and ultrasonically dispersed for 30 min until completely dissolved. The solution was then transferred to a 150 mL high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 170 °C for 15 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting black solid product was washed several times by centrifugation with deionized water and ethanol, and then dried in a vacuum oven at 60 °C for 12 h to obtain the precursor powder.

[0079] The precursor powder was placed in a ceramic boat and then placed in a tube furnace. Under an argon atmosphere (flow rate 50 sccm), the temperature was increased to 950℃ at a rate of 5℃ / min, and then pyrolyzed at this temperature for 2.3 h. Afterward, it was naturally cooled to room temperature, and the resulting black powder was ground uniformly to obtain an iron-nitrogen-carbon single-atom catalyst.

[0080] 100 mg of iron-nitrogen-carbon single-atom catalyst was weighed and dispersed in a mixed solvent of 20 mL deionized water and 20 mL ethanol. The mixture was ultrasonically treated for 1 h to form a uniform dispersion. 1 mL of 35 wt% hydrogen peroxide solution was added to the dispersion, and the mixture was stirred continuously for 30 min. The mixture was then transferred to a 100 mL high-pressure reactor and subjected to hydrothermal etching at 120 °C for 3 h. After the treatment, the product was washed and dried to obtain the etched catalyst.

[0081] The etched catalyst powder was placed in a ceramic boat and then placed in a tube furnace. Under a mixed atmosphere of 10% H₂ and 90% Ar (volume fraction) (total flow rate 50 sccm), the temperature was increased to 950°C at a rate of 5°C / min and held for 2.3 hours for heat treatment. After heat treatment, the powder was cooled to room temperature under a mixed atmosphere to obtain the hydrogen-passivated carbon edge iron single-atom catalyst.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A hydrogen passivation catalyst for carbon edges of iron single atoms, characterized in that, It includes a nitrogen-doped carbon support and iron; wherein the iron is anchored in the nitrogen-doped carbon support in an atomically dispersed form to form Fe-N4 active sites; the nitrogen-doped carbon support has abundant edge structures, and the carbon atoms on the edge structures are passivated by hydrogen atoms.

2. A method for preparing a hydrogen passivation carbon edge iron single-atom catalyst as described in claim 1, characterized in that, include: Ferric acetylacetone, zinc chloride, and formamide were mixed and subjected to a hydrothermal reaction to obtain a precursor powder. The precursor powder was pyrolyzed to obtain an iron-nitrogen-carbon single-atom catalyst. The iron-nitrogen-carbon single-atom catalyst was dispersed in a solvent, and then hydrothermal etching was performed after adding hydrogen peroxide solution to obtain the etched catalyst. The etched catalyst was heat-treated in an inert atmosphere containing hydrogen to obtain a hydrogen passivated carbon edge iron single-atom catalyst.

3. The method for preparing the hydrogen passivation carbon edge iron single-atom catalyst according to claim 2, characterized in that, When acetylacetone iron, zinc chloride and formamide are mixed, the molar concentration of zinc chloride is (0.05-0.15) mol / L and the molar concentration of acetylacetone iron is (0.004-0.006) mol / L.

4. The method for preparing the hydrogen passivation carbon edge iron single-atom catalyst according to claim 2, characterized in that, The hydrothermal reaction temperature is 160-190℃, and the hydrothermal reaction time is 10-18h.

5. The method for preparing the hydrogen passivation carbon edge iron single-atom catalyst according to claim 2, characterized in that, The pyrolysis treatment conditions are inert atmosphere conditions, the pyrolysis treatment temperature is 800-1000℃, the pyrolysis treatment heating rate is 3-6℃ / min, and the pyrolysis treatment time is 1.6-2.5h.

6. The method for preparing the hydrogen passivation carbon edge iron single-atom catalyst according to claim 2, characterized in that, The solvent is an aqueous ethanol solution, wherein the volume ratio of ethanol to water in the aqueous ethanol solution is 1:(0.5-2); the mass concentration of the hydrogen peroxide solution is 25%-40%, and after adding the hydrogen peroxide solution, the volume ratio of the hydrogen peroxide solution to the solvent is 1:(40-60).

7. The method for preparing the hydrogen passivation carbon edge iron single-atom catalyst according to claim 2, characterized in that, The temperature of the hydrothermal etching process is 100-120℃, and the time of the hydrothermal etching process is 3-12h.

8. The method for preparing the hydrogen passivation carbon edge iron single-atom catalyst according to claim 2, characterized in that, The hydrogen-containing inert atmosphere is a mixture of hydrogen and argon; wherein, in the mixture of hydrogen and argon, the volume fraction of hydrogen is 8%-12%.

9. The method for preparing the hydrogen passivation carbon edge iron single-atom catalyst according to claim 2, characterized in that, The heat treatment in the inert atmosphere containing hydrogen is carried out at a temperature of 800-1000℃, a heating rate of 3-6℃ / min, and a heat treatment time of 1.6-2.5h.

10. The application of the hydrogen passivated carbon edge iron single-atom catalyst of claim 1 in a proton exchange membrane fuel cell or a zinc-air battery.

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