Preparation method and application of a double-metal sulfide / three-dimensional porous carbon catalyst

Abstract

The application discloses a preparation method and application of a bimetallic sulfide / three-dimensional porous carbon catalyst, relates to the technical field of water electrolysis catalysts, and comprises the following steps: cleaning melamine sponge to obtain clean melamine sponge; dissolving metal salt 1 and metal salt 2 in an ethanol aqueous solution, adding alkali and aniline monomers, and obtaining a precursor solution; completely immersing the clean melamine sponge in the precursor solution, carrying out constant-temperature hydrothermal reaction, and then sequentially carrying out washing and drying to obtain melamine sponge anchoring bimetallic ions; and passing in inert gas protection and carrying out high-temperature sulfuration treatment to obtain a three-dimensional porous carbon catalyst embedded with a bimetallic sulfide heterostructure. The catalyst comprises uniformly dispersed bimetallic sulfide nanoparticles and a sponge-like three-dimensional porous carbon carrier, and when applied to an electrocatalytic water splitting reaction, exhibits excellent bifunctional catalytic activity and stability, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis catalyst preparation technology, and particularly to a method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst and its application in the water electrolysis reaction. Background Technology

[0002] The catalytic electrolysis of water is a crucial process in hydrogen production technology, involving two half-reactions: the oxygen evolution reaction (OER) at the anolyte and the hydrogen evolution reaction (HER) at the cathodicly. Due to slow reaction kinetics and thermodynamic limitations, the actual water electrolysis reaction requires a large overpotential, resulting in high energy consumption and becoming one of the bottlenecks restricting the large-scale application of water electrolysis technology. Noble metals (Pt, Ir, Ru) and their compounds are considered the most effective electrocatalysts; however, their scarcity and high price pose significant challenges to their widespread adoption and sustainability in industrial applications. Therefore, developing low-cost, efficient, and stable non-noble metal catalysts has become a key research focus in the field of water electrolysis catalysts.

[0003] In recent years, transition metal sulfides (MoS2, FeS2, VS2, Ni3S2, Co9S8, etc.) have become popular candidates to replace precious metal catalysts due to their abundant reserves and low cost. Metal sulfides generally possess good electrical conductivity, strong catalytic activity, and relatively stable chemical properties, and are widely used in water splitting, fuel cells, batteries, and sensors. However, the catalytic activity of single metal sulfide catalysts is still limited by their internal structure, especially their poor catalytic performance in alkaline media. Typically, metal sulfides exhibit weak adsorption and dissociation of water molecules under alkaline conditions, resulting in unsatisfactory catalytic efficiency in HER and OER reactions. Furthermore, after prolonged use, the active sites of the catalyst are prone to degradation, leading to a rapid decline in catalytic performance.

[0004] To address these issues, researchers have attempted to construct bimetallic sulfide heterostructures to optimize electronic structure using interfacial effects. However, existing preparation methods often suffer from uneven dispersion of metal sulfides, weak heterostructure bonding, and insufficient conductivity and structural stability of the support, making it difficult to simultaneously meet the practical requirements of high activity and long lifetime. Therefore, developing a preparation technique that can achieve uniform dispersion of bimetallic sulfides, enhance heterostructure interfacial interactions, and provide stable support is of great significance for promoting the industrial application of water electrolysis catalysts. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying a bimetallic sulfide / three-dimensional porous carbon catalyst, so as to overcome the defects of the above-mentioned single metal sulfide.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst, comprising the following steps:

[0007] The melamine sponge is washed to obtain a clean melamine sponge;

[0008] Metal salt 1 and metal salt 2 were dissolved in an aqueous ethanol solution, and then alkali and aniline monomer were added to obtain a precursor solution.

[0009] The cleaned melamine sponge was completely immersed in the precursor solution, and after a constant temperature hydrothermal reaction, it was washed and dried in sequence to obtain a melamine sponge anchored with bimetallic ions.

[0010] The melamine sponge anchored with bimetallic ions was protected by an inert gas and subjected to high-temperature sulfidation to obtain a three-dimensional porous carbon catalyst with an embedded bimetallic sulfide heterostructure.

[0011] Compared with existing technologies, this invention introduces two metal salts and a sulfur source to form a metal sulfide heterostructure during the preparation of a bimetallic sulfide / three-dimensional porous carbon catalyst. The metal sulfide then combines with melamine sponge to form a composite material. The interfacial effect of this heterostructure promotes electron transfer and distribution, optimizes the active sites of the catalyst, and thus enhances its activity and stability. Furthermore, the surface of the metal sulfide nanoparticles can be protected by a thin carbon layer formed by the carbonization of the coordination stabilizer aniline monomer, further improving the catalyst's stability. Specifically, the introduction of the coordination stabilizer aniline monomer is based on two main functions: firstly, the amino group in its molecule can coordinate with metal ions, thereby effectively buffering OH groups. - The precipitation process of metal ions, through the regulation of nucleation and growth kinetics, yields nanoparticles with uniform size and distribution; secondly, aniline monomers adsorbed on the surface of metal species, after carbonization, can form a uniform thin layer of carbon coating on the sulfide surface, which helps to enhance the structural stability and conductivity of the material.

[0012] Furthermore, the melamine sponge support, after being subjected to isothermal hydrothermal reaction and sulfidation treatment, is transformed into a three-dimensional porous carbon framework with high conductivity and good mechanical strength. This provides stable support for the metal sulfides, preventing the aggregation and loss of metal particles. At the same time, it is beneficial to increase the contact between the material surface and the electrolyte and promote the timely discharge of gas. As a result, the prepared three-dimensional porous carbon catalyst with a bimetallic sulfide heterostructure exhibits excellent electrocatalytic water splitting performance (oxygen evolution reaction, hydrogen evolution reaction, and total water splitting reaction) and stability in alkaline electrolyte. Compared with traditional single catalysts, it can simultaneously optimize two reactions and improve the overall reaction efficiency.

[0013] Furthermore, the process of cleaning the melamine sponge is as follows: the melamine sponge is sequentially cleaned in deionized water and 0.1 mol / L... -1 The samples were ultrasonically cleaned for 30 minutes each in hydrochloric acid solution and anhydrous acetone.

[0014] Furthermore, the molar concentration of the dissolved metal salt 1 is 0.05~0.25 mol L. -1 ;

[0015] The molar concentration of the dissolved metal salt 2 is 0.015~0.075 mol L. -1 ;

[0016] The molar ratio of metal salt 1 to metal salt 2 is (2~8):1;

[0017] In the ethanol-water solution, the volume ratio of ethanol to water is 1:(1~4).

[0018] When the concentrations of metal salt 1 and metal salt 2 are selected within the above-mentioned ranges, it is beneficial to control the nucleation and growth process of metal species, thereby controlling the morphology and content of metal sulfides, obtaining nanomaterials with relatively uniform structures, and improving the catalytic activity of the catalyst. Meanwhile, the inventors discovered that when the molar concentration of the metal salt is too low, the hydrolysis rate of metal ions in the solution is too slow, resulting in a limited number of metal ions anchored in the melamine sponge, and ultimately a low content of metal sulfides formed in the material. Conversely, when the molar concentration of the metal salt is too high, the hydrolysis rate of metal ions is too fast, easily generating uneven, large-particle precipitates, making it difficult to control the distribution of metal ions anchored in the melamine sponge, ultimately leading to difficulties in controlling the morphology of metal sulfides in the material.

[0019] The metal salt 1 is a water-soluble nickel salt, including at least one of nickel nitrate hexahydrate, nickel acetate tetrahydrate, nickel chloride hexahydrate, nickel sulfate hexahydrate, and nickel oxalate dihydrate;

[0020] The metal salt 2 includes at least one of water-soluble cobalt salt, water-soluble iron salt, and water-soluble copper salt;

[0021] The water-soluble cobalt salt includes at least one of cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, cobalt chloride hexahydrate, cobalt sulfate heptahydrate, and cobalt oxalate dihydrate;

[0022] The water-soluble iron salt includes at least one of ferric nitrate hexahydrate, ferric acetate tetrahydrate, ferric chloride hexahydrate, and ferric sulfate nonahydrate;

[0023] The water-soluble copper salt includes at least one of copper nitrate hexahydrate, copper acetate monohydrate, copper chloride dihydrate, and copper sulfate pentahydrate.

[0024] This invention selects water-soluble nickel salts, cobalt salts, iron salts, and copper salts as raw materials for metal salt 1 and metal salt 2. These raw materials have high solubility and are relatively stable in water, which is conducive to the uniform anchoring of metal ions at the reaction sites of melamine sponge. In addition, the metal ion radii of these four types of transition metal salts are relatively close, which facilitates the formation of bimetallic sulfide heterointerfaces.

[0025] Further, the alkali includes hexamethylenetetramine, with a concentration of 0.005~0.015 g / mL in the solution. -1 ;

[0026] The molar ratio of hexamethylenetetramine to the aniline monomer is (1~5):1.

[0027] This invention uses hexamethylenetetramine as an alkali source and pH adjuster, which can gradually release OH- during hydrothermal processes. - This maintains the solution pH within a suitable range, thereby effectively regulating the hydrolysis rate of metal ions. Under these conditions, metal ions can slowly and uniformly nucleate and grow at the nitrogen-containing sites of the melamine sponge.

[0028] Regarding the concentration of hexamethylenetetramine, the inventors discovered that if the concentration of hexamethylenetetramine is too low, the hydrolysis reaction is slow, and the metal ions are difficult to effectively anchor to the carrier; conversely, if the concentration is too high, the metal ions will undergo instantaneous and violent hydrolysis, generating a large amount of precipitate, which also makes it impossible to achieve uniform anchoring on the carrier. Therefore, this invention controls the concentration of hexamethylenetetramine within the above-mentioned range, which can achieve uniform anchoring of metal ions on the carrier.

[0029] The ratio of hexamethylenetetramine to aniline is crucial. Both regulate the competitive balance between hydrolysis and precipitation and coordination stabilization. If the ratio is too low, the coordination stabilization effect is too strong, inhibiting the necessary hydrolysis of metal ions and making it difficult for them to effectively anchor on the melamine carrier. If the ratio is too high, hydrolysis and precipitation occur too quickly, and the coordination stabilization effect cannot be effectively exerted, also leading to disordered deposition of metal ions on the carrier.

[0030] Furthermore, the constant-temperature hydrothermal reaction is carried out in a reactor at a temperature of 60~120 ℃ for a time of 3~10 h.

[0031] This invention employs the aforementioned conditions for a isothermal hydrothermal reaction because the hydrothermal temperature directly determines the reaction kinetics. If the temperature is too low, the reaction driving force is insufficient, limiting nucleation and growth processes, resulting in incomplete precursor transformation and an insufficient number of metal species anchored on the melamine carrier. If the temperature is too high, the reaction rate is too fast, leading to uncontrolled nucleation and growth of nanoparticles, easily forming irregular and uneven aggregates. On the other hand, the hydrothermal time relates to the completeness of the reaction. If the time is too short, the binding reaction between the melamine carrier and metal ions is insufficient; if the time is too long, it may trigger excessive growth of metal species or even Ostwald ripening, similarly leading to particle agglomeration and affecting dispersibility and uniformity.

[0032] Furthermore, during the high-temperature vulcanization process, the inert gas includes at least one of nitrogen and argon;

[0033] The inert gas flow rate is 20~60 mL / min. -1 ;

[0034] The sulfur source is placed at the front end of the inert gas flow for high-temperature sulfidation treatment. The sulfur source includes at least one of thiourea, thioacetamide, sulfur powder, and sodium sulfide.

[0035] The heating rate during the high-temperature vulcanization is 1~10 °C / min. -1 The vulcanization temperature is 500~900 ℃, and the vulcanization time is 1~6 h.

[0036] A constant inert gas flow rate not only maintains the inert atmosphere but also ensures the effective transport and uniform distribution of the sulfur source precursor or its gaseous products within the reaction system, thereby guaranteeing the uniformity and sufficiency of the sulfidation reaction. A moderate heating rate helps the material skeleton shrink gently during pyrolysis, preventing structural collapse due to excessive thermal stress and ensuring the synchronous coordination of pyrolysis and sulfidation reactions. Sulfidation temperature and time jointly determine the crystallinity and grain size of the product: too low a temperature or too short a time leads to incomplete sulfidation and poor crystallinity; too high a temperature or too long a time easily causes abnormal grain growth, a decrease in specific surface area, and even morphological deterioration.

[0037] Secondly, the present invention provides a bimetallic sulfide / three-dimensional porous carbon catalyst, which is obtained by the above-mentioned preparation method; the catalyst uses a porous carbon framework as a support, and a bimetallic sulfide heterostructure is uniformly embedded therein; the three-dimensional porous carbon support is carbonized from melamine sponge, and is sponge-like, consisting of interconnected hollow microfibers with rough surfaces.

[0038] Compared with existing technologies, the catalyst supports three-dimensional porous carbon derived from melamine sponge, which has high conductivity and good mechanical strength, providing stable support for metal sulfides, avoiding the aggregation and loss of metal particles, and also facilitating increased contact between the material surface and the electrolyte and promoting timely gas discharge. The metal sulfide nanoparticles are uniformly dispersed in the three-dimensional porous carbon matrix, and their surfaces are wrapped by a thin carbon layer. A highly active heterogeneous interface is formed between different metal sulfides, which significantly enhances electronic interactions, effectively promotes the adsorption and dissociation process of water molecules, and achieves excellent catalytic performance for water electrolysis.

[0039] Thirdly, this invention provides the application of the aforementioned bimetallic sulfide / three-dimensional porous carbon catalyst in electrocatalytic water splitting reactions, wherein the electrocatalytic water splitting reactions include hydrogen evolution reaction, oxygen evolution reaction, and total water splitting reaction, and are particularly suitable for alkaline electrolytes (such as 1 mol·L⁻¹). -1 (KOH solution) system. Attached Figure Description

[0040] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0041] Figure 1 This is a schematic diagram illustrating the principle of adsorption and anchoring of metal ions by abundant nitrogen sites in melamine sponge.

[0042] Figure 2 A scanning electron microscope (SEM) image of melamine sponge;

[0043] Figure 3 SEM images of the three-dimensional porous carbon catalyst with embedded bimetallic sulfide heterostructure prepared in Example 2: a is a low-magnification SEM image, and b is a high-magnification SEM image.

[0044] Figure 4 Transmission electron microscopy (TEM) images of the three-dimensional porous carbon catalyst with embedded bimetallic sulfide heterostructure prepared in Example 2: a is a low-magnification TEM image, b is a high-resolution TEM image;

[0045] Figure 5 X-ray diffraction (XRD) patterns of the three-dimensional porous carbon catalysts with embedded bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with embedded monometallic sulfides prepared in Comparative Examples 1-2.

[0046] Figure 6Nitrogen adsorption-desorption curves of the three-dimensional porous carbon catalysts with embedded bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with embedded monometallic sulfides prepared in Comparative Examples 1-2.

[0047] Figure 7 The oxygen evolution catalytic performance of the three-dimensional porous carbon catalysts with intercalated bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2 in alkaline media are shown in Figure a: polarization curve; Figure b: oxygen evolution catalytic performance at a current density of 10 mA / cm². -2 Overpotential below;

[0048] Figure 8 Tafel curves of the oxygen evolution catalytic performance in alkaline media of the three-dimensional porous carbon catalysts with bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with monometallic sulfides prepared in Comparative Examples 1-2.

[0049] Figure 9 The figure shows a comparison of polarization curves before and after the oxygen evolution reaction stability test of the three-dimensional porous carbon catalyst with embedded bimetallic sulfide heterostructure prepared in Example 2. The inset is the stability curve of the I test.

[0050] Figure 10 The hydrogen evolution catalytic performance of the three-dimensional porous carbon catalysts with intercalated bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2 in alkaline media are shown in Figure a: polarization curve; Figure b: hydrogen evolution catalytic performance at a current density of -10 mA / cm². -2 Overpotential below;

[0051] Figure 11 Tafel curves of the hydrogen evolution catalytic performance of the three-dimensional porous carbon catalysts with embedded bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with embedded monometallic sulfides prepared in Comparative Examples 1-2 in alkaline media.

[0052] Figure 12 The hydrogen evolution reaction stability curve of the three-dimensional porous carbon catalyst with embedded bimetallic sulfide heterostructure prepared in Example 2 is shown in the test curve.

[0053] Figure 13 The complete water decomposition curve of the three-dimensional porous carbon catalyst with an embedded bimetallic sulfide heterostructure prepared in Example 2. Detailed Implementation

[0054] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0055] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0056] In this invention, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between the associated objects, indicating that three relationships can exist.

[0057] Example 1

[0058] A method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst CoNiS@NSC-0.5, wherein "0.5" indicates that the Co raw material is 0.5 mmol:

[0059] (1) The cut melamine sponge (20 mm × 10 mm × 40 mm) was placed in deionized water and 0.1 mol L water in sequence. -1 The melamine sponge was ultrasonically cleaned in hydrochloric acid solution and anhydrous acetone for 30 min, and then dried overnight in a vacuum drying oven at 80℃ to obtain a clean melamine sponge.

[0060] (2) Weigh 1.160 g (4.0 mmol) nickel nitrate hexahydrate and 0.145 g (0.5 mmol) cobalt nitrate hexahydrate, and completely dissolve them in a mixed solvent of 20 mL deionized water and 10 mL anhydrous ethanol. Add 0.308 g (2.2 mmol) hexamethylenetetramine until completely dissolved. Then, use a pipette to add 91 μL (1.0 mmol) aniline monomer solution dropwise. Continue stirring for 15 min to disperse it evenly. After complete dissolution, obtain the precursor solution.

[0061] (3) The precursor solution was transferred to a polytetrafluoroethylene-lined reactor. The clean melamine sponge was immersed in the inner liner of the reactor. The reactor was locked and placed in an oven at 90°C for a constant temperature hydrothermal reaction for 6 h. After the reaction was completed, the reactor was removed from the oven and allowed to cool naturally. The reactor was then opened, and the reacted melamine sponge was picked up with tweezers and thoroughly washed with an appropriate amount of deionized water and ethanol. The sponge was then placed in a vacuum drying oven and dried at 80°C for 0.5 h to obtain melamine sponge anchored with bimetallic ions.

[0062] (4) Place the melamine sponge anchored with bimetallic ions on the right side of the corundum ceramic boat, weigh 76.12 mg (1.0 mmol) of thiourea and place it on the left side of the ceramic boat. Then place the ceramic boat into a tube furnace and heat it at a constant flow rate (40 mL / min). -1 Under argon protection (with the end containing thiourea placed at the front of the gas flow), high-temperature vulcanization is performed at 2 °C for 1 minute. -1 The temperature was increased from room temperature to 700 °C and maintained for 2 h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the final three-dimensional porous carbon catalyst material with an embedded bimetallic sulfide heterostructure was collected, denoted as CoNiS@NSC-0.5.

[0063] Example 2

[0064] A method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst CoNiS@NSC-1.0, wherein "1.0" indicates that the Co raw material is 1.0 mmol:

[0065] (1) The cut melamine sponge (20 mm × 10 mm × 40 mm) was placed in deionized water and 0.1 mol L⁻¹ water in sequence. -1 The melamine sponge was ultrasonically cleaned in hydrochloric acid solution and anhydrous acetone for 30 min, and then dried overnight in a vacuum drying oven at 60℃ to obtain a clean melamine sponge.

[0066] (2) Weigh 1.160 g (4.0 mmol) nickel nitrate hexahydrate and 0.290 g (1.0 mmol) cobalt nitrate hexahydrate, and completely dissolve them in a mixed solvent of 20 mL deionized water and 10 mL anhydrous ethanol. Add 0.308 g (2.2 mmol) hexamethylenetetramine until completely dissolved. Then, use a pipette to add 91 μL (1.0 mmol) aniline monomer solution dropwise. Continue stirring for 15 min to disperse it evenly. After complete dissolution, obtain the precursor solution.

[0067] (3) The precursor solution was transferred to a polytetrafluoroethylene-lined reactor. The clean melamine sponge was immersed in the inner liner of the reactor. The reactor was locked and placed in an oven at 90°C for a constant temperature hydrothermal reaction for 6 h. After the reaction was completed, the reactor was removed from the oven and allowed to cool naturally. The reactor was then opened, and the reacted melamine sponge was picked up with tweezers and thoroughly washed with an appropriate amount of deionized water and ethanol. The sponge was then placed in a vacuum drying oven and dried at 80°C for 0.5 h to obtain melamine sponge anchored with bimetallic ions.

[0068] (4) Place the melamine sponge anchored to bimetallic ions on the right side of the corundum ceramic boat, weigh 76.12 mg (1.0 mmol) of thioacetamide and place it on the left side of the ceramic boat, then place the ceramic boat into a tube furnace and heat at a constant flow rate (40 mL / min). -1 Under argon protection (with the end containing thioacetamide placed at the front of the gas flow), high-temperature vulcanization is performed at 2°C for 2 min. -1 The temperature was increased from room temperature to 700℃ and maintained for 2 hours. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and the final three-dimensional porous carbon catalyst material with an embedded bimetallic sulfide heterostructure was collected, denoted as CoNiS@NSC-1.0.

[0069] Example 3

[0070] A method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst CoNiS@NSC-2.0, wherein "2.0" indicates that the Co raw material is 2.0 mmol:

[0071] (1) The cut melamine sponge (20 mm × 10 mm × 40 mm) was placed in deionized water and 0.1 mol L water in sequence. -1 The melamine sponge was ultrasonically cleaned in hydrochloric acid solution and anhydrous acetone for 30 min, and then dried overnight in a vacuum drying oven at 70 ℃ to obtain a clean melamine sponge.

[0072] (2) Weigh 1.160 g (4.0 mmol) nickel nitrate hexahydrate and 0.580 g (2.0 mmol) cobalt nitrate hexahydrate, and completely dissolve them in a mixed solvent of 20 mL deionized water and 10 mL anhydrous ethanol. Add 0.308 g (2.2 mmol) hexamethylenetetramine until completely dissolved. Then, use a pipette to add 91 μL (1.0 mmol) aniline monomer solution dropwise. Continue stirring for 15 min to disperse it evenly. After complete dissolution, obtain the precursor solution.

[0073] (3) The precursor solution was transferred to a polytetrafluoroethylene-lined reactor. The clean melamine sponge was immersed in the inner liner of the reactor. The reactor was locked and placed in an oven at 90°C for a constant temperature hydrothermal reaction for 6 h. After the reaction was completed, the reactor was removed from the oven and allowed to cool naturally. The reactor was then opened, and the reacted melamine sponge was picked up with tweezers and thoroughly washed with an appropriate amount of deionized water and ethanol. The sponge was then placed in a vacuum drying oven and dried at 80°C for 0.5 h to obtain melamine sponge anchored with bimetallic ions.

[0074] (4) Place the melamine sponge anchored with bimetallic ions on the right side of the corundum ceramic boat, weigh 76.12 mg of sulfur powder and place it on the left side of the ceramic boat, then place the ceramic boat into a tube furnace and heat it at a constant flow rate (40 mL / min). -1 Under argon protection (with the end containing sulfur powder placed at the front of the gas flow), high-temperature vulcanization is performed at 2°C for 2 minutes. -1 The temperature was increased from room temperature to 700℃ and maintained for 2 hours. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and the final three-dimensional porous carbon catalyst material with an embedded bimetallic sulfide heterostructure was collected, denoted as CoNiS@NSC-2.0.

[0075] Comparative Example 1

[0076] In Comparative Example 1, the only difference from Example 2 is that cobalt nitrate hexahydrate is not added, while the rest of the process remains unchanged, denoted as Ni3S2@NSC.

[0077] Comparative Example 2

[0078] In Comparative Example 2, the only difference from Example 2 is that nickel nitrate hexahydrate is not added, while the rest of the process remains unchanged, and it is denoted as Co9S8@NSC.

[0079] Performance testing

[0080] I. The catalyst materials prepared in Examples 1-3 and Comparative Examples 1-2 were analyzed using characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and surface area ratio (BET).

[0081] (1) Basic principles of materials design

[0082] Figure 1This diagram illustrates the principle of adsorption and anchoring of metal ions by abundant nitrogen sites in melamine sponge. Melamine sponge is a thermosetting melamine-formaldehyde resin with an ultra-high nitrogen content (>60 wt.%). It contains abundant imino groups and has a well-defined spatial structure, which can recognize and coordinate with metal ions, resulting in a composite material that uniformly anchors high-density metal ions. This invention also introduces aniline monomer as a coordination stabilizer, which forms a polymer thin layer around the metal precursor, thereby improving the dispersibility of metal species and preventing their aggregation. During the subsequent vulcanization process, it is transformed into a Co9S8 / Ni3S2 heterostructure.

[0083] (2) SEM analysis

[0084] Figure 2 SEM images of melamine sponge. Figure 3 SEM images of the three-dimensional porous carbon catalyst with an embedded bimetallic sulfide heterostructure prepared in Example 2: a is a low-magnification SEM image, and b is a high-magnification SEM image; from Figure 2 It can be observed that the melamine sponge exhibits a three-dimensional interconnected foam network structure composed of solid microfibers. Its surface is smooth and has abundant open channels, forming a macroscopic morphology similar to a "honeycomb," providing an efficient three-dimensional transport channel for the rapid passage and diffusion of gases and liquids. Figure 3 It can be observed that the prepared three-dimensional porous carbon catalyst CoNiS@NSC-1.0 with embedded bimetallic sulfide heterostructure exhibits a sponge-like morphology. The melamine sponge support is transformed into a three-dimensional porous carbon framework, the microfibers become hollow, the surface becomes very rough, and a large number of metal sulfide nanoparticles are loaded.

[0085] (3) TEM analysis

[0086] Figure 4 Transmission electron microscopy (TEM) images of the three-dimensional porous carbon catalyst CoNiS@NSC-1.0 with an embedded bimetallic sulfide heterostructure prepared in Example 2: a is a low-magnification TEM image, b is a high-resolution TEM image; from Figure 4 Medium- and low-magnification TEM images revealed a thin aniline-derived carbon protective layer on the surface of the metal sulfide nanoparticles in the prepared three-dimensional porous carbon catalyst CoNiS@NSC-1.0, which incorporates a bimetallic sulfide heterostructure. High-resolution TEM images further revealed the successful formation of the bimetallic sulfide heterostructure within the carbon framework, with clear lattice fringes of 2.98 Å spacing corresponding to the (331) crystal plane of Co9S8, while clear lattice fringes of 2.87 Å spacing correspond to the (110) crystal plane of Ni3S2.

[0087] (4) X-ray diffraction pattern analysis

[0088] The X-ray diffraction patterns of the three-dimensional porous carbon catalysts with intercalated bimetallic sulfide heterostructures prepared in Examples 1-4 and the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2 are shown in the figure. Figure 5 .

[0089] from Figure 5 It can be observed that a broad diffraction envelope peak is present at approximately 25.2°, which corresponds to the (002) crystal plane diffraction signal of the amorphous carbon support, indicating that it has a partially graphitized ordered structure. The three-dimensional porous carbon catalysts with embedded bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with embedded nickel metal sulfide prepared in Comparative Example 1 show significant diffraction peaks at 21.7° and 31.1°, which are highly consistent with the standard card (PDF#44-1418) of Ni3S2, respectively corresponding to Its (101) and (110) crystal planes, and the diffraction peaks at 29.9° and 52.2° are highly consistent with the standard card (PDF#75-2023) of Co9S8, corresponding to its (101) and (311) crystal planes respectively. Moreover, the diffraction peak intensity of Co9S8 is relatively stronger with the increase of Co addition. In contrast, the catalyst Ni3S2@NSC prepared in Comparative Example 1 did not show diffraction peaks of cobalt species, and the catalyst Co9S8@NSC prepared in Comparative Example 2 did not show diffraction peaks of nickel species.

[0090] It is noteworthy that no other obvious heterogeneous phase diffraction peaks were observed in the figure, indicating that three-dimensional porous carbon catalysts with embedded bimetallic sulfide heterostructures and three-dimensional porous carbon catalysts with embedded monometallic sulfides were successfully synthesized.

[0091] (5) Specific surface area test (BET)

[0092] Figure 6 Nitrogen adsorption-desorption curves of the three-dimensional porous carbon catalysts with bimetallic sulfide heterostructures prepared in Examples 1-4 and the three-dimensional porous carbon catalysts with monometallic sulfides prepared in Comparative Examples 1-2.

[0093] from Figure 6 As shown in the nitrogen adsorption-desorption isotherms, these materials all exhibit typical type IV isotherms and a distinct H4 type hysteresis loop in the medium-high pressure region (P / P0 > 0.4), indicating that the materials have a porous structure dominated by mesopores. This is attributed to the unique three-dimensional porous carbon framework, which provides a large specific surface area and abundant mesopore channels, exposing a wealth of active sites for catalytic reactions.

[0094] II. Verification of the effect of water electrolysis

[0095] Example 2

[0096] The catalysts prepared in the above examples and comparative examples were applied to the electrocatalytic water splitting performance test, including oxygen evolution reaction, hydrogen evolution reaction and total water splitting reaction. The specific methods are as follows:

[0097] (1) Weigh 2.0 mg of catalyst powder material and disperse it in 200 μL of isopropanol solution. Sonicate it in an ultrasonic cleaner for 30 min to obtain a uniformly dispersed catalyst ink.

[0098] (2) 2.0 μL of catalyst ink was dropped onto a polished glassy carbon electrode with a diameter of 3 mm. After the electrode dried naturally, 2.0 μL of Nafion solution (0.5 wt.%, isopropanol as solvent) was applied to the sample surface, resulting in a sample loading of 0.28 mg / cm³. -2 For the over-hydrolysis (OWS) test, carbon cloth (CC) was used as the support material, and the sample loading was 4.0 mg / cm³. -2 .

[0099] (3) At room temperature, at 1 mol·L⁻¹ -1 The catalytic performance of the catalyst was systematically evaluated in KOH (pH=14.0) solution using a conventional three-electrode configuration on a CHI760e workstation. A glassy carbon electrode coated with the catalyst was used as the working electrode, while a graphite carbon rod (5 mm diameter) and a saturated Ag / AgCl electrode served as the counter and reference electrodes, respectively. Before testing, argon gas was bubbled into the electrolyte for 30 min to remove oxygen and carbon dioxide. All electrode potentials were converted to their corresponding values ​​relative to the reversible hydrogen electrode (RHE) using the Nernst equation. To ensure reliable results, each sample was activated by 30 cyclic voltammetric scans at a scan rate of 100 mV s⁻¹ within the potential window before catalytic performance testing.

[0100] Unless otherwise specified in this test, all operating procedures are conventional methods well known to those skilled in the art.

[0101] Figure 7 The oxygen evolution catalytic performance of the three-dimensional porous carbon catalysts with intercalated bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2 in alkaline media is shown in Figure a: polarization curve; Figure b: oxygen evolution catalytic performance at a current density of 10 mA / cm². -2 Overpotential below;

[0102] from Figure 7As shown in Figure a, the three-dimensional porous carbon catalysts with intercalated bimetallic sulfide heterostructures prepared in Examples 1-3 exhibit excellent oxygen evolution reaction (OER) catalytic activity in alkaline media, showing a significant performance improvement compared to the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2. The performance of each sample at a current density of 10 mA·cm⁻¹ was also observed. -2 The overpotential at a current density of 10 mA·cm⁻¹ is shown in Figure b. The bimetallic sulfide heterostructure catalyst prepared in Example 2 exhibits catalytic performance very close to that of RuO₂ at a current density of 10 mA·cm⁻¹. -2 The required overpotential is only 336 mV, compared to a significantly lower overpotential of 470 mV and 407 mV for the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2. These results demonstrate that the heterostructure of bimetallic sulfides can modulate the electronic structure, redistribute interfacial charges, promote intermetallic electronic interactions, optimize the adsorption energy of reaction intermediates, form highly active catalytic sites, and significantly enhance catalytic reaction kinetics.

[0103] Figure 8 Tafel curves of oxygen evolution performance in alkaline media for the three-dimensional porous carbon catalysts with bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with monometallic sulfides prepared in Comparative Examples 1-2.

[0104] from Figure 8 As can be seen from the above, the three-dimensional porous carbon catalysts with embedded bimetallic sulfide heterostructures prepared in Examples 1-3 exhibit very fast kinetics in catalyzing the oxygen evolution reaction in alkaline media, with Tafel slopes ranging from 53 to 90 mV dec⁻¹. In contrast, the three-dimensional porous carbon catalyst with embedded bimetallic sulfide heterostructures prepared in Example 2 has a Tafel slope of only 53.2 mV dec⁻¹, which is much lower than that of commercially available RuO₂ catalysts, indicating that the bimetallic sulfide heterostructures have faster reaction kinetics.

[0105] Figure 9 This is a comparison of polarization curves before and after the oxygen evolution reaction stability test of the three-dimensional porous carbon catalyst with an embedded bimetallic sulfide heterostructure prepared in Example 2. The inset is the stability curve from the IT test. Figure 9 As can be seen, the polarization curves of the three-dimensional porous carbon catalyst CoNiS@NSC-1.0, which is embedded with a bimetallic sulfide heterostructure and prepared in Example 2, showed almost no change before and after the oxygen evolution reaction stability test, with the overpotential increasing by only 3 mV. Furthermore, the stability curves showed that after 28 h of stable catalysis, the catalytic activity remained essentially unchanged, and the current density remained consistently at 10 mAcm⁻¹ throughout the test. -2Nearby, it was confirmed that the prepared three-dimensional porous carbon catalyst with embedded bimetallic sulfide heterostructure exhibits excellent stability in the oxygen evolution reaction.

[0106] Figure 10 The hydrogen evolution catalytic performance of the three-dimensional porous carbon catalysts with intercalated bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2 in alkaline media are shown in Figure a: polarization curve; Figure b: hydrogen evolution catalytic performance at a current density of -10 mA cm⁻¹. -2 Overpotential below; from Figure 10 As shown in Figure a, the three-dimensional porous carbon catalysts with intercalated bimetallic sulfide heterostructures prepared in Examples 1-3 exhibit excellent catalytic activity for the hydrogen evolution reaction in alkaline media, and also show a significant performance improvement compared to the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2. The performance of each sample at a current density of -10 mA cm⁻¹ was also observed. -2 The overpotential at a current density of -10 mA cm⁻¹ is shown in Figure b. The catalyst material prepared in Example 2 exhibited the best catalytic performance at this current density. -2 The required overpotential is only 249 mV, compared to 319 mV and 371 mV, respectively, for the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2. These results indicate that, similar to the oxygen evolution reaction (OER), the bimetallic sulfide heterostructure can significantly enhance the hydrogen evolution performance of the catalyst, and also demonstrate that the prepared three-dimensional porous carbon catalysts with intercalated bimetallic sulfide heterostructures possess excellent bifunctional catalytic activity.

[0107] Figure 11 Tafel curves are shown for the hydrogen evolution performance of the three-dimensional porous carbon catalysts with intercalated bimetallic sulfide heterostructures prepared in Examples 1-3 and the three-dimensional porous carbon catalysts with intercalated monometallic sulfides prepared in Comparative Examples 1-2 in alkaline media; from Figure 11 As can be seen, the three-dimensional porous carbon catalyst with an embedded bimetallic sulfide heterostructure prepared in Example 2 exhibits very fast electrocatalytic hydrogen evolution reaction kinetics in alkaline media, with a Tafel slope of 126 mV dec. -1 The results were significantly lower than those of the materials prepared in Examples 1, 3, and Comparative Examples 1-2, further demonstrating that the bimetallic sulfide heterostructure and the appropriate molar ratio of metal salts play an important role in the reaction kinetics.

[0108] Figure 12 The hydrogen evolution reaction (HER) stability curve of the three-dimensional porous carbon catalyst with an embedded bimetallic sulfide heterostructure prepared in Example 2 was tested. Figure 12As can be seen from the above, the three-dimensional porous carbon catalyst with embedded bimetallic sulfide heterostructure prepared in Example 2 has excellent stability in the hydrogen evolution reaction, and its catalytic activity remains basically unchanged after 15 hours of stable catalysis.

[0109] Figure 13 The total water splitting curve of the three-dimensional porous carbon catalyst with an embedded bimetallic sulfide heterostructure prepared in Example 2; from Figure 13 As can be seen from the results, the three-dimensional porous carbon catalyst with an embedded bimetallic sulfide heterostructure prepared in Example 2 exhibits excellent performance in the whole water splitting application, achieving current densities of 10 and 20 mA cm⁻¹. -2 The overpotentials required are only 1.515 and 1.557 V (equivalent to 285 and 325 mV overpotentials, respectively), and the overpotential remains low even at high current densities. This indicates that the prepared three-dimensional porous carbon catalyst with embedded bimetallic sulfide heterostructure not only has high initial activity but also excellent kinetic performance. The polarization is small as the current density increases, which is crucial in practical applications.

[0110] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0111] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely exemplary descriptions of the invention as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst, characterized in that, Includes the following steps: The melamine sponge is washed to obtain a clean melamine sponge; Metal salt 1 and metal salt 2 were dissolved in an aqueous ethanol solution, and then alkali and aniline monomer were added to obtain a precursor solution. The cleaned melamine sponge was completely immersed in the precursor solution, and after a constant temperature hydrothermal reaction, it was washed and dried in sequence to obtain a melamine sponge anchored with bimetallic ions. The melamine sponge anchored with bimetallic ions was protected by an inert gas and subjected to high-temperature sulfidation treatment to obtain a three-dimensional porous carbon catalyst with an embedded bimetallic sulfide heterostructure. The molar concentration of the dissolved metal salt 1 is 0.05~0.25 mol L⁻¹; The molar concentration of the dissolved metal salt 2 is 0.015~0.075 mol L⁻¹; The molar ratio of metal salt 1 to metal salt 2 is (2~8):1; In the ethanol-water solution, the volume ratio of ethanol to water is 1:(1~4). The metal salt 1 is a water-soluble nickel salt; the metal salt 2 is a water-soluble cobalt salt; The alkali includes hexamethylenetetramine, and its concentration in the solution is 0.005~0.015 g mL⁻¹; The molar ratio of hexamethylenetetramine to the aniline monomer is (1~5):1; The constant-temperature hydrothermal reaction is carried out in a reaction vessel at a temperature of 60~120 ℃ for a time of 3~8 h. During the high-temperature vulcanization process, the inert gas flow rate is 20~60 mL min-1; the sulfur source is placed at the front end of the inert gas flow for high-temperature vulcanization treatment; the heating rate during high-temperature vulcanization is 1~10 ℃ min-1, the vulcanization temperature is 500~900 ℃, and the vulcanization time is 1~6 h.

2. The method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst according to claim 1, characterized in that, The process of cleaning the melamine sponge is as follows: the melamine sponge is ultrasonically cleaned for 30 min each in deionized water, hydrochloric acid solution with a concentration of 0.1 mol L-1, and anhydrous acetone.

3. The method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst according to claim 1, characterized in that, The water-soluble nickel salt includes at least one of nickel nitrate hexahydrate, nickel acetate tetrahydrate, nickel chloride hexahydrate, nickel sulfate hexahydrate, and nickel oxalate dihydrate.

4. The method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst according to claim 1, characterized in that, The water-soluble cobalt salt includes at least one of cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, cobalt chloride hexahydrate, cobalt sulfate heptahydrate, and cobalt oxalate dihydrate.

5. The method for preparing a bimetallic sulfide / three-dimensional porous carbon catalyst according to claim 1, characterized in that, The inert gas includes at least one of nitrogen and argon; The sulfur source includes at least one of thiourea, thioacetamide, sulfur powder, and sodium sulfide.

6. A bimetallic sulfide / three-dimensional porous carbon catalyst, characterized in that, The catalyst is obtained by the preparation method according to any one of claims 1 to 5; the catalyst uses a porous carbon framework as a support, and a bimetallic sulfide heterostructure is uniformly embedded therein; The three-dimensional porous carbon carrier is made of carbonized melamine sponge, and is sponge-like, composed of interconnected hollow microfibers with rough surfaces.

7. The application of the bimetallic sulfide / three-dimensional porous carbon catalyst according to claim 6 in the electrocatalytic water splitting reaction, wherein the electrocatalytic water splitting reaction includes hydrogen evolution reaction, oxygen evolution reaction and total water splitting reaction.

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