Nickel-cobalt-based prussian blue derivative / porous cocoon biomass carbon composite electrocatalyst and preparation method and application thereof

Abstract

The application belongs to the technical field of electrocatalytic materials, and particularly relates to a nickel-cobalt-based prussian blue derivative / porous cocoon biomass carbon composite electrocatalyst as well as a preparation method and application thereof. The catalyst takes three-dimensional network nitrogen-doped porous carbon prepared by degumming and carbonization of a cocoon as a substrate, grows nickel-cobalt prussian blue analog precursor on the surface of the substrate in situ through a coprecipitation method, and is converted through sulfidation, phosphidation or selenization treatment by a gas phase deposition method. The method completely retains the three-dimensional interwoven network structure of the biomass, and the active components are uniformly dispersed in the form of nanoparticles and form a strong coupling interface with the carbon substrate. The composite material can be directly used as a self-supporting electrode for electrocatalytic oxygen evolution reaction, and the overpotential required for the 10 mA·cm ‑2 current density can be as low as 224 mV, and the Tafel slope is 53.90 mV·dec ‑1 , and the composite material has the advantages of high activity, high stability and low cost.

Description

Technical Field

[0001] This application relates to the field of electrocatalysts, and more specifically, to a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst, its preparation method, and its application. Background Technology

[0002] With the excessive consumption of fossil fuels, hydrogen energy has attracted much attention as a clean and renewable ideal energy source. Electrocatalytic water splitting for hydrogen production involves two half-reactions: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The OER involves a multi-step proton-electron coupling process with slow kinetics, which is a bottleneck limiting the efficiency of water electrolysis. Currently, noble metal-based catalysts such as IrO2 and RuO2 are the benchmark catalysts for OER, but their high cost and scarcity severely hinder large-scale commercial applications. Therefore, developing efficient, stable, and inexpensive non-noble metal OER catalysts is crucial.

[0003] Prussian blue analogues (PBAs) are considered promising precursor materials due to their open framework structure, tunable composition, and ease of preparation. High-performance electrocatalysts can be obtained through derivatization (e.g., phosphating, sulfidation, selenization) or morphology control. Meanwhile, combining active materials with carbon materials possessing high conductivity and high specific surface area is a common strategy for enhancing performance. Biomass carbon materials are widely available, renewable, and naturally rich in heteroatoms, making them considered potentially ideal supports.

[0004] However, the application of biomass carbon materials in the field of electrocatalysis, especially as self-supporting electrode carriers, faces significant limitations and technical obstacles in the current technology: Existing technologies extensively utilize biomass carbon materials, but their target applications are primarily concentrated in the lithium-ion battery field. For example, patent CN115411244A discloses a method for preparing nitrogen-doped porous hard carbon using silkworm cocoons as raw material, through KCl solution soaking, hydrothermal treatment, carbonization, and finally asphalt coating and secondary high-temperature carbonization. The resulting material is used as a battery anode. This process aims to optimize the lithium storage performance of the material, but its design principles fundamentally contradict the core requirements of electrocatalyst supports. Electrocatalyst supports require extremely high electronic conductivity, abundant open pores to load active materials and promote mass transfer, and a complete macroscopic structure to construct a self-supporting electrode. However, the asphalt coating step in the CN115411244A process severely clogs the material's pores, reduces the specific surface area, and covers surface active sites. The final pulverization process completely destroys the natural three-dimensional continuous network structure of the silkworm cocoon, and the resulting powder product must rely on binders, which completely fails to meet the requirements for constructing high-performance, binder-free integrated electrodes.

[0005] Furthermore, even disregarding the inherent defects of the aforementioned materials, existing methods for constructing composite catalysts often have shortcomings. For example, CN115976565B discloses a Fe5Ni4S8 nanoparticle / 3D porous carbon composite electrocatalyst, which is prepared by first synthesizing active nanoparticles and porous carbon supports separately, and then physically mixing them. This "post-composite" strategy results in weak bonding between the active component and the support, mainly through physical adsorption. This makes it prone to detachment during demanding electrocatalytic reactions (especially gas-producing OER reactions), affecting stability.

[0006] Furthermore, most non-precious metal catalysts still exist in powder form. When fabricating the working electrode, they need to be mixed with a conductive agent (such as carbon black) and a polymer binder (such as Nafion) and then coated onto a current collector (such as a glassy carbon electrode or nickel foam). The insulating binder can obscure some active sites, increase interfacial contact resistance, and the coating may peel off from the current collector during the reaction. These factors limit the full potential of the catalyst's performance and make it difficult to accurately assess its intrinsic activity.

[0007] Therefore, the research and application of OER catalysts still face three major challenges: First, it is difficult to achieve both high activity and low cost, and the dependence on precious metal materials has not been fundamentally resolved; second, the combination of highly efficient active components and support materials is mostly a simple physical mixing, resulting in insufficient interfacial stability; third, most catalysts still rely on traditional coating processes to fabricate electrodes, and the problems of active sites being obscured by binders and increased interfacial resistance remain prominent. A deeper problem is that even when using widely available biomass carbon materials, the post-processing techniques such as asphalt coating and pulverization adopted by existing technologies to adapt to battery applications precisely destroy the key structural advantages of the material as a high-performance electrocatalyst support, such as three-dimensional continuity and high specific surface area, making it unable to meet the requirements of self-supporting electrodes. In view of this, how to develop a novel composite catalyst that can circumvent all the above defects and its preparation method has become a critical technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0008] To address the aforementioned technical problems, this application provides a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst, its preparation method, and its application.

[0009] This application uses waste silkworm cocoons as raw materials to obtain a porous carbon substrate (PNCC) with an intrinsic three-dimensional nanofiber network structure and rich in nitrogen doping through carbonization. Using this PNCC as a self-supporting framework, a nickel-cobalt Prussian blue analogue (NiCo PBA) precursor is grown in situ via co-precipitation. Then, through sulfidation, phosphating, or selenization treatment, heteroatoms are introduced and the precursor is transformed into a highly active nickel-cobalt bimetallic compound (NiCoS, NiCoP, NiCoSe). Finally, an integrated composite electrocatalyst with stable structure, abundant active sites, high electron transport efficiency, and low cost is constructed for the efficient electrocatalytic oxygen evolution reaction (OER).

[0010] The technical solution adopted in this application is as follows: In a first aspect, this application provides a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst, comprising: Porous silkworm cocoon biomass carbon substrate, wherein the substrate is a nitrogen-doped porous carbon material with a three-dimensional interwoven network structure obtained by degumming and carbonizing waste silkworm cocoons; And, a nickel-cobalt-based Prussian blue derivative active component grown in situ and loaded on the porous silkworm cocoon biomass carbon substrate, the active component comprising at least one of nickel-cobalt bimetallic sulfides, phosphides or selenides; When the composite electrocatalyst is used for the electrocatalytic oxygen evolution reaction, at a current density of 10 mA·cm⁻¹ -2 The overpotential at the point is no higher than 280 mV.

[0011] Furthermore, the aforementioned active component is a nickel-cobalt bimetallic sulfide, and at a current density of 10 mA·cm⁻¹ -2 The overpotential at the point is no higher than 230 mV, and the Tafel slope is no higher than 55 mV·dec. -1 .

[0012] Furthermore, the specific surface area of ​​the aforementioned porous silkworm cocoon biomass carbon substrate is 300–400 m². 2 ·g -1 The pore size distribution is 0.7~2.0 nm.

[0013] Furthermore, the above-mentioned active components are nanoparticles or nanoclusters with a particle size of 5~50 nm, which are uniformly dispersed on the fiber surface and in the pores of the porous silkworm cocoon biomass carbon substrate.

[0014] Secondly, this application provides a method for preparing the above-mentioned nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst, which includes the following steps: S1. After removing the silkworm pupae and degumming the silkworm cocoons, carbonize them under an inert atmosphere to obtain a porous silkworm cocoon biomass carbon substrate that maintains a three-dimensional interwoven network structure. S2. The carbon substrate is immersed in a mixed aqueous solution containing soluble nickel salt and soluble cobalt salt, and then potassium cobalt cyanide solution is added. The mixture is stirred and reacted at 20~60 °C. A nickel cobalt Prussian blue analog precursor is grown in situ on the carbon substrate by co-precipitation. After washing and drying, the precursor / carbon substrate composite material is obtained. S3. The precursor / carbon substrate composite material and a sulfur source, phosphorus source or selenium source are placed in different temperature zones of a tube furnace and subjected to vapor deposition reaction under an inert atmosphere. After the reaction is completed, the mixture is cooled to room temperature to obtain the composite electrocatalyst.

[0015] Further, in step S1, the degumming treatment involves treating the silkworm cocoons with sodium carbonate solution and potassium ferrate solution at 80-100 °C for 1-3 hours respectively.

[0016] Further, in step S1, the carbonization treatment is as follows: under an inert atmosphere, with a gas flow rate of 70~100 mL / min, the degummed silkworm cocoons are kept at 600~900 ℃ for 1~3 hours.

[0017] Further, in step S2, the soluble nickel salt is nickel nitrate, nickel chloride, or nickel acetate, and the soluble cobalt salt is cobalt nitrate, cobalt chloride, or cobalt acetate; the molar ratio of the nickel salt to the cobalt salt is 1:0.5~2.

[0018] Further, in step S3, the mass ratio of the sulfur source, phosphorus source or selenium source to the porous silkworm cocoon biomass carbon substrate is (0.5~3):1; the temperature of the vapor phase deposition reaction is 300~400 ℃, and the reaction time is 1~2 hours.

[0019] Thirdly, this application provides an electrode whose working part is composed of a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst as described in any one of claims 1 to 3, without the need for a polymer binder.

[0020] Fourthly, this application provides an application of the above-mentioned nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst as an anode catalyst in a water electrolysis device.

[0021] In summary, this application has the following beneficial effects: This application uses waste silkworm cocoons as raw material, transforming their natural three-dimensional interwoven fibrous network structure into a nitrogen-doped porous carbon framework (PNCC) through degumming and carbonization. This framework not only perfectly inherits the macroporous channels of the biological template, facilitating mass transfer and bubble release, but its inherent nitrogen doping also simultaneously enhances conductivity and creates more active sites. On this substrate, a nickel-cobalt Prussian blue analogue (NiCo PBA) precursor is grown in situ via co-precipitation, ensuring a strong bond between the active component and the carbon substrate. Subsequently, sulfidation, phosphating, or selenization treatments are performed via vapor deposition, transforming the precursor into highly active nickel-cobalt bimetallic compounds (such as NiCoS, NiCoP, and NiCoSe) while introducing heteroatoms to further optimize the electronic structure of the active centers. This three-dimensional structure-in-situ growth-electronic doping design results in a unique heterogeneous interface with strong electronic coupling in the final composite material, laying the structural foundation for high catalytic activity.

[0022] When this catalyst is used in the oxygen evolution reaction (OER), it achieves a speed of 10 mA·cm⁻¹. -2 The overpotential at current density is no higher than 280 mV, and the Tafel slope is no higher than 98 mV·dec. -1 The performance indicators approach those of some noble metal benchmark catalysts and significantly outperform most reported non-noble metal materials. Its superior performance stems from a multi-dimensional synergistic effect: the three-dimensional porous PNCC substrate constitutes a high specific surface area and an excellent electronic conduction network; the uniformly dispersed nanoscale active components expose a large number of active sites; the synergistic effect of nickel-cobalt bimetals and heteroatoms (S, P, Se) optimizes the adsorption energy of reaction intermediates and enhances intrinsic activity. Crucially, the tight interfacial bonding formed through in-situ growth ensures the structural stability of the catalyst during vigorous electrocatalysis, effectively preventing the shedding and aggregation of active particles, thus achieving excellent long-term cycling stability and demonstrating great application potential in the field of efficient and stable water electrolysis for hydrogen production.

[0023] The entire preparation process starts with natural, renewable waste biomass and achieves the construction of a three-dimensional self-supporting carbon substrate and the robust loading of active components through relatively simple steps. This method uses low-cost raw materials and is environmentally friendly. It not only avoids the asphalt coating and pulverization steps that damage the three-dimensional structure in traditional processes, but also allows the final composite material to be directly used as an integrated electrode without polymer binders. This fundamentally solves the problems of active site shielding and increased interfacial resistance caused by the use of binders, providing an innovative technical path for designing high-performance, low-cost, and practical electrocatalysts. Attached Figure Description

[0024] Figure 1 The XRD patterns of the composite electrocatalysts prepared in Examples 1-3 and Comparative Example 1 on the silkworm cocoon carbon substrate (PNCC) in this application are shown. Figure 2 SEM images of the composite electrocatalysts prepared in Examples 1-3 and Comparative Example 1, based on the silkworm cocoon carbon substrate (PNCC) in this application. Figure 3 Raman spectra of the composite electrocatalysts prepared in Examples 1, 4, 5 and Comparative Example 1, which are based on the silkworm cocoon carbon substrate (PNCC) in this application. Figure 4 Fourier transform infrared spectra of the composite electrocatalysts prepared in Examples 1-3 and Comparative Example 1, which are based on the silkworm cocoon carbon substrate (PNCC) in this application. Figure 5 The nitrogen adsorption-desorption isotherm (BET) and its pore size distribution of the silkworm cocoon carbon substrate (PNCC) in the embodiments of this application are shown. Figure 6 Electrochemical test diagrams of the composite electrocatalysts prepared in Examples 1-3 and Comparative Examples 1-3, based on the silkworm cocoon carbon substrate (PNCC) in this application. Figure 7 This is a stability test diagram of the composite electrocatalyst (NiCoS / PNCC) prepared in Example 1 of this application. Detailed Implementation

[0025] The implementation scheme of this application will be described in detail below with reference to the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate this application and should not be regarded as limiting the scope of this application. Specific conditions not specified in the embodiments shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0026] The specific embodiments of this application are described in detail below. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0027] Example 1:

[0028] This embodiment describes a method for preparing a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst, which specifically includes the following steps: Step S1: Collect waste silkworm cocoons, remove silkworm pupae, place the treated silkworm cocoons in a beaker, and ultrasonically clean them with deionized water and anhydrous ethanol for 20 min in sequence, repeating three times. Dry them in a 60 ℃ oven for 12 h to obtain pretreated silkworm cocoons.

[0029] Step S2: Weigh 1.0 g of the pretreated silkworm cocoons from Step S1 into a 250 mL round-bottom flask, add 200 mL of a 0.02 mol / L sodium carbonate monohydrate solution, heat in a 100 ℃ oil bath for 60 min, cool to room temperature, wash the cocoons three times with deionized water, then add 200 mL of a 0.002 mol / L potassium ferrate solution, continue heating in a 100 ℃ oil bath for 60 min, cool to room temperature, wash the cocoons three times with deionized water, and dry in a 60 ℃ oven for 12 h to obtain degummed cocoons; place the degummed cocoons in the middle of a tube furnace, purge with nitrogen for 30 min to purge air, and in a nitrogen atmosphere, heat to 900 ℃ at a gas flow rate of 80 mL / min and a rate of 2 ℃ / min, hold at that temperature for 2 h, cool naturally to room temperature, wash three times with deionized water, and dry in a 60 ℃ oven for 12 h. h, a porous, nitrogen-doped cocoon carbon substrate (PNCC) was obtained.

[0030] Step S3: Cut the PNCC obtained in step S2 into 1×2 cm pieces. 2 The precursor was synthesized via coprecipitation. 0.1745 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and 0.2647 g of sodium citrate dihydrate (Na3C6H5O7·2H2O) were dissolved in 10 mL of water and sonicated for 5 min to form solution A. 0.1329 g of potassium cobalt cyanide (K3[Co(CN)6]) was dissolved in 10 mL of water and sonicated for 5 min to form solution B. 20 mL of anhydrous ethanol was added to solutions A and B respectively, and each solution was sonicated for 15 min to obtain solutions C and D. The pre-cut PNCC (1×2 cm) was then... 2 The substrate was placed in solution C. Under the condition of a 60 ℃ water bath, solution D was slowly added dropwise to solution C. The mixture was stirred for 30 min and allowed to stand at room temperature for 24 h. The substrate was collected, washed three times with deionized water, and dried in a 60 ℃ oven for 12 h to obtain the precursor (NiCo / PNCC) loaded on the surface of silkworm cocoons.

[0031] Step S4: Place 40 mg of the precursor (NiCo / PNCC) obtained in step S3 downstream of a tube furnace, and place 60 mg of sublimed sulfur as a sulfur source upstream of the tube furnace, wherein the mass ratio of sublimed sulfur to precursor is 1.5:1. Purge with nitrogen for 30 min to purge air. In a nitrogen atmosphere, heat to 300 ℃ at a gas flow rate of 80 mL / min and a rate of 2 ℃ / min, hold at that temperature for 2 h, and allow to cool naturally to room temperature. Wash the obtained product three times with deionized water and dry it in a 60 ℃ oven for 12 h to obtain the NiCoS / PNCC composite material.

[0032] Example 2:

[0033] This embodiment is a method for preparing a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst. The difference from Example 1 is that in step S4, 60 mg of sodium hypophosphite is placed upstream of the tube furnace as a phosphorus source, and the mass ratio of sodium hypophosphite to the precursor is 1.5:1, to obtain the NiCoP / PNCC composite material.

[0034] Example 3:

[0035] This embodiment is a method for preparing a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst. The difference from Example 1 is that in step S4, 60 mg of selenium powder is placed upstream of a tube furnace as a selenium source, and the mass ratio of selenium powder to precursor is 1.5:1, to obtain the NiCoSe / PNCC composite material.

[0036] Example 4:

[0037] This embodiment is a method for preparing a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst. The difference from Example 1 is that in step S4, 40 mg of sublimed sulfur is placed upstream of the tube furnace as a sulfur source, and the mass ratio of sulfur powder to precursor is 1:1, to obtain NiCoS / PNCC (1:1) composite material.

[0038] Example 5:

[0039] A method for preparing a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst, the difference from Example 1 is that in step S4, 80 mg of sublimed sulfur is placed upstream of a tube furnace as a sulfur source, and the mass ratio of sulfur powder to precursor is 2:1, to obtain NiCoS / PNCC (2:1) composite material.

[0040] To investigate the effects of sulfidation, phosphating, selenization, and porous silkworm cocoon biochar substrate on the performance of the product in this application, the following comparative experiments were conducted. Different electrocatalysts were prepared in the following comparative examples: Comparative Example 1: This comparative example is a method for preparing a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst. The difference from Example 1 is that in step S4, 40 mg of the precursor (NiCo / PNCC) is placed in the middle of a tube furnace. No sulfidation, phosphating, or selenization substances are placed upstream of the tube furnace. Nitrogen gas is introduced for 30 min to purge the air. Under the nitrogen atmosphere, the temperature is increased to 300 °C at a gas flow rate of 80 mL / min and a rate of 2 °C / min, held at this temperature for 2 h, and then naturally cooled to room temperature. The resulting product is washed three times with deionized water and dried in a 60 °C oven for 12 h to obtain the NiCoO / PNCC composite material.

[0041] Comparative Example 2: This comparative example is a method for preparing a nickel-cobalt-based Prussian blue derivative / carbon cloth composite electrocatalyst, which differs from Example 1 in that steps S1 and S2 are omitted, and the carbon cloth (CC) is cut into 1×2 cm pieces. 2 Instead of PNCC as the substrate, in step S3, a precursor (NiCo / CC) loaded with NiCo PBA on the surface of carbon cloth is obtained. In step S4, 50 mg of the precursor (NiCo / CC) is placed downstream of the tube furnace, and 75 mg of sublimed sulfur is placed upstream of the tube furnace as a sulfur source. The mass ratio of sublimed sulfur to precursor is 1.5:1, thus obtaining the NiCoS / CC composite material.

[0042] Comparative Example 3: This comparative example is a method for preparing a nickel-cobalt-based Prussian blue derivative / carbonized watermelon rind composite electrocatalyst, which differs from Example 1 in that: in step S1, the watermelon pulp is manually removed, and the treated watermelon rind is placed in a beaker and ultrasonically cleaned with deionized water and anhydrous ethanol for 20 min each time, repeated three times, and then dried in an oven at 60 ℃ for 24 h to obtain pretreated watermelon rind; in step S2, the pretreated watermelon rind is placed in the middle of a tube furnace, and nitrogen gas is introduced for 30 min to purge the air. Under the nitrogen atmosphere, the temperature is increased to 900 ℃ at a gas flow rate of 80 mL / min and a rate of 2 ℃ / min, held at that temperature for 2 h, and then naturally cooled to room temperature. After washing three times with deionized water, it is dried in an oven at 60 ℃ for 12 h to obtain carbonized watermelon rind (XGCC), which is then cut into 1×2 cm pieces. 2 In step S3, a NiCo PBA precursor (NiCo / XGCC) is loaded onto the surface of the obtained XGCC. In step S4, 200 mg of the obtained precursor NiCo / XGCC is placed downstream of a tube furnace, and 300 mg of sublimed sulfur is placed upstream of the tube furnace as a sulfur source. The mass ratio of sublimed sulfur to precursor is 1.5:1, thus obtaining the NiCoS / XGCC composite material.

[0043] Structural characterization and performance testing; XRD test; XRD patterns were analyzed for the silkworm cocoon carbon substrate (PNCC, provided in Example 1), the precursor (NiCo / PNCC, provided in Example 1), and samples from Examples 1-3 and Comparative Example 1. The results are as follows: Figure 1 As shown: PNCC exhibits a broad diffuse reflection peak without sharp diffraction peaks, indicating low crystallinity and primarily existing in an amorphous structure. Both NiCo / PNCC and NiCoO / PNCC retain the broad amorphous peaks of PNCC. The supported NiCo PBA has low crystallinity and exists as highly dispersed nanoparticles. The peak intensity of NiCoO / PNCC is slightly higher than that of NiCo / PNCC. After secondary calcination, the crystallinity is slightly improved, but it is still strongly masked by the amorphous peaks of the substrate.

[0044] The products after different treatments exhibited different structures: the phosphide (NiCoP / PNCC) remained amorphous; the selenide (NiCoSe / PNCC) formed a crystalline structure; while the sulfide with the best performance (NiCoS / PNCC) showed extremely low crystallinity, indicating that the nickel-cobalt sulfide was highly dispersed in the form of ultra-small particles and tightly bonded to the carbon substrate. This unique "ultra-small particle-amorphous carbon" strongly coupled structure is the fundamental reason why Example 1 achieved high specific surface area, rapid charge transport, and excellent catalytic activity.

[0045] SEM test; The samples from silkworm cocoon carbon substrate (PNCC), Examples 1-3, and Comparative Example 1 were subjected to SEM testing, and the results are as follows: Figure 2 As shown: Figure 2 a~ Figure 2 Image d shows the SEM image of NiCoS / PNCC. As can be seen from the image, the three-dimensional nanofiber network structure of the PNCC substrate is preserved. Nickel-cobalt sulfides are uniformly loaded on the surface and interfiber spaces of carbon fibers in the form of nano-scale clusters. The particles are tightly bonded to the carbon fiber interface, avoiding pore blockage caused by excessive loading of active materials, and providing abundant active sites for electrocatalytic water splitting.

[0046] Figure 2 e Figure 2 f is a SEM image of NiCoSe / PNCC. Ni-doped CoSe2 nanocrystalline particles are uniformly dispersed on the carbon fiber surface, exposing more active sites, which is beneficial to improving the kinetic performance of electrocatalysis.

[0047] Figure 2 g、 Figure 2 h is a SEM image of NiCoP / PNCC, showing that NiCoP nanoparticles are densely and uniformly distributed on the carbon fiber surface, with small particle size.

[0048] Figure 2 i、 Figure 2 j is a SEM image of NiCoO / PNCC, showing the nickel-cobalt alloy covering the carbon fiber surface in the form of small clusters.

[0049] Figure 2 k、 Figure 2 l is a SEM image of PNCC, showing a three-dimensional interwoven flexible nanofiber network structure.

[0050] SEM results confirmed that all composite materials fully retained the three-dimensional interwoven nanofiber network structure of the silkworm cocoon carbon substrate (PNCC), and different processing techniques guided the active components to exhibit differentiated loading morphologies. This retention of the substrate structure, along with the uniform loading and tight interfacial contact of the active phase, together constructs three-dimensional mass transfer channels and exposes abundant active sites, providing solid structural support for excellent electrocatalytic performance.

[0051] Raman spectroscopy test; Raman spectroscopy was performed on samples from silkworm cocoon carbon substrate (PNCC), precursor (NiCo / PNCC), Examples 1, 4, 5, and Comparative Example 1. Figure 3 As shown: Raman spectroscopy tests showed that all composite materials exhibited activity at ~1350 cm⁻¹. -1 (D peak) and ~1580 cm -1 The peaks at (G) all exhibit typical carbon characteristic peaks, and their intensity ratios (I) D / I G The peak value reflects the degree of defect and graphitization of the carbon substrate. Compared to the PNCC substrate and other samples, the D peak of Example 1 (NiCoS / PNCC) is not only significantly sharper but also has a significantly increased intensity, while the I peak... D / I G The value reached its highest (1.12). This indicates that the composite of the active components did not destroy the carbon substrate framework, but instead induced a large number of edge defects and heteroatom doping sites in the carbon framework. These abundant defect structures and highly disordered carbon lattices greatly increased the exposure of electrochemical active sites, effectively promoting rapid electron transfer, thus explaining the excellent oxygen evolution reaction performance of Example 1 from a microstructural perspective.

[0052] Fourier transform infrared spectroscopy test; Fourier transform infrared spectroscopy was performed on the silkworm cocoon carbon substrate (PNCC), the precursor (NiCo / PNCC), and the samples from Examples 1-3 and Comparative Example 1. Figure 4 As shown: At ~1630 cm -1 and ~1580 cm -1At this location, the characteristic peak of the C=C conjugate skeleton stretching vibration of PNCC corresponds to the position, indicating that the PNCC after high-temperature carbonization has formed a graphite-like aromatic structure. At ~2200 cm⁻¹ -1 At the location indicated, NiCo / PNCC exhibited C≡N stretching vibrations, signifying the successful synthesis of PBA. Furthermore, all samples also showed aromatic ring C=C skeletal vibrations, indicating that the PNCC carbon skeleton structure remained intact after loading with the nickel-cobalt-based compound.

[0053] Nitrogen adsorption-desorption isotherms and their pore size distribution were measured. Nitrogen adsorption-desorption isotherms and pore size distribution were measured on a silkworm cocoon carbon substrate (PNCC). The results are as follows: Figure 5 As shown, PNCC exhibits a typical type I isotherm. Under extremely low relative pressure (P / P0 < 0.1), the adsorption capacity increases rapidly and tends to plateau, indicating that it is dominated by a microporous structure with pore sizes concentrated in the range of 0.7–2.0 nm; its BET specific surface area is as high as 331.78 m². 2 ·g -1 The t-Plot micropore area is 317.60 m². 2 ·g -1 It accounts for 95.7% of the total specific surface area.

[0054] Electrochemical oxygen evolution test; Electrochemical oxygen evolution (OER) tests were performed on silkworm cocoon carbon substrate (PNCC), precursor (NiCo / PNCC), and samples from Examples 1-3 and Comparative Examples 1-3. Linear cyclic voltammetry (LSV) was used to record changes in electrode potential and current. The scan voltage range was set from 0 to 1.0 V for OER performance testing. Unless otherwise specified, the scan rate was 5 mV·s. -1 Five to ten scan rates were selected within the non-Radichterlian range for cyclic voltammetry (CV) curve testing. The scan rate was plotted on the x-axis, and half the difference between the oxidation and reduction current densities at the midpoint of the CV curve was plotted on the y-axis. The slope of the linear relationship was determined by the sample's double-layer capacitance C. dl All EIS tests in this application cover a frequency range of 0.01 Hz to 1000 kHz, with the AC signal amplitude set to 0.01 V. When evaluating stability using the Vt method, time-potential curves were recorded over a long period at a fixed current density. Smaller potential fluctuations indicate better catalyst durability and a longer service life.

[0055] The results are as follows Figure 6 As shown: Figure a is the LSV curve of the sample, Figure b is the Tafel slope, and Figure c is the double-layer capacitance (C). dl Figure d shows the electrochemical impedance spectroscopy (EIS), and the performance test data are shown in Table 1: Table 1. Comparison of performance of electrocatalytic oxygen evolution reaction (Note: * indicates that during the oxygen evolution reaction, 10 mA·cm) -2 (the overpotential corresponding to the current density) As can be seen from Table 1: The materials provided in Examples 1-3 of this application exhibit differences in oxygen evolution overpotential, Tafel slope, double-layer capacitance (Cdl), and charge transfer resistance (R). ct All three exhibited significant, step-like optimizations. Taking the optimal Example 1 (NiCoS / PNCC) as an example, its overpotential and Tafel slope were not only much lower than the substrate PNCC, but also comprehensively superior to Example 2 (phosphide, 276 mV) and Example 3 (selenide, 260 mV). Its C dl Value (43.29 mF·cm) -2 ) and the lowest R ct (2.134 Ω) together confirm that the material has both the largest electrochemical active area and the highest charge transport efficiency. This simultaneous breakthrough in activity, kinetics and conductivity reflects the universal advantages of heteroatom doping strategy and the ultimate effect of sulfidation treatment.

[0056] As can be seen from Example 1 and Comparative Example 1 (NiCoO / PNCC), both have the same precursor and substrate, but due to the absence of doped active components in Comparative Example 1, the performance exhibits a significant difference. The overpotential of Example 1 (224 mV) is reduced by more than 68 mV compared to Comparative Example 1 (292 mV), and the Tafel slope is reduced by approximately 10 mV·dec. -1 R ct Furthermore, the Ω decreased sharply from 6.324 Ω to 2.134 Ω. This indicates that the introduction of sulfur significantly optimized charge transfer and surface adsorption of oxygen-containing intermediates in the catalyst, thereby accelerating the reaction kinetics.

[0057] As can be seen from Example 1 and Comparative Example 2 (NiCoS / CC), both have NiCoS as their active component, but different supports (silkworm cocoon carbon PNCC vs. commercial carbon cloth CC). Example 1's performance completely surpasses Comparative Example 2: overpotential reduced by 109 mV, Tafel slope lower, and R... ctThe value is less than one-seventh of that of Comparative Example 2. This indicates that the nitrogen-doped carbon framework of the silkworm cocoon carbon substrate has high intrinsic conductivity, accelerating the OER kinetics. This demonstrates that the silkworm cocoon carbon substrate with its three-dimensional interwoven network structure used in this application is not an inert carrier. Its unique porous structure, nitrogen self-doping characteristics, and active components generate a strong synergistic effect, achieving efficient exposure of active sites and ultrafast electron transport—something unmatched by ordinary commercial carbon cloths. This highlights the decisive role of the specific design of the biomass substrate.

[0058] As can be seen from Example 1 and Comparative Example 3 (NiCoS / XGCC, watermelon rind carbon), even though they are both biomass carbon supports, their performance is vastly different. Comparative Example 3 exhibits a significantly higher overpotential (346 mV) and an extremely high Tafel slope (208.33 mV·dec). -1 This indicates that the reaction kinetics are severely hampered. This demonstrates that not all biomass carbon can replicate the effects of this application. The unique three-dimensional nanofiber network structure of silkworm cocoons and their inherent protein components (converted into nitrogen doping) constitute the indispensable structural basis for achieving high performance. This profoundly reveals the critical importance of raw material selection and structural inheritance in this application, and its effects are far beyond what can be expected or achieved using other biomass (such as watermelon rind).

[0059] In summary, the composite catalyst NiCoS / PNCC prepared in Example 1 possesses excellent active area and unique electronic structure, effectively improving charge transfer rate and surface mass transfer, thus exhibiting superior OER performance. The stability of the NiCoS / PNCC sample prepared in Example 1 was tested, as shown in the following figures... Figure 7 As shown, when the test current density is 10 mA·cm -2 At the corresponding voltage, the current density of NiCoS@PNCC showed almost no decay during a 56-hour long-term catalytic reaction, indicating its excellent stability in electrocatalytic OER.

[0060] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst, characterized in that, It includes: Porous silkworm cocoon biomass carbon substrate, wherein the substrate is a nitrogen-doped porous carbon material with a three-dimensional interwoven network structure obtained by degumming and carbonizing waste silkworm cocoons; And, a nickel-cobalt-based Prussian blue derivative active component grown in situ and loaded on the porous silkworm cocoon biomass carbon substrate, the active component comprising at least one of nickel-cobalt bimetallic sulfides, phosphides or selenides; When the composite electrocatalyst is used for the electrocatalytic oxygen evolution reaction, at a current density of 10 mA·cm⁻¹ -2 The oxygen evolution overpotential at the point is no higher than 280 mV.

2. The nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst according to claim 1, characterized in that, The active component is a nickel-cobalt bimetallic sulfide, and it operates at a current density of 10 mA·cm⁻¹. -2 The overpotential at the point is no higher than 230 mV, and the Tafel slope is no higher than 55 mV·dec. -1 .

3. The nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst according to claim 1 or 2, characterized in that, The active component is nanoparticles or nanoclusters with a particle size of 5-50 nm, which are uniformly dispersed on the fiber surface and in the pores of the porous silkworm cocoon biomass carbon substrate.

4. A method for preparing a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst as described in any one of claims 1 to 3, characterized in that, It includes the following steps: S1. After removing the silkworm pupae and degumming the silkworm cocoons, carbonize them under an inert atmosphere to obtain a porous silkworm cocoon biomass carbon substrate that maintains a three-dimensional interwoven network structure. S2. The carbon substrate is immersed in a mixed aqueous solution containing soluble nickel salt and soluble cobalt salt, and then potassium cobalt cyanide solution is added. A nickel cobalt Prussian blue analog precursor is grown in situ on the carbon substrate by co-precipitation. After washing and drying, a precursor / carbon substrate composite material is obtained. S3. The precursor / carbon substrate composite material and a sulfur source, phosphorus source or selenium source are placed in different temperature zones of a tube furnace and subjected to vapor deposition reaction under an inert atmosphere. After the reaction is completed, the mixture is cooled to room temperature to obtain the composite electrocatalyst.

5. The method for preparing the composite electrocatalyst according to claim 4, characterized in that, In step S1, the degumming process involves treating the silkworm cocoons with sodium carbonate solution and potassium ferrate solution at 80-100 °C for 1-3 hours, respectively.

6. The method for preparing the composite electrocatalyst according to claim 4, characterized in that, The carbonization process is as follows: under an inert atmosphere, with a gas flow rate of 70-100 mL / min, the degummed silkworm cocoons are kept at 600-900 ℃ for 1-3 hours.

7. The method for preparing the composite electrocatalyst according to claim 4, characterized in that, In step S2, the soluble nickel salt is nickel nitrate, nickel chloride, or nickel acetate, and the soluble cobalt salt is cobalt nitrate, cobalt chloride, or cobalt acetate; the molar ratio of the nickel salt to the cobalt salt is 1:0.5~2.

8. The method for preparing the composite electrocatalyst according to claim 4, characterized in that, In step S3, the mass ratio of the sulfur source, phosphorus source or selenium source to the porous silkworm cocoon biomass carbon substrate is 0.5~3:1; the temperature of the vapor phase deposition reaction is 300~400℃, and the reaction time is 1~2 hours.

9. An electrode, characterized in that, Its working part is composed of a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst as described in any one of claims 1 to 3, without the need for polymer binders.

10. The application of a nickel-cobalt-based Prussian blue derivative / porous silkworm cocoon biomass carbon composite electrocatalyst as described in any one of claims 1 to 3 as an anode catalyst in a water electrolysis device.

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