A fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst and a preparation method thereof

Abstract

The application discloses a fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst, which is composed of a fluorine-doped double transition metal phosphide heterojunction active phase and a carrier, the fluorine-doped double transition metal phosphide heterojunction active phase is in a relatively rough nanowire structure, and the nanowire is attached to the carrier; the double transition metal phosphide in the double transition metal phosphide heterojunction is Ni2P and CoP, and the two phases constitute the heterojunction. The fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst has high intrinsic activity, good conductivity and excellent stability, can stably and efficiently catalyze the water electrolysis hydrogen evolution reaction under a full pH condition, has excellent stability and durability, and the comprehensive catalytic performance is close to that of a noble metal Pt / C catalyst.

Description

Technical Field

[0001] This invention belongs to the field of energy catalytic conversion materials technology, specifically relating to a fluorine-doped and heterojunction synergistic modification of hydrogen evolution electrocatalyst and its preparation method. Background Technology

[0002] The depletion of fossil fuels and increasing environmental pressures have spurred an urgent global effort to develop green and renewable energy sources. Hydrogen, due to its high energy density (~142 MJ / kg), is a suitable candidate. -1 With zero pollutant emissions, water electrolysis has become a promising sustainable energy carrier. Water electrolysis is an ideal technology for large-scale hydrogen production, involving two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. However, in practical production applications, its high energy consumption is a major constraint. Therefore, researching high-efficiency hydrogen evolution catalysts to reduce the energy consumption of water electrolysis is one of the key foundations for promoting the development of water electrolysis technology.

[0003] Platinum (Pt) and its based materials are considered state-of-the-art electrocatalysts for the hydrogen evolution reaction (HER), but their high cost, scarcity, and low reaction efficiency in alkaline or neutral solutions limit their large-scale application. Various water sources, such as industrial wastewater, freshwater, seawater, and domestic water, can serve as ideal feedstocks for electrocatalytic water splitting. Meanwhile, industrial electrolysis devices, microbial electrolyzers, and proton exchange membrane technologies operate in strongly alkaline, neutral, and strongly acidic media, respectively, prompting greater attention to the development of inexpensive and efficient non-precious metal-based HER electrocatalysts across the entire pH range. An ideal electrocatalyst should exhibit excellent performance under different pH conditions. Therefore, developing highly efficient electrocatalysts suitable for various electrolysis environments is crucial.

[0004] To address these challenges, various non-noble metal transition metal-based hydrogen evolution reaction (HER) catalysts, including phosphides, sulfides, nitrides, carbides, and oxides, have been developed to replace noble metal-based HER electrocatalysts. Among them, transition metal phosphides (TMPs) have emerged as a potential alternative to noble metal-based HER catalysts due to their high activity, abundant reserves, and similarity to hydrogenases. However, due to their low electronic conductivity, sluggish kinetics, and insufficient stability, the catalytic performance of TMPs remains unsatisfactory compared to noble metal-based catalysts. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a fluorine-doped and heterojunction-synergistic modified hydrogen evolution electrocatalyst and its preparation method, aiming to obtain a catalyst with high intrinsic catalytic activity, good conductivity and stability, capable of efficiently and stably catalyzing the hydrogen evolution reaction of water electrolysis under all pH conditions, with comprehensive catalytic performance approaching that of noble metal Pt / C catalysts.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0007] A fluorine-doped and heterojunction-synergistic modified hydrogen evolution electrocatalyst, the catalyst comprising a fluorine-doped dual transition metal phosphide heterojunction active phase and a support, wherein the fluorine-doped dual transition metal phosphide heterojunction active phase exhibits a relatively coarse nanowire structure, the nanowires being attached to the support; the dual transition metal phosphides in the dual transition metal phosphide heterojunction are Ni2P and CoP, the two phases constituting the heterojunction; the active phase of the dual transition metal phosphide heterojunction is a transition metal phosphide; the transition metal refers to at least two of Fe, Co, Ni, W, Cr, Mo, V, and Mn.

[0008] Preferably, the transition metal is Co and Ni; the carrier is nickel foam, copper foam, transition metal mesh, hydrophilic carbon paper or porous carbon material; preferably, it is nickel foam.

[0009] Preferably, the dual transition metal phosphide is a uniformly distributed nanowire array heterojunction, and the nanowire size of the fluorine-doped dual transition metal phosphide heterojunction is 5–20 μm.

[0010] The preparation method of the above-mentioned fluorine-doped and heterojunction synergistic modification hydrogen evolution electrocatalyst includes the following steps:

[0011] (1) The support is added to a 0.05-0.5M aqueous solution of a transition metal salt and hydrothermally reacted at 90-180℃ for 4-20 hours to grow a dual transition metal phosphide precursor on the surface of the support. The precursor is washed with deionized water to remove the aqueous solution containing the transition metal salt, and then vacuum dried. The transition metal salt refers to at least one of the following: halide, nitrate, sulfate, aminosulfonate, acetate, or oxygen-containing or oxygen-free acid salt of a transition metal. The transition metal refers to at least two of the following: Fe, Co, Ni, W, Cr, V, Mo, or Mn.

[0012] (2) The precursor obtained after drying in step (1) is phosphated with phosphorus source at a mass ratio of 1:1 to 2 at 300 to 450°C under an inert atmosphere. A dual transition metal phosphide heterojunction is generated in situ on the surface of the dual transition metal phosphide precursor, and a rougher nanowire structure with a larger active area is obtained at the same time.

[0013] (3) The dual transition metal phosphide heterojunction obtained in step (2) is immersed in an aqueous solution of 0.5-2M fluorine source to carry out fluorine doping reaction, and after drying, a fluorine-doped and heterojunction synergistic modified hydrogen evolution electrocatalyst is obtained.

[0014] Preferably, when the transition metals in step (1) are Co and Ni, the support is added to a 0.05-0.5M transition metal salt aqueous solution, followed by the addition of urea and ammonium fluoride (NH4F). The mass ratio of the added urea to the added Ni transition metal salt aqueous solution is 1:1. The mass ratio of the added ammonium fluoride to the added Co transition metal salt aqueous solution is 0.1:1. During the hydrothermal process, the urea creates an alkaline environment in the aqueous solution, causing Ni and Co to deposit hydroxides. Ammonium fluoride acts as a surface modifier, ensuring that the deposited hydroxides are evenly distributed on the surface of the support.

[0015] Preferably, the hydrothermal reaction time in step (1) is 6 hours; the concentration of the transition metal salt aqueous solution in step (1) is 0.2 M.

[0016] Preferably, the phosphorus source in step (2) is sodium hypophosphite; the precursor obtained after drying in step (2) is mixed with the phosphorus source at a mass ratio of 1:1.5; the inert atmosphere refers to an argon atmosphere; the phosphating reaction time in step (2) is 1 to 3 hours, preferably 2 hours.

[0017] Preferably, the aqueous solution of the fluorine source in step (3) is a 1M sodium fluoride aqueous solution; the fluorine doping reaction time in step (3) is 2 to 4 hours, preferably 2 hours.

[0018] As mentioned above, fluorine doping and heterojunction synergistic modification of hydrogen evolution electrocatalysts are used in the field of electrocatalytic water desorption of hydrogen.

[0019] As described above, the method is as follows: the fluorine-doped and heterojunction-modified hydrogen evolution electrocatalyst is loaded on nickel foam or carbon paper for hydrogen production by water electrolysis. The reaction time is not fixed. During the reaction, hydrogen gas will be evolved around the catalyst, generating bubbles. The reaction temperature is room temperature, and the reaction environment is a full pH environment (acidic, alkaline, and neutral). When the number of bubbles decreases or no bubbles are generated, it indicates that the reaction is over and the catalyst needs to be replaced.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The hydrothermal synthesis of the dual transition metal phosphide precursor on the surface of the support material in this invention generates a large number of nanowires during the heating process, which increases the specific surface area of ​​the material and provides more active sites for subsequent catalysts. By controlling the phosphating reaction conditions, a synergistic catalyst is constructed by growing a heterogeneous phosphide structure in situ. At the same time, the phosphated catalyst exhibits a dense nanowire structure, exposing more active sites. In addition, after fluorine doping, the catalyst is attached to the support with a relatively rough nanowire structure, which is conducive to the full contact between the catalyst and the electrolyte, thereby promoting the occurrence of electrocatalytic reaction. Thus, the intrinsic activity, the number of active sites, and the conductivity are optimized simultaneously. The hydrothermally synthesized precursor material contains a large amount of water of crystallization. The dehydration reaction that occurs during the heating process leads to the generation of a large number of nanowires, which further increases the specific surface area of ​​the material and provides more active sites.

[0022] (2) The preparation method of the present invention uses readily available raw materials, has a simple process, low cost, and is easy to mass-produce;

[0023] (3) The fluorine-doped and heterojunction-modified hydrogen evolution electrocatalyst obtained in this invention has high intrinsic activity, good conductivity and excellent stability. It can carry out stable and efficient hydrogen evolution reaction of water electrolysis under all pH conditions, and has excellent stability and durability. Its comprehensive catalytic performance is close to that of noble metal Pt / C catalyst. Attached Figure Description

[0024] Figure 1 The images show the scanning electron microscope (SEM) morphology of the hydrothermal NiCo precursor obtained in step (1) of Example 1 of this invention, the phosphated sample Ni2P / CoP(b) in step (2), and the target catalyst F-Ni2P / CoP(c) in step (3).

[0025] Figure 2 The X-ray diffraction patterns are those of the hydrothermal NiCo precursor (a) obtained in step (1) of Example 1 of the present invention, the phosphated sample Ni2P / CoP (b) in step (2), and the target catalyst F-Ni2P / CoP (b) in step (3).

[0026] Figure 3 The images show the transmission electron microscope (TEM) morphology (a), high-resolution electron microscope (HEM) image (b), selected area electron diffraction (C), and energy-dispersive X-ray diffraction (EDX) spectrum of the target sample F-Ni2P / CoP obtained in Example 1 of this invention.

[0027] Figure 4The X-ray photoelectron spectra of the phosphating sample Ni2P / CoP obtained in Example 1 of this invention and the target catalyst F-Ni2P / CoP are shown below: (a) full spectrum; (b) F1s spectrum of the target catalyst F-Ni2P / CoP; (c) Ni 2p spectrum; (d) Co 2p spectrum; (e) P2p spectrum and (f) O 1s spectrum.

[0028] Figure 5 A comparison of hydrogen evolution reaction polarization curves for different phosphating samples Ni2P / CoP-1, Ni2P / CoP-2, and the phosphating sample Ni2P / CoP (Ni2P / CoP-1.5) obtained in step (2) of Example 1 (a); a comparison of hydrogen evolution reaction polarization curves for different catalysts 0.5-F-Ni2P / CoP-1.5, 1-F-Ni2P / CoP-1.5 (the target catalyst F-Ni2P / CoP obtained in step (3) of Example 1), and 2-F-Ni2P / CoP-1.5 (b).

[0029] Figure 6 The following figures compare the polarization curves of hydrogen evolution reaction of different samples 1-F-Ni2P / CoP-1.5, Ni2P / CoP-1.5 and Pt / C catalyst in 1M KOH electrolyte (pH=14): (a); (b) Impedance spectroscopy results of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at -0.03V (vs. reversible hydrogen electrode); (c) Relationship between capacitive current density and potential scan rate of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at open circuit potential; and (d) Comparison of polarization curves of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 after ECSA normalization.

[0030] Figure 7 A comparison of the hydrogen evolution reaction polarization curves of different samples 1-F-Ni2P / CoP-1.5, Ni2P / CoP-1.5 and Pt / C catalyst in 0.5M H2SO4 electrolyte (pH=0) (a); impedance spectroscopy results of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at -0.03V (vs. reversible hydrogen electrode) (b); relationship between capacitive current density and potential scan rate of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at open circuit potential (c); and comparison of the polarization curves of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 after ECSA normalization (d).

[0031] Figure 8The following figures compare the polarization curves of the hydrogen evolution reaction of different samples 1-F-Ni2P / CoP-1.5, Ni2P / CoP-1.5 and Pt / C catalyst in 1M PBS electrolyte (pH=7): (a); (b) impedance spectroscopy results of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at -0.03V (vs. reversible hydrogen electrode); (c) the relationship between capacitive current density and potential scan rate of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at open circuit potential; and (d) the polarization curves of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 after ECSA normalization.

[0032] Figure 9 For step (3) of Example 1, the target catalyst F-Ni2P / CoP was tested under conditions of 1M KOH, 0.5M H2SO4, and 1M PBS at a current density of 100 mA cm⁻¹. -2 The results of the stability test (a); the X-ray diffraction pattern (b) and X-ray photoelectron spectrum (c) of the target catalyst F-Ni2P / CoP after 55 hours of durability test.

[0033] Figure 10 The image shows the scanning electron microscope (SEM) morphology of the target catalyst F-Ni2P / CoP in step (3) of Example 1 after a 55-hour durability test in 1M KOH (a), 0.5M H2SO4 (b), and 1M PBS (c). Detailed Implementation

[0034] The specific embodiments are described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise specified, the raw materials and reagents used in the examples are commercially available. The precious metal Pt / C catalyst was purchased from Suzhou Shengernuo Technology Co., Ltd.

[0035] Example 1

[0036] A method for preparing a fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst, comprising the following steps:

[0037] (1) With a thickness of 1.85 mm and a surface density of 610 ± 30 g / m³ 2 Using NF nickel foam with a pore size of 0.20–0.80 mm as a carrier, nickel foam (1.5 × 4 cm) was used to... 2After ultrasonic cleaning with ethanol for 10 minutes, the nickel foam was activated with 3M hydrochloric acid solution for 10 minutes. The activated nickel foam was then placed in a 50mL hydrothermal reactor with 30mL of a deionized aqueous solution containing Ni(NO3)2·6H2O (0.6g), Co(NO3)2·6H2O (2g), urea (0.6g), and NH4F (0.2g) (the total concentration of Ni and Co transition metals in the deionized aqueous solution was 0.2M). The reaction was carried out at a constant temperature of 160℃ for 6 hours. After natural cooling to room temperature, a dual transition metal phosphide precursor was grown on the support surface. The precursor was washed with deionized water to remove the residual Co and Ni transition metal salt aqueous solution on the precursor surface, and then vacuum dried at 60℃ for 6 hours to obtain the hydrothermal NiCo precursor. The scanning electron microscope image of the hydrothermal NiCo precursor is shown below. Figure 1 As shown in (a), the X-ray diffraction pattern is as follows: Figure 2 As shown in (a);

[0038] (2) Take 1.0 g of the hydrothermal NiCo precursor obtained in step (1) and place it in the middle of a quartz boat. Then, place 1.5 g of sodium hypophosphite (NaH2PO2) upstream of the quartz boat. Under an argon atmosphere, heat the solution to 350 °C at a rate of 2 °C per minute for phosphating. After constant temperature treatment for 2 h, a dual transition metal phosphide heterojunction is generated in situ on the surface of the dual transition metal phosphide precursor. At the same time, a rougher nanowire structure with a larger active area is obtained, thus preparing the phosphated sample Ni2P / CoP. The scanning electron microscope image of the phosphated sample Ni2P / CoP is shown below. Figure 1 As shown in (b), the X-ray diffraction pattern is as follows: Figure 2 (b) shows the X-ray photoelectron spectrum. Figure 4 (a);

[0039] (3) The phosphating sample Ni2P / CoP obtained in step (2) was immersed in a 1M sodium fluoride aqueous solution for fluorine doping for 2 hours. After thoroughly washing off the sodium fluoride aqueous solution remaining on the catalyst surface with deionized water, it was vacuum dried at room temperature for 2 hours to obtain the fluorine-doped and heterojunction synergistic modified hydrogen evolution electrocatalyst F-Ni2P / CoP, which is the target catalyst. The scanning electron microscope image of the target catalyst F-Ni2P / CoP is shown below. Figure 1 As shown in (c), the X-ray diffraction pattern is as follows: Figure 2 As shown in (b), the transmission electron microscope (TEM) morphology image is as follows: Figure 3 (a) The high-resolution electron microscope image is shown below. Figure 3 (b) As described, the selected area electron diffraction pattern is as follows: Figure 3 As shown in (c), the energy-dispersive X-ray spectrum is as follows: Figure 3 As shown in (d), the X-ray photoelectron energy F1s spectrum is as follows: Figure 4 As shown in (b).

[0040] Example 2

[0041] A method for preparing a fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst, comprising the following steps:

[0042] (1) With a thickness of 1.85 mm and a surface density of 610 ± 30 g / m³ 2 Using NF foam with a pore size of 0.20–0.80 mm as a carrier, nickel foam (1.5 × 4 cm) was... 2 After ultrasonic cleaning with ethanol for 10 minutes, the nickel foam was activated with 3M hydrochloric acid solution for 10 minutes. The activated nickel foam was then placed in a 50mL hydrothermal reactor with 20mL of 3.6mmol / L hydrochloric acid solution containing Co(NO3)2·6H2O (0.05M, the concentration of transition metal in hydrochloric acid solution). The reaction was carried out at a constant temperature of 100℃ for 20h. After natural cooling to room temperature, a dual transition metal phosphide precursor was grown on the support surface. The precursor was washed with deionized water to remove the residual transition metal salt solution on the surface of the precursor and then vacuum dried at 60℃ for 6h to obtain the hydrothermal NiCo precursor.

[0043] (2) Take 1.0g of the hydrothermal NiCo precursor obtained in step (1) and place it in the middle of the quartz boat. Then place 1g of sodium hypophosphite (NaH2PO2) upstream of the quartz boat and heat it to 400℃ at a rate of 2℃ per minute under an argon atmosphere for phosphating reaction. After constant temperature treatment for 1h, a dual transition metal phosphide heterojunction is generated in situ on the surface of the dual transition metal phosphide precursor. At the same time, a rougher nanowire structure with a larger active area is obtained, and the phosphated sample Ni2P / CoP is obtained.

[0044] (3) The phosphating sample Ni2P / CoP obtained in step (2) was immersed in a 2M sodium fluoride aqueous solution for fluorine doping for 3 hours. After thoroughly washing off the sodium fluoride aqueous solution remaining on the surface of the target catalyst with deionized water, it was vacuum dried at room temperature for 2 hours to obtain the fluorine-doped and heterojunction synergistic modified hydrogen evolution electrocatalyst F-Ni2P / CoP.

[0045] Scanning electron microscopy observation ( Figure 1 (a) It was found that, after hydrothermal reaction treatment, a large number of nanowires grew on the surface of the nickel foam and self-assembled to form a nanoarray. According to XRD analysis ( Figure 2 In section a), the diffraction peaks of the nanowire material correspond to Ni(OH)2 and Co(CO3). 0.5 The hydrothermal NiCo precursor underwent phosphating at 350℃ for 2 hours, and the morphology of the sample showed no significant change. Figure 1 (b); After fluorination treatment, a relatively rough nanowire structure was formed on the catalyst surface. Figure 1 As shown in c), the length of the heterojunction nanowires of the present invention is 5–20 μm.

[0046] XRD analysis ( Figure 2 Figure b) shows that after phosphating the hydrothermal NiCo precursor at 350℃ for 2 hours, the NiCo precursor is transformed into Ni2P and CoP crystal phases. Fluorination treatment by immersion in sodium fluoride solution transforms the phosphated sample Ni2P / CoP into the target catalyst F-Ni2P / CoP. The peak position of the target catalyst does not change, indicating that the doping of fluorine atoms has no significant effect on the crystal structure of Ni2P / CoP.

[0047] Transmission electron microscopy observation ( Figure 3 (a) further confirmed the nanowire structure of the carbonization-treated target catalyst, with an average diameter of approximately 80 nm; according to high-resolution electron microscopy analysis ( Figure 3 In section b), Ni₂P and CoP form a uniformly distributed nanowire array heterojunction, selected area electron diffraction analysis (... Figure 3 c) confirmed the coexistence of Ni₂P and CoP. Energy-dispersive X-ray spectroscopy (EDS) Figure 3 Analysis of the sample (d) revealed that the main elements, such as nickel, cobalt, and phosphorus, were distributed very uniformly in the target catalyst, indicating the presence of numerous heterostructure interfaces within the F-Ni2P / CoP catalyst. Simultaneously, fluorine was also uniformly distributed throughout the observation area, demonstrating that fluorine atoms had been successfully doped into the heterostructure.

[0048] Based on X-ray photoelectron spectroscopy analysis ( Figure 4 The target catalyst F-Ni2P / CoP contains elements such as Ni, Co, P, and F, while no trace of fluorine was detected in the phosphating sample Ni2P / CoP, indicating that fluorine has been successfully doped into the catalyst. Figure 4 a and Figure 4 (b) Figure 4 c shows the Ni 2p of the target catalyst F-Ni2P / CoP. 3 / 2 The spectrum can be decomposed into Ni δ+ (δ close to 0), NiO x The combination of Ni and satellite peaks confirms that Ni 2 The presence of +. Similarly, Co 2p 3 / 2 Spectrum ( Figure 4 In the middle d), it can be fitted as Co. δ+ CoO x And satellite peaks also confirmed Co 2+ The existence of P 2p spectrum ( Figure 4 e) then belongs to P δ+ 2p 3 / 2 and 2p 1 / 2 This indicates the presence of P bonded to Ni or Co. δ+ Co δ+ With P δ+The joint detection confirmed the formation of Ni2P and CoP. Simultaneously, the O1s spectrum was studied (…). Figure 4 In the O 1s spectrum (f), two peaks were observed, one at 533.1 eV, attributed to a PO bond, and the other at 531.7 eV, indicating the presence of a MO bond (M = Ni, Co). These observations are consistent with XRD and transmission electron microscopy results.

[0049] Electrocatalytic performance test of the fluorine-doped and heterojunction synergistic modified hydrogen evolution electrocatalyst F-Ni2P / CoP obtained in Example 1:

[0050] A standard three-electrode system was used, with a carbon rod as the counter electrode, Hg / HgO as the reference electrode in alkaline environments, and saturated calomel as the reference electrode in acidic and neutral environments. The fluorine-doped and heterojunction-modified hydrogen evolution electrocatalyst prepared in Example 1 was used as the working electrode, with Pt / C as the control. The electrolytes were 1 M KOH (pH = 14), 0.5 M H₂SO₄ (pH = 0), and 1 M PBS (pH = 7). All electrochemical test data were collected using an electrochemical workstation, and all electrochemical tests were performed at room temperature.

[0051] To compare the effects of different phosphating reaction conditions on the activity of the samples, three sets of control tests were set up according to the mass ratio of hydrothermal NiCo precursor to sodium hypophosphite obtained in step (1) of 1:1, 1:1.5 (the phosphating sample Ni2P / CoP obtained in step (2) of Example 1, labeled as Ni2P / CoP-1.5), and 1:2. (That is, in step (2), 1.0g of hydrothermal NiCo precursor obtained in step (1) was placed in the middle of the quartz boat, and then 1g and 2g of sodium hypophosphite (NaH2PO2) were placed upstream of the quartz boat, respectively. The rest of the operation was the same as in steps (1) and (2) of Example 1, and phosphating samples Ni2P / CoP with the mass ratio of hydrothermal NiCo precursor to sodium hypophosphite obtained in step (1) of 1:1 and 1:2 were obtained, respectively labeled as Ni2P / CoP-1 and Ni2P / CoP-2). The test results ( Figure 5 Figure a) shows that the phosphated sample Ni2P-CoP-1.5 has the best hydrogen evolution activity.

[0052] Furthermore, under the optimal phosphorus source mass ratio (i.e., under the operation steps of Example 1), the effects of different fluorine source concentrations of 0.5M, 1M (the target catalyst F-Ni2P / CoP obtained in step (3) of Example 1, labeled as 1-F-Ni2P / CoP-1.5) and 2M on the activity of the target sample were compared (i.e., in step (3), the phosphated sample Ni2P / CoP obtained in step (2) was immersed in 0.5M and 2M sodium fluoride aqueous solutions for fluorine doping for 2 hours to obtain different catalysts, labeled as 0.5-F-Ni2P / CoP-1.5 and 2-F-Ni2P / CoP-1.5, respectively). The test results ( Figure 5 Figure b) shows that the target catalyst (1-F-Ni2P / CoP-1.5) with a fluorine source concentration of 1M has the best activity.

[0053] Results of hydrogen evolution reaction polarization curve test ( Figure 6 , Figure 7 and Figure 8 The results show that the target catalyst 1-F-Ni2P / CoP-1.5 exhibits excellent electrocatalytic activity for the hydrogen evolution reaction, requiring only 44 mV of hydrogen evolution overpotential to reach 10 mA / cm² in 1.0 M KOH. 2 current density ( Figure 5 In section a), only a hydrogen evolution overpotential of 46 mV is required to reach 10 mA / cm² in an acidic environment. 2 current density ( Figure 6 In section a), a hydrogen evolution overpotential of 96 mV is required in a neutral environment to achieve 10 mA / cm². 2 ( Figure 7 (a) These results collectively demonstrate that the target catalyst possesses excellent catalytic activity, approaching that of noble metal Pt / C catalysts. Figure 6 b, Figure 7 b and Figure 8 Figure b shows the impedance spectroscopy test results. Under the full pH environment, the charge transfer resistance of the target catalyst is lower than that of the phosphating sample Ni2P / CoP-1.5, indicating that the electron transfer rate inside 1-F-Ni2P / CoP-1.5 is faster, which shows that the target sample has good conductivity. Figure 6 c, Figure 7 c and Figure 8 Figure c shows the relationship between the capacitance current density and the potential scan rate of the target catalyst 1-F-Ni2P / CoP-1.5 and the phosphating sample Ni2P / CoP-1.5 at open circuit potential. Compared with the phosphating sample, the double layer capacitance of the target sample is improved to a certain extent, that is, the electrochemical specific surface area is increased. This should be attributed to the unique heterostructure of the 1-F-Ni2P / CoP-1.5 nanowires, which provides the most active sites. Figure 6 d, Figure 7 d and Figure 8 In the figure, d is the polarization curve after electrochemical specific surface area normalization, which shows that the target sample 1-F-Ni2P / CoP-1.5 has the highest intrinsic activity compared to the phosphating sample.

[0054] Figure 9 In Example 1, step (3) was used to test the stability of the target catalyst F-Ni2P / CoP. A standard three-electrode system was employed, with a carbon rod as the counter electrode, Hg / HgO as the reference electrode in alkaline conditions, and saturated calomel as the reference electrode in acidic and neutral conditions. A constant current of 100 mA was applied to the catalyst, and the stability of the catalyst was measured by the change in potential. The results showed that after 55 hours of constant current measurement (100 mA / cm²), the stability of the catalyst was determined. 2 After 55 hours (in alkaline, acidic, and neutral electrolytes), the activity of the target catalyst did not show significant decline, indicating that the target catalyst has good stability. Figure 9 Figures b and c show the X-ray diffraction pattern and X-ray photoelectron spectrum after stability testing. Apart from a slight decrease in peak intensity, there is basically no obvious peak shift, indicating that the physical phase of the target catalyst has not changed, demonstrating that the target catalyst prepared in Example 1 of this invention has strong phase stability.

[0055] Figure 10 The scanning electron microscope (SEM) images show the morphology of the target catalyst F-Ni2P / CoP obtained in step (3) of Example 1 after stability testing in alkaline (a), acidic (b), and neutral (c) environments. The results show that the morphological characteristics of the catalyst did not change significantly, indicating that the target catalyst F-Ni2P / CoP has good structural stability.

[0056] For hydrogen evolution electrocatalysts operating under all pH conditions, the three key criteria for evaluating their electrocatalytic performance are intrinsic catalytic activity, conductivity, and stability. Traditional research on non-precious metal catalysts primarily focuses on one or two of these aspects. This invention provides measures to simultaneously optimize all three aspects and offers a simple and inexpensive preparation method.

[0057] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst, characterized in that: The catalyst consists of a fluorine-doped dual transition metal phosphide heterojunction active phase and a support. The fluorine-doped dual transition metal phosphide heterojunction active phase has a relatively rough nanowire structure, and the nanowires are attached to the support. The dual transition metal phosphide heterojunction consists of Ni2P and CoP, with the two phases constituting the heterojunction. The active phase of the dual transition metal phosphide heterojunction is a transition metal phosphide, where the transition metals refer to Co and Ni. The preparation method of the fluorine-doped and heterojunction synergistic modified hydrogen evolution electrocatalyst includes the following steps: (1) Add the carrier to a 0.05~0.5 M transition metal salt aqueous solution, then add urea and ammonium fluoride (NH4F), and perform a hydrothermal reaction at 90~180℃ for 4~20 h, then wash and dry with water; the transition metal salt refers to at least one of the halides, nitrates, sulfates, aminosulfonates and acetates of transition metals; the transition metal refers to Co and Ni; (2) The precursor obtained after drying in step (1) is phosphated with phosphorus source at a mass ratio of 1:1~2 at 300~450 °C under an inert atmosphere to generate a dual transition metal phosphide heterojunction in situ on the surface of the dual transition metal phosphide precursor. (3) The dual transition metal phosphide heterojunction obtained in step (2) is immersed in an aqueous solution of 0.5~2 M fluorine source to carry out fluorine doping reaction, and after drying, the fluorine-doped and heterojunction synergistic modified hydrogen evolution electrocatalyst is obtained.

2. The fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst according to claim 1, characterized in that: The carrier is nickel foam, copper foam, transition metal mesh, hydrophilic carbon paper, or porous carbon material.

3. The fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst according to claim 1, characterized in that: The carrier is nickel foam.

4. The fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst according to claim 1, characterized in that: The dual transition metal phosphide is a uniformly distributed nanowire array heterojunction, and the nanowire size of the fluorine-doped dual transition metal phosphide heterojunction is 5~20 μm.

5. The fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst according to claim 1, characterized in that: In step (1), the mass ratio of the added urea to the added Ni transition metal salt aqueous solution is 1:1, and the mass ratio of the added ammonium fluoride to the added Co transition metal salt aqueous solution is 0.1:

1.

6. The fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst according to claim 1, characterized in that: The hydrothermal reaction time in step (1) is 6 h; the concentration of the transition metal salt aqueous solution in step (1) is 0.2 M.

7. The fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst according to claim 1, characterized in that: The phosphorus source in step (2) is sodium hypophosphite; the precursor obtained after drying in step (2) is in a mass ratio of 1:1.5 with the phosphorus source; the inert atmosphere refers to an argon atmosphere; the phosphating reaction time in step (2) is 1~3 h.

8. The fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst according to claim 1, characterized in that: The phosphating reaction time in step (2) is 2 hours.

9. The fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst according to claim 1, characterized in that: The aqueous solution of the fluorine source in step (3) is a 1 M sodium fluoride aqueous solution; the fluorine doping reaction time in step (3) is 2~4 h.

10. The fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst according to claim 1, characterized in that: The fluorine doping reaction time in step (3) is 2 hours.

11. The application of the fluorine-doped and heterojunction-synergistic modified hydrogen evolution electrocatalyst as described in any one of claims 1-10 in the field of electrocatalytic water desorption hydrogen.

12. The application as described in claim 11, characterized in that: The fluorine-doped and heterojunction-modified hydrogen evolution electrocatalyst is supported on nickel foam or carbon paper and used for hydrogen production by water electrolysis. The reaction time is not fixed, and hydrogen gas will be evolved around the catalyst during the reaction. The reaction temperature is room temperature, and the reaction environment is a full pH environment.

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