Fluorine-doped and heterojunction synergistic modified hydrogen evolution electrocatalyst and preparation method thereof

Abstract

The invention discloses a fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst, the catalyst 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 of a rough nanowire structure, and nanowires are attached to the carrier; the double transition metal phosphide in the double transition metal phosphide heterojunction is Ni2P and CoP, and the double transition metal phosphide and the CoP form the heterojunction. The fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst has high intrinsic activity, good conductivity and excellent stability, can perform stable and efficient water electrolysis catalytic hydrogen evolution reaction under a full pH condition, has excellent stability and durability, and has comprehensive catalytic performance close to that of a noble metal Pt / C catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy catalytic conversion materials, and in particular relates to a fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst and a preparation method thereof. Background Art

[0002] The depletion of fossil fuels and increasing environmental pressure have prompted the world to urgently develop green and renewable energy. Hydrogen has a high energy density (~142MJ kg -1 ) and zero pollutant emissions, becoming a promising sustainable energy carrier. Water electrolysis is an ideal technology for large-scale hydrogen production. Water electrolysis involves two half reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. However, in actual production applications, it is limited by its high reaction energy consumption. Therefore, studying high-efficiency hydrogen evolution catalysts to reduce the energy consumption of water electrolysis reaction is one of the key foundations for promoting the development of water electrolysis technology.

[0003] Platinum (Pt) and its based materials are considered to be the most advanced 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, fresh water, seawater, and domestic water, can be used as ideal raw materials for electrocatalytic water splitting. At the same time, industrial electrolysis devices, microbial electrolysis cells, and proton exchange membrane technology operate in strongly alkaline, neutral, and strongly acidic media, respectively, which has prompted people to pay more attention to the development of cheap and efficient non-precious metal-based hydrogen evolution reaction (HER) electrocatalysts over the entire pH range. An ideal electrocatalyst should exhibit excellent performance under different pH conditions. Therefore, it is crucial to develop efficient electrocatalysts suitable for various electrolysis environments.

[0004] To address these challenges, various non-noble transition metal-based 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 become a potential choice to replace 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 with noble metal-based catalysts. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst and a preparation method thereof, aiming to obtain a catalyst having high intrinsic catalytic activity, good conductivity and stability, which can efficiently and stably catalyze the hydrogen evolution reaction by electrolysis of water under all pH environments, and whose comprehensive catalytic performance is close to that of the precious metal Pt / C catalyst.

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

[0007] A fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst, the catalyst consisting of a fluorine-doped double transition metal phosphide heterojunction active phase and a carrier, the fluorine-doped double transition metal phosphide heterojunction active phase presenting a relatively rough nanowire structure, the nanowire being attached to the carrier; the double transition metal phosphides in the double transition metal phosphide heterojunction are Ni2P and CoP, the two phases constituting the heterojunction; the double transition metal phosphide heterojunction active phase is a phosphide of a transition metal; 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 nickel foam.

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

[0010] The preparation method of the fluorine-doped and heterojunction-synergistically modified hydrogen evolution electrocatalyst comprises the following steps:

[0011] (1) adding a carrier to a 0.05-0.5M transition metal salt aqueous solution, hydrothermally reacting at 90-180°C for 4-20 hours, growing a double transition metal phosphide precursor on the carrier surface, washing the transition metal salt aqueous solution remaining on the precursor surface with deionized water, and then vacuum drying; the transition metal salt refers to at least one of a transition metal halide, nitrate, sulfate, aminosulfonate, acetate, or an oxygen-containing or oxygen-free acid salt of a transition metal; the transition metal refers to at least two of Fe, Co, Ni, W, Cr, V, Mo, or Mn;

[0012] (2) subjecting the precursor obtained after drying in step (1) to a phosphorus source in a mass ratio of 1:1-2 to a phosphating reaction at 300-450° C. in an inert atmosphere, thereby in situ generating a double transition metal phosphide heterojunction on the surface of the double transition metal phosphide precursor and simultaneously obtaining a relatively rough nanowire structure with a relatively large active area;

[0013] (3) Immersing the double transition metal phosphide heterojunction obtained in step (2) in an aqueous solution of a 0.5-2 M fluorine source to perform a fluorine doping reaction, and after drying, obtaining a fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst.

[0014] Preferably, when the transition metal in step (1) is Co and Ni, the carrier is added to a 0.05-0.5M transition metal salt aqueous solution, and then urea and ammonium fluoride (NH4F) are added, and 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; urea makes the aqueous solution alkaline during the hydrothermal process, so that Ni and Co precipitate hydroxides, and ammonium fluoride is a surface modifier, so that the precipitated hydroxides are evenly distributed on the carrier surface.

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

[0016] Preferably, the phosphorus source in step (2) is sodium hypophosphite; the precursor obtained after drying in step (2) and the phosphorus source are in a mass ratio of 1:1.5; the inert atmosphere refers to 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 synergistically modified hydrogen evolution electrocatalysts are used in the field of electrocatalytic water decomposition of hydrogen.

[0019] The application method is as follows: the fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst is loaded on nickel foam or carbon paper and used for electrolysis of water to produce hydrogen. The reaction time is not fixed. During the reaction, hydrogen will be evolved around the catalyst to generate bubbles. The reaction temperature is room temperature and the reaction environment is a full pH environment (acidic, alkaline and neutral environment). When the bubbles decrease or no bubbles are generated, it means that the reaction is over and the catalyst needs to be replaced.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention hydrothermally synthesizes a double transition metal phosphide precursor on the surface of the carrier material, and 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 the subsequent catalyst; the phosphide heterostructure is grown in situ by regulating the phosphating reaction treatment conditions to construct a synergistic catalyst; at the same time, the phosphated catalyst presents a dense nanowire structure, exposing more active sites; in addition, after fluorine doping, the catalyst is attached to the carrier in a relatively rough nanowire structure, which is conducive to the full contact between the catalyst and the electrolyte, thereby promoting the occurrence of the electrocatalytic reaction; thereby achieving simultaneous optimization of the three elements of intrinsic activity, the number of active sites, and conductivity; the hydrothermally synthesized precursor material contains a large amount of crystal water, and the dehydration reaction occurring during the heating process will lead to the generation of a large number of nanowires, further increasing the specific surface area of ​​the material, thereby providing more active sites;

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

[0023] (3) The fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst obtained in the present invention has high intrinsic activity, good conductivity and excellent stability. It can carry out stable and efficient water electrolysis catalytic hydrogen evolution reaction under all pH conditions, and has excellent stability and durability. The comprehensive catalytic performance is close to that of the precious metal Pt / C catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 These are scanning electron microscope morphology images of the hydrothermal NiCo precursor 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 (c) in step (3).

[0025] Figure 2 X-ray diffraction patterns 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 target sample F-Ni2P / CoP obtained in Example 1 of the present invention is shown in transmission electron microscope morphology image (a), high-resolution electron microscope photograph image (b), selected area electron diffraction image (c), and energy dispersive X-ray spectrum image (d).

[0027] Figure 4X-ray photoelectron energy spectra of the phosphated sample Ni2P / CoP and the target catalyst F-Ni2P / CoP obtained in Example 1 of the present invention: (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 The diagram (a) shows a comparison of polarization curves of hydrogen evolution reaction of different phosphated samples Ni2P / CoP-1, Ni2P / CoP-2, and the phosphated sample Ni2P / CoP (Ni2P / CoP-1.5) obtained in step (2) of Example 1; the diagram (b) shows a comparison of polarization curves of hydrogen evolution reaction of different catalysts 0.5-F-Ni2P / CoP-1.5, 1-F-Ni2P / CoP-1.5 (target catalyst F-Ni2P / CoP obtained in step (3) of Example 1), and 2-F-Ni2P / CoP-1.5.

[0029] Figure 6 Comparison of 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); impedance spectrum test results of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at a potential of -0.03V (vs. reversible hydrogen electrode) (b); relationship between capacitance current density and potential scan rate of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at open circuit potential (c); comparison of polarization curves of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 after ECSA normalization (d).

[0030] Figure 7 Comparison of polarization curves of hydrogen evolution reaction of different samples 1-F-Ni2P / CoP-1.5, Ni2P / CoP-1.5 and Pt / C catalyst in 0.5MH2SO4 electrolyte (pH=0) (a); impedance spectrum test results of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at a potential of -0.03V (vs. reversible hydrogen electrode) (b); relationship between capacitance current density and potential scan rate of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at open circuit potential (c); comparison of polarization curves of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 after ECSA normalization (d).

[0031] Figure 8Comparison of 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 PBS electrolyte (pH=7) (a); impedance spectrum test results of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at a potential of -0.03V (vs. reversible hydrogen electrode) (b); relationship between capacitance current density and potential scan rate of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 at open circuit potential (c); comparison of polarization curves of 1-F-Ni2P / CoP-1.5 and Ni2P / CoP-1.5 after ECSA normalization (d).

[0032] Fig. 9 The target catalyst F-Ni2P / CoP in step (3) of Example 1 was heated in 1M KOH, 0.5M H2SO4 and 1M PBS at a current density of 100 mA cm -2 Stability test results (a); 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] Fig.10 These are scanning electron microscope morphology images of the target catalyst F-Ni2P / CoP in step (3) of Example 1 after 55 hours of durability testing in 1M KOH (a), 0.5M H2SO4 (b) and 1MPBS (c) environments. DETAILED DESCRIPTION

[0034] The specific implementation is described in detail below in conjunction with the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited by the specific implementation. The raw materials and reagents used in the examples are all commercially available unless otherwise specified. 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, the operating steps are as follows:

[0037] (1) With a thickness of 1.85 mm and a surface density of 610 ± 30 g / m 2 , nickel foam (NF) with a pore size of 0.20 to 0.80 mm. The nickel foam (1.5 × 4 cm 2) was ultrasonically cleaned with ethanol for 10 minutes, and then activated with 3M hydrochloric acid solution for 10 minutes. The activated nickel foam and 30mL of deionized water 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 water solution is 0.2M) were placed in a hydrothermal reactor with a volume of 50mL, and the hydrothermal reaction was carried out at 160℃ for 6h. After naturally cooling to room temperature, a double transition metal phosphide precursor was grown on the surface of the carrier. The aqueous solution containing Co and Ni transition metal salts remaining on the surface of the precursor was washed with deionized water and then vacuum dried at 60℃ for 6h to obtain a hydrothermal NiCo precursor; the scanning electron microscope image of the hydrothermal NiCo precursor is as shown in Figure 1 (a) shows the X-ray diffraction pattern. Figure 2 As shown in (a);

[0038] (2) 1.0 g of the hydrothermal NiCo precursor obtained in step (1) was placed in the middle of a quartz boat, and then 1.5 g of sodium hypophosphite (NaH2PO2) was placed upstream of the quartz boat. The mixture was heated to 350° C. at a rate of 2° C. per minute in an argon atmosphere for a phosphating reaction. The mixture was kept at a constant temperature for 2 h to in-situ generate a double transition metal phosphide heterojunction on the surface of the double transition metal phosphide precursor, and a relatively rough nanowire structure with a large active area was obtained to obtain a phosphated sample Ni2P / CoP. The scanning electron microscope image of the phosphated sample Ni2P / CoP is shown in FIG. Figure 1 (b) shows the X-ray diffraction pattern. Figure 2 (b) shows X-ray photoelectron spectroscopy Figure 4 (a);

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

[0040] Example 2

[0041] A method for preparing a fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst, the operating steps are as follows:

[0042] (1) With a thickness of 1.85 mm and a surface density of 610 ± 30 g / m 2 , nickel foam (NF) with a pore size of 0.20 to 0.80 mm was used as a carrier, and the nickel foam (1.5×4 cm 2 ) was ultrasonically cleaned with ethanol for 10 minutes, and then activated with a 3M hydrochloric acid solution for 10 minutes, the activated nickel foam and 20mL of a 3.6mmol / L hydrochloric acid solution containing Co(NO3)2·6H2O (0.05M, the concentration of transition metals in the hydrochloric acid solution) were placed in a hydrothermal reactor with a volume of 50mL, and the reaction was carried out at a constant temperature of 100°C for 20h, and then naturally cooled to room temperature to grow a double transition metal phosphide precursor on the surface of the carrier, and the aqueous solution containing transition metal salts remaining on the surface of the precursor was washed with deionized water and then vacuum dried at 60°C for 6h to obtain a hydrothermal NiCo precursor;

[0043] (2) 1.0 g of the hydrothermal NiCo precursor obtained in step (1) was placed in the middle of a quartz boat, and then 1 g of sodium hypophosphite (NaH2PO2) was placed upstream of the quartz boat. The mixture was heated to 400°C at a rate of 2°C per minute in an argon atmosphere for a phosphating reaction. The mixture was kept at this temperature for 1 h to in-situ generate a double transition metal phosphide heterojunction on the surface of the double transition metal phosphide precursor, and a relatively rough nanowire structure with a large active area was obtained to obtain a phosphated sample Ni2P / CoP.

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

[0045] Scanning electron microscopy observation ( Figure 1 In a), it was found that after hydrothermal reaction, a large number of nanowires grew on the surface of nickel foam and self-assembled into nanoarrays. According to XRD analysis ( Figure 2 In a), the diffraction peaks of the nanowire material correspond to Ni(OH)2 and Co(CO3) 0.5 OH·0.11H2O phase. The hydrothermal NiCo precursor was phosphated at 350℃ for 2 hours, and the sample morphology did not change significantly ( Figure 1 b); After fluorination treatment, a relatively rough nanowire structure is formed on the catalyst surface ( Figure 1 In c), it can be seen that the length of the heterojunction nanowires of the present invention is 5 to 20 μm.

[0046] XRD analysis ( Figure 2 Figure b) shows that after the hydrothermal NiCo precursor was phosphated at 350°C for 2 hours, the NiCo precursor was transformed into Ni2P crystal phase and CoP crystal phase; by immersing in sodium fluoride solution for fluorination treatment, the phosphated sample Ni2P / CoP was transformed into the target catalyst F-Ni2P / CoP, and the peak position of the target catalyst did not change, indicating that the doping of fluorine atoms has no obvious effect on the crystal structure of Ni2P / CoP.

[0047] Transmission electron microscopy observation ( Figure 3 a) further confirmed the nanowire structure of the target catalyst after carbonization treatment, with an average diameter of about 80 nm; according to high-resolution electron microscopy analysis ( Figure 3 b), Ni2P and CoP form a uniformly distributed nanowire array heterojunction, selected area electron diffraction analysis ( Figure 3 Energy dispersive X-ray spectroscopy ( Figure 3 The sample was analyzed in (d), and the results showed that the main elements such as nickel, cobalt and phosphorus in the target catalyst were distributed very evenly, indicating that there were a large number of heterostructure interfaces in the target catalyst F-Ni2P / CoP. At the same time, fluorine was also evenly distributed in the entire observation area, indicating that fluorine atoms had been successfully doped into the heterostructure.

[0048] According to 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 is detected in the phosphated sample Ni2P / CoP, indicating that fluorine has been successfully doped into the catalyst ( Figure 4 A and Figure 4 b); Figure 4 Figure c shows the Ni 2p of the target catalyst F-Ni2P / CoP. 3 / 2 The spectrum can be decomposed into Ni δ+ (δ is close to 0), NiO x The combination of the Ni 2 +. Similarly, Co 2p 3 / 2 The spectrum of Figure 4 d) can be fitted as Co δ+ 、CoO x and satellite peaks, which also confirms that Co 2+ The existence of P 2p spectrum ( Figure 4 e) belongs to P δ+ 2p 3 / 2 and 2p 1 / 2 , indicating the presence of P bonded to Ni or Co. Ni δ+ 、Co δ+ With P δ+The joint detection of confirmed the formation of Ni2P and CoP. At the same time, the O1s spectrum ( Figure 4 f), the O 1s spectrum shows two peaks, one at 533.1 eV, attributed to the PO bond; the other at 531.7 eV, indicating the presence of a MO bond (M = Ni, Co). These observations are consistent with the XRD and TEM results.

[0049] The electrocatalytic performance test of the fluorine-doped and heterojunction-synergistically 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 an alkaline environment, and saturated calomel as the reference electrode in an acidic and neutral environment. Example 1 Preparation The obtained fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst was used as the working electrode, Pt / C was used as the control, and the electrolytes were 1M KOH (pH=14), 0.5M H2SO4 (pH=0) and 1M PBS (pH=7) solutions, respectively. An electrochemical workstation was used to collect all electrochemical test data, and all electrochemical tests were performed at room temperature.

[0051] In order to compare the effects of different phosphating reaction conditions on the activity of the samples, three groups of control tests were set up according to the mass ratios of the hydrothermal NiCo precursor obtained in step (1) to the phosphorus source sodium hypophosphite of 1:1, 1:1.5 (phosphated sample Ni2P / CoP obtained in step (2) of Example 1, marked as Ni2P / CoP-1.5) and 1:2 (i.e., in step (2), 1.0 g of the hydrothermal NiCo precursor obtained in step (1) was placed in the middle of the quartz boat, and then 1 g and 2 g of sodium hypophosphite (NaH2PO2) were placed upstream of the quartz boat, respectively. The remaining operations were the same as steps (1) and (2) of Example 1, and phosphated samples Ni2P / CoP with mass ratios of the hydrothermal NiCo precursor obtained in step (1) to the phosphorus source sodium hypophosphite of 1:1 and 1:2 were obtained, respectively, marked as Ni2P / CoP-1 and Ni2P / CoP-2). The test results are as follows: Figure 5 Figure (a) shows that the phosphated sample Ni2P-CoP-1.5 has the best hydrogen evolution activity.

[0052] In addition, under the above-mentioned optimal phosphorus source mass ratio (i.e., the operating 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, marked as 1-F-Ni2P / CoP-1.5) and 2M on the activity of the target sample were also 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 2h to obtain different catalysts, marked as 0.5-F-Ni2P / CoP-1.5 and 2-F-Ni2P / CoP-1.5, respectively). The test results ( Figure 5 (b) shows that the target catalyst (1-F-Ni2P / CoP-1.5) has the best activity when the fluorine source concentration is 1M.

[0053] Hydrogen evolution reaction polarization curve test results ( Figure 6 , Figure 7 and Figure 8 ) showed that the target catalyst 1-F-Ni2P / CoP-1.5 has excellent electrocatalytic activity for hydrogen evolution reaction, and it only needs 44mV hydrogen evolution overpotential in 1.0M KOH to reach 10mA / cm 2 The current density ( Figure 5 In a), in an acidic environment, only 46 mV of hydrogen evolution overpotential is required to reach 10 mA / cm 2 The current density ( Figure 6 In a), a hydrogen evolution overpotential of 96 mV is required to reach 10 mA / cm in a neutral environment. 2 ( Figure 7 These results together indicate that the target catalyst has excellent catalytic activity and its activity is close to that of precious metal Pt / C catalyst. Figure 6 Middle b, Figure 7 Medium b and Figure 8 Figure b shows the impedance spectrum test results. Under all pH conditions, the charge transfer resistance of the target catalyst is lower than that of the phosphated sample Ni2P / CoP-1.5, indicating that the electron transfer speed inside 1-F-Ni2P / CoP-1.5 is faster, indicating that the target sample has good conductivity. Figure 6 Middle c, Figure 7 Medium c and Figure 8 Figure c shows the relationship between the capacitance current density and potential scan rate of the target catalyst 1-F-Ni2P / CoP-1.5 and the phosphated sample Ni2P / CoP-1.5 measured at the open circuit potential. Compared with the phosphated sample, the double-layer capacitance of the target sample has been improved to a certain extent, that is, the electrochemical specific surface area has been increased, which should be due to the unique heterogeneous structure of the 1-F-Ni2P / CoP-1.5 nanowires providing the most active sites; Figure 6 Middle d, Figure 7 Medium D and Figure 8 Figure d is the polarization curve normalized by electrochemical specific surface area, which shows that the target sample 1-F-Ni2P / CoP-1.5 has the highest intrinsic activity compared with the phosphated sample.

[0054] Fig. 9 a is the stability test of the target catalyst F-Ni2P / CoP obtained in step (3) of Example 1: a standard three-electrode system was used, with a carbon rod as the counter electrode, Hg / HgO as the reference electrode in an alkaline environment, and saturated calomel as the reference electrode in an acidic and neutral environment. A constant current of 100 mA was applied to the catalyst, and the stability of the catalyst was reflected by the change in potential. The results showed that after 55 hours of constant current measurement (100 mA / cm 2 ~55 hours, in alkaline, acidic and neutral electrolytes), the activity of the target catalyst did not show obvious decline, indicating that the target catalyst has good stability. Fig. 9 Figures b and c are the X-ray diffraction patterns and X-ray photoelectron spectra after stability testing. Except for 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, indicating that the target catalyst prepared in Example 1 of the present invention has strong phase stability.

[0055] Fig.10 The scanning electron microscope 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 shows that the morphological characteristics of the catalyst have not changed significantly, indicating that the target catalyst F-Ni2P / CoP has good structural stability.

[0056] For hydrogen evolution electrocatalysts operating in full pH environments, the three elements for evaluating their electrocatalytic standards are: intrinsic catalytic activity, conductivity, and stability. Traditional research on non-precious metal catalysts focuses on one or two of these aspects. The present invention provides measures to optimize these three aspects simultaneously, and provides a simple and inexpensive preparation method.

[0057] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst, characterized in that: The catalyst is composed of a fluorine-doped double transition metal phosphide heterojunction active phase and a carrier, wherein the fluorine-doped double transition metal phosphide heterojunction active phase is a relatively rough nanowire structure, and the nanowire is attached to the carrier; The double transition metal phosphides in the double transition metal phosphide heterojunction are Ni2P and CoP, and the two phases constitute the heterojunction; the active phase of the double transition metal phosphide heterojunction is a phosphide of a transition metal; the transition metal refers to at least two of Fe, Co, Ni, W, Cr, Mo, V, and Mn.

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

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

4. The method for preparing the fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst according to any one of claims 1 to 3, characterized in that: The following steps are included: (1) adding the carrier to a 0.05-0.5M aqueous solution of a transition metal salt, subjecting the carrier to a hydrothermal reaction at 90-180°C for 4-20 hours, and washing with water and drying; the transition metal salt refers to at least one of a transition metal halide, nitrate, sulfate, aminosulfonate, acetate, or an oxygen-containing or oxygen-free acid salt of a transition metal; the transition metal refers to at least two of Fe, Co, Ni, W, Cr, V, Mo, or Mn; (2) subjecting the precursor obtained after drying in step (1) to a phosphorus source in a mass ratio of 1:1 to 2 and subjecting the precursor to a phosphating reaction at 300 to 450° C. in an inert atmosphere to in situ generate a double transition metal phosphide heterojunction on the surface of the double transition metal phosphide precursor; (3) Immersing the double transition metal phosphide heterojunction obtained in step (2) in an aqueous solution of a 0.5-2 M fluorine source to perform a fluorine doping reaction, and after drying, obtaining a fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst.

5. The method for preparing the fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst according to claim 4, characterized in that: When the transition metal in step (1) is Co and Ni, the carrier is added to a 0.05-0.5M transition metal salt aqueous solution, and then urea and ammonium fluoride (NH4F) are added, wherein 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.

6. The method for preparing the fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst according to claim 4, characterized in that: The time of the hydrothermal reaction in step (1) is 6 hours; the concentration of the transition metal salt aqueous solution in step (1) is 0.2M.

7. The method for preparing the fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst according to claim 4, characterized in that: The phosphorus source in step (2) is sodium hypophosphite; the precursor obtained after drying in step (2) and the phosphorus source are in a mass ratio of 1:1.5; the inert atmosphere refers to argon atmosphere; the phosphating reaction time in step (2) is 1 to 3 hours, preferably 2 hours.

8. The method for preparing the fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst according to claim 4, characterized in that: 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.

9. Use of the fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst as described in any one of claims 1-3 and 5-8 in the field of electrocatalytic water decomposition of hydrogen.

10. The use according to claim 9, characterized in that: The fluorine-doped and heterojunction synergistically modified hydrogen evolution electrocatalyst is loaded on nickel foam or carbon paper and is used for electrolyzing water to produce hydrogen. The reaction time is not fixed, and hydrogen 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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