Membrane electrode material containing double-heteroatom co-doped iron-cobalt nanoparticles as well as preparation method and application of membrane electrode material

Abstract

The invention relates to a membrane electrode material containing double-heteroatom co-doped iron-cobalt nanoparticles and a preparation method and application thereof. The membrane electrode material comprises a conductive carbon material substrate; the double-heteroatom co-doped iron-cobalt alloy nanoparticles are loaded on the surface of the conductive carbon material substrate; the double heteroatoms are selected from two of nitrogen, sulfur, phosphorus and fluorine, and are combined with the FeCo alloy through chemical bonds to form a composite catalytic activity center. Iron trifluoromethanesulfonate (III) and cobalt trifluoromethanesulfonate (II) are prepared into an ethanol homogeneous solution as a precursor, a dispensing method is adopted, an infrared heating lamp is used for rapid drying, and the double-heteroatom co-doped iron-cobalt-based catalyst is prepared through a Joule heat rapid synthesis technology. Compared with the prior art, the sulfur and fluorine co-doped FeCo nano-particles are generated on the surface of the carbon paper in situ by adopting a Joule heat rapid synthesis technology, double breakthrough of activity and stability is realized through a synergistic effect of double heteroatom doping, and the sulfur and fluorine co-doped FeCo nano-particles show excellent stability in simulated alkaline seawater electrolyte.

Description

Technical Field

[0001] The present invention relates to the technical field of water electrolysis hydrogen production, and in particular to a membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles, and a preparation method and application thereof. Background Art

[0002] With the rapid development of hydrogen energy technology, water electrolysis technology has attracted widespread attention due to its clean and efficient characteristics. The hydrogen evolution reaction (HER) is the core reaction in the water electrolysis process, and its catalytic efficiency is highly dependent on the design of the electrocatalyst. At present, precious metal platinum-based catalysts are still regarded as the best HER catalysts, but their high cost and scarcity seriously restrict their large-scale application. In recent years, transition metal sulfides (such as CoS2, FeS2, etc.) have become a research hotspot for non-precious metal catalysts due to their low cost and adjustable electronic structure.

[0003] However, the intrinsic activity and conductivity of single metal sulfides are insufficient, resulting in a significant gap between their catalytic performance and that of precious metal catalysts.

[0004] In the prior art, patent CN116657184A discloses an iron-doped cobalt sulfide composite material, which regulates the electronic structure of CoS2 by introducing Fe elements. However, its catalytic activity is still not ideal when it is not compounded with secondary catalysts such as molybdenum sulfide, indicating that there is a bottleneck in the optimization of the electronic structure of a single metal sulfide system. In addition, the high-temperature sulfurization process used in this technology easily leads to agglomeration of active sites, making it difficult to fully expose the effective catalytic interface. Another patent, CN115084556A, proposes a bifunctional catalyst of nitrogen-doped carbon-supported iron-cobalt nanoparticles, which improves metal dispersion through carbon carriers, but it focuses on oxygen reduction / oxygen evolution reactions and does not involve the regulation of the electronic state of sulfide active sites, making it difficult to directly apply to HER scenarios.

[0005] Further studies have shown that simply using metal doping or carbon carrier loading still has the following problems: (1) The H adsorption energy on the sulfide surface is too high, resulting in slow reaction kinetics; (2) The balance between metal-sulfur bond strength and electron transfer efficiency is difficult to optimize; (3) Traditional sulfurization processes are prone to introduce structural defects, reducing material stability. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles, as well as its preparation method and application. The present invention adopts Joule heat rapid synthesis technology to in situ generate sulfur-fluorine co-doped FeCo nanoparticles on the surface of carbon paper. Through the synergistic effect of double heteroatom doping, a double breakthrough in activity and stability is achieved, and excellent stability is shown in simulated alkaline seawater electrolyte.

[0007] During the conception of the present invention, it was believed that the transition metal catalyst system based on nitrogen-doped carbon matrix support (such as Fe-NC and Co-NC) has shown excellent performance in the field of ORR and OER bifunctional catalysis due to its active site density advantage brought by its high specific surface area. Similarly, sulfur atoms as another dopant (its outermost layer contains p orbitals) have an electronegativity similar to that of carbon, which can effectively induce the polarization effect of adjacent carbon and nitrogen atoms. In this system, the transition metal not only forms a metal node bridging structure through organic ligands, but also plays a dual function: it acts as a Lewis acid for other metal species (such as cobalt oxides, etc.) to stabilize their high valence states, and it can also regulate the pore orientation of the carbon matrix, thereby significantly improving the catalytic performance. Through the dual doping strategy, carbon-based materials can achieve unique electron distribution regulation and integrate a higher density of active sites with the help of synergistic effects.

[0008] It can be seen that developing a double heteroatom co-doped catalyst and further constructing a membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles for seawater electrolysis is a very promising direction. How to develop a new catalyst that reconstructs the electronic structure of sulfide through a multi-element synergistic doping strategy and simultaneously achieves high active site exposure and stable carrier loading is the key to breaking through the existing technological bottleneck.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] A first aspect of the present invention provides a membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles, comprising:

[0011] a conductive carbon material substrate;

[0012] Double heteroatom co-doped iron-cobalt alloy nanoparticles supported on the surface of the conductive carbon material substrate;

[0013] The double heteroatoms are selected from two of nitrogen, sulfur, phosphorus and fluorine, and are combined with the FeCo alloy through chemical bonds to form a composite catalytic active center.

[0014] Furthermore, the double heteroatoms are sulfur and fluorine, wherein sulfur exists on the surface of the FeCo alloy nanoparticles in the form of FeS2 and fluorine exists in the form of FeF2.

[0015] Furthermore, the conductive carbon material substrate is carbon paper.

[0016] Furthermore, the FeCo alloy nanoparticles have a diameter of 150-240 nm and are uniformly dispersed on the surface of the carbon material substrate.

[0017] A second aspect of the present invention provides a method for preparing the membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles as described above, comprising the following steps:

[0018] S1: dissolving iron (III) trifluoromethanesulfonate and cobalt (II) trifluoromethanesulfonate in an organic solvent to form a homogeneous precursor solution;

[0019] S2: coating the precursor solution on the surface of the conductive carbon material substrate and performing a drying process;

[0020] S3: The substrate loaded with the precursor is subjected to Joule heat treatment under an inert atmosphere to co-dope iron, cobalt and heteroatoms to form FeCo alloy nanoparticles, thereby obtaining a membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles.

[0021] Furthermore, in S1, the molar ratio of the iron (III) trifluoromethanesulfonate to the cobalt (II) trifluoromethanesulfonate is 1:1.

[0022] Furthermore, in S1, the organic solvent is anhydrous ethanol;

[0023] The ratio of iron (III) trifluoromethanesulfonate, cobalt (II) trifluoromethanesulfonate and anhydrous ethanol is (0.2-0.3 g):(0.15-0.2 g):(40-60 mL), preferably 0.251 g:0.178 g:50 ml.

[0024] Furthermore, in S2, the drying treatment adopts one of infrared heating, hot air drying or vacuum drying, and the drying temperature is 50-100°C, preferably 65°C.

[0025] Furthermore, in S3, during the Joule heat treatment, the surface temperature of the carbon paper is 500-700°C, preferably 600°C.

[0026] The treatment time is 1-30 seconds, preferably 8-30, most preferably 10 seconds,

[0027] The processing atmosphere is argon or nitrogen.

[0028] The third aspect of the present invention provides an application of the membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles as described above, wherein the membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles is used as an oxygen evolution reaction anode in 0.1M KOH and 0.6M NaCl electrolyte at 100mA cm -2 At current density:

[0029] OER overpotential ≤ 400 mV, Tafel slope ≤ 75 mV dec -1 , at 100mA cm -2 Continuous stability under working conditions ≥100 hours.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This paper proposes a synergistic optimization strategy for sulfur and fluorine co-doping. Leveraging the advantages of a rapid synthesis method, the sulfur-fluorine co-doped FeCo-based catalyst, FeCo@CSF-J-10, was prepared using iron (III) trifluoromethanesulfonate and cobalt (II) trifluoromethanesulfonate as precursor solutions. The synergistic effect of dual heteroatom doping achieves a double breakthrough in both activity and stability. The FeCo@CSF-J-10 catalyst exhibits superior catalytic activity and stability. In alkaline seawater (0.1M KOH + 0.6M NaCl), an ultra-low overpotential of only 392mV is required to achieve a charge of 100mAcm -2 The current density can be 100mAcm -2 It can work stably for more than 100 hours at a current density of 1000 nm, providing new ideas for the development of highly corrosion-resistant seawater electrolysis catalysts and has very good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The figure is a flow chart of the preparation process of the catalyst in Example 1 and Comparative Examples 1 and 2 of the present invention.

[0033] Figure 2 The XRD patterns of the SEM images of FeCo@CS-J-10, FeCo@CF-J-10 and FeCo@CSF-J-10 catalysts in Examples of the present invention and Comparative Examples 1 and 2 are shown.

[0034] Figure 3 This is an elemental surface scan of the FeCo@CSF-J-10 catalyst in the examples of the present invention.

[0035] Figure 4 TEM image and elemental scanning image of FeCo@CSF-J-10 catalyst in the embodiment of the present invention.

[0036] Figure 5 The XRD patterns of FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 catalysts in Examples 1 and 2 of the present invention are shown.

[0037] Figure 6 The C1s, O 1s, S2p and F1s fine spectra of FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 catalysts in Examples of the present invention and Comparative Examples 1 and 2 are shown.

[0038] Figure 7 Fe 2p is the FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 catalysts in Examples 1 and 2 of the present invention. 3 / 2 and Co 2p 3 / 2 Fine spectrum.

[0039] Figure 8 Polarization curves and Tafel slopes of FeCo@CSF-J-10, FeCo@CS-J-10, and FeCo@CF-J-10 catalysts in 0.1 M KOH + 0.6 M NaCl electrolyte in Examples of the present invention and Comparative Examples 1 and 2.

[0040] Figure 9 Nyquist curves of FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 in Examples of the present invention and Comparative Examples 1 and 2.

[0041] Figure 10 The cyclic voltammetry curves of FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 at different scan rates and the corresponding current density difference-scan rate diagrams in Examples 1 and 2 of the present invention are shown.

[0042] Figure 11 This is a long-term stability test of the FeCo@CSF-J-10 catalyst in the embodiment of the present invention in 0.1M KOH+0.6M NaCl electrolyte.

[0043] Figure 12 Polarization curves and Tafel slopes of FeCo@CSF-J-10, FeCo@CS-J-10, and FeCo@CF-J-10 in 1 M KOH electrolyte in Examples of the present invention and Comparative Examples 1 and 2.

[0044] Figure 13 This is a long-term stability test of the FeCo@CSF-J-10 catalyst in 1M KOH electrolyte in an embodiment of the present invention.

[0045] Figure 14 1 is the SEM image of the FeCo@CSF-J-10 catalyst after stability test and the corresponding element distribution diagram in the embodiment of the present invention.

[0046] Figure 15 TEM image of the FeCo@CSF-J-10 catalyst after stability test and the corresponding element distribution map in the embodiment of the present invention.

[0047] Figure 16 This is the XRD pattern of the FeCo@CSF-J-10 catalyst after stability testing in the embodiment of the present invention.

[0048] Figure 17 This is the XPS spectrum of the FeCo@CSF-J-10 catalyst after stability test in the embodiment of the present invention. DETAILED DESCRIPTION

[0049] On the whole, the membrane electrode containing double heteroatom co-doped iron-cobalt nanoparticles and its preparation method in the present invention. It includes the following steps: using carbon paper as a substrate, using iron (III) trifluoromethanesulfonate and cobalt (II) trifluoromethanesulfonate to prepare an ethanol homogeneous solution as a precursor, using a drop coating method and rapid drying with an infrared heating lamp, and preparing a double heteroatom co-doped iron-cobalt-based catalyst by Joule heat rapid synthesis technology. The heteroatoms are taken from two of nitrogen, sulfur, phosphorus and fluorine. Compared with the prior art, the present invention achieves more excellent catalytic activity and stability through a double heteroatom co-doping synergistic optimization strategy. The catalyst exhibits excellent oxygen evolution reaction (OER) activity in alkaline seawater (0.1M KOH+0.6M NaCl), and only 392mV overpotential is required to reach 100mAcm -2 The current density can reach 10000 s and can operate stably at industrial current density for over 100 hours. Double heteroatom doping optimizes the electronic structure through Pd orbital hybridization and electronegativity regulation, significantly improving resistance to chloride ion corrosion and providing an innovative solution for achieving cheap and efficient hydrogen production by seawater electrolysis.

[0050] In a specific implementation, the heteroatom is sulfur or fluorine.

[0051] In the specific implementation, the carbon paper is SCP130N and the size is cut into 1×1.5cm. 2 .

[0052] In a specific implementation, the diameter of the FeCo alloy nanoparticles is 150-240 nm, and sulfur and fluorine exist on the surface of the particles in the form of FeS2 and FeF2 respectively.

[0053] In specific implementation, the best preparation process includes the following steps:

[0054] Step 1: 0.251 g of iron (III) trifluoromethanesulfonate (C3F9FeO9S3) and 0.178 g of cobalt (II) trifluoromethanesulfonate (C2CoF6O6S2) were dissolved in 50 mL of ethanol at room temperature and magnetically stirred for 10 min to form a homogeneous solution;

[0055] Step 2: Use the drop coating method to drop 500 μL of the precursor solution containing Fe and Co directly onto the 1×1.5 cm 2 The carbon paper was placed on a carbon paper substrate (SCP130N) and quickly dried with an infrared heating lamp (about 65°C). The heated and dried carbon paper was placed on two 3×6cm 2 A sandwich structure is constructed between the carbon paper (SCP130N) to ensure that the sample is heated evenly during the heating process;

[0056] Step 3: In an argon-protected glove box, a heating treatment was performed by applying high voltage and high current to generate Joule heat. The voltage was set to 30 V, the current was set to 22 A, and the heating time was 10 s to obtain a FeCo@CSF-J-10 sample.

[0057] In a specific implementation, during the Joule heat treatment, the surface temperature of the carbon paper is about 600°C;

[0058] In a specific implementation, the diameter of the FeCo alloy nanoparticles is 150-240 nm, and sulfur and fluorine exist on the surface of the particles in the form of FeS2 and FeF2 respectively.

[0059] During the application of the composite material in the electrolysis of seawater, a three-electrode system was used to perform all electrochemical performance tests. The prepared material was used as the working electrode, the carbon rod was used as the counter electrode, and Ag / AgCl (saturated KCl) was used as the reference electrode. The electrochemical performance of the composite material was tested using a three-electrode system. The working electrode was the carbon rod, the counter electrode was the Ag / AgCl (saturated KCl) electrode, and the electrochemical performance was tested using a three-electrode system. -1 The linear voltammetric sweep test was performed at a scan rate of 100 nm. The relevant tests were completed using a Metrohm Autolab workstation (Metrohm, MultiAutolan m204) from Switzerland.

[0060] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Any features such as preparation methods, materials, structures or composition ratios not explicitly described in this technical solution are considered to be common technical features disclosed in the prior art.

[0061] Example 1

[0062] See also Figure 1 The preparation of sulfur-fluorine co-doped iron-cobalt nanoparticle catalysts is as follows:

[0063] Step 1: 0.251 g of iron (III) trifluoromethanesulfonate (C3F9FeO9S3) and 0.178 g of cobalt (II) trifluoromethanesulfonate (C2CoF6O6S2) were dissolved in 50 mL of ethanol at room temperature and magnetically stirred for 10 min to form a homogeneous solution;

[0064] Step 2: Use the drop coating method to drop 500 μL of the precursor solution containing Fe and Co directly onto the 1×1.5 cm 2 The carbon paper was placed on a carbon paper substrate (SCP130N) and quickly dried with an infrared heating lamp (about 65°C). The heated and dried carbon paper was placed on two 3×6cm 2 A sandwich structure is constructed between the carbon paper (SCP130N) to ensure that the sample is heated evenly during the heating process;

[0065] Step 3: In an argon-protected glove box, a heating treatment is performed by applying high voltage and high current to generate Joule heat. The voltage is set to 30 V, the current is set to 22 A, and the heating time is 10 s to obtain a FeCo@CSF-J-10 sample. The surface temperature of the carbon paper is about 600 °C.

[0066] Comparative Example 1

[0067] The preparation of sulfur-doped iron-cobalt nanoparticle catalysts is carried out in the following steps:

[0068] Step 1: Dissolve 0.119 g of CoCl2·6H2O and 0.081 g of FeCl3 in 50 mL of deionized water at room temperature and stir magnetically for 10 min to form a homogeneous solution. Add 0.59 mL of DMSO to 50 mL of deionized water.

[0069] Step 2: 500 μL of the solution containing Fe and Co precursors and 200 μL of DMSO solution were dropped in batches on a 1×1.5 cm 2 The carbon paper substrate (SCP130N) was placed on the substrate and quickly dried using an infrared heating lamp.

[0070] In step 3, the dried sample was subjected to rapid Joule heating for 10 seconds (the surface temperature of the carbon paper was about 600° C.) to obtain a FeCo@CS-J-10 sample.

[0071] Comparative Example 2

[0072] Preparation of Fluorine-doped Iron-Cobalt Nanoparticle Catalysts

[0073] Step 1: Dissolve 0.119 g of CoCl2·6H2O and 0.081 g of FeCl3 in 50 mL of deionized water at room temperature and stir magnetically for 10 min to form a homogeneous solution.

[0074] Step 2: 500 μL of the solution containing Fe and Co precursors and 100 μL of Nafion solution were dropped onto a 1×1.5 cm 2 The carbon paper substrate (SCP130N) was placed on the substrate and quickly dried using an infrared heating lamp.

[0075] In step 3, the dried sample was subjected to rapid Joule heating for 10 seconds (the surface temperature of the carbon paper was about 600° C.) to obtain a FeCo@CS-J-10 sample.

[0076] Verification Example 1

[0077] Structural and morphological characterization of sulfur-fluorine co-doped iron-cobalt nanoparticle catalyst (FeCo@CSF-J-10).

[0078] The FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 prepared above were subjected to scanning electron microscopy (SEM) analysis. Figure 2 As shown. It can be seen that the metal nanoparticles on the catalyst substrate doped only with sulfur present a fine rod-like particle structure, with a relatively small particle size and a relatively uniform distribution, without obvious large-scale agglomerates. The catalyst doped only with fluorine presents a more unique microstructure, which is composed of a large number of fine structural units interwoven into nanoscale rod-like particles or fibrous structures, forming a morphology similar to a porous network. The FeCo@CSF-J-10 catalyst substrate is loaded with metal nanoparticles with a spherical structure and presents a uniformly dispersed state, without obvious large-scale agglomeration. The results show that S and F doping may effectively inhibit particle agglomeration, making the active components more evenly dispersed, which is conducive to increasing the exposure of active sites. At the same time, it can be found that the substrate in the FeCo@CSF-J-10 catalyst is smoother, indicating that the catalyst has better conductivity and can enhance its catalytic activity. Elemental surface scanning (EDX) such as Figure 3 It can be observed that iron, cobalt, sulfur, fluorine, and oxygen elements are evenly distributed on the surface of the entire carbon paper substrate, proving that these elements still exist and have good dispersion after rapid Joule heating.

[0079] The FeCo@CSF-J-10 prepared above was subjected to transmission electron microscopy (TEM) test. Figure 4 As shown in the figure, it can be observed that the metal nanoparticles are spherical with a diameter of 150 to 240 nm. Figure 4 ) results show that iron, cobalt, sulfur, fluorine and oxygen elements are evenly distributed in the nanoparticles, which is consistent with the element surface scanning results of SEM, confirming the successful preparation of sulfur and fluorine co-doped catalysts.

[0080] The FeCo@CSF-J-10 prepared above was subjected to X-ray diffraction analysis (XRD). Figure 5 As shown, the FeCo@CSF-J-10, FeCo@CS-J-10, and FeCo@CF-J-10 catalysts exhibit characteristic diffraction peaks corresponding to FeCo metal alloys at 44.750° and 65.108° (PDF#48-1816). The peak intensity of the FeCo@CSF-J-10 catalyst is the strongest. The FeCo@CSF-J-10 catalyst also clearly exhibits characteristic peaks of FeS2 (PDF#24-0074) and FeF2 (PDF#18-0638), indicating that the FeCo@CSF-J-10 catalyst has successfully doped sulfur and fluorine.

[0081] The FeCo@CSF-J-10 prepared above was subjected to X-ray photoelectron spectroscopy (XPS) analysis. Figure 6 As shown, in the FeCo@CSF-J-10 catalyst, it can be found by fitting that the S2p fine spectrum is located at 162.0 eV (2p 3 / 2 ) and 163.6eV(2p 1 / 2 The characteristic peak at 167.8 eV is attributed to metal-sulfur bonds (MS). The SO characteristic peak at 167.8 eV indicates that sulfur on the material surface was oxidized during the preparation process. The characteristic peak at 684.5 eV in the F1s fine spectrum is attributed to metal-fluorine bonds (MF), indicating the presence of fluorine on the catalyst surface. These results demonstrate the successful doping of sulfur and fluorine. Figure 7 Fe2p as catalyst 3 / 2 According to the peak area analysis, Fe 2+ and Fe 3+ The ratio of FeCo@CSF-J-10 is 75:25. 2+ and Fe 3+ The ratio of sulfur to Fe is 61:39, which indicates that the electron-donating effect of sulfur and the electron-withdrawing effect of fluorine, which has the strongest electronegativity, partially offset each other, but it can still attract electrons from Fe and make it exist in a higher valence state. 3 / 2 The fine spectrum ( Figure 7 ) It can be seen that according to the peak area analysis, similar results can be obtained as for Fe. In the FeCo@CS-J-10 catalyst, Co 3+ and Co 2+ The ratio of Co in FeCo@CSF-J-10 catalyst is 57:43. 3+ and Co 2+ The ratio is 68:32, which shows that the electron-donating effect of the introduced sulfur element and the electron-withdrawing effect of the fluorine element form a partial compensation mechanism, but can still trigger the electron migration of cobalt atoms through induction, making it stable in a higher oxidation state.

[0082] Verification Example 2

[0083] Simulated alkaline seawater electrolysis experiments using sulfur-fluorine co-doped iron-cobalt nanoparticle catalyst (FeCo@CSF-J-10)

[0084] The FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 catalysts prepared above were used as anode electrode materials for hydrogen production by electrolysis of water, and their electrochemical performance was tested and evaluated.

[0085] All electrochemical performance tests were performed using a three-electrode system, with the prepared material as the working electrode, the carbon rod as the counter electrode, and Ag / AgCl (saturated KCl) as the reference electrode. -1 Linear voltammetric sweep tests were performed at a scan rate of 100 nm. The relevant tests were completed using a Metrohm Autolab workstation (Metrohm, Multi Autolan m204) from Switzerland.

[0086] The oxygen evolution reaction performance of FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 catalysts prepared above in 0.1M KOH+0.6M NaCl solution was compared. Figure 8 It can be clearly seen that the FeCo@CSF-J-10 catalyst prepared by sulfur and fluorine co-doping exhibits the best OER performance, and only an overpotential of 392mV is required to reach 100mAcm in 0.1M KOH+0.6MNaCl electrolyte. -2 The current density is much lower than that of FeCo@CS-J-10 (458mV) and FeCo@CF-J-10 (411mV) doped with sulfur or fluorine, which shows that the synergistic effect of sulfur and fluorine doping has a significant effect on the improvement of catalyst performance. In addition to the overpotential, the OER kinetics of the catalyst is further evaluated by converting the polarization curve into the Tafel slope. Figure 8 As shown in Figure 2, the Tafel slope of the sulfur and fluorine co-doped FeCo@CSF-J-10 catalyst is 70.8 mVdec. -1 , which is higher than that of FeCo@CS-J-10 doped with sulfur or fluorine (91.6mV dec -1 ) and FeCo@CF-J-10(78.0mV dec -1 ) catalyst has a smaller slope, which indicates that the catalyst co-doped with sulfur and fluorine has a better OER kinetic response.

[0087] The FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 catalysts prepared above were subjected to EIS tests at an overpotential of 315 mV. Figure 9 As shown in the figure, under the test conditions where the solution internal resistance is approximately equal, the FeCo@CSF-J-10 catalyst exhibits the smallest semicircle diameter of 4Ω, which is much smaller than that of FeCo@CS-J-10 (8Ω) and FeCo@CF-J-10 (7Ω) catalysts, indicating that the FeCo@CSF-J-10 catalyst has the lowest charge transfer impedance, which is one of the important factors for its excellent OER catalytic activity.

[0088] The electrochemical active areas of the FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 catalysts prepared above were measured by cyclic voltammetry at different scan rates. Figure 10 As shown, the scanning rates (20-100 mV s -1 ) in the non-Faraday region, the linear relationship between the current response and the scan rate at a constant potential is selected, and its slope corresponds to C dl , in order to quantitatively evaluate the active area. FeCo@CSF-J-10 exhibits the largest C dl The value is 5.24mF·cm -2 Compared with FeCo@CS-J-10 (3.61mF·cm -2 ) and FeCo@CSF-J-10(3.21mF·cm -2 ) increased by 45.1% and 63.2%, respectively, and this difference directly confirmed that the FeCo@CSF-J-10 catalyst has more abundant active site exposure.

[0089] Verification Example 3

[0090] Long-term stability evaluation of FeCo@CSF-J-10 catalyst in electrolyte

[0091] The FeCo@CSF-J-10 catalyst prepared above was tested for stability in 0.1M KOH+0.6M NaCl electrolyte using chronoamperometry. Figure 11 As can be seen in the figure, FeCo@CSF-J-10 catalyst has a -2 It can operate stably for more than 100 hours at the current density without obvious performance degradation, indicating its excellent stability.

[0092] The electrochemical performance of the FeCo@CSF-J-10, FeCo@CS-J-10 and FeCo@CF-J-10 catalysts prepared above was then tested in alkaline electrolyte (1 M KOH). Figure 12 The polarization curve of the catalyst in 1M KOH electrolyte is consistent with the expectation. It can be clearly seen that the FeCo@CSF-J-10 catalyst has a high conductivity at 100mAcm -2 The overpotential required for the FeCo@CF-J-10 catalyst is only 304 mV, which is lower than that of FeCo@CF-J-10 (318 mV) and FeCo@CS-J-10 (424 mV). When the overpotential is 328 mV, the current density of the FeCo@CSF-J-10 catalyst is 311 mA cm -2 , respectively FeCo@CF-J-10(133mA cm -2) and FeCo@CS-J-10 (9.5 mA cm -2 ) by 2.3 and 33 times. The Tafel slope of FeCo@CSF-J-10 catalyst is 38.4 mV dec -1 , which is much smaller than FeCo@CF-J-10 (51.0mV dec -1 ) and FeCo@CS-J-10(95.3mV dec -1 ), which fully demonstrates that the sulfur and fluorine co-doped FeCo@CSF-J-10 catalyst has more excellent OER performance.

[0093] The stability of the FeCo@CSF-J-10 catalyst prepared above was tested by chronoamperometry in 1M KOH electrolyte. Figure 13 It shows that FeCo@CSF-J-10 catalyst has a -2 The catalytic activity remained stable after 100 hours of continuous operation under constant current density conditions, indicating that it has good electrochemical stability.

[0094] The catalyst samples that have undergone stability testing were systematically characterized, and SEM images showed that ( Figure 14 ), the morphology of the FeCo@CSF-J-10 catalyst is still similar to that before the reaction, with many spherical nanoparticles evenly dispersed on the surface of the carbon paper substrate, and no agglomeration occurs. Further TEM characterization can be observed ( Figure 14 ), the catalyst morphology did not change much before and after the reaction, the FeCo metal particles were still evenly dispersed and there was no structural damage.

[0095] The XRD test of FeCo@CSF-J-10 catalyst after reaction was carried out. Figure 15 The FeCo@CSF-J-10 catalyst still retains the characteristic diffraction peaks of the FeCo alloy, but the characteristic diffraction peaks of FeS2 and FeF2 almost disappear. This is because the catalyst surface may become amorphous under continuous oxidation conditions during long-term stability testing. These results demonstrate that the FeCo@CSF-J-10 catalyst has excellent structural stability.

[0096] XPS test of FeCo@CSF-J-10 catalyst after reaction was performed. Figure 16 This shows that the iron, cobalt, sulfur and fluorine elements in the FeCo@CSF-J-10 catalyst can still exist well after a long period of stability testing. Figure 17 It shows that Co 2p 3 / 2 and Fe 2p 3 / 2 Co in fine spectroscopy 3+ and Fe3+ The increase in the ratio indicates that the Fe and Co elements on the surface of the material are oxidized. This is because the OER process is highly oxidizing, which causes the metal valence to increase accordingly.

[0097] Example 2

[0098] The specific steps are as follows:

[0099] Step 1: dissolve 0.200 g of iron (III) trifluoromethanesulfonate and 0.150 g of cobalt (II) trifluoromethanesulfonate in 40 mL of ethanol at room temperature and stir magnetically for 15 minutes to form a homogeneous solution;

[0100] Step 2: Use a micro syringe to drop a total of 500 μL of the precursor solution into a 1×1.5 cm 2 Carbon paper substrate (SCP130N), after each drop, immediately use infrared heating lamp (50℃) to dry the interlayer, and the total drying time is controlled within 3 minutes;

[0101] In step 3, the carbon paper surface temperature was stabilized at 500°C in a nitrogen atmosphere by controlling the output power of a Joule heating device (voltage 25V, current 18A) for 30 seconds to obtain a sample. Scanning electron microscopy (SEM) revealed that the obtained FeCo alloy nanoparticles had an average diameter of 152±8nm, and XPS confirmed the presence of sulfur and fluorine as FeS2 and FeF2.

[0102] Example 3

[0103] The specific steps are as follows:

[0104] Step 1: 0.300 g of iron (III) trifluoromethanesulfonate and 0.200 g of cobalt (II) trifluoromethanesulfonate were dissolved in 60 mL of anhydrous ethanol precooled to 4° C. under argon protection, and ultrasonically dispersed for 20 min to form a supersaturated precursor solution;

[0105] Step 2: Use pneumatic spraying to evenly coat the precursor solution on a 2×2 cm 2 The carbon paper substrate was immediately placed in a hot air drying oven at 100°C for rapid solvent removal, with the drying time compressed to less than 90 seconds;

[0106] In step 3, in a high-pressure argon atmosphere (0.5 MPa), an ultra-high voltage of 35 V and a pulsed current of 25 A were applied to the carbon paper, raising the surface temperature to 700°C. This heat treatment was continued for 7 seconds to obtain a sample. TEM analysis revealed a monodisperse spherical structure of the nanoparticles, and XPS confirmed the presence of sulfur and fluorine as FeS2 and FeF2.

[0107] Comparative Example 3

[0108] This comparative example is a single sulfur doping comparison group.

[0109] Different from Example 1, this comparative example uses ferrous sulfate (FeSO4·7H2O) and cobalt sulfate (CoSO4·7H2O) as precursors, which are dissolved in deionized water in equal molar amounts. After the same drop coating and infrared drying process, Joule heat treatment (600°C / 10 seconds) is performed. The resulting FeCo@CS-J-10S catalyst is only sulfur-doped. XPS shows that sulfur exists in the form of SO42- and no Fe-S bond is formed. In 0.1M KOH+0.6M NaCl electrolyte, 100mA cm -2 The corresponding overpotential increased to 438mV and the Tafel slope increased to 89.5mV dec. -1 , and the current decayed by 15% after 40 hours in the stability test, proving that the selection of sulfur source and chemical bonding mode are crucial to the formation of active sites.

[0110] Comparative Example 4

[0111] This comparative example is a sulfur-nitrogen co-doped comparison group.

[0112] Different from Example 1, this comparative example uses iron (III) trifluoromethanesulfonate, cobalt (II) trifluoromethanesulfonate and urea as precursors, adds 10wt% urea to the ethanol solution, and then performs Joule heat treatment (600℃ / 10s) after drop coating and drying. The obtained FeCo@CSN-J-10 catalyst is doped with sulfur and nitrogen, but XRD shows that FeN is generated. x S y Electrochemical tests showed that 100mA cm -2 Overpotential is 418mV, Tafel slope is 82.3mV dec -1 The amount of Fe dissolved after 80 hours due to Cl- corrosion reached 12.7 μg / cm 2 , revealing that the sulfur-fluorine combination is superior to the sulfur-nitrogen system in terms of corrosion resistance.

[0113] Comparative Example 5

[0114] Different from Example 1, this comparative example uses ferric chloride (FeCl3) and cobalt nitrate (Co(NO3)2·6H2O) as precursors, which are dissolved in ethanol and then 0.5 mL of trifluoromethanesulfonic acid is added as a fluorine source. After the same process, XPS detected that the fluorine was physically adsorbed and no Fe-F bond was formed. The resulting FeCo@CF*-J-10 catalyst was 100 mA cm -2 The lower overpotential reaches 427mV, and the Tafel slope increases to 84.6mV dec -1 , proving that the in situ coordination of trifluoromethanesulfonate anions in the precursor is irreplaceable for fluorine atom chemical doping.

[0115] Comparative Example 6

[0116] Different from Example 1, this comparative example used the same precursor solution to coat carbon paper and then calcined it in a tube furnace under argon at 600°C for 2 hours (heating rate 5°C / min). The resulting FeCo@CSF-T-120 catalyst nanoparticles were uneven in size (180-350 nm), and SEM showed severe agglomeration. Electrochemical tests showed that the 100mA cm -2 The overpotential is 412mV, but the Tafel slope is as high as 93.2mV dec -1 , and ECSA (3.02mF / cm 2 ) is only 57.6% of that of the Joule heating method, confirming the key role of rapid heating and cooling in nanostructure regulation.

[0117] Comparative Example 7

[0118] Different from Example 1, this comparative example first prepared pure FeCo alloy nanoparticles by Joule heat treatment, and then doped by gas phase fluorination (NH4F as fluorine source) and liquid phase sulfur impregnation (Na2S treatment). The obtained FeCo@F / SJ-10 catalyst XRD showed that FeF3 and CoS x In simulated seawater, 100mA cm -2 The overpotential is 408mV, but the Tafel slope (79.5mV dec -1 ) is significantly higher than that in Example 1, and in the stability test, the sulfur element is lost by 38% after 50 hours, which proves the necessity of synchronous doping to form a stable FeS2-FeF2 composite active center.

[0119] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles, characterized in that: include: a conductive carbon material substrate; Double heteroatom co-doped iron-cobalt alloy nanoparticles supported on the surface of the conductive carbon material substrate; The double heteroatoms are selected from two of nitrogen, sulfur, phosphorus and fluorine, and are combined with the FeCo alloy through chemical bonds to form a composite catalytic active center.

2. The membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles according to claim 1, characterized in that: The double heteroatoms are sulfur and fluorine, wherein sulfur exists on the surface of the FeCo alloy nanoparticles in the form of FeS2 and fluorine exists in the form of FeF2.

3. The membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles according to claim 1, characterized in that: The conductive carbon material substrate is carbon paper.

4. The membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles according to claim 1, characterized in that: The FeCo alloy nanoparticles have a diameter of 150-240 nm and are uniformly dispersed on the surface of the carbon material substrate.

5. A method for preparing a membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: dissolving iron (III) trifluoromethanesulfonate and cobalt (II) trifluoromethanesulfonate in an organic solvent to form a homogeneous precursor solution; S2: coating the precursor solution on the surface of the conductive carbon material substrate and performing a drying process; S3: The substrate loaded with the precursor is subjected to Joule heat treatment under an inert atmosphere to co-dope iron, cobalt and heteroatoms to form FeCo alloy nanoparticles, thereby obtaining a membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles.

6. The membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles according to claim 5, characterized in that: In S1, the molar ratio of the iron (III) trifluoromethanesulfonate to the cobalt (II) trifluoromethanesulfonate is 1:

1.

7. The membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles according to claim 5, characterized in that: In S1, the organic solvent is anhydrous ethanol; The ratio of the iron (III) trifluoromethanesulfonate, cobalt (II) trifluoromethanesulfonate and anhydrous ethanol is (0.2-0.3 g): (0.15-0.2 g): (40-60 mL).

8. The membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles according to claim 5, characterized in that: In S2, the drying process adopts one of infrared heating, hot air drying or vacuum drying, and the drying temperature is 50-100°C.

9. The membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles according to claim 5, characterized in that: In S3, during the Joule heat treatment, the surface temperature of the carbon paper is 500-700°C. Processing time is 1-30 seconds, The processing atmosphere is argon or nitrogen.

10. Use of a membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles according to any one of claims 1 to 4, characterized in that: The membrane electrode material containing double heteroatom co-doped iron-cobalt nanoparticles was used as an oxygen evolution reaction anode in 0.1 M KOH and 0.6 M NaCl electrolyte at 100 mA cm -2 At current density: OER overpotential ≤ 400 mV, Tafel slope ≤ 75 mV dec -1 , at 100mA cm -2 Continuous stability under working conditions ≥100 hours.

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