A nickel phosphide-iron phosphide self-supporting electrode and a preparation method and application thereof

Abstract

This application belongs to the field of electrocatalysis and photoelectrocatalysis materials technology, specifically relating to a nickel phosphide-iron phosphide self-supporting electrode, its preparation method, and its application. This application provides a method for preparing a nickel phosphide-iron phosphide self-supporting electrode, which directly constructs an active layer on a conductive nickel foam substrate through in-situ hydrothermal growth combined with a gas-phase phosphating strategy. The nickel foam not only acts as a conductive current collector but also participates in the growth of the precursor as a reaction substrate, enhancing the bonding force between the active layer and the substrate, completely avoiding the use of binders, and effectively reducing interfacial resistance. The phosphating treatment transforms the nickel-iron precursor into a phosphide with metal-like properties, significantly improving the electrode's conductivity and intrinsic catalytic activity, thereby solving the problem of slow reaction kinetics.

Description

Technical Field

[0001] This application belongs to the field of electrocatalysis and photoelectrocatalysis materials technology, specifically relating to a nickel phosphide-iron phosphide self-supporting electrode, its preparation method and application. Background Technology

[0002] Adipic acid plays a crucial role in the chemical industry as a key monomer in the production of nylon-66, plasticizers, and food additives. Traditional industrial production methods primarily employ the oxidation of cyclohexanol or cyclohexanone with nitric acid. While these processes are mature, they require highly corrosive concentrated nitric acid and result in significant emissions of the greenhouse gas N2O. This not only places stringent demands on equipment materials but also leads to severe environmental pollution problems. With the rise of green chemistry principles, developing new, milder, and more environmentally friendly adipic acid synthesis processes has become a research hotspot in this field.

[0003] Electrocatalytic oxidation technology utilizes electrons as a clean reagent to drive chemical reactions, offering advantages such as mild reaction conditions, controllable processes, and zero pollution emissions, and is considered a potential alternative to traditional thermocatalytic processes. However, the efficient electrocatalytic oxidation of cyclohexanol to adipic acid still faces many challenges. This reaction involves multiple electron transfer processes, has relatively slow kinetics, and often requires the application of high overpotentials. Furthermore, existing electrocatalytic systems mostly use powdered catalysts, which need to be coated onto the current collector surface using insulating polymer binders (such as Nafion solutions). The introduction of binders not only increases interfacial resistance but also easily covers active sites, hindering mass transfer between reactants and products. Moreover, the catalyst is prone to detachment during long-term electrolysis, leading to decreased electrode stability.

[0004] In recent years, the photoelectric synergistic strategy of introducing light energy into electrocatalytic systems has demonstrated unique advantages. The electron-hole pairs generated by photoexcitation can modulate the electronic structure of the catalyst surface, potentially further reducing the reaction energy barrier. Transition metal phosphides have attracted considerable attention in the field of electrocatalysis due to their unique metal-like properties, excellent conductivity, and intrinsic catalytic activity. However, how to construct a self-supporting transition metal phosphide electrode that is simple to fabricate, structurally robust, and can effectively couple light energy, and apply it to the efficient and green synthesis of adipic acid, remains a pressing technical challenge in this field. Summary of the Invention

[0005] Based on this, one embodiment of this application provides a nickel phosphide-iron phosphide self-supporting electrode, its preparation method, and its application.

[0006] This application provides a method for preparing a nickel phosphide-iron phosphide self-supporting electrode, comprising the following steps: Step 1: Cleaning and pre-treatment of the nickel foam; Step 2: The pretreated nickel foam is placed in a mixed solution containing nickel source and iron source for hydrothermal reaction to grow nickel-iron precursor on the surface of nickel foam, thus obtaining nickel foam with supported precursor. Step 3: The nickel foam of the load precursor is phosphated in the presence of a phosphorus source and under an inert atmosphere to obtain the nickel phosphide-iron phosphide self-supporting electrode.

[0007] In some embodiments, the molar ratio of the nickel source to the iron source is (1~4):1.

[0008] In some embodiments, the mixed solution also contains urea at a concentration of 0.05M to 0.2M.

[0009] In some embodiments, the mixed solution also contains ammonium fluoride at a concentration of 0.01 M to 0.05 M.

[0010] In some embodiments, the hydrothermal reaction is carried out at a temperature of 100°C-140°C for 12-24 hours.

[0011] In some embodiments, the phosphorus source is sodium hypophosphite, and the mass ratio of the phosphorus source to the nickel foam of the supported precursor is greater than or equal to 5:1.

[0012] In some embodiments, the phosphating treatment is performed at a temperature of 300°C-400°C for 2 hours.

[0013] This application also provides a nickel phosphide-iron phosphide self-supporting electrode prepared according to the preparation method described above.

[0014] This application also provides the application of the described nickel phosphide-iron phosphide self-supporting electrode in the electrocatalytic oxidation of cyclohexanol to prepare adipic acid.

[0015] In some embodiments, light is introduced during the electrocatalytic oxidation process to perform photo-assisted electrocatalytic oxidation.

[0016] This application provides a method for preparing a nickel phosphide-iron phosphide self-supporting electrode. An active layer is directly constructed on a conductive nickel foam substrate through in-situ hydrothermal growth combined with a gas-phase phosphating strategy. The nickel foam not only acts as a conductive current collector but also participates in the growth of the precursor as a reaction substrate, enhancing the adhesion between the active layer and the substrate. This completely avoids the use of binders and effectively reduces interfacial resistance. The phosphating treatment transforms the nickel-iron precursor into a phosphide with metal-like properties, significantly improving the electrode's conductivity and intrinsic catalytic activity, thereby solving the problem of slow reaction kinetics. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 SEM image of the nickel phosphide-iron phosphide self-supporting electrode supported on nickel foam prepared in Example 1.

[0019] Figure 2 The X-ray diffraction (XRD) pattern of the nickel phosphide-iron phosphide self-supporting electrode loaded with nickel foam prepared in Example 1.

[0020] Figure 3 The image shows a comparison of the linear sweep voltammetry (LSV) curves of the electrode prepared in Example 1 under conditions of presence and absence of cyclohexanol and under light irradiation.

[0021] Figure 4 This is a comparison chart showing the yield of the electrode prepared in Example 1 for the electrocatalytic oxidation of cyclohexanol to adipic acid under light and no light conditions. Detailed Implementation

[0022] The present application will be further described in detail below with reference to the embodiments and examples. It should be understood that these embodiments and examples are for illustrative purposes only and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to enable a more thorough and comprehensive understanding of the disclosure of the present application. It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0023] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings: The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND," and also undoubtedly includes technical solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0025] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0026] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0027] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0028] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0029] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0030] In this application, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions composed of the listed features.

[0031] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0032] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0033] In this application, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass-volume percentage.

[0034] All references to documents mentioned in this application are incorporated herein by reference as if each document were individually incorporated herein by reference. Unless they conflict with the inventive purpose and / or technical solution of this application, all cited documents are incorporated herein by reference in their entirety and for all purposes. When citing documents in this application, the definitions of relevant technical features, terms, nouns, phrases, etc., are also incorporated herein by reference. When citing documents in this application, examples and preferred embodiments of the cited technical features may also be incorporated herein by reference, but only to the extent that they enable the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, this application shall prevail or modifications shall be made adaptably to the description in this application.

[0035] To address the problems of high overpotential, high interfacial resistance, and poor stability caused by the need for binders to fix powdered catalysts in the electrocatalytic oxidation of cyclohexanol to prepare adipic acid in the prior art, this application provides a method for preparing and applying a nickel phosphide-iron phosphide self-supporting electrode.

[0036] The first aspect of this application provides a method for preparing a nickel phosphide-iron phosphide self-supporting electrode, comprising the following steps: cleaning and pre-treating nickel foam; placing the pre-treated nickel foam in a mixed solution containing a nickel source and an iron source for hydrothermal reaction to grow a nickel-iron precursor on the surface of the nickel foam, thereby obtaining nickel foam with a supported precursor; and phosphating the nickel foam with the supported precursor in the presence of a phosphorus source and under an inert atmosphere to obtain the nickel phosphide-iron phosphide self-supporting electrode.

[0037] This method directly constructs an active layer on a conductive nickel foam substrate through in-situ hydrothermal growth combined with a gas-phase phosphating strategy. The nickel foam not only acts as a conductive current collector but also participates in the growth of the precursor as a reaction substrate, enhancing the adhesion between the active layer and the substrate. This completely eliminates the need for binders and effectively reduces interfacial resistance. The phosphating treatment transforms the nickel-iron precursor into a phosphide with metal-like properties, significantly improving the electrode's conductivity and intrinsic catalytic activity, thereby solving the problem of slow reaction kinetics.

[0038] In some embodiments, the molar ratio of the nickel source to the iron source is (1~4):1. By adjusting the nickel-iron ratio, the electronic structure of the bimetallic active center can be optimized, generating a synergistic effect and further improving the catalytic activity for the oxidation of cyclohexanol.

[0039] In some embodiments, the mixed solution also contains urea at a concentration of 0.05–0.2 M. The urea slowly hydrolyzes at high temperature to produce OH-. - It can uniformly precipitate metal ions, which helps to form a nanosheet precursor structure with uniform morphology and high specific surface area.

[0040] In some embodiments, the mixed solution further contains ammonium fluoride at a concentration of 0.01–0.05 M. The introduction of ammonium fluoride can etch the nickel foam substrate, increase surface roughness, and provide more nucleation sites, while F… - The coordination effect helps to regulate the micromorphology of the precursor.

[0041] In some embodiments, the hydrothermal reaction is carried out at a temperature of 100–140°C for a reaction time of 12–24 hours. This temperature and time range is conducive to the full growth and crystallization of nickel-iron layered bimetallic hydroxides.

[0042] In some embodiments, the phosphorus source is sodium hypophosphite, and the mass ratio of the phosphorus source to the nickel foam supporting the precursor is greater than or equal to 5:1. Sufficient phosphorus source ensures the complete phosphating reaction, allowing the precursor to be fully converted into phosphide.

[0043] In some embodiments, the phosphating treatment is carried out at a temperature of 300–400°C for 1–3 hours. Within this temperature range, the PH3 gas generated by the decomposition of sodium hypophosphite can fully react with the metal precursor to generate a well-crystallized nickel phosphide-iron phosphide composite, while avoiding the collapse of the nanostructure caused by high temperature.

[0044] A second aspect of this application provides a nickel phosphide-iron phosphide self-supporting electrode prepared according to the above-described method. This electrode has a three-dimensional porous network structure, with the active material uniformly grown in the form of nanosheets on a nickel foam framework, exhibiting a large electrochemical active surface area and excellent electron transport capabilities.

[0045] A third aspect of this application provides the application of the aforementioned nickel phosphide-iron phosphide self-supporting electrode in the electrocatalytic oxidation of cyclohexanol to adipic acid. This application requires no additional binder, and the electrode can be used directly as the working electrode, exhibiting excellent electrocatalytic oxidation performance in alkaline electrolytes.

[0046] In some embodiments, light is introduced during the electrocatalytic oxidation process to perform photo-assisted electrocatalytic oxidation. The photogenerated carriers generated by light excitation can synergistically enhance the electrocatalytic process, further reducing the reaction overpotential and increasing the Faraday yield of adipic acid.

[0047] The embodiments of this application will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0048] In the specific embodiments described below, the measurement parameters involving raw material components may have slight deviations within the weighing accuracy range unless otherwise specified. For temperature and time parameters, acceptable deviations due to instrument testing accuracy or operational precision are permissible.

[0049] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0050] Example 1 (1) Pretreatment of nickel foam: Take a piece of nickel foam with a diameter of 2cm×4cm, and place it in acetone, 3M HCl solution and deionized water for ultrasonic cleaning for 15 minutes each, and then dry it in an oven at 60℃.

[0051] (2) Hydrothermal growth of nickel-iron precursor: 1.2 g Ni(NO3)2·6H2O, 0.8 g Fe(NO3)3·9H2O, 0.6 g urea and 0.15 g NH4F were dissolved in 35 mL deionized water and magnetically stirred for 30 minutes to form a homogeneous solution. The solution and the pretreated nickel foam were transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor and reacted at 100~140℃ for 12~24 hours. After the reaction was completed, the sample was taken out, washed several times with deionized water and ethanol, and vacuum dried overnight at 60℃ to obtain nickel foam loaded with nickel-iron precursor.

[0052] (3) Low-temperature phosphating treatment: The NF / Pre sample obtained in step (2) was placed downstream of the isothermal zone of a tube furnace, and 1.0 g of NaH2PO2 was placed upstream. Under the protection of N2 gas flow (100 sccm), the temperature was increased to 350℃ at a rate of 2℃ / min and held for 2 hours for phosphating. After the reaction was completed, it was naturally cooled to room temperature under N2 atmosphere to obtain the final product—nickel phosphide-iron phosphide self-supporting electrode supported by nickel foam (denoted as NF / Ni-P / Fe-P). Its SEM morphology is as follows. Figure 1 As shown, the morphology of the nanosheets was preserved after phosphating, but the surface became rougher and more porous. XRD analysis was performed on the product.

[0053] The results are as follows Figure 2 As shown, characteristic diffraction peaks matching those of the standard Ni2P card (PDF#97-060-1077) appeared at positions such as 40.7°, 44.6°, and 47.3°, confirming the successful synthesis of the Ni2P phase.

[0054] (4) Electrochemical performance test: A standard three-electrode system was used, with the NF / Ni-P / Fe-P electrode as the working electrode (for direct use, with an active area of ​​1 cm²). 2 The Hg / HgO electrode was used as the reference electrode, the carbon rod as the counter electrode, and the electrolyte was 1M KOH. First, the OER performance of the electrode in pure 1M KOH was tested (without light). Then, 0.1M cyclohexanol was added to the electrolyte, and its catalytic oxidation performance was tested. Finally, under the same conditions, simulated sunlight (xenon lamp light source, AM 1.5G, 100mW cm⁻¹) was introduced. -2 The working electrode surface was irradiated to perform photo-assisted electrocatalysis tests.

[0055] The results of the linear sweep voltammetry (LSV) test are as follows: Figure 3 As shown. At 100mA cm -2 At the given current density, the potential of this electrode in soda ash solution is 1.63V (vs. RHE, the same below); after the addition of cyclohexanol, the potential drops to 1.41V; after the introduction of light, the potential further decreases to 1.39V.

[0056] (5) Product analysis: under a constant current density of 50 mA cm⁻¹ -2 Electrolysis was performed for 10 hours, and the electrolyte was collected. The product was analyzed by high-performance liquid chromatography (HPLC), and quantification was performed using adipic acid as a standard. Calculations showed that the Faraday yield of adipic acid was 76.3% under light-free conditions; under light conditions, the yield increased to 80.2% (data corresponds to...). Figure 4 The conversion rate is close to 100%.

[0057] Example 2 The difference between this embodiment and Example 1 is that in the hydrothermal reaction of step two, the molar ratio of Ni(NO3)2·6H2O to Fe(NO3)3·9H2O is 1:2. Other steps and parameters are the same as in Example 1. The resulting electrode is reacted in 1 M KOH containing 0.1 M cyclohexanol at 100 mA cm⁻¹. -2 The potential at the current density is 1.43 V, which drops to 1.40 V after illumination.

[0058] Example 3 The difference between this embodiment and Embodiment 1 is that the phosphating temperature in step three is 400°C. Other steps and parameters are the same as in Embodiment 1. The resulting electrode is heated in 1 M KOH containing 0.1 M cyclohexanol at 100 mA cm⁻¹. -2 The potential at the current density is 1.42V, which drops to 1.40V after illumination.

[0059] Comparative Example 1 The difference between this comparative example and Example 1 is that in step two, no iron source Fe(NO3)3·9H2O is added; only a nickel source is used. Other steps and parameters are the same as in Example 1. The resulting electrode is nickel phosphide / nickel foam (NF / Ni-P). Under the same testing conditions, this electrode was tested in 1 M KOH containing 0.1 M cyclohexanol at 100 mA cm⁻¹. -2 The potential at the current density was 1.50 V, which was much higher than that of the electrode in Example 1, and the light-assisted effect was not obvious, with the adipic acid yield being only 68.5%.

[0060] Comparative Example 2 The difference between this comparative example and Example 1 is that the phosphating treatment in step three is omitted. The precursor obtained in step (2) of Example 1 was directly used as the working electrode for testing. Under the same test conditions, the electrode was tested in 1M KOH containing 0.1 M cyclohexanol at 100 mA cm⁻¹. -2 The potential at the current density is as high as 1.58 V, and the activity decays rapidly during the test, with the adipic acid yield being only 42.1%.

[0061] Performance Testing: Electrochemical performance tests were all conducted in a standard three-electrode system. The prepared self-supporting electrode was used directly as the working electrode (exposed area 1 cm²). 2 The Hg / HgO electrode was used as the reference electrode, and the carbon rod as the counter electrode. The electrolyte environment was a 1 M KOH solution. Linear sweep voltammetry (LSV) curves were tested at room temperature with a scan rate of 5 mV / s. -1 The light-assisted test used a simulated solar light source (AM 1.5G, 100 mW cm⁻¹). -2 The working electrode surface was vertically irradiated. Product analysis was performed using high-performance liquid chromatography (HPLC) to quantitatively detect the electrolyte and calculate the Faraday yield of adipic acid. The results are shown in Table 1.

[0062] Table 1

[0063] Results analysis: The nickel phosphide-iron phosphide self-supported electrodes prepared in Examples 1-3 all exhibited excellent catalytic activity in the cyclohexanol oxidation reaction. After introducing 0.1 M cyclohexanol, the oxidation potential of Example 1 (1.41 V) was significantly lower than that of the pure oxygen evolution reaction (OER) (1.63 V), with a negative shift of approximately 220 mV. This phenomenon indicates that the oxidation kinetics of cyclohexanol molecules on the electrode surface are superior to those of the water splitting reaction, and the electrode possesses a high degree of selective catalytic activity towards the target substrate. Furthermore, after the introduction of light irradiation, the reaction potential of Example 1 further decreased to 1.39 V, and the Faraday yield increased from 76.3% to 80.2%, fully verifying the excellent photoelectric synergistic response characteristics of this material.

[0064] Comparative Example 1 used only a nickel source to prepare a single nickel phosphide electrode. Its potential at the same current density was as high as 1.50 V, significantly higher than the 1.41 V of Example 1, and the adipic acid yield was only 68.5%. This indicates that the introduction of iron is crucial for regulating the electronic structure of nickel-based phosphides, and the Ni-Fe bimetallic synergistic effect significantly lowers the reaction energy barrier and improves catalytic efficiency.

[0065] Comparative Example 2, without phosphating treatment, directly used the hydroxide precursor as the electrode. Its potential reached a high of 1.58 V, and the activity decayed rapidly during the test, with a yield of only 42.1%. This is attributed to the poor conductivity and unstable chemical properties of metal hydroxides. Phosphating treatment not only endows the material with metal-like conductivity and accelerates electron transfer, but also significantly enhances the material's corrosion resistance and structural stability in alkaline electrolytes.

[0066] Comparing Examples 1 and 2 reveals that the nickel-iron ratio has a significant impact on catalytic activity. The performance of Example 1 (Ni:Fe ≈ 2:1) is superior to that of Example 2 (Ni:Fe = 1:2), indicating that a suitable nickel-rich environment may be more conducive to the formation of active centers or the optimization of electronic structure.

[0067] Comparing Examples 1 and 3, it can be seen that when the phosphating temperature is increased from 350°C to 400°C, the potential increases slightly (from 1.41 V to 1.42 V). This may be because excessively high temperatures cause partial aggregation or sintering of the nanosheet structure, reducing the electrochemically active surface area, suggesting that 350°C is a better phosphating process window.

[0068] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Furthermore, it should be understood that after reading the above teachings of this application, those skilled in the art can make various alterations or modifications to this application, and the equivalent forms obtained also fall within the scope of protection of this application. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a nickel phosphide-iron phosphide self-supporting electrode, characterized in that, Includes the following steps: Step 1: Cleaning and pre-treatment of the nickel foam; Step 2: The pretreated nickel foam is placed in a mixed solution containing nickel source and iron source for hydrothermal reaction to grow nickel-iron precursor on the surface of nickel foam, thus obtaining nickel foam with supported precursor. Step 3: The nickel foam of the load precursor is phosphated in the presence of a phosphorus source and under an inert atmosphere to obtain the nickel phosphide-iron phosphide self-supporting electrode.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the nickel source to the iron source is (1~4):

1.

3. The preparation method according to claim 1, characterized in that, The mixed solution also contains urea, and the concentration of urea is 0.05M to 0.2M.

4. The preparation method according to claim 1, characterized in that, The mixed solution also contains ammonium fluoride, the concentration of which is 0.01M to 0.05M.

5. The preparation method according to claim 1, characterized in that, The hydrothermal reaction temperature is 100℃-140℃, and the reaction time is 12 hours-24 hours.

6. The preparation method according to claim 1, characterized in that, The phosphorus source is sodium hypophosphite, and the mass ratio of the phosphorus source to the nickel foam of the supported precursor is greater than or equal to 5:

1.

7. The preparation method according to claim 1, characterized in that, The phosphating treatment is performed at a temperature of 300℃-400℃ for 2 hours.

8. A nickel phosphide-iron phosphide self-supporting electrode prepared by the preparation method according to any one of claims 1-7.

9. The application of the nickel phosphide-iron phosphide self-supporting electrode as described in claim 8 in the electrocatalytic oxidation of cyclohexanol to prepare adipic acid.

10. The application according to claim 9, characterized in that, Light is introduced into the electrocatalytic oxidation process to achieve photo-assisted electrocatalytic oxidation.

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