Novel method for green confinement synthesis of small-size metal phosphide bifunctional catalyst from phosphorus source and application of catalyst

Abstract

The invention belongs to the technical field of electro-catalysis and energy materials, and particularly relates to a method for synthesizing a small-size metal phosphide catalyst from a novel phosphorus source in a green limited range and application of the catalyst. The method comprises the following steps: 1) weighing required raw materials including metal salt, a carbon-containing precursor and a phosphorus-containing complexing agent; 2) uniformly mixing the raw materials in the step 1); and 3) performing pyrolysis treatment on the product obtained in the step 2) to obtain the bifunctional catalyst. According to the technical scheme, the green, cheap and nontoxic phosphorus-containing complexing agent (such as diethylenetriaminepenta (methylene phosphonic acid) and ethylenediamine tetramethylenephosphonic acid) is adopted as the raw material, a larger number of transition metal phosphides with smaller size (nanoscale) are formed through the complexing confinement effect, the specific surface area is remarkably increased, more catalytic active sites are exposed, and the catalytic activity of the catalyst is improved. The kinetic performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalysis and energy materials, and specifically relates to a method for green confined synthesis of a small-sized metal phosphide bifunctional catalyst using a novel phosphorus source and the application of the catalyst. Background Art

[0002] Hydrogen is a zero-emission energy carrier and is widely considered to be the most promising alternative to traditional fossil fuels. Hydrogen can be produced by electrochemical water splitting technology. The electrolytic water splitting hydrogen production technology consists of the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode, both of which are multi-electron transfer processes with high reaction energy barriers. Therefore, it is crucial to construct efficient catalysts to reduce the overpotential and improve the overall energy conversion efficiency. Currently, the most effective HER and OER catalysts are mainly precious metals (Pt, Ir / Ru), but their high cost, limited reserves and poor stability limit their large-scale application. Therefore, it is imperative to develop efficient and low-cost bifunctional electrocatalysts for HER and OER.

[0003] Transition metal phosphides (TMPs) have attracted much attention due to their abundant reserves, unique electronic properties and excellent electrocatalytic activity. At present, transition metal phosphides are usually synthesized by liquid phase and gas-solid reaction routes using organic phosphorus and hypophosphite as raw materials. This synthesis route decomposes at high temperature to form phosphine, which is toxic, flammable and dangerous, thus severely limiting the large-scale preparation and practical application of transition metal phosphides. In addition, phosphides usually have limited inherent active sites, resulting in reaction activity that is still difficult to meet actual needs. Therefore, it is crucial to increase the exposure of active sites and establish effective transmission pathways during the electrocatalytic reaction. Moreover, single metal phosphides usually have only single functional catalytic activity and it is difficult to have good hydrogen evolution and oxygen evolution reaction performance at the same time. Therefore, how to develop a low-cost, non-toxic, non-corrosive gas-releasing new phosphorus source to simultaneously achieve green synthesis of phosphides and small nano-sized bifunctional metal catalysts is still a problem that needs to be solved in the field of electrocatalysis. Therefore, it is necessary to design a non-toxic and controllable green synthesis route to achieve large-scale preparation of small-sized metal phosphide nanoelectrocatalysts that can be used for total hydrolysis. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides a general preparation method and application of a nitrogen-phosphorus co-doped carbon-coated small-sized metal phosphide bifunctional catalyst. The method provided by the present invention has the characteristics of universality, green environmental protection, low cost, simple process, and easy industrialization.

[0005] The technical solution provided by the present invention is as follows:

[0006] A method for green confinement synthesis of a small-sized metal phosphide bifunctional catalyst using a novel phosphorus source, comprising the following steps:

[0007] 1) Weigh the required raw materials, including metal salts, carbon-containing precursors, and phosphorus-containing complexing agents;

[0008] 2) Uniformly mix the raw materials in step 1);

[0009] 3) Pyrolyze the product obtained in step 2) to obtain a nitrogen and phosphorus co-doped carbon-coated small-sized metal phosphide bifunctional catalyst.

[0010] Specifically, the carbon-containing precursor in step 1) is preferably selected from nitrogen-containing organic compounds, such as melamine, urea, dicyandiamide, etc.

[0011] Specifically, the metal salts in step 1) include nitrates, acetates, sulfates, chlorides, acetylacetonates, etc. of all metals.

[0012] Preferably, the metal salts include nickel metal salts and cobalt metal salts.

[0013] Specifically, the phosphorus-containing complexing agent is diethylenetriamine pentamethylenephosphonic acid (DTPMP) or ethylenediamine tetramethylenephosphonic acid (EDTMP).

[0014] Specifically, the dosage ratio of the metal salt to the phosphorus-containing complexing agent is 4 g:0.5 mmol.

[0015] Specifically, the mass ratio of the carbon-containing precursor to the metal salt is (1-20):1.

[0016] Specifically, the mixing in step 2) includes solid-phase mixing and liquid-phase mixing;

[0017] The solid-phase mixing refers to placing all the dry preparation raw materials in a mortar or a ball milling jar at room temperature and fully mixing and grinding them by hand or a ball mill for 10-30 minutes;

[0018] The liquid-phase mixing refers to mixing all the raw materials in a solvent (such as water), heating and stirring until completely evaporated to dryness.

[0019] Specifically, the pyrolysis treatment in step 3) is as follows: Under the protection of a protective gas, heat up to 700-1000 °C at a rate of 2-10 °C / min, then keep warm for 1-6 hours, and naturally cool to room temperature.

[0020] Specifically, the protective gas is any one of argon, argon-hydrogen, or nitrogen.

[0021] The present invention also provides the application of the catalyst prepared by the above preparation method in hydrogen production by water electrolysis.

[0022] Among the above materials provided by the present invention, the co-doping of nitrogen and phosphorus atoms has a synergistic effect, and different sizes and electronegativities regulate the electronic structure and charge density of the carbon material, etc.; the small nano-size synthesized by the phosphonic acid complexing agent has a larger specific surface area, which can expose more active sites, and the synthesized phosphide has excellent catalytic activity and stability for hydrogen evolution and oxygen evolution reactions.

[0023] The present invention also provides the application of the above nitrogen and phosphorus co-doped carbon-coated small-size metal phosphide bifunctional catalyst as a bifunctional catalyst for alkaline water electrolysis to produce hydrogen.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The present invention uses a phosphonic acid compound containing a phosphorus-containing complexing agent as a novel phosphorus source to prepare a nitrogen and phosphorus co-doped carbon-coated small-size metal phosphide bifunctional catalyst. The phosphorus-containing complexing agent is in-situ thermally decomposed and reduced to form a phosphide, effectively avoiding the generation of phosphine, and is expected to realize the green and large-scale preparation of phosphides; the small nano-size forms more active sites, and the synergistic effect of nitrogen and phosphorus atoms enhances the conductivity of the carbon material;

[0026] 2. The present invention utilizes the strong coordination ability of the phosphonic acid compound containing a phosphorus-containing complexing agent with metal ions. Through the complexation confinement effect, the metal ions can be uniformly dispersed, the particle agglomeration can be inhibited, and smaller-sized (nanoscale) and more numerous transition metal phosphides can be formed. The specific surface area of the transition metal phosphide is significantly increased, more catalytic active sites are exposed, and the kinetic performance of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is effectively improved.

[0027] 4. The present invention uses a phosphonic acid compound containing a phosphorus-containing complexing agent as a novel phosphorus source, and has universality through a simple synthesis process. Description of the Drawings

[0028] Figure 1 X-ray diffraction images (XRD images) of the catalysts for Examples 1-2, 5-6, 9-10, where (a) is for Examples 1 (Ni2P@NC), 5 (CoP@NC), 9 (NiCoP@NC), and (b) is for Examples 2 (Ni2P@NC), 6 (CoP@NC), 10 (NiCoP@NC);

[0029] Figure 2 (a), (b), and (c) are scanning electron microscope images (SEM images) of Examples 1 (Ni2P@NC), 5 (CoP@NC), and 9 (NiCoP@NC) respectively;

[0030] Figure 3 Transmission electron microscope image (TEM image) of the NiCoP@NC bifunctional catalyst prepared in Example 9;

[0031] Figure 4 Electrochemical performance diagrams of the catalysts of Examples 1-4, where (a) is the HER electrochemical performance diagram and (b) is the OER electrochemical performance diagram;

[0032] Figure 5 Electrochemical performance diagrams of the catalysts of Examples 5-8, where (a) is the HER electrochemical performance diagram and (b) is the OER electrochemical performance diagram;

[0033] Figure 6 Electrochemical performance diagrams of the catalysts of Examples 9-12, where (a) is the HER electrochemical performance diagram and (b) is the OER electrochemical performance diagram. Detailed implementation manners

[0034] Example 1:

[0035] Synthesis method of nitrogen and phosphorus co-doped carbon-coated Ni2P bifunctional catalyst, comprising the following steps:

[0036] Step 1: First, prepare nickel acetate tetrahydrate, select melamine with a high nitrogen content as the carbon precursor, and DTPMP as the new phosphorus source;

[0037] Step 2: Dissolve 4 g of melamine in 50 ml of deionized water and continuously stir at 50 °C to form a transparent and uniform solution. Subsequently, pour 2 mmol of nickel acetate tetrahydrate and 0.5 mmol of DTPMP into the above solution, and continuously stir and evaporate the mixed solution at 70 °C to obtain the pre-product A;

[0038] Step 3: Transfer the pre-product A to a corundum boat and place it in a tube furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat it from room temperature to 900 °C at a heating rate of 5 °C / min and keep it warm for 2 hours. After complete carbonization, naturally cool it to room temperature to obtain the target product, nitrogen and phosphorus co-doped carbon-coated Ni2P bifunctional catalyst;

[0039] Example 2:

[0040] Synthesis method of nitrogen and phosphorus co-doped carbon-coated Ni2P bifunctional catalyst, comprising the following steps:

[0041] Step 1: First, prepare nickel acetate tetrahydrate, select melamine with a high nitrogen content as the carbon precursor, and DTPMP as the new phosphorus source;

[0042] Step 2: Pour 4 g of melamine, 2 mmol of nickel acetate tetrahydrate and 0.5 mmol of DTPMP into a ball milling jar, set the rotation speed to 5000 revolutions, and ball mill for 30 minutes to obtain the pre-product A;

[0043] Step 3: Transfer the pre-product A to a corundum boat and place it in a tube furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat it from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool it to room temperature to obtain a nitrogen and phosphorus co-doped carbon-coated Ni2P bifunctional catalyst;

[0044] Example 3:

[0045] A method for synthesizing a nitrogen and phosphorus co-doped carbon-coated Ni2P bifunctional catalyst includes the following steps:

[0046] Step 1: First, prepare nickel acetate tetrahydrate, select melamine with a high nitrogen content as a carbon precursor, and EDTPMP as a novel phosphorus source;

[0047] Step 2: Dissolve 4 g of melamine in 50 ml of deionized water and continuously stir at 50 °C to form a transparent and uniform solution. Subsequently, pour 2 mmol of nickel acetate tetrahydrate and 0.5 mmol of EDTPMP into the above solution, and continuously stir and evaporate the mixed solution at 70 °C to obtain the pre-product A;

[0048] Step 3: Transfer the pre-product A to a corundum boat and place it in a tube furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat it from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool it to room temperature to obtain the target product, a nitrogen and phosphorus co-doped carbon-coated Ni2P bifunctional catalyst;

[0049] Example 4:

[0050] A method for synthesizing a nitrogen and phosphorus co-doped carbon-coated Ni2P bifunctional catalyst includes the following steps:

[0051] Step 1: First, prepare nickel acetate tetrahydrate, select melamine with a high nitrogen content as a carbon precursor, and EDTPMP as a novel phosphorus source;

[0052] Step 2: Pour 4 g of melamine, 2 mmol of nickel acetate tetrahydrate, and 0.5 mmol of EDTPMP into a ball milling jar, set the rotation speed to 5000 revolutions, and ball mill for 30 minutes to obtain the pre-product A;

[0053] Step 3: Transfer the pre-product A to a corundum boat and place it in a tube furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat it from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool it to room temperature to obtain a nitrogen and phosphorus co-doped carbon-coated Ni2P bifunctional catalyst;

[0054] Example 5:

[0055] A method for synthesizing a nitrogen and phosphorus co-doped carbon-coated CoP bifunctional catalyst includes the following steps:

[0056] Step 1: First, prepare cobalt acetate tetrahydrate, select melamine with a high nitrogen content as the carbon precursor, and DTPMP as the novel phosphorus source;

[0057] Step 2: Dissolve 4 g of melamine in 50 ml of deionized water and continuously stir at 50 °C to form a transparent and homogeneous solution. Subsequently, pour 2 mmol of cobalt acetate tetrahydrate and 0.5 mmol of DTPMP into the above solution in sequence, and continuously stir the mixed solution at 70 °C until it is evaporated to dryness to obtain the pre-product A;

[0058] Step 3: Transfer the pre-product A to a corundum boat and place it in a tube furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat it from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool it to room temperature to obtain the target product, the nitrogen and phosphorus co-doped carbon-coated CoP bifunctional catalyst;

[0059] Example 6:

[0060] A method for synthesizing a nitrogen and phosphorus co-doped carbon-coated CoP bifunctional catalyst, comprising the following steps:

[0061] Step 1: First, prepare cobalt acetate tetrahydrate, select melamine with a high nitrogen content as the carbon precursor, and DTPMP as the novel phosphorus source;

[0062] Step 2: Pour 4 g of melamine, 2 mmol of cobalt acetate tetrahydrate and 0.5 mmol of EDTPMP into a ball milling tank, set the rotation speed to 5000 revolutions, and ball mill for 30 minutes to obtain the pre-product A;

[0063] Step 3: Transfer the pre-product A to a corundum boat and place it in a tube furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat it from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool it to room temperature to obtain the nitrogen and phosphorus co-doped carbon-coated CoP bifunctional catalyst;

[0064] Example 7:

[0065] A method for synthesizing a nitrogen and phosphorus co-doped carbon-coated CoP bifunctional catalyst, comprising the following steps:

[0066] Step 1: First, prepare cobalt acetate tetrahydrate, select melamine with a high nitrogen content as the carbon precursor, and EDTPMP as the novel phosphorus source;

[0067] Step 2: Dissolve 4 g of melamine in 50 ml of deionized water and continuously stir at 50 °C to form a transparent and homogeneous solution. Subsequently, pour 2 mmol of cobalt acetate tetrahydrate and 0.5 mmol of EDTPMP into the above solution in sequence, and continuously stir the mixed solution at 70 °C until it is evaporated to dryness to obtain the pre-product A;

[0068] Step 3: Transfer the pre-product A to a corundum boat and place it in a tube furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat it from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool it to room temperature to obtain the target product, the nitrogen and phosphorus co-doped carbon-coated CoP bifunctional catalyst;

[0069] Example 8:

[0070] A method for synthesizing a nitrogen and phosphorus co-doped carbon-coated CoP bifunctional catalyst includes the following steps:

[0071] Step 1: First, prepare cobalt acetate tetrahydrate, select melamine with a high nitrogen content as the carbon-containing precursor, and EDTPMP as the novel phosphorus source;

[0072] Step 2: Pour 4 g of melamine, 2 mmol of cobalt acetate tetrahydrate, and 0.5 mmol of EDTPMP into a ball milling jar, set the rotation speed to 5000 revolutions, and ball mill for 30 minutes to obtain the pre-product A;

[0073] Step 3: Transfer the pre-product A to a corundum boat and place it in a tube furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat it from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool it to room temperature to obtain the nitrogen and phosphorus co-doped carbon-coated CoP bifunctional catalyst;

[0074] Example 9:

[0075] A method for synthesizing a nitrogen and phosphorus co-doped carbon-coated NiCoP bifunctional catalyst includes the following steps:

[0076] Step 1: First, prepare nickel acetate tetrahydrate and cobalt acetate tetrahydrate, select melamine with a high nitrogen content as the carbon-containing precursor, and DTPMP as the novel phosphorus source;

[0077] Step 2: Dissolve 4 g of melamine in 50 ml of deionized water and continuously stir at 50 °C to form a transparent and homogeneous solution. Subsequently, pour 1 mmol of nickel acetate tetrahydrate, 1 mmol of cobalt acetate tetrahydrate, and 0.5 mmol of DTPMP into the above solution in sequence. Keep stirring the mixed solution at 70 °C until it is evaporated to dryness to obtain the pre-product A;

[0078] Step 3: Transfer the pre-product A to a corundum boat and place it in a tube furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat it from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool it to room temperature to obtain the target product, the nitrogen and phosphorus co-doped carbon-coated NiCoP bifunctional catalyst;

[0079] Example 10:

[0080] Synthesis method of nitrogen and phosphorus co-doped carbon-coated NiCoP bifunctional catalyst, comprising the following steps:

[0081] Step 1: First, prepare nickel acetate tetrahydrate and cobalt acetate tetrahydrate, select melamine with a high nitrogen content as the carbon-containing precursor, and DTPMP as the novel phosphorus source;

[0082] Step 2: Pour 4 g of melamine, 1 mmol of nickel acetate tetrahydrate, 1 mmol of cobalt acetate tetrahydrate, and 0.5 mmol of DTPMP into a ball-milling jar, set the rotation speed to 5000 revolutions, and ball-mill for 30 minutes to obtain the pre-product A;

[0083] Step 3: Transfer the pre-product A to a corundum boat and place it in a tubular furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool to room temperature to obtain the nitrogen and phosphorus co-doped carbon-coated NiCoP bifunctional catalyst;

[0084] Example 11:

[0085] Synthesis method of nitrogen and phosphorus co-doped carbon-coated NiCoP bifunctional catalyst, comprising the following steps:

[0086] Step 1: First, prepare nickel acetate tetrahydrate and cobalt acetate tetrahydrate, select melamine with a high nitrogen content as the carbon-containing precursor, and DTPMP as the novel phosphorus source;

[0087] Step 2: Dissolve 4 g of melamine in 50 ml of deionized water and continuously stir at 50 °C to form a transparent and uniform solution. Subsequently, pour 1.5 mmol of nickel acetate tetrahydrate, 0.5 mmol of cobalt acetate tetrahydrate, and 0.5 mmol of DTPMP into the above solution in sequence. Continuously stir and evaporate the mixed solution at 70 °C to dryness to obtain the pre-product A;

[0088] Step 3: Transfer the pre-product A to a corundum boat and place it in a tubular furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool to room temperature to obtain the target product, the nitrogen and phosphorus co-doped carbon-coated NiCoP bifunctional catalyst;

[0089] Example 12:

[0090] Synthesis method of nitrogen and phosphorus co-doped carbon-coated NiCoP bifunctional catalyst, comprising the following steps:

[0091] Step 1: First, prepare nickel acetate tetrahydrate and cobalt acetate tetrahydrate, select melamine with a high nitrogen content as the carbon-containing precursor, and DTPMP as the novel phosphorus source;

[0092] Step 2: Dissolve 4 g of melamine in 50 ml of deionized water and continuously stir at 50 °C to form a transparent and homogeneous solution. Subsequently, pour 0.5 mmol of nickel acetate tetrahydrate, 1.5 mmol of cobalt acetate tetrahydrate, and 0.5 mmol of DTPMP into the above solution in sequence. Keep stirring the mixed solution at 70 °C until it is evaporated to dryness to obtain the pre-product A;

[0093] Step 3: Transfer the pre-product A to a corundum boat and place it in a tubular furnace. Under the protection of an argon-hydrogen (10 wt%) atmosphere, heat from room temperature to 900 °C at a heating rate of 5 °C / min and hold for 2 hours. After complete carbonization, naturally cool to room temperature to obtain the target product, the nitrogen and phosphorus co-doped carbon-coated NiCoP bifunctional catalyst;

[0094] Performance detection

[0095] Prepare the materials in Examples 1 - 12 into an ink. The preparation method of the ink is as follows: Add 5 mg of catalyst powder to a mixed solution (480 μL of water, 40 μL of Nafion, and 480 μL of ethanol), and ultrasonicate for 1 h to uniformly disperse the powder in the solution to obtain the catalyst ink; Next, load 60 μL of the ink onto a glassy carbon electrode, and the loading mass of the catalyst is 1.5 mg cm -2 . All electrochemical measurements are carried out at room temperature using a CHI-660E electrochemical workstation in a three-electrode electrochemical system. The glassy carbon electrode (GCE, with a diameter of 5 mm) loaded with the prepared catalyst is used as the working electrode, while a graphite rod is used as the counter electrode. The Hg / HgO electrode is selected as the reference electrode, and the electrochemical test is carried out in a 1.0 M KOH solution. During the whole experiment, all potentials have been converted to the potential values based on the reversible hydrogen electrode (RHE). When performing the hydrogen evolution reaction (HER), generally, the linear sweep potential is in the range of -0.8 to -1.5 V, and the scan rate is set to 5 mV / s; while when performing the oxygen evolution reaction (OER), the linear sweep potential range is usually 0 to 1 V, and the scan rate is 2 mV / s. The test results are shown in Table 1 below.

[0096] Table 1

[0097]

[0098] The above test data show that the nitrogen and phosphorus co-doped carbon-coated transition metal phosphide bifunctional catalyst prepared by this method has good performance, and under different mixing methods and phosphorus sources, the materials mixed by the liquid phase method using DTPMP as the phosphorus source generally have better performance.

[0099] In the above-mentioned embodiments, Step 1 is only an exemplary operation, and a large industrial stirring reactor can be used to improve production efficiency and product quantity.

[0100] As Figure 1 shown, the XRD patterns of a series of nitrogen and phosphorus co-doped carbon-coated transition metal phosphide bifunctional catalysts obtained by the method of the reference example are presented. It can be seen from the figure that all the synthesized catalysts are in pure phase.

[0101] As Figures 4 - 6 shown, the HER and OER polarization curves of a series of nitrogen and phosphorus co-doped carbon-coated transition metal phosphide bifunctional catalysts obtained by the method of the reference example are presented. The material exhibits good electrocatalytic performance, with good hydrogen evolution and oxygen evolution overpotentials.

[0102] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for green confinement synthesis of small-sized metal phosphide bifunctional catalysts using a novel phosphorus source, characterized in that, It includes the following steps: 1) Weigh the required raw materials, including metal salts, carbon precursors, and phosphorus-containing complexing agents; 2) Uniformly mix the raw materials in step 1); 3) Pyrolyze the product obtained in step 2) to obtain a bifunctional catalyst; Among them, the phosphorus-containing complexing agent is diethylenetriamine pentamethylenephosphonic acid or ethylenediamine tetra(methylene phosphonic acid).

2. The method for green confinement synthesis of a small-sized metal phosphide bifunctional catalyst using a novel phosphorus source according to claim 1, characterized in that, The carbon precursor described in step 1) includes melamine, urea, and dicyandiamide; The metal salts include metal nitrates, acetates, sulfates, chlorides, and acetylacetonates.

3. The method for green confinement synthesis of a small-sized metal phosphide bifunctional catalyst using a novel phosphorus source according to claim 1, characterized in that, The mass ratio of the carbon precursor to the metal salt in step 1) is (1-20):

1.

4. The method for green confinement synthesis of small-sized metal phosphide bifunctional catalyst using the novel phosphorus source according to claim 1, characterized in that, The dosage ratio of the metal salt to the phosphorus-containing complexing agent in step 1) is 4 g:0.5 mmol.

5. The method for green confinement synthesis of a small-sized metal phosphide bifunctional catalyst using a novel phosphorus source according to claim 1, wherein The mixing in step 2) includes solid-phase mixing and liquid-phase mixing.

6. The method for green confinement synthesis of a small-sized metal phosphide bifunctional catalyst using a novel phosphorus source according to claim 5, wherein The solid-phase mixing is to place all the raw materials in a mortar or a ball milling tank at room temperature and fully mix and grind them by hand grinding or a ball mill.

7. The method for green confinement synthesis of a small-sized metal phosphide bifunctional catalyst using a novel phosphorus source according to claim 5, wherein The liquid-phase mixing means mixing all the raw materials in a solvent, heating and stirring until completely evaporated to dryness.

8. The method for green confinement synthesis of a small-sized metal phosphide bifunctional catalyst using a novel phosphorus source according to claim 1, wherein The pyrolysis treatment in step 3) is as follows: Under the protection of a protective gas, heat up to 700-1000 °C at a rate of 2-10 °C / min, then keep it warm for 1-6 hours, and naturally cool to room temperature.

9. The method for green confinement synthesis of small-sized metal phosphide bifunctional catalyst with novel phosphorus source according to claim 8, characterized in that, The protective gas is any one of argon, argon-hydrogen, or nitrogen.

10. Application of a catalyst prepared by the method according to claims 1-9 in hydrogen production by electrolysis of water.

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