CoP / Ni5P4 / FeP nanometer material and preparation method and application thereof

Abstract

The invention provides a CoP / Ni5P4 / FeP nano material as well as preparation and application thereof, and the CoP / Ni5P4 / FeP nano material takes a carbon material as a carrier and contains CoP, Ni5P4 and FeP. The adopted transition metal phosphide has good conductivity and electrochemical stability, negative phosphorus atoms with strong electrostatic affinity are arranged in the transition metal phosphide, and the transition metal phosphide can be used as a proton acceptor and is beneficial to catalyzing the hydrogen production process; abundant active sites can be designed by means of morphology regulation, element doping, defect engineering and the like, for example, the superficial area of the catalyst can be increased by constructing different forms of catalysts, so that more abundant catalytic active sites are created, and particularly, an electrolyte diffusion path can be shortened and the active sites can be more effectively exposed by adopting a nanosheet structure; meanwhile, the conductivity is enhanced, and the catalytic efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of preparation and application of electrocatalysts, and particularly to a method for preparing an ultrathin nanosheet flower-like CoP / Ni5P4 / FeP / NC electrocatalyst and its application. Background Art

[0004] Hydrogen production by water electrolysis (electrochemical water splitting for hydrogen production) is a relatively convenient method for producing hydrogen. In an electrolytic cell filled with an electrolyte, direct current is passed through, and water molecules undergo an electrochemical reaction on the electrodes to decompose into hydrogen and oxygen. Electrochemical water splitting for hydrogen production is considered the most promising hydrogen production technology.

[0005] Currently, noble metal-based electrocatalysts exhibit good performance in electrochemical water splitting. In particular, due to the unique electronic structure of platinum, platinum and platinum-based materials are also the main commercially used catalysts for electrochemical water splitting for hydrogen production. However, due to their high cost and limited resources, their large-scale commercial application is restricted. Therefore, the development of affordable and efficient catalysts is of great significance for realizing the recycling of hydrogen energy. Summary of the Invention

[0006] The present application provides a preparation and application of an electrocatalyst, which does not use noble metal catalysts and is particularly applied to hydrogen production by electrolyzing water in an alkaline environment, having excellent HER performance.

[0007] The first aspect of the present application is to provide a method for preparing a CoP / Ni5P4 / FeP nanomaterial, and the steps include:

[0008] Step 1, reacting an iron source with at least a dicarboxylic acid to prepare an iron complex precursor;

[0009] Step 2, reacting the iron complex precursor with a cobalt source and a nickel source in the presence of a base, a complexing agent, and a polymer, and collecting the solid reaction product;

[0010] Step 3, phosphating the solid reaction product with a phosphating reagent to obtain a CoP / Ni5P4 / FeP / NC nanomaterial.

[0011] In a preferred embodiment, the iron source provides one or more of Fe 3+ 、Fe 2+ and can be, for example, one or several selected from inorganic salts, organic salts, oxides, and hydroxides of iron, such as one or several selected from chlorides, bromides, sulfides, carbonates, nitrates, sulfates, acetates, oxides, hydroxides, formates, citrates, oleates, oxalates, etc. Specific examples can be one or several selected from: iron nitrate, ferrous chloride, ferrous sulfate, ammonium ferrous sulfate, and iron oleate.

[0012] In a preferred embodiment, the at least dibasic carboxylic acid may be selected from terephthalic acid, isophthalic acid, 2-aminoterephthalic acid, 2-methyl-1,4-benzenedicarboxylic acid, 2-hydroxyterephthalic acid, 2-nitroterephthalic acid, 2,5-dihydroxyterephthalic acid, trimellitic acid, succinic acid, glutaric acid, butyric acid, adipic acid, azelaic acid, sebacic acid, glutamic acid, aspartic acid, 1,4-naphthalenedicarboxylic acid, oxalic acid, maleic acid, etc.

[0013] In a preferred embodiment, the iron source and the at least dibasic carboxylic acid are dissolved in a first solvent, and the first solvent is preferably an aprotic solvent, such as those selected from amides, ketones, nitriles, sulfoxides, pyridines, ethers, hydrocarbons, etc. Specific examples may be selected from acetone, dimethyl sulfoxide, acetonitrile, N,N-dimethylformamide, carbon tetrachloride, benzene, pyridine, etc.

[0014] In a preferred embodiment, after the iron source and the at least dibasic carboxylic acid are dissolved in the first solvent, a hydrothermal reaction is carried out.

[0015] In a preferred embodiment, the molar ratio of the iron source to the at least dibasic carboxylic acid is preferably 1:(0.1 - 10), more preferably 1:(0.5 - 8); more preferably 1:(1 - 5).

[0016] In a preferred embodiment, the reaction temperature of the iron source and the at least dibasic carboxylic acid is preferably at least 50 °C, more preferably at least 80 °C, more preferably 100 - 300 °C, more preferably 150 - 250 °C, more preferably 170 - 220 °C.

[0017] In a preferred embodiment, the reaction time of the iron source and the at least dibasic carboxylic acid is preferably at least 0.5 h, more preferably 1 - 36 h, more preferably 3 - 33 h, more preferably 5 - 30 h, more preferably 6 - 27 h, more preferably 8 - 25 h, more preferably 10 - 24 h, more preferably 12 - 20 h, more preferably 15 - 18 h.

[0018] In a preferred embodiment, the cobalt source provides Co + 、Co 2+ 、Co 3+ 、Co 4+ One or more of them. More preferably, the cobalt source may be selected from one or more of organic salts, inorganic salts, oxides, hydroxides of cobalt, such as chlorides, bromides, sulfides, carbonates, nitrates, sulfates, acetates, oxides, hydroxides, formates, citrates, oleates, oxalates, etc. Specific examples may be selected from cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt stearate, cobalt formate, cobalt acetate, cobalt carbonate, cobalt citrate, cobalt naphthenate, cobalt stearate, cobalt isooctanoate, cobalt aminosulfonate, cobalt gluconate, etc.

[0019] In a preferred embodiment, the nickel source provides Ni 2+ , Ni 3+ or one or more of them. More preferably, the nickel source may be one or more selected from organic acid salts, inorganic acid salts, oxides, and hydroxides of nickel, such as chlorides, bromides, sulfides, carbonates, nitrates, sulfates, acetates, oxides, hydroxides, formates, citrates, oleates, oxalates, etc. Specific examples may be selected from nickel oxide, nickel hydroxide, nickel sulfate, nickel chloride, nickel bromide, nickel nitrate, nickel acetate, nickel propionate, nickel butyrate, nickel octanoate, nickel isooctanoate, nickel lactate, nickel benzoate, bis(acetylacetone)nickel, nickel salicylate, nickel oleate, etc.

[0020] In a preferred embodiment, the base may be selected from urea, hydroxides, ammonia, or organic amines, such as one or several selected from urea, potassium hydroxide, sodium hydroxide, ammonia water, and ethylamine.

[0021] In a preferred embodiment, the complexing agent may be selected from ammonium salts, such as ammonium chloride, ammonium fluoride, ammonium nitrate, ammonium bromide, ammonium carbonate, ammonium acetate, ammonium formate, etc.

[0022] In a preferred embodiment, the polymer main chain contains a cyclic structure, wherein the proportion of the number of cyclic structures in the total number of atoms constituting the main chain (regarding the cyclic structure as one atom) is preferably ≥40%, more preferably ≥50%, more preferably ≥70%, more preferably ≥80%, more preferably ≥90%, more preferably ≥95%, and more preferably the polymer main chain is formed by linking cyclic structures. Specific examples of polymers may be selected from: polyphenylene, polyphenylene ether, polypyrrole, polypyridine, polynorbornene, cycloolefin polymers (such as cyclohexene polymers, cyclopentene polymers), phenolic resins, etc.

[0023] In a preferred embodiment, in step 2, during the process of step 2, the polymer is polymerized by adding monomers. For example, pyrrole is added in step 2, and during the reaction process of step 2, pyrrole polymerizes to form polypyrrole; or cycloolefin is added in step 2, and during the reaction process of step 2, cycloolefin polymerizes to form a cycloolefin polymer; or norbornene is added in step 2, and during the reaction process of step 2, norbornene polymerizes to form polynorbornene; or pyridine is added in step 2, and during the reaction process of step 2, pyridine polymerizes to form polypyridine.

[0024] In a preferred embodiment, if necessary, a catalyst or initiator required for polymerization may be added in step 2.

[0025] Preferably, the polymer contains N heteroatoms. More preferably, the N heteroatoms are located on the polymer main chain or on the cyclic structure of the main chain. Therefore, more preferably, the monomer is selected from those containing a cyclic structure with N heteroatoms, such as pyrrole, 2,4-dimethyl-3-ethylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole, 2-acetyl-1-methylpyrrole, 2-acetylpyrrole, N-methyl-2-pyrrolecarboxaldehyde, methyl 1H-pyrrole-2-carboxylate, ethyl 1-H-pyrrole-2-carboxylate, ethyl 3,5-dimethyl-1H-pyrrole-2-carboxylate, ethyl 2,4-dimethyl-1H-pyrrole-3-carboxylate, 1H-pyrrole-3-carboxylic acid, 1H-pyrrole-2-carboxaldehyde, 1-(furan-2-ylmethyl)-1H-pyrrole, 3,5-dimethyl-1H-pyrrole-2-carboxaldehyde, ethyl 5-methyl-1H-pyrrole-2-carboxylate, 3,5-dimethyl-1H-pyrrole-2-carboxylic acid, pyridine, quinoline, isoquinoline, 4-methylpyridine, 4-vinylpyridine, 4-cyanopyridine, 2-vinylpyridine, 2-cyanopyridine, 2-ethylpyridine, 2-benzylpyridine, 2-hydroxyethylpyridine, 2-bromopyridine, 2-chloropyridine, 2,4-dimethylpyridine, 2,6-dimethylpyridine, etc.

[0026] In a preferred embodiment, the reaction in step 2 is carried out in a second solvent, and the second solvent can be one or more selected from water, alcohol, ketone, aldehyde, hydrocarbon, ether, nitrile, ester, furan, amide, such as water, methanol, ethanol, isopropanol, propanol, glycerol, acetone, formaldehyde, dichloromethane, chloroform, chlorobenzene, toluene, ethyl acetate, acetonitrile, petroleum ether, diethyl ether, tetrahydrofuran, etc.

[0027] In a preferred embodiment, the ratio of the iron complex precursor to cobalt is preferably 100 g∶(0.1 - 3) mol, more preferably 100 g∶(0.2 - 2.5) mol, and even more preferably 100 g∶(0.5 - 2) mol.

[0028] In a preferred embodiment, the ratio of the iron complex precursor to nickel is preferably 100 g∶(0.1 - 3) mol, more preferably 100 g∶(0.2 - 2.5) mol, and even more preferably 100 g∶(0.5 - 2) mol.

[0029] In a preferred embodiment, the ratio of the iron complex precursor to the base is preferably 100 g∶(10 - 300) mol, more preferably 100 g∶(20 - 280) mol, even more preferably 100 g∶(40 - 250) mol, even more preferably 100 g∶(50 - 200) mol, even more preferably 100 g∶(80 - 180) mol, and even more preferably 100 g∶(100 - 150) mol.

[0030] In a preferred embodiment, the ratio of the iron complex precursor to the complexing agent is preferably 100 g:(1 - 100) mol, more preferably 100 g:(2 - 80) mol, more preferably 100 g:(5 - 50) mol, more preferably 100 g:(10 - 40) mol, more preferably 100 g:(15 - 30) mol, more preferably 100 g:(20 - 25) mol.

[0031] In a preferred embodiment, the ratio of the iron complex precursor to the monomer for forming the polymer is preferably 100:(0.01 - 0.2) mol, more preferably 100 g:(0.015 - 0.18) mol, more preferably 100 g:(0.02 - 0.15) mol, more preferably 100 g:(0.03 - 0.12) mol, more preferably 100 g:(0.05 - 0.1) mol, more preferably 100 g:(0.06 - 0.08) mol.

[0032] In a preferred embodiment, the reaction temperature in step 2 is preferably at least 35°C, more preferably 40°C - 100°C, more preferably 50 - 80°C, more preferably 60 - 70°C.

[0033] In a preferred embodiment, the reaction time in step 2 is preferably at least 0.5 hours, more preferably 1 - 24 hours, more preferably 3 - 21 hours, more preferably 5 - 20 hours, more preferably 6 - 18 hours, more preferably 8 - 15 hours, more preferably 10 - 12 hours.

[0034] In a preferred embodiment, the phosphating reagent is preferably PH3. More preferably, the PH3 can be obtained from one or more of the following compounds: hypophosphorous acid, hypophosphite, hypophosphite ester, and the compounds can be selected from sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, ethyl hypophosphite, methyl hypophosphite, glycerol hypophosphite, etc.

[0035] In a preferred embodiment, the phosphating temperature is preferably at least 200°C, more preferably at least 250°C, more preferably 250 - 800°C, more preferably 300 - 600°C, more preferably 350 - 500°C.

[0036] In a preferred embodiment, the phosphating time is preferably at least 15 minutes, more preferably at least 0.5 hours, more preferably 0.5 - 10 hours, more preferably 1 - 8 hours, more preferably 2 - 6 hours, more preferably 3 - 5 hours.

[0037] In a preferred embodiment, the heating rate of the phosphating temperature is preferably 0.5 - 8 °C / min, more preferably 1 - 4 °C / min, still more preferably 1.5 - 3.5 °C / min, and even more preferably 2 - 3 °C / min.

[0038] The second aspect of this application is to provide a CoP / Ni5P4 / FeP nanomaterial, preferably obtained by the preparation method described in the first aspect.

[0039] In a preferred embodiment, the CoP / Ni5P4 / FeP nanomaterial uses a carbon material as a carrier and contains CoP, Ni5P4, and FeP; more preferably, the carbon material is an N-doped carbon material.

[0040] Preferably, the carbon material is obtained by heating a polymer.

[0041] The third aspect of this application provides an application of the CoP / Ni5P4 / FeP nanomaterial, which is used as an electrocatalyst in electrochemical water splitting.

[0042] In a preferred embodiment, the CoP / Ni5P4 / FeP nanomaterial is used for hydrogen production by electrochemical water splitting or in an electrochemical water splitting hydrogen production device.

[0043] In a more preferred embodiment, the hydrogen production by electrochemical water splitting is alkaline electrolytic water hydrogen production.

[0044] In this application, the introduction of Co and Ni adjusts the electronic structure of the catalyst material. The polymer serves as a carrier for the phosphide nanoparticles, slowing down the agglomeration of the particles and facilitating the improvement of the structural stability of the material. Finally, a nanoflower sphere structure assembled from ultrathin nanosheets is obtained. This structure has a large specific surface area, which can provide additional active sites, not only providing rich electron transport pathways but also promoting gas release, while enhancing electron transport kinetics and improving the electrochemical stability of CoP-NiP / FeP. Especially in the case of nitrogen-containing polymers, it is also transformed into an ultrathin nitrogen-doped carbon material, enhancing the conductivity of the material.

[0045] In this application, the introduction of Co and Ni elements adjusts the electron density on the material surface, induces interfacial charge rearrangement, and optimizes the adsorption of reaction intermediates, thereby improving the catalytic efficiency. In addition, the nanoparticles loaded on the nanosheets produce a rich interfacial effect, shortening the mass transfer path, accelerating charge transfer, and further improving the intrinsic activity of the catalyst.

[0046] The CoP / NiP / FeP electrocatalyst provided by this application has excellent hydrogen evolution and oxygen evolution catalytic performances in an alkaline electrolyte. When the current density is 10 mA / cm², its overpotential is lower than 130 mV, even as low as 128 mV, which is superior to most transition metal phosphide catalysts. Brief Description of the Drawings

[0047] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0048] Figure 1 is the SEM image of the CoP / Ni5P4 / FeP electrocatalyst of this application;

[0049] Figure 2 is the XRD pattern of the CoP / Ni5P4 / FeP electrocatalyst of this application;

[0050] Figure 3 is the high-resolution TEM image of the CoP / Ni5P4 / FeP electrocatalyst of this application;

[0051] Figure 4 is the alkaline hydrogen evolution performance curve of the CoP / Ni5P4 / FeP electrocatalyst of this application;

[0052] Figure 5 is the alkaline oxygen evolution performance curve of the CoP / Ni5P4 / FeP electrocatalyst of this application. Detailed Description of the Invention

[0053] This application provides a CoP / Ni5P4 / FeP nanomaterial and its preparation and application. The transition metal phosphide used has good electrical conductivity and electrochemical stability, and the negatively charged phosphorus atoms with strong electrostatic affinity inside can be used as proton acceptors, which helps the process of catalytic hydrogen production; and through means such as morphology regulation, element doping, and defect engineering, rich active sites can be designed. For example, by constructing catalysts with different morphologies, its surface area can be increased, thus creating more abundant catalytic active sites. In particular, the use of a nanosheet structure can shorten the electrolyte diffusion path, more effectively expose the active sites, and at the same time enhance the electrical conductivity, thereby improving the catalytic efficiency.

[0054] To make the purpose, technical solution and effects of this application clearer and more definite, the following further elaborates this application with reference to the drawings and by way of examples. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0055] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of this application are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0056] All raw materials used in the examples of this application are commercially available analytical pure products and have not been further purified.

[0057] The phase of the material prepared in this application was characterized by an XRD-D / MAX2200V PV type X-ray diffractometer (Cu target, K α rays as the radiation source, incident wavelength scanning the range of 2θ = 5° - 80° at a scanning speed of 8° / minute).

[0058] The morphology of the material prepared in this application was observed by a JSM-7500F scanning electron microscope from JEOL LTD, Japan, with an accelerating voltage of 20 kV. The transmission electron microscope used was a JEM-2100F from JEOL Ltd., Japan.

[0059] Example 1:

[0060] The present invention provides a super-thin nanosheet flower-like CoP / Ni5P4 / FeP / NC catalyst. The preparation method of this catalyst is as follows: First, an octahedral precursor is synthesized by a simple solvothermal method. Subsequently, the precursor is added to a mixed solution containing Co(NO3)2·6H2O, Ni(NO3)2·6H2O, pyrrole and ammonium fluoride. Due to the hydrolysis of Ni 2+ more H + is generated in the solution, which gradually corrodes the Fe precursor, and the released Fe ions react with Co 2+ and Ni 2+ to form the corresponding layered hydroxide. At the same time, the Fe ions on the surface of the precursor oxidize pyrrole into polypyrrole, and the polypyrrole and the layered hydroxide are intertwined together; the precursor acts as a sacrificial template and undergoes ligand exchange under the action of polypyrrole to obtain a nanosheet self-assembled nanoflower sphere. Finally, phosphidation is carried out to obtain the CoP / Ni5P4 / FeP / NC electrocatalyst.

[0061] The specific steps include:

[0062] Step 1:

[0063] Mix FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide in a molar ratio of 1:1:280 and stir for 60 minutes. Then transfer the mixed solution to a hydrothermal reaction kettle and react at 150 °C for 15 hours.

[0064] After cooling to room temperature, take out the crystals, wash them with methanol and ethanol, and then place them in a vacuum drying oven at 60 °C to dry overnight to obtain the crystals.

[0065] Step 2:

[0066] Take 20 mg of the precursor, 0.25 mmol of cobalt nitrate hexahydrate, 0.25 mmol of nickel nitrate hexahydrate, 10 mmol of urea and 5 mmol of NH4F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then, add 4 mL of pyrrole to the mixed solution.

[0067] Reflux the mixture at 60 °C for 12 hours. Subsequently, centrifuge and wash with ethanol and water respectively. Finally, place the obtained product in a vacuum drying oven at 60 °C to dry for 12 hours to obtain a powder sample.

[0068] Step 3

[0069] Subsequently, take 10 mg of the above-obtained powder sample and place it at the downwind position of a porcelain boat, and place 100 mg of sodium hypophosphite at the upwind position of the porcelain boat. Then place it in a tube furnace with nitrogen flowing through, and heat it to 350 °C at a heating rate of 2 °C / min for annealing for 2 hours. Cool to room temperature.

[0070] From Figure 1 the SEM, it can be seen that the prepared CoP / Ni5P4 / FeP / NC electrocatalyst presents a nano "flower ball" structure composed of nano "petals". This hierarchical structure has a large specific surface area, which is conducive to exposing more active sites, effectively promoting the mass transfer rate and charge transfer, and enhancing the intrinsic catalytic activity of the catalyst.

[0071] Figure 2 the XRD results show that the electrocatalyst phase is mainly composed of CoP, Ni5P4 and FeP. From Figure 3 the high-resolution TEM observation results are consistent with the XRD results. The prepared catalyst has a high crystallinity, indicating the successful preparation of the CoP / Ni5P4 / FeP / NC electrocatalyst.

[0072] Electrochemical performance test:

[0073] 1. Preparation of KOH solution

[0074] Dissolve KOH in 50 mL of ultrapure water. After the KOH solution is completely dissolved and cooled, make up the volume to 100 mL in a volumetric flask to obtain a 1 mol / L KOH electrolyte solution.

[0075] 2. Preparation of nickel foam

[0076] Immerse a piece of nickel foam into hydrochloric acid solution and sonicate for 10 minutes, then sonicate the surface with acetone solution for 10 minutes, and subsequently sonicate with ethanol and deionized water for 30 minutes respectively.

[0077] 3. Preparation of working electrode

[0078] Weigh 3 mg of the electrocatalyst sample, disperse it in a mixed solution of 165 μL of deionized water and 55 μL of ethanol, and sonicate until evenly dispersed. Then add 20 μL of Nafion and sonicate for 30 minutes. Slowly pipette 120 μL of the dispersion onto the pre-treated nickel foam, and leave it to dry in a vacuum oven for 2 hours to successfully prepare the working electrode.

[0079] 4. Activation treatment of electrocatalyst

[0080] (1) For the hydrogen evolution reaction (HER) by electrochemistry, a three-electrode system is used. The counter electrode is a graphite rod electrode, the reference electrode is a Hg / HgO electrode, and the electrolyte is 1 mol / L KOH.

[0081] (2) Activation by cyclic voltammetry (CV): Use a CHI 660E electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd. with a standard three-electrode system. Adopt the CV program. The HER test range is 0 - 0.2 V vs. RHE, the scanning rate is 100 mV / s, and cycle 100 times until the electrode reaches a stable state.

[0082] 5. Linear sweep voltammetry (LSV) test

[0083] After activation, switch the program to linear sweep voltammetry 1 program. The HER test range is -0.4 - 0.1 V vs. RHE, and the scanning rate is 5 mV / s (using automatic IR compensation with a 90% compensation level).

[0084] 6. Stability test

[0085] Measure by chronopotentiometry and chronoamperometry.

[0086] Comparative Example 1:

[0087] Step 1:

[0088] Mix FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide in a molar ratio of 1:1:280 and stir for 60 minutes. Then transfer the mixed solution to a hydrothermal reaction kettle and react at 150 °C for 15 hours.

[0089] After cooling to room temperature, take out the crystals, wash them with methanol and ethanol, and then place them in a vacuum drying oven at 60 °C to dry overnight to obtain the crystals.

[0090] Step 2:

[0091] Take 20 mg of the precursor, 0.25 mmol of nickel nitrate hexahydrate, 10 mmol of urea and 5 mmol of NH4F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then add 4 mL of pyrrole to the mixed solution.

[0092] Reflux the mixture at 60 °C for 12 hours. Then centrifuge and wash with ethanol and water respectively. Finally, place the obtained product in a vacuum drying oven at 60 °C to dry for 12 hours to obtain a powder sample.

[0093] Step 3

[0094] Subsequently, take 10 mg of the above-obtained powder sample and place it at the downwind position of the porcelain boat, and place 100 mg of sodium hypophosphite at the upwind position of the porcelain boat. Then place it in a tube furnace with nitrogen flowing through, and heat it to 350 °C at a heating rate of 2 °C / min for annealing for 2 hours. Cool to room temperature.

[0095] Prepare the working electrode in the manner of Example 1 and conduct electrochemical performance tests.

[0096] Comparative Example 2:

[0097] Step 1:

[0098] Mix FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide in a molar ratio of 1:1:280 and stir for 60 minutes. Then transfer the mixed solution to a hydrothermal reaction kettle and react at 150 °C for 15 hours.

[0099] After cooling to room temperature, take out the crystals, wash them with methanol and ethanol, and then place them in a vacuum drying oven at 60 °C to dry overnight to obtain the crystals.

[0100] Step 2:

[0101] Take 20 mg of the precursor, 0.25 mmol of cobalt nitrate hexahydrate, 10 mmol of urea and 5 mmol of NH4F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then add 4 mL of pyrrole to the mixed solution.

[0102] Reflux the mixture at 60 °C for 12 h. Subsequently, centrifuge and wash with ethanol and water respectively. Finally, dry the obtained product in a vacuum drying oven at 60 °C for 12 h to obtain a powder sample.

[0103] Step 3

[0104] Subsequently, take 10 mg of the above-obtained powder sample and place it at the downwind position of the porcelain boat, and place 100 mg of sodium hypophosphite at the upwind position of the porcelain boat. Then place it in a tube furnace filled with nitrogen and heat it to 350 °C at a heating rate of 2 °C / min for annealing for 2 h. Cool to room temperature.

[0105] Prepare the working electrode and conduct electrochemical performance tests in the same manner as in Example 1.

[0106] Comparative Example 3:

[0107] Step 1:

[0108] Mix FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide in a molar ratio of 1:1:280 and stir for 60 min. Then transfer the mixed solution to a hydrothermal reaction kettle and react at 150 °C for 15 h.

[0109] After cooling to room temperature, take out the crystals, wash them with methanol and ethanol, and then place them in a vacuum drying oven at 60 °C to dry overnight to obtain the crystals.

[0110] Step 2:

[0111] Take 20 mg of the precursor, 0.5 mmol of cobalt nitrate, 0.5 mmol of nickel nitrate, 10 mmol of urea and 5 mmol of NH4F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then add 4 mL of pyrrole to the mixed solution.

[0112] Reflux the mixture at 60 °C for 12 h. Subsequently, centrifuge and wash with ethanol and water respectively. Finally, dry the obtained product in a vacuum drying oven at 60 °C for 12 h to obtain a powder sample.

[0113] Step 3

[0114] Subsequently, take 10 mg of the above-obtained powder sample and place it at the downwind position of the porcelain boat, and place 100 mg of sodium hypophosphite at the upwind position of the porcelain boat. Then place it in a tube furnace filled with nitrogen and heat it to 350 °C at a heating rate of 2 °C / min for annealing for 2 h. Cool to room temperature.

[0115] Prepare the working electrode and conduct electrochemical performance tests in the same manner as in Example 1.

[0116] Comparative Example 4:

[0117] Using Pt / C as the working electrode, the electrochemical performance test was carried out in the same way as in Example 1.

[0118] Table 1. Performance comparison between Example 1 and Comparative Examples 1-5

[0119]

[0120] Table 1, Figure 4 and 5 It can be seen that the electrocatalyst of the present application exhibits good catalytic activity for hydrogen evolution and oxygen evolution reactions. In an alkaline electrolyte, when the current density reaches 10 mA / cm³, the overpotential of the electrocatalyst prepared in Example 1 is 128 mV. In contrast, without the introduction of Ni and Co, the performance of the prepared catalyst is poor, manifested as a higher overpotential.

[0121] Example 2:

[0122] Step 1:

[0123] FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide were mixed and stirred for 60 minutes at a molar ratio of 0.75:1:280, and then the mixed solution was transferred to a hydrothermal reaction kettle and reacted at 150 °C for 15 hours.

[0124] After cooling to room temperature, the crystals were taken out, washed with methanol and ethanol, and then placed in a vacuum drying oven at 60 °C to dry overnight to obtain the crystals.

[0125] Step 2:

[0126] Take 20 mg of the precursor, 0.25 mmol of cobalt nitrate hexahydrate, 0.25 mmol of nickel nitrate hexahydrate, 10 mmol of urea and 5 mmol of NH4F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then 4 mL of pyrrole was added to the mixed solution.

[0127] The mixture was refluxed at 60 °C for 12 hours. Subsequently, it was centrifuged and washed with ethanol and water respectively, and finally the obtained product was placed in a vacuum drying oven at 60 °C to dry for 12 hours to obtain a powder sample.

[0128] Step 3

[0129] Subsequently, 10 mg of the above-obtained powder sample was placed at the downwind position of the porcelain boat, 100 mg of sodium hypophosphite was placed at the upwind position of the porcelain boat, and then it was placed in a tubular furnace with nitrogen flowing through, and heated to 350 °C at a heating rate of 2 °C / min for annealing for 2 hours. Cool to room temperature.

[0130] For the electrochemical performance test, referring to Example 1, the overpotential at a current density of 10 mA / cm³ was 129 mV.

[0131] Example 3:

[0132] Step 1:

[0133] Mix FeCl₃·6H₂O, terephthalic acid, and N,N-dimethylformamide in a molar ratio of 1.25:1:280 and stir for 60 minutes. Then transfer the mixed solution to a hydrothermal reaction kettle and react at 150 °C for 15 hours.

[0134] After cooling to room temperature, take out the crystals, wash them with methanol and ethanol, and then place them in a vacuum drying oven at 60 °C to dry overnight to obtain the crystals.

[0135] Step 2:

[0136] Take 20 mg of the precursor, 0.25 mmol of cobalt nitrate hexahydrate, 0.25 mmol of nickel nitrate hexahydrate, 10 mmol of urea, and 5 mmol of NH₄F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then add 4 mL of pyrrole to the mixed solution.

[0137] Reflux the mixture at 60 °C for 12 hours. Then centrifuge and wash with ethanol and water respectively. Finally, place the obtained product in a vacuum drying oven at 60 °C to dry for 12 hours to obtain a powder sample.

[0138] Step 3

[0139] Subsequently, take 10 mg of the above-obtained powder sample and place it at the downwind position of the porcelain boat, and place 100 mg of sodium hypophosphite at the upwind position of the porcelain boat. Then place it in a tube furnace with nitrogen flowing through, and heat it to 350 °C at a heating rate of 2 °C / minute for annealing for 2 hours. Cool to room temperature.

[0140] For the electrochemical performance test, referring to Example 1, the overpotential at a current density of 10 mA / cm³ was 128 mV.

[0141] Example 4:

[0142] Step 1:

[0143] Mix FeCl₃·6H₂O, terephthalic acid, and N,N-dimethylformamide in a molar ratio of 0.75:1:280 and stir for 60 minutes. Then transfer the mixed solution to a hydrothermal reaction kettle and react at 100 °C for 15 hours.

[0144] After cooling to room temperature, take out the crystals, wash them with methanol and ethanol, and then place them in a vacuum drying oven at 60 °C to dry overnight to obtain the crystals.

[0145] Step 2:

[0146] Take 20 mg of the precursor, 0.25 mmol of cobalt nitrate hexahydrate, 0.25 mmol of nickel nitrate hexahydrate, 10 mmol of urea and 5 mmol of NH4F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then add 4 mL of pyrrole to the mixed solution.

[0147] Reflux the mixture at 60 °C for 12 hours. Subsequently, centrifuge and wash with ethanol and water respectively, and finally dry the obtained product in a vacuum drying oven at 60 °C for 12 hours to obtain a powder sample.

[0148] Step 3

[0149] Subsequently, take 10 mg of the above-obtained powder sample and place it at the downwind position of the porcelain boat, and place 100 mg of sodium hypophosphite at the upwind position of the porcelain boat. Then place it in a tubular furnace with nitrogen flowing through, and heat it to 350 °C at a heating rate of 2 °C per minute for annealing for 2 hours. Cool to room temperature.

[0150] The electrochemical performance test refers to Example 1, and the overpotential at a current density of 10 mA / cm³ is 128 mV.

[0151] Example 5:

[0152] Step 1:

[0153] Mix FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide in a molar ratio of 0.75:1:280 and stir for 60 minutes. Then transfer the mixed solution to a hydrothermal reaction kettle and react at 200 °C for 15 hours.

[0154] After cooling to room temperature, take out the crystals, wash them with methanol and ethanol, and then place them in a vacuum drying oven at 60 °C to dry overnight to obtain the crystals.

[0155] Step 2:

[0156] Take 20 mg of the precursor, 0.25 mmol of cobalt nitrate hexahydrate, 0.25 mmol of nickel nitrate hexahydrate, 10 mmol of urea and 5 mmol of NH4F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then add 4 mL of pyrrole to the mixed solution.

[0157] Reflux the mixture at 60 °C for 12 hours. Subsequently, centrifuge and wash with ethanol and water respectively, and finally dry the obtained product in a vacuum drying oven at 60 °C for 12 hours to obtain a powder sample.

[0158] Step 3

[0159] Subsequently, take 10 mg of the obtained powder sample and place it at the downwind position of the porcelain boat, and place 100 mg of sodium hypophosphite at the upwind position of the porcelain boat. Then place it in a tube furnace with nitrogen flowing through it and heat it to 350 °C at a heating rate of 2 °C per minute for annealing for 2 hours. Cool to room temperature.

[0160] For the electrochemical performance test, refer to Example 1. The overpotential at a current density of 10 mA / cm³ is 129 mV.

[0161] Example 5:

[0162] Step 1:

[0163] Mix FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide in a molar ratio of 0.75:1:280 and stir for 60 minutes. Then transfer the mixed solution to a hydrothermal reaction kettle and react at 150 °C for 15 hours.

[0164] After cooling to room temperature, take out the crystals, wash them with methanol and ethanol, and then place them in a vacuum drying oven at 60 °C for drying overnight to obtain the crystals.

[0165] Step 2:

[0166] Take 20 mg of the precursor, 0.25 mmol of cobalt nitrate hexahydrate, 0.25 mmol of nickel nitrate hexahydrate, 10 mmol of urea and 5 mmol of NH4F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then add 4 mL of pyrrole to the mixed solution.

[0167] Reflux the mixture at 60 °C for 12 hours. Subsequently, centrifuge and wash with ethanol and water respectively. Finally, place the obtained product in a vacuum drying oven at 60 °C for drying for 12 hours to obtain a powder sample.

[0168] Step 3

[0169] Subsequently, take 10 mg of the obtained powder sample and place it at the downwind position of the porcelain boat, and place 100 mg of sodium hypophosphite at the upwind position of the porcelain boat. Then place it in a tube furnace with nitrogen flowing through it and heat it to 300 °C at a heating rate of 2 °C per minute for annealing for 2 hours. Cool to room temperature.

[0170] For the electrochemical performance test, refer to Example 1. The overpotential at a current density of 10 mA / cm³ is 129 mV.

[0171] Example 6:

[0172] Step 1:

[0173] Mix FeCl3·6H2O, terephthalic acid and N,N-dimethylformamide in a molar ratio of 0.75:1:280 and stir for 60 minutes. Then transfer the mixed solution to a hydrothermal reaction kettle and react at 150 °C for 15 hours.

[0174] After cooling to room temperature, take out the crystals, wash them with methanol and ethanol, and then place them in a vacuum drying oven at 60 °C to dry overnight to obtain the crystals.

[0175] Step 2:

[0176] Take 20 mg of the precursor, 0.25 mmol of cobalt nitrate hexahydrate, 0.25 mmol of nickel nitrate hexahydrate, 10 mmol of urea and 5 mmol of NH4F, and disperse them evenly in a mixed solvent of 45 mL of deionized water and 5 mL of ethanol. Then add 4 mL of pyrrole to the mixed solution.

[0177] Reflux the mixture at 60 °C for 12 hours. Subsequently, centrifuge and wash with ethanol and water respectively. Finally, place the obtained product in a vacuum drying oven at 60 °C to dry for 12 hours to obtain a powder sample.

[0178] Step 3

[0179] Subsequently, take 10 mg of the above-obtained powder sample and place it at the downwind position of the porcelain boat, and place 100 mg of sodium hypophosphite at the upwind position of the porcelain boat. Then place it in a tubular furnace with nitrogen flowing through, and heat it to 400 °C at a heating rate of 2 °C / minute for annealing for 2 hours. Cool to room temperature.

[0180] For the electrochemical performance test, refer to Example 1. The overpotential at a current density of 10 mA / cm³ is 128 mV.

[0181] The specific embodiments of the present application have been described in detail above, but they are only examples, and the present application is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present application are also within the scope of the present application. Therefore, equivalent transformations and modifications made without departing from the spirit and scope of the present application should be covered within the scope of the present application.

Claims

1. A method for preparing CoP / Ni5P4 / FeP nanomaterials, characterized in that the steps Including: Step 1: Reacting an iron source with at least a dicarboxylic acid to prepare an iron complex precursor; Step 2: Reacting the iron complex precursor with a cobalt source and a nickel source in the presence of a base, a complexing agent, and a polymer, and collecting the solid reaction product; Step 3: Phosphating the solid reaction product with a phosphating reagent to obtain a CoP / Ni5P4 / FeP / NC nanomaterial.

2. The method according to claim 1, wherein The iron source provides Fe 3+ , Fe 2+ or one or more of them, preferably one or several selected from inorganic acid salts, organic acid salts, oxides, and hydroxides of iron, such as selected from chlorides, bromides, sulfides, carbonates, nitrates, sulfates, acetates, oxides, hydroxides, formates, citrates, oleates, oxalates, etc. Specific examples may be selected from: one or several of iron nitrate, ferrous chloride, ferrous sulfate, ammonium ferrous sulfate, and iron oleate; The at least a dicarboxylic acid is selected from terephthalic acid, isophthalic acid, 2-aminoterephthalic acid, 2-methyl-1,4-benzenedicarboxylic acid, 2-hydroxyterephthalic acid, 2-nitroterephthalic acid, 2,5-dihydroxyterephthalic acid, trimesic acid, succinic acid, glutaric acid, butanedioic acid, adipic acid, azelaic acid, sebacic acid, glutamic acid, aspartic acid, 1,4-naphthalenedicarboxylic acid, oxalic acid, maleic acid; The iron source and the at least a dicarboxylic acid are dissolved in a first solvent, and the first solvent is preferably an aprotic solvent, such as those selected from amides, ketones, nitriles, sulfoxides, pyridines, ethers, hydrocarbons, etc. Specific examples can be selected from acetone, dimethyl sulfoxide, acetonitrile, N,N-dimethylformamide, carbon tetrachloride, benzene, pyridine; The cobalt source provides Co + , Co 2+ , Co 3+ , Co 4+ or one or more of them; preferably, the cobalt source is selected from one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of cobalt, such as chlorides, bromides, sulfides, carbonates, nitrates, sulfates, acetates, oxides, hydroxides, formates, citrates, oleates, oxalates, etc. Specific examples may include cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt stearate, cobalt formate, cobalt acetate, cobalt carbonate, cobalt citrate, cobalt naphthenate, cobalt stearate, cobalt isooctanoate, cobalt sulfamate, and cobalt gluconate; The nickel source provides Ni 2+ , Ni 3+ or one or more of them; preferably, the nickel source may be one or more selected from organic acid salts, inorganic acid salts, oxides, and hydroxides of nickel, such as chlorides, bromides, sulfides, carbonates, nitrates, sulfates, acetates, oxides, hydroxides, formates, citrates, oleates, oxalates, etc. Specific examples may be selected from nickel oxide, nickel hydroxide, nickel sulfate, nickel chloride, nickel bromide, nickel nitrate, nickel acetate, nickel propionate, nickel butyrate, nickel octanoate, nickel isooctanoate, nickel lactate, nickel benzoate, bis(acetylacetone)nickel, nickel salicylate, nickel oleate; The base can be selected from urea, hydroxides, ammonia, or organic amines, such as one or more selected from urea, potassium hydroxide, sodium hydroxide, ammonia water, ethylamine; The complexing agent can be selected from ammonium salts, such as ammonium chloride, ammonium fluoride, ammonium nitrate, ammonium bromide, ammonium carbonate, ammonium acetate, ammonium formate; The polymer main chain contains a cyclic structure. Among them, the proportion of the number of cyclic structures in the total number of atoms constituting the main chain is preferably ≥40%, more preferably ≥50%, more preferably ≥70%, more preferably ≥80%, more preferably ≥90%, more preferably ≥95%, and more preferably the polymer main chain is linked by cyclic structures. Specific examples of the polymer can be selected from: polyphenylene, polyphenylene ether, polypyrrole, polypyridine, polynorbornene, cycloolefin polymers (such as cyclohexene polymers, cyclopentene polymers), phenolic resins; The reaction in Step 2 is carried out in a second solvent, and the second solvent can be one or more selected from water, alcohols, ketones, aldehydes, hydrocarbons, ethers, nitriles, esters, furans, amides, etc., such as selected from water, methanol, ethanol, isopropanol, propanol, glycerol, acetone, formaldehyde, dichloromethane, chloroform, chlorobenzene, toluene, ethyl acetate, acetonitrile, petroleum ether, diethyl ether, tetrahydrofuran; The phosphating reagent is preferably PH3. More preferably, the PH3 can be obtained from one or more of the following compounds: hypophosphorous acid, hypophosphites, hypophosphites, and the compounds can be selected from sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, ethyl hypophosphite, methyl hypophosphite, glycerol hypophosphite.

3. The method according to claim 1, characterized in that, In Step 2, the polymer is polymerized by adding monomers during Step 2; preferably, the polymer contains N heteroatoms, and more preferably, the N heteroatoms are located on the polymer main chain or on the cyclic structure of the main chain; more preferably, the monomers are selected from those containing a cyclic structure with N heteroatoms, such as pyrrole, 2,4-dimethyl-3-ethylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole, 2-acetyl-1-methylpyrrole, 2-acetylpyrrole, N-methyl-2-pyrrolecarboxaldehyde, methyl 1H-pyrrole-2-carboxylate, ethyl 1-H-pyrrole-2-carboxylate, ethyl 3,5-dimethyl-1H-pyrrole-2-carboxylate, ethyl 2,4-dimethyl-1H-pyrrole-3-carboxylate, 1H-pyrrole-3-carboxylic acid, 1H-pyrrole-2-carboxaldehyde, 1-(furan-2-ylmethyl)-1H-pyrrole, 3,5-dimethyl-1H-pyrrole-2-carboxaldehyde, ethyl 5-methyl-1H-pyrrole-2-carboxylate, 3,5-dimethyl-1H-pyrrole-2-carboxylic acid, pyridine, quinoline, isoquinoline, 4-methylpyridine, 4-vinylpyridine, 4-cyanopyridine, 2-vinylpyridine, 2-cyanopyridine, 2-ethylpyridine, 2-benzylpyridine, 2-hydroxyethylpyridine, 2-bromopyridine, 2-chloropyridine, 2,4-dimethylpyridine, 2,6-dimethylpyridine.

4. The method according to claim 3, characterized in that The ratio of the iron complex precursor to the monomers forming the polymer is preferably 100∶(0.01 - 0.2) mol, more preferably 100 g∶(0.015 - 0.18) mol, more preferably 100 g∶(0.02 - 0.15) mol, more preferably 100 g∶(0.03 - 0.12) mol, more preferably 100 g∶(0.05 - 0.1) mol, more preferably 100 g∶(0.06 - 0.08) mol.

5. The method according to claim 1, wherein The molar ratio of the iron source to the at least dibasic carboxylic acid is 1∶(0.1 - 10), more preferably 1∶(0.5 - 8); more preferably 1∶(1 - 5); The ratio of the iron complex precursor to cobalt is preferably 100 g∶(0.1 - 3) mol, more preferably 100 g∶(0.2 - 2.5) mol, more preferably 100 g∶(0.5 - 2) mol; The ratio of the iron complex precursor to nickel is preferably 100 g∶(0.1 - 3) mol, more preferably 100 g∶(0.2 - 2.5) mol, more preferably 100 g∶(0.5 - 2) mol; The ratio of the iron complex precursor to the base is preferably 100 g∶(10 - 300) mol, more preferably 100 g∶(20 - 280) mol, more preferably 100 g∶(40 - 250) mol, more preferably 100 g∶(50 - 200) mol, more preferably 100 g∶(80 - 180) mol, more preferably 100 g∶(100 - 150) mol; The ratio of the iron complex precursor to the complexing agent is preferably 100 g∶(1 - 100) mol, more preferably 100 g∶(2 - 80) mol, more preferably 100 g∶(5 - 50) mol, more preferably 100 g∶(10 - 40) mol, more preferably 100 g∶(15 - 30) mol, more preferably 100 g∶(20 - 25) mol.

6. The method according to claim 1, wherein The reaction temperature of the iron source with at least a dicarboxylic acid is at least 50 °C, more preferably at least 80 °C, more preferably 100 - 300 °C, more preferably 150 - 250 °C, more preferably 170 - 220 °C; The reaction time of the iron source with at least a dicarboxylic acid is at least 0.5 h, more preferably 1 - 36 h, more preferably 3 - 33 h, more preferably 5 - 30 h, more preferably 6 - 27 h, more preferably 8 - 25 h, more preferably 10 - 24 h, more preferably 12 - 20 h, more preferably 15 - 18 h; The reaction temperature in Step 2 is preferably at least 35 °C, more preferably 40 °C - 100 °C, more preferably 50 - 80 °C, more preferably 60 - 70 °C; The reaction time in Step 2 is preferably at least 0.5 hour, more preferably 1 - 24 hours, more preferably 3 - 21 hours, more preferably 5 - 20 hours, more preferably 6 - 18 hours, more preferably 8 - 15 hours, more preferably 10 - 12 hours; The phosphating temperature is preferably at least 200 °C, more preferably at least 250 °C, more preferably 250 - 800 °C, more preferably 300 - 600 °C, more preferably 350 - 500 °C; The phosphating time is preferably at least 15 minutes, more preferably at least 0.5 hour, more preferably 0.5 - 10 hours, more preferably 1 - 8 hours, more preferably 2 - 6 hours, more preferably 3 - 5 hours; The heating rate of the phosphating temperature is preferably 0.5 - 8 °C / min, more preferably 1 - 4 °C / min, more preferably 1.5 - 3.5 °C / min, more preferably 2 - 3 °C / min.

7. The CoP / Ni5P4 / FeP nanomaterial obtained by the method according to claim 1, characterized in that, The CoP / Ni5P4 / FeP nanomaterial is supported on a carbon material and contains CoP, Ni5P4, and FeP.

8. The CoP / Ni5P4 / FeP nanomaterial according to claim 7, characterized in that, The carbon material is an N-doped carbon material.

9. Use of the CoP / Ni5P4 / FeP nanomaterial according to claim 8, characterized in that, The CoP / Ni5P4 / FeP nanomaterial is used as an electrocatalyst in electrochemical water splitting; preferably, the hydrogen production by electrochemical water splitting is alkaline electrolytic water hydrogen production.

10. The application according to claim 9, wherein, The CoP / Ni5P4 / FeP nanomaterial is used for hydrogen production by electrochemical water splitting, or for an electrochemical water splitting hydrogen production device.

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