Self-supporting amorphous / crystalline NiCoP / NF multilevel structure electrocatalyst and preparation method and application thereof

Abstract

The invention provides a self-supporting amorphous / crystalline NiCoP / NF multilevel structure electrocatalyst as well as a preparation method and application of the self-supporting amorphous / crystalline NiCoP / NF multilevel structure electrocatalyst. The preparation method comprises the following steps: mixing nickel nitrate hexahydrate, cobalt nitrate hexahydrate, urea and ammonium fluoride, adding pretreated foamed nickel, separating, washing and drying to obtain a nickel-cobalt precursor loaded foamed nickel material; and calcining the nickel-cobalt precursor loaded foamed nickel material and sodium hypophosphite monohydrate in two porcelain boats to obtain the amorphous / crystalline NiCoP / NF multistage three-dimensional nano flower-shaped material. The catalyst has a self-supporting system, does not fall off in the catalysis process, can be applied to hydrogen evolution of acidic and alkaline electrolyzed water, can also be applied to hydrogen evolution of alkaline electrolyzed seawater, and keeps good stability. The catalyst provided by the invention not only improves effective utilization of seawater, but also provides guarantee for sustainable green energy development.

Description

Technical Field

[0001] The invention relates to a self-supporting amorphous / crystalline NiCoP / NF multi-level structure electrocatalyst and a preparation method and application thereof, belonging to the field of electrocatalysis. Background Art

[0002] Compared with the acidic hydrogen evolution reaction (HER), the Volmer step in alkaline electrolytes requires appropriate water molecule adsorption energy and additional energy to dissociate water molecules, so it is difficult to form intermediate hydrogen adsorption species. In order to achieve efficient hydrogen conversion, it is necessary to develop hydrogen evolution reaction electrocatalysts with high activity and long stability. The ocean is the largest water reservoir on Earth, and its water storage capacity accounts for about 96.5% of the world's total water storage capacity. Direct electrolysis of seawater to produce hydrogen does not produce harmful gases such as carbon dioxide, and is a zero-emission clean energy production method. Therefore, a multifunctional semiconductor catalyst that can efficiently precipitate hydrogen in a universal medium and in alkaline seawater has become the focus of many researchers.

[0003] Transition metal phosphides are considered to be very promising catalysts due to their large theoretical capacity, low HER overpotential, and high chemical stability. Their unique charged structure (metals carry positive charges and phosphorus carries negative charges) promotes phosphorus atoms to capture H + , and act as active sites to accelerate the dissociation of hydrogen, thereby accelerating the reaction process (see: DOI:10.1007 / s10853-023-08423-5). In addition, due to the synergistic effect, bimetallic phosphides often exhibit better catalytic performance than single metal phosphides.

[0004] Compared with traditional regular crystalline phase materials, amorphous materials have a larger proportion of randomly oriented bonds and unsaturated electronic configurations, which gives them better reactant adsorption, and the flexibility of the local amorphous phase structure can accelerate the charge transfer between active sites and intermediates. In addition, the unique amorphous materials have long-range disorder and a few atomic short-range order characteristics, and the rich surface defects and unsaturated coordination promote the generation of more active sites, thereby enhancing the electrocatalytic activity. Amorphous materials can not only be used in the direction of electrocatalysis, but also have a variety of applications in photothermal conversion and optoelectronics due to their good chemical corrosion resistance and permeability resistance. For example, the literature (see: DOI: 10.1002 / adma.202301684) uses amorphous / crystal interface engineering to prepare metal halide perovskite solar cells, opening up a new path for the next generation of photovoltaic technology. In contrast, although crystalline materials have high conductivity, due to the lack of sufficient reactive active sites, the catalytic effect cannot achieve the best results. Therefore, it is exciting to design a material with a unique amorphous / crystal structure combining the advantages of both. On the one hand, the uneven charge distribution at the amorphous / crystal interface leads to the formation of an internal electric field, which in turn promotes efficient charge separation. For example, the literature (see: DOI: 10.1016 / j.cej.2023.143252) synthesized a CoPi / ZnIn2S4 / aB-TiO2 photoelectrocatalytic material. The incorporation of non-metallic B and the formation of amorphous / crystal heterojunctions regulate the band structure of the catalyst, enhance its internal electric field, and improve the charge distribution. On the other hand, the active sites exposed at the amorphous / crystal interface are more powerful for the adsorption / desorption of intermediates, thereby showing higher catalytic activity (see: DOI: 10.1039 / d2ta09035j).

[0005] The performance of a material depends largely on its size and shape. A specific size and shape can have a high surface area, thereby exposing more active sites, increasing the contact area between the electrolyte and the catalyst, and increasing the mass transfer rate. One-dimensional nanowires expose more active sites. Chinese patent document CN 118241250 A discloses a Pt / NiCoP for electrocatalytic nitrate reduction. Thanks to the nanowire array of the catalyst, it has a large specific surface area, more exposed active sites, and improved NH3 production efficiency. Two-dimensional nanosheets can accelerate electron transfer. Chinese patent document CN 109961963 A discloses a NiCoP-CoP regular hexagonal micron sheet capacitor material and preparation method, which has good specific capacitance. However, the reaction time is too long. Starting from green energy saving and environmental protection, this patent invents a preparation method with shorter hydrothermal time. The three-dimensional nanoflower catalyst combines the advantages of the above two different structures and also enhances mechanical stability, maximizing the overall activity without expanding the total area (see: DOI:10.1002 / smll.202301610). Chinese patent document CN116180134 A discloses a nitrogen-doped carbon nanoflower-loaded CoP / NiCoP heterostructure. Although both of them form a three-dimensional nanoflower structure, there are great differences between them: 1. The hydrothermal time of the patent is not applicable to the present patent and is not within the protection scope of the patent; 2. Methanol is used as a solvent in the preparation process of the patent, which lacks the concept of green environmental protection compared with the present patent that only uses water; 3. The overall raw materials of the patent and the present patent are different, and the catalysts generated by phosphating are also different, and the phosphating methods of the two patents are also different, and the phosphating time is not within the protection scope of the patent. The former step is the basis of the latter step and is inseparable; 4. The catalyst prepared by the patent is only It is only used for alkaline hydrogen evolution reaction, and the continuous hydrogen evolution time is very short. Compared with the application scope of this patent (this patent can be applied to alkaline hydrogen evolution, alkaline complete water splitting, acidic hydrogen evolution, alkaline seawater hydrogen evolution), the application scope is extremely narrow; 5. The catalyst of this patent is a powder that needs to be adhered to the glassy carbon electrode with a binder. During the catalytic process, the catalyst is easily detached, resulting in unstable performance. The self-supporting system prepared by this patent has successfully and cleverly solved the above problems; 6. This patent uses phosphating to obtain a crystalline heterojunction. This patent combines the characteristics of crystals and amorphous materials, and uses hydrothermal method and low-temperature phosphating method to obtain an amorphous / crystalline NiCoP / NF electrocatalyst.

[0006] In summary, amorphous / crystalline materials are widely used, and there are still few research patents on amorphous / crystalline bimetallic phosphides that can construct unique structures. Amorphous / crystalline bimetallic phosphides that can be applied to general media and real seawater and have high stability are even less reported. Chinese patent document CN 118308753 A discloses a method for preparing a Ni2P-NiFeBP heterojunction catalyst, which is used for electrolysis of urea to produce hydrogen. The preparation process is complicated and cannot meet the wide range requirements of hydrogen production from general media and alkaline seawater. Therefore, the invention of a new amorphous / crystalline bimetallic phosphide electrocatalyst that can simultaneously meet the requirements of hydrogen evolution in acid / alkaline water electrolysis, hydrogen evolution in alkaline seawater, and efficient catalytic kinetics has potential application value in the fields of hydrogen energy development and environmental protection. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a self-supporting amorphous / crystalline NiCoP / NF multi-level structure electrocatalyst and its preparation method and application. The preparation method of the amorphous / crystalline NiCoP / NF electrocatalyst of the present invention is simple, has high efficiency and safety performance, and is low in price.

[0008] The technical solution of the present invention is as follows: A self-supporting amorphous / crystalline NiCoP / NF multi-level structure nanomaterial, wherein the microscopic morphology of the NiCoP / NF multi-level structure nanomaterial is a three-dimensional nanoflower of 5-6 μm, wherein the three-dimensional nanoflower is assembled from two-dimensional nanosheets of 4-5 μm, and the two-dimensional nanosheets are woven from one-dimensional nanowires with a diameter of 100-200 nm.

[0009] The method for preparing the above-mentioned amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower material comprises the following steps: (1) dissolving nickel nitrate hexahydrate, cobalt nitrate hexahydrate, urea and ammonium fluoride in ultrapure water, stirring until completely dissolved, adding the pretreated nickel foam, and performing a hydrothermal reaction; separating, washing, and drying to obtain a nickel foam material loaded with a nickel-cobalt precursor; The pretreatment process is as follows: ultrasonically treating the nickel foam in hydrochloric acid, ethanol and ultrapure water respectively, and vacuum drying to obtain the pretreated nickel foam; (2) The nickel-cobalt precursor foam nickel material and sodium hypophosphite monohydrate are placed in two porcelain boats respectively; the sodium hypophosphite monohydrate is close to the gas inlet end of the tubular furnace, and the nickel-cobalt precursor foam nickel material is close to the gas outlet end of the protective gas. Under the protective gas atmosphere, the amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower material is obtained by calcining.

[0010] Preferably, in step (1), the molar ratio of nickel nitrate hexahydrate, cobalt nitrate hexahydrate, urea and ammonium fluoride is 1:2:10:3; the stirring speed is 1000 rpm and the stirring time is 30 min.

[0011] According to the preferred embodiment of the present invention, in step (1), the pretreatment process is: a 0.5-2 mm thick, 1×2 cm 2 The foamed nickel was ultrasonically treated in 3 M hydrochloric acid, ethanol and ultrapure water for 10-30 min respectively and vacuum dried to obtain the pretreated foamed nickel.

[0012] Preferably, in step (1), the hydrothermal reaction temperature is 120°C, the hydrothermal time is 2-12 h, and the hydrothermal time is more preferably 6 h; the vacuum drying temperature is 40-60°C, the drying time is 2-20 h, and more preferably the drying temperature is 60°C, and the drying time is 12 h.

[0013] Preferably, according to the present invention, the mass ratio of sodium hypophosphite monohydrate in step (2) to nickel nitrate hexahydrate in step (1) is 20:2.91; and the protective gas is nitrogen or argon.

[0014] Preferably, according to the present invention, in step (2), after the nickel-cobalt precursor foam nickel material and sodium hypophosphite monohydrate are respectively placed in a tubular furnace, the tubular furnace is vacuumed 2-4 times, and then a protective gas is introduced.

[0015] Preferably, in step (2), during the calcination process, the gas is continuously introduced into the tubular furnace, the gas outlet of the tubular furnace is connected to the tail gas absorption liquid through a pipeline, and the bubble rate of the gas discharged from the pipeline in the tail gas absorption liquid is 1 / (1-3) s.

[0016] According to the preferred embodiment of the present invention, in step (2), the calcination conditions are: heating rate 1-5 °C min -1 The calcination temperature is 300-400 °C, the holding time is 0.5-3 h, and the heating rate is preferably 2 °C min -1 The calcination temperature is 300 °C and the holding time is 2 h.

[0017] The present invention also provides the application of the above-mentioned amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflowers as an electrocatalyst in alkaline or acidic water electrolysis hydrogen evolution reaction (HER), and alkaline electrolysis of seawater for hydrogen evolution.

[0018] The present invention adopts a simple one-step hydrothermal method to prepare a nickel-cobalt precursor foam nickel material, and then uses low-temperature phosphating to prepare a multi-level three-dimensional structure electrocatalyst with a combination of amorphous / crystalline, which can be applied to hydrogen evolution in a variety of electrolytes (acidic, alkaline, alkaline seawater).

[0019] In the preparation method of the present invention, the phosphating temperature is relatively important. By controlling the phosphating temperature, target products with different crystal strengths and significantly different performances can be obtained. For example, when the temperature is 300 ° C, the HER performance of amorphous / crystalline NiCoP / NF is the best. As the temperature increases, the crystal strength of NiCoP / NF increases, but the HER performance is inversely proportional to it. Therefore, a suitable phosphating temperature can obtain NiCoP / NF with the best amorphous / crystalline phase ratio, which can maximize the electrocatalytic performance, so controlling the phosphating temperature is the key to the present invention.

[0020] Technical features and beneficial effects of the present invention: 1. The raw materials of the present invention are all cheap, non-precious metals with rich energy storage, and the preparation process is simple, easy to operate, and has a high repetition rate. The whole process only uses water as a solvent, without the participation of organic solvents, which conforms to the concept of green environmental protection.

[0021] 2. The present invention prepares excellent self-supporting amorphous / crystalline electrode materials with a self-supporting system, does not rely on binders such as Nafion, and will not cause the catalyst to fall off during the catalytic process, resulting in unstable performance.

[0022] 3. The catalyst prepared by the present invention can be used under a variety of electrolytes, that is, it can be used in acidic or alkaline water electrolysis to produce hydrogen, and can also be used for alkaline seawater to produce hydrogen; under different acidic or alkaline conditions, it not only exhibits excellent HER catalytic activity, but also the dual-electrode system composed of RuO2 in alkaline medium has excellent complete water splitting function; at the same time, it also achieves long-term stability at high current density in alkaline seawater.

[0023] 4. The materials of the present invention are used as electrocatalysts for HER: In 1 M KOH, when the current density reaches 10 mAcm -2 , 100 mA cm -2 , 300 mA cm -2 When the current density reaches 10 mA cm -2 , 100 mA cm -2 , 200 mA cm -2When the current density is 100 mA cm-1, the overpotential of HER is only 152 mV, 231 mV and 268 mV respectively. -2 The catalyst material of the present invention is of great significance for reducing the overpotential of water electrolysis reaction, realizing low-energy consumption hydrogen production, improving the natural environment and utilizing seawater resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope (SEM) image of the nickel-cobalt precursor (Comparative Example 6) of the present invention; Figure 2 The X-ray diffraction (XRD) pattern of the catalyst material prepared in Example 1 of the present invention; Figure 3 This is a scanning electron microscope (SEM) image of the catalyst material prepared in Example 1 of the present invention; Figure 4 The transmission electron microscope (TEM) spectrum of the catalyst material prepared in Example 1 of the present invention; Figure 5 A high resolution transmission electron microscope (HRTEM) spectrum of the catalyst material prepared in Example 1 of the present invention; Figure 6 A high angle annular dark field scanning transmission electron microscope (HAADF-STEM) and corresponding element mapping diagram of the catalyst material prepared in Example 1 of the present invention; Figure 7 The X-ray diffraction (XRD) pattern of the catalyst material prepared in Example 2 of the present invention; Figure 8 The X-ray diffraction (XRD) pattern of the catalyst material prepared in Comparative Example 1 of the present invention; Fig. 9 The X-ray diffraction (XRD) pattern of the catalyst material prepared in Comparative Example 2 of the present invention; Fig.10 Alkaline HER linear sweep voltammetry (LSV) polarization curves of the catalyst materials prepared in Examples 1-5 and Comparative Examples 1-8 of the present invention; Fig.11 X-ray diffraction (XRD) comparison patterns of the catalyst materials prepared in Examples 1-2 of the present invention and Comparative Example 1; Fig.12 This is a stability diagram of the alkaline HER of the catalyst material prepared in Example 1 of the present invention; Fig.13 The linear sweep voltammetry (LSV) polarization curve of the catalyst material prepared by Example 1 of the present invention and RuO2 for alkaline water splitting; Fig.14The alkaline water splitting stability diagram of the catalyst material prepared by Example 1 of the present invention and RuO2; Fig.15 Acidic HER linear sweep voltammetry (LSV) polarization curves of the catalyst materials prepared in Examples 1-5 and Comparative Examples 1-8 of the present invention; Fig.16 A diagram showing the stability of the acidic HER of the catalyst material prepared in Example 1 of the present invention; Fig.17 HER linear sweep voltammetry (LSV) polarization curve of the catalyst prepared in Example 1 of the present invention in simulated seawater and real seawater; Fig.18 This is a stability diagram of the catalyst prepared in Example 1 of the present invention in real seawater. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0026] Meanwhile, the experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents, materials and devices described are all commercially available unless otherwise specified.

[0027] Example 1 A method for preparing a self-supporting amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower material, comprising the following steps: (1) Cut the 0.5 mm thick and 1×2 cm 2 The nickel foam was ultrasonically treated with 3 M hydrochloric acid, ethanol and ultrapure water for 20 min each to remove the oxide layer on the surface of the nickel foam, and then placed in a vacuum drying oven at 60 °C for 6 h to obtain the treated nickel foam.

[0028] (2) Take 1 mmol of nickel nitrate hexahydrate, 2 mmol of cobalt nitrate hexahydrate, 10 mmol of urea and 3 mmol of ammonium fluoride and add them to 30 mL of ultrapure water. Stir at 1000 rpm for 30 min. After complete dissolution, a pink clear solution is obtained.

[0029] (3) The pink clear solution obtained in step (2) is placed in a reactor, and the nickel foam (NF) treated in step (1) is immersed in the solution as a catalyst self-supporting carrier, followed by a hydrothermal reaction at 120°C for 6 h to obtain a nickel foam loaded with a nickel-cobalt precursor. After cooling to room temperature, the nickel foam is taken out, and washed with ultrapure water and anhydrous ethanol in turn, and dried in a vacuum drying oven at 60°C for 12 h to obtain a nickel-cobalt precursor nickel foam material.

[0030] The scanning electron microscope (SEM) image of the prepared nickel-cobalt precursor is shown in Figure 1 As shown in the figure, the prepared precursor is a three-dimensional nanoflower with a radius of about 5-6 μm, in which the nanoflower is self-assembled from nanosheets with a width of about 4-5 μm, and the nanosheets are woven from nanowires with a diameter of about 100-200 nm. The surface of the obtained three-dimensional nanoflower is flat and smooth.

[0031] (4) Place the nickel-cobalt precursor nickel foam material obtained in step (3) into an independent porcelain boat, and place 2 g of sodium hypophosphite monohydrate in another independent porcelain boat. Place the two porcelain boats into the tubular furnace in the order of placing the porcelain boat of sodium hypophosphite monohydrate at the air inlet of the tubular furnace and the porcelain boat of the nickel-cobalt precursor nickel foam material at the air outlet, and evacuate the tubular furnace three times in succession to remove the air in the tubular furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tubular furnace; the outlet end of the tubular furnace is connected to the tail gas absorption liquid, and the bubble rate generated in the tail gas absorption liquid is 1 / 3 s. Set the temperature rise program of the tubular furnace at 2°C min -1 The temperature was raised to 300 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0032] The X-ray diffraction pattern (XRD) of the final product (NiCoP-300, the numbers represent different phosphating temperatures) prepared in Example 1 is as follows: Figure 2 In addition to the typical diffraction peaks attributed to nickel foam (JCPDS: 70-1849), the diffraction peaks at 40.99°, 47.58°, 54.74°, 55.33° and 75.41° are respectively attributed to the (111), (210), (002), (211) and (212) crystal planes of NiCoP (JCPDS: 71-2336), and no impurity peaks appear, indicating that the material was successfully prepared.

[0033] The scanning electron microscope (SEM) of the catalyst material prepared in this Example 1 is as follows Figure 3 As shown, Figure 4 is the transmission electron microscope (TEM) of Example 1, Figure 5 For high-resolution transmission electron microscopy (HRTEM), Figure 6 High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and the corresponding elemental mapping. Figure 3 It can be seen that the overall morphology of the NiCoP / NF obtained after phosphating is completely consistent with that of the nickel-cobalt precursor. The three-dimensional nanoflowers grow evenly on the nickel foam, and the surface remains flat and smooth, indicating that the phosphating is successful. Figure 4 It is clearly shown that many vesicles are formed on the smooth and flat one-dimensional nanowire surface of the prepared catalyst after phosphating, which is due to dehydration and gas release occurring during the phosphating process. Figure 5HRTEM images show that NiCoP is composed of amorphous and crystalline images, and there is a clear lattice fringe on the (111) crystal plane of NiCoP with a spacing of 0.220 nm ( Figure 5 a). In the corresponding selected area fast Fourier transform (FFT) mode, the bright spot ( Figure 5 a) and diffusion ring ( Figure 5 b) further supports this point. In addition, Figure 5 The inverse FFT image in c clearly confirms the coexistence of crystalline and amorphous phases in NiCoP. Figure 6 The high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and corresponding elemental mapping of NiCoP are shown, showing that the Ni, Co and P elements are evenly distributed in the sample. This multi-stage catalyst with a suitable amorphous / crystalline phase ratio provides more abundant unsaturated active sites, thereby enhancing the adsorption / desorption of intermediates and improving the HER reaction kinetics of the catalyst.

[0034] Example 2 A method for preparing a self-supporting amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower material, comprising the following steps: The preparation steps (1) to (3) of the nickel-cobalt precursor nickel foam material are the same as those in Example 1.

[0035] (4) Place the nickel-cobalt precursor nickel foam material in an independent porcelain boat, and place 2 g of sodium hypophosphite monohydrate in another independent porcelain boat. Place the two porcelain boats in the order of placing the sodium hypophosphite monohydrate boat at the air inlet of the tube furnace and the nickel-cobalt precursor nickel foam material boat at the air outlet. Vacuum the tube furnace three times continuously to remove the air in the tube furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tube furnace; the outlet end of the tube furnace is connected to the exhaust gas absorption liquid, and the bubble rate generated in the exhaust gas absorption liquid is 1 / 3s. Set the temperature rise program of the tube furnace at 2 ℃ min -1 The temperature was raised to 400 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0036] The X-ray diffraction pattern (XRD) of the final product prepared in Example 2 is as follows: Figure 7 As shown. In addition to the typical diffraction peaks attributed to nickel foam (JCPDS: 70-1849), the diffraction peaks at 40.99°, 47.58°, 54.74°, 55.33° and 75.41° are respectively attributed to the (111), (210), (002), (211) and (212) crystal planes of NiCoP (JCPDS: 71-2336). As the phosphating temperature increases, the intensity of the diffraction peaks increases significantly, indicating that the crystallinity is enhanced compared to Example 1. No impurity peaks appear, indicating that the material was successfully prepared.

[0037] Example 3 A method for preparing a self-supporting amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower material, comprising the following steps: The preparation of the pretreated nickel foam in step (1) and the pink clarified solution in step (2) is the same as in Example 1.

[0038] (3) The pink clear solution obtained in step (2) is placed in a reactor, and the NF treated in step (1) is immersed in the solution as a catalyst self-supporting carrier, followed by a hydrothermal reaction at 120°C for 2 h to obtain a nickel foam loaded with a nickel-cobalt precursor. After cooling to room temperature, the nickel foam is taken out, and washed with ultrapure water and anhydrous ethanol in turn, and dried in a vacuum drying oven at 60°C for 12 h to obtain a nickel-cobalt precursor nickel foam material.

[0039] (4) Place the nickel-cobalt precursor nickel foam material obtained in step (3) into an independent porcelain boat, and place 2 g of sodium hypophosphite monohydrate in another independent porcelain boat. Place the two porcelain boats in the order of placing the porcelain boat of sodium hypophosphite monohydrate at the air inlet of the tubular furnace and the porcelain boat of the nickel-cobalt precursor nickel foam material at the air outlet, and evacuate the tubular furnace three times in succession to remove the air in the tubular furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tubular furnace; the outlet end of the tubular furnace is connected to the tail gas absorption liquid, and the bubble rate generated in the tail gas absorption liquid is 1 / 3s. Set the temperature rise program of the tubular furnace at 2 ℃min -1 The temperature was raised to 300 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0040] Example 4 A method for preparing a self-supporting amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower material, comprising the following steps: The preparation of the pretreated nickel foam in step (1) and the pink clarified solution in step (2) is the same as in Example 1.

[0041] (3) The pink clear solution obtained in step (2) is placed in a reactor, and the NF treated in step (1) is immersed in the solution as a catalyst self-supporting carrier, followed by a hydrothermal reaction at 120°C for 10 h to obtain a nickel foam loaded with a nickel-cobalt precursor. After cooling to room temperature, the nickel foam is taken out, and washed with ultrapure water and anhydrous ethanol in turn, and dried in a vacuum drying oven at 60°C for 12 h to obtain a nickel-cobalt precursor nickel foam material.

[0042] (4) Place the nickel-cobalt precursor nickel foam material obtained in step (3) into an independent porcelain boat, and place 2 g of sodium hypophosphite monohydrate in another independent porcelain boat. Place the two porcelain boats into the tubular furnace in the order of placing the porcelain boat of sodium hypophosphite monohydrate at the air inlet of the tubular furnace and the porcelain boat of the nickel-cobalt precursor nickel foam material at the air outlet, and evacuate the tubular furnace three times in succession to remove the air in the tubular furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tubular furnace; the outlet end of the tubular furnace is connected to the tail gas absorption liquid, and the bubble rate generated in the tail gas absorption liquid is 1 / 3s. Set the temperature rise program of the tubular furnace at 2 ℃min -1 The temperature was raised to 300 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0043] Example 5 A method for preparing a self-supporting amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower material, comprising the following steps: The preparation of the pretreated nickel foam in step (1) and the pink clarified solution in step (2) is the same as in Example 1.

[0044] (3) The pink clear solution obtained in step (2) is placed in a reactor, and the NF treated in step (1) is immersed in the solution as a catalyst self-supporting carrier, followed by a hydrothermal reaction at 120°C for 12 h to obtain a nickel foam loaded with a nickel-cobalt precursor. After cooling to room temperature, the nickel foam is taken out, and washed with ultrapure water and anhydrous ethanol in turn, and dried in a vacuum drying oven at 60°C for 12 h to obtain a nickel-cobalt precursor nickel foam material.

[0045] (4) Place the nickel-cobalt precursor nickel foam material obtained in step (3) into an independent porcelain boat, and place 2 g of sodium hypophosphite monohydrate in another independent porcelain boat. Place the two porcelain boats into the tubular furnace in the order of placing the porcelain boat of sodium hypophosphite monohydrate at the air inlet of the tubular furnace and the porcelain boat of the nickel-cobalt precursor nickel foam material at the air outlet, and evacuate the tubular furnace three times in succession to remove the air in the tubular furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tubular furnace; the outlet end of the tubular furnace is connected to the tail gas absorption liquid, and the bubble rate generated in the tail gas absorption liquid is 1 / 3s. Set the temperature rise program of the tubular furnace at 2 ℃min -1 The temperature was raised to 300 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0046] Comparative Example 1 The preparation steps (1) to (3) of the nickel-cobalt precursor nickel foam material are the same as those in Example 1.

[0047] (4) Place the obtained nickel-cobalt precursor nickel foam material into an independent porcelain boat, and place 2g of sodium hypophosphite monohydrate in another independent porcelain boat. Place the two porcelain boats into the tubular furnace in the order of placing the porcelain boat of sodium hypophosphite monohydrate at the air inlet of the tubular furnace and the porcelain boat of nickel-cobalt precursor nickel foam material at the air outlet, and evacuate the tubular furnace three times in succession to remove the air in the tubular furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tubular furnace; the outlet end of the tubular furnace is connected to the exhaust gas absorption liquid, and the bubble rate generated in the exhaust gas absorption liquid is 1 / 3s. Set the temperature rise program of the tubular furnace at 2 ℃ min -1 The temperature was raised to 500 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0048] The X-ray diffraction pattern (XRD) of the final product prepared in this comparative example 1 is as follows: Figure 8 As shown. In addition to the typical diffraction peaks attributed to nickel foam (JCPDS: 70-1849), the diffraction peaks at 40.99°, 47.58°, 54.74°, 55.33° and 75.41° are respectively attributed to the (111), (210), (002), (211) and (212) crystal planes of NiCoP (JCPDS: 71-2336), and no impurity peaks appear, indicating that the material is successfully prepared. With the increase of phosphating temperature, the intensity of the diffraction peak increases significantly, indicating that the crystallinity is enhanced compared with Example 2. Although the increase of phosphating temperature significantly enhances the crystallinity of NiCoP / NF, the HER performance is inversely proportional to the crystallinity of the catalyst. This shows that the optimal ratio of amorphous phase and crystalline phase has faster electrolyte diffusion capacity and more electrocatalytic active sites, thereby accelerating the HER catalytic reaction kinetics.

[0049] Comparative Example 2 The preparation steps (1) to (3) of the nickel-cobalt precursor nickel foam material are the same as those in Example 1.

[0050] (4) Place the obtained nickel-cobalt precursor nickel foam material into an independent porcelain boat, and place 2g of sodium hypophosphite monohydrate in another independent porcelain boat. Place the two porcelain boats into the tubular furnace in the order of placing the porcelain boat of sodium hypophosphite monohydrate at the air inlet of the tubular furnace and the porcelain boat of nickel-cobalt precursor nickel foam material at the air outlet, and evacuate the tubular furnace three times in succession to remove the air in the tubular furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tubular furnace; the outlet end of the tubular furnace is connected to the exhaust gas absorption liquid, and the bubble rate generated in the exhaust gas absorption liquid is 1 / 3s. Set the temperature rise program of the tubular furnace at 2 ℃ min -1 The temperature was raised to 250 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0051] The X-ray diffraction pattern (XRD) of the final product prepared in this comparative example 2 is as follows: Fig. 9 In addition to the typical diffraction peaks belonging to nickel foam (JCPDS: 70-1849), no diffraction peaks consistent with NiCoP appear, indicating that when the phosphating temperature is 250°C, amorphous / crystalline NiCoP / NF cannot be generated.

[0052] Comparative Example 3 The preparation steps (1) to (3) of the nickel-cobalt precursor nickel foam material are the same as those in Example 1.

[0053] (4) The obtained nickel-cobalt precursor nickel foam material was placed in an independent porcelain boat and heated in a tube furnace under air atmosphere at 2 °C min -1 The temperature was raised to 300 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0054] Comparative Example 4 (1) The preparation of treated nickel foam is the same as in Example 1.

[0055] (2) Take 3 mmol of nickel nitrate hexahydrate, 10 mmol of urea and 3 mmol of ammonium fluoride and add them to 30 mL of ultrapure water. Stir at 1000 rpm for 30 min until they are completely dissolved to obtain a pink clear solution.

[0056] (3) The pink clear solution obtained in step (2) is placed in a reactor, and the NF treated in step (1) is immersed in the solution as a self-supporting catalyst carrier, followed by a hydrothermal reaction at 120°C for 6 h to obtain a nickel foam loaded with a nickel precursor. After cooling to room temperature, the nickel foam is taken out, and washed with ultrapure water and anhydrous ethanol in turn, and dried in a vacuum drying oven at 60°C for 12 h to obtain a nickel precursor nickel foam material.

[0057] (4) Place the nickel precursor foam nickel material obtained in step (3) into an independent porcelain boat, and place 2 g of sodium hypophosphite monohydrate in another independent porcelain boat. Place the two porcelain boats into the tubular furnace in the order of placing the porcelain boat of sodium hypophosphite monohydrate at the air inlet of the tubular furnace and the porcelain boat of the nickel precursor foam nickel material at the air outlet, and evacuate the tubular furnace three times in succession to remove the air in the tubular furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tubular furnace; the outlet end of the tubular furnace is connected to the tail gas absorption liquid, and the bubble rate generated in the tail gas absorption liquid is 1 / 3s. Set the temperature rise program of the tubular furnace at 2 ℃ min -1 The temperature was raised to 300 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0058] Comparative Example 5 (1) The preparation of treated nickel foam is the same as in Example 1.

[0059] (2) Take 3 mmol of cobalt nitrate hexahydrate, 10 mmol of urea and 3 mmol of ammonium fluoride and add them to 30 mL of ultrapure water. Stir at 1000 rpm for 30 min until they are completely dissolved to obtain a pink clear solution.

[0060] (3) The pink clear solution obtained in step (2) is placed in a reactor, and the NF treated in step (1) is immersed in the solution as a self-supporting catalyst carrier, followed by a hydrothermal reaction at 120°C for 6 h to obtain a nickel foam loaded with a cobalt precursor. After cooling to room temperature, the nickel foam is taken out, and washed with ultrapure water and anhydrous ethanol in turn, and dried in a vacuum drying oven at 60°C for 12 h to obtain a cobalt precursor nickel foam material.

[0061] (4) Place the cobalt precursor nickel foam material obtained in step (3) into an independent porcelain boat, and place 2 g of sodium hypophosphite monohydrate in another independent porcelain boat. Place the two porcelain boats in the order of placing the porcelain boat of sodium hypophosphite monohydrate at the air inlet of the tubular furnace and the porcelain boat of the cobalt precursor nickel foam material at the air outlet, and evacuate the tubular furnace three times in succession to remove the air in the tubular furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tubular furnace; the outlet end of the tubular furnace is connected to the tail gas absorption liquid, and the bubble rate generated in the tail gas absorption liquid is 1 / 3s. Set the temperature rise program of the tubular furnace at 2 ℃min -1 The temperature was raised to 300 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0062] Comparative Example 6 (1) The preparation of treated nickel foam is the same as in Example 1.

[0063] (2) Take 1 mmol nickel nitrate hexahydrate, 2 mmol cobalt nitrate hexahydrate, 10 mmol urea and 3 mmol ammonium fluoride and add them to 30 mL of ultrapure water. Stir at 1000 rpm for 30 min until they are completely dissolved to obtain a pink clear solution.

[0064] (3) The pink clear solution obtained in step (2) is placed in a reactor, and the NF treated in step (1) is immersed in the solution as a self-supporting catalyst carrier, followed by a hydrothermal reaction at 120°C for 6 h to obtain a nickel foam loaded with a nickel-cobalt precursor. After cooling to room temperature, the nickel foam is taken out, and washed with ultrapure water and anhydrous ethanol in turn, and dried in a vacuum drying oven at 60°C for 12 h to obtain a nickel-cobalt precursor nickel foam material.

[0065] Comparative Example 7 (1) Take 1 mmol nickel nitrate hexahydrate, 2 mmol cobalt nitrate hexahydrate, 10 mmol urea and 3 mmol ammonium fluoride and add them to 30 mL ultrapure water. Stir at 1000 rpm for 30 min until they are completely dissolved to obtain a pink clear solution.

[0066] (2) The pink clear solution obtained in step (1) was placed in a reactor and subjected to hydrothermal reaction at 120°C for 6 h. After cooling to room temperature, the solution was centrifuged, washed, and dried in a vacuum drying oven at 60°C for 12 h to obtain a nickel-cobalt precursor powder.

[0067] (3) Take 50 mg of the nickel-cobalt precursor powder obtained in step (2) and put it into one end of a porcelain boat, and put 500 mg of sodium hypophosphite monohydrate at the other end. Place the porcelain boat into the tube furnace in the order of placing one end of the sodium hypophosphite monohydrate at the air inlet of the tube furnace and one end of the nickel-cobalt precursor powder at the air outlet. Vacuum the tube furnace three times continuously to remove the air in the tube furnace; then introduce nitrogen. Nitrogen is continuously introduced into the tube furnace; the outlet end of the tube furnace is connected to the exhaust gas absorption liquid, and the bubble rate generated in the exhaust gas absorption liquid is 1 / 3s. Set the temperature rise program of the tube furnace at 2 ℃ min -1 The temperature was raised to 300 °C at a rate of 100 °C and kept at this temperature for 2 h. After cooling to room temperature, the porcelain boat was taken out to obtain a black final product.

[0068] Comparative Example 8 (1) Cut the nickel foam (thickness 0.5 mm, area 1×2 cm) 2 ) was ultrasonically treated with 3 M hydrochloric acid, ethanol and ultrapure water for 20 min each to remove the oxide layer on the surface of the nickel foam, and then dried in a vacuum drying oven at 60 °C for 6 h to obtain the treated blank nickel foam.

[0069] Test Example 1 The electrochemical alkaline hydrogen evolution performance test was performed on the catalysts prepared in Examples 1-5 and Comparative Examples 1-8. The specific test method is as follows.

[0070] LSV test method for electrocatalyst HER: A three-electrode system is used, with the prepared catalyst as the working electrode, the graphite rod as the counter electrode, and the Hg / HgO electrode as the reference electrode. The electrolyte uses KOH with a concentration of 1 M. Among them, comparative example 7 is a powder catalyst, which needs to be equipped with ink and dripped on the glassy carbon electrode as a working electrode for testing. The specific operation is as follows: 7 mg of sample and 2 mg of XC-72 carbon black are dispersed in a mixed solution of 0.75 mL of isopropanol and 0.25 mL of Nafion, and the resulting mixture is ultrasonically treated for 40 min to obtain a uniform ink, and then 10 μL of the solution is dripped on the glassy carbon electrode and vacuum dried for 10 h to obtain the desired working electrode.

[0071] Fig.10 The LSV diagrams of the alkaline HER of the electrocatalysts obtained in Examples 1-5 and Comparative Examples 1-8 are shown in Table 1. It is worth noting that the HER performance of the catalytic material prepared in Example 1 is better than that of the other examples and comparative examples. Due to the strong lattice strain at the amorphous / crystalline interface, the active sites of HER are significantly increased, thereby accelerating the HER reaction kinetics. Although the increase in phosphating temperature significantly enhances the crystallinity of NiCoP / NF ( Fig.11 ), but the HER performance is inversely proportional to the crystallinity of the catalyst. This shows that the optimal ratio of amorphous phase and crystalline phase has faster electrolyte diffusion capacity and more electrocatalytic active sites, thereby accelerating the HER catalytic reaction kinetics. In addition, by controlling the hydrothermal time, a nickel-cobalt precursor-loaded nickel foam material is obtained. At the same phosphating temperature, Example 1, i.e., the hydrothermal time is 6 h, has the best HER performance, indicating that the appropriate hydrothermal time is also one of the important factors for improving the reaction rate. The HER performance of the catalyst calcined in an air atmosphere is far inferior to that of the phosphated catalyst, which shows that the unique charged structure of the phosphide can more effectively capture H + , and act as active sites to accelerate the dissociation of hydrogen, thereby increasing the reaction rate. Therefore, the catalytic performance of phosphides is better than that of oxides. At the same time, under the same calcination conditions, the performance of monometallic phosphides is also lower than that of bimetallic phosphides, which shows that the synergistic effect of bimetallic is an important factor in promoting the HER reaction kinetics. Finally, it cannot be ignored that the HER performance of pure nickel foam and NiCoP powder is significantly reduced compared with NiCoP / NF. This is because the unique mechanical strength and porous structure of nickel foam combined with the unique three-dimensional nanoflower multi-level structure of NiCoP greatly increases the mass transfer efficiency of the electrolyte to a certain extent, thereby improving the HER efficiency. At the same time, the unique self-supporting structure of NiCoP / NF avoids the influence of the binder and the phenomenon of catalyst shedding caused by bubbles during the catalytic process. Experiments show that no matter which of the two substances is missing, the synthesized catalyst cannot achieve optimal performance. In particular, at a current density of 50 mA cm -2 When the overpotential of Example 1 is only 139 mV, the current density is 100 mA cm -2 When the overpotential is only 151 mV, the overpotential is only 151 mV. Furthermore, when the current density reaches 300 mA cm -2 The required overpotential is only 154 mV. Then the stability test of the catalyst prepared in Example 1 was carried out. Fig.12 As shown, at a current density of 50 mA cm -2 When , the prepared catalyst can stably evolve hydrogen at a voltage of 139 mV for 72 h without obvious performance degradation, indicating that Example 1 has significant alkaline HER stability.

[0072] Test Example 2 The electrochemical alkaline water splitting performance test of the catalyst prepared in Example 1 was carried out. The specific test method is as follows: Electrocatalyst alkaline water splitting performance test method: A two-electrode system is used, the prepared catalyst material and RuO2 are used as cathode hydrogen evolution and anode oxygen evolution electrodes, respectively, and the electrolyte is a 1 M KOH aqueous solution.

[0073] like Figure 13-14 As shown in the figure, the dual-electrode system composed of Example 1 and RuO2 has excellent performance as a whole for water decomposition. -1 When the overpotential of water splitting is 1.59 V, and at 10 mA cm -1 It can produce hydrogen stably and continuously for 24 h.

[0074] Test Example 3 The electrochemical acidic hydrogen evolution performance test was performed on the catalysts prepared in Examples 1-5 and Comparative Examples 1-8. The specific test method is as follows.

[0075] LSV test method of electrocatalyst HER: A three-electrode system is used, with the prepared catalyst as the working electrode, the graphite rod as the counter electrode, and the Hg2SO4 electrode as the reference electrode. The electrolyte uses H2SO4 with a concentration of 0.5 M. The working electrode preparation method of Comparative Example 7 refers to Experimental Example 1.

[0076] Fig.15 The LSV diagrams of the electrocatalysts obtained in Examples 1-5 and Comparative Examples 1-8 for acidic HER are shown. This is consistent with the excellent HER activity of Example 1 under alkaline conditions. This indicates that the bimetallic NiCoP / NF with a unique and suitable ratio of amorphous / crystalline phases is also highly suitable for acidic electrolytes for acidic hydrogen evolution. In particular, at a current density of 100 mA cm -2 When the overpotential of Example 1 is only 231 mV, the current density is 200 mA cm -2 When the overpotential is only 268 mV, the overpotential is only 268 mV. Furthermore, when the current density reaches 300 mA cm -2 When , the required overpotential is only 302 mV. Therefore, the catalyst prepared in Example 1 has the smallest overpotential and the highest electrocatalytic acidic HER activity. Fig.16 This is a stability test diagram of Example 1 in 0.5 M H2SO4. It can be seen intuitively that Example 1 can also continuously produce hydrogen for 72 hours under acidic electrolyte, and has high acidic HER stability.

[0077] Test Example 4 The catalyst prepared in Example 1 was tested for its hydrogen evolution performance in alkaline seawater. The specific testing method is as follows.

[0078] LSV test method for electrocatalyst HER: A three-electrode system is used, with the prepared catalyst as the working electrode, the graphite rod as the counter electrode, and the Hg / HgO electrode as the reference electrode. The electrolytes used are 1 M KOH+0.5 M NaCl (simulated seawater) and 1 M KOH+ sea water (real seawater).

[0079] like Figure 17-18 As shown, in Example 1, HER was carried out in simulated seawater and real seawater. When the current density was 100 mAcm -2 When the overpotential was 246 mV and 253 mV, the electrocatalyst prepared in Example 1 also showed good conductivity at a high current density of 100 mA cm -2 Hydrogen can be produced continuously for 26 hours. - It is highly corrosive to transition metal catalysts, which has an adverse effect on the efficiency and stability of the catalysts. However, the prepared catalyst did not show a continuous performance decline in the initial use, but stabilized after 21 hours, with the performance only declining by 10%. Therefore, the prepared catalyst also showed excellent performance and high efficiency and stability in seawater electrolysis hydrogen production.

[0080] This patent combines hydrothermal method and calcination phosphating process to successfully prepare a multi-level self-supporting three-dimensional nanoflower NiCoP / NF electrocatalyst with an appropriate amorphous / crystalline phase ratio. The catalyst exhibits excellent HER performance and high efficiency stability in both 1 M KOH and 0.5 M H2SO4 media, perfectly realizing efficient and convenient hydrogen production technology in universal media. Not only that, the dual-electrode system composed of the prepared catalyst and RuO2 achieves efficient full water decomposition in 1 M KOH, further improving the utilization rate of water. According to the above results, the catalyst with a strong synergistic effect between the amorphous / crystalline interface significantly improves the HER performance of Example 1. With the increase of phosphating temperature, the crystallinity of NiCoP / NF is significantly enhanced, but the HER performance is inversely proportional to the crystallinity, which shows that the reasonable ratio of amorphous phase to crystalline phase is the key to improving HER performance. In addition, the appropriate hydrothermal time is also one of the important factors to improve HER performance. In summary, this patent not only reduces the phosphating temperature, but also relatively shortens the hydrothermal time. It is more energy-saving and environmentally friendly in terms of process preparation. At the same time, this patent also proves that the HER performance of phosphides is better than that of oxides, and the synergistic effect between bimetallic phosphides is also the core factor in improving HER performance. Then the synergistic effect of nickel foam and synthetic catalysts was discussed. Finally, we applied the prepared catalyst to real seawater with high corrosiveness and ion complexity, and found that it not only has good HER activity, but also can be used at 100 mA cm -2 The hydrogen evolution continued for 26 h at the current density, showing extremely high stability and corrosion resistance. Therefore, the amorphous / crystalline multi-level NiCoP / NF self-supporting three-dimensional nanoflower electrocatalyst not only achieved efficient hydrogen production in universal media, but also showed excellent performance in seawater, truly achieving the goal of high-efficiency, wide-range and comprehensive application of electrocatalysts.

Claims

1. A self-supporting amorphous / crystalline NiCoP / NF multi-level structure nanomaterial, characterized in that: The microscopic morphology of the NiCoP / NF multi-level structure nanomaterial is a three-dimensional nanoflower of 5-6 μm, wherein the three-dimensional nanoflower is assembled from two-dimensional nanosheets of 4-5 μm, and the two-dimensional nanosheets are woven from one-dimensional nanowires with a diameter of 100-200 nm.

2. The method for preparing the amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower material according to claim 1, characterized in that: The following steps are involved: (1) Dissolving nickel nitrate hexahydrate, cobalt nitrate hexahydrate, urea and ammonium fluoride in ultrapure water, stirring until completely dissolved, adding pretreated nickel foam, and performing a hydrothermal reaction; separating, washing, and drying to obtain a nickel-cobalt precursor nickel foam material; The pretreatment process is as follows: ultrasonically treating the nickel foam in hydrochloric acid, ethanol and ultrapure water respectively, and vacuum drying to obtain the pretreated nickel foam; (2) The nickel-cobalt precursor foam nickel material and sodium hypophosphite monohydrate are placed in two porcelain boats respectively; the sodium hypophosphite monohydrate is close to the gas inlet end of the tubular furnace, and the nickel-cobalt precursor foam nickel material is close to the gas outlet end of the protective gas. Under the protective gas atmosphere, the amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower material is obtained by calcining.

3. The preparation method according to claim 2, characterized in that In the step (1), the molar ratio of nickel nitrate hexahydrate, cobalt nitrate hexahydrate, urea and ammonium fluoride is 1:2:10:3; the stirring speed is 1000 rpm, and the stirring time is 30 min.

4. The preparation method according to claim 2, characterized in that In the step (1), the pretreatment process is: a 0.5-2 mm thick, 1×2 cm 2 The nickel foam was ultrasonically treated in 3 M hydrochloric acid, ethanol and ultrapure water for 10-30 min respectively and vacuum dried to obtain the pretreated nickel foam.

5. The preparation method according to claim 2, characterized in that In the step (1), the hydrothermal reaction temperature is 120°C; the hydrothermal reaction time is 2-12 h, preferably, the hydrothermal time is 6 h; the vacuum drying temperature is 40-60°C, and the vacuum drying time is 2-20 h, preferably, the drying temperature is 60°C, and the drying time is 12 h.

6. The preparation method according to claim 2, characterized in that: The mass ratio of the sodium hypophosphite monohydrate in step (2) to the nickel nitrate hexahydrate in step (1) is 20:2.91; and the protective gas is nitrogen or argon.

7. The preparation method according to claim 2, characterized in that: In the step (2), after the nickel-cobalt precursor loaded with nickel foam and sodium hypophosphite monohydrate are respectively placed in a tubular furnace, the tubular furnace is evacuated 2-4 times, and then a protective gas is introduced.

8. The preparation method according to claim 2, characterized in that: In the step (2), during the calcination process, the gas is continuously introduced into the tubular furnace, and the gas outlet end of the tubular furnace is connected to the tail gas absorption liquid through a pipeline. The bubble rate of the gas discharged from the pipeline in the tail gas absorption liquid is 1 / (1-3) s.

9. The preparation method according to claim 2, characterized in that: In the step (2), the calcination conditions are: heating rate 1-5 ℃ min -1 The calcination temperature is 300-400 °C, the holding time is 0.5-3 h, and the heating rate is preferably 2 °C min -1 The calcination temperature is 300 °C and the holding time is 2 h.

10. Use of the self-supporting amorphous / crystalline NiCoP / NF multi-level structure nanomaterial as claimed in claim 1 or the amorphous / crystalline NiCoP / NF multi-level three-dimensional nanoflower obtained by the preparation method as claimed in any one of claims 2 to 9 as an electrocatalyst in alkaline or acidic water electrolysis hydrogen evolution reaction, and alkaline electrolysis of seawater hydrogen evolution.

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