A self-supporting bifunctional electrocatalytic material, its preparation method and application

Abstract

This disclosure relates to a self-supporting bifunctional electrocatalytic material, its preparation method, and its application. The electrocatalytic material comprises a three-dimensional composite material containing a three-dimensional Ni nanoframework and a NiMoFe nanoalloy layer coated on the three-dimensional Ni nanoframework. The electrocatalytic material of this disclosure achieves the advantages of both high catalytic activity and high stability in water electrolysis catalysis, and it also possesses bifunctionality, serving as both a hydrogen evolution electrode and an oxygen evolution electrode.

Description

Technical Field

[0001] This disclosure relates to the field of catalyst preparation technology, specifically to a self-supporting bifunctional electrocatalytic material, its preparation method, and its application. Background Technology

[0002] Developing clean and renewable energy sources is one of the effective ways to address global warming and the dwindling supply of fossil fuels. Converting solar and wind energy into transportable and storable chemical fuels is considered a highly feasible solution. Hydrogen, with its high gravimetric energy density, high abundance, and clean, pollution-free nature, is an excellent carrier of sustainable energy, and water splitting is an important method for producing high-purity hydrogen. To overcome the high energy barrier of the water splitting reaction, the electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) half-reactions need to be designed and optimized. Precious metals exhibit extremely high activity for water splitting, but their scarcity still greatly hinders their large-scale application. Therefore, developing abundant, inexpensive, efficient, and stable catalysts for HER and OER is of great significance and has a promising market prospect.

[0003] Transition metals are among the most widely used catalysts for water splitting in alkaline media. Nanomaterials of elemental metals suffer from poor electrochemical activity and stability due to size and surface electronic structure, further limiting their application in overall water splitting. Performance can be improved by adjusting the properties and structure of their active sites through alloying, coating, or compositing. For example, Ho et al. (Nano Energy, 2016, 27, 247-254) reported the application of nickel-molybdenum alloy nanomaterials in the hydrogen evolution reaction (HER). This catalyst exhibited excellent HER catalytic activity; however, the preparation process used 20% hydrogen gas at high temperatures, posing significant safety risks. Xv et al. (Adv. Mater. 2017, 29, 1605957) reported a nitrogen-doped carbon-coated nickel nanoparticle as a water electrolysis catalyst, but the high-temperature carbonization process at 800℃ resulted in high energy consumption, and the material exhibited a large hydrogen evolution overpotential. Zhou et al. (Chem. Eng. J. 2020, 394, 124977) reported a nickel-iron alloy based on nitrogen-doped carbon materials, which showed superior water splitting activity compared to single-element doped carbon composites, but the use of binders for the electrode also reduced the active surface area. It is evident that highly active self-supporting nanocatalytic materials are mostly prepared under complex and demanding conditions, while most commercially available nanocatalytic materials are in powder form, requiring polymer binders to form electrodes. This leads to a reduction in active surface area and charge transfer efficiency, resulting in higher overpotentials at high current densities and the possibility of delamination. Furthermore, in industrial applications, it is difficult to obtain bifunctional catalytic electrodes that combine high catalytic activity and high stability. Summary of the Invention

[0004] The purpose of this disclosure is to provide a self-supporting bifunctional electrocatalytic material, its preparation method and application. This electrocatalytic material has the advantages of both high catalytic activity and high stability, and it is bifunctional, serving as both a hydrogen evolution electrode and an oxygen evolution electrode.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a self-supporting bifunctional electrocatalytic material, the electrocatalytic material comprising a three-dimensional composite material, the three-dimensional composite material comprising a three-dimensional Ni nanoframework and a NiMoFe nanoalloy layer coated on the three-dimensional Ni nanoframework.

[0006] Optionally, the BET specific surface area of ​​the electrocatalytic material is 2.1–2.9 m². 2 / g, preferably 2.3~2.7m 2 / g; In the XRD pattern of the electrocatalytic material, there are characteristic peaks at 2θ of 37-40°, 40-43°, 44-47°, 55-60°, 70-74° and 75-80°; XPS analysis shows that the atomic content of Ni in the electrocatalytic material is 58-84%, the atomic content of Mo is 9-29% and the atomic content of Fe is 4-26%.

[0007] Optionally, the thickness of the NiMoFe nanoalloy layer is 10–50 nm.

[0008] Optionally, the electrocatalytic material further includes a conductive substrate, on which the three-dimensional composite material is coated; the conductive substrate is a flexible conductive substrate or a rigid conductive substrate; the flexible conductive substrate is one of carbon cloth or foamed metal; the foamed metal is selected from one of foamed nickel and foamed copper; the rigid conductive substrate is one of carbon paper or conductive glass.

[0009] A second aspect of this disclosure provides a method for preparing the electrocatalytic material described in the first aspect of this disclosure, the method comprising:

[0010] S1: Nickel salt, molybdenum salt, iron salt and complexing agent are mixed to obtain a mixed solution; the mixed solution is adjusted to alkalinity using a pH adjuster to obtain an electrolyte;

[0011] S2: The three-dimensional Ni nanoframework is used as the working electrode and placed in the electrolyte obtained in S1 for electroplating.

[0012] Optionally, the nickel salt in step S1 is selected from one or more of nickel chloride, nickel sulfate, and nickel nitrate, preferably nickel chloride; the molybdenum salt is selected from one or more of sodium molybdate, potassium molybdate, and ammonium molybdate, preferably sodium molybdate; the iron salt is selected from one or more of ferrous sulfate and ferrous chloride, preferably ferrous sulfate; and the complexing agent is selected from one or more of sodium citrate, potassium citrate, ethylenediaminetetraacetic acid (EDTA), and disodium EDTA, preferably sodium citrate.

[0013] Optionally, the mass ratio of the nickel salt, the molybdenum salt, the iron salt, and the complexing agent in step S1 is 1:(0.03-0.25):(0.03-0.25):(0.35-1.50), preferably 1:(0.06-0.13):(0.06-0.13):(0.45-0.75);

[0014] The concentration of the nickel salt is 0.04–0.08 g / ml; the concentration of the molybdenum salt is 0.002–0.01 g / ml; the concentration of the iron salt is 0.002–0.01 g / ml; and the concentration of the complexing agent is 0.03–0.06 g / ml.

[0015] Step S1 further includes adjusting the pH of the mixed solution to above 9 using a pH adjuster; the pH adjuster includes one or more of sodium carbonate, sodium hydroxide, and potassium hydroxide, preferably sodium carbonate.

[0016] Optionally, in step S2, the electroplating conditions include: a current density of 50–300 mA / cm². 2 Preferably 100-200 mA / cm 2 The electroplating time is 200–600 s, preferably 300–560 s; the reference electrode is one or more of silver chloride electrode, mercury / mercuric oxide electrode and saturated calomel electrode, preferably silver chloride electrode; the counter electrode is one or more of platinum wire and carbon rod, preferably platinum wire.

[0017] Optionally, the three-dimensional Ni nanoframework has a cross-sectional diameter of 90–120 nm and a BET specific surface area of ​​2.7–2.9 m². 2 / g; In the XRD pattern of the three-dimensional Ni nanoframework, there are characteristic peaks at 2θ of 37-40°, 40-43°, 44-47°, 55-60°, 70-74° and 75-80°.

[0018] Optionally, the three-dimensional Ni nanoframework is prepared by the following method:

[0019] Nickel hydroxide nano-precursors are prepared on a conductive substrate; the nickel hydroxide nano-precursors are then calcined in a reducing atmosphere.

[0020] Optionally, the reducing atmosphere is a mixture of hydrogen and an inert gas; the volume fraction of hydrogen is 2% to 8%.

[0021] The calcination conditions include: a calcination temperature of 300–500°C and a calcination time of 0.5–2 hours.

[0022] This third aspect of the disclosure provides the use of electrocatalytic materials prepared by the methods described in the second aspect of the disclosure in oxygen evolution electrodes or hydrogen evolution electrodes for water electrolysis.

[0023] Through the above technical solution, this disclosure prepares a NiMoFe nanoalloy layer and coats a three-dimensional Ni nanoframework to obtain a self-supporting dual-function electrocatalytic material. This achieves the advantages of high catalytic activity and high stability in water electrolysis catalytic materials. Moreover, this electrocatalytic material has dual functionality and can be used as a highly efficient hydrogen evolution electrode and oxygen evolution electrode.

[0024] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0026] Figure 1 This is an electron microscope (SEM) image of the electrocatalytic material obtained in Example 1 of this application.

[0027] Figure 2 This is the X-ray diffraction (XRD) pattern of the electrocatalytic material obtained in Example 1 of this application. Detailed Implementation

[0028] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0029] The first aspect of this disclosure provides a self-supporting bifunctional electrocatalytic material, the electrocatalytic material comprising a three-dimensional composite material, the three-dimensional composite material comprising a three-dimensional Ni nanoframework and a NiMoFe nanoalloy layer coated on the three-dimensional Ni nanoframework.

[0030] The self-supporting bifunctional electrocatalytic material disclosed herein exhibits good catalytic activity and catalytic stability in the hydrogen evolution and oxygen evolution reactions of water electrolysis.

[0031] According to one embodiment of this disclosure, in the XRD pattern of the electrocatalytic material, characteristic peaks are observed at 2θ values ​​of 37–40°, 40–43°, 44–47°, 55–60°, 70–74°, and 75–80°. XPS analysis revealed that the atomic content of Ni in the electrocatalytic material is 58–84%, the atomic content of Mo is 9–29%, and the atomic content of Fe is 4–26%. The XPS test results indicate the content of each element on the surface of the electrocatalytic material.

[0032] According to one embodiment of this disclosure, the BET specific surface area of ​​the electrocatalytic material is 2.1–2.9 m². 2 / g, preferably 2.3~2.7m 2 / g.

[0033] According to one embodiment of this disclosure, the thickness of the NiMoFe nanoalloy layer is 10–50 nm. The above embodiment is beneficial for the electrocatalytic material to exhibit good catalytic activity and catalytic stability in the hydrogen evolution and oxygen evolution reactions of water electrolysis.

[0034] According to one embodiment of this disclosure, the electrocatalytic material further includes a conductive substrate, and the three-dimensional composite material is coated on the conductive substrate; the conductive substrate is a flexible conductive substrate or a rigid conductive substrate; the flexible conductive substrate is one of carbon cloth or foamed metal; the foamed metal is selected from one of foamed nickel and foamed copper; the rigid conductive substrate is one of carbon paper or conductive glass (FTO).

[0035] A second aspect of this disclosure provides a method for preparing the electrocatalytic material described in the first aspect of this disclosure, the method comprising:

[0036] S1: Nickel salt, molybdenum salt, iron salt and complexing agent are mixed to obtain a mixed solution; the mixed solution is adjusted to alkalinity using a pH adjuster to obtain an electrolyte;

[0037] S2: The three-dimensional Ni nanoframework is used as the working electrode and placed in the electrolyte obtained in S1 for electroplating.

[0038] According to one embodiment of this disclosure, in step S1, the nickel salt is selected from one or more of nickel chloride, nickel sulfate, and nickel nitrate, preferably nickel chloride; the molybdenum salt is selected from one or more of sodium molybdate, potassium molybdate, and ammonium molybdate, preferably sodium molybdate; the iron salt is selected from one or more of ferrous sulfate and ferrous chloride, preferably ferrous sulfate; the complexing agent is selected from one or more of sodium citrate, potassium citrate, ethylenediaminetetraacetic acid (EDTA), and disodium EDTA, preferably sodium citrate. In a further embodiment, the mass ratio of the nickel salt, the molybdenum salt, the iron salt, and the complexing agent in step S1 is 1:(0.03–0.25):(0.03–0.25):(0.35–1.50), preferably 1:(0.06–0.13):(0.06–0.13):(0.45–0.75); the concentration of the nickel salt is 0.04–0.08 g / ml, preferably… The concentration of the molybdenum salt is selected to be 0.068–0.078 g / ml; the concentration of the molybdenum salt is 0.002–0.01 g / ml, preferably 0.005–0.009 g / ml; the concentration of the iron salt is 0.002–0.01 g / ml, preferably 0.005–0.008 g / ml; and the concentration of the complexing agent is 0.03–0.06 g / ml, preferably 0.045–0.055 g / ml. The above embodiments are beneficial for obtaining electrocatalytic materials with good surface structures, resulting in electrocatalytic materials with high electrochemical active area and good conductivity. This facilitates electron conduction between the three-dimensional Ni nanoframework and the conductive substrate, further enhancing the catalytic activity and stability of the electrocatalytic material in the hydrogen evolution and oxygen evolution reactions of water electrolysis, thereby improving catalytic performance.

[0039] According to one embodiment of this disclosure, step S1 further includes adjusting the pH of the mixed solution to above 9 using a pH adjuster; the pH adjuster includes one or more of sodium carbonate, sodium hydroxide, and potassium hydroxide, preferably sodium carbonate. The above embodiment is beneficial for obtaining electrocatalytic materials with good surface structures, resulting in electrocatalytic materials with high electrochemical active area and good conductivity. This facilitates electron conduction between the three-dimensional Ni nanoframework and the conductive substrate, further enhancing the catalytic activity and stability of the electrocatalytic material in the hydrogen evolution and oxygen evolution reactions of water electrolysis, thereby improving catalytic performance.

[0040] According to one embodiment of this disclosure, in step S2, the electroplating conditions include: a current density of 50–300 mA / cm². 2 Preferably 100-200 mA / cm 2The electroplating time is 200–600 s, preferably 300–560 s; the reference electrode is one or more of silver chloride electrode, mercury / mercuric oxide electrode, and saturated calomel electrode, preferably silver chloride electrode; the counter electrode is one or more of platinum wire and carbon rod, preferably platinum wire. The above embodiments are beneficial for obtaining electrocatalytic materials with good surface structures, resulting in electrocatalytic materials with high electrochemical active area and good conductivity. This facilitates electron conduction between the three-dimensional Ni nanoframework and the conductive substrate, further enhancing the catalytic activity and stability of the electrocatalytic material in the hydrogen evolution and oxygen evolution reactions of water electrolysis, thereby improving catalytic performance.

[0041] According to one embodiment of this disclosure, the three-dimensional Ni nanoframework has a cross-sectional diameter of 90–120 nm and a BET specific surface area of ​​2.7–2.9 m². 2 / g; In the XRD pattern of the three-dimensional Ni nanoframework, characteristic peaks are observed at 2θ values ​​of 37–40°, 40–43°, 44–47°, 55–60°, 70–74°, and 75–80°. The above-described embodiments are beneficial for obtaining electrocatalytic materials with good surface structures, resulting in electrocatalytic materials with high electrochemical active area and good conductivity. This facilitates electron conduction between the three-dimensional Ni nanoframework and the conductive substrate, further enhancing the catalytic activity and stability of the electrocatalytic material in the hydrogen evolution and oxygen evolution reactions of water electrolysis, thereby improving catalytic performance.

[0042] According to one embodiment of this disclosure, the three-dimensional Ni nanoframework is prepared by the following method: preparing a nickel hydroxide nano-precursor on a conductive substrate; and calcining the nickel hydroxide nano-precursor under a reducing atmosphere. In a further embodiment, the reducing atmosphere is a mixture of hydrogen and an inert gas; the volume fraction of the hydrogen is 2%–8%; and the calcination conditions include: a calcination temperature of 300–500°C, preferably 350–450°C, and a calcination time of 0.5–2 h. The above embodiments are beneficial for obtaining electrocatalytic materials with good surface structures, resulting in electrocatalytic materials with high electrochemical active area and good conductivity. This facilitates electron conduction between the three-dimensional Ni nanoframework and the conductive substrate, further enhancing the catalytic activity and stability of the electrocatalytic material in the hydrogen evolution and oxygen evolution reactions of water electrolysis, thereby improving catalytic performance.

[0043] This third aspect of the disclosure provides the use of electrocatalytic materials prepared by the methods described in the second aspect of the disclosure in oxygen evolution electrodes or hydrogen evolution electrodes for water electrolysis.

[0044] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0045] Unless otherwise specified, all reagents used in the examples and comparative examples are commercially available products.

[0046] The BET test was performed on an instrument of model SA3100.

[0047] XRD was performed on a Philips PW 1830 instrument.

[0048] XPS was performed on a PHI 5600 instrument.

[0049] SEM was performed on an instrument of model JSM-6700F.

[0050] Electrochemical performance was performed on a CHI 760D electrochemical workstation.

[0051] Example 1

[0052] (1) Place the conductive substrate carbon cloth into a glass container containing 15 mL of 0.125 mol / L nickel chloride hexahydrate and 0.25 mol / L hexamethylenetetramine aqueous solution, seal the glass container with a plastic lid, and place it in an oven at 100°C for 10 hours to obtain nickel hydroxide precursor.

[0053] (2) The nickel hydroxide precursor grown on carbon cloth was washed with distilled water and ethanol and dried in a vacuum oven at 80°C for 120 min. The dried product was transferred to a tube furnace and heated to 400°C at a heating rate of 5°C / min. It was then calcined in a reducing atmosphere for 1 h. The reducing atmosphere was a mixture of hydrogen and nitrogen (hydrogen volume fraction of 5.0%) to obtain a three-dimensional Ni nanoframework.

[0054] (3) Dissolve 2.3g nickel chloride hexahydrate, 0.2g sodium molybdate dihydrate, 0.16g ferrous sulfate heptahydrate and 1.7g sodium citrate dihydrate in 30mL of distilled water, and adjust the pH of the solution to above 9 using sodium carbonate to obtain the electrolyte; the mass ratio of the nickel salt, the molybdenum salt, the iron salt and the complexing agent is 1:0.087:0.069:0.74, the concentration of the nickel salt is 0.077g / ml; the concentration of the molybdenum salt is 0.0067g / ml; the concentration of the iron salt is 0.0053g / ml; the concentration of the complexing agent is 0.0567g / ml;

[0055] (4) The three-dimensional Ni nanoframework obtained in step (2) is used as the working electrode and electroplated in the electrolyte obtained in step (3), with a silver chloride electrode as the reference electrode and a platinum wire as the counter electrode, at an electrode pressure of 160 mA / cm². 2 Electrodeposition was performed at a constant current for 480 seconds. The resulting product was washed several times with distilled water and dried in a vacuum oven at 30°C to obtain the electrocatalytic material.

[0056] XRD, SEM, and XPS analyses revealed that the surface of this electrocatalytic material contains 76% Ni, 15% Mo, and 9% Fe, with a BET specific surface area of ​​2.6 m². 2 / g; In the XRD pattern, characteristic peaks are observed at 2θ values ​​of 26°, 38°, 41°, 44°, 58°, 72°, and 78°, attributed to the three-dimensional Ni nanoframework in the electrocatalytic material; the cross-sectional diameter of the three-dimensional Ni nanoframework is 100 nm, and the BET specific surface area is 2.7 m². 2 / g; the thickness of the NiMoFe nanoalloy layer is 20nm.

[0057] Example 2

[0058] The method in this embodiment is the same as that in embodiment 1, except that:

[0059] In step (3), 2.3 g of nickel chloride hexahydrate, 0.4 g of sodium molybdate dihydrate, 0.32 g of ferrous sulfate heptahydrate, and 1.7 g of sodium citrate dihydrate were dissolved in 30 mL of distilled water. The mass ratio of the nickel salt, the molybdenum salt, the iron salt, and the complexing agent was 1:0.17:0.14:0.74. The concentration of the nickel salt was 0.077 g / mL, the concentration of the molybdenum salt was 0.013 g / mL, the concentration of the iron salt was 0.011 g / mL, and the concentration of the complexing agent was 0.0567 g / mL.

[0060] XRD, SEM, and XPS analyses revealed that the electrocatalytic material contained 77% Ni, 13% Mo, and 10% Fe by mass on its surface, and had a BET specific surface area of ​​2.5 m². 2 / g; In the XRD pattern, characteristic peaks are observed at 2θ values ​​of 26°, 38°, 41°, 44°, 58°, 72°, and 78°; The three-dimensional Ni nanoframework has a cross-sectional diameter of 100 nm and a BET specific surface area of ​​2.7 m². 2 / g; The thickness of the NiMoFe nanoalloy layer is 25nm.

[0061] Example 3

[0062] The method in this embodiment is the same as that in embodiment 1, except that:

[0063] In step (3), 2.3 g of nickel chloride hexahydrate, 0.1 g of sodium molybdate dihydrate, 0.08 g of ferrous sulfate heptahydrate, and 0.85 g of sodium citrate dihydrate were dissolved in 30 mL of distilled water. The mass ratio of the nickel salt, the molybdenum salt, the iron salt, and the complexing agent was 1:0.043:0.035:0.37. The concentration of the nickel salt was 0.077 g / mL, the concentration of the molybdenum salt was 0.003 g / mL, the concentration of the iron salt was 0.003 g / mL, and the concentration of the complexing agent was 0.028 g / mL.

[0064] XRD, SEM, and XPS analyses revealed that the electrocatalytic material contained 84% Ni, 10% Mo, and 6% Fe by mass on its surface, with a BET specific surface area of ​​2.3 m². 2 / g; In the XRD pattern, characteristic peaks are observed at 2θ values ​​of 26°, 38°, 41°, 44°, 58°, 72°, and 78°; The three-dimensional Ni nanoframework has a cross-sectional diameter of 100 nm and a BET specific surface area of ​​2.7 m². 2 / g; The thickness of the NiMoFe nanoalloy layer is 25nm.

[0065] Example 4

[0066] The method in this embodiment is the same as in embodiment 1, except that in step (4), the constant current is 60mA / cm. 2 The electrodeposition time was 240 s.

[0067] XRD, SEM, and XPS analyses revealed that the electrocatalytic material contained 79% Ni, 15% Mo, and 6% Fe by mass on its surface, and had a BET specific surface area of ​​2.6 m². 2 / g; In the XRD pattern, characteristic peaks are observed at 2θ values ​​of 26°, 38°, 41°, 44°, 58°, 72°, and 78°; The three-dimensional Ni nanoframework has a cross-sectional diameter of 100 nm and a BET specific surface area of ​​2.7 m². 2 / g; the thickness of the NiMoFe nanoalloy layer is 10nm.

[0068] Example 5

[0069] The method in this embodiment is the same as in embodiment 1, except that in step (4), the constant current is 360mA / cm. 2 The electrodeposition time was 80 s.

[0070] XRD, SEM, and XPS analyses revealed that the electrocatalytic material contains 75% Ni, 10% Mo, and 15% Fe by mass on its surface, and has a BET specific surface area of ​​2.4 m². 2 / g; In the XRD pattern, characteristic peaks are observed at 2θ values ​​of 26°, 38°, 41°, 44°, 58°, 72°, and 78°; The three-dimensional Ni nanoframework has a cross-sectional diameter of 100 nm and a BET specific surface area of ​​2.7 m². 2 / g; The thickness of the NiMoFe nanoalloy layer is 15nm.

[0071] Comparative Example 1

[0072] The method used in this comparative example is the same as in Example 1, except that only steps (1) and (2) of Example 1 are performed to obtain a three-dimensional Ni nanoframework. The cross-sectional diameter of this three-dimensional Ni nanoframework is 100 nm, and its BET specific surface area is 2.7 m². 2 / g.

[0073] Comparative Example 2

[0074] (1) After cleaning the nickel mesh with dilute hydrochloric acid, ethanol, and ultrapure water, it is used as the cathode, and the platinum sheet is used as the anode. A 0.1M Ni(Cl)2 and 2M NH4Cl solution is prepared as the electrolyte and placed in a beaker. The positive and negative terminals of the DC power supply are connected to the platinum sheet and the nickel mesh, respectively, and installed in the beaker so that the electrodes are submerged in the solution. Under room temperature conditions, the current density is set to 3A / cm. 2 Electrodeposition treatment for 90 seconds;

[0075] (2) Dissolve 2.3g nickel chloride hexahydrate, 0.16g ferrous sulfate heptahydrate and 1.7g sodium citrate dihydrate in 30mL of distilled water, and adjust the pH of the solution to above 9 using sodium carbonate to obtain the electrolyte.

[0076] (3) The porous Ni obtained in step (1) is used as the working electrode and electroplated in the electrolyte obtained in step (2), with a silver chloride electrode as the reference electrode and a platinum wire as the counter electrode, at an electrode pressure of 160 mA / cm². 2 Electrodeposition was performed at a constant current for 480 seconds. The resulting product was washed several times with distilled water and dried in a vacuum oven at 30°C to obtain the electrocatalytic material.

[0077] Test Example 1

[0078] The electrocatalytic materials of Examples 1-5 and Comparative Examples 1-2 were used as working electrodes, and their activity and stability as electrodes for hydrogen production (HER) and oxygen production (OER) by water electrolysis were tested in a three-electrode system. The electrolyte was 1M KOH, the counter electrode was a carbon rod, and the reference electrode was a Hg / HgO electrode.

[0079] Before testing, each electrode was activated under appropriate conditions: the hydrogen production electrode and the oxygen production electrode underwent cyclic voltammetry treatment until the current stabilized. After pretreatment, the hydrogen and oxygen production polarization curves and time-current curves at a fixed current density were measured for each electrode, with the obtained current density being 10 mA / cm². 2 The required overpotential magnitude for each electrode and 100 mA / cm 2 The overpotential of each electrode after constant current testing is shown in Table 1 below:

[0080] Table 1

[0081]

[0082]

[0083] According to the data in Table 1, compared with Comparative Example 1, the electrocatalytic material of this disclosure exhibits low overpotential, small Tafel slope, and high catalytic activity when used as a hydrogen production electrode or oxygen production electrode, while also possessing good electrochemical stability. Compared with Comparative Example 2, which was only used as an oxygen production electrode, the electrocatalytic material of this disclosure exhibits considerable catalytic activity and electrochemical stability when used as an oxygen production electrode. Furthermore, the electrocatalytic material of this disclosure can also be used as a hydrogen production electrode, exhibiting low overpotential, small Tafel slope, high catalytic activity, and good electrochemical stability. A comparison of Example 1 with Examples 2 and 3 shows that within the preferred mass ratio range of nickel salt, molybdenum salt, iron salt, and complexing agent in this disclosure, the electrocatalytic material exhibits higher catalytic activity. A comparison of Example 1 with Examples 4 and 5 shows that under the preferred electroplating conditions in this disclosure, the electrocatalytic material exhibits higher catalytic activity.

[0084] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0085] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0086] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A self-supporting bifunctional electrocatalytic material, characterized in that, The electrocatalytic material includes a three-dimensional composite material comprising a three-dimensional Ni nanoframework and a NiMoFe nanoalloy layer coated on the three-dimensional Ni nanoframework; the electrocatalytic material also includes a conductive substrate, on which the three-dimensional composite material is coated, and the conductive substrate is carbon cloth. The three-dimensional Ni nanoframework is prepared by the following method: preparing a nickel hydroxide nano-precursor on a conductive substrate; calcining the nickel hydroxide nano-precursor under a reducing atmosphere; and obtaining the NiMoFe nano-alloy layer by electroplating the three-dimensional Ni nanoframework in an electrolyte composed of nickel salt, molybdenum salt, iron salt, complexing agent and pH adjuster.

2. The electrocatalytic material according to claim 1, wherein, The BET specific surface area of ​​the electrocatalytic material is 2.1~2.9 m². 2 / g; In the XRD pattern of the electrocatalytic material, there are characteristic peaks at 2θ of 37~40°, 40~43°, 44~47°, 55~60°, 70~74° and 75~80°; XPS analysis showed that the atomic content of Ni in the electrocatalytic material was 58~84%, the atomic content of Mo was 9~29% and the atomic content of Fe was 4~26%.

3. The electrocatalytic material according to claim 2, wherein, The BET specific surface area of ​​the electrocatalytic material is 2.3~2.7 m². 2 / g.

4. The electrocatalytic material according to claim 1, wherein, The thickness of the NiMoFe nanoalloy layer is 10~50 nm.

5. The electrocatalytic material according to claim 1, wherein, The reducing atmosphere is a mixture of hydrogen and an inert gas; the volume fraction of the hydrogen is 2% to 8%. The calcination conditions include: a calcination temperature of 300~500℃ and a calcination time of 0.5~2h.

6. A method for preparing the electrocatalytic material according to any one of claims 1 to 5, characterized in that, The method includes: S1: Nickel salt, molybdenum salt, iron salt and complexing agent are mixed to obtain a mixed solution; the mixed solution is adjusted to alkalinity using a pH adjuster to obtain an electrolyte; S2: The three-dimensional Ni nanoframework is used as the working electrode and placed in the electrolyte obtained in S1 for electroplating.

7. The method according to claim 6, wherein, In step S1, the nickel salt is selected from one or more of nickel chloride, nickel sulfate, and nickel nitrate; the molybdenum salt is selected from one or more of sodium molybdate, potassium molybdate, and ammonium molybdate; the iron salt is selected from one or more of ferrous sulfate and ferrous chloride; and the complexing agent is selected from one or more of sodium citrate, potassium citrate, ethylenediaminetetraacetic acid, and disodium ethylenediaminetetraacetic acid.

8. The method according to claim 7, wherein, In step S1, the nickel salt is nickel chloride; the molybdenum salt is sodium molybdate; the iron salt is ferrous sulfate; and the complexing agent is sodium citrate.

9. The method according to claim 6, wherein, In step S1, the mass ratio of the nickel salt, the molybdenum salt, the iron salt, and the complexing agent is 1:(0.03~0.25):(0.03~0.25):(0.35~1.50). The concentration of the nickel salt is 0.04~0.08 g / ml; the concentration of the molybdenum salt is 0.002~0.01 g / ml; the concentration of the iron salt is 0.002~0.01 g / ml; and the concentration of the complexing agent is 0.03~0.06 g / ml. Step S1 further includes adjusting the pH of the mixed solution to above 9 using a pH adjuster; the pH adjuster includes one or more of sodium carbonate, sodium hydroxide, and potassium hydroxide.

10. The method according to claim 9, wherein, In step S1, the mass ratio of the nickel salt, the molybdenum salt, the iron salt, and the complexing agent is 1:(0.06~0.13):(0.06~0.13):(0.45~0.75).

11. The method according to claim 9, wherein, The pH adjuster is sodium carbonate.

12. The method according to claim 6, wherein, In step S2, the electroplating conditions include: a current density of 50~300 mA / cm². 2 The electroplating time is 200~600s; the reference electrode is one or more of silver chloride electrode, mercury / mercuric oxide electrode and saturated calomel electrode; the counter electrode is one or more of platinum wire and carbon rod.

13. The method according to claim 12, wherein, In step S2, the electroplating conditions include: a current density of 100~200 mA / cm². 2 The electroplating time is 300~560s.

14. The method according to claim 12, wherein, In step S2, the reference electrode is a silver chloride electrode.

15. The method according to claim 12, wherein, In step S2, the counter electrode is a platinum wire.

16. The method according to claim 6, wherein, The three-dimensional Ni nanoframework has a cross-sectional diameter of 90-120 nm and a BET specific surface area of ​​2.7-2.9 m². 2 / g; In the XRD pattern of the three-dimensional Ni nanoframework, there are characteristic peaks at 2θ of 37~40°, 40~43°, 44~47°, 55~60°, 70~74° and 75~80°.

17. Use of the electrocatalytic material prepared by the method of any one of claims 6 to 16 in the oxygen evolution electrode or hydrogen evolution electrode of water electrolysis.

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