A nickel nitride-tungsten nitride heterostructure for electrocatalytic alkaline hydrogen oxidation reaction

Abstract

The present invention belongs to the field of two-dimensional heterostructure electrocatalysts and fuel cell technologies, and discloses a nickel nitride-tungsten nitride heterostructure for electrocatalytic alkaline hydrogen oxidation reaction, and its preparation method comprises the following steps: (1) mixing a nickel source material and a tungsten source material with a solution containing an organic solvent and ammonia water, and heating and stirring under oil bath conditions to obtain a NiW-OH precursor nanosheet; (2) heating the NiW-OH precursor nanosheet in an atmosphere containing ammonia for reduction and nitridation reaction, thereby obtaining a two-dimensional nickel nitride-tungsten nitride heterostructure nanosheet. The present invention improves the composition of the nickel-based heterostructure and the corresponding preparation method, and the obtained nickel nitride-tungsten nitride heterostructure nanosheet exhibits high catalytic activity and strong stability in the anode hydrogen oxidation reaction of the alkaline membrane fuel cell. The synthesis method of the present invention is simple, time-consuming, mild and low-cost, and is easy to achieve large-scale industrial synthesis.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional heterostructure electrocatalysts and fuel cells, and more specifically, relates to a nickel nitride-tungsten nitride heterostructure for electrocatalytic alkaline hydrogen oxidation reaction. Background Art

[0002] Anion exchange membrane fuel cells are considered to be the most promising next-generation fuel cells because they can use inexpensive non-precious metal electrocatalysts. However, the kinetics of the anodic hydrogen oxidation reaction are relatively slow, and a certain amount of platinum (Pt) group metal loading is currently required to achieve the target activity, which limits its industrialization process. Therefore, the development of inexpensive and efficient non-precious metal catalysts for the anodic hydrogen oxidation reaction of anion exchange membrane fuel cells is of great significance. Nickel (Ni)-based materials have been proven to be the most promising alkaline hydrogen oxidation catalysts to replace precious metal materials, but their performance is still difficult to compare with Pt group precious metal catalysts. In order to improve the catalytic performance of nickel-based catalysts, it is crucial to balance and optimize the binding ability of nickel-based catalysts to hydrogen oxidation reaction intermediates (hydrogen and hydroxyl species).

[0003] Heterostructured catalysts, due to the synergistic effects between their different components, can not only adjust the electronic structure to optimize the binding energy of key reaction intermediates, but also provide different active sites to balance the adsorption / desorption behavior of reaction intermediates. There are also reports on nickel-based heterostructured catalysts in the prior art, but they often involve heterostructures of nickel with other oxides or hydroxides (NiO, MoO2, V2O3, Ni(OH)2). Although these have improved catalytic performance to a certain extent, there is still room for improvement.

[0004] At the same time, two-dimensional transition metal nitride materials have advantages such as large specific surface area and high conductivity, and are promising catalytic material systems in the field of energy-related electrocatalysis. Combining the advantages of heterogeneous structures and two-dimensional transition metal nitrides, it is possible to effectively balance and optimize the binding ability of nickel-based catalysts to hydrogen and hydroxyl species, thereby improving the hydrogen oxidation catalytic performance of nickel-based catalysts. However, most of the two-dimensional heterogeneous structure nitride catalysts reported so far require the use of substrate materials such as nickel foam or high-temperature reactions; when using high-temperature reactions, the preparation method is complicated and cumbersome, which is not conducive to large-scale preparation; and when using substrate materials such as nickel foam, the product obtained is a block rather than a powder, which is not convenient for practical application (even if a powder is obtained after subsequent treatment, other impurities will be introduced due to the presence of the substrate, affecting the application effect). Summary of the Invention

[0005] In response to the above-mentioned deficiencies or improvements in the prior art, the present invention aims to provide a nickel nitride-tungsten nitride heterostructure for electrocatalytic alkaline hydrogen oxidation reactions. By modifying the composition of the nickel-based heterostructure and improving the corresponding preparation method, the resulting nickel nitride-tungsten nitride heterostructure nanosheets exhibit high catalytic activity and strong stability in the anodic hydrogen oxidation reaction of alkaline membrane fuel cells. The design concept of the present invention is effective and universal, and the synthesis method is simple, time-saving, mild, and low-cost, making it easy to achieve large-scale industrial synthesis.

[0006] To achieve the above object, according to one aspect of the present invention, a method for preparing two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets is provided, characterized in that it comprises the following steps:

[0007] (1) mixing a nickel source material and a tungsten source material with a solution containing an organic solvent and aqueous ammonia, and heating and stirring the resulting mixture in an oil bath to obtain NiW-OH precursor nanosheets;

[0008] Wherein, the nickel source material is selected from nickel nitrate, nickel chloride, and nickel acetate; the tungsten source material is selected from ammonium metatungstate and ammonium tungstate; and the organic solvent is selected from ethylene glycol and diethylene glycol.

[0009] (2) The NiW-OH precursor nanosheet obtained in step (1) is placed in an atmosphere containing ammonia and heated to perform reduction and nitridation reactions, thereby obtaining a two-dimensional nickel nitride-tungsten nitride heterostructure nanosheet.

[0010] As a further preferred embodiment of the present invention, in step (1), the molar ratio of the nickel element contained in the nickel source material to the tungsten element contained in the tungsten source material is (4-8):1;

[0011] Preferably, the molar ratio of the nickel element contained in the nickel source material to the tungsten element contained in the tungsten source material is 4:1, 6:1 or 8:1.

[0012] As a further preference of the present invention, in step (1), the solution containing the organic solvent and ammonia water is equal to a mixed solution obtained by mixing deionized water, the organic solvent and concentrated ammonia water in a volume ratio of 5:45:2; wherein the mass percentage concentration of the concentrated ammonia water is 25% to 28%.

[0013] As a further preference of the present invention, in step (1), the heating and stirring under oil bath conditions is specifically heating and stirring at an oil bath temperature of 150° C. for 30 min.

[0014] As a further preferred embodiment of the present invention, in step (2), the atmosphere containing ammonia is specifically a flowing ammonia atmosphere, and the flow rate of the ammonia is 100-200 sccm.

[0015] As a further preferred embodiment of the present invention, in step (2), the heating for reduction and nitridation reaction is specifically heating to 400°C-450°C, and the reaction time is 2-3h;

[0016] Preferably, the heating rate used in the heating is 5-10°C / min.

[0017] As a further preferred embodiment of the present invention, the molar ratio of the nickel element contained in the nickel source material and the tungsten element contained in the tungsten source material in step (1) is 6:1;

[0018] In step (2), the heating is performed to carry out reduction and nitridation reaction, specifically heating to 400° C. and reacting for 2 hours.

[0019] According to another aspect of the present invention, the present invention provides a two-dimensional nickel nitride-tungsten nitride heterostructure nanosheet prepared by the above preparation method.

[0020] According to another aspect of the present invention, the present invention provides the use of the above-mentioned two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets as a catalyst in the anode hydrogen oxidation reaction of an anion exchange membrane fuel cell.

[0021] Compared to existing technologies, the present invention's technical solution, conceived above, allows the synthesis of two-dimensional nickel nitride-tungsten nitride heterostructured nanosheets without the need for a substrate. The synthesized two-dimensional nickel nitride-tungsten nitride heterostructured nanosheets, containing both nickel nitride and tungsten nitride, exhibit high activity and stability during alkaline hydrogen oxidation reactions.

[0022] The method of the present invention avoids the use of a substrate material, reducing tedious steps such as substrate cleaning. Furthermore, the reduction and nitridation reactions in an ammonia atmosphere are preferably carried out at a temperature of 400°C to 450°C, avoiding high temperatures (e.g., the 800°C and above reported in existing molten salt methods). This method offers advantages such as simplicity, time efficiency, and low cost, and is expected to enable large-scale production. The two-dimensional nickel nitride-tungsten nitride heterostructured nanosheets prepared by the present invention exhibit high activity and stability during alkaline hydrogen oxidation reactions.

[0023] Specifically, the present invention can achieve the following beneficial effects:

[0024] (1) The present invention prepares nickel nitride-tungsten nitride heterostructured nanosheets through a simple, substrate-free, low-temperature method. The method is simple, time-efficient, mild, and low-cost, making it easy to implement large-scale industrial synthesis. Furthermore, since the reaction requires no substrate, the resulting product is a powder, which is very convenient for practical applications. The powder has few impurities and exhibits excellent catalytic performance.

[0025] (2) In the nanosheet preparation method of the present invention, the resulting nanosheets have uniform thickness, stable structure, and easily controllable composition. When the molar ratio of nickel nitrate to ammonium metatungstate is changed, the ratio of nickel nitride to tungsten nitride in the resulting heterostructure changes accordingly. As the molar ratio of nickel nitrate to ammonium metatungstate increases, the nickel nitride content increases. Alternatively, when the molar ratio of nickel nitrate to ammonium metatungstate remains unchanged and the nitriding temperature increases, the tungsten nitride content increases.

[0026] (3) In the two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets formed by the present invention, nickel nitride and tungsten nitride serve as adsorption sites for hydrogen and hydroxyl species, respectively, effectively avoiding the limitation of hydrogen and hydroxyl species adsorbed solely on nickel sites. Furthermore, due to the electronic interaction between nickel nitride and tungsten nitride, the adsorption strength of hydrogen and hydroxyl species is optimized, thereby accelerating the kinetics of the alkaline hydrogen oxidation reaction.

[0027] This invention utilizes the phase composition and interfacial electronic interactions of heterostructures to balance and optimize the adsorption sites and adsorption strength of intermediates in alkaline hydrogen oxidation reactions, successfully using them as electrocatalysts for catalyzing alkaline hydrogen oxidation reactions. Based on the method of the present invention, the molar ratio of nickel to tungsten in the raw materials can be controlled to 6:1, and the subsequent heating reduction and nitridation process is controlled at 400°C for 2 hours, thereby obtaining two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets. By regulating the ratio of nickel nitride to tungsten nitride in the heterostructure, the number of hydrogen and hydroxyl species adsorption sites is balanced.

[0028] (4) The two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets prepared by the present invention have excellent catalytic activity and stability in the hydrogen oxidation reaction at the anode of alkaline membrane fuel cells. Taking the product prepared in Example 1 as an example, the nickel nitride-tungsten nitride heterostructure nanosheets showed a high catalytic activity of 2.27 mA / cm at an overpotential of 50 mV. 2 The current density is better than that of commercial platinum-carbon catalysts. Its specific activity reaches 47μA / cm 2 , far higher than nickel nitride nanosheets and higher than most other nickel-based catalysts reported so far. Furthermore, the current density of the nickel nitride-tungsten nitride heterostructured nanosheet catalyst showed no significant attenuation during 2,000 cycles of alkaline hydrogen oxidation, demonstrating excellent stability.

[0029] It can be seen that the method of preparing two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets of the present invention and the corresponding two-dimensional nickel nitride-tungsten nitride heterostructure nanosheet products have great industrial application potential in the field of anode hydrogen oxidation catalysis technology of anion exchange membrane fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1This is a scanning electron microscope image of the NiW-OH precursor nanosheets prepared in step (1) of Example 1 of the present invention.

[0031] Figure 2 This is a morphology structure diagram of the two-dimensional nickel nitride-tungsten nitride heterostructure nanosheet prepared in Example 1 of the present invention; wherein, Figure 2 a in the figure is a scanning electron microscope image. Figure 2 b Transmission electron micrograph in .

[0032] Figure 3 This is the X-ray diffraction spectrum of the two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets prepared in Example 1 of the present invention.

[0033] Figure 4 This is a high-resolution transmission electron microscopy image of the two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets prepared in Example 1 of the present invention.

[0034] Figure 5 X-ray diffraction spectra of nanosheets prepared under different temperature conditions in Example 2

[0035] Figure 6 The X-ray diffraction spectra of the two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets prepared with different nickel-tungsten molar ratios in Example 3.

[0036] Figure 7 Hydrogen oxidation polarization curves of the two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets prepared in Example 1 of the present invention, the pure nickel nitride nanosheets of Comparative Example 1, the tungsten nitride nanosheets of Comparative Example 2, and a commercial platinum-carbon catalyst.

[0037] Figure 8 This is a comparison chart of the specific activities of the two-dimensional nickel nitride-tungsten nitride heterostructure prepared in Example 1 of the present invention and the nickel nitride nanosheets prepared in Comparative Example 1.

[0038] Figure 9 This is a comparison diagram of the hydrogen oxidation polarization curves of the two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets prepared in Example 1 of the present invention before and after 2000 cycles of testing.

[0039] Figure 10 The following is a comparison of the hydrogen adsorption Gibbs free energy and the binding energy of hydrogen and oxygen species for the two-dimensional nickel nitride-tungsten nitride heterostructure, nickel nitride and tungsten nitride nanosheets prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention. Figure 10 The a in corresponds to the Gibbs free energy of hydrogen adsorption, Figure 10 Where b is the binding energy of hydrogen and oxygen species.

[0040] Figure 11 The X-ray diffraction spectrum and transmission electron microscope image of the nickel nitride nanosheet prepared in Comparative Example 1 are shown. Figure 11 The a in corresponds to the X-ray diffraction spectrum, Figure 11 b in the figure corresponds to the transmission electron microscopy image.

[0041] Figure 12 The X-ray diffraction spectrum and transmission electron microscope image of the tungsten nitride nanosheet prepared in Comparative Example 2 are shown. Figure 12 The a in corresponds to the X-ray diffraction spectrum, Figure 12 b in the figure corresponds to the transmission electron microscopy image. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0043] The ammonia water used in the following examples is all commercially available concentrated ammonia water (mass percentage concentration meets 25% to 28%).

[0044] Example 1

[0045] A method for preparing a two-dimensional nickel nitride-tungsten nitride heterostructure nanosheet comprises the following steps:

[0046] (1) Preparation of NiW-OH precursor nanosheets

[0047] 2.14mmol nickel nitrate and 0.03mmol ammonium metatungstate were added to a three-necked flask (Ni:W molar ratio was 6:1), and 5mL deionized water, 45mL diethylene glycol and 2mL ammonia water were added in sequence under magnetic stirring. The reaction was stirred at 150℃ for 30min under oil bath conditions. The obtained precipitate was washed repeatedly by centrifugation with water and ethanol and freeze-dried to obtain NiW-OH (i.e., nickel-tungsten hydroxide) precursor nanosheets ( Figure 1 ).

[0048] (2) Preparation of two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets

[0049] 20 mg of NiW-OH precursor nanosheet powder was placed in a porcelain boat and heated at a flow rate of 100 sccm NH3 at 10 °C min -1 The temperature was raised to 400°C at a heating rate of 1000 ℃ and the reaction was carried out for 2 hours. After cooling to room temperature, nickel nitride-tungsten nitride heterostructure nanosheets were obtained.

[0050] like Figure 2 As shown, the obtained product is a self-assembled two-dimensional sheet structure, and the nanosheet is composed of multiple interconnected nanoparticles. Figure 3 It shows that nickel nitride-tungsten nitride nanosheets have characteristic XRD diffraction peaks of Ni3N and W5N4. Figure 4 High-resolution transmission electron microscopy (HRTEM) of the nanostructured Ni3N nanostructured composites showed that the composites had distinct, closely adjacent Ni3N and W5N4 phase interfaces, including closely connected heterojunctions formed by the (111) crystal plane of Ni3N and the (101) crystal plane of W5N4 (the interlayer spacings of these two crystal planes were 2.03 angstroms and 2.46 angstroms, respectively, with low lattice mismatch), and closely connected heterojunctions formed by the (002) crystal plane of Ni3N and the (101) crystal plane of W5N4 (the interlayer spacings of these two crystal planes were 2.12 angstroms and 2.46 angstroms, respectively, with low lattice mismatch). The above results demonstrate the formation of nickel nitride-tungsten nitride heterostructure nanosheets.

[0051] Comparative Example 1

[0052] The preparation of pure nickel nitride nanosheets includes the following steps:

[0053] 2.5mmol nickel nitrate was added to a three-necked flask, and 5mL deionized water, 45mL diethylene glycol and 2mL ammonia water were added in sequence under magnetic stirring. The reaction was stirred at 150℃ for 30min under oil bath conditions. The obtained precipitate was washed repeatedly by centrifugation with water and ethanol and freeze-dried to obtain Ni-OH precursor. 20mg Ni-OH precursor powder was placed in a porcelain boat and stirred at a flow rate of 100sccm NH3 at 10℃min. -1 The temperature was raised to 350℃ at a heating rate of 100℃ for 2 hours, and nickel nitride nanosheets were obtained after cooling to room temperature. Figure 11 ).

[0054] Comparative Example 2

[0055] The preparation of pure tungsten nitride nanosheets includes the following steps:

[0056] 2.14 mmol of nickel nitrate and 0.03 mmol of ammonium metatungstate were added to a three-necked flask (Ni:W molar ratio of 6:1). 5 mL of deionized water, 45 mL of diethylene glycol, and 2 mL of aqueous ammonia were added sequentially under magnetic stirring. The reaction was stirred at 150°C in an oil bath for 30 minutes. The resulting precipitate was washed repeatedly by centrifugation with water and ethanol and freeze-dried to obtain NiW-OH nanosheets.

[0057] 20 mg of NiW-OH nanosheet powder was placed in a porcelain boat and heated at a flow rate of 100 sccm NH3 at 10 °C min -1 The heating rate was raised to 400℃ and the reaction was continued for 2 hours. After cooling to room temperature, nickel nitride-tungsten nitride heterostructure nanosheets were obtained. The prepared nickel nitride-tungsten nitride heterostructure nanosheets were etched in 10% HNO3 for 20 minutes to obtain tungsten nitride nanosheets ( Figure 12 ).

[0058] Example 2

[0059] Comparison of different temperatures during the preparation of two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets:

[0060] (1) Preparation of NiW-OH precursor nanosheets

[0061] 2.14 mmol of nickel nitrate and 0.03 mmol of ammonium metatungstate were placed in a three-necked flask. 5 mL of deionized water, 45 mL of diethylene glycol, and 2 mL of aqueous ammonia were added sequentially under magnetic stirring. The reaction was stirred at 150°C in an oil bath for 30 minutes. The resulting precipitate was washed repeatedly by centrifugation with water and ethanol and freeze-dried to obtain NiW-OH precursor nanosheets.

[0062] (2) Preparation of two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets under different temperature conditions

[0063] 20 mg of NiW-OH precursor nanosheet powder was placed in a porcelain boat and heated at a flow rate of 100 sccm NH3 at 10 °C min -1 The heating rate was raised to 350℃, 400℃, and 450℃ and the reaction was continued for 2 hours. Figure 5 As shown in the figure, different temperatures produce different products. At 350°C, the main component of the product is Ni3N; at 400°C and 450°C, the products are Ni3N and W5N4, with the proportion of W5N4 increasing as the temperature rises. This result proves that changing the nitridation temperature can control the ratio of the two phases that make up the Ni3N-W5N4 heterostructure.

[0064] Example 3

[0065] Comparison of different nickel-tungsten ratios during the preparation of two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets:

[0066] (1) Preparation of NiW-OH precursor nanosheets with different nickel-tungsten ratios

[0067] Two groups of samples with different molar ratios of nickel nitrate and ammonium metatungstate were prepared. In the first group, the molar ratios of nickel nitrate and ammonium metatungstate were adjusted to 2.0 mmol and 0.0417 mmol, respectively (corresponding to a Ni:W molar ratio of 4:1); in the second group, the molar ratios of nickel nitrate and ammonium metatungstate were adjusted to 2.22 mmol and 0.023 mmol, respectively (corresponding to a Ni:W molar ratio of 8:1).

[0068] For each sample group, 5 mL of deionized water, 45 mL of diethylene glycol, and 2 mL of aqueous ammonia were added sequentially under magnetic stirring. The reaction was stirred at 150°C in an oil bath for 30 minutes. The resulting precipitate was washed repeatedly by centrifugation with water and ethanol and freeze-dried to obtain NiW-OH precursor nanosheets with varying nickel-tungsten ratios.

[0069] (2) Preparation of two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets

[0070] 20 mg of NiW-OH precursor nanosheet powder with different nickel-tungsten ratios was placed in a porcelain boat and heated at a flow rate of 100 sccm NH3 at 10 °C min -1 The temperature was raised to 400 °C at a heating rate of 1.5 % and the reaction was continued for 2 h

[0071] The two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets obtained in Example 1 with a molar ratio of Ni:W of 6:1 were compared. Figure 6 As shown in the figure, all products contain characteristic XRD diffraction peaks of Ni3N and W5N4. With the increase of the molar ratio of Ni to W in the raw materials, the diffraction peak intensity ratio of the (111) crystal plane of Ni3N and the (101) crystal plane of W5N4 gradually increases (wherein, the diffraction peak position of the (111) crystal plane of Ni3N is 2θ = 44.5°, and the diffraction peak position of the (101) crystal plane of W5N4 is 2θ = 36.3°), indicating that the proportion of Ni3N in the Ni3N-W5N4 heterostructure gradually increases. This result proves that changing the nickel-tungsten ratio of the raw materials can regulate the ratio of the two phases constituting the Ni3N-W5N4 heterostructure.

[0072] Example 4

[0073] Testing and comparison of alkaline hydrogen oxidation reaction performance:

[0074] The two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets prepared in Example 1, the pure nickel nitride nanosheets prepared in Comparative Example 1, the pure tungsten nitride nanosheets prepared in Comparative Example 2, and a commercial platinum-carbon catalyst (purchased from: 20% Pt / C of Johnson Metthey) were used in the alkaline hydrogen oxidation reaction process and compared. 5 mg of catalyst powder mixed with carbon carrier material was dissolved in 1 mL of isopropanol and 15 μL of a 5% mass fraction of Nafion solution, and ultrasonicated for 1 hour to form a uniform ink solution. A certain amount of the catalyst ink solution was drop-coated on the surface of a rotating disk electrode and dried naturally to prepare a working electrode. A carbon rod was used as an auxiliary electrode, and a homemade reversible hydrogen was used as a reference electrode. In a hydrogen-saturated 0.1 M potassium hydroxide electrolyte, the reaction temperature was 2 mV s -1 The polarization curve test was carried out at a scan rate of 1600 rpm and an electrode speed of 1600 rpm. Figure 7As shown, at an overpotential of 50 mV, the nickel nitride-tungsten nitride heterostructure nanosheets showed a high current density of 2.27 mA / cm 2 The current density is better than that of commercial platinum-carbon catalysts. Its specific activity reaches 47μA / cm 2 , much higher than nickel nitride nanosheets ( Figure 8 ), and is higher than most nickel-based catalysts reported so far (as shown in Table 1), reflecting the excellent alkaline hydrogen oxidation catalytic activity of nickel nitride-tungsten nitride heterostructure nanosheets. Figure 9 As shown, the current density of the nickel nitride-tungsten nitride heterostructure nanosheet catalyst did not decay significantly during the alkaline hydrogen oxidation reaction for up to 2000 cycles, demonstrating its excellent catalytic stability.

[0075] Table 1: Comparative results of the specific activities of the two-dimensional nickel nitride-tungsten nitride heterostructure prepared in Example 1 of the present invention and other nickel-based catalysts reported in the prior art

[0076]

[0077]

[0078] Example 5

[0079] Analysis and comparison of adsorption strength of reaction intermediates:

[0080] The adsorption of the reaction intermediates by the two-dimensional nickel nitride-tungsten nitride heterostructure, nickel nitride and tungsten nitride nanosheets prepared in Example 1, Comparative Example 1 and Comparative Example 2 is compared. Figure 10 As shown in a in the figure, the Gibbs free energy values ​​of hydrogen adsorption on the surfaces of nickel nitride-tungsten nitride heterostructure, nickel nitride and tungsten nitride nanosheets are -0.161eV, -0.592eV and -0.353eV, respectively. The Gibbs free energy value of hydrogen adsorption on the surface of nickel nitride is higher than that of tungsten nitride, and hydrogen species will be preferentially adsorbed on the surface of nickel nitride. The Gibbs free energy value of hydrogen adsorption on the surface of nickel nitride-tungsten nitride heterostructure is lower than that of nickel nitride, indicating that the adsorption of hydrogen species by nickel nitride-tungsten nitride heterostructure is significantly weakened, which is conducive to promoting the alkaline hydrogen oxidation reaction. At the same time, as Figure 10 As shown in Figure 2(b), tungsten nitride has a relatively stronger binding energy for hydroxyl species than nickel nitride. Therefore, hydroxyl species tend to adsorb on the tungsten nitride surface. The adsorption strength of hydroxyl species on the surface of the nickel nitride-tungsten nitride heterostructure is significantly higher than that of tungsten nitride, indicating that the nickel nitride-tungsten nitride heterostructure significantly enhances the adsorption of hydroxyl species, which is beneficial for promoting the alkaline hydrogen oxidation reaction.

[0081] The above embodiments are merely examples. For example, the amount of NiW-OH precursor nanosheets used in step (2) of the preparation process can be adjusted according to actual needs (e.g., 20 mg to 30 mg). For another example, in addition to using pure ammonia, ammonia can also be used in combination with a carrier gas (the carrier gas can be, for example, an inert gas such as nitrogen or argon).

[0082] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets, characterized in that: The following steps are involved: (1) Mixing a nickel source material and a tungsten source material with a solution containing an organic solvent and aqueous ammonia, and heating and stirring the resulting mixture in an oil bath to obtain NiW-OH precursor nanosheets; Wherein, the nickel source material is selected from one or more of nickel nitrate, nickel chloride, and nickel acetate; the tungsten source material is selected from one or more of ammonium metatungstate and ammonium tungstate; and the organic solvent is selected from one or more of ethylene glycol and diethylene glycol. (2) placing the NiW-OH precursor nanosheet obtained in step (1) in an atmosphere containing ammonia and heating it for reduction and nitridation reaction, thereby obtaining a two-dimensional nickel nitride-tungsten nitride heterostructure nanosheet; In step (1), the molar ratio of the nickel element contained in the nickel source material to the tungsten element contained in the tungsten source material is (4-8):1; In step (2), the reduction and nitridation reaction is carried out by heating, specifically heating to 400°C-450°C, and the reaction time is 2-3 hours.

2. The preparation method according to claim 1, wherein In step (1), the molar ratio of the nickel element contained in the nickel source material to the tungsten element contained in the tungsten source material is 4:1, 6:1 or 8:

1.

3. The preparation method according to claim 1, wherein In step (1), the solution containing the organic solvent and ammonia water is equal to a mixed solution obtained by mixing deionized water, the organic solvent and concentrated ammonia water in a volume ratio of 5:45:2; wherein the mass percentage concentration of the concentrated ammonia water is 25% to 28%.

4. The preparation method according to claim 1, wherein In step (1), the heating and stirring under oil bath conditions is specifically heating and stirring at an oil bath temperature of 150° C. for 30 min.

5. The preparation method according to claim 1, wherein In step (2), the atmosphere containing ammonia is specifically a flowing ammonia atmosphere, and the flow rate of the ammonia is 100-200 sccm.

6. The preparation method according to claim 1, wherein In step (2), the heating rate used for heating is 5-10 °C / min.

7. The preparation method according to claim 1, wherein The molar ratio of the nickel element contained in the nickel source material and the tungsten element contained in the tungsten source material in step (1) is 6:1; In step (2), the heating is performed to carry out reduction and nitridation reaction, specifically heating to 400°C and reacting for 2 hours.

8. A two-dimensional nickel nitride-tungsten nitride heterostructure nanosheet prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the two-dimensional nickel nitride-tungsten nitride heterostructure nanosheets as claimed in claim 8 as a catalyst in the anode hydrogen oxidation reaction of an anion exchange membrane fuel cell.

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