NiMo nitride-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses a NiMo nitride-based catalyst and a preparation method and application thereof, and belongs to the technical field of electrolyzed water hydrogen production catalysts.The NiMo nitride-based catalyst is characterized in that foamed nickel serves as a substrate, NiMo nitride microcrystals grow on the surface of the foamed nickel in situ, at least one noble metal elementary substance of ruthenium, osmium and iridium is loaded on the surface of the NiMo nitride microcrystals, and the NiMo nitride-based catalyst is prepared. The NiMo nitride-based catalyst is obtained. The microtopography of the NiMo nitride-based catalyst provided by the invention is an in-situ growth micron-sized nickel-molybdenum nitride microcrystal square column, a noble metal simple substance is attached to the surface of the microcrystal square column, and various catalytic active sites of the noble metal simple substance and the nickel-molybdenum nitride are distributed and constructed on a foamed nickel matrix, so that the catalytic efficiency of the catalyst is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts for hydrogen production by electrolyzing water, and particularly relates to a NiMo nitride-based catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] As a clean energy carrier, hydrogen energy has core advantages such as zero carbon emission and high energy density. The technology of electrolyzing seawater to produce hydrogen uses seawater as raw material. Seawater has rich reserves and low prices, making it an ideal raw material for hydrogen production. Moreover, the hydrogen production process by electrolyzing water is pollution-free, the product purity is high, and it has strong adaptability, and is expected to be put into large-scale industrial production. Currently, the mature commercial electrolyzing seawater hydrogen production system requires many additional investments, which greatly increases the cost and limits large-scale commercial promotion. In addition to the cost problem, the electrolysis raw material problem is also a major problem restricting commercial promotion. Whether it is an alkaline electrolytic cell or a proton exchange membrane electrolytic cell, high-purity water is used as the electrolysis raw material. If most of the hydrogen energy in the world is produced by electrolyzing high-purity water in the future, the consumption problem of fresh water resources cannot be ignored. In contrast, the reserves of seawater account for 96.5% of the total reserves of the earth's water resources, and the reserves are almost infinite.

[0003] However, compared with the technology of electrolyzing fresh water, the technology of electrolyzing seawater faces many problems, such as the poisoning of the electrode active sites by chloride ions, the low activity of the catalysts used in electrolyzing seawater, and the lack of long-term stability. Therefore, developing catalysts with high activity and high stability is the top priority for the development of electrolyzing seawater to produce hydrogen. Currently, noble metal-based catalysts are generally used for the anodes (HER side) of commercial electrolytic cells, and noble metals platinum and iridium are generally used for the cathodes (OER side). These noble metals have limited reserves and high prices, which increase the cost of their commercial applications. Summary of the Invention

[0004] The present invention provides a NiMo nitride-based catalyst, a preparation method thereof, and an application thereof, effectively solving the technical problems of the existing catalysts for electrolyzing seawater to produce hydrogen, such as high cost, low efficiency, and poor stability. The present invention provides a NiMo nitride catalyst modified with trace noble metals. This catalyst can be used for catalyzing both the hydrogen evolution reaction at the anode and the oxygen evolution reaction at the cathode, and this catalyst can achieve an ultra-long stability of more than 2100 hours on the HER side and more than 2600 hours on the OER side under the conditions of harsh alkaline seawater.

[0005] The first object of the present invention is to provide a NiMo nitride-based catalyst, with nickel foam as the substrate, growing NiMo nitride microcrystals on the surface of the nickel foam, and loading noble metal single substances on the surface of the NiMo nitride microcrystals; the noble metal single substances are at least one of ruthenium, osmium, and iridium.

[0006] As a preferred embodiment, based on the mass of the NiMo nitride-based catalyst, the loading amount of the noble metal element is 0.015% - 0.02%.

[0007] As a preferred embodiment, the NiMo nitride microcrystals are square columnar with a size of 500 nm - 1 μm.

[0008] The second object of the present invention is to provide a method for preparing the above NiMo nitride-based catalyst, comprising the following steps: Using a nickel source and a molybdenum source as raw materials, a NiMo mixed salt solution is prepared.

[0009] Placing nickel foam in the NiMo mixed salt solution, a hydrothermal reaction occurs at 180°C - 220°C, and nickel molybdate crystals grow in-situ on the surface of the nickel foam to obtain a precursor.

[0010] Under an inert atmosphere, the precursor and dicyandiamide crystals are heated to 400°C - 600°C and annealed to generate NiMo nitride microcrystals, obtaining a NiMo nitride precursor.

[0011] The NiMo nitride precursor is immersed in a noble metal salt solution to obtain noble metal elements and attach them to the surface of the NiMo nitride precursor, obtaining a NiMo nitride-based catalyst.

[0012] As a preferred embodiment, the concentration of the nickel source in the NiMo mixed salt solution is 0.2 mmol / mL - 5 mmol / mL, and the molar ratio of the nickel source to the molybdenum source is 1:1 - 15.

[0013] As a preferred embodiment, the noble metal salt solution is at least one of a soluble ruthenium salt, a soluble osmium salt, and a soluble iridium salt.

[0014] As a preferred embodiment, the concentration of the noble metal salt solution is 0.5 mmol / L - 10 mmol / L.

[0015] As a preferred embodiment, the time of the hydrothermal reaction is 5 h - 8 h, the time of the annealing is 1 h - 3 h, and the time of the immersion is 1 h - 3 h.

[0016] As a preferred embodiment, the nickel foam is sequentially ultrasonically treated in an acid solution with a concentration of 3 mol / L - 10 mol / L and an organic solvent, washed with absolute ethanol to obtain clean nickel foam, and then the crystallized nickel foam is placed in the NiMo mixed salt solution.

[0017] The third object of the present invention is to provide an application of the above NiMo nitride-based catalyst in hydrogen production by electrolyzing water.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a NiMo nitride-based catalyst, with nickel foam as the substrate, on the surface of the nickel foam, NiMo nitride microcrystals are in-situ grown, and at least one noble metal element of ruthenium, osmium, and iridium is loaded on the surface of the NiMo nitride microcrystals to obtain the NiMo nitride-based catalyst. The microscopic morphology of the NiMo nitride-based catalyst provided by the present invention is micron-scale nickel molybdenum nitride microcrystal square columns grown in-situ, and trace amounts of noble metal elements are attached to the surface of the microcrystal square columns. The distribution of various catalytic active sites of the noble metal elements and nickel molybdenum nitride is constructed on the nickel foam matrix, significantly improving the catalytic efficiency of the catalyst.

[0019] When the NiMo nitride-based catalyst prepared by the present invention is in 1 M KOH seawater, at a current density of 10 mA cm -2 , the overpotential on the HER side is only 8.93 mV, and the overpotential on the OER side is only 174.11 mV. The NiMo nitride-based catalyst provided by the present invention is a bifunctional catalyst, which can be used for the catalysis of both anodic hydrogen evolution reaction and cathodic oxygen evolution reaction. In alkaline seawater, the HER stability exceeds 2100 h (about 88 days), and the OER stability exceeds 2600 h (about 108 days), showing the characteristics of both high stability and high activity.

[0020] In terms of overall seawater electrolysis, the NiMo nitride-based catalyst provided by the present invention has better electrocatalytic performance than commercial RuO2 and Pt / C electrodes, and can be used in the field of large-current electrolysis of seawater for hydrogen production.

[0021] The preparation method of the NiMo nitride-based catalyst provided by the present invention is simple and has low cost. Description of the Drawings

[0022] Figure 1 SEM image of RuNiMoN prepared in Example 1 of the present invention at a scale of 25 μm.

[0023] Figure 2 SEM image of RuNiMoN prepared in Example 1 of the present invention at a scale of 5 μm.

[0024] Figure 3 SEM image of RuNiMoN prepared in Example 1 of the present invention at a scale of 500 nm.

[0025] Figure 4 Comparison chart of the XRD characterization results of RuNiMoN prepared in Example 1 of the present invention with the standard card.

[0026] Figure 5The hydrogen evolution polarization curves of the RuNiMoN prepared in Example 1 of the present invention and the catalysts of the comparative examples in seawater.

[0027] Figure 6 The change curve of potential with time under a constant current of 500 mA cm for the RuNiMoN prepared in Example 1 of the present invention in seawater. -2 The graph of the change of potential with time under a constant current.

[0028] Figure 7 The oxygen evolution polarization curves of the RuNiMoN prepared in Example 1 of the present invention and the catalysts of the comparative examples in seawater.

[0029] Figure 8 The change curve of potential with time under a constant current of 500 mA cm for the RuNiMoN prepared in Example 1 of the present invention in seawater. -2 The graph of the change of potential with time under a constant current.

[0030] Figure 9 The polarization curve of the RuNiMoN prepared in Example 1 of the present invention as both the cathode and the anode. Detailed implementation manners

[0031] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention will be further described below with reference to specific embodiments, but the embodiments cited do not limit the present invention. The following test methods and detection methods are all conventional methods unless otherwise specified; the reagents and raw materials are all commercially available unless otherwise specified.

[0032] Aiming at the technical problems that the catalysts used in the existing electrolysis of seawater have low activity and insufficient long-term stability; and the anodes (HER side) of commercial electrolyzers generally use noble metal-based catalysts, and the cathodes (OER side) generally use noble metals such as platinum and iridium with high prices. The present invention provides a NiMo nitride-based catalyst and its preparation method and application.

[0033] The technical solution of the present invention will be described in detail below.

[0034] The present invention provides a NiMo nitride-based catalyst, with nickel foam as the substrate, NiMo nitride microcrystals are grown on the surface of the nickel foam, and noble metal simple substances are loaded on the surface of the NiMo nitride microcrystals; the noble metal simple substances are at least one of ruthenium, osmium and iridium.

[0035] In the above technical solution, the NiMo nitride-based catalyst has micron-scale nickel molybdenum nitride microcrystal columns grown in-situ on the nickel foam substrate, and trace noble metal simple substances are attached to the surface of the microcrystal columns. The multiple catalytic active sites of the noble metal simple substances and nickel molybdenum nitride are distributed and constructed on the nickel foam matrix, significantly improving the catalytic efficiency of the catalyst.

[0036] In order to improve the catalytic performance of the NiMo nitride-based catalyst while reducing the production cost, based on the mass of the NiMo nitride-based catalyst, the loading amount of the noble metal element is 0.015% - 0.02%. The NiMo nitride-based catalyst modified with trace noble metals in the present invention has both cost advantages and excellent catalytic performance.

[0037] It should be noted that the NiMo nitride microcrystals are square columnar with a size of 500 nm - 1 μm.

[0038] The second object of the present invention is to provide a preparation method of the above-mentioned NiMo nitride-based catalyst, which includes the following steps: Using nickel source and molybdenum source as raw materials, a NiMo mixed salt solution is prepared.

[0039] Placing nickel foam in the NiMo mixed salt solution, a hydrothermal reaction occurs at 180°C - 220°C, and nickel molybdate crystals grow in-situ on the surface of the nickel foam to obtain a precursor.

[0040] Under an inert atmosphere, the precursor and dicyandiamide crystals are heated to 400°C - 600°C and annealed to generate NiMo nitride microcrystals, obtaining a NiMo nitride precursor.

[0041] The NiMo nitride precursor is immersed in a noble metal salt solution to obtain noble metal elements and attach them to the surface of the NiMo nitride precursor, obtaining a NiMo nitride-based catalyst.

[0042] In order to further improve the activity and long-term stability of the catalyst in seawater, the concentration of the nickel source in the NiMo mixed salt solution is 0.2 mmol / mL - 5 mmol / mL, and the molar ratio of the nickel source to the molybdenum source is 1:1 - 15. When the molar amount of the molybdenum source is less than 1 or greater than 15 defined here, it will lead to poor activity and long-term stability of the catalyst in seawater electrolyte.

[0043] It should be noted that the noble metal salt solution is at least one of soluble ruthenium salt, soluble osmium salt, and soluble iridium salt, and the concentration of the noble metal salt solution is 0.5 mmol / L - 10 mmol / L.

[0044] To prepare a catalyst with better performance, the hydrothermal reaction time is 5 h to 8 h, the annealing time is 1 h to 3 h, and the soaking time is 1 h to 3 h. For the hydrothermal reaction, if the reaction temperature is less than 180 °C for no more than 5 h, the reaction will be incomplete and the expected product cannot be obtained. If the reaction temperature is higher than 220 °C for more than 8 h, the self-grown crystals will fall off from the substrate surface, preventing the attachment of NiMo nitride microcrystals to the surface of nickel foam and rendering them unable to play their corresponding role. For the annealing treatment, annealing at a temperature less than 400 °C for less than 1 h results in incomplete annealing and the target product cannot be obtained; if annealing at a temperature of 600 °C for more than 3 h, the target product cannot be obtained either.

[0045] It should be noted that before the nickel foam used in the present invention is placed in the NiMo mixed salt solution, the nickel foam needs to be purified, specifically: the nickel foam is ultrasonically treated in an acid solution with a concentration of 3 mol / L to 10 mol / L and an organic solvent in sequence, washed with absolute ethanol, and clean nickel foam is obtained. Then, the crystallized nickel foam is placed in the NiMo mixed salt solution.

[0046] The following is a specific description of the content of the present invention through the following examples and comparative examples.

[0047] Example 1 A preparation method of a NiMo nitride-based catalyst includes the following steps: S1. After cutting the nickel foam into a size of 3 cm × 3 cm, it is ultrasonically cleaned in acetone and 6 M hydrochloric acid for 10 min in sequence. The role of hydrochloric acid is to wash away the oxide layer on the surface of the nickel foam, and the role of acetone is to degrease the nickel foam. Then, it is washed with ethanol and deionized water to remove the residual acetone and hydrochloric acid, and after cleaning, it is taken out to obtain clean nickel foam.

[0048] S2. Dissolve 1.2 mmol of Ni(NO3)2·6H2O and 0.3 mmol of (NH4)2MoO4·4H2O in 30 mL of deionized water, place it on a magnetic stirrer and stir for 30 min to fully dissolve to obtain a homogeneous solution, and obtain a NiMo mixed salt solution. Transfer the NiMo mixed salt solution to a hydrothermal synthesis reactor, immerse the clean nickel foam in the NiMo mixed salt solution, seal the reactor, and carry out a hydrothermal reaction at 200 °C for 6 h. After the reaction is completed, wash the product, and microscale square-columnar nickel molybdate crystals grow in-situ on the surface of the nickel foam to obtain a precursor.

[0049] S3. Place the precursor downstream of the high-temperature furnace, place dicyandiamide crystals upstream of the high-temperature furnace, and raise the temperature to 500 °C in an argon atmosphere and maintain it for 2 h for annealing treatment to generate NiMo nitride microcrystals and obtain a NiMo nitride precursor.

[0050] S4, immersing the NiMo nitride precursor in a 0.782 mmol / L ruthenium chloride solution, taking it out after immersion for 1 hour, and obtaining a NiMo nitride-based catalyst, wherein the loading amount of ruthenium on the surface of the NiMo nitride-based catalyst is 0.016%, recorded as RuNiMoN.

[0051] Example 2 A method for preparing a NiMo nitride-based catalyst comprises the following steps: S1, cut the nickel foam into a size of 3cm×3cm and then place it in acetone and 6M hydrochloric acid for ultrasonic cleaning for 10min. The role of hydrochloric acid is to wash away the oxide layer on the surface of the nickel foam, and the role of acetone is to degrease the nickel foam. Then use ethanol and deionized water to wash away the residual acetone and hydrochloric acid. After cleaning, take it out to obtain a clean nickel foam.

[0052] S2, dissolve 1.2mmol Ni(NO3)2·6H2O and 0.3mmol (NH4)2MoO4·4H2O in 30mL deionized water, place on a magnetic stirrer and stir for 30min to fully dissolve to obtain a uniform solution, obtain a NiMo mixed salt solution, transfer the NiMo mixed salt solution to a hydrothermal synthesis reactor, immerse the clean nickel foam in the NiMo mixed salt solution, seal the reactor, and perform hydrothermal reaction at 200℃ for 6h. After the reaction is completed, clean the product, and grow micrometer-sized square columnar nickel molybdate crystals in situ on the surface of the nickel foam to obtain a precursor.

[0053] S3, placing the precursor downstream of the high-temperature furnace, taking the dicyandiamide crystal and placing it upstream of the high-temperature furnace, heating to 500° C. in an argon atmosphere and maintaining it for 2 hours for annealing treatment to generate NiMo nitride microcrystals, and obtaining a NiMo nitride precursor.

[0054] S4, immersing the NiMo nitride precursor in a 0.765 mmol / L osmium chloride solution, taking it out after immersion for 1 hour, to obtain a NiMo nitride-based catalyst, wherein the loading amount of osmium on the surface of the NiMo nitride-based catalyst is 0.018%, recorded as OsNiMoN.

[0055] Example 3 A method for preparing a NiMo nitride-based catalyst comprises the following steps: S1, cut the nickel foam into a size of 3cm×3cm and then place it in acetone and 6M hydrochloric acid for ultrasonic cleaning for 10min. The role of hydrochloric acid is to wash away the oxide layer on the surface of the nickel foam, and the role of acetone is to degrease the nickel foam. Then use ethanol and deionized water to wash away the residual acetone and hydrochloric acid. After cleaning, take it out to obtain a clean nickel foam.

[0056] S2, dissolve 1.2mmol Ni(NO3)2·6H2O and 0.3mmol (NH4)2MoO4·4H2O in 30mL deionized water, place on a magnetic stirrer and stir for 30min to fully dissolve to obtain a uniform solution, obtain a NiMo mixed salt solution, transfer the NiMo mixed salt solution to a hydrothermal synthesis reactor, immerse the clean nickel foam in the NiMo mixed salt solution, seal the reactor, and perform hydrothermal reaction at 200℃ for 6h. After the reaction is completed, clean the product, and grow micrometer-sized square columnar nickel molybdate crystals in situ on the surface of the nickel foam to obtain a precursor.

[0057] S3, placing the precursor downstream of the high-temperature furnace, taking the dicyandiamide crystal and placing it upstream of the high-temperature furnace, heating to 500° C. in an argon atmosphere and maintaining it for 2 hours for annealing treatment to generate NiMo nitride microcrystals, and obtaining a NiMo nitride precursor.

[0058] S4, immersing the NiMo nitride precursor in a 2.13 mmol / L iridium chloride solution, taking it out after immersion for 1 hour, and obtaining a NiMo nitride-based catalyst, wherein the loading amount of iridium on the surface of the NiMo nitride-based catalyst is 0.019%, recorded as IrNiMoN.

[0059] In order to further illustrate the effect of the present invention, the present invention also sets a comparative example, as follows: Comparative Example 1 Compared with Example 1, the difference is that the treatment of S4 is not performed, that is, the precious metal salt solution is not used for immersion.

[0060] A method for preparing a NiMo nitride catalyst comprises the following steps: S1, cut the nickel foam into a size of 3cm×3cm and then place it in acetone and 6M hydrochloric acid for ultrasonic cleaning for 10min. The role of hydrochloric acid is to wash away the oxide layer on the surface of the nickel foam, and the role of acetone is to degrease the nickel foam. Then use ethanol and deionized water to wash away the residual acetone and hydrochloric acid. After cleaning, take it out to obtain a clean nickel foam.

[0061] S2, dissolve 1.2mmol Ni(NO3)2·6H2O and 0.3mmol (NH4)2MoO4·4H2O in 30mL deionized water, place on a magnetic stirrer and stir for 30min to fully dissolve to obtain a uniform solution, obtain a NiMo mixed salt solution, transfer the NiMo mixed salt solution to a hydrothermal synthesis reactor, immerse the clean nickel foam in the NiMo mixed salt solution, seal the reactor, and perform hydrothermal reaction at 200℃ for 6h. After the reaction is completed, clean the product, and grow micrometer-sized square columnar nickel molybdate crystals in situ on the surface of the nickel foam to obtain a precursor.

[0062] S3. Place the precursor downstream of the high-temperature furnace, put the dicyandiamide crystal upstream of the high-temperature furnace, heat it to 500 °C in an argon atmosphere and hold for 2 h for annealing treatment to generate NiMo nitride microcrystals, and obtain a NiMo nitride catalyst, denoted as NiMoN.

[0063] Comparative Example 2 Compared with Example 1, the difference is that the treatments of S3 and S4 are not carried out, that is, annealing is not carried out and soaking with a noble metal salt solution is not carried out.

[0064] A preparation method of a NiMo-based catalyst includes the following steps: S1. Cut the nickel foam into a size of 3 cm × 3 cm, and then place it in acetone and 6 M hydrochloric acid in turn and ultrasonically clean for 10 min. The function of hydrochloric acid is to wash away the oxide layer on the surface of the nickel foam, and the function of acetone is to degrease the nickel foam. Then wash away the residual acetone and hydrochloric acid with ethanol and deionized water, take it out after cleaning, and obtain clean nickel foam.

[0065] S2. Dissolve 1.2 mmol of Ni(NO3)2·6H2O and 0.3 mmol of (NH4)2MoO4·4H2O in 30 mL of deionized water, place it on a magnetic stirrer and stir for 30 min to fully dissolve to obtain a homogeneous solution, and obtain a NiMo mixed salt solution. Transfer the NiMo mixed salt solution to a hydrothermal synthesis reactor, immerse the clean nickel foam in the NiMo mixed salt solution, seal the reactor, and carry out hydrothermal reaction at 200 °C for 6 h. After the reaction is completed, clean the product, and nickel molybdate crystals with a micron-sized square columnar shape grow in-situ on the surface of the nickel foam to obtain a NiMo-based catalyst, denoted as NiMoO4.

[0066] Comparative Example 3 Compared with Example 1, the difference is that only clean nickel foam is used as the catalyst.

[0067] A preparation method of a nickel foam catalyst includes the following steps: Cut the nickel foam into a size of 3 cm × 3 cm, and then place it in acetone and 6 M hydrochloric acid in turn and ultrasonically clean for 10 min. The function of hydrochloric acid is to wash away the oxide layer on the surface of the nickel foam, and the function of acetone is to degrease the nickel foam. Then wash away the residual acetone and hydrochloric acid with ethanol and deionized water, take it out after cleaning, and obtain clean nickel foam.

[0068] Comparative Example 4 A preparation method of a Pt / C catalyst includes the following steps: S1. Mix 60 μL of nafion, 540 μL of deionized water and 400 μL of absolute ethanol, then add 20 mg of commercial Pt / C, and ultrasonically process the mixture for 10 min to obtain a mixed slurry.

[0069] S2, 200 μL of the mixed slurry was dropped onto a clean nickel foam of 1.5 cm × 1 cm, and then the nickel foam was placed in a vacuum drying oven and vacuum dried at 60 °C for 12 h to obtain the Pt / C catalyst.

[0070] Comparative Example 5 A preparation method of a RuO2 catalyst includes the following steps: S1, 60 μL of nafion, 540 μL of deionized water and 400 μL of absolute ethanol were mixed, and then 20 mg of commercial RuO2 was added. After mixing, it was ultrasonically treated for 10 min to obtain a mixed slurry.

[0071] S2, 200 μL of the mixed slurry was dropped onto a clean nickel foam of 1.5 cm × 1 cm, and then the nickel foam was placed in a vacuum drying oven and vacuum dried at 60 °C for 12 h to obtain the RuO2 catalyst.

[0072] For the NiMo nitride-based catalyst prepared in the above-mentioned examples, namely RuNiMoN, the morphology and performance of the catalysts prepared in Comparative Examples 1 to 5 were characterized and detected, and the results are as follows.

[0073] Figure 1 、 Figure 2 and Figure 3 are SEM photos of different scales of RuNiMoN prepared in Example 1. It can be seen from the figure that: micron-scale square-columnar catalysts are distributed on the nickel foam substrate, and small particles can be observed adhering to the surface of the microcrystalline square columns from the high-magnification SEM photos.

[0074] Figure 4 is the X-ray diffraction pattern of RuNiMoN prepared in Example 1 of the present invention. By comparing with the known phase spectrum, the phase composition of the material was determined. The RuNiMoN prepared in Example 1 is (Mo 0.8 Ni 0.2 )N and Ni(MoO4)(H2O) 0.7 .

[0075] Using the NiMo nitride-based catalyst RuNiMoN prepared in Example 1, NiMoN prepared in Comparative Example 1, NiMoO4 / NF prepared in Comparative Example 2, clean nickel foam prepared in Comparative Example 3, and Pt / C catalyst prepared in Comparative Example 4 as hydrogen evolution catalysts respectively, linear sweep voltammetry (LSV) tests were carried out. The specific test method is as follows: A three-electrode test system composed of a working electrode, a counter electrode and a reference electrode was connected to an electrochemical workstation and scanned between -0.8 V and -3 V at a scan rate of 2 mV / s. The hydrogen evolution polarization curves of each catalyst in seawater are as Figure 5As shown, by comparison, in harsh alkaline seawater conditions, the performance of RuNiMoN prepared in Example 1 is superior to that of the catalysts in the comparative examples, showing excellent performance of 8.93 mV@10 mA cm -2 in alkaline seawater. It should be emphasized that RuNiMoN prepared in Example 1 exhibits intrinsic activity superior to that of commercial Pt / C, and its performance is far better than that of commercial Pt / C at high current densities. The alkaline seawater used in the test was prepared by adding 1 mol of KOH to a 1-L volumetric flask and making up the volume with seawater.

[0076] Figure 6 Figure showing the variation of the potential with time of the NiMo nitride-based catalyst RuNiMoN prepared in Example 1 of the present invention as a hydrogen evolution catalyst in alkaline seawater under a constant current of 500 mA cm -2 As can be seen from Figure 6 it, the NiMo nitride-based catalyst RuNiMoN prepared in Example 1 can stably operate for more than 2100 hours under the condition of 500 mA cm -2 in alkaline seawater, and its performance hardly decays significantly, indicating that the NiMo nitride-based catalyst RuNiMoN prepared in Example 1 has excellent stability as a hydrogen evolution catalyst.

[0077] Linear sweep voltammetry (LSV) tests were respectively carried out using the NiMo nitride-based catalyst RuNiMoN prepared in Example 1, NiMoN prepared in Comparative Example 1, NiMoO4 / NF prepared in Comparative Example 2, clean nickel foam prepared in Comparative Example 3, and RuO2 catalyst prepared in Comparative Example 5 as hydrogen evolution catalysts. The specific test method is as follows: A three-electrode test system composed of a working electrode, a counter electrode, and a reference electrode was connected to an electrochemical workstation and scanned between 0 V and 2.2 V at a scan rate of 2 mV / s to obtain the hydrogen evolution polarization curves of each catalyst in seawater as Figure 7 shown. By comparison, in harsh alkaline seawater conditions, the performance of RuNiMoN prepared in Example 1 is superior to that of the catalysts in the comparative examples, showing excellent performance of 174.11 mV@10 mA cm -2 in alkaline seawater. It should be emphasized that the NiMo nitride-based catalyst RuNiMoN prepared in Example 1 exhibits intrinsic activity superior to that of commercial RuO2, and its performance is far better than that of commercial RuO2 at high current densities.

[0078] Figure 8 Figure showing the variation of the potential with time of the NiMo nitride-based catalyst RuNiMoN prepared in Example 1 as an oxygen evolution catalyst in alkaline seawater under a constant current of 500 mA cm -2 As can be seen from Figure 8It can be seen that the NiMo nitride-based catalyst RuNiMoN prepared in Example 1 can stably operate for more than 2600 hours under the condition of 500 mA cm -2 in alkaline seawater, and its performance hardly decays significantly, indicating that the NiMo nitride-based catalyst RuNiMoN prepared in Example 1 has excellent stability as an oxygen evolution catalyst.

[0079] The linear sweep voltammetry (LSV) test was carried out using the NiMo nitride-based catalyst RuNiMoN prepared in Example 1 as both the oxygen evolution side and the hydrogen evolution side catalysts. At the same time, the LSV test was carried out using the Pt / C catalyst prepared in Comparative Example 4 as the hydrogen evolution side catalyst and the RuO2 catalyst prepared in Comparative Example 5 as the oxygen evolution side catalyst. The obtained polarization curve diagram is as Figure 9 shown. It can be seen from Figure 9 that in alkaline seawater, the NiMo nitride-based catalyst RuNiMoN prepared in Example 1 is not inferior to the catalysts of Comparative Example 4 and Comparative Example 5.

[0080] Among precious metals, ruthenium (Ru), a member of the platinum group metals, has received great attention in the field of electrocatalysis. It has shown quite excellent performance in the field of electrolytic seawater hydrogen evolution. At the same time, the price of ruthenium ($275 per ounce) is much lower than that of platinum ($1094 per ounce), and much lower than platinum group precious metals such as iridium, making it have great application prospects in the field of electrolytic seawater hydrogen evolution. The NiMo nitride-based catalyst RuNiMoN of the present invention is a nickel molybdenum nitride catalyst, and its electrocatalytic performance is further improved by surface modification with trace amounts of precious metal ruthenium, which not only greatly reduces the use of precious metals, but also ensures the high activity of the catalyst. This catalyst also has excellent long-term stability and can be used as both the cathode and anode catalysts in the field of electrolytic water hydrogen production, which can solve the problems of high cost, insufficient activity, poor stability of catalysts in the current electrolytic water hydrogen production field and hydrogen production by electrolysis of seawater.

[0081] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A NiMo nitride-based catalyst, characterized in that, With nickel foam as a substrate, NiMo nitride microcrystals are grown on the surface of the nickel foam, and a noble metal element is loaded on the surface of the NiMo nitride microcrystal; the noble metal element is at least one of ruthenium, osmium and iridium.

2. The NiMo nitride-based catalyst according to claim 1, wherein Based on the mass of the NiMo nitride-based catalyst, the loading amount of the noble metal element is 0.015% to 0.02%.

3. The NiMo nitride-based catalyst according to claim 1, characterized in that, The NiMo nitride microcrystals are in the shape of square columns with a size of 500nm to 1μm.

4. A method for preparing the NiMo nitride-based catalyst according to claim 1, characterized in that, The following steps are involved: A NiMo mixed salt solution is prepared using a nickel source and a molybdenum source as raw materials; The nickel foam is placed in the NiMo mixed salt solution, and a hydrothermal reaction is carried out at 180° C. to 220° C., and nickel molybdate crystals are grown in situ on the surface of the nickel foam to obtain a precursor; In an inert atmosphere, the precursor and dicyandiamide crystals are heated to 400° C. to 600° C., and annealed to generate NiMo nitride microcrystals to obtain a NiMo nitride precursor; The NiMo nitride precursor is immersed in a noble metal salt solution to obtain a noble metal element and attach it to the surface of the NiMo nitride precursor to obtain a NiMo nitride-based catalyst.

5. The preparation method according to claim 4, characterized in that, The concentration of the nickel source in the NiMo mixed salt solution is 0.2 mmol / mL to 5 mmol / mL, and the molar ratio of the nickel source to the molybdenum source is 1:1 to 15.

6. The preparation method according to claim 4, wherein The noble metal salt solution is at least one of a soluble ruthenium salt, a soluble osmium salt and a soluble iridium salt.

7. The preparation method according to claim 4, characterized in that The concentration of the noble metal salt solution is 0.5 mmol / L to 10 mmol / L.

8. The preparation method according to claim 4, wherein The time of the hydrothermal reaction is 5 h to 8 h, the time of the annealing is 1 h to 3 h, and the time of the soaking is 1 h to 3 h.

9. The preparation method according to claim 4, characterized in that, The nickel foam is subjected to ultrasonic treatment in an acid solution and an organic solvent with a concentration of 3 mol / L to 10 mol / L in sequence, and washed with anhydrous ethanol to obtain clean nickel foam, and then the crystallized nickel foam is placed in the NiMo mixed salt solution.

10. Use of the NiMo nitride-based catalyst according to any one of claims 1 to 3 in hydrogen production by water electrolysis.

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