Ni3n / mo2n superlattice material, preparation method and application thereof

Abstract

The application relates to the technical field of nanomaterials, in particular to a Ni3N / Mo2N superlattice material and a preparation method and application thereof. The preparation method comprises the following steps: pretreating nickel foam; mixing nickel salt or cobalt salt, an alkali source, the pretreated nickel foam and deionized water, and carrying out hydrothermal reaction for several hours; respectively cleaning the product grown on the nickel foam under ultrasonic waves with water and ethanol, and drying to obtain CO3 2‑ Interlayer ion alpha-Ni(OH)2; being placed in high-temperature calcination annealing; adding MoO4 2‑ aqueous solution by using the "memory effect" of transition metal layered hydroxide; stirring; filtering and drying to obtain layered nickel hydroxide containing interlayer MoO4 2‑ ; carrying out nitriding treatment in an inert gas atmosphere to obtain the Ni3N / Mo2N superlattice material. The advantages are that the preparation process is simple, the period is short, the process is easy to control, more active sites of the catalytic material are exposed, and the electrocatalytic performance is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, and particularly relates to a Ni3N / Mo2N superlattice material and a preparation method and application thereof. BACKGROUND

[0002] Over-exploitation and utilization of fossil fuels have made energy crisis and environmental pollution problems increasingly serious, and therefore it is urgent to accelerate the development of renewable clean energy. Hydrogen energy has attracted widespread attention due to its high energy density (142 MJ kg -1 ), non-polluting product and other advantages. At present, the most commonly used method is to use clean power resources to catalytically decompose water to produce hydrogen, and the catalysts are generally commercial noble metals (Pt, Pd, Ru, etc.). However, due to the high price, small crustal storage and poor stability, the noble metal catalysts cannot be used on a large scale. Therefore, it is very meaningful to develop inexpensive and highly efficient and stable non-noble metal electrocatalysts.

[0003] Non-noble metal-based electrocatalysts are called important substitutes for noble metal-based catalysts due to their low cost and high catalytic activity. Non-noble metal oxides, carbides, nitrides, phosphides, sulfides and selenides have unique electronic structures and excellent catalytic performance, and have attracted more and more attention in the field of energy. Single-phase non-noble metal nitrides exhibit good electrocatalytic HER / OER performance, and therefore have attracted extensive attention of researchers. At present, the catalytic performance is influenced by regulating the following factors: such as regulating the micro-morphology size, vacancy engineering, substrate, non-metallic doping and the like. Theoretical calculation and experimental exploration have shown that the electrocatalytic performance of double-metal nitrides is better than that of the corresponding single-metal compounds. A simple method is to weaken or strengthen the M-H bond by introducing another metal to change the electronic properties. For example, Zhang et al. doped Ni3N with high-valence Mo, W and V respectively to regulate the electronic structure, improve the water dissociation kinetics and intermediate (proton and hydroxyl) adsorption, and improve the alkaline HER catalytic activity. Another method is to construct a heterojunction interface to improve the catalytic activity. For example, Zhang et al. constructed a Ni 0.2 Mo 0.8 N / Ni composite electrocatalyst, and the Ni sites and Ni 0.2 Mo 0.8 N sites have optimized hydroxyl and proton adsorption energies, respectively, which effectively improve the alkaline HER. Although great progress has been made in the study of double-metal nitrides NiMoN, there is still a gap compared with noble metal-based benchmark catalysts such as Pt, Ru and Ir-based materials, especially the non-uniform electronic structure causes the limited active sites of the catalyst, the slow alkaline hydrogen evolution kinetics, and the long-term stability is still not ideal.

[0004] One possible way to improve the bottleneck of NiMoN catalytic activity and stability is to construct superlattice structure. Li et al. found that the ordered CoMnO@CN superlattice structure can increase the active sites, be beneficial to charge transfer and structural stability, and exhibit excellent catalytic performance in the processes of HER and oxygen evolution reaction (OER); Xiong et al. prepared MoS2 / NiFe-LDH superlattice structure, which exhibits excellent electrocatalytic performance for hydrogen and oxygen production, mainly because the strong electronic coupling effect at the heterojunction interface makes the adsorption energy of the intermediate produced in the catalytic process optimal. Therefore, synthesizing superlattice material is an effective method to improve the electronic structure and catalytic activity, and at present, the experimental study on Ni3N / Mo2N superlattice catalyst is still blank.

[0005] At present, many preparation methods of superlattice materials have been proposed. For example, chemical vapor deposition (CVD) can precisely control the number of stacked layers and stacking mode, and obtain high-quality materials with excellent purity and crystallinity. However, this method has high energy consumption and low yield, which is not conducive to the industrial production of superlattice materials. Liquid flocculation or precipitation method can realize high-yield production of superlattice materials in solution. The biggest challenge is that pollutants bring inevitable impurities or defects on the interface or surface of the material. Therefore, it is necessary to develop advanced preparation technology to efficiently prepare high-purity superlattice materials. Recently, Du et al. prepared AlCrTiNbN / VN superlattice by high-power pulsed magnetron sputtering, but this method has problems such as low target utilization rate, uneven thickness, and poor repeatability in the preparation process. Therefore, it is still necessary to further explore an efficient and low-cost method for preparing Ni3N / Mo2N superlattice material to solve the above problems. SUMMARY

[0006] The present application provides a Ni3N / Mo2N superlattice material and a preparation method and application thereof to solve the above problems.

[0007] The first object of the present application is to provide a Ni3N / Mo2N superlattice material, and the preparation method specifically comprises the following steps:

[0008] S1, pretreating foamed nickel as a base material;

[0009] S2, mixing nickel salt, alkali source, pretreated foamed nickel and deionized water, and hydrothermal reaction at 100-150℃ for 10-15h; after the reaction is completed, the product grown on the foamed nickel is cleaned with water and ethanol under ultrasonic respectively, and dried to obtain α-Ni(OH)2containing CO3 2- intercalated ions;

[0010] S3, calcining and annealing α-Ni(OH)2containing CO3 2- intercalated ions at 300-600℃ for 1-4h; then adding MoO42- , stirring for 6-72 h; filtering, drying to obtain layered nickel hydroxide containing intercalated MoO4 2-

[0011] S4, nitrogenation treatment under inert gas atmosphere to obtain Ni3N / Mo2N superlattice material.

[0012] Preferably, the pretreatment in step S1 is to pretreat the foamed nickel with 5% HCl solution, ethanol and water respectively for 20-30 minutes.

[0013] Preferably, the molar ratio of the nickel salt, the alkali source, the pretreated foamed nickel and the deionized water in step S2 is 0.75:1:1.12:1.3.

[0014] Preferably, the nickel salt is nickel acetate or nickel molybdate; and the alkali source is urea.

[0015] Preferably, the temperature of the hydrothermal reaction in step S2 is 120°C, and the time is 12 h.

[0016] Preferably, the concentration of the aqueous solution of MoO4 2- ion is 0.25-1 M; and the calcination annealing is performed under nitrogen, helium or argon atmosphere.

[0017] Preferably, the inert gas in step S4 is ammonia or nitrogen, the flow rate of the ammonia or nitrogen is 40-60 ccm, the temperature of the nitrogenation treatment is 400-600°C, and the time is 2-7 h.

[0018] The second object of the present application is to provide an electrocatalytic three-electrode system, comprising a working electrode, a counter electrode and a reference electrode, and taking the Ni3N / Mo2N superlattice material as the working electrode; the electrocatalytic three-electrode system is used for testing electrocatalytic hydrogen evolution and oxygen evolution reaction.

[0019] Preferably, the counter electrode is a graphite rod, and the reference electrode is a saturated calomel electrode.

[0020] The third object of the present application is to provide an application of the Ni3N / Mo2N superlattice material in electrolytic water hydrogen evolution and oxygen evolution.

[0021] Compared with the prior art, the present application can achieve the following beneficial effects:

[0022] (1) The present application provides a preparation method of a novel Ni3N / Mo2N superlattice electrocatalytic material, which has the advantages of simple preparation process, low cost, short cycle and easy process control, and is in-situ grown on a foamed nickel substrate, so that the catalytic material exposes more active sites, the strong electronic coupling effect of the interface improves the intermediate adsorption energy, and thus the electrocatalytic performance is effectively improved, so that the catalytic material has good electrocatalytic application prospect.​

[0023] (2) The use of transition metal hydroxide "memory effect", intercalation anion poly-variable structure ordered superlattice electrocatalyst, which effectively increases the interface catalytic active site, thereby improving the performance of the electrocatalyst; the strong interface electron coupling effect is conducive to improving the adsorption energy of the intermediate, further enhancing the catalytic performance; in addition, the good conductivity and large specific surface area of the foam nickel substrate, and the in-situ growth of the catalyst without the use of a binder are conducive to improving the stability of the catalyst and thereby improving the catalytic performance; under the combined action of the above structures, the superlattice material exhibits excellent electrocatalytic performance, and is expected to be widely used in the field of electrocatalysis. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is an SEM spectrum of a Ni3N / Mo2N superlattice material according to an embodiment of the application.

[0025] Figure 2 is an XRD spectrum of a Ni3N / Mo2N superlattice material according to an embodiment of the application.

[0026] Figure 3 is a linear scan curve spectrum according to an embodiment of the application. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0028] In order to make the objectives, technical solutions and advantages of the present application clearer, further detailed descriptions will be made below in combination with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not constitute a limitation on the present application.

[0029] Embodiment 1

[0030] A preparation method of a Ni3N / Mo2N superlattice material, specifically comprising the following steps:

[0031] S1, pretreat 3×3 cm 2 of foam nickel with 5% HCl solution, ethanol and deionized water respectively for 25 min as a substrate material;

[0032] S2, add 0.75 mmol of nickel acetate, (1 mmol) of urea, (3×3 cm 2) and (25 mL) deionized water were mixed and hydrothermally reacted at 120℃ for 12 h; after the reaction was completed, the product grown on the foam nickel was cleaned with water and ethanol under ultrasonic for 10 min, respectively, and dried in a vacuum drying oven at 55℃ for 5 h to obtain layered nickel hydroxide containing CO3 2- intercalated ions of α-Ni(OH)2;

[0033] S3, the layered nickel hydroxide containing CO3 2- was calcined and annealed in a muffle furnace at 400℃ under a nitrogen atmosphere for 2 h to release the intercalated CO3 2- in the form of CO2; after the calcination and annealing, 0.25 M MoO4 2- ion aqueous solution was added and stirred for 6 h; after suction filtration and freeze drying, layered nickel hydroxide containing intercalated MoO4 2- was obtained.

[0034] S4, nitridation treatment was carried out under a flowing ammonia atmosphere, the ammonia flow rate was 40 ccm, the nitridation treatment temperature was 400℃, and the time was 4 h to obtain a Ni3N / Mo2N superlattice material.

[0035] The SEM spectrum of the prepared Ni3N / Mo2N superlattice material is shown in Figure 1 , and the XRD spectrum is shown in Figure 2 .

[0036] Example 2

[0037] The same experimental steps as in Example 1 were used for preparation; the sample in step S3 was calcined and annealed in an argon atmosphere.

[0038] Example 3

[0039] The same experimental steps as in Example 1 were used for preparation; the calcination and annealing temperature in step S3 was changed to 500℃.

[0040] Example 4

[0041] The same experimental steps as in Example 1 were used for preparation; the calcination and annealing temperature in step S3 was changed to 600℃.

[0042] Example 5

[0043] The same experimental steps as in Example 1 were used for preparation; the stirring time of the MoO4 2- ion aqueous solution in step S3 was changed to 18 h.

[0044] Example 6

[0045] The same experimental steps as in Example 1 were used for preparation; the stirring time of the MoO4 2-The concentration of the aqueous solution of ions was kept constant and the stirring time was changed to 24 h.

[0046] Example 7

[0047] The same experimental procedure as in Example 1 was used; in step S3 the MoO4 2- The concentration of the aqueous solution of ions was kept constant and the stirring time was changed to 48 h.

[0048] Example 8

[0049] The same experimental procedure as in Example 1 was used; in step S3 the MoO4 2- The concentration of the aqueous solution of ions was kept constant and the stirring time was changed to 72 h.

[0050] Example 9

[0051] The same experimental procedure as in Example 1 was used; in step S3 the MoO4 2- The concentration of the aqueous solution of ions was changed to 0.5 M.

[0052] Example 10

[0053] The same experimental procedure as in Example 1 was used; in step S3 the MoO4 2- The concentration of the aqueous solution of ions was changed to 0.5 M and the stirring time was changed to 6 h.

[0054] Example 11

[0055] The same experimental procedure as in Example 1 was used; in step S3 the MoO4 2- The concentration of the aqueous solution of ions was changed to 1 M and the stirring time was changed to 6 h.

[0056] Example 12

[0057] The same experimental procedure as in Example 1 was used; in step S3 the MoO4 2- The concentration of the aqueous solution of ions was changed to 1 M and the stirring time was changed to 12 h.

[0058] Example 13

[0059] The same experimental procedure as in Example 1 was used; in step S4 the nitridation temperature was 400 °C, the ammonia flow rate was 40 ccm and the reaction time was 4 h.

[0060] Example 14

[0061] The same experimental procedure as in Example 1 was used; in step S4 the nitridation temperature was 500 °C, the ammonia flow rate was 40 ccm and the reaction time was 3 h.

[0062] Example 15

[0063] The same experimental procedure as in Example 1 was used for the preparation; the nitridation temperature in Step S4 was 600°C, the ammonia flow rate was 40 ccm, and the reaction time was 2 h.

[0064] Example 16

[0065] The same experimental procedure as in Example 1 was used for the preparation; the nitridation temperature in Step S4 was 400°C, the ammonia flow rate was 50 ccm, and the reaction time was 4 h.

[0066] Example 17

[0067] The same experimental procedure as in Example 1 was used for the preparation; the nitridation temperature in Step S4 was 400°C, the ammonia flow rate was 60 ccm, and the reaction time was 4 h.

[0068] Example 18

[0069] The same experimental procedure as in Example 1 was used for the preparation; the sample in Step S3 was annealed by calcination in a helium atmosphere; and the reaction time in Step S4 was 7 h.

[0070] Example 19

[0071] This example provides an electrocatalytic three-electrode system, which comprises a working electrode, a counter electrode and a reference electrode, uses a Ni3N / Mo2N superlattice material as the working electrode, a graphite rod as the counter electrode, and a saturated calomel electrode as the reference electrode; and the electrocatalytic three-electrode system is used for testing electrocatalytic hydrogen evolution and oxygen evolution reactions.

[0072] The Ni3N / Mo2N superlattice materials prepared in the examples were tested using a Shanghai Chenhua CHI660E electrochemical workstation. All potential values were converted into voltages relative to the reversible hydrogen electrode (RHE) by adding 1.05 V. A three-electrode system was used for testing, and all electrolytes were 1 M KOH, 1 M H2SO4, 1 M PBS and 1 M alkaline seawater.

[0073] The results show that the overpotential of the Ni3N / Mo2N superlattice material as the working electrode in 1 M KOH, alkaline seawater and PBS is very small, and when the current density is 10 mA cm -2 , the overpotential is only 22 mV, 35 mV and 50 mV, which is obviously better than that of commercial Pt / C, but the preparation cost is much lower than that of platinum, and it has super-long stability at a large current density.

[0074] Comparative Example 1

[0075] Mo-doped Ni3N was synthesized as follows:

[0076] A piece of foamed nickel (3x3 cm2 ) Pretreated with 5% HCl solution, ethanol and deionized water for 25 minutes, then used as a substrate material; nickel acetate, ammonium molybdate, hexamethylenetetramine and deionized water were mixed in a molar ratio of 2.5:1:1, stirred uniformly and transferred to a reaction kettle containing foamed nickel, heated in an oven at 180℃ for 12 h; after the reaction was completed, it was cooled to room temperature, washed with deionized water and ethanol three times, and finally dried in an oven at 60℃; the dried product was loaded into a high-temperature tube furnace, and Mo-doped Ni3N was synthesized under a flowing ammonia atmosphere.

[0077] Comparative Example 2

[0078] The synthesis of heterojunction Ni3N@Mo2N is as follows:

[0079] Clean foamed nickel (3x3 cm 2 ) as a substrate material, dissolve nickel acetate, ammonium molybdate, ammonium fluoride in 25 mL deionized water in a molar ratio of 2.5:1:1.5, stir for 20 minutes to get a uniform solution, then transfer the solution to a 50 mL Teflon-lined stainless steel autoclave, then heat in an oven at 120℃ for 12 h. After the reaction is completed, it is washed with deionized water and ethanol, and dried in a vacuum drying oven. The product is placed in a high-temperature tube furnace, ammonia is used as the nitrogen source, and high-temperature nitridation is carried out to obtain Ni3N@Mo2N.

[0080] In summary, the present application provides a preparation method of a novel Ni3N / Mo2N superlattice electrocatalytic material. The electrocatalyst has simple preparation process, low cost, short cycle, and easy process control. It is in-situ grown on a foamed nickel substrate. The catalytic material exposes more active sites, and the strong electronic coupling effect at the interface improves the adsorption energy of the intermediate, thereby effectively improving the electrocatalytic performance. Therefore, it has good electrocatalytic application prospect.

[0081] The present application creatively uses the "memory effect" of transition metal hydroxide, and constructs an ordered superlattice electrocatalyst with intercalated anions, which effectively increases the interface catalytic active sites, thereby improving the performance of the electrocatalyst. The strong interface electronic coupling effect is conducive to improving the adsorption energy of the intermediate, further enhancing the catalytic performance. In addition, the foamed nickel substrate has good electrical conductivity and large specific surface area, and the in-situ growth of the catalyst without binder is conducive to improving the stability of the catalyst and thereby improving the catalytic performance. Under the combined action of the above structures, the catalyst exhibits excellent electrocatalytic performance and is expected to be widely used in the field of electrocatalysis.

[0082] It should be understood that the various forms of flow shown above can be used to reorder, add, or remove steps. For example, the steps recited in the present disclosure can be performed in parallel, in series, or in a different order, as long as the desired results of the technical solutions of the present disclosure are achieved, which are not limited herein.

[0083] The above detailed description does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A Ni3N / Mo2N superlattice material, characterized in that, The preparation method specifically comprises the following steps: S1, pretreating the foamed nickel with 5% HCl solution, ethanol and water respectively for 20-30 minutes as a base material; S2, mixing nickel salt, alkali source, pretreated foamed nickel and deionized water, the molar ratio of nickel salt, alkali source, pretreated foamed nickel and deionized water is 0.75:1:1.12:1.3, hydrothermal reaction at 100-150℃ for 10-15h; after the reaction is completed, the product grown on the foamed nickel is cleaned with water and ethanol respectively under ultrasonic, dried, to obtain CO3 2- α-Ni(OH)2intercalated with ions; the nickel salt is nickel acetate or nickel molybdate; the alkali source is urea; S3, adding CO3 2- The intercalated ion α-Ni(OH)2 is calcined at 300-600℃ for 1-4 h; then MoO4 2- aqueous solution is added, and stirred for 6-72 h; filtered and dried to obtain layered nickel hydroxide containing intercalated MoO4 2- aqueous solution is added, and stirred for 6-72 h; filtered and dried to obtain layered nickel hydroxide containing intercalated MoO4 S4, performing nitriding treatment under an inert gas atmosphere at 400 DEG C to obtain a Ni3N / Mo2N superlattice material.

2. The Ni3N / Mo2N superlattice material of claim 1, wherein: The temperature of the hydrothermal reaction in the step S2 is 120 DEG C, and the time is 12 h.

3. The Ni3N / Mo2N superlattice material of claim 2, wherein: The concentration of the aqueous solution of MoO4 2- The concentration of the aqueous solution of MoO4 The concentration of the aqueous solution of MoO4 4. The Ni3N / Mo2N superlattice material of claim 3, wherein: The inert gas in the step S4 is nitrogen, the flow rate of the nitrogen is 40-60 ccm, and the nitriding treatment time is 2-7 h.

5. An electrocatalytic three-electrode system comprising a working electrode, a counter electrode and a reference electrode, characterized in that: The Ni3N / Mo2N superlattice material in claim 1 is used as a working electrode; the electrocatalytic three-electrode system is used for testing electrocatalytic hydrogen evolution and oxygen evolution reaction.

6. An electro-catalytic three-electrode system according to claim 5, characterized in that: The counter electrode is a graphite rod, and the reference electrode is a saturated calomel electrode.

7. Application of the Ni3N / Mo2N superlattice material in claim 1 to water electrolysis for hydrogen evolution and oxygen evolution.

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