Nickel nanocrystal as well as preparation method and application thereof

Abstract

The invention discloses a nickel nanocrystal and a preparation method and application thereof, and the method comprises the following steps: adding a nickel salt, a surfactant and a reducing agent into a solvent, and controlling the reaction atmosphere, reactant concentration and reaction temperature to realize the control of seed crystal types in the nucleation process, so as to realize the synthesis of nickel nanocrystals with different morphologies; the concentration of the nickel salt in the reaction system is 1 * 10 <-4 > mol / L to 8 * 10 <-2 > mol / L; the initial concentration of the surfactant is 0.1 to 10 mol / L; the initial concentration of the reducing agent is 2-100 times of the concentration of the nickel salt. According to the invention, morphology control synthesis of a plurality of nickel nanocrystals is realized by adjusting growth conditions, the variety of nickel nanomaterials is enriched, and a cheap material is provided for the fields of catalysis, sensing, detection and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nano materials, and specifically relates to a nickel nanocrystal and a preparation method and application thereof. Background Art

[0002] Compared with precious metals, the morphology-controlled synthesis of active metal nanomaterials is still a challenge, mainly because active metals are more easily oxidized and lack seed crystal control mechanisms and morphology control methods. How to achieve the synthesis of nanocrystals with specific morphologies has always been an important topic in the research of this type of materials. Nickel nanomaterials have both magnetic and catalytic properties and are widely used in a variety of catalytic reactions. They are abundant in the earth's crust and have low costs, making them an ideal choice for a type of template material.

[0003] To this end, people have developed methods for synthesizing nickel nanomaterials such as seed crystal growth and solvent heat. For example, Huang Xiaoqing et al. used oleylamine, glucose and nickel formate to mix and heat to 230°C to synthesize hexagonal nickel nanospheres (Adv. Funct. Mater. 2023, 33, 2300636); Richard D. Tilley et al. mixed gold nanocrystals (as seeds), hexadecylamine and trioctylphosphine in xylene and introduced 5 atmospheres of hydrogen, reacted at 145°C for 24 hours, and synthesized hexagonal nickel nanotwigs (J. Am. Chem. Soc. 2022, 144, 11094-11098); Li Xingguo et al. mixed nickel formate, oleylamine and oleic acid in octadecene and heated them to 200°C and added carbonyl iron to synthesize nickel nanosheets (Nanotechnology, 2006, 17, 4834-4839).

[0004] These methods have achieved certain success in the synthesis of nickel nanocrystals. However, the morphology of nickel nanocrystals is still scarce, and morphologies such as decahedron and tetrahedron have not been reported, mainly because the seed crystal structure is difficult to control during nickel nucleation.

[0005] The formation of metal nanocrystals in a homogeneous solution is mainly divided into three steps (Small, 2011, 7, 2685–2702. Chem. Sci., 2020, 11, 11394-11403): (1) The metal precursor is reduced to zero-valent metal atoms; (2) When the concentration of metal atoms in the solution exceeds the supersaturation concentration, the metal atoms begin to nucleate and form small seeds; (3) The deposition of metal atoms on the seeds leads to their growth and the formation of nanocrystals. At present, there is a lack of seed types for nickel nanocrystals, that is, the research on the second step of forming nanocrystals is limited, which limits the acquisition of nanocrystals with different morphologies through crystal growth on this basis. Therefore, the development of the seed crystal regulation mechanism of nickel nanocrystals is of great significance to achieve the diversification of nickel nanocrystal morphology.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0007] The purpose of the present invention is to provide a nickel nanocrystal and a preparation method and application thereof, so as to solve the problem of the lack of morphology of existing nickel nanocrystals and realize the controllable synthesis of nickel nanocrystals with different morphologies.

[0008] In order to achieve the above-mentioned object, the present invention provides a method for preparing nickel nanocrystals, which comprises: adding nickel salt, surfactant and reducing agent into a solvent and placing them in a reaction atmosphere, controlling the reaction atmosphere, reactant concentration and reaction temperature, thereby controlling the supersaturated concentration of zero-valent nickel in the solution by controlling the reaction rate, so as to control the formation of single crystal, stacking fault or multiple dislocation structure seed crystals of zero-valent nickel, realize the control of seed crystal type in the nucleation process, and obtain nickel nanocrystals with different morphologies; wherein the concentration of the nickel salt is 1×10 -4 mol / L~8×10 -2 mol / L; the initial concentration of the surfactant is 0.1-10 mol / L; the initial concentration of the reducing agent is 2-100 times the concentration of the nickel salt; the reaction temperature is 160-210°C; the solvent is selected from oil-soluble reagents with a boiling point higher than 160°C; the reaction atmosphere is selected from carbon monoxide, or a mixture thereof with an inert gas or hydrogen; wherein both the carbon monoxide and the surfactant can be adsorbed on the {111} crystal plane of the nickel nanocrystal to control the exposed crystal plane of the nickel nanocrystal; the inert gas or hydrogen is used to prevent oxidation of the nickel nanocrystal.

[0009] The present invention is in the process of liquid phase synthesis of nickel nanocrystals (see Figure 1 ), the type of seed crystal is controlled by controlling the supersaturated concentration of zero-valent nickel, and the reaction rate is controlled mainly by controlling the reaction atmosphere, reactant concentration and reaction temperature. When the reaction rate is low, the concentration of zero-valent nickel salt generated by the reaction in the solution is low, tending to form a single crystal structure, and then growing into an octahedron or tetrahedron through crystal face control; when the reaction rate is fast, the concentration of zero-valent nickel salt generated by the reaction in the solution is high, tending to form a stacking fault structure, and then growing into a nanosheet through crystal face control; when the reaction rate is further increased, the concentration of zero-valent nickel salt generated by the reaction in the solution is higher, and the seed crystal with multiple dislocations tends to be generated during the nucleation process, and grows into a decahedron through crystal face control.

[0010] Preferably, the surfactant is selected from any one or more of oleylamine, sodium dodecyl sulfate, glucose, carbon monoxide, resorcinol, hydroquinone, and phloroglucinol; or / and, the reducing agent is selected from any one or more of glucose, oleylamine, oleic acid, and hydrogen; or / and, the solvent is selected from any one or more of oleylamine, oleic acid, octadecene, benzyl alcohol, hexanol, heptanol, octanol, nonanol, and decanol; or / and, the inert gas is selected from nitrogen. The surfactant functions to protect the {111} crystal plane of the nickel nanocrystals and disperse them.

[0011] Preferably, the method comprises: adding the surfactant and the reducing agent to a solvent to obtain a solution A; using a mixture of nickel salt, reducing agent and solvent as solution B; adding the solution B to solution A, controlling the reaction atmosphere, reactant concentration and reaction temperature, and controlling the type of seed crystals in the nucleation process, thereby realizing the synthesis of nickel nanocrystals with different morphologies. The order of adding the various substances in the present invention has little effect on the reaction, and the morphology control and synthesis of nickel nanocrystals can be realized. When the various substances are added together for reaction, although some substances may react with each other, such as glucose and oleylamine, the generated substances can also realize the reduction of nickel, and the reaction gas will quickly take away the water vapor during the heating process, which will not affect the zero-valent nickel. In a more optimal way, the surfactant and the reducing agent can be added to the solvent to obtain solution A, and then the nickel salt, the reducing agent and the solvent mixture can be used as solution B, and the two can be mixed.

[0012] More preferably, the surfactant and the reducing agent are added to a solvent, and heated under the protection of an inert gas to remove moisture in the system to obtain the solution A.

[0013] More preferably, the solution B is added to the solution A, and after a reaction time, the solution B is continuously added to increase the nickel salt and the reducing agent, so that the nickel nanocrystals continue to grow, thereby achieving size control of the nickel nanocrystals.

[0014] Preferably, the reaction time is 0.5 to 2 hours. Generally, the nickel salt is completely reduced after 0.5 hours of reaction time, but if nickel salt is added to grow crystals to adjust the size, additional reaction time is required.

[0015] The second objective of the present invention is to provide nickel nanocrystals obtained by the preparation method, wherein the nickel nanocrystals have a cubic phase and their shapes include nano-decahedrons and nano-tetrahedrons.

[0016] Preferably, the size of the nickel nanocrystals is 10 to 400 nm.

[0017] The third object of the present invention is to provide the use of the nickel nanocrystals in hydrogen evolution by electrolysis of water.

[0018] The nickel nanocrystals and the preparation method and application thereof of the present invention solve the problem of the lack of morphology of existing nickel nanocrystals and have the following advantages:

[0019] The synthesis method of the present invention realizes the synthesis of nickel nanocrystal seed crystals with a specific type by controlling the concentration of reactants and the reaction temperature. On this basis, carbon monoxide is used to specifically adsorb on the {111} crystal plane of the nickel nanocrystal, thereby realizing the morphology control of the nickel nanocrystal. By continuing to add nickel salt and reducing agent to the above nickel nanocrystal to make it continue to grow, the size control of the nickel nanocrystal can be realized. In short, the seed crystal control and crystal growth mechanism introduced by the present invention realize the controllable synthesis of nickel nanocrystals with different morphologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a diagram of the nickel nanocrystal morphology control mechanism of the present invention.

[0021] Figure 2 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 1 of the present invention.

[0022] Figure 3 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 2 of the present invention.

[0023] Figure 4 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 3 of the present invention.

[0024] Figure 5 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 4 of the present invention.

[0025] Figure 6 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 5 of the present invention.

[0026] Figure 7 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 6 of the present invention.

[0027] Figure 8 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 7 of the present invention.

[0028] Fig. 9 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 8 of the present invention.

[0029] Fig.10 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 9 of the present invention.

[0030] Fig.11 This is a transmission electron microscope image of nickel nanocrystals prepared in Example 10 of the present invention.

[0031] Fig.12 This is a transmission electron microscope image of nickel nanocrystals prepared in Comparative Example 1 of the present invention.

[0032] Fig.13 This is the result of using the nickel tetrahedron prepared in Example 2 of Application Example 1 of the present invention for hydrogen evolution reaction by electrolysis of water. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that if the specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased from the market.

[0035] In the present invention, all features defined in the form of numerical ranges or percentage ranges, such as values, quantities, contents and concentrations, are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0036] The features mentioned in the present invention can be combined arbitrarily, as long as there is no contradiction in the combination of these features, all possible combinations should be considered as the scope of this specification. Each feature disclosed in the specification can be replaced by any alternative feature that can provide the same, equal or similar purpose. Therefore, unless otherwise specified, the disclosed features are only general examples of equal or similar features.

[0037] Example 1

[0038] A nickel nanocrystal, the preparation method of which comprises:

[0039] Glucose (as a reducing agent), oleylamine (as a solvent, reducing agent and surfactant), resorcinol (as a surfactant), and heptanol (as a solvent) were heated at 160°C for half an hour under nitrogen protection. Glucose reacted with oleylamine to produce a substance that could also be used as a reducing agent. Water was produced in the reaction, and the presence of water made nickel easy to oxidize. Therefore, the water produced by the system reaction was removed to avoid subsequent effects on the generated zero-valent nickel. This solution was recorded as solution A. The initial concentration of oleylamine was 0.8 mol / L, and the initial concentration of glucose was 7×10 -2 mol / L, the initial concentration of resorcinol was 2×10 -2 mol / L.

[0040] The nickel salt was dissolved in oleylamine (as a reducing agent and surfactant), which was recorded as solution B. The concentration of the nickel salt was 4×10 -2 mol / L.

[0041] A certain amount of solution B was added to solution A, and then carbon monoxide gas (as a surfactant) was introduced at a rate of 100 mL / min until saturation. After mixing evenly, the mixture was heated to 175°C, stirred vigorously, and reacted for 0.5 hours.

[0042] like Figure 2 The transmission electron microscope image of the nickel nanocrystals prepared in Example 1 of the present invention is shown in FIG. Figure 2 It can be seen that the prepared nickel nanocrystals are mainly nano-decahedrons, the average side length of the prepared decahedrons is about 20nm, the transmission projection diagram is a regular pentagon, and the yield is about 71%.

[0043] Example 2

[0044] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 1, except that:

[0045] The initial concentration of oleylamine was 0.2 mol / L, and the initial concentration of glucose was 4×10 -2 mol / L, the initial concentration of resorcinol was 4×10 -2 mol / L; the reaction temperature is 170℃.

[0046] like Figure 3 The transmission electron microscope image of the nickel nanocrystals prepared in Example 2 of the present invention is shown in FIG. Figure 3 It can be seen that the obtained nickel nanocrystals are mainly nano-tetrahedrons, the average side length of the obtained tetrahedrons is about 10nm, the transmission projection diagram is triangular, and the yield is about 92%.

[0047] Example 3

[0048] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 2, except that:

[0049] After 0.5 hours of reaction, a certain amount of solution B was added to the solution to make the total concentration of the added nickel salt 8×10 -2 mol / L.

[0050] like Figure 4 The transmission electron microscope image of the nickel nanocrystals prepared in Example 3 of the present invention is shown in FIG. Figure 4 It can be seen that the obtained nickel nanocrystals are mainly nano-tetrahedrons, the average side length of the obtained tetrahedrons is about 18nm, the transmission projection diagram is triangular, and the yield is about 84%.

[0051] Example 4

[0052] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 1, except that:

[0053] The initial concentration of glucose was 2×10 -2 mol / L, the initial concentration of resorcinol was 1×10 -2 mol / L; the reaction temperature is 165℃.

[0054] like Figure 5 The transmission electron microscope image of the nickel nanocrystals prepared in Example 4 of the present invention is shown in FIG. Figure 5 It can be seen that the obtained nickel nanocrystals are mainly nano-octahedra, the average side length of the obtained octahedra is about 20nm, the transmission projection diagram is rhombus, and the yield is about 83%.

[0055] Example 5

[0056] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 4, except that:

[0057] The reaction temperature was 170°C.

[0058] like Figure 6 As shown, it is an atomic force microscope image of nickel nanocrystals prepared in Example 5 of the present invention. Figure 6 It can be seen that the prepared nickel nanocrystals are mainly nanosheets, the average side length of the prepared nanosheets is about 20nm, the transmission projection image is triangular, and the yield is about 93%.

[0059] Example 6

[0060] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 5, except that:

[0061] After half an hour of reaction at 170°C, a certain amount of solution B was added to the solution to make the total concentration of the added nickel salt 8×10 -2 mol / L.

[0062] like Figure 7 As shown, it is an atomic force microscope image of nickel nanocrystals prepared in Example 6 of the present invention. Figure 7 It can be seen that the prepared nickel nanocrystals are nanosheets, the average side length of the prepared nanosheets is about 100nm, and the transmission projection image is triangular.

[0063] Example 7

[0064] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 1, except that:

[0065] Solution A contains: oleic acid (as solvent, surfactant and reducing agent), oleylamine (as surfactant and reducing agent), octadecene (as solvent), wherein the initial concentration of oleylamine is 0.2 mol / L, the initial concentration of oleic acid is 0.2 mol / L; the concentration of nickel salt is 4×10 -2 mol / L; solution B was added to solution A, and then carbon monoxide (as a surfactant) gas was introduced; the reaction temperature was 210°C.

[0066] like Figure 8 The transmission electron microscope image of the nickel nanocrystals prepared in Example 7 of the present invention is shown in FIG. Figure 8 It can be seen that the prepared nickel nanocrystals are a mixture of nanosheets and decahedrons, with an average side length of about 10 nm.

[0067] Example 8

[0068] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 7, except that:

[0069] A mixed gas of carbon monoxide (5%), nitrogen (90%) and hydrogen (5%) was introduced at a rate of 100 mL / min until saturation; the reaction temperature was 170°C.

[0070] like Fig. 9 The transmission electron microscope image of the nickel nanocrystals prepared in Example 8 of the present invention is shown in FIG. Fig. 9 It can be seen that the shape of the prepared nickel nanocrystals is mainly leaf-like, with an average long side length of about 400nm, an average short side length of 160nm, and a yield of about 58%.

[0071] Example 9

[0072] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 1, except that:

[0073] The concentration of nickel salt is 1×10 -4 mol / L, the initial concentration of oleylamine was 2×10 -4 mol / L; the reaction temperature is 170℃.

[0074] like Fig.10 As shown, it is a transmission electron microscope image of nickel nanocrystals obtained in Example 10 of the present invention. Fig. 9 It can be seen that the prepared nickel nanocrystals are a mixture of nanosheets and small seed crystals, which is mainly due to the low concentration of nickel salt in the system and the limited seed crystal growth process.

[0075] Example 10

[0076] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 5, except that:

[0077] The initial concentration of oleylamine was 4 mol / L.

[0078] like Fig.11 As shown, it is a transmission electron microscope image of nickel nanocrystals obtained in Example 10 of the present invention. Fig.11 It can be seen that the prepared nickel nanocrystals are nanosheets with an average size of 10 nm and a yield of 88%.

[0079] When the reducing agent concentration increases, the number of seed crystals generated increases, and the size of the nanocrystals obtained at the same nickel salt concentration decreases to a certain extent.

[0080] Comparative Example 1

[0081] A nickel nanocrystal, the preparation method of which is substantially the same as that of Example 2, except that:

[0082] No carbon monoxide gas is introduced.

[0083] like Fig.12 As shown, it is a transmission electron microscope picture of nickel nanocrystals prepared in Comparative Example 1 of the present invention. Fig.12 It can be seen that the prepared nickel nanocrystals are mainly spherical, with an average side length of about 15nm.

[0084] Application Example 1

[0085] The nickel tetrahedron prepared in Example 2 of the present invention or the nickel nanosphere synthesized in Comparative Example 1 is used for the hydrogen evolution reaction by electrolysis of water, and the specific process is as follows:

[0086] The nickel tetrahedron or nickel nanosphere was washed three times with n-butylamine and ethanol respectively, and then loaded on carbon (Ketjen black) to make the nickel content 20wt%. 10μg of the above material was evenly coated on a glassy carbon electrode (diameter 5mm), and then 5μL of 0.5% naphthol solution was added and dried. The test was carried out on an electrochemical workstation using a three-electrode system and a rotating disk electrode. A calomel electrode was used as a reference electrode and a carbon rod was used as a counter electrode. In nitrogen-saturated potassium hydroxide (1mol / L), the reaction was carried out at 10mV s at 25°C. -1 The scanning rate was 1600 revolutions per minute, and the line scanning was performed from 0 V to -0.15 V.

[0087] like Fig.13 As shown in the figure, it can be seen that the electrolytic water hydrogen evolution activity of the obtained nickel tetrahedron is higher than that of the nickel nanospheres synthesized in Comparative Example 1.

[0088] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A method for preparing nickel nanocrystals, characterized in that: The method includes: The nickel salt, surfactant and reducing agent are added to a solvent and placed in a reaction atmosphere, and the reaction atmosphere, reactant concentration and reaction temperature are controlled, thereby controlling the reaction rate to regulate the supersaturated concentration of zero-valent nickel in the solution, so as to control the formation of single crystals, stacking faults or seed crystals with multiple dislocation structures of zero-valent nickel, thereby controlling the type of seed crystals in the nucleation process and obtaining nickel nanocrystals with different morphologies; Wherein, the concentration of the nickel salt is 1×10 -4 mol / L~8×10 -2 mol / L; the initial concentration of the surfactant is 0.1 to 10 mol / L; the initial concentration of the reducing agent is 2 to 100 times the concentration of the nickel salt; The reaction temperature is 160-210°C; The solvent is selected from oil-soluble reagents having a boiling point higher than 160°C; The reaction atmosphere is selected from carbon monoxide, or a mixture thereof with an inert gas or hydrogen; wherein the carbon monoxide and the surfactant can be adsorbed on the {111} crystal plane of the nickel nanocrystal to control the exposed crystal plane of the nickel nanocrystal; and the inert gas or hydrogen is used to prevent the nickel nanocrystal from being oxidized.

2. The preparation method according to claim 1, characterized in that: The surfactant is selected from any one or more of oleylamine, sodium lauryl sulfate, glucose, carbon monoxide, resorcinol, hydroquinone, and phloroglucinol; Or / and, the reducing agent is selected from any one or more of glucose, oleylamine, oleic acid, and hydrogen; or / and, the solvent is selected from any one or more of oleylamine, oleic acid, octadecene, benzyl alcohol, hexanol, heptanol, octanol, nonanol, and decanol; Or / and, the inert gas is selected from nitrogen.

3. The preparation method according to claim 1, characterized in that: The method includes: Adding the surfactant and the reducing agent into a solvent to obtain a solution A; A mixture of nickel salt, reducing agent and solvent is used as solution B; The solution B is added to the solution A, and the reaction atmosphere, reactant concentration and reaction temperature are controlled to achieve control of the seed crystal type during the nucleation process, thereby achieving synthesis of nickel nanocrystals with different morphologies.

4. The preparation method according to claim 3, characterized in that: The surfactant and the reducing agent are added to the solvent, and heated under the protection of an inert gas to remove moisture in the system, thereby obtaining the solution A.

5. The preparation method according to claim 3, characterized in that: The solution B is added to the solution A, and after reacting for a period of time, the solution B is continuously added to increase the nickel salt and the reducing agent, so that the nickel nanocrystals continue to grow, thereby achieving size control of the nickel nanocrystals.

6. The preparation method according to claim 1, characterized in that: The reaction time is 0.5 to 2 hours.

7. The nickel nanocrystal obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The nickel nanocrystal phase is a cubic phase, and its shape includes: nano decahedron and nano tetrahedron.

8. The nickel nanocrystal according to claim 7, characterized in that: The size of the nickel nanocrystal is 10-400nm.

9. Use of nickel nanocrystals obtained by the preparation method as claimed in claim 7 or 8 in hydrogen evolution by electrolysis of water.

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