CN109455775B

CN109455775B - Preparation method of nano nickel oxide

Info

Publication number: CN109455775B
Application number: CN201811425121.5A
Authority: CN
Inventors: 杨英; 陈甜; 郭学益; 林飞宇; 朱从谭
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2018-11-27
Filing date: 2018-11-27
Publication date: 2021-03-26
Anticipated expiration: 2038-11-27
Also published as: CN109455775A

Abstract

A preparation method of nano nickel oxide comprises the following steps: (1) mixing oleic acid and octadecylene solvent, stirring and heating, adding nickel acetylacetonate, heating and stirring to obtain a light green mixed solution; (2) mixing oleylamine and a surfactant, adding the mixture into a light green mixed solution, and heating and stirring the mixture to obtain a precursor of a product; (3) keeping the temperature of a precursor of the product at 200-220 ℃ for 6-10 h, taking out, and naturally cooling to room temperature to obtain a gray-green nickel oxide solution; (4) and pouring a centrifugal solution into the grey-green nickel oxide solution, centrifuging, removing supernatant, leaving a bottom precipitate, adding a cleaning solution into the precipitate to disperse the precipitate, and repeatedly cleaning to obtain the nano-scale nickel oxide. The method has the advantages of low price of raw materials, simple experimental operation, no harsh reaction environment, no generation of toxic gas, simple purification and capability of quickly obtaining the nano nickel oxide.

Description

Preparation method of nano nickel oxide

Technical Field

The invention belongs to the field of chemical science, and particularly relates to a preparation method of nano nickel oxide.

Background

When the size of the particles is small to the nanometer level, many inherent characteristics of the substance per se are changed substantially, and the remarkable physical and chemical properties, namely the optical, thermal, electrical, magnetic, mechanical and chemical properties are different from those of the bulk solid, so-called abnormal phenomena occur, and the phenomena are called nanometer effect; the method mainly comprises the surface effect, the small-size effect, the quantum size effect, the macroscopic quantum tunneling effect, the coulomb blockade effect and the like. Due to the special properties of the nano particles, the nano material has wide application prospects in the aspects of sintering, catalysis, sensing and the like of magnetic materials, electronic materials, optical materials, high-strength and high-density materials.

NiO is an oxidation catalyst with better catalytic performance. Ni²⁺Has 3d orbit, has preferential adsorption tendency to multi-electron oxygen, has activation effect on other reducing gases and has catalytic effect on the oxidation of the reducing gases. The nanometer NiO has attracted attention in the field of catalysis due to the large surface area, short intracrystalline diffusion channels, rich active sites, high surface atomic ratio and surface energy, and activity and selectivity far higher than those of the traditional catalyst. Especially in recent years, with the increasing increase of the problem of energy scarcity, renewable energy such as biomass and the like is developed and utilized through a thermal decomposition technology, fossil raw materials are replaced to a certain extent, NiO is used as a catalyst with excellent cost performance, and the yield and efficiency of biomass gasification and pyrolysis can be greatly improved.

The preparation method of nickel oxide is mainly divided into a solid phase method, a liquid phase method and a gas phase method. The solid phase method has the advantages of low cost, high yield, easily controlled reaction conditions and the like, but has the defects of high energy consumption, low efficiency, large product particle size, easy oxidation deformation and agglomeration of particles and the like. The liquid phase method for preparing the nano nickel oxide has the characteristics of easy preparation of nucleation and growth processes, high cost, uneven particle size and the like. The gas phase method has the characteristics of high yield, high capacity, difficult shape control and the like. For example, CN 107855125 a discloses a method for preparing nano-grade nickel oxide, which requires a muffle furnace to bake at high temperature for a long time, and has high energy consumption, and the obtained nickel oxide has non-uniform particle size, which is not suitable for wide application.

In conclusion, the application development of the nano nickel oxide is limited due to large capacity, complex preparation process, non-uniform morphology, severe reaction conditions and the like. Therefore, it is necessary to develop a nano-grade nickel oxide with easy synthesis, low cost and uniform particle size.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects of the prior art and providing the preparation method of the nano nickel oxide with simple process, high speed and low cost, and the obtained nano nickel oxide has uniform appearance and controllable particle size.

The technical scheme adopted by the invention for solving the technical problem is that,

a preparation method of nano nickel oxide comprises the following steps:

(1) mixing oleic acid and an octadecylene solvent, stirring and heating to 30-50 ℃, adding nickel acetylacetonate, heating to 100-120 ℃, and stirring for 1-1.5 hours to form a uniform solution to obtain a light green mixed solution;

(2) mixing oleylamine and a surfactant, adding the mixture into the light green mixed solution obtained in the step (1), heating at a constant temperature of 100-120 ℃, and stirring for 1-1.5 hours to form a brownish red solution, so as to obtain a precursor of a product;

(3) transferring the precursor of the product obtained in the step (2) into a high-temperature reaction kettle, preserving heat for 6-10 hours in an electric heating constant-temperature air blast drying oven at 200-220 ℃, and then taking out and naturally cooling to room temperature to obtain a gray-green nickel oxide solution;

(4) and (3) pouring a centrifugal solution into the gray green nickel oxide solution obtained in the step (3), centrifuging at the rotation speed of 10000-15000 rpm for 10-20 min, removing the supernatant, leaving a bottom precipitate, adding a cleaning solution into the precipitate to disperse the precipitate, and repeatedly cleaning for more than 2 times to obtain particles, namely the nano-nickel oxide.

Further, in the step (1) and the step (2), the weight percentages of the raw materials are as follows: 45-55% of Octadecene (ODE), 13-20% of Oleic Acid (OA), 19-31% of oleylamine (OAm), 1-5% of surfactant, and the sum of the mass percentages of the raw materials is 100%.

Further, in the step (1), the molar ratio of the nickel acetylacetonate to the oleic acid is 1: 1-3.

Further, in the step (2), the surfactant is at least one of polyvinylpyrrolidone, tween-80 or sodium dodecyl sulfate.

Further, in the step (4), the centrifugal solution and the cleaning solution are mixed solution of n-hexane and absolute ethyl alcohol in a volume ratio of 1: 2-5. The addition of the centrifugation solution and the washing solution is for washing the precipitate, so the amount of the washing solution is enough to cover the precipitate, and can be more or less.

The invention selects polyvinylpyrrolidone, tween-80 or sodium dodecyl sulfate as a dispersing agent, nickel acetylacetonate as a nickel source, and the polyvinylpyrrolidone can effectively reduce the crosslinking of NiO nano particles to obtain NiO with uniform dispersion, and is beneficial to rapid nucleation of NiO and shortening of preparation time. In addition, researches show that the particle size of NiO can be effectively controlled by controlling the heat preservation time in the step (3), reaction conditions are changed, nano NiO with different particle sizes is obtained, and the corresponding band gaps are also changed.

As the proportion of oleic acid in the reactants increases, the morphology of the product changes from spheroidal to spheroidal, and the average particle size increases. The introduction of excessive oleic acid can increase the driving force of crystal nucleus growth in the reaction, so that the particle size is increased and homogenized, and the crystal form is more complete; at the same time, the excessive oleic acid can affect the supersaturation concentration of nickel atoms, inhibit the nucleation process of the nickel atoms and reduce the yield of the product.

And (4) as the heat preservation time in the step (3) is prolonged (6-10 h), the product always keeps the spheroidal morphology, and the average particle size is increased from 18.55nm to 57.43 nm. The long holding time at 200 ℃ provides enough growth driving force for crystal nucleus to increase the grain diameter. After reaching the supersaturated concentration, the nickel ions first generate nickel atoms, and then are further oxidized, but the product is still a mixed substance of NiO and Ni. In order to generate pure phases of oxides, the appearance and the particle size of a sample are regulated and controlled simultaneously, and an additive polyvinylpyrrolidone (PVP) is introduced, so that not only is an oxygen element introduced into a reaction system, but also a certain dispersion effect can be achieved.

Compared with the prior art, the invention has the advantages that:

(1) the raw materials used in the invention have low price, the experimental operation is simple, the harsh reaction environment is not needed, no toxic gas is generated, the purification is simple, and the nano nickel oxide can be quickly obtained;

(2) the polyvinylpyrrolidone, the Tween-80 or the sodium dodecyl sulfate are used as the surfactant, and the highly dispersed composite precursor is obtained through the action of the surfactant and organic matters and metal ions. And finally, removing redundant organic matters in a constant-temperature heating mode to obtain the nano nickel oxide with uniform particle size and stable performance.

(3) The nano nickel oxide prepared by the method does not contain toxic metal elements, has controllable particle size and adjustable band gap, has excellent physicochemical properties, and can be applied to renewable energy sources, photoelectric devices and other aspects.

The optical band gap of the nickel oxide serving as the p-type semiconductor is greatly influenced by the size, shape and appearance of the material, the nickel oxide with spherical microscopic appearance and uniform particle size is synthesized according to the method, the actual band gap is 3.6-3.75eV which is obtained through ultraviolet and visible light absorption spectrum test and is close to the theoretical band gap, and the synthesized sample is pure-phase nickel oxide which can well absorb ultraviolet light or visible light, so that the nickel oxide can be applied to the optical field.

Drawings

FIG. 1 is a transmission electron micrograph of nickel oxide obtained in comparative example 1;

FIG. 2 is a transmission electron micrograph of nickel oxide obtained in example 1;

FIG. 3 is a graph showing a particle size distribution of nickel oxide obtained in comparative example 2;

FIG. 4 is a graph showing a particle size distribution of nickel oxide obtained in example 2;

FIG. 5 is a graph showing a particle size distribution of nickel oxide obtained in example 4;

FIG. 6 is a particle size distribution diagram of nickel oxide obtained in example 7.

Detailed Description

In order to facilitate understanding of the present invention, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following specific examples.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Comparative example 1:

the preparation method of the nano nickel oxide of the comparative example comprises the following steps:

(1) respectively weighing 47.34 g of octadecene (62.5 mmol) and 16.95 g of oleic acid (20 mmol) at room temperature, mixing, stirring, heating to 30 ℃, adding 20mmol of nickel acetylacetonate, heating to 100 ℃, and stirring for 1.5 h to form a uniform solution to obtain a light green mixed solution;

(2) adding 24.07 g of oleylamine into the light green mixed solution obtained in the step (1), heating at a constant temperature of 100 ℃, and stirring for 1 h to form a brownish red solution, so as to obtain a precursor of a product;

(3) transferring the precursor of the product obtained in the step (2) into a high-temperature reaction kettle, preserving heat for 6 hours in an electric heating constant-temperature air-blast drying oven at 200 ℃, and then taking out and naturally cooling to room temperature to obtain a gray-green nickel oxide solution;

(4) and (4) pouring a centrifugal solution into the gray green nickel oxide solution obtained in the step (3), centrifuging for 10 min at the rotating speed of 12000 rpm, removing the supernatant, leaving a bottom precipitate, adding a cleaning solution into the precipitate to disperse the precipitate, and repeatedly cleaning for 2 times to obtain particles, namely the nano nickel oxide.

In the step (4), the centrifugal solution and the cleaning solution are mixed solution of n-hexane and absolute ethyl alcohol in a volume ratio of 1: 2.

In this comparative example, nickel oxide having an average particle diameter of 88.24nm was obtained.

FIG. 1 is a transmission electron micrograph of nickel oxide obtained in comparative example 1; it can be seen from the figure that the nickel oxide obtained in comparative example 1 is strongly agglomerated.

Comparative example 2

Comparative example 2 is different from comparative example 1 in that 40 mmol of nickel acetylacetonate was added in step (1) and other operating conditions were the same as in comparative example 1, to obtain nickel oxide having an average particle diameter of 111.59 nm.

FIG. 3 is a graph showing the distribution of the particle size of the nickel oxide obtained in comparative example 2, and it can be seen that the distribution of the particle size of the nickel oxide obtained in comparative example 2 is not uniform.

Comparative example 3

Comparative example 3 is different from comparative example 1 in that 60 mmol of nickel acetylacetonate was added in step (1) and other operating conditions were the same as in comparative example 1 to obtain nickel oxide having an average particle diameter of 143.79 nm.

The nickel oxide obtained by the comparative example has large particle size and agglomeration phenomenon.

Example 1:

the preparation method of the nano nickel oxide of the embodiment includes the following steps:

(1) respectively weighing 47.34 g of octadecene (62.5 mmol) and 16.98 g of oleic acid (20 mmol) at room temperature, mixing, stirring and heating to 50 ℃, adding 6.94 g of nickel acetylacetonate, heating to 120 ℃, and stirring for 1 h to form a uniform solution to obtain a light green mixed solution;

(2) mixing 1.6 g of tween-80 and 24.07 g of oleylamine, adding the mixture into the light green mixed solution obtained in the step (1), heating at the constant temperature of 120 ℃, and stirring for 80 min to form a brownish red solution, so as to obtain a precursor of a product;

(4) and (3) pouring a centrifugal solution into the gray green nickel oxide solution obtained in the step (3), centrifuging for 20 min at the rotating speed of 12000 rpm, removing the supernatant, leaving a bottom precipitate, adding a cleaning solution into the precipitate to disperse the precipitate, and repeatedly cleaning for 2 times to obtain particles, namely the nano-nickel oxide. In the step (4), the centrifugal solution and the cleaning solution are mixed solution of n-hexane and absolute ethyl alcohol in a volume ratio of 1: 5. Nickel oxide with an average particle size of 18.55nm was obtained.

FIG. 2 is a transmission electron micrograph of nickel oxide obtained in example 1; as can be seen from the figure, the nickel oxide obtained in example 1 did not agglomerate.

FIG. 4 is a graph showing the particle size distribution of the nickel oxide obtained in example 2, and it can be seen that the particle size distribution of the nickel oxide obtained in example 2 is uniform.

Example 2

Example 2 differs from example 1 in that in step (3), nickel oxide having an average particle size of 54.73nm was produced by maintaining the temperature in an electrically heated constant temperature forced air drying oven at 200 ℃ for 8 hours under the same operating conditions as in example 1.

Example 3

Example 3 differs from example 1 in that in step (3), nickel oxide having an average particle size of 57.43nm was produced by maintaining the temperature in an electrically heated constant temperature forced air drying oven at 200 ℃ for 10 hours under the same operating conditions as in example 1.

Example 4:

(1) respectively weighing 47.34 g of octadecene (62.5 mmol) and 16.95 g of oleic acid (20 mmol) at room temperature, mixing, stirring, heating to 50 ℃, adding 6.96 g of nickel acetylacetonate, heating to 110 ℃, and stirring for 1.5 h to form a uniform solution to obtain a light green mixed solution;

(2) mixing 1.6 g of sodium dodecyl sulfate and 24.07 g of oleylamine, adding the mixture into the light green mixed solution obtained in the step (1), heating at the constant temperature of 110 ℃, and stirring for 1 hour to form a brownish red solution, so as to obtain a precursor of a product;

(4) and (3) pouring a centrifugal solution into the gray green nickel oxide solution obtained in the step (3), centrifuging for 20 min at the rotating speed of 15000 rpm, removing the supernatant, leaving a bottom precipitate, adding a cleaning solution into the precipitate to disperse the precipitate, and repeatedly cleaning for more than 2 times to obtain particles, namely the nano-nickel oxide. Nickel oxide with an average particle size of 45.30nm was obtained.

In the step (4), the centrifugal solution and the cleaning solution are mixed solution of n-hexane and absolute ethyl alcohol in a volume ratio of 1: 3.

FIG. 5 is a distribution diagram of the particle size of the nickel oxide obtained in example 4, and it can be seen that the particle size distribution of the nickel oxide obtained in example 4 is uniform.

Example 5

Example 5 differs from example 4 in that in step (3) nickel oxide with an average particle size of 41.25nm was produced by maintaining the temperature in an electrically heated constant temperature forced air drying oven at 200 ℃ for 8h, but otherwise the operating conditions were the same as in example 4.

Example 6

Example 6 differs from example 4 in that in step (3) nickel oxide with an average particle size of 40.06nm was produced by maintaining the temperature in an electrically heated constant temperature forced air drying oven at 200 ℃ for 10 hours under otherwise the same operating conditions as in example 4.

Example 7:

(2) mixing 1.6 g of polyvinylpyrrolidone and 24.07 g of oleylamine, adding the mixture into the light green mixed solution obtained in the step (1), heating at the constant temperature of 110 ℃, and stirring for 1 hour to form a brownish red solution, so as to obtain a precursor of a product;

(4) and (3) pouring a centrifugal solution into the gray green nickel oxide solution obtained in the step (3), centrifuging for 20 min at the rotating speed of 15000 rpm, removing the supernatant, leaving a bottom precipitate, adding a cleaning solution into the precipitate to disperse the precipitate, and repeatedly cleaning for more than 2 times to obtain particles, namely the nano-nickel oxide. The nickel oxide with the average grain diameter of 41.02nm is prepared.

In the step (4), the centrifugal solution and the cleaning solution are mixed solution of n-hexane and absolute ethyl alcohol in a volume ratio of 1: 4.

FIG. 6 is a graph showing the particle size distribution of the nickel oxide obtained in example 7, and it can be seen that the particle size distribution of the nickel oxide obtained in example 7 is uniform.

Example 8

Example 8 differs from example 7 in that in step (3) nickel oxide having an average particle size of 45.30nm was produced by maintaining the temperature in an electrically heated constant temperature forced air drying oven at 200 ℃ for 8 hours under the same operating conditions as in example 7.

Example 9

Example 9 differs from example 7 in that in step (3) nickel oxide having an average particle size of 77.80 nm was produced by maintaining the temperature in an electrically heated constant temperature forced air drying oven at 200 ℃ for 10 hours under the same operating conditions as in example 7.

In conclusion, the preparation method of the nano nickel oxide is simple, the raw material source is wide, the cost is low, the surfactant is adopted, the highly dispersed composite precursor is obtained through the action of the surfactant and organic matters and metal ions, and in addition, the surfactant film can effectively prevent the particles from forming aggregates, so that the prepared particle size can be stably stored for a long time. And finally, removing redundant organic matters in a constant-temperature heating mode to obtain the nano nickel oxide with uniform particle size and stable performance. The nano nickel oxide prepared by the method has the advantages of uniformity, controllability, higher quality, adjustable band gap and excellent physical and chemical properties, and can be applied to renewable energy sources, photoelectric devices and other aspects.

Claims

1. A preparation method of nano nickel oxide is characterized by comprising the following steps:

(2) mixing oleylamine and a surfactant, adding the mixture into the light green mixed solution obtained in the step (1), heating at a constant temperature of 100-120 ℃, and stirring for 1-1.5 hours to form a brownish red solution, so as to obtain a precursor of a product; the surfactant is tween-80;

2. The method for preparing nano nickel oxide according to claim 1, wherein in the step (1) and the step (2), the weight percentage of each raw material is as follows: 45-55% of octadecene, 13-20% of oleic acid, 19-31% of oleylamine and 1-5% of surfactant, wherein the sum of the mass percentages of the raw materials is 100%.

3. The method for preparing nano nickel oxide according to claim 1 or 2, wherein in the step (1), the molar ratio of nickel acetylacetonate to oleic acid is 1: 1-3.

4. The method for preparing nano nickel oxide according to claim 1 or 2, wherein in the step (4), the centrifugal solution and the cleaning solution are mixed solution of n-hexane and absolute ethyl alcohol in a volume ratio of 1: 2-5.