阅读说明：本技术 一种氮、硫元素掺杂的氧化镧/苋菜基碳纳米复合材料及其制备方法和应用 (Nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite and preparation method and application thereof ) 是由 杨洲 向萌 陈建香 朱云峰 杨润苗 刘江 于 2020-05-21 设计创作，主要内容包括：本发明涉及一种氮、硫元素掺杂的氧化镧/苋菜基碳纳米复合材料及其制备方法和应用,制备方法包括如下步骤：将苋菜洗净、烘干,进行预碳化,得到苋菜基碳粉,将其分散在镧盐水溶液中,超声处理,然后进行水热反应,得到氧化镧/苋菜基碳纳米复合材料,然后与硫氰化钾混合均匀进行煅烧,最后得到氮、硫元素掺杂的氧化镧/苋菜基碳纳米复合材料。本发明方法制得的氮、硫元素掺杂的氧化镧/苋菜基碳纳米复合材料具有较高的比表面积和孔隙率以及具有较好的电化学性能,作为电极材料应用于电解水制氢能够获得较低的析氢电位,应用于超级电容器能够获得较高的比电容和较高的容量保持率。(The invention relates to a nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material and a preparation method and application thereof, wherein the preparation method comprises the following steps: cleaning amaranth, drying, pre-carbonizing to obtain amaranth-based carbon powder, dispersing the amaranth-based carbon powder in a lanthanum salt aqueous solution, carrying out ultrasonic treatment, then carrying out hydrothermal reaction to obtain a lanthanum oxide/amaranth-based carbon nano composite material, then uniformly mixing with potassium thiocyanate, and calcining to obtain the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material. The nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material prepared by the method has higher specific surface area and porosity and better electrochemical performance, can obtain lower hydrogen evolution potential when being used as an electrode material for hydrogen production by water electrolysis, and can obtain higher specific capacitance and higher capacity retention rate when being used in a super capacitor.)

1. A preparation method of a nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material is characterized by comprising the following steps:

(1) cleaning amaranth, drying, and pre-carbonizing to obtain amaranth-based carbon powder;

(2) dispersing the amaranth-based carbon powder in a lanthanum salt aqueous solution, carrying out ultrasonic treatment, then placing the mixture in a hydrothermal reaction kettle for hydrothermal reaction, washing with water, and drying to obtain a lanthanum oxide/amaranth-based carbon nano composite material;

(3) and uniformly mixing the lanthanum oxide/amaranth-based carbon nano composite material with potassium thiocyanate, calcining, cooling, washing and drying to obtain the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material.

2. The method for preparing the nitrogen and sulfur element doped lanthanum oxide/amaranth based carbon nanocomposite material according to the claim 1, wherein the pre-carbonization in the step (1) is performed for 1-2 h at 300-400 ℃ in a tubular furnace under nitrogen atmosphere; the temperature of the hydrothermal reaction in the step (2) is 100-120 ℃, and the reaction time is 10-12 h; the calcining process in the step (3) is to calcine for 1.5 to 2 hours at the temperature of 600 to 800 ℃ in a tubular furnace under the nitrogen atmosphere.

3. The method for preparing nitrogen and sulfur doped lanthanum oxide/amaranth based carbon nanocomposite material according to claim 1, wherein the lanthanum salt aqueous solution in the step (2) is lanthanum nitrate aqueous solution; the molar concentration of the lanthanum salt aqueous solution is 0.05 mol/L-0.1 mol/L; the mass volume ratio of the amaranth-based carbon powder to the lanthanum salt aqueous solution is 1g:25 mL.

4. The preparation method of the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite material according to claim 1, wherein the temperature of the ultrasonic treatment in the step (2) is not more than 30 ℃, the ultrasonic power is 800-1000W, and the ultrasonic time is 0.5-1 h.

5. The method for preparing the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite material according to claim 1, wherein the mass ratio of the lanthanum oxide/amaranth-based carbon nanocomposite material to the potassium thiocyanate in the step (3) is 1 (3-5).

6. A nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite prepared by the preparation method of any one of claims 1 to 5.

7. The application of the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite prepared by the preparation method of any one of claims 1-5 in hydrogen production by water electrolysis is characterized in that the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite is used as an electrocatalytic material on an electrode material in hydrogen production by water electrolysis.

8. The application according to claim 7, wherein the method of application is: uniformly dispersing the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material into a mixed solution of Nafion resin, water and ethanol to prepare the electro-catalysis material, coating the electro-catalysis material on nickel foam, and drying to obtain the electrode material, wherein the electrode material comprises a cathode and an anode;

the mass ratio of the Nafion resin to the water to the ethanol is 1:2: 7; the loading capacity of the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite on the nickel foam is 0.4 mg/cm.

9. The application of the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite prepared by the preparation method of any one of claims 1-5 in a supercapacitor is characterized in that the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite is used as an electrode of the supercapacitor.

10. The application according to claim 9, wherein the method of application is: uniformly dispersing the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material in a mixed solution of Nafion resin, water and ethanol, then coating the mixed solution on nickel foam, drying to obtain the electrode, and immersing the middle of two identical electrodes in a PVA-KOH gel electrolyte at intervals by a diaphragm to assemble a symmetrical supercapacitor;

the mass ratio of the Nafion resin to the water to the ethanol is 1:2: 7; the loading capacity of the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite on the nickel foam is 0.4 mg/cm.

Technical Field

The invention relates to the technical field of carbon nano composite materials, in particular to a nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material and a preparation method and application thereof.

Background

With the development of economic society, the energy demand is more and more. The fossil fuels such as coal, natural gas, petroleum and the like belong to the traditional energy sources which can not be said any more, so that the development of new energy sources which are stable in supply and efficient in use is urgent, and the research has important social significance.

The hydrogen belongs to secondary new energy, has the advantages of high combustion heat value, cleanness, no pollution, wide application range and the like, occupies an important position in the industrial fields of aerospace, electronic appliances and the like and human life, and has irreplaceable effect on the aspect of fuel power. At present, the methods for producing hydrogen mainly include a coal gasification method, a steam reforming method, an electrolytic water method and the like. Among them, the water electrolysis method is the most easily applied hydrogen production method in large scale, and the used equipment is simple, the preparation process is pollution-free, and the prepared hydrogen has high purity. However, the key to realize large-scale hydrogen production by water electrolysis is to reduce the energy consumption of electrolysis, while the electrode materials in the prior art show higher hydrogen evolution potential, so that the electrode materials with lower hydrogen evolution potential need to be developed.

In addition, batteries or supercapacitors play an important role in energy storage in view of stability, the continuous large-scale use of renewable energy sources. The super capacitor has the advantages of high power density, long service life, fast charge and discharge performance, no pollution and the like. The key to influence the performance and quality of the super capacitor is the electrode material, and the development of the electrode material with excellent performance is of great significance. The ideal electrode material of the super capacitor has to satisfy the following characteristics: high specific surface area, suitable porosity, good electrical conductivity, ideal electrochemically active sites, excellent chemical and thermal stability. The existing electrode materials used as the super capacitor mainly comprise the following types: carbon materials such as activated carbon, carbon nanotubes, template carbon, etc., metal oxide materials such as cobalt oxide, ruthenium oxide, etc., conductive polymer materials such as PANI, PPy, PTh, etc., composite materials. The above electrode materials all have advantages and disadvantages, such as low porosity of carbon material, low specific capacitance caused by poor pseudo-electric characteristics, low capacity retention rate caused by low specific surface area of metal oxide, etc., and how to make up for the deficiencies of the metal oxide to prepare the composite material with high specific capacitance and capacity retention rate is a difficult problem.

Disclosure of Invention

In order to solve the technical problems of high hydrogen evolution potential in the water electrolysis hydrogen production technology caused by small specific surface area and small porosity of an electrode material and low specific capacitance and capacity retention rate of a super capacitor, the nitrogen and sulfur element doped lanthanum oxide/amaranth based carbon nano composite material and the preparation method and the application thereof are provided. The lanthanum oxide/amaranth-based carbon nano composite material has higher specific surface area and porosity and better electrochemical performance, can obtain lower hydrogen evolution potential when being used as an electrode material for hydrogen production by water electrolysis, and can obtain higher specific capacitance and higher capacity retention rate when being used in a super capacitor.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a preparation method of nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite comprises the following steps:

(1) cleaning amaranth, drying, and pre-carbonizing to obtain amaranth-based carbon powder;

(2) dispersing the amaranth-based carbon powder in a lanthanum salt aqueous solution, carrying out ultrasonic treatment, then placing the mixture in a hydrothermal reaction kettle for hydrothermal reaction, washing with water, and drying to obtain a lanthanum oxide/amaranth-based carbon nano composite material;

(3) and uniformly mixing the lanthanum oxide/amaranth-based carbon nano composite material with potassium thiocyanate, calcining, cooling, washing and drying to obtain the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material.

Further, the pre-carbonization process in the step (1) is to perform pre-carbonization for 1 to 2 hours at the temperature of 300 to 400 ℃ in a nitrogen atmosphere in a tubular furnace; the temperature of the hydrothermal reaction in the step (2) is 100-120 ℃, and the reaction time is 10-12 h; the calcining process in the step (3) is to calcine for 1.5 to 2 hours at the temperature of 600 to 800 ℃ in a tubular furnace under the nitrogen atmosphere.

Further, the lanthanum salt aqueous solution in the step (2) is a lanthanum nitrate aqueous solution; the molar concentration of the lanthanum salt aqueous solution is 0.05 mol/L-0.1 mol/L; the mass volume ratio of the amaranth-based carbon powder to the lanthanum salt aqueous solution is 1g:25 mL.

Further, the temperature of the ultrasonic treatment in the step (2) is not more than 30 ℃, the ultrasonic power is 800-1000W, and the ultrasonic time is 0.5-1 h.

Further, the mass ratio of the lanthanum oxide/amaranth-based carbon nanocomposite material to the potassium thiocyanate in the step (3) is 1 (3-5).

The invention also provides a nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material prepared by the preparation method.

The third aspect of the invention provides an application of the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite material prepared by the preparation method in hydrogen production by water electrolysis, and the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite material is used as an electrocatalytic material on an electrode material in hydrogen production by water electrolysis.

Further, the application method comprises the following steps: uniformly dispersing the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material into a mixed solution of Nafion resin, water and ethanol to prepare the electro-catalysis material, coating the electro-catalysis material on nickel foam, and drying to obtain the electrode material, wherein the electrode material comprises a cathode and an anode;

the mass ratio of the Nafion resin to the water to the ethanol is 1:2: 7; the loading capacity of the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite on the nickel foam is 0.4 mg/cm.

In the last aspect of the invention, the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite prepared by the preparation method is applied to a supercapacitor, and the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite is used as an electrode of the supercapacitor.

Further, the application method comprises the following steps: uniformly dispersing the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nano composite material in a mixed solution of Nafion resin, water and ethanol, then coating the mixed solution on nickel foam, drying to obtain the electrode, and immersing the middle of two identical electrodes in a PVA-KOH gel electrolyte at intervals by a diaphragm to assemble a symmetrical supercapacitor;

the mass ratio of the Nafion resin to the water to the ethanol is 1:2: 7; the loading capacity of the nitrogen and sulfur element doped lanthanum oxide/amaranth-based carbon nanocomposite on the nickel foam is 0.4 mg/cm.

The amaranth is used as a carbon source precursor, the amaranth-based carbon powder material with the porous three-dimensional network structure is formed by a high-temperature carbonization mode, and has higher specific surface area and porosity, mainly because the microstructure of the amaranth which is a common natural plant is a mutually staggered net-shaped structure, the main elements in the amaranth are carbon elements, and the amaranth also contains some non-carbon elements such as nitrogen, sulfur, phosphorus, oxygen, potassium, magnesium, calcium and the like;

according to the method, amaranth-based carbon powder prepared after pre-carbonization and lanthanum nitrate are subjected to hydrothermal reaction at high temperature and high pressure, a large number of lanthanum oxide nanocrystals grow out in a porous three-dimensional network structure of the amaranth-based carbon powder in the process to form a lanthanum oxide/amaranth-based carbon nanocomposite, lanthanum oxide has good conductivity, surface effect and volume effect, and can be subjected to in-situ compounding with the amaranth-based carbon powder to form active sites on a carbon material; and then mixing the carbon nano composite material with potassium thiocyanate and then carrying out high-temperature calcination, wherein the potassium thiocyanate contains nitrogen and sulfur, so that the lanthanum oxide/amaranth-based carbon nano composite material can be doped by the nitrogen and the sulfur in the high-temperature calcination process, and the finally prepared nitrogen and sulfur doped lanthanum oxide/amaranth-based carbon nano composite material has higher specific surface area and porosity and better electrochemical performance, can be used as an electrode material for hydrogen production by water electrolysis to obtain lower hydrogen evolution potential, and can be used for a super capacitor to obtain higher specific capacitance and higher capacity retention rate.

The beneficial technical effects are as follows:

(1) the method comprises the following steps of (1) discarding expensive traditional carbon sources such as graphene and carbon nanotubes, selecting common natural plants such as amaranth as carbon source precursors, wherein the common natural plants are rich in alkali metal and alkaline earth metal elements, and the metal elements can promote amaranth-based carbon materials to form a porous three-dimensional network structure in a high-temperature carbonization process in an ion migration mode, so that transfer of electrons and ions can be promoted in the aspect of electrochemistry, and the electrochemical performance is improved; the amaranth has low cost and wide source, is sometimes used as agricultural waste, and is made into a composite material by changing the waste of the amaranth into valuable to be applied to an electrode material, so that the environmental pollution is treated, and the high-value resource conversion of biological waste is realized.

(2) The method is characterized in that a high-temperature and high-pressure environment generated by a hydrothermal reaction kettle in a closed state is utilized, so that lanthanum ions are combined with oxygen ions in a solution to form lanthanum oxide nano crystal grains, the lanthanum oxide nano crystal grains grow in a porous three-dimensional network structure of the amaranth-based carbon powder material, the electron cloud distribution of the carbon material is changed to become active sites of carbon, the carbon material is activated to a great extent, and the electrochemical performance of the carbon material is improved.

(3) The carbon material has good cycling stability and corrosion resistance, but the electrochemical performance of the carbon material is not ideal when the carbon material is used as an electrode material in a super capacitor and electrocatalytic hydrogen production; although the lanthanum oxide has good conductivity, the lanthanum oxide has poor corrosion resistance and is particularly easy to be corroded by acid; according to the method, the carbon material is subjected to in-situ compounding by doping the impurity element and lanthanum oxide, and a synergistic effect is formed by integrating the porous three-dimensional network structure of the amaranth-based carbon powder material, the lanthanum oxide and the impurity element doping, so that the electrode material with ideal electrochemical performance is obtained, and the application range of the electrode material is expanded.

(4) The preparation method is simple and convenient to operate, low in cost and easy to regulate, can be applied to the field of new energy sources for energy storage and conversion and hydrogen production, and replaces some materials with high price and narrow application range.

Drawings

FIG. 1 is a scanning electron microscope photograph of amaranth after pre-carbonization in step (1) of example 1.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Unless specifically stated otherwise, the numerical values set forth in these examples do not limit the scope of the invention. Techniques, methods known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.