CN117317128A - Electrode and preparation method and application thereof - Google Patents

Electrode and preparation method and application thereof Download PDF

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Publication number
CN117317128A
CN117317128A CN202311101430.8A CN202311101430A CN117317128A CN 117317128 A CN117317128 A CN 117317128A CN 202311101430 A CN202311101430 A CN 202311101430A CN 117317128 A CN117317128 A CN 117317128A
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metal
ions
reaction
conductive substrate
electrode
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孙朱行
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Xi'an Longji Hydrogen Energy Technology Co ltd
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Xi'an Longji Hydrogen Energy Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

The application provides an electrode, a preparation method and application thereof, wherein the electrode comprises the following components: a conductive substrate, an intermediate connection layer, and a hydrotalcite compound layer laminated in this order; wherein the conductive substrate comprises a first metal; the intermediate connection layer comprises a second metal; the first metal is more reactive than the second metal; the cations in the hydrotalcite compound layer include ions of a first metal and ions of a second metal. The intermediate connecting layer of the electrode can play a good role in covering and protecting the conductive substrate, so that the conductive substrate is prevented from being corroded in the using process, and the long-term using stability of the material is improved; and the hydrotalcite compound layer has proper plate (/ rod) body, and has enough active matter content on the conductive substrate in unit area, thus improving the electrical property of the electrode.

Description

Electrode and preparation method and application thereof
Technical Field
The application relates to the technical field of electrochemistry, in particular to an electrode, a preparation method and application thereof.
Background
Layered double hydroxides (LDHs, also known as hydrotalcite) are novel inorganic functional materials with layered structures, and have the composition general formula of [ M ] 1-x 2+ M x 3+ (OH) 2 ] x+ (A n- )·mH 2 O, where M 2+ Is Mg 2+ 、Ni 2+ 、Co 2+ 、Zn 2+ 、Cu 2+ Equal divalentMetal cation, M 3+ Is Al 3+ 、Cr 3+ 、Fe 3+ 、Sc 3+ An aliovalent metal cation; divalent metal ion M 2+ With trivalent metal ions M 3+ The molar content ratio of (2) is as follows: m is M 2+ /M 3+ ＝2～4；A n- Being anionic, e.g. CO 3 2- 、NO 3 - 、Cl - 、OH - 、SO 4 2- 、PO 4 3- 、C 6 H 6 (COO - ) 2 Such inorganic and organic ions and complex ions; n is the charge number of the anion. Because of its easily-regulated chemical properties and unique two-dimensional structure, hydrotalcite materials have been attracting attention in the fields of photo/electro-catalytic water decomposition oxygen production, carbon dioxide reduction and the like. However, bulk hydrotalcite materials have the disadvantages of low conductivity, insufficient exposure of active sites, and limited catalytic activity. Hydrotalcite nano material is vertically grown on the surface of the conductive substrate in situ, so that the charge conduction capacity and the effective exposure area of the hydrotalcite material can be effectively improved.
Generally, salts of the required metals are used as precursors, and hydrotalcite nano materials such as nickel-iron, nickel-cobalt, iron-cobalt-nickel and the like are grown on the surface of a conductive substrate with macroscopic porous and microscopic surface such as foam nickel, carbon paper and the like in situ, but the obtained water skid material has the problems of thicker layer, poor stability and conductivity and the like.
In order to solve the problems, the prior method directly takes a substrate as a certain metal source and uses a solution containing both the precursor and a sedimentation agent (reducing agent) to synthesize the hydrotalcite material, but the obtained water-skid material layer is thinner due to the limited content of metal ions released by the metal source, the active matter content on the substrate material per unit area is limited, and the corrosion resistance of the substrate (such as an iron substrate) which can be taken as the metal source is poor, although the surface of the substrate grows hydrotalcite to have a certain covering protection effect, the corrosion of the conductive substrate in the using process is difficult to avoid, and the long-term use stability of the material is poor.
Disclosure of Invention
In order to solve the problems in the prior art, the application provides an electrode, and a preparation method and application of the electrode. The technical scheme of the application is as follows:
1. an electrode, comprising:
a conductive substrate, an intermediate connection layer, and a hydrotalcite compound layer laminated in this order; wherein,
the conductive substrate includes a first metal;
the intermediate connection layer comprises a second metal;
the first metal is more reactive than the second metal;
the cations in the hydrotalcite compound layer include ions of a first metal and ions of a second metal.
2. The electrode according to item 1, wherein,
the thickness of the intermediate connection layer is 0.01-10 μm, preferably 0.05-5 μm.
3. The electrode according to item 1, wherein,
the hydrotalcite compound layer has a thickness of 0.1 to 20. Mu.m, preferably 0.5 to 10. Mu.m.
4. The electrode according to item 1, wherein,
the first metal is selected from one or more than two of iron, cobalt and nickel;
the second metal is selected from one or more of cobalt, nickel, tin, lead, copper, mercury, silver, platinum and gold.
5. The electrode according to item 1, wherein,
the cations in the hydrotalcite compound layer further include ions of a third metal;
the third metal is more reactive than the first metal.
6. The electrode according to item 5, wherein,
the third metal is selected from one or more than two of potassium, barium, calcium, sodium, magnesium, aluminum, manganese, zinc, chromium, iron and cobalt.
7. A method of making an electrode comprising:
a displacement reaction step of placing a conductive substrate in a first solution under an inert atmosphere or a reducing atmosphere, wherein the conductive substrate comprises a first metal containing ions of a second metal, the first metal being more reactive than the second metal so that the ions of the first metal and the second metal undergo a displacement reaction, the ions of the second metal being displaced to form an intermediate connection layer on the surface of the conductive substrate, and obtaining a second solution containing the ions of the first metal and the ions of the second metal; the intermediate connection layer comprises a second metal;
and a coprecipitation reaction step, wherein a precipitant is introduced into the second solution to carry out a coprecipitation reaction, so as to form a hydrotalcite compound layer on the surface of the intermediate connecting layer, wherein cations in the hydrotalcite compound layer comprise ions of a first metal and ions of a second metal.
8. The electrode according to item 7, wherein,
the thickness of the intermediate connection layer is 0.01-10 μm, preferably 0.05-5 μm.
9. The electrode according to item 7, wherein,
the hydrotalcite compound layer has a thickness of 0.1 to 20. Mu.m, preferably 0.5 to 10. Mu.m.
10. The method according to item 7, wherein,
the inert atmosphere is kept by introducing inert gas into the reaction vessel before or during the displacement reaction.
11. The method according to item 7, wherein,
the reducing atmosphere is maintained by introducing a reducing gas and/or adding a reducing solid into the reaction vessel before or during the displacement reaction.
12. The method according to item 7, wherein,
the first metal is selected from one or more than two of iron, cobalt and nickel; and/or the number of the groups of groups,
the second metal is selected from one or more of cobalt, nickel, tin, lead, copper, mercury, silver, platinum and gold.
13. The method of item 12, wherein,
the first metal is iron and the second metal is nickel.
14. The method according to item 7, wherein,
the concentration of the ions of the second metal in the first solution is 0.05 to 1mol/L, preferably 0.1 to 0.5mol/L.
15. The method according to item 7, wherein,
the reaction temperature of the displacement reaction is 20-60 ℃ and the reaction time is 1-60 min;
preferably, the reaction temperature is 35-50 ℃ and the reaction time is 5-30 min.
16. The method according to item 7, wherein,
the precipitant is one or more of organic alkali or inorganic alkali, preferably one or more of urea, thiourea, sodium bicarbonate, sodium carbonate, sodium lignin and sodium acetate; and/or the number of the groups of groups,
the molar content of the precipitant is 0.025-2 mol/L, preferably 0.05-1 mol/L.
17. The method according to item 7, wherein,
the introducing the precipitant comprises:
adding a precipitant to the second solution through a pipeline; and/or the number of the groups of groups,
the first solution is pre-filled with an encapsulant-encapsulated precipitant, and the light, heat or aqueous solution is capable of releasing the encapsulant to introduce the precipitant into the second solution.
18. The method according to item 7, wherein,
the reaction temperature of the coprecipitation reaction is 20-150 ℃;
preferably, the coprecipitation reaction is carried out under normal pressure, and the reaction temperature is 50-100 ℃; or the coprecipitation reaction is carried out under the sealed hydrothermal condition, and the reaction temperature is 100-130 ℃.
19. The method of item 18, wherein,
the reaction time of the coprecipitation reaction is 2 to 48 hours, preferably 6 to 24 hours.
20. The method according to item 7, wherein,
before the displacement reaction step, a pretreatment step is also included,
the pretreatment step includes removing impurities from the conductive substrate.
21. The method of item 20, wherein,
the impurity removal comprises one or more of acid washing, alkali washing, organic solvent washing and water washing.
22. The method according to item 7, wherein,
the first solution also contains ions of a third metal;
the third metal is more reactive than the first metal.
23. The method of item 22, wherein,
the third metal is selected from one or more than two of potassium, barium, calcium, sodium, magnesium, aluminum, manganese, zinc, chromium, iron and cobalt.
24. Use of the electrode according to any one of claims 1 to 6 in electrochemistry.
According to the electrode, the electrode sequentially comprises the relatively active conductive substrate, the relatively inactive intermediate connecting layer and the multilayer structural material corresponding to the metal hydrotalcite from inside to outside, and the intermediate connecting layer of the electrode can play a good role in covering and protecting the conductive substrate, so that the conductive substrate is prevented from being corroded in the use process, and the long-term use stability of the material is improved; and the hydrotalcite compound layer has proper plate (/ rod) body, and has enough active matter content on the unit area conductive substrate to improve the electrical performance of the electrode.
The foregoing description is only an overview of the technical solutions of the present application, to the extent that it can be implemented according to the content of the specification by those skilled in the art, and to make the above-mentioned and other objects, features and advantages of the present application more obvious, the following description is given by way of example of the specific embodiments of the present application.
Drawings
Fig. 1: scanning electron microscopy of the hydrotalcite compound layer of the electrode surface layer in one embodiment;
fig. 2: scanning electron microscopy of electrode cross-sections in one embodiment;
fig. 3: in one embodiment the surface layer of the conductive substrate is scraped to obtain an X-ray diffraction pattern of the powder material.
Detailed Description
The following embodiments of the present application are merely illustrative of specific embodiments for practicing the present application and are not to be construed as limiting the present application. Any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principles of the present application are intended to be equivalent arrangements which are within the scope of the present application.
The present embodiment provides a method of preparing an electrode, comprising:
a displacement reaction step of placing a conductive substrate in a first solution under an inert atmosphere or a reducing atmosphere, wherein the conductive substrate comprises a first metal containing ions of a second metal, the first metal being more reactive than the second metal so that the ions of the first metal and the second metal undergo a displacement reaction, the ions of the second metal being displaced to form an intermediate connection layer on the surface of the conductive substrate, and obtaining a second solution containing the ions of the first metal and the ions of the second metal;
and a coprecipitation reaction step, wherein a precipitant is added into the second solution to carry out a coprecipitation reaction, so as to form a hydrotalcite compound layer on the surface of the intermediate connecting layer, and cations in the hydrotalcite compound layer comprise ions of a first metal and ions of a second metal.
The terms "first", "second", "third", etc. in the present application are used only to distinguish different metal materials. Wherein the metal may include only one metal element or two metal elements.
The first metal and the second metal are not particularly limited, and the first metal and the ions of the second metal can undergo a substitution reaction, and metal ions formed by the first metal which participates in the substitution reaction and ions of the remaining second metal which does not participate in the substitution reaction can participate in a coprecipitation reaction to form a hydrotalcite compound layer.
The first metal being more reactive than the second metal in the present application means that all metal elements in the first metal are more reactive than the metal elements of the second metal. Of course, the conductive substrate may further include other conductive materials (such as other metals that do not affect the substitution reaction described above) other than the first metal, and the first solution may also contain other metal ions (such as ions of a third metal below) other than the second metal ions.
Those skilled in the art will appreciate that in the above displacement reaction step, the ions of the second metal are displaced, so that a thin intermediate connection layer can be formed on the surface of the conductive substrate, and a second solution is obtained, where the second solution contains the ions of the first metal and the ions of the second metal; the intermediate connection layer comprises a second metal. When the metal cations in the first solution are ions of only the second metal, the intermediate connection layer includes only the second metal.
The activity sequence table of common metals is: potassium, barium, calcium, sodium, magnesium, aluminum, manganese, zinc, chromium, iron, cobalt, nickel, tin, lead, (hydrogen), copper, mercury, silver, platinum, gold. The weaker the metal activity of the metal at the later position in the metal activity sequence table, the weaker the reducibility of the atoms; the more active the metal is, the more reducing the atoms are. The metals that are displaced in front can displace the metals that are displaced in rear from their salt solutions. The sequence of substitution reactions of the mixed salt solution with a metal is "far before" and "near after". In other words, the metal ions that are displaced behind can react with the surface of the metal that is displaced ahead, displacing the ions of the metal that is displaced ahead; when a solution containing two kinds of metal ions arranged at the back is contacted and reacted with the metal arranged at the front, the metal ions far away preferentially participate in the reaction to replace the metal ions arranged at the front. For example, from the above metal activity sequence, elemental iron may undergo a substitution reaction with cobalt or nickel ions to produce ferrous ions, which then oxidize to ferric ions in an oxidizing environment.
As described in the background, in hydrotalcite compounds, divalent metal ions M 2+ And trivalent metal ion M 3 + The molar content ratio of (2) is as follows: m is M 2+ /M 3+ =2 to 4. Therefore, it is known to those skilled in the art that when the metal cations in the hydrotalcite compound layer are derived from only the first metal and the second metal, then the metal elements contained in the first metal and the second metal contain metal elements whose cations are divalent and trivalent; when part of the metal cations in the hydrotalcite compound layer are derived from other sources (the third metal hereinafter) than from the first metal, the second metal, then the metal elements contained in the other sources, the first metal and the second metal contain a metal element whose cations are divalent and a metal element which is trivalent.
The anion corresponding to the ion of the second metal may be CO 3 2- ,NO 3 - ,Cl - ,SO 4 2- ,PO 4 3- ,C 6 H 4 (COO) 2 2- And inorganic, organic or complex ions.
By maintaining an inert atmosphere or a reducing atmosphere, the intermediate connection layer formed by substitution can be prevented from being oxidized. In regard to maintaining the inert atmosphere, an inert gas (such as nitrogen, argon, helium, etc.) may be introduced into the reaction vessel before or during the displacement reaction. In regard to maintaining the reducing atmosphere, a reducing gas (e.g., hydrogen gas, etc.) and/or a small amount of a reducing solid (e.g., sodium borohydride, etc.) may be introduced into the reaction vessel before or during the displacement reaction.
Regarding co-precipitation, essentially two basic processes are involved: (1) participating in a coprecipitation nucleation process of metal ions; and (2) hydrotalcite nucleus growth process. Wherein in process (1) the control of the pH of the solution is critical.
The electrode is mainly used for electrochemistry (such as electrocatalysis and the like), and is particularly used for reactions such as water decomposition, oxygen reduction, pollutant degradation or organic matter conversion or super capacitors.
According to the technical scheme, compared with the prior art, the adding time of the precipitant is postponed, so that the conductive substrate (the material is the first metal) is guaranteed to provide metal cations for forming the hydrotalcite compound layer, and part of ions of the second metal are replaced to form an intermediate connecting layer with lower metal activity on the conductive substrate, and enough ions of the first metal can be contained in the second solution while the intermediate connecting layer is formed, so that the subsequent generation of the hydrotalcite compound layer is facilitated; compared with the prior art, the control of the reaction atmosphere (inert atmosphere and/or reducing atmosphere) ensures that the intermediate connecting layer is not oxidized in the reaction process, thereby saving precursors; the middle connecting layer can play a good role in covering and protecting the conductive substrate, so that the conductive substrate is prevented from being corroded in the using process, and the long-term use stability of the material is improved; the sheet (/ rod) body of the hydrotalcite compound layer is ensured to be proper, and the active matter content on the conductive substrate per unit area is enough.
After the above-described method for preparing an electrode is given, it is known to those skilled in the art that an electrode which can be used for electrochemistry (e.g., electrocatalysis, etc.) can be obtained by the above-described method, which comprises a conductive substrate, an intermediate connection layer, and a hydrotalcite compound layer laminated in this order; wherein the conductive substrate comprises a first metal; the intermediate connection layer comprises a second metal; the first metal is more reactive than the second metal; the cations in the hydrotalcite compound layer include ions of a first metal and ions of a second metal. Specifically, the electrode can sequentially comprise a more active conductive substrate, a less active intermediate connecting layer and a multilayer structure material corresponding to metal hydrotalcite from inside to outside. The middle connecting layer of the electrode can play a good role in covering and protecting the conductive substrate, prevent the conductive substrate from being corroded in the use process, and improve the long-term use stability of the material; and the hydrotalcite compound layer has a suitable sheet (/ rod) body and a sufficient amount of active material per unit area of the conductive substrate.
In a preferred embodiment, the intermediate connection layer is between 0.01 and 10 μm (in particular, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or 9 μm), preferably between 0.05 and 5 μm, so as to ensure a protective covering of the conductive substrate, to prevent the conductive substrate from being corroded during use, to improve the stability and the service life of the material.
Specifically, the thickness of the intermediate connection layer may be controlled by controlling the amount of the second metal to be displaced by controlling the time, temperature, etc. of the displacement reaction.
In a preferred embodiment, the hydrotalcite compound layer has a thickness of 0.1 to 20 μm (specifically, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or 19 μm), preferably 0.5 to 10 μm. Thereby maintaining a sufficient active area and a high stability.
Specifically, the thickness of the hydrotalcite compound layer may be controlled by controlling the content of the second metal ions in the first solution, the amount of ions of the first metal that enter the second solution through the substitution reaction, and the like.
In a preferred embodiment, the first metal is selected from one or a combination of more than two of iron, cobalt, nickel; and/or the number of the groups of groups,
the second metal is selected from one or more of cobalt, nickel, tin, lead, copper, mercury, silver, platinum and gold.
Iron, cobalt and nickel are not noble metals, and the combination of one, two or three of the noble metals is used as a conductive substrate, so that the manufacturing cost of the electrode can be obviously reduced.
In particular, the electrode may be prepared using iron as the first metal and cobalt and/or nickel as the second metal, thereby minimizing electrode costs while improving electrode performance.
It is to be noted that, from the solubility product and the ion concentration of each of the common metal hydroxides in table 1 below at normal temperature, the pH value of the precipitation is similar to that of the divalent iron ion, the divalent nickel ion and the divalent cobalt ion (the lower the pH value required for precipitation is defined as the easier the precipitation), and the trivalent iron and the trivalent cobalt are more likely to precipitate than the above three. Ferric ions are more stable than ferrous ions, so ferric salts are generally used as precursors in hydrotalcite synthesis. In the general synthesis process of ferronickel hydrotalcite added with all precursor ions, the ferronickel ratio in the obtained ferronickel hydrotalcite is generally lower than that in the additive because iron ions are easier to precipitate.
Table 1: ksp of solubility product, beginning (0.01 mol/L) and complete precipitation of different metal hydroxides at normal temperature<10 - 5 mol/L) pH value
For cobalt, non-complexed bivalent cobalt ions are more stable than trivalent cobalt ions, the divalent cobalt ions precipitate slower, and when the cobalt ions and the iron ions co-precipitate to produce iron-cobalt hydrotalcite, cobalt in the hydrotalcite is mainly bivalent; and cobalt ions and nickel ions form hydrotalcite, wherein cobalt in the hydrotalcite exists in divalent and trivalent states. In the synthesis of nickel cobalt hydrotalcite, it is necessary to ensure a high oxidizing property of the environment.
In a preferred embodiment, the concentration of the second metal ion in the first solution is 0.05 to 1mol/L (specifically, 0.1mol/L, 0.2mol/L, 0.3mol/L, 0.4mol/L, 0.5mol/L, 0.6mol/L, 0.7mol/L, 0.8mol/L or 0.9 mol/L), preferably 0.1 to 0.5mol/L.
The adoption of the second metal ions with the concentration is favorable for ensuring the formation of an intermediate connecting layer with a certain thickness and simultaneously forming a hydrotalcite compound layer with a proper thickness and a proper size of a nano sheet (/ rod).
In a preferred embodiment, the metathesis reaction is carried out at a reaction temperature of 20 to 60 ℃ (specifically, such as 30 ℃, 40 ℃ or 50 ℃), and a reaction time of 1 to 60 minutes (specifically, such as 10 minutes, 20 minutes, 30 minutes, 40 minutes or 50 minutes); preferably, the reaction temperature is 35-50 ℃ and the reaction time is 5-30 min.
Under the above reaction conditions, it is advantageous to form an intermediate connection layer of a certain thickness and release enough ions of the first metal into the second solution.
In a preferred embodiment, the precipitating agent is one or more of organic base or inorganic base, and is selected from one or more of urea, thiourea, sodium bicarbonate, sodium carbonate, sodium lignin and sodium acetate; and/or adding the precipitant to the reaction system in a molar amount of 0.025 to 2mol/L (specifically, 0.2mol/L, 0.4mol/L, 0.6mol/L, 0.8mol/L, 1mol/L, 1.2mol/L, 1.4mol/L, 1.6mol/L or 1.8 mol/L), preferably 0.05 to 1mol/L.
The person skilled in the art can select suitable precipitants as described above. In addition, the above-mentioned precipitants in a molar amount (about 0.5 to 2 times, preferably 0.8 to 1.2 times the total molar amount of the salt precursor) are advantageous for forming a hydrotalcite compound layer of a suitable thickness.
Since the above-mentioned precipitants mainly play a role in coprecipitation by adjusting pH, the precipitants may also be referred to as pH adjusters in the present application.
In a preferred embodiment, the introducing the precipitation agent comprises: adding a precipitant to the second solution through a pipeline; and/or, the first solution is pre-provided with the precipitant wrapped by the encapsulant, and the light, heat or water solution can enable the encapsulant to release the precipitant so as to introduce the precipitant into the second solution.
In this embodiment, two schemes of adding precipitants are provided, wherein a pipeline, such as a preset dropper, can be arranged for dripping without damaging the reaction environment. In addition, an encapsulant which does not affect the reaction may be coated on the surface of the precipitant. The encapsulant can be low-melting solid alkane or solid ester, and can be alkane or ester with melting point of 22-100deg.C, such as C 17 -C 32 One or more than two of alkanes can be paraffin, candle wax, spermaceti wax, beeswax, etc., adding precipitant coated with fusible material into reaction system, heating the reaction system to a temperature higher than the melting point of fusible material when coprecipitation reaction is required, releasing precipitant to raise pH value of the second solution, and promoting ion coprecipitation in the second solution to generate waterA talc compound layer. The encapsulating agent can also be water-soluble capsules, and the thickness of the capsules is controlled so as to control the time for releasing the precipitant.
In a preferred embodiment, the reaction temperature of the coprecipitation reaction is 20 to 150 ℃ (specifically, such as 40 ℃,60 ℃, 80 ℃, 100 ℃, 120 ℃ or 140 ℃);
preferably, the coprecipitation reaction is carried out under normal pressure, and the reaction temperature is 50-100 ℃; or the coprecipitation reaction is carried out under the sealed hydrothermal condition, and the reaction temperature is 100-130 ℃.
The above temperature is favorable for the coprecipitation reaction to take place and for the hydrotalcite compound layer with proper thickness to be formed.
In particular, when the reaction is carried out under normal pressure at a reaction temperature of 50 to 100℃or under sealed hydrothermal conditions at a reaction temperature of 100 to 130℃the coprecipitation reaction is carried out at a temperature higher than the displacement reaction, and therefore, a temperature increase is required during the conversion from the displacement reaction to the coprecipitation reaction, and at this time, the above-mentioned fusible material (having a melting point higher than the displacement reaction temperature and lower than the coprecipitation reaction temperature) may be appropriately selected so that the precipitant is automatically released during the temperature increase converted to the coprecipitation reaction.
And the reaction time of the coprecipitation reaction is controlled to be in the range of 2 to 48 hours, preferably 6 to 24 hours, which is advantageous for forming a hydrotalcite compound layer of a suitable thickness.
In a preferred embodiment, a pretreatment step is further included prior to the metathesis step,
the pretreatment step includes removing impurities from the conductive substrate.
Specifically, the impurity removal comprises one or more of acid washing, alkali washing, organic solvent washing and water washing.
The impurity removal is beneficial to ensuring the cleanliness of the conductive substrate and improving the catalytic performance of the finally prepared electrode.
In a preferred embodiment, the first solution further contains ions of a third metal; the third metal is more reactive than the first metal.
The third metal being more reactive than the first metal in this application means that all metal elements in the third metal are more reactive than the metal elements in the first metal. So that the ions of the third metal do not participate in the displacement reaction.
The third metal is not particularly limited as long as ions of the third metal do not undergo a substitution reaction with the first metal in the substitution reaction.
For example, when the first metal is elemental iron, the ion of the third metal may be one or a combination of two or more of potassium, barium, calcium, sodium, magnesium, aluminum, manganese, zinc, chromium, and the like; when the first metal is cobalt simple substance, the ion of the third metal can be one or the combination of more than two of ions such as potassium, barium, calcium, sodium, magnesium, aluminum, manganese, zinc, chromium, iron and the like; for example, when the first metal is a simple substance of nickel, the ion of the third metal may be one or a combination of two or more of ions such as potassium, barium, calcium, sodium, magnesium, aluminum, manganese, zinc, chromium, iron, cobalt, and the like.
Wherein the total molar concentration of the barium, the calcium, the magnesium, the aluminum, the manganese, the zinc, the chromium, the iron and the cobalt is less than or equal to 0.1mol/L; for ions such as sodium, potassium and the like which are not easy to precipitate in alkaline environment, the concentration is not limited.
Thus, one skilled in the art may introduce appropriate metal ions into the hydrotalcite compound layer as needed to obtain different hydrotalcite compound layers, not just ions of the first metal having a metal activity of not less than that of the first metal.
Examples
The experimental methods used below are conventional methods if no special requirements are imposed.
Materials, reagents and the like used in the following are commercially available unless otherwise specified.
Example 1
Will be 1X 2cm 2 The surface layer is a metal net (46 mesh, wire diameter 350 μm) with iron conductive substrate layer, and is pretreated (cleaned by acetone, 0.5M H) 2 SO 4 Immersing for 3min, washing with pure water), placing in a three-neck flask containing 50mL of 0.1mol/L nickel nitrate solution, and purging with nitrogen for 15min to maintain an inert atmosphere in the flaskSurrounding, heating the flask to 45 ℃ by adopting a water bath kettle while keeping nitrogen purging, and keeping the temperature for 30min;
then, dropwise adding 5mL of urea solution containing 5mmol of urea as a precipitator, heating to 80 ℃ at the same time, and reacting for 8 hours;
and then taking out the iron net (electrode) deposited with the composite material, washing with ethanol and deionized water, and drying in a 60 ℃ oven.
Fig. 1 is a Scanning Electron Microscope (SEM) image of a surface hydrotalcite compound layer of an electrode, and it can be seen from the image that the hydrotalcite compound layer is formed by stacking spheres composed of nano-sheets.
FIG. 2 is a Scanning Electron Microscope (SEM) image of a cross section of an electrode, the hydrotalcite compound layer having a thickness of about 2. Mu.m.
FIG. 3 is an X-ray diffraction pattern of a powder material scraped from the surface layer of a conductive substrate, and diffraction peaks of elemental nickel and ferronickel hydrotalcite can be obtained.
For convenience of description, hereinafter, detection of a Scanning Electron Microscope (SEM) of the hydrotalcite compound layer on the surface layer of the electrode, a Scanning Electron Microscope (SEM) of the cross section of the electrode, and an X-ray diffraction pattern of the powder material scraped from the surface layer of the conductive substrate will be simply referred to as "characterization analysis".
The obtained electrode can be directly used as an anode for water electrolysis, a three-electrode system (Pt is a counter electrode and mercury/mercury oxide is a reference electrode) is adopted, the change of anode current density with time when the electrode is subjected to Infrared Ray (IR) correction under the condition of over-potential of 0.37V vs RHE (namely, under the condition of over-potential of 0.37V) is tested in 1M KOH electrolyte, and the detection result is shown in table 2.
Comparative example 1
Comparative example 1 differs from example 1 only in the way urea is added, in order to be placed directly with the conductive substrate into the nickel nitrate solution, the flask temperature is directly raised to 80 ℃, and the reaction is carried out for 8 hours.
The thickness of the hydrotalcite compound layer of the obtained electrode is about 0.3 μm after characterization analysis; the content of the simple substance nickel is low, and an obvious diffraction peak of the simple substance nickel (namely, the middle connecting layer is not obvious) cannot be detected.
The resulting electrode was subjected to the same anode current density change with time as in example 1, and specific parameters are shown in Table 2.
Example 2
The conductive substrate was the same as in example 1, with 1.6mmol of cobalt nitrate and 3mmol of nickel acetate as cobalt and nickel precursors and 8mmol of thiourea as precipitant (wrapped with 2.5g of paraffin wax).
Dissolving cobalt nitrate and nickel acetate in 60mL of deionized water, adding the solution into a pressure-resistant hydrothermal reaction kettle, adding thiourea wrapped by 2.5g of paraffin, purging nitrogen to keep an inert atmosphere in the kettle, and sealing the reaction kettle; reacting at 50deg.C for 25min;
then, the temperature was raised to 130 ℃ (paraffin was melted), reacted for 10 hours, and then naturally cooled.
And then taking out the iron net (electrode) deposited with the composite material, washing with ethanol and deionized water, and drying in a 60 ℃ oven.
The appearance of the hydrotalcite compound layer of the obtained electrode is a sphere stacking display formed by assembling nano sheets through characterization analysis; a thickness of about 2 μm; diffraction peaks of the simple substance nickel, nickel-iron-cobalt hydrotalcite and nickel-cobalt hydrotalcite can be obtained.
The resulting electrode was subjected to the same anode current density change with time as in example 1, and specific parameters are shown in Table 2.
Comparative example 2
Comparative example 2 differs from example 2 only in that thiourea was not coated with paraffin wax.
The thickness of the hydrotalcite compound layer of the obtained electrode is about 0.5 μm through characterization analysis; no obvious X-ray diffraction peak of elemental nickel or cobalt (i.e., no obvious intermediate tie layer).
The resulting electrode was subjected to the same anode current density change with time as in example 1, and specific parameters are shown in Table 2.
Example 3
The conductive substrate of example 3 was the same as that of example 1,5mmol of cobalt nitrate as the cobalt precursor and 5mmol of sodium bicarbonate as the precipitant (wrapped with 3g of paraffin wax).
Dissolving the cobalt nitrate in 40mL of deionized water, adding a 100mL three-neck flask, adding the sodium bicarbonate wrapped by 3g of paraffin, purging the upper end of the flask with nitrogen for 20min, maintaining 50 ℃, placing the conductive substrate, closing bottle mouths at two ends, connecting the bottle mouths in the middle for reflux condensation, and stirring the solution;
then, heating to 90 ℃ after 28min, reacting for 6 hours, and naturally cooling;
and then taking out the iron net (electrode) deposited with the composite material, washing with acetone, ethanol and deionized water, and drying in a 60 ℃ oven.
The appearance of the hydrotalcite compound layer of the obtained electrode is a regular array formed by staggering vertically grown nano-sheets through characterization analysis; a thickness of about 1.5 μm; diffraction peaks of cobalt-iron hydrotalcite and smaller elemental cobalt can be obtained.
The resulting electrode was subjected to the same anode current density change with time as in example 1, and the detection results are shown in Table 2.
Comparative example 3
The conductive substrate of comparative example 3 was the same as example 1,5mmol of cobalt nitrate as the cobalt precursor and 5mmol of sodium bicarbonate as the precipitant (without paraffin encapsulation).
Dissolving the cobalt nitrate and the sodium bicarbonate in 40mL of deionized water, adding the sodium bicarbonate into a 100mL three-neck flask, placing the conductive substrate, reacting for 6 hours at 90 ℃, and naturally cooling;
and then taking out the iron net (electrode) deposited with the composite material, washing with acetone, ethanol and deionized water, and drying in a 60 ℃ oven.
The hydrotalcite compound layer of the obtained electrode has smaller thickness, about 0.4 μm after characterization analysis; no significant elemental cobalt X-ray diffraction peaks (i.e., no significant intermediate tie layer).
The resulting electrode was subjected to the same anode current density change with time as in example 1, and the detection results are shown in Table 2.
Example 4
Example 4 differs from example 1 only in that the conductive substrate of example 4 is foamed cobalt (cobalt purity 99.9%, area 1cm x 2cm, thickness 1mm, cell number 75-110 ppi) and the foamed cobalt has been pretreated (acetone cleaning, 0.5M H) 2 SO 4 Immersing and washing for 3min, and washing with pure water).
The appearance of the hydrotalcite compound layer of the obtained electrode is that vertically grown nano rods form a ball stacking array through characterization analysis; a thickness of about 0.8 μm; the diffraction peak of the simple substance nickel and nickel cobalt hydrotalcite can be obtained.
The resulting electrode was subjected to the same anode current density change with time as in example 1, and the detection results are shown in Table 2.
Comparative example 4
Comparative example 4 differs from comparative example 1 only in that the conductive substrate was a foamed cobalt (cobalt purity 99.9%, area 1cm x 2cm, thickness 1mm, cell number 75-110 ppi) and the foamed cobalt was pretreated (acetone cleaning, 0.5M H) 2 SO 4 Immersing and washing for 3min, and washing with pure water).
The thickness of the hydrotalcite compound layer of the obtained electrode is 0.4 mu m through characterization analysis; the analysis by X-ray diffraction shows that the surface of the substrate is mainly nickel-cobalt hydrotalcite and has no diffraction peak of a nickel simple substance (namely, no obvious intermediate connecting layer).
The resulting electrode was subjected to the same anode current density change with time as in example 1, and the detection results are shown in Table 2.
Table 2: anode current density of the electrodes obtained in examples 1 to 4 and comparative examples 1 to 4 was varied with time
The small knot:
in each of examples 1 to 4, a first substitution reaction was carried out for a period of time to form an intermediate connection layer on the surface of the conductive substrate, and sufficient ions of the first metal were introduced into the reaction system, followed by a coprecipitation reaction to form a hydrotalcite compound layer on the surface of the intermediate connection layer. In comparative examples 1 to 4, the solutions all contained ions of the second metal and the precipitant at the same time, and co-precipitation was performed while the substitution reaction was performed, an intermediate connecting layer coating the conductive substrate was not formed, and ions of the first metal were introduced into the reaction system in a small amount, and the obtained hydrotalcite compound layer was small in thickness and had a limited active material content per unit area of the substrate material.
Examples 1 to 4 were compared with comparative examples 1 to 4, respectively, and it can be seen that the anode current density (mA/cm) at a potential of 1.6V vs RHE of the examples 2 ) Are all higher than the comparative example, and compared with the comparative example, the anodic current density (mA/cm) at a 1.6V vs RHE potential after 24 hours 2 ) The drop is low, and the intermediate connection layer plays a good role in protecting the conductive substrate.
Although embodiments of the present application have been described above, the present application is not limited to the specific embodiments and fields of application described above, which are merely illustrative, instructive, and not restrictive. Those skilled in the art, having the benefit of this disclosure, may make numerous forms of the invention without departing from the scope of the invention as claimed.

Claims (24)

1. An electrode, comprising:
a conductive substrate, an intermediate connection layer, and a hydrotalcite compound layer laminated in this order; wherein,
the conductive substrate includes a first metal;
the intermediate connection layer comprises a second metal;
the first metal is more reactive than the second metal;
the cations in the hydrotalcite compound layer include ions of a first metal and ions of a second metal.
2. The electrode according to claim 1, wherein,
the thickness of the intermediate connection layer is 0.01-10 μm, preferably 0.05-5 μm.
3. The electrode according to claim 1, wherein,
the hydrotalcite compound layer has a thickness of 0.1 to 20. Mu.m, preferably 0.5 to 10. Mu.m.
4. The electrode according to claim 1, wherein,
the first metal is selected from one or more than two of iron, cobalt and nickel;
the second metal is selected from one or more of cobalt, nickel, tin, lead, copper, mercury, silver, platinum and gold.
5. The electrode according to claim 1, wherein,
the cations in the hydrotalcite compound layer further include ions of a third metal;
the third metal is more reactive than the first metal.
6. The electrode according to claim 5, wherein,
the third metal is selected from one or more than two of potassium, barium, calcium, sodium, magnesium, aluminum, manganese, zinc, chromium, iron and cobalt.
7. A method of making an electrode comprising:
a displacement reaction step of placing a conductive substrate in a first solution under an inert atmosphere or a reducing atmosphere, wherein the conductive substrate comprises a first metal containing ions of a second metal, the first metal being more reactive than the second metal so that the ions of the first metal and the second metal undergo a displacement reaction, the ions of the second metal being displaced to form an intermediate connection layer on the surface of the conductive substrate, and obtaining a second solution containing the ions of the first metal and the ions of the second metal; the intermediate connection layer comprises a second metal;
and a coprecipitation reaction step, wherein a precipitant is introduced into the second solution to carry out a coprecipitation reaction, so as to form a hydrotalcite compound layer on the surface of the intermediate connecting layer, wherein cations in the hydrotalcite compound layer comprise ions of a first metal and ions of a second metal.
8. The electrode according to claim 7, wherein,
the thickness of the intermediate connection layer is 0.01-10 μm, preferably 0.05-5 μm.
9. The electrode according to claim 7, wherein,
the hydrotalcite compound layer has a thickness of 0.1 to 20. Mu.m, preferably 0.5 to 10. Mu.m.
10. The method of claim 7, wherein,
the inert atmosphere is kept by introducing inert gas into the reaction vessel before or during the displacement reaction.
11. The method of claim 7, wherein,
the reducing atmosphere is maintained by introducing a reducing gas and/or adding a reducing solid into the reaction vessel before or during the displacement reaction.
12. The method of claim 7, wherein,
the first metal is selected from one or more than two of iron, cobalt and nickel; and/or the number of the groups of groups,
the second metal is selected from one or more of cobalt, nickel, tin, lead, copper, mercury, silver, platinum and gold.
13. The method of claim 12, wherein,
the first metal is iron and the second metal is nickel.
14. The method of claim 7, wherein,
the concentration of the ions of the second metal in the first solution is 0.05 to 1mol/L, preferably 0.1 to 0.5mol/L.
15. The method of claim 7, wherein,
the reaction temperature of the displacement reaction is 20-60 ℃ and the reaction time is 1-60 min;
preferably, the reaction temperature is 35-50 ℃ and the reaction time is 5-30 min.
16. The method of claim 7, wherein,
the precipitant is one or more of organic alkali or inorganic alkali, preferably one or more of urea, thiourea, sodium bicarbonate, sodium carbonate, sodium lignin and sodium acetate; and/or the number of the groups of groups,
the molar content of the precipitant is 0.025-2 mol/L, preferably 0.05-1 mol/L.
17. The method of claim 7, wherein,
the introducing the precipitant comprises:
adding a precipitant to the second solution through a pipeline; and/or the number of the groups of groups,
the first solution is pre-filled with an encapsulant-encapsulated precipitant, and the light, heat or aqueous solution is capable of releasing the encapsulant to introduce the precipitant into the second solution.
18. The method of claim 7, wherein,
the reaction temperature of the coprecipitation reaction is 20-150 ℃;
preferably, the coprecipitation reaction is carried out under normal pressure, and the reaction temperature is 50-100 ℃; or the coprecipitation reaction is carried out under the sealed hydrothermal condition, and the reaction temperature is 100-130 ℃.
19. The method of claim 18, wherein,
the reaction time of the coprecipitation reaction is 2 to 48 hours, preferably 6 to 24 hours.
20. The method of claim 7, wherein,
before the displacement reaction step, a pretreatment step is also included,
the pretreatment step includes removing impurities from the conductive substrate.
21. The method of claim 20, wherein,
the impurity removal comprises one or more of acid washing, alkali washing, organic solvent washing and water washing.
22. The method of claim 7, wherein,
the first solution also contains ions of a third metal;
the third metal is more reactive than the first metal.
23. The method of claim 22, wherein,
the third metal is selected from one or more than two of potassium, barium, calcium, sodium, magnesium, aluminum, manganese, zinc, chromium, iron and cobalt.
24. Use of an electrode according to any one of claims 1 to 6 in electrochemistry.
CN202311101430.8A 2023-08-29 2023-08-29 Electrode and preparation method and application thereof Pending CN117317128A (en)

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