Double-shell hollow cylindrical nickel hydroxide electrode material for super capacitor and preparation method and application thereof
阅读说明：本技术 一种用于超级电容器的双壳空心柱状氢氧化镍电极材料及其制备方法和应用 (Double-shell hollow cylindrical nickel hydroxide electrode material for super capacitor and preparation method and application thereof ) 是由 黄子航 马天翼 孙放放 于 2020-11-20 设计创作，主要内容包括：本发明涉及一种用于超级电容器的双壳空心柱状氢氧化镍电极材料及其制备方法和应用,属于储能技术领域。本发明采用牺牲模板和电化学沉积技术相结合的策略在碳布基底上构筑了双壳空心柱状氢氧化镍,即通过晶体辅助水热的方法在碳布上生长氧化锌六棱柱,以硝酸镍为电解液在氧化锌表面电沉积一层氢氧化镍,然后继续使用电沉积的方式在材料表面轮流包覆氧化锌和氢氧化镍层,再通过浓碱刻蚀氧化锌形成双壳空心柱状氢氧化镍,并且壳层的氢氧化镍为相互连接的超薄纳米片,此种结构增加了材料的比表面积,有利于电极和电解液的接触,最大化增加材料的利用率,同时此种结构的制备方法也为构筑其他双壳空心材料提供了一种思路。(The invention relates to a double-shell hollow columnar nickel hydroxide electrode material for a super capacitor, and a preparation method and application thereof, and belongs to the technical field of energy storage. The invention adopts a strategy of combining a sacrificial template and an electrochemical deposition technology to construct double-shell hollow columnar nickel hydroxide on a carbon cloth substrate, namely, a zinc oxide hexagonal prism grows on the carbon cloth by a crystal-assisted hydrothermal method, nickel nitrate is used as electrolyte to electrodeposit a layer of nickel hydroxide on the surface of the zinc oxide, then the zinc oxide and a nickel hydroxide layer are coated on the surface of the material in turn by continuously using an electrodeposition mode, the zinc oxide is etched by concentrated alkali to form the double-shell hollow columnar nickel hydroxide, and the nickel hydroxide of the shell layer is ultrathin nanosheets which are mutually connected.)
1. A preparation method of a double-shell hollow columnar nickel hydroxide electrode material for a super capacitor is characterized by comprising the following steps:
1) template construction: dissolving zinc nitrate and hexamethylenetetramine in deionized water, adding ammonia water, stirring to form a precursor solution, immersing a carbon cloth with ZnO seed crystals in the precursor solution, carrying out hydrothermal treatment, and growing a columnar zinc oxide template on the carbon cloth to form CC @ ZnO;
2) active material deposition: CC @ ZnO is used as a working electrodeElectrodeposition is carried out by taking nickel nitrate aqueous solution as electrolyte and electrodepositing a layer of nickel hydroxide on the surface of the zinc oxide to form CC @ ZnO @ Ni (OH)2；
3) And (3) template deposition: with CC @ ZnO @ Ni (OH)2Taking zinc nitrate aqueous solution as electrolyte for electrodeposition, and electrodepositing a layer of zinc oxide template on the surface of nickel hydroxide to form CC @ ZnO @ Ni (OH)2@ZnO；
4) Secondary deposition of active substances: with CC @ ZnO @ Ni (OH)2Adopting @ ZnO as a working electrode, adopting nickel nitrate aqueous solution as electrolyte, carrying out electrodeposition, and electrodepositing a layer of nickel hydroxide on the surface of the zinc oxide again to form CC @ ZnO @ Ni (OH)2@[email protected](OH)2；
5) And (3) template etching: the CC @ ZnO @ Ni (OH) prepared in the step 4)2@[email protected](OH)2Soaking in 6M alkali solution for 24h, etching away the zinc oxide template, taking out, cleaning with ethanol and deionized water, and drying in a vacuum drying oven at 60 ℃ for 12h to form the double-shell hollow cylindrical nickel hydroxide electrode material.
2. The preparation method according to claim 1, wherein in the step 1), the preparation method of the carbon cloth with the ZnO seed crystal comprises the following steps: soaking the cleaned carbon cloth in zinc nitrate alcohol solution for 10min, taking out, heating on a hot table at 320 deg.C for 10min, and repeating soaking and heating for 1-4 times.
3. The method according to claim 2, wherein the alcohol is methanol or ethanol.
4. The preparation method according to claim 1, wherein in step 1), the hydrothermal treatment conditions are: hydrothermal treatment at 95 ℃ for 5 h.
5. The production method according to claim 1, wherein in step 2), the electrodeposition conditions are: the deposition was carried out at-1V for 50-200 seconds.
6. The production method according to claim 1, wherein in step 3), the electrodeposition conditions are: the deposition was carried out at-1V for 50 seconds.
7. The production method according to claim 1, wherein in step 4), the electrodeposition conditions are: the deposition was carried out at-1V for 50-200 seconds.
8. The method according to claim 1, wherein in the step 5), the alkali solution is a sodium hydroxide or potassium hydroxide solution.
9. Use of the double-shell hollow cylindrical nickel hydroxide electrode material prepared by the method according to any one of claims 1 to 8 in a supercapacitor.
10. The use according to claim 9, characterized by the use of a double-shell hollow cylindrical nickel hydroxide electrode material as a positive electrode material in a supercapacitor.
Technical Field
The invention belongs to the technical field of new energy, and particularly relates to a double-shell hollow columnar nickel hydroxide electrode material for a super capacitor, and a preparation method and application thereof.
Background
With the rapid development of the technological revolution and the gradual exhaustion of the non-renewable fossil fuel, energy has become a big problem blocking the sustainable development of the human society, so that the development of efficient transfer and storage technology of various new energy and clean energy has become a hotspot of current international research, and batteries and super capacitors are favored by researchers as efficient energy conversion and storage devices. The super capacitor has the advantages of high power density, high charging and discharging speed, long service life, environmental friendliness and the like, and is widely applied to the fields of smart power grids, hybrid vehicles, portable electronic equipment and the like.
Supercapacitors are classified into double layer capacitors and pseudo-capacitor capacitors according to the mechanism of charge storage, and the quality of the capacitor properties depends largely on the electrode material. The oxidation/hydroxide theoretical capacitance of the transition metal nickel is high, and the nickel is considered to be a very promising electrode material, however, poor conductivity is a common problem of the transition metal material, and meanwhile, the massive electrode material can block the infiltration of electrolyte, so that the utilization rate of the material is not high, and therefore, the electrochemical performance of the nickel-based material is very necessary to be improved by reasonably constructing the microscopic nano structure of the material.
Disclosure of Invention
The invention constructs double-shell hollow columnar nickel hydroxide on the carbon cloth by a template etching method, increases the specific surface area and ion permeability of the nickel hydroxide electrode material, and achieves the purpose of improving the energy storage performance of the electrode material.
The technical scheme adopted by the invention is as follows: a preparation method of a double-shell hollow columnar nickel hydroxide electrode material for a super capacitor comprises the following steps:
1) template construction: dissolving zinc nitrate and hexamethylenetetramine in deionized water, adding ammonia water, stirring to obtain a precursor solution, immersing a carbon cloth with ZnO seed crystals in the precursor solution, carrying out hydrothermal treatment, and growing a columnar zinc oxide template on the carbon cloth to form CC @ ZnO;
2) active material deposition: using CC @ ZnO as a working electrode, using a nickel nitrate aqueous solution as an electrolyte, carrying out electrodeposition, and electrodepositing a layer of nickel hydroxide on the surface of zinc oxide to form CC @ ZnO @ Ni (OH)2；
3) And (3) template deposition: with CC @ ZnO @ Ni (OH)2Taking zinc nitrate aqueous solution as electrolyte for electrodeposition, and electrodepositing a layer of zinc oxide template on the surface of nickel hydroxide to form CC @ ZnO @ Ni (OH)2@ZnO；
4) Secondary deposition of active substances: with CC @ ZnO @ Ni (OH)2Adopting @ ZnO as a working electrode, adopting nickel nitrate aqueous solution as electrolyte, carrying out electrodeposition, and electrodepositing a layer of nickel hydroxide on the surface of the zinc oxide again to form CC @ ZnO @ Ni (OH)2@[email protected](OH)2；
5) And (3) template etching: the CC @ ZnO @ Ni (OH) prepared in the step 4)2@[email protected](OH)2Soaking in 6M alkali solution for 24h, etching away the zinc oxide template, taking out, cleaning with ethanol and deionized water, and drying in a vacuum drying oven at 60 ℃ for 12h to form the double-shell hollow cylindrical nickel hydroxide electrode material.
Further, in the above preparation method, in step 1), the preparation method of the carbon cloth with ZnO seed crystals comprises: soaking the cleaned carbon cloth in zinc nitrate alcohol solution for 10min, taking out, heating on a hot table at 320 deg.C for 10min, and repeating the soaking and heating steps for 1-4 times.
Further, in the above preparation method, the alcohol is methanol or ethanol.
Further, in the above preparation method, in step 1), the hydrothermal treatment conditions are: hydrothermal treatment at 95 ℃ for 5 h.
Further, in the above preparation method, in step 2), the electrodeposition conditions are as follows: the deposition was carried out at-1V for 50-200 seconds.
Further, in the above preparation method, in step 3), the electrodeposition conditions are as follows: the deposition was carried out at-1V for 50 seconds.
Further, in the above preparation method, in step 4), the electrodeposition conditions are as follows: the deposition was carried out at-1V for 50-200 seconds.
Further, in the above preparation method, step 5), the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution.
The invention provides an application of a double-shell hollow columnar nickel hydroxide electrode material in a super capacitor.
Further, the double-shell hollow cylindrical nickel hydroxide electrode material is applied to a super capacitor as a positive electrode material.
The invention has the beneficial effects that:
1. the invention adopts a strategy of combining a sacrificial template and an electrochemical deposition technology, adopts a continuous casting mode of template construction, active material deposition, template deposition, active material secondary deposition and template etching, takes ZnO which is easy to corrode in alkaline solution as a basis for manufacturing a hollow structure, and constructs double-shell hollow columnar nickel hydroxide on a carbon cloth substrate to prepare the double-shell hollow columnar nickel hydroxide electrode material. Namely, a zinc oxide hexagonal prism grows on carbon cloth by a crystal-assisted hydrothermal method, nickel nitrate is used as electrolyte to electrodeposit a layer of nickel hydroxide on the surface of zinc oxide, then zinc oxide and a nickel hydroxide layer are coated on the surface of the material in turn by using an electrodeposition mode, zinc oxide is etched by concentrated alkali to form double-shell hollow columnar nickel hydroxide, and the nickel hydroxide of the shell layer is an ultrathin nanosheet which is mutually connected, so that the specific surface area of the material is increased, the contact between an electrode and the electrolyte is facilitated, and the utilization rate of the material is maximized.
2. According to the invention, nickel hydroxide is uniformly distributed and grows on the carbon cloth fiber in a columnar form, the direct space distributed among the active substances is favorable for rapid diffusion of electrolyte, the internal hollow structure can store the electrolyte, increase the specific surface area of the material and buffer the strain in the energy storage process, and compared with the single-shell hollow structure, the double-shell hollow structure has the advantages of the single-shell hollow structure, larger specific surface area and more exposed active sites, and shows better electrochemical performance.
Drawings
FIG. 1 is a scanning electron micrograph (a) and (b) of active material deposited in step (3) of example 1.
FIG. 2 is a scanning electron micrograph (a) and (b) showing a low magnification (a) and a high magnification (b) after deposition of an active material in step (3) of example 2.
FIG. 3 is a scanning electron micrograph (a) of the active material deposited at the step (3) of example 3 and (b) of the active material deposited at a low magnification.
Fig. 4 is a scanning electron micrograph (a) and (b) of the active material deposited in step (3) of example 4.
FIG. 5 is the XRD spectrum of the zinc oxide template and the double-shell hollow nickel hydroxide material prepared in example 4.
FIG. 6 is a transmission electron microscope picture of the double-shell hollow nickel hydroxide material prepared in example 4.
FIG. 7 is a cyclic voltammogram of the double-shelled, hollow nickel hydroxide electrode prepared in example 5 at different sweep rates.
Fig. 8 is a charge-discharge curve of the double-shelled hollow nickel hydroxide electrode prepared in example 5 at different current densities.
FIG. 9 is a graph of rate performance of the double-shelled, hollow nickel hydroxide electrode prepared in example 5.
Detailed Description
A preparation method of a double-shell hollow columnar nickel hydroxide electrode material for a super capacitor comprises the following steps:
1) template construction: dissolving zinc nitrate and hexamethylenetetramine in deionized water, adding ammonia water, stirring to form a precursor solution, immersing a carbon cloth with ZnO seed crystals in the precursor solution, carrying out hydrothermal treatment at 95 ℃ for 5 hours, and growing a columnar zinc oxide template on the carbon cloth to form CC @ ZnO.
The preparation method of the carbon cloth with the ZnO seed crystal comprises the following steps: soaking the cleaned carbon cloth in zinc nitrate alcohol solution for 10min, taking out, heating on a hot table at 320 deg.C for 10min, and repeating soaking and heating for 1-4 times. The alcohol is methanol or ethanol.
2) Active material deposition: using CC @ ZnO as a working electrode, using a nickel nitrate aqueous solution as an electrolyte, depositing for 50-200 seconds under the voltage of-1V, and electrodepositing a layer of nickel hydroxide on the surface of zinc oxide to form CC @ ZnO @ Ni (OH)2；
3) And (3) template deposition: with CC @ ZnO @ Ni (OH)2Using zinc nitrate aqueous solution as electrolyte for deposition for 50 seconds under-1V voltage as a working electrode, and electrodepositing a layer of zinc oxide template on the surface of nickel hydroxide to form CC @ ZnO @ Ni (OH)2@ZnO；
4) Secondary deposition of active substances: with CC @ ZnO @ Ni (OH)2@ ZnO is a working electrode, nickel nitrate aqueous solution is electrolyte, the deposition is carried out for 50-200 seconds under the voltage of-1V, a layer of nickel hydroxide is electrodeposited on the surface of the zinc oxide again, and CC @ ZnO @ Ni (OH) is formed2@[email protected](OH)2；
5) And (3) template etching: the CC @ ZnO @ Ni (OH) prepared in the step 4)2@[email protected](OH)2Soaking in 6M alkali solution for 24h, etching away the zinc oxide template, taking out, cleaning with ethanol and deionized water, and drying in a vacuum drying oven at 60 ℃ for 12h to form the double-shell hollow cylindrical nickel hydroxide electrode material.
The alkali solution is sodium hydroxide or potassium hydroxide solution.
Example 1
A preparation method of a double-shell hollow columnar nickel hydroxide electrode material for a super capacitor comprises the following steps:
(1) preparation of carbon cloth with ZnO seed crystal: cutting carbon cloth into 2 × 3cm2According to specifications, after ultrasonic cleaning is respectively carried out on ethanol and deionized water, the carbon cloth is soaked in 0.05M of zinc nitrate ethanol solution for 10min, then the carbon cloth is placed on a hot table at 320 ℃ for baking for 10min, and the soaking and baking are repeated for 4 times, so that the carbon cloth with the zinc oxide seed crystal is obtained.
(2) Template construction: 1.49g of zinc nitrate and 0.7g of hexamethylenetetramine are weighed and dissolved in 30ml of deionized water, 2ml of ammonia water is added, and the mixture is stirred to form a transparent bright yellow solution, so that a precursor solution is obtained. Transferring the precursor solution into a 40ml reaction kettle, immersing the prepared carbon cloth with the zinc oxide seed crystal in the precursor solution, carrying out hydrothermal treatment for 5h at 95 ℃, and growing a hexagonal prism-shaped zinc oxide template on the carbon cloth to form CC @ ZnO.
(3) Active material deposition: 0.44g of nickel nitrate was weighed out and dissolved in 20ml of deionized water to form a green solution as an electrolyte. Depositing the CC @ ZnO obtained in the step (2) as a working electrode, carbon paper as a counter electrode and a calomel electrode as a reference electrode for 200 seconds under the voltage of-1V, electrodepositing a layer of nickel hydroxide on the surface of zinc oxide, and then washing the nickel hydroxide clean by deionized water to form CC @ ZnO @ Ni (OH)2。
(4) And (3) template deposition: 0.45g of zinc nitrate was weighed out and dissolved in 20ml of deionized water to obtain a solution as an electrolyte. Using CC @ ZnO @ Ni (OH) obtained in step (3)2Depositing for 50 seconds under-1V voltage as a working electrode, carbon paper as a counter electrode and a calomel electrode as a reference electrode, electrodepositing a zinc oxide template on the surface of nickel hydroxide, and washing with deionized water to form CC @ ZnO @ Ni (OH)2@ZnO。
(5) Secondary deposition of active substances: 0.44g of nickel nitrate was weighed out and dissolved in 20ml of deionized water to form a green solution as an electrolyte. The CC @ ZnO @ Ni (OH) obtained in the step (4)2@ ZnO is a working electrode, carbon paper is a counter electrode, a calomel electrode is a reference electrode, the deposition is carried out for 200 seconds under the voltage of-1V, a layer of nickel hydroxide is electrodeposited on the surface of zinc oxide again, and then the zinc oxide is washed clean by deionized water to form CC @ ZnO @ Ni (OH)2@[email protected](OH)2。
(6) And (3) template etching: the CC @ ZnO @ Ni (OH) prepared in the step (5)2@[email protected](OH)2Soaking in 6M KOH solution for 24h, etching away the zinc oxide template, taking out, washing with ethanol and deionized water for several times, and drying in a vacuum drying oven at 60 ℃ for 12h to obtain the double-shell hollow cylindrical nickel hydroxide electrode material.
FIG. 1 is a scanning electron micrograph (a) showing a low magnification (b) and a high magnification (a) showing the active material deposited in step (3) of example 1. As can be seen from fig. 1, when the electrodeposition time of nickel hydroxide is 200 seconds, the nickel hydroxide material deposited on the surface of the hexagonal zinc oxide is thicker and serious agglomeration occurs (b in the figure), and the zinc oxide nanorod template is completely covered, and if template deposition and active material secondary deposition are further performed, a thicker nickel hydroxide shell is generated, which is not beneficial to the diffusion and transmission of electrolyte ions, so that the electrodeposition time of nickel hydroxide should be properly adjusted to reduce the thickness of the double-layer nickel hydroxide shell.
Example 2
A preparation method of a double-shell hollow columnar nickel hydroxide electrode material for a super capacitor comprises the following steps:
(1) preparation of carbon cloth with ZnO seed crystal: cutting carbon cloth into 2 × 3cm2According to specifications, ultrasonic cleaning is respectively carried out by ethanol and deionized water, the carbon cloth is soaked in 0.05M of zinc nitrate ethanol solution for 10min, then the carbon cloth is placed on a hot table at 320 ℃ for baking for 10min, and the soaking and baking are repeated for 4 times, so that the carbon cloth with the zinc oxide seed crystal is obtained.
(2) Template construction: 1.49g of zinc nitrate and 0.7g of hexamethylenetetramine are weighed and dissolved in 30ml of deionized water, 2ml of ammonia water is added, and the mixture is stirred to form a transparent bright yellow solution, so that a precursor solution is obtained. Transferring the precursor solution into a 40ml reaction kettle, immersing the prepared carbon cloth with the zinc oxide seed crystal in the precursor solution, carrying out hydrothermal treatment for 5h at 95 ℃, and growing a hexagonal prism-shaped zinc oxide template on the carbon cloth to form CC @ ZnO.
(3) Active material deposition: weighing 0.44g of nickel nitrate, dissolving the nickel nitrate in 20ml of deionized water to form a green solution serving as an electrolyte, taking CC @ ZnO obtained in the step (2) as a working electrode, carbon paper as a counter electrode and a calomel electrode as a reference electrode, depositing for 150 seconds at a voltage of-1V, electrodepositing a layer of nickel hydroxide on the surface of zinc oxide, and then washing the nickel hydroxide cleanly with deionized water to form CC @ ZnO @ Ni (OH)2。
(4) And (3) template deposition: 0.45g of zinc nitrate was weighed out and dissolved in 20ml of deionized water to obtain a solution as an electrolyte. Using CC @ ZnO @ Ni (OH) obtained in step (3)2Is a working electrode, carbon paper is a counter electrode, a calomel electrode is a reference electrode, the deposition is carried out for 50 seconds under the voltage of-1V, a layer of zinc oxide template is electrodeposited on the surface of the nickel hydroxide, and the zinc oxide template is washed clean by deionized water to form [email protected]@Ni(OH)2@ZnO。
(5) Secondary deposition of active substances: 0.44g of nickel nitrate was weighed and dissolved in 20ml of deionized water to form a green solution as an electrolyte, and CC @ ZnO @ Ni (OH) obtained in step (4)2@ ZnO as a working electrode, carbon paper as a counter electrode, a calomel electrode as a reference electrode, depositing for 150 seconds under the voltage of-1V, electrodepositing a layer of nickel hydroxide on the surface of zinc oxide, and then washing with deionized water to form CC @ ZnO @ Ni (OH)2@[email protected](OH)2。
(6) And (3) template etching: the CC @ ZnO @ Ni (OH) prepared in the step (5)2@[email protected](OH)2Soaking in 6M KOH solution for 24h, etching away the zinc oxide template, taking out, washing with ethanol and deionized water for several times, and drying in a vacuum drying oven at 60 ℃ for 12h to obtain the double-shell hollow cylindrical nickel hydroxide electrode material.
FIG. 2 is a scanning electron micrograph (a) showing a low magnification (b) and a high magnification (a) showing the active material deposited in step (3) of example 2. As can be seen, when the electrodeposition time of nickel hydroxide is 150 seconds, the agglomeration phenomenon is improved, but the nickel hydroxide layer on the surface of the zinc oxide nanorods is still thick and the zinc oxide nanorods are completely covered, so the electrodeposition time should be further adjusted to reduce the thickness of the nickel hydroxide shell.
Example 3
A preparation method of a double-shell hollow columnar nickel hydroxide electrode material for a super capacitor comprises the following steps:
(1) preparation of carbon cloth with ZnO seed crystal: cutting carbon cloth into 2 × 3cm2According to specifications, after ultrasonic cleaning is respectively carried out on ethanol and deionized water, the carbon cloth is soaked in 0.05M of zinc nitrate ethanol solution for 10min, then the carbon cloth is placed on a hot table at 320 ℃ for baking for 10min, and the soaking and baking are repeated for 4 times, so that the carbon cloth with the zinc oxide seed crystal is obtained.
(2) Template construction: 1.49g of zinc nitrate and 0.7g of hexamethylenetetramine are weighed and dissolved in 30ml of deionized water, 2ml of ammonia water is added, and the mixture is stirred to form a transparent bright yellow solution, so that a precursor solution is obtained. Transferring the precursor solution into a 40ml reaction kettle, immersing the prepared carbon cloth with the zinc oxide seed crystal in the precursor solution, carrying out hydrothermal treatment for 5h at 95 ℃, and growing a hexagonal prism-shaped zinc oxide template on the carbon cloth to form CC @ ZnO.
(3) Active material deposition: 0.44g of nickel nitrate was weighed out and dissolved in 20ml of deionized water to form a green solution as an electrolyte. Depositing the CC @ ZnO obtained in the step (2) as a working electrode, carbon paper as a counter electrode and a calomel electrode as a reference electrode for 100 seconds at a voltage of-1V, electrodepositing a layer of nickel hydroxide on the surface of the zinc oxide, and then washing the nickel hydroxide clean by deionized water to form CC @ ZnO @ Ni (OH)2。
(4) And (3) template deposition: 0.45g of zinc nitrate was weighed out and dissolved in 20ml of deionized water to obtain a solution as an electrolyte. Using CC @ ZnO @ Ni (OH) obtained in step (3)2Depositing for 50 seconds under-1V voltage as a working electrode, carbon paper as a counter electrode and a calomel electrode as a reference electrode, electrodepositing a zinc oxide template on the surface of nickel hydroxide, and washing with deionized water to form CC @ ZnO @ Ni (OH)2@ZnO。
(5) Secondary deposition of active substances: 0.44g of nickel nitrate was weighed out and dissolved in 20ml of deionized water to form a green solution as an electrolyte. The CC @ ZnO @ Ni (OH) obtained in the step (4)2@ ZnO is a working electrode, carbon paper is a counter electrode, a calomel electrode is a reference electrode, the deposition is carried out for 100 seconds under the voltage of-1V, a layer of nickel hydroxide is electrodeposited on the surface of zinc oxide again, and then the zinc oxide is washed clean by deionized water to form CC @ ZnO @ Ni (OH)2@[email protected](OH)2。
(6) And (3) template etching: the CC @ ZnO @ Ni (OH) prepared in the step (5)2@[email protected](OH)2Soaking in 6M KOH solution for 24h, etching away the zinc oxide template, taking out, washing with ethanol and deionized water for several times, and drying in a vacuum drying oven at 60 ℃ for 12h to obtain the double-shell hollow cylindrical nickel hydroxide electrode material.
Fig. 3 is a scanning electron microscope image of the low multiple (a in the figure) and the high multiple (b in the figure) after the deposition of the active material in step (3) in example 3, and it can be seen from the figure that when the electrodeposition time in step (3) is reduced to 100 seconds, no agglomeration occurs, and the nickel hydroxide material is wrapped on the surface of the zinc oxide nanorod, but the thickness of the nanorod is not uniform, so that the electrodeposition time should be further reduced, and the nickel hydroxide shell is uniformly wrapped on the surface of the zinc oxide nanorod to form a thin and uniform double-layer nickel hydroxide shell structure.
Example 4
A preparation method of a double-shell hollow columnar nickel hydroxide electrode material for a super capacitor comprises the following steps:
(1) preparation of carbon cloth with ZnO seed crystal: cutting carbon cloth into 2 × 3cm2According to specifications, after ultrasonic cleaning is respectively carried out on ethanol and deionized water, the carbon cloth is soaked in 0.05M of zinc nitrate ethanol solution for 10min, then the carbon cloth is placed on a hot table at 320 ℃ for baking for 10min, and the soaking and baking are repeated for 4 times, so that the carbon cloth with the zinc oxide seed crystal is obtained.
(2) Template construction: 1.49g of zinc nitrate and 0.7g of hexamethylenetetramine are weighed and dissolved in 30ml of deionized water, 2ml of ammonia water is added, and the mixture is stirred to form a transparent bright yellow solution, so that a precursor solution is obtained. Transferring the precursor solution into a 40ml reaction kettle, immersing the prepared carbon cloth with the zinc oxide seed crystal in the precursor solution, carrying out hydrothermal treatment for 5h at 95 ℃, and growing a hexagonal prism-shaped zinc oxide template on the carbon cloth to form CC @ ZnO.
(3) Active material deposition: 0.44g of nickel nitrate was weighed out and dissolved in 20ml of deionized water to form a green solution as an electrolyte. Depositing the CC @ ZnO obtained in the step (2) as a working electrode, carbon paper as a counter electrode and a calomel electrode as a reference electrode for 50 seconds under the voltage of-1V, electrodepositing a layer of nickel hydroxide on the surface of zinc oxide, and then washing the nickel hydroxide clean by deionized water to form CC @ ZnO @ Ni (OH)2And (3) cleaning.
(4) And (3) template deposition: 0.45g of zinc nitrate was weighed out and dissolved in 20ml of deionized water to obtain a solution as an electrolyte. Using CC @ ZnO @ Ni (OH) obtained in step (3)2Depositing for 50 seconds under-1V voltage as a working electrode, carbon paper as a counter electrode and a calomel electrode as a reference electrode, electrodepositing a zinc oxide template on the surface of nickel hydroxide, and washing with deionized water to form CC @ ZnO @ Ni (OH)2@ZnO。
(5) Secondary deposition of active substances: 0.44g of nickel nitrate was weighed out and dissolved in 20ml of deionized water to form a green solution as an electrolyte. The CC @ ZnO @ Ni (OH) obtained in the step (4)2@ ZnO is a working electrode, carbon paper is a counter electrode, a calomel electrode is a reference electrode, the deposition is carried out for 50 seconds under the voltage of-1V, a layer of nickel hydroxide is electrodeposited on the surface of zinc oxide again, and then the zinc oxide is washed clean by deionized water to form CC @ ZnO @ Ni (OH)2@[email protected](OH)2。
(6) And (3) template etching: the CC @ ZnO @ Ni (OH) prepared in the step (5)2@[email protected](OH)2Soaking in 6M KOH solution for 24h, etching away the zinc oxide template, taking out, washing with ethanol and deionized water for several times, and drying in a vacuum drying oven at 60 ℃ for 12h to obtain the double-shell hollow cylindrical nickel hydroxide electrode material.
Fig. 4 is scanning electron microscope pictures of low multiple (a in the figure) and high multiple (b in the figure) after the deposition of the active material in the step (3) in the example 4, and it can be seen from the figure that when the electrodeposition time is reduced to 50 seconds, nickel hydroxide is uniformly coated on the surface of the zinc oxide nanorod to form a neat nanorod structure, and as can be seen from the scanning electron microscope picture of high multiple b in fig. 4, the coated nickel hydroxide material is thin and uniform, which is beneficial to the diffusion and transmission of electrolyte ions and improves the utilization rate of the electrode material. It is thus shown that a thin, uniform shell of nickel hydroxide can be produced when the nickel hydroxide electrodeposition time is 50 seconds, and this example method is a preferred embodiment of the present invention.
Fig. 5 is XRD spectra of the zinc oxide template (a in fig. 5) prepared in example 4 and the double-shelled hollow nickel hydroxide material (b in fig. 5), and it can be seen from a in fig. 5 that the position of diffraction peak of the prepared zinc oxide template is consistent with JCPDS card 36-1451 (ZnO). As can be seen from b in FIG. 5, the diffraction peak position of the prepared double-shell hollow nickel hydroxide material is consistent with JCPDS card 14-0117(Ni (OH)2) In addition, the XRD spectrum of the double-shell hollow nickel hydroxide material does not have a characteristic peak of zinc oxide, which indicates that the zinc oxide template is completely etched to form the double-shell hollow structure.
Fig. 6 is a transmission electron microscope picture of the double-shell hollow nickel hydroxide material prepared in example 4, and it can be seen from the picture that the zinc oxide template deposited twice is completely etched away, so as to form a double-shell hollow structure of nickel hydroxide. Thus, it is shown that when the two-time nickel hydroxide electrodeposition time is 50 seconds, a thin and uniform double-shell hollow nickel hydroxide material can be prepared.
Example 5
Application of double-shell hollow cylindrical nickel hydroxide electrode material as positive electrode material in super capacitor
The method comprises the following steps: the method comprises the steps of taking a double-shell hollow cylindrical nickel hydroxide electrode material as a working electrode, a mercury oxide electrode as a reference electrode, carbon fiber cloth as a counter electrode and 1M KOH as electrolyte, and respectively carrying out cyclic voltammetry scanning test and constant current charge-discharge test on the double-shell hollow cylindrical nickel hydroxide electrode within the potential ranges of 0-0.75V and 0-0.55V.
FIG. 7 is a cyclic voltammetry curve of the double-shell hollow cylindrical nickel hydroxide electrode of example 5 at different sweep rates, and it can be seen from the graph that a pair of reversible redox peaks appear in the potential range of 0-0.75V, indicating that the electrode material has good energy storage behavior.
FIG. 8 and FIG. 9 are the constant current charge-discharge curve and the rate performance curve, respectively, of the double-shell hollow cylindrical nickel hydroxide electrode of example 5, from which it can be seen that when the current density is 3mA cm-2When the capacitance is in the range of 1838mF cm-2And the capacitor has excellent capacitance performance. When the current density is increased by 10 times to 30mA cm-2When the specific capacitance is 1644mF cm-2The specific capacitance maintenance rate is as high as 89.4%, and excellent rate performance is shown, which indicates that the prepared double-shell hollow structure is beneficial to the diffusion and transmission of electrolyte ions in the nickel hydroxide material, and the utilization rate of the electrode material is improved, so that the excellent specific capacitance and rate performance are shown.