CN113539702A - Preparation method of PNTs @ NiMoS core-shell structure composite electrode material and application of PNTs @ NiMoS core-shell structure composite electrode material in water system asymmetric supercapacitor - Google Patents
Preparation method of PNTs @ NiMoS core-shell structure composite electrode material and application of PNTs @ NiMoS core-shell structure composite electrode material in water system asymmetric supercapacitor Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Abstract
The invention discloses a preparation method of a PNTs @ NiMoS core-shell structure composite electrode material and application of the PNTs @ NiMoS core-shell structure composite electrode material in a water system asymmetric supercapacitor, and belongs to the technical field of electrochemical energy storage. According to the preparation method, the PNTs is used as a core, the NiMoS nano sheet with high specific capacitance grows on the surface of the core in situ by a hydrothermal method, and the synergistic effect of the PNTs and the NiMoS nano sheet is utilized to prepare the PNTs @ NiMoS core-shell structure composite material with high specific capacitance and good cycle stability, wherein the NiMoS nano sheet is used as a shell to provide high specific capacitance, the PNTs is used as a core to facilitate the rapid transmission of electrons/ions, the utilization rate of an active material is improved, and the electrochemical performance of the optimized composite material is obviously superior to that of the PNTs and the NiMoS. In addition, water-based asymmetric supercapacitors assembled with N-CNTs exhibit high energy and power densities and good cycling stability.
Description
Technical Field
The invention relates to a preparation method of a PNTs @ NiMoS core-shell structure composite electrode material and application of the PNTs @ NiMoS core-shell structure composite electrode material in a water system asymmetric supercapacitor, and belongs to the technical field of electrochemical energy storage.
Background
The gradual depletion of fossil fuels and the increasingly severe environmental pollution problems caused by the combustion thereof have prompted researchers to develop and utilize renewable clean energy sources, such as solar energy, wind energy, tidal energy, and the like. However, due to the intermittent and fluctuating nature of these clean energy sources, the full utilization of these clean energy sources has led to the development of high performance, sustainable, environmentally friendly energy storage and conversion devices. The super capacitor has the characteristics of high power density, excellent cycle life, environmental friendliness and the like, so that the super capacitor is widely researched and applied in the field of energy storage. How to increase the energy density of the super capacitor without losing the high power density is a difficult problem to be overcome. Wherein the development of electrode materials with high specific capacitance and excellent cycling stability is crucial for achieving high energy-power output performance of supercapacitors.
The transition metal compound has a higher theoretical specific capacitance due to multiple valence states of its metal ion. Compared with transition metal oxides, the transition metal sulfide has higher conductivity and shows better electrochemical performance. Particularly, the double transition metal sulfide can provide more abundant redox reaction sites through the synergistic action among different metal ions, and further store more charges. Among various transition metal sulfides, nickel sulfide has been widely studied because of its advantages such as high specific capacitance, redox reversibility, safety, and low cost; molybdenum disulfide as another attractive electrode material has a graphite-like layered structure, and the Mo atoms have multiple redox states from +2 to +6, which impart a specific nanostructure and good pseudocapacitive capability to molybdenum disulfide. Therefore, the bimetallic nickel molybdenum sulfide with the nano structure can show obviously improved specific capacitance performance. However, the electronic conductivity of bimetallic nickel molybdenum sulfide is still not ideal enough, which largely hinders its further application in supercapacitors with high energy-power output performance.
Polypyrrole is used as a pseudo-capacitor material, and has the advantages of high conductivity, low cost, good flexibility, no toxicity, convenience in synthesis and the like. Particularly, Polypyrrole Nanotubes (PNTs) with hollow tubular structures are used for the conductive framework of the composite material, which is beneficial to electron/ion transmission, prevents the aggregation of active materials and improves the utilization rate of the active materials. Therefore, the nickel molybdenum sulfide (NiMoS) is synthesized in situ on the outer surface of the PNTs to prepare the PNTs @ NiMoS core-shell structure composite electrode material, and the composite electrode material has high specific capacitance and good circulation stability and is assembled into a water system asymmetric supercapacitor with high energy density, power density and good circulation stability by utilizing the synergistic effect of the nickel molybdenum sulfide (NiMoS) and the PNTs, so that the water system asymmetric supercapacitor is applied to the technical field of electrochemical energy storage.
Disclosure of Invention
The invention aims to provide a preparation method of a PNTs @ NiMoS core-shell structure composite electrode material.
The invention also aims to provide application of the PNTs @ NiMoS core-shell structure composite electrode material in the field of water system asymmetric supercapacitors.
The technical scheme of the invention is as follows:
a preparation method of a PNTs @ NiMoS core-shell structure composite electrode material comprises the following steps:
and 2, preparing the PNTs @ NiMoS core-shell structure composite electrode material by using the PNTs, the sodium molybdate dihydrate, the nickel nitrate hexahydrate, the thiourea and the triethylamine which are obtained in the step 1 as raw materials.
Further limiting, the specific operation process of step 1 is as follows:
dissolving methyl orange and ferric trichloride hexahydrate in distilled water respectively to form a solution A and a solution B, then dropwise adding the solution B into the solution A to obtain a suspension, dropwise adding a pyrrole monomer into the suspension, stirring and reacting for 12 hours under the condition of an ice-water bath at 5 ℃, filtering, washing with distilled water and absolute ethyl alcohol for several times until a filtrate becomes colorless, and then placing an obtained black product in a vacuum drying oven at 60 ℃ for vacuum drying for 12 hours to obtain PNTs.
Further, the molar concentration ratio of methyl orange, pyrrole monomer and ferric chloride hexahydrate in the reaction solution is 0.001mol/L:0.02mol/L:0.06 mol/L.
Further limiting, the specific operation process of step 2 is:
ultrasonically dispersing the PNTs obtained in the step 1 in an ethylene glycol aqueous solution, then adding sodium molybdate dihydrate, nickel nitrate hexahydrate and thiourea, carrying out ultrasonic treatment for 15min, dropwise adding triethylamine, continuing ultrasonic treatment for 10min, then transferring the suspension into a hydrothermal reaction kettle, reacting for 6h at 150 ℃, naturally cooling to room temperature, filtering, washing with distilled water and absolute ethyl alcohol for several times, and then placing in a vacuum drying oven at 60 ℃ for vacuum drying for 12h to obtain the PNTs @ NiMoS core-shell structure composite electrode material.
More specifically, the volume ratio of ethylene glycol to distilled water in the ethylene glycol aqueous solution is 15mL:15 mL.
More specifically, the mass molar ratio of PNTs, sodium molybdate dihydrate, nickel nitrate hexahydrate and thiourea is (10-40) mg:0.75mmol:0.75mmol:4 mmol.
More specifically, the volume of triethylamine is 1 mL.
The method for preparing the water system asymmetric supercapacitor by applying the PNTs @ NiMoS core-shell structure composite electrode material obtained by the preparation method comprises the following operation processes:
(1) preparing nitrogen-doped carbon nanotubes (N-CNTs);
(2) preparing an N-CNTs negative plate;
mixing N-CNTs, carbon black and Polytetrafluoroethylene (PTFE) dispersion, dripping distilled water and ethanol to form paste, and coating the paste on foamed nickel with the coating area of 1cm multiplied by 1 cm. Then putting the obtained product into a vacuum drying oven at 60 ℃ for vacuum drying for 24 hours, and pressing the obtained product into sheets by using a double-roller machine to obtain N-CNTs negative plates;
(3) preparing a PNTs @ NiMoS positive plate;
mixing a PNTs @ NiMoS core-shell structure composite electrode material, carbon black and PTFE dispersion liquid, dropwise adding distilled water and ethanol to form paste, coating the paste on foamed nickel, wherein the coating area is 1cm multiplied by 1cm, then putting the paste into a vacuum drying oven at 60 ℃ for vacuum drying for 24h, and pressing the dried paste into a sheet by using a double-roller machine to obtain a PNTs @ NiMoS positive plate;
(4) assembling a water system asymmetric supercapacitor;
and (3) placing a polypropylene diaphragm between the N-CNTs negative plate obtained in the step (2) and the PNTs @ NiMoS positive plate obtained in the step (3), clamping the positive plate and the negative plate by using an organic glass plate, fixing the positive plate and the negative plate by using a polytetrafluoroethylene screw, and injecting a KOH solution with the concentration of 6mol/L between the positive plate and the negative plate as an electrolyte, thus obtaining the water system asymmetric supercapacitor.
Further, the specific operation process of step (1) is as follows:
placing PNTs in a high temperature tube furnace in N2Under the protection of (2), heating to 600 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 3h, and then cooling to room temperature to obtain the N-CNTs.
Further limiting, in the step (2), the mass ratio of the N-CNTs to the carbon black to the PTFE is 8:1: 1; in the step (3), the mass ratio of the PNTs @ NiMoS core-shell structure composite electrode material to the carbon black to the PTFE is 8:1: 1.
Further limiting, the mass ratio of the materials on the positive plate and the negative plate in the step (4) is 3: 7.
The invention has the following beneficial effects: according to the preparation method, the PNTs is used as a core, the NiMoS nanosheets with high specific capacitance are grown on the surface of the PNTs in situ by a hydrothermal method, and the PNTs @ NiMoS composite electrode material with the core-shell structure is prepared, wherein the NiMoS nanosheets serving as the shell provide high specific capacitance, and the PNTs serving as the core is beneficial to rapid transmission of electrons/ions, so that the utilization rate of the active material is improved. The specific capacitance of the optimal PNTs @ NiMoS-20 obtained by the invention reaches 1557.2F/g when the current density is 1A/g, and 84.9% of the initial capacitance can be still maintained after testing for 2000 cycles when the current density is 5A/g, which are superior to the PNTs and the NiMoS. The PNTs @ NiMoS-20 positive plate and the N-CNTs negative plate prepared by the method are assembled into the water system asymmetric super capacitor, the energy density is up to 63.7Wh/kg when the power density is 1044.7W/kg, the energy density is still kept at 35.8Wh/kg even if the power density is increased to 13719.1W/kg, the asymmetric super capacitor has excellent cycle life, and the specific capacitance value of the asymmetric super capacitor is still kept at 84.9% of the initial value after 5000 cycles of testing at the current density of 5A/g. In addition, the preparation method of the PNTs @ NiMoS core-shell structure composite electrode material and the water system asymmetric supercapacitor thereof have the following advantages:
(1) the NiMoS synthesized by the method improves the charge storage capacity of the material by utilizing the synergistic effect of a plurality of valence states of nickel and molybdenum; the synthesized NiMoS nano-sheet has an increased specific surface area and more active sites, and can improve the utilization rate of active substances.
(2) According to the invention, NiMoS nanosheets and PNTs are compounded to prepare a PNTs @ NiMoS composite electrode material with a core-shell structure, and the PNTs are used as a conductive network to provide a path for rapid transmission of electrons in the composite material; the PNTs are used as the cores, so that the agglomeration of the NiMoS nano-sheets is effectively reduced, more active sites are exposed, and the rapid transmission of ions is facilitated; meanwhile, the PNTs can be used as pseudocapacitance materials to store partial charges through doping/de-doping processes.
(3) The PNTs @ NiMoS// N-CNTs water system asymmetric super capacitor assembled by the method has excellent energy-power output performance.
(4) The preparation method provided by the invention also has the advantages of simple operation process, low raw material cost, safe and pollution-free preparation process, accordance with the requirements of green production, ecological concept of environmental protection and the like.
Drawings
FIG. 1a is an SEM image of PNTs prepared in example 1;
FIG. 1b is a TEM image of PNTs prepared in example 1;
FIG. 1c is an SEM image of PNTs @ NiMoS-20 prepared in example 3;
FIG. 1d is a TEM image of the PNTs @ NiMoS-20 prepared in example 3 with an inset image being an HTEM image;
FIG. 2a is an SEM image of PNTs @ NiMoS-10 prepared in example 4;
FIG. 2b is an SEM image of the PNTs @ NiMoS-30 prepared in example 5;
FIG. 2c is an SEM image of PNTs @ NiMoS-40 prepared in example 6;
FIG. 3 is an X-ray diffraction (XRD) contrast plot of PNTs, NiMoS and PNTs @ NiMoS-20;
FIG. 4 is a graph of Fourier Infrared Spectroscopy (FT-IR) comparison of PNTs, NiMoS and PNTs @ NiMoS-20;
FIG. 5a is a graph of X-ray photoelectron spectroscopy contrast for PNTs, NiMoS and PNTs @ NiMoS-20;
FIG. 5b is a comparison of high resolution X-ray photoelectron spectroscopy of N1s in PNTs and PNTs @ NiMoS-20;
FIG. 5c is a comparison of high resolution X-ray photoelectron spectroscopy of Ni 2p in NiMoS and PNTs @ NiMoS-20;
FIG. 5d is a comparison of high resolution X-ray photoelectron spectroscopy of C1s in PNTs and PNTs @ NiMoS-20;
FIG. 5e is a comparison of high resolution X-ray photoelectron spectroscopy of Mo 3d in NiMoS and PNTs @ NiMoS-20;
FIG. 5f is a comparison of high resolution X-ray photoelectron spectroscopy of S2 p in NiMoS and PNTs @ NiMoS-20;
FIG. 6a is a graph comparing Cyclic Voltammetry (CV) curves at a scan rate of 10mV/s for PNTs, NiMoS, and PNTs @ NiMoS-20;
FIG. 6b is a graph comparing CV curves at a scan rate of 10mV/s for PNTs @ NiMoS-10, PNTs @ NiMoS-20, PNTs @ NiMoS-30, and PNTs @ NiMoS-40;
FIG. 6c is a graph comparing constant current charge and discharge (GCD) curves for PNTs, NiMoS, and PNTs @ NiMoS-20 at a current density of 1A/g;
FIG. 6d is a graph comparing the GCD curves at a current density of 1A/g for PNTs @ NiMoS-10, PNTs @ NiMoS-20, PNTs @ NiMoS-30, and PNTs @ NiMoS-40;
FIG. 6e is a Nyquist plot and corresponding fitted curves for PNTs, NiMoS and PNTs @ NiMoS-20;
FIG. 6f is the specific capacitance of PNTs, NiMoS and PNTs @ NiMoS-20 at different current densities;
FIG. 6g is the cycling stability of PNTs, NiMoS and PNTs @ NiMoS-20 at 5A/g current density;
FIG. 7a is a CV curve of N-CNTs prepared in example 7 at a scan rate of 10 mV/s;
FIG. 7b is a GCD curve of N-CNTs prepared in example 7 at a current density of 1A/g;
FIG. 8a is a CV curve for N-CNTs and PNTs @ NiMoS-20 at a scan rate of 30mV/s in a three electrode system;
FIG. 8b is a CV curve of the water system asymmetric supercapacitor made in example 9 over a range of voltages at a scan rate of 30 mV/s;
FIG. 8c is a CV curve of the water system asymmetric supercapacitor made in example 9 at different scan rates;
FIG. 8d is a GCD curve of the water-based asymmetric supercapacitor made in example 9 at different current densities;
FIG. 8e is the specific capacitance of the water-based asymmetric supercapacitor prepared in example 9 at different current densities;
FIG. 8f is the cycle stability at 5A/g current density for the water-based asymmetric supercapacitor made in example 9;
fig. 8g is a Ragone plot of the water-based asymmetric supercapacitor prepared in example 9 and a comparison of energy density and power density with other bimetallic sulfide-based water-based asymmetric supercapacitors.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The experimental procedures used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and apparatus used, unless otherwise specified, are conventional in the art and are commercially available to those skilled in the art.
Example 1: preparation of PNTs
Dissolving 0.049g of methyl orange in 125mL of distilled water, stirring and dissolving to obtain an orange red solution, placing the orange red solution in a three-necked bottle, stirring in an ice-water bath at 5 ℃, dissolving 2.43g of ferric trichloride hexahydrate in 25mL of distilled water, slowly and dropwise adding the solution into the three-necked bottle, continuing stirring, then dropwise adding 0.21mL of pyrrole monomer into the three-necked bottle, continuously stirring for 12h, filtering to obtain a black precipitate, washing with distilled water and absolute ethyl alcohol for several times until the filtrate becomes colorless, and then placing the obtained black product in a vacuum drying oven at 60 ℃ for vacuum drying for 12h to obtain PNTs.
Example 2: preparation of NiMoS
0.75mmol of sodium molybdate dihydrate (Na) was weighed2MoO4·2H2O), 0.75mmol nickel nitrate hexahydrate (NiNO)3·6H2O) and 4mmol of thiourea (CH)4N2S) is dissolved in 30mL of mixed solution of distilled water and glycol (the volume ratio of glycol to distilled water is 1:1), ultrasonic treatment is continued for 15min, and 1mL of triethylamine ((C) is added dropwise2H5)3N), continuing ultrasonic treatment for 10min, transferring the suspension into a 40mL hydrothermal reaction kettle, reacting at 150 ℃ for 6h, naturally cooling to room temperature, filtering, washing with distilled water and absolute ethyl alcohol for several times, and vacuum-drying in a vacuum drying oven at 60 ℃ for 12h to obtain NiMoS.
Example 3: preparation of PNTs @ NiMoS-20
20mg of the PNTs prepared in example 1 were ultrasonically dispersed in 30mL of a mixed solution of distilled water and ethylene glycol (volume ratio of ethylene glycol to distilled water: 1), and 0.75mmol of Na was added2MoO4·2H2O、0.75mmol NiNO3·6H2O and 4mmol CH4N2S is dissolved in the suspension, then ultrasonic treatment is carried out for 15min, and 1mL (C) is added dropwise2H5)3And N, continuing ultrasonic treatment for 10min, transferring the suspension into a 40mL hydrothermal reaction kettle, reacting at 150 ℃ for 6h, naturally cooling to room temperature, filtering, washing with distilled water and absolute ethyl alcohol for several times, and vacuum-drying in a vacuum drying oven at 60 ℃ for 12h to obtain PNTs @ NiMoS-20.
Example 4: preparation of PNTs @ NiMoS-10
10mg of the PNTs prepared in example 1 were ultrasonically dispersed in 30mL of a mixed solution of distilled water and ethylene glycol (volume ratio of ethylene glycol to distilled water: 1), and 0.75mmol of Na was added2MoO4·2H2O、0.75mmol NiNO3·6H2O and 4mmol CH4N2S is dissolved in the suspension, then ultrasonic treatment is carried out for 15min, and 1mL (C) is added dropwise2H5)3And N, continuing ultrasonic treatment for 10min, then transferring the suspension into a 40mL hydrothermal reaction kettle, reacting at 150 ℃ for 6h, naturally cooling to room temperature, filtering, washing with distilled water and absolute ethyl alcohol for several times, and then putting in a vacuum drying oven at 60 ℃ for vacuum drying for 12h to obtain PNTs @ NiMoS-10.
Example 5: preparation of PNTs @ NiMoS-30
30mg of the PNTs prepared in example 1 were ultrasonically dispersed in 30mL of a mixed solution of distilled water and ethylene glycol (volume ratio of ethylene glycol to distilled water: 1), and 0.75mmol of Na was added2MoO4·2H2O、0.75mmol NiNO3·6H2O and 4mmol CH4N2S is dissolved in the suspension, then ultrasonic treatment is carried out for 15min, and 1mL (C) is added dropwise2H5)3And N, continuing ultrasonic treatment for 10min, transferring the suspension into a 40mL hydrothermal reaction kettle, reacting at 150 ℃ for 6h, naturally cooling to room temperature, filtering, washing with distilled water and absolute ethyl alcohol for several times, and vacuum-drying in a vacuum drying oven at 60 ℃ for 12h to obtain PNTs @ NiMoS-30.
Example 6: preparation of PNTs @ NiMoS-40
40mg of the PNTs prepared in example 1 were ultrasonically dispersed in 30mL of a mixed solution of distilled water and ethylene glycol (volume ratio of ethylene glycol to distilled water: 1), and 0.75mmol of Na was added2MoO4·2H2O、0.75mmol NiNO3·6H2O and 4mmol CH4N2S is dissolved in the suspension, then ultrasonic treatment is carried out for 15min, and 1mL (C) is added dropwise2H5)3And N, continuing ultrasonic treatment for 10min, then transferring the suspension into a 40mL hydrothermal reaction kettle, reacting at 150 ℃ for 6h, naturally cooling to room temperature, filtering, washing with distilled water and absolute ethyl alcohol for several times, and then putting in a vacuum drying oven at 60 ℃ for vacuum drying for 12h to obtain PNTs @ NiMoS-40.
And performing structural characterization and performance test on the PNTs, NiMoS, PNTs @ NiMoS-20, PNTs @ NiMoS-10, PNTs @ NiMoS-30 and PNTs @ NiMoS-40 respectively obtained in the embodiment.
(1) The microscopic morphologies of PNTs, NiMoS, PNTs @ NiMoS-10, PNTs @ NiMoS-20, PNTs @ NiMoS-30 and PNTs @ NiMoS-40 were observed, and the results are shown in FIGS. 1a to 2 c.
In which, fig. 1a and 1b are SEM and TEM images of PNTs, respectively, from which it is evident that they have a uniform tubular structure with a diameter of about 250 nm. FIG. 1c is an SEM image of PNTs @ NiMoS-20, it can be clearly seen that NiMoS nano-sheets uniformly grow on the outer surface of the PNTs to form a honeycomb structure, a TEM photograph (FIG. 1d) of the PNTs @ NiMoS-20 shows that the PNTs @ NiMoS-20 has a distinct core-shell structure, and the thickness of the NiMoS nano-sheet shell is about 150-. In addition, HTEM observation of the NiMoS shell region in PNTs @ NiMoS-20 was also performed, and as shown in the inset of FIG. 1d, two lattice fringes with widths of 0.28nm and 0.61nm, respectively, were clearly visible, which correspond to the (300) crystal plane of nickel sulfide and the (002) crystal plane of molybdenum disulfide, respectively.
FIGS. 2a-2c are SEM images of composite materials with different dosage of PNTs, and comparing FIG. 1c with FIGS. 2a-2c, it can be seen that NiMoS nano-sheets in PNTs @ NiMoS-20 (FIG. 1c) uniformly grow on the outer surface of the PNTs to form a honeycomb structure. When the PNTs was used at 10mg, the PNTs was unevenly covered in the composite (as shown in fig. 2 a), whereas when the PNTs was used at 30mg and 40mg, agglomeration of NiMoS nanoplates occurred in the composite (as shown in fig. 2b and 2 c). It can be seen that the synthesized PNTs @ NiMoS composite material has the most uniform shell-core structure when the dosage of the PNTs is 20 mg.
(2) X-ray diffraction characterization was performed for PNTs, NiMoS and PNTs @ NiMoS-20, with the contrast curves shown in FIG. 3.
As can be seen from FIG. 3, the XRD pattern of the PNTs showed a broad peak at 15-30 ℃ 2. theta. indicating that the PNTs had low crystallinity. The characteristic peaks of the NiMoS are mainly located at 18.4 °, 30.3 °, 32.2 °, 35.7 °, 40.5 °, 48.9 °, 50.2 °, 52.7 °, 56.3 °, 57.5 ° and 59.7 °, which are completely coincident with the (110), (101), (300), (021), (211), (131), (410), (401), (321), (330) and (012) crystal planes of nickel sulfide according to the standard card (PDF # 97-015-. In addition, it can be seen from the figure that XRD peaks of PNTs @ NiMoS-20 are all from NiMoS, and no other miscellaneous peaks appear, indicating that the crystal phase structure of NiMoS synthesized in situ on the surface of PNTs by a hydrothermal method is not affected.
(3) Fourier infrared spectroscopy characterization was performed on PNTs, NiMoS and PNTs @ NiMoS-20, with the comparison curves shown in FIG. 4.
As can be seen from FIG. 4, in the infrared spectrum of the PNTs, it is located at 918cm-1The peak at (B) is due to out-of-plane deformation vibration of C-H, and is located at 1035cm-1And 1305cm-1The peak at (a) is mainly attributed to the in-plane deformation vibration and the stretching vibration of C — H. At 1184cm-1The peak mainly comes from C-N stretching vibration and is positioned at 1470cm-1And 1561cm-1The two peaks are due to the symmetric and asymmetric oscillations of the pyrrole ring. In the infrared spectrum of NiMoS, at 624cm-1And 1095cm-1The peak mainly comes from the stretching vibration of Ni-S in NiMoS. The peaks for PNTs @ NiMoS-20 are mainly from PNTs and NiMoS.
In conclusion, according to TEM, XRD and FT-IR test results, the PNTs @ NiMoS core-shell structure composite material can be successfully synthesized in the experiment.
(4) The X-ray photoelectron spectra of PNTs, NiMoS and PNTs @ NiMoS-20 were characterized and the comparison curve is shown in FIG. 5 a.
As shown in FIG. 5a, PNTs @ NiMoS-20 mainly contains C, N, S, Ni, Mo and other elements, wherein O is mainly caused by the sample exposed to air.
High resolution X-ray photoelectron spectra of C, N, S, Ni and Mo elements in PNTs, NiMoS and PNTs @ NiMoS-20 are shown in FIGS. 5 b-5 f.
As shown in fig. 5b, N1s of PNTs was peaked as imine nitrogen (═ N-), pyrrole nitrogen (— NH-), and nitrogen with positive charge (— NH-)+-) at 397.6eV, 399.6eV and 401.7eV, respectively. Ni 2p of NiMoS (FIG. 5c) is mainly peaked as Ni 2+2p3/2、Ni 3+2p3/2、Ni 2+2p1/2、Ni 3+2p1/2And two corresponding satellite peaks, located at 852.1eV, 854.8eV, 860.1eV, 869.4eV, 872.6eV, and 878.8eV, respectively. The corresponding partial peaks of N1s and Ni 2p in PNTs @ NiMoS-20 were shifted toward lower and higher binding energies, respectively, as compared to PNTs and NiMoS, which also indicates that there is an interaction between PNTs and NiMoS in the composite and that electrons are transferred from the Ni atom in NiMoS to the N atom in PNTs. In addition, as shown in fig. 5d, the PNTs @ NiMoS-20 has the same positions as the three peaks C-C, C-N and C-O of C1s of the PNTs, which are located at 284.6eV, 286.0eV and 287.1eV, respectively. As shown in FIG. 5e, Mo 3d in NiMoS is mainly peaked as Mo4+And Mo6+Comprising Mo4 +3d5/2、Mo 4+3d3/2、Mo 6+3d5/2And Mo 6+3d3/2At 229.1eV, 232.2eV, 232.8eV, and 235.9eV, respectively. The weak peak at 226.6eV in fig. 5e is mainly from S2S. It can be seen from FIG. 5f that S2 p is mainly peaked as S2 p in NiMoS3/2And S2 p1/2And corresponding satellite peaks at 163.1eV, 164.7eV and 169.7eV, respectively. It can be seen from FIGS. 5e and 5f that the peak positions of Mo and S are the same for the PNTs @ NiMoS-20 and NiMoS, indicating that there is no interaction between the Mo and S atoms of the PNTs and NiMoS. The X-ray photoelectron spectroscopy test result further proves that the PNTs @ NiMoS composite material is successfully synthesized by the experiment, and electrons are transmitted between N in the PNTs and Ni in the NiMoS, so that the electrochemical performance of the composite material can be improved.
(5) And performing electrochemical performance test on the three-electrode system by adopting a CHI660E electrochemical workstation on PNTs, NiMoS, PNTs @ NiMoS-20, PNTs @ NiMoS-10, PNTs @ NiMoS-30 and PNTs @ NiMoS-40. The three-electrode testing device adopts a platinum electrode as an auxiliary electrode, an Hg/HgO electrode as a reference electrode, an electrode to be tested as a working electrode and an electrolyte of 6 mol/LKOH. The preparation method of the electrode to be tested comprises the following steps: firstly, putting foamed nickel with the thickness of 1.5mm into absolute ethyl alcohol and distilled water, removing impurities on the foamed nickel by ultrasonic treatment for 30min, and then putting the foamed nickel into a 60 ℃ oven to be dried for later use. Then, PNTs, NiMoS, PNTs @ NiMoS-20, PNTs @ NiMoS-10, PNTs @ NiMoS-30 and PNTs @ NiMoS-40 are respectively mixed with carbon black and PTFE according to the mass ratio of 8:1:1, distilled water and ethanol are dripped to form paste, the paste is coated on foamed nickel, the coating area is 1cm multiplied by 1cm, the paste is placed in a vacuum drying box at 60 ℃ for vacuum drying for 24 hours, and then the paste is pressed into a sheet by a double-roller machine, so that the electrode to be measured is obtained. The mass of the substance on the electrode to be measured was 3 mg.
FIGS. 6a and 6b are CV test curves for PNTs, NiMoS, PNTs @ NiMoS-20, PNTs @ NiMoS-10, PNTs @ NiMoS-30, and PNTs @ NiMoS-40 with a potential window of 0-0.7V and a scan rate of 10 mV/s. It can be seen from the figure that the CV curves of each sample have distinct redox peaks, indicating that these materials have pseudocapacitance properties, which in composites are mainly provided by PNTs, which stores charge mainly by doping/dedoping with electrolyte ions during charging and discharging, and NiMoS, which stores charge by reversible faradaic redox reactions during charging and discharging, according to equations 1-1 and 1-2 below.
And the oxidation-reduction peak current and the closed curve area of the PNTs @ NiMoS-20 are higher than those of other electrode materials, so that the PNTs @ NiMoS-20 has the optimal capacitance performance.
FIGS. 6c and 6d are GCD curves of PNTs, NiMoS, PNTs @ NiMoS-20, PNTs @ NiMoS-10, PNTs @ NiMoS-30 and PNTs @ NiMoS-40 at a current density of 1A/g, and it can be clearly seen that the curves have obvious potential plateaus, and the potential plateaus are matched with the potential positions of the redox peaks of the CV curves, further confirming that the materials mainly store energy through Faraday redox reactions in the charging and discharging processes. PNTs @ NiMoS-20 has the longest discharge time among these electrode materials, indicating that PNTs @ NiMoS-20 has the largest capacitance value. The specific capacitance of PNTs @ NiMoS-20 reached 1557.2F/g, which is much higher than that of the other electrode materials described above, at a current density of 1A/g, as calculated from equations 1-3 below.
In the formula: ce(F/g) is the specific capacitance of the electrode material; i (A) is charging and discharging current; Δ t(s) is the discharge time; Δ v (v) is the potential difference at which the IR drop is removed by the discharge process; m (g) is the mass of the active material on the electrode sheet.
And performing electrochemical impedance spectroscopy test on the PNTs, NiMoS and PNTs @ NiMoS-20, and further exploring the reaction kinetics of the PNTs, NiMoS and PNTs @ NiMoS-20 in the charging and discharging processes. Fig. 6e is a nyquist plot of the synthesized electrode material and an equivalent circuit diagram used in the fitting using Zview software, the values of the fitting being shown in table 1 below.
TABLE 1
RsRepresents the solution resistance;
CPETa capacitance value when CPEP is 1;
CPEPrepresents a constant phase element index;
Rctrepresents a charge transfer resistance;
WRrepresents diffusion resistance (Warburg diffusion resistance);
WTrepresents the diffusion time constant;
WPrepresenting a fractional index between 0 and 1.
The intercept of the curve with the X axis in the high frequency region represents the solution resistance (R)s) From Table 1, it can be seen that R is for all samplessThe values were all less than 1 Ω, indicating that these electrode materials have good wettability for KOH electrolyte. There is also a semicircle in the high frequency region whose diameter represents the charge transfer resistance (R)ct). In addition, the slope of the line in the low frequency region is determined by the diffusion of ions, also known as the Wobbe diffusion resistanceAnti (W)R). Notably, PNTs @ NiMoS-20 has a lower R than NiMoSctAnd WRThe result shows that the PNTs is favorable for electron transmission and electrolyte ion diffusion as a core, so that the PNTs @ NiMoS-20 has better rate performance.
FIG. 6f shows the specific capacitance of PNTs, NiMoS and PNTs @ NiMoS-20 calculated according to equations 1-3 at different current densities. As can be seen from the graph, the specific capacitance value of PNTs @ NiMoS-20 remained 52.2% higher than the initial specific capacitance value when the current density was increased from 1A/g to 20A/g, which is higher than PNTs (43.5%) and NiMoS (36.8%).
In addition, PNTs, NiMoS and PNTs @ NiMoS-20 were also tested for cycle stability by constant current charging and discharging at a current density of 5A/g, as shown in FIG. 6g, after 2000 cycles of charging and discharging, PNTs @ NiMoS-20 still retained 84.9% of the initial capacitance, which was higher than that of PNTs (80.3%) and NiMoS (65.4%). The PNTs @ NiMoS-20 showed excellent cycle life, primarily due to its own specific core-shell structure and synergy between the PNTs core and the NiMoS shell.
Example 7: preparation of N-CNTs
0.1g of the PNTs prepared in example 1 was weighed into a small porcelain boat (1 cm. times.4 cm), and the boat was placed in a high temperature tube furnace under N2Under the protection of (2), heating to 600 ℃ at the heating rate of 5 ℃/min, keeping at the temperature for 3h, then stopping heating, and waiting for the sample to be naturally cooled to room temperature to obtain the N-CNTs.
Example 8: preparation of PNTs @ NiMoS-20 positive plate and N-CNTs negative plate
The method comprises the steps of adopting foamed nickel as a current collector, placing a strip with the thickness of 1.5mm and the size of 1cm multiplied by 6cm in absolute ethyl alcohol and distilled water, carrying out ultrasonic treatment for 30min to remove impurities on the foamed nickel, then placing the foamed nickel in a 60 ℃ drying oven, and drying for later use.
PNTs @ NiMoS-20 prepared in example 3 and N-CNTs prepared in example 7 were mixed with carbon black and PTFE, respectively, in a mass ratio of 8:1:1, and distilled water and ethanol were added dropwise to form a paste, which was then applied onto nickel foam with an area of 1cm × 1 cm. And finally, putting the electrode slice into a vacuum drying oven at 60 ℃ for vacuum drying for 24h, and pressing the electrode slice into a slice by using a double-roller machine to obtain a PNTs @ NiMoS-20 positive plate and an N-CNTs negative plate. Wherein the mass of the matter on the PNTs @ NiMoS-20 positive plate is 3mg, and the mass of the matter on the N-CNTs negative plate is 7 mg.
Example 9: preparation of PNTs @ NiMoS-20// N-CNTs water system asymmetric supercapacitor
In this embodiment, a polypropylene diaphragm is placed between the PNTs @ NiMoS-20 positive plate and the N-CNTs negative plate prepared in the embodiment 8, the positive plate and the negative plate are clamped by an organic glass plate and fixed by polytetrafluoroethylene screws, and KOH solution with the concentration of 6mol/L is injected between the positive plate and the negative plate as electrolyte by adopting a negative pressure imbibition method, so that the PNTs @ NiMoS-20// N-CNTs water system asymmetric supercapacitor is obtained.
The performances of the water-based asymmetric supercapacitors of N-CNTs and PNTs @ NiMoS-20// N-CNTs obtained in example 7 and example 9, respectively, were tested, and the test results are shown in FIGS. 7a to 7b and FIGS. 8a to 8 g.
FIGS. 7a and 7b are CV curves of N-CNTs at a scan rate of 10mV/s and GCD curves at a current density of 1A/g, and it can be seen that the CV curves are quasi-rectangular and the GCD curves exhibit non-linear behavior, indicating that the capacitance of N-CNTs includes double layer capacitance and pseudocapacitance.
FIG. 8a is a CV plot of PNTs @ NiMoS-20 and N-CNTs in a three-electrode system with a scan rate of 30mV/s and potential ranges of 0-0.7V and-1-0V, respectively. According to the test results of FIG. 8a, the PNTs @ NiMoS-20// N-CNTs water-based asymmetric supercapacitor prepared in example 9 was tested for its operating voltage range by CV, FIG. 8b is the CV curve of the water-based asymmetric supercapacitor at a scan rate of 30mV/s for different voltage ranges, and it is clear from FIG. 8b that the prepared water-based asymmetric supercapacitor showed a redox peak on the CV curve, indicating that the capacitance of the water-based asymmetric supercapacitor comes from the double layer capacitance and the pseudocapacitance associated with the Faraday redox reaction. When the voltage reached 1.7V, an oxygen evolution peak appeared. Therefore, 0-1.6V is selected as the optimal operating voltage range of the water system asymmetric supercapacitor and further research is carried out.
FIG. 8c shows the CV curve for an increase in the water based asymmetric supercapacitor from 10mV/s to 100mV/s, and it can be seen that there is no significant distortion in the CV curve with increasing scan rate, confirming the good rate capability of the supercapacitor. FIG. 8d is a GCD curve for PNTs @ NiMoS-20// N-CNTs at 1-10A/g, with a non-linear shape and a pronounced voltage plateau, consistent with CV test results (as shown in FIG. 8 b), indicating that PNTs @ NiMoS-20// N-CNTs have pseudocapacitive properties.
The specific capacitance of the PNTs @ NiMoS-20// N-CNTs water system asymmetric supercapacitor is calculated by the formula 1-4.
In the formula: csIs the specific capacitance (F/g) of the asymmetric supercapacitor; i is a charge-discharge current (A); Δ t is the discharge time(s); Δ V is the potential difference (V) after IR drop is removed in the discharge process; m is the mass (g) of all active materials on the electrode sheet.
Calculated according to equations 1-4, the specific capacitances of the PNTs @ NiMoS-20// N-CNTs were 179.1F/g, 125.6F/g, 111.6F/g, 104.3F/g and 100.7F/g, respectively, at current densities of 1A/g, 2A/g, 3A/g, 5A/g and 10A/g (as shown in FIG. 8 e). It can be seen from the figure that when the current density is increased from 1A/g to 10A/g, the specific capacitance of the asymmetric supercapacitor still retains 56.2% of the initial value, which proves that the asymmetric supercapacitor has better rate capability. In addition, the cycle life of the PNTs @ NiMoS-20// N-CNTs is tested, and as shown in FIG. 8f, the capacitance value of the super capacitor still keeps 84.9% of the initial value after 5000 cycles of charge and discharge tests at the current density of 5A/g, which indicates that the PNTs @ NiMoS-20// N-CNTs have good cycle stability.
The power density and energy density of the PNTs @ NiMoS-20// N-CNTs water-based asymmetric supercapacitor are calculated by the following formulas 1-5 and 1-6, respectively.
In the formula: e is the energy density of the asymmetric supercapacitor (Wh/kg); p is the power density (W/kg) of the asymmetric supercapacitor.
The calculation results are shown in FIG. 8g, and the PNTs @ NiMoS-20// N-CNTs water system asymmetric supercapacitor has the energy density as high as 63.7Wh/kg at the power density of 1044.7W/kg, and the energy density is still kept at 35.8Wh/kg even if the power density is increased to 13719.1W/kg. The energy density and power density of the super capacitor are obviously superior to those of other bimetallic sulfide-based water system asymmetric super capacitors (as shown in figure 8 g), such as Ni-Mo-O-S// AC (when the power density is 850W/kg, the energy density is 50.6Wh/kg), 40cyc @ NMSNi// N, O-AC (when the power density is 1500W/kg, the energy density is 35Wh/kg), NiMoS4A// AC (energy density of 35Wh/kg at 400W/kg), RNMS-36// rGO (energy density of 32.6Wh/kg at 399.8W/kg), NMS/CNT// AC (energy density of 40Wh/kg at 400W/kg), MN-1// AC (energy density of 37.2Wh/kg at 800W/kg), NiS2/CoS2(power density of 800W/kg, energy density of 53.9 Wh/kg), MNS-G-2.5// rGO (power density of 416.6W/kg, energy density of 38.9Wh/kg), NiCo2S4The power density was 750W/kg, the energy density was 34.7Wh/kg, and the power density was 303.4W/kg, and the power density was 58.9Wh/kg for NMOS-1:3// AC/NF.
In conclusion, the PNTs @ NiMoS-20 synthesized by the experiment has high specific capacitance and good cycle stability, and has great application potential in the aspect of energy storage devices with high energy-power output performance.
Claims (10)
1. A preparation method of a PNTs @ NiMoS core-shell structure composite electrode material is characterized by comprising the following steps:
step 1, preparing PNTs;
and 2, preparing the PNTs @ NiMoS core-shell structure composite electrode material by using the PNTs, the sodium molybdate dihydrate, the nickel nitrate hexahydrate, the thiourea and the triethylamine which are obtained in the step 1 as raw materials.
2. The preparation method of the PNTs @ NiMoS core-shell structure composite electrode material according to claim 1, wherein the specific operation process of the step 1 is as follows:
dissolving methyl orange and ferric trichloride hexahydrate in distilled water respectively to form a solution A and a solution B, then dropwise adding the solution B into the solution A to obtain a suspension, dropwise adding a pyrrole monomer into the suspension, stirring and reacting for 12 hours under the condition of an ice-water bath at 5 ℃, filtering, washing with distilled water and absolute ethyl alcohol for several times until a filtrate becomes colorless, and then placing an obtained black product in a vacuum drying oven at 60 ℃ for vacuum drying for 12 hours to obtain PNTs.
3. The preparation method of the PNTs @ NiMoS core-shell structure composite electrode material as claimed in claim 2, wherein the molar concentration ratio of methyl orange, pyrrole monomer and ferric chloride hexahydrate in the reaction solution is 0.001mol/L:0.02mol/L:0.06 mol/L.
4. The preparation method of the PNTs @ NiMoS core-shell structure composite electrode material according to claim 1, wherein the specific operation process of the step 2 is as follows:
ultrasonically dispersing the PNTs obtained in the step 1 in an ethylene glycol aqueous solution, then adding sodium molybdate dihydrate, nickel nitrate hexahydrate and thiourea, carrying out ultrasonic treatment for 15min, dropwise adding triethylamine, continuing ultrasonic treatment for 10min, then transferring the suspension into a hydrothermal reaction kettle, reacting for 6h at 150 ℃, naturally cooling to room temperature, filtering, washing with distilled water and absolute ethyl alcohol for several times, and then placing in a vacuum drying oven at 60 ℃ for vacuum drying for 12h to obtain the PNTs @ NiMoS core-shell structure composite electrode material.
5. The preparation method of the PNTs @ NiMoS core-shell structure composite electrode material as claimed in claim 4, wherein the volume ratio of ethylene glycol to distilled water in the ethylene glycol aqueous solution is 15mL:15 mL; the volume of triethylamine was 1 mL.
6. The preparation method of the PNTs @ NiMoS core-shell structure composite electrode material according to claim 4, wherein the mass molar ratio of the PNTs, the sodium molybdate dihydrate, the nickel nitrate hexahydrate and the thiourea is (10-40) mg:0.75mmol:0.75mmol:4 mmol.
7. The method for preparing the water system asymmetric supercapacitor by using the PNTs @ NiMoS core-shell structure composite electrode material prepared by the method of claim 1 is characterized by comprising the following steps of:
(1) preparing N-CNTs;
(2) preparing an N-CNTs negative plate;
mixing N-CNTs, carbon black and PTFE dispersion, dropwise adding distilled water and ethanol to form paste, coating the paste on foamed nickel with the coating area of 1cm multiplied by 1cm, then putting the paste in a vacuum drying oven at 60 ℃ for vacuum drying for 24h, and pressing the dried paste into sheets by using a double-roller machine to obtain an N-CNTs negative plate;
(3) preparing a PNTs @ NiMoS positive plate;
mixing a PNTs @ NiMoS core-shell structure composite electrode material, carbon black and PTFE dispersion liquid, dropwise adding distilled water and ethanol to form paste, coating the paste on foamed nickel, wherein the coating area is 1cm multiplied by 1cm, then putting the paste into a vacuum drying oven at 60 ℃ for vacuum drying for 24h, and pressing the dried paste into a sheet by using a double-roller machine to obtain a PNTs @ NiMoS positive plate;
(4) assembling a water system asymmetric supercapacitor;
and (3) placing a polypropylene diaphragm between the negative plate of the N-CNTs obtained in the step (2) and the PNTs @ NiMoS positive plate obtained in the step (3), clamping the positive plate and the negative plate by using an organic glass plate, fixing the positive plate and the negative plate by using a polytetrafluoroethylene screw, and injecting a KOH solution with the concentration of 6mol/L between the positive plate and the negative plate as an electrolyte to obtain the water system asymmetric supercapacitor.
8. The method for preparing the water-based asymmetric supercapacitor according to claim 7, wherein the specific operation process of the step (1) is as follows:
placing PNTs in a high temperature tube furnace in N2Under the protection of (2), heating to 600 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 3h, and then cooling to room temperature to obtain the N-CNTs.
9. The method for preparing the water-based asymmetric supercapacitor according to claim 7, wherein in the step (2), the mass ratio of N-CNTs, carbon black and PTFE is 8:1: 1; in the step (3), the mass ratio of the PNTs @ NiMoS core-shell structure composite electrode material to the carbon black to the PTFE is 8:1: 1.
10. The method for preparing a water-based asymmetric supercapacitor according to claim 7, wherein the mass ratio of the substances on the positive electrode sheet to the substances on the negative electrode sheet in the step (4) is 3: 7.
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| CN105253871A (en) * | 2015-09-25 | 2016-01-20 | 深圳博磊达新能源科技有限公司 | Nitrogen-containing carbon material for supercapacitosr, preparation method thereof, and supercapacitor electrode material |
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