CN115036144A - Preparation method and application of iron oxide/graphene composite material - Google Patents

Preparation method and application of iron oxide/graphene composite material Download PDF

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CN115036144A
CN115036144A CN202210516930.7A CN202210516930A CN115036144A CN 115036144 A CN115036144 A CN 115036144A CN 202210516930 A CN202210516930 A CN 202210516930A CN 115036144 A CN115036144 A CN 115036144A
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composite material
graphene
iron oxide
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杨梅
吴中
冯雨涵
吴君哲
李飞龙
包立达
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Bengbu College
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    • H—ELECTRICITY
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    • H—ELECTRICITY
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    • 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
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • 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
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    • Y02E60/10—Energy storage using batteries
    • 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

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Abstract

The invention discloses a preparation method and application of an iron oxide/graphene composite material, which comprises the following steps: s1: graphene oxide prepared by an improved Hummers method; s2: adding graphene oxide into deionized water, performing ultrasonic dispersion for 1H, adding ferric nitrate nonahydrate, and dropwise adding H 2 O 2 Dropwise adding HCl solution to adjust the pH value to 1-2, stirring for 20min, uniformly mixing, transferring into a reaction kettle, and carrying out hydrothermal reaction at 180 ℃ for 10 h; s3: and centrifuging the mixed solution after the reaction, respectively rinsing the remained substrate with deionized water and ethanol for three times, and performing vacuum drying at 60 ℃ for 12 hours to obtain the iron oxide/graphene composite material. Fe prepared by the invention 2 O 3 When the + RGO-2 composite material is used as an electrode material, the obvious pseudo-capacitance effect exists in a 1M KOH electrolyte, and the volume of the current density is 5mV/sThe specific capacitance is as high as 256.11F/g, the high-performance high-capacity capacitor has good rate performance and cycle stability, and the specific capacitance retention rate after the cycle is performed at 500 th.

Description

Preparation method and application of iron oxide/graphene composite material
Technical Field
The invention belongs to the field of electrode material synthesis, and particularly relates to a preparation method and application of an iron oxide/graphene composite material.
Background
Due to the development of economic society, the demand for energy is greatly increased, and the reduction of traditional fossil energy sources prompts people to concentrate on developing renewable energy technology. Under the condition of the shortage of the existing energy in China, the super capacitor becomes a research hotspot. Compared with a secondary battery, the super capacitor has higher power density, can release large current in a very short time, and is widely applied to different fields of auxiliary peak power, standby power supplies, stored renewable energy sources and the like. However, because the energy density is relatively low, it is difficult to completely replace a battery device, so that research and development of high-performance electrode materials, improvement of the stability of an electrolyte, development of a novel asymmetric capacitor, continuous optimization of a preparation process and the like are main research directions in the field of super capacitors in future. The electrode material compounding is an effective way, namely the electrode material with excellent performance is obtained by constructing a heterostructure, doping and other methods by utilizing the synergistic effect among different materials. Many researchers have selected transition metal oxides with high oxygen evolution overpotentials as the positive electrode material and carbon-based negative electrode materials to form hybrid supercapacitors in aqueous electrolytes. The transition metal oxide is a typical pseudo capacitor electrode material, the theoretical specific capacity and the energy density of the transition metal oxide are 10-100 times of those of a carbon material, the electrochemical performance is very stable, and the transition metal oxide has higher lithium storage capacity, such as SnO 2 ，MnO，Co 3 O 4 And ZnO. The iron oxide and the compound thereof have excellent capacitance performance, have the advantages of high lithium ion diffusion coefficient, no toxicity, low cost and the like, and are ideal cathode materials of lithium ion batteries. The iron compound has the characteristics of rich raw materials, low price, high specific surface area, adjustable pore size structure, modifiable metal center and the like, and is widely applied to the fields of electrochemical sensing, electrochemical catalysis, energy storage and the like. The theoretical specific surface area of the graphene is 2630m 2 Is one of the idealCarbon materials for Electrochemical Double Layer Supercapacitors (EDLCs).
Based on the above, the present invention utilizes Fe 3+ And the iron oxide/graphene composite material is synthesized by a one-step hydrothermal method under the physical and chemical action of graphene oxide, has a unique nano structure, and is beneficial to forming more electrode/electrolyte interfaces. By directly preparing the high-activity material on the surface of the graphene, a larger electrochemical reachable area is obtained by smaller aggregation. The synthesized iron oxide prepolymer has low price and is environment-friendly, and the synthesized Fe 2 O 3 The + RGO-2 nano composite material has excellent capacitance performance and has good application prospect when being used as a cathode material of a water-phase super capacitor.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a preparation method of an iron oxide/graphene composite material.
The technical scheme of the invention is summarized as follows:
a preparation method of an iron oxide/graphene composite material comprises the following steps:
s1: graphene oxide prepared by an improved Hummers method;
s2: adding graphene oxide into deionized water, performing ultrasonic dispersion for 1H, adding ferric nitrate nonahydrate, and dropwise adding H 2 O 2 Dropwise adding HCl solution to adjust the pH value to 1-2, stirring for 20min, uniformly mixing, transferring into a reaction kettle, and carrying out hydrothermal reaction at 180 ℃ for 10 h;
s3: and centrifuging the mixed solution after the reaction, respectively rinsing the remained substrate with deionized water and ethanol for three times, and performing vacuum drying for 12 hours at the temperature of 60 ℃ to obtain the iron oxide/graphene composite material.
Preferably, in S1, a specific process for preparing graphene oxide by using the modified Hummers method is as follows: adding graphite into mixed acid and stirring uniformly, wherein the mixed acid is prepared from concentrated H 2 SO 4 And rich H 3 PO 4 According to the following steps: 1 volume ratio, under the ice bath condition, KMnO is slowly added 4 Then stirring for 1h to mix them uniformly, when the solution is dark green, making water bath reaction at 40-50 deg.C for 12-24h until the solution is turned into dark brownAdding deionized water, heating to 98 deg.C for pyrolysis, and adding H dropwise 2 O 2 And (3) converting the solution from dark brown to bright yellow, standing to remove supernatant, repeatedly centrifuging, washing with water, and drying in vacuum to obtain the graphene oxide.
Preferably, the graphite, mixed acid, KMnO 4 Deionized water, H 2 O 2 The dosage ratio of the solution is 3 g: 200mL of the solution: 18 g: 300 mL: 5 mL.
Preferably, the concentrated H is 2 SO 4 Is 85 percent.
Preferably, the concentrated H 3 PO 4 Is 80 percent.
Preferably, in S2, the graphene oxide, deionized water, ferric nitrate nonahydrate, and H 2 O 2 The dosage ratio of the solution is1 g: 80mL of: (0.8-0.9) g: 0.15 mL.
Preferably, said H 2 O 2 The mass fraction of the solution is 30 percent.
The invention also provides application of the iron oxide/graphene composite material prepared by the preparation method in a super capacitor.
The invention has the beneficial effects that:
1. in the invention, Fe 3+ Taking graphene oxide as a carbon source, and preparing the iron oxide/graphene composite material, Fe, by simple hydrothermal reaction one-step synthesis method and electrostatic charge attraction self-assembly 3+ The graphene oxide electrode material has positive charges and negative charges (is electronegative), the graphene oxide electrode material and the graphene oxide electrode material are compounded through electrostatic adsorption, the specific surface area of the electrode material is increased, the conductivity of iron oxide is improved, and the electrochemical performance of the supercapacitor is further improved.
2. Fe prepared by the invention 2 O 3 The + RGO-2 composite material has good integral dispersibility, small size, uniform granularity, large-area three-dimensional iron ion diffusion channels and integral conductive network structure; after the nano iron oxide is introduced into the graphene oxide, the agglomeration of the graphene is effectively solved, and the improvementThe transport speed of electrolyte ions inside the composite material is improved.
3. Fe prepared by the invention 2 O 3 When the + RGO-2 composite material is used as an electrode material, the obvious pseudo-capacitance effect exists in 1M KOH electrolyte, the volume specific capacitance reaches 256.11F/g when the current density is 5mV/s, the rate performance and the cycle stability are better, and the specific capacitance retention rate after the cycle at 500th is high.
Drawings
FIG. 1 is a schematic diagram of the electrode assembly of the supercapacitor of the present invention;
FIG. 2 shows a view of nano-Fe 2 O 3 Comparative example 1 Fe 2 O 3 + RGO-1, Fe of example 1 2 O 3 + RGO-2 infrared spectrogram;
FIG. 3 shows nano-Fe 2 O 3 Comparative example 1 Fe 2 O 3 + RGO-1, Fe of example 1 2 O 3 An X-ray diffraction pattern of + RGO-2;
FIG. 4 shows a view of nano-Fe 2 O 3 Comparative example 1 Fe 2 O 3 + RGO-1, Fe of example 1 2 O 3 + RGO-2 particle size distribution plot;
FIG. 5 shows nano-Fe 2 O 3 Comparative example 1 Fe 2 O 3 + RGO-1, Fe of example 1 2 O 3 + RGO-2 polarization microscope images, sequentially represented by (a), (b), and (c);
FIG. 6 is Fe 2 O 3 Fe of example 1 2 O 3 CV diagrams of + GRO-2 at different sweep rates, which are sequentially represented by (a), (b);
FIG. 7 is Fe 2 O 3 Fe of example 1 2 O 3 An EIS diagram of + GRO-2 at different sweep rates, indicated by (a) and (b) in this order;
FIG. 8 is Fe 2 O 3 Fe of example 1 2 O 3 + GRO-2 GCD graph at different sweep rates and voltammogram of different cycle times, wherein (a) and (b) sequentially represent Fe 2 O 3 Fe of example 1 2 O 3 + GRO-2 GCD map at different sweep rates, (c) and (d) represent Fe in sequence 2 O 3 Fe of example 1 2 O 3 + GRO-2 voltammograms for different cycle times;
FIG. 9 shows nano-Fe 2 O 3 Fe of example 1 2 O 3 A specific capacity comparison graph is obtained by calculating the + GRO-2 composite material according to a cyclic voltammetry curve;
FIGS. 10 to 12 show graphene oxide and Fe in sequence according to example 1 2 O 3 + GRO-2 higher power Fe of example 1 2 O 3 + GRO-2 SEM picture under low power mirror;
fig. 13 is a flow chart of a preparation method of the iron oxide/graphene composite material of the present invention.
Detailed Description
The present invention is further described in detail below with reference to examples so that those skilled in the art can practice the invention with reference to the description.
The invention provides a preparation method of an iron oxide/graphene composite material, which comprises the following steps:
s1: graphene oxide prepared by an improved Hummers method: adding graphite into mixed acid and uniformly stirring, wherein the mixed acid is composed of concentrated H with the mass fraction of 85% 2 SO 4 And 80% by mass of concentrated H 3 PO 4 According to the following steps: 1 volume ratio, under the ice bath condition, KMnO is slowly added 4 Then stirring for 1H to mix uniformly, reacting in water bath at 40-50 ℃ for 12-24H when the solution is dark green until the solution turns dark brown, adding deionized water, heating to 98 ℃ for pyrolysis, and then dropwise adding 30% H 2 O 2 The solution is changed from dark brown to bright yellow, and after the solution is kept stand to remove supernatant, the solution is repeatedly centrifuged, washed and dried in vacuum to obtain graphene oxide; the graphite, mixed acid and KMnO 4 Deionized water, H 2 O 2 The dosage ratio of the solution is 3 g: 200mL of: 18 g: 300 mL: 5 mL;
s2: adding graphene oxide into deionized water, performing ultrasonic dispersion for 1H, adding ferric nitrate nonahydrate, and dropwise adding 30% H 2 O 2 Adding HCl solution dropwise to adjust the pH value to 1-2,stirring for 20min, uniformly mixing, transferring into a reaction kettle, and carrying out hydrothermal reaction at 180 ℃ for 10 h; the graphene oxide, deionized water, ferric nitrate nonahydrate and H 2 O 2 The dosage ratio of the solution is1 g: 80mL of: (0.8-0.9) g: 0.15 mL;
s3: and centrifuging the mixed solution after the reaction, respectively rinsing the remained substrate with deionized water and ethanol for three times, and performing vacuum drying at 60 ℃ for 12 hours to obtain the iron oxide/graphene composite material.
The iron oxide/graphene composite material prepared by the embodiment is applied to a super capacitor.
Example 1
A preparation method of an iron oxide/graphene composite material comprises the following steps:
s1: graphene oxide prepared by an improved Hummers method: adding 3g of graphite into 200mL of mixed acid and uniformly stirring, wherein the mixed acid is composed of concentrated H with the mass fraction of 85% 2 SO 4 And 80% by mass of concentrated H 3 PO 4 According to the following steps: 1 volume ratio, under ice bath condition, 18g KMnO is slowly added 4 Then stirring for 1H to mix uniformly, reacting in water bath at 40-50 ℃ for 12-24H when the solution is dark green until the solution turns into dark brown, adding 300mL of deionized water, heating to 98 ℃ for pyrolysis, and then adding 5mL of H with the mass fraction of 30% 2 O 2 The solution is changed from dark brown to bright yellow, and after standing and removing supernatant, repeated centrifugation, water washing and vacuum drying are carried out to obtain graphene oxide (RGO);
s2: 1g of graphene oxide (RGO) was added to 80mL of deionized water, ultrasonically dispersed for 1h, and 0.8024g of ferric nitrate nonahydrate (Fe (NO)) 3 ·9H 2 O), 0.15mL of 30% H by mass fraction is added dropwise 2 O 2 Dropwise adding HCl solution to adjust the pH value to 1.5, stirring for 20min, uniformly mixing, transferring into a reaction kettle, and carrying out hydrothermal reaction at 180 ℃ for 10 h;
s3: and centrifuging the mixed solution after the reaction, respectively rinsing the remained substrate with deionized water and ethanol for three times, and performing vacuum drying for 12 hours at the temperature of 60 ℃ to obtain the iron oxide/graphene composite material.
Comparative example 1
S1: 0.8024g of iron nitrate nonahydrate (Fe (NO)) 3 ·9H 2 O) is added into 80mL deionized water, and after stirring and dissolving, 0.15mL H with the mass fraction of 30 percent is added in drops 2 O 2 Dropwise adding HCl solution to adjust the pH value to 1.5, stirring for 20min, uniformly mixing, transferring into a reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 10h, centrifuging the mixed solution after reaction, respectively rinsing the remained substrate with deionized water and ethanol for three times, and carrying out vacuum drying at 60 ℃ for 12h to obtain an iron oxide prepolymer;
s2: and adding 1g of graphene oxide (RGO) prepared by an improved Hummers method into 80mL of deionized water, ultrasonically dispersing for 1h, adding the iron oxide prepolymer obtained in S1, stirring and dispersing, centrifuging, rinsing the remaining substrate with deionized water and ethanol for three times respectively, and drying in vacuum at 60 ℃ for 12h to obtain the iron oxide/graphene composite material.
The iron oxide/graphene composite material prepared in comparative example 1 was denoted as Fe 2 O 3 + RGO-1 composite material; the iron oxide/graphene composite material prepared in comparative example 2 was denoted as Fe 2 O 3 + RGO-2 composite material and for nano Fe 2 O 3 Comparative example 1 Fe 2 O 3 And performing characterization and electrochemical performance test on the + RGO-1 composite material.
Characterization method and test result
IR characterization was performed by using a Fourier infrared spectrometer model Nicolet iS10 of Sammer fly, Germany Bruker D8 Focus X-ray powder diffractometer to perform XRD characterization on the composite material, a Nicomp380Z3000 laser particle sizer of PSS, Germany tests the particle size of the sample, and an Axio Lab. A1 polarizing microscope of Zeiss, Germany takes pictures and the micro-morphology characteristics are characterized by a scanning electron microscope.
And (3) analyzing test results:
FIG. 2 shows a nano Fe 2 O 3 Comparative example 1 Fe 2 O 3 + RGO-1, Fe of example 1 2 O 3 The infrared spectrum absorption spectrum of the + RGO-2 shows that the main functional groups have similar peak positions and different intensities, which indicates that the mixed amount of the samples is different. At 3439cm -1 A broad peak is nearbyThe peak belongs to the stretching vibration of-OH. 1632cm -1 Characteristic absorption peaks classified into unsaturated double bonds-C ═ C-in graphene. At 1022cm -1 The peak is the bending vibration absorption peak of C-O bond adsorbed on the surface of graphene, 619cm -1 And 468cm -1 The peak is the stretching vibration absorption peak of the Fe-O bond in the inorganic fingerprint area, and after compounding, characteristic peaks all appear in the sample, which indicates that the composite material is successfully synthesized initially.
FIG. 3 is a view of nano Fe 2 O 3 Comparative example 1 Fe 2 O 3 + RGO-1, Fe of example 1 2 O 3 XRD pattern of + RGO-2, 2 theta values of three samples corresponding to Fe respectively 2 O 3 The crystal plane (PDF #33-0664) and the crystal plane C (PDF #41-1487) correspond in number to each other, and no other impurities were found. Pure substance Fe 2 O 3 A small amount of graphene is mixed in the graphene, so that a large amorphous C broad peak of the graphene appears at 24.2 degrees, which is mainly caused by large disorder of a graphene lamellar structure. The main crystal phase of the iron oxide compound added with the graphene is changed slightly before and after the experiment, and the peak of the main crystal phase is stronger, which shows that the two methods for synthesizing the compound material have no great influence on the crystal phase of the final product.
FIG. 4 shows a view of nano-Fe 2 O 3 Comparative example 1 Fe 2 O 3 + RGO-1, Fe of example 1 2 O 3 + RGO-2 particle size distribution plot, particle size distribution as follows: 122/256/431nm, 560nm and 176nm, it can be seen that the particle size distribution range of pure nano Fe2O3 is wider, the particle size distribution is more concentrated after the nano Fe2O3 is mixed with graphene, wherein the particle size of a compound prepared by adding graphene before reaction is 560nm, which is much larger than the particle size of a sample prepared by adding graphene after reaction, which is 176nm, and this shows that in example 1, Fe obtained by stirring raw materials and graphene oxide together for hydrothermal synthesis 2 O 3 The + RGO-2 has better appearance and can synthesize composite nano particles with smaller particle size.
FIG. 5 shows a view of nano-Fe 2 O 3 Comparative example 1 Fe 2 O 3 + RGO-1, Fe of example 1 2 O 3 The polarization microscope image of + RGO-2 is represented by (a), (b), and (c): nano Fe 2 O 3 The dispersion is good, the particle size is small, the distribution is uniform, and the graphene is easy to agglomerate due to a lamellar structure. The graph b shows that the graphene is in an agglomerated state, and the graph c shows that the composite is also in an agglomerated state, but the agglomeration degree of the composite is reduced relative to that of the graphene, which indicates that the graphene and the nano Fe are in an agglomerated state 2 O 3 After mixing, the agglomeration state of the graphene is improved, and the dispersibility of the composite is improved.
FIGS. 10 to 12 show graphene oxide and Fe in sequence according to example 1 2 O 3 + RGO-2 higher power Fe of example 1 under mirror 2 O 3 SEM image under + RGO-2 Low magnification mirror: as can be seen from FIG. 10, graphene oxide is a sheet-like material, and Fe can be seen from FIGS. 11 to 12 2 O 3 The + RGO-2 has no obvious agglomeration phenomenon, the obtained material has high micro-morphology consistency, and simultaneously Fe can be seen from figure 12 2 O 3 The + RGO-2 particles are uniformly distributed in the graphene matrix, and the structure can effectively reduce the side effect caused by the volume effect of the material and prevent the electrode from being pulverized and falling off.
Second, electrochemical performance test and test results
Grinding the electrode active material, polytetrafluoroethylene and acetylene black in an agate mortar according to the ratio of 8:1:1, dropwise adding a proper amount of absolute ethyl alcohol, grinding into slurry, and pressing the slurry to 1cm 2 On the foamed nickel. The iron oxide material, the iron oxide/graphene prepared in comparative example 1 and the prepared 1M KOH electrolyte form a super capacitor, which comprises three electrode systems, as shown in FIG. 1, a counter electrode of the super capacitor is usually a common platinum electrode, a working electrode is made of three synthesized nano materials, and a reference electrode is an Hg/HgO electrode filled with 1mol/L KOH. Soaking the completely assembled working electrode in the electrolyte for a sufficient time until the nano Fe is obtained 2 O 3 、Fe 2 O 3 +RGO-1、Fe 2 O 3 + RGO-2 was completely immersed in the electrolyte and electrochemical performance was tested using CHI660 electrochemical workstation in Shanghai Chenghua at room temperature.
1) Cyclic voltammetry
Cyclic Voltammetry (CV) can visually express the electrochemical behavior of the electrode surface of the electrode material in the charging-discharging process, and can also control the scanning electrode to scan for multiple times at different positions and match a triangular wave pattern to cycle for multiple times, and different reduction and oxidation reactions can occur from low potential to high potential. And obtaining CV curves under scanning of different frequencies ranging from-1V to 0V.
And (3) analyzing test results: FIG. 6 is Fe 2 O 3 Fe of example 1 2 O 3 CV diagram of + GRO-2 at different sweep rates, indicated by (a), (b) in this order: as shown in the figure, under the same scanning speed, when the voltage window is-1-0V, the nano Fe 2 O 3 And Fe 2 O 3 The current on the CV curve of the + GRO-2 composite material fluctuates along with the change of the scanning rate, but the position difference of the oxidation reduction peak is not large, and the shape of the cyclic voltammetry curve can be kept unchanged along with the continuous increase of the scanning rate, which indicates that the composite electrode has good electrochemical reversibility and conductivity and shows good pseudocapacitance behavior. Both of them showed obvious oxidation peak, but the reduction peak was relatively weak, indicating that the pseudocapacitance was determined by the electrode material. At the same scanning speed, Fe 2 O 3 The CV curve integral area of the + GRO-2 is far larger than that of the nano Fe 2 O 3 Indicating that the composite electrode has a greater specific capacitance.
2) Electrochemical impedance testing
Electrochemical Impedance (EIS) was used to investigate the diffusion of electrolyte ions in the electrode material. According to the measured impedance spectrogram, the dynamic steps and the interface structure in the electrode process can be deduced, and a plurality of parameters such as specific capacitance, resistance and the like can be obtained through the electrochemical impedance spectrogram. The scan rates we used were 5mV/s, 2mV/s, 10mV/s, 20 mV/s. By recording the difference in scanning voltage (Δ V), the weight of the active and the scanning frequency, the specific capacity can be calculated using the following equation 1 and the integral of its area:
Figure BDA0003640037210000081
in the formula: i-current, A
Upsilon-sweeping velocity, mV s -1
And (3) analysis of test results: FIG. 7 is Fe 2 O 3 Fe of example 1 2 O 3 The EIS diagram of the + GRO-2 under different sweep speeds is sequentially represented by (a) and (b), and the impedance spectrogram shows that two sample spectrograms before and after circulation have a low-frequency area straight line with a large slope and a high-frequency area circular arc with a small radius, which indicates that the sample is in good contact with the electrolyte. The intersection point of the sample and the x axis, namely the total internal resistance of the sample, is less than 3.0 omega by extrapolation, which shows that the material has very small charge transfer resistance. Fe 2 O 3 The intercept of the + GRO-2 composite electrode material on the solid axis is less than that of the nano Fe 2 O 3 Material, which shows that the internal resistance is smaller, and the linear ratio of the material to the material is nano Fe in a low-frequency region 2 O 3 The steeper the material, the faster the migration speed of the ions inside it, the more active the diffusion.
3) Constant current charge-discharge and cycle stability test
Constant current Charge-discharge (GCD), i.e., a time-dependent voltage variation curve, is measured by performing Charge-discharge tests on the electrodes at a set current density, and observing the variation curve of the discharge time and the voltage.
The stability of the super capacitor is verified by testing the cycle life of the super capacitor. Usually, a CV method (constant scanning speed) or a GCD method (constant current density) is adopted to perform a plurality of charge and discharge tests on the material, after cycling, the specific capacity has a certain loss relative to the initial specific capacity, and the ratio of the specific capacity to the initial specific capacity is called the cycle life.
FIG. 8 shows Fe 2 O 3 Fe of example 1 2 O 3 + GRO-2 GCD graph at different sweep rates and voltammogram of different cycle times, wherein (a) and (b) sequentially represent Fe 2 O 3 Fe of example 1 2 O 3 + GRO-2 GCD map at different sweep rates, (c) and (d) represent Fe in sequence 2 O 3 Fe of example 1 2 O 3 Voltammogram of + GRO-2 for different cycle numbers: from Fe 2 O 3 The curve of different current density samples has good symmetry and good capacitance characteristic seen by the constant current charge-discharge curve of + GRO-2, and the doped graphene and Fe have good capacitance characteristic 2 O 3 The + GRO-2 electrode material generates pseudo capacitance, and the radian of a discharge curve is good. In addition Fe 2 O 3 + GRO-2 has the longest discharge time at 0.5A/g and the largest specific capacitance. Fe after 500th cycles 2 O 3 The specific capacitance retention of the + GRO-2 sample was good, indicating that Fe 2 O 3 The + GRO-2 composite material is relatively stable. Fe 2 O 3 The main reasons for the higher cycle life of the + GRO-2 composite electrode material are: the pore channel generated by etching the graphene provides a rapid transfer path for electrolyte ions in the direction vertical to the graphene, and the nano Fe 2 O 3 Doped on a graphene base layer with high conductivity, solves the problem of graphene agglomeration, and is doped with Fe 2 O 3 The redox reaction occurs to provide a pseudo-capacitance, and the flexibility of the graphene-based layer can adapt to changes caused by charge storage, thereby leading to good cycling stability of the sample.
FIG. 1 shows nano Fe 2 O 3 Fe of example 1 2 O 3 And the specific capacitance value of the + GRO-2 composite material is calculated at different scanning speeds.
TABLE 1 Fe 2 O 3 、Fe 2 O 3 Specific capacitance values calculated by the + RGO-2 composite material at different scanning rates
Figure BDA0003640037210000091
FIG. 9 shows nano-Fe 2 O 3 Fe of example 1 2 O 3 The specific capacity comparison graph obtained by calculating the + GRO-2 composite material according to the cyclic voltammetry curve is shown in FIG. 9 and Table 1, and it can be seen that in the same electrode material, the lower the scanning rate is, the higher the specific capacitance value of the composite material is, and secondly, the higher the specific capacitance value can beNow Fe 2 O 3 + RGO-2 is much higher than nano Fe at the same scan rate 2 O 3 The specific capacitance value of (2). By calculation, Fe 2 O 3 The volume specific capacitance of the + RGO-2 composite electrode at 5mV/s is up to 256.11F/g, Fe 2 O 3 The reduction degree and the repair capability of the + RGO-2 are very high, so that the electrolyte can be fully immersed, the surface area of the electrode material can be enlarged, the reversible result of the redox reaction in the experimental process is ensured, and the consumption of the electrode material is also reduced to the maximum extent.
While embodiments of the invention have been disclosed above, it is not limited to the applications listed in the description and the embodiments, which are fully applicable in all kinds of fields of application of the invention, and further modifications may readily be effected by those skilled in the art, so that the invention is not limited to the specific details without departing from the general concept defined by the claims and the scope of equivalents.

Claims (8)

1. The preparation method of the iron oxide/graphene composite material is characterized by comprising the following steps:
s1: graphene oxide prepared by an improved Hummers method;
s2: adding graphene oxide into deionized water, performing ultrasonic dispersion for 1H, adding ferric nitrate nonahydrate, and dropwise adding H 2 O 2 Dropwise adding HCl solution to adjust the pH value to 1-2, stirring for 20min, uniformly mixing, transferring into a reaction kettle, and carrying out hydrothermal reaction at 180 ℃ for 10 h;
s3: and centrifuging the mixed solution after the reaction, respectively rinsing the remained substrate with deionized water and ethanol for three times, and performing vacuum drying at 60 ℃ for 12 hours to obtain the iron oxide/graphene composite material.
2. The method for preparing the iron oxide/graphene composite material according to claim 1, wherein in S1, the modified Hummers method is used for preparing the graphene oxide in a specific process: adding graphite into mixed acid and stirring uniformly, wherein the mixed acid is prepared from concentrated H 2 SO 4 And concentrated H 3 PO 4 According to the weight ratio of 10: 1 volume ofAccording to the composition, KMnO is slowly added under the ice bath condition 4 Then stirring for 1H to mix uniformly, when the solution is dark green, reacting in 40-50 deg.C water bath for 12-24H until the solution turns dark brown, adding deionized water and heating to 98 deg.C for pyrolysis, and adding H dropwise 2 O 2 And (3) converting the solution from dark brown to bright yellow, standing to remove supernatant, repeatedly centrifuging, washing with water, and drying in vacuum to obtain the graphene oxide.
3. The method for preparing the iron oxide/graphene composite material according to claim 2, wherein the graphite, the mixed acid and the KMnO are mixed 4 Deionized water, H 2 O 2 The dosage ratio of the solution is 3 g: 200mL of: 18 g: 300 mL: 5 mL.
4. The method of claim 2, wherein the concentrated H is selected from the group consisting of 2 SO 4 Is 85 percent.
5. The method of claim 2, wherein the concentrated H is selected from the group consisting of 3 PO 4 Is 80 percent.
6. The method for preparing an iron oxide/graphene composite material according to claim 1, wherein in S2, the graphene oxide, deionized water, ferric nitrate nonahydrate, and H 2 O 2 The dosage ratio of the solution is1 g: 80mL of: (0.8-0.9) g: 0.15 mL.
7. The method for preparing an iron oxide/graphene composite material according to any one of claims 3 or 6, wherein the H is 2 O 2 The mass fraction of the solution is 30 percent.
8. The application of the iron oxide/graphene composite material prepared by the preparation method according to any one of claims 1-6 in a super capacitor.
CN202210516930.7A 2022-05-12 2022-05-12 Preparation method and application of iron oxide/graphene composite material Pending CN115036144A (en)

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CN109030417A (en) * 2018-08-01 2018-12-18 广州特种承压设备检测研究院 A kind of preparation method of graphene Fiber Composites
CN110828194A (en) * 2019-11-06 2020-02-21 蚌埠学院 Method for preparing layered β -nickel hydroxide/graphene material by utilizing induction effect of surface charge
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Publication number Priority date Publication date Assignee Title
CN104008888A (en) * 2014-06-13 2014-08-27 上海利物盛企业集团有限公司 Preparation method of composite material and electrode slice for super capacitor
CN107256810A (en) * 2017-06-12 2017-10-17 中科合成油技术有限公司 A kind of iron oxide/stannic oxide/graphene nano composite and preparation method thereof and the application in ultracapacitor
US20210363015A1 (en) * 2017-07-05 2021-11-25 Fundación Tecnalia Research & Innovation Capacitive deionization electrode
CN108380176A (en) * 2018-03-01 2018-08-10 同济大学 A kind of preparation method of nanometer α-phase ferricoxide-graphene composite material of removal water body dye discoloration
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