CN113054208A

CN113054208A - Ultrasonic synthesis method and application of spiral nickel-iron supermolecular network framework nano composite material

Info

Publication number: CN113054208A
Application number: CN202110267670.XA
Authority: CN
Inventors: 肖高; 刘抒濛
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2021-03-11
Filing date: 2021-03-11
Publication date: 2021-06-29
Anticipated expiration: 2041-03-11
Also published as: CN113054208B

Abstract

The invention belongs to the field of oxygen reduction electrocatalysis, and particularly relates to an ultrasonic synthesis method and application of a spiral nickel-iron supermolecular network framework nano composite material₂O₄The composite material has the advantages of spiral-like shape, simple ultrasonic synthesis method, low cost, short reaction time, high yield, uniform appearance, large specific surface area and easy realization of industrial production. The invention is used for solving the defects of low reversibility of cathode oxygen reduction reaction, small exchange current density, high cost and toxicity of Pt-based catalytic materials and the like of the existing fuel cell catalyst, and the obtained oxygen reduction catalyst has the advantages of high potential, excellent limiting current, high stability, methanol tolerance and the like, so that C @ NiFe₂O₄Has great potential application value as a high-efficiency electrocatalyst.

Description

Ultrasonic synthesis method and application of spiral nickel-iron supermolecular network framework nano composite material

Technical Field

The invention belongs to the field of oxygen reduction electrocatalysis, and particularly relates to an ultrasonic synthesis method and application of a spiral nickel-iron supermolecular network framework nano composite material.

Background

Most of the current research on oxygen reduction electrocatalysts focuses on compounds based on the elemental composition of transition metals (Fe, Co, Ni, Mn), mainly including oxides and composites thereof, etc. Transition metals are commonly used to prepare electrocatalysts because of their diverse adsorption sites, and their unfilled orbitals and unpaired electrons, which form empty d-electron orbitals of chemisorbed bonds. Bimetallic oxides may have higher catalytic activity than single metal oxides, and even exhibit excellent catalytic activity in oxygen evolution and oxygen evolution reactions, and are receiving increasing attention from researchers. In the loaded transition metal, Co has higher catalytic activity, but the reserves in China are rare and the price is high, so that the development of the graphitized structure catalyst based on the ferronickel bimetal doping has more practical significance.

Cellulose is the most abundant renewable polymer in nature and has wide application in coating, textile, pharmacy, food and other aspects. Cellulose is also a versatile chemical support material because it contains a large number of hydroxyl groups, and stable positive or negative charges can be introduced by cationization or carboxymethylation processes. The Biomass Carbon Fiber (BCF) is low in price and rich in source, has the advantages of large specific surface area, good adsorption performance, no agglomeration and the like, but can better exert the advantages only by activating or modifying the BCF, wherein a common method is to add KOH and ZnCl₂And K₂CO₃Carrying out chemical activation; another is by doping atoms or introducing surface functional groups.

The invention mainly adopts a second method, prepares the spiral ferronickel-doped carbon fiber with a super molecular frame by one-step pyrolysis method by utilizing the doping of transition metal ions and matching with the natural structural advantages of cellulose, and keeps the advantages of high conductivity, large specific surface area and the like of the carbon fiber. The morphology structure and the composition of the electrocatalytic material are analyzed by using characterization methods such as SEM, XRD and EDX, the oxygen reduction performance of the electrocatalytic material is inspected by means of cyclic voltammetry, chronoamperometry and the like, in addition, the influence of the optimal metal proportion and the optimal calcination temperature on the ORR performance is inspected, the preparation process is optimized, and the structure-activity relationship between the material structure and the electrochemical performance is discussed by combining experimental data.

Disclosure of Invention

The invention aims to solve the problems of the existing fuel cell catalyst, and the existing fuel cell catalyst generally has the defects of very low reversibility of cathode oxygen reduction reaction, small exchange current density, very high overpotential accompanied by very high cost, toxicity and the like of a Pt-based catalytic material; based on the unique structure of cellulose, a spiral nickel-iron supermolecular network framework nano composite material is developed, and the spiral nickel-iron supermolecular network framework nano composite material has the advantages of high initial potential, half-slope potential, excellent limiting current, excellent stability, methanol tolerance and the like.

In order to achieve the purpose, the invention adopts the following technical scheme:

an ultrasonic synthesis method of a spiral nickel-iron supermolecular network framework nano composite material specifically comprises the following steps:

(1) weighing a certain amount of directly bought cellulose, putting the directly bought cellulose into a conical flask filled with deionized water, then adjusting the pH value of a solution system to 1.0-2.0 by using a buffer acid solution 2M HCl solution, sealing the conical flask by using a preservative film, and then putting the conical flask into a water bath oscillator for oscillation so as to achieve the purpose of opening a cellulose compact system, and washing the conical flask for later use;

(2) respectively and fully dissolving ferric nitrate nonahydrate and nickel nitrate hexahydrate in deionized water, pouring into cellulose, stirring for 10min (the mass ratio of the three raw materials is 1: 6: 1.5 in sequence), pouring a proper amount of 10mg/mL plant polyphenol solution into the cellulose, fully mixing, putting into an ultrasonic machine, controlling the ultrasonic output power at 200W and the temperature at (40 +/-1) DEG C, uniformly dispersing the solution in the pretreated cellulose, carrying out ultrasonic reaction for 60min, washing with water, and putting into an oven at 80 ℃ for drying for 12 h;

(3) and (3) putting the precursor obtained in the step (2) into a ark, performing high-temperature treatment in a pure argon atmosphere, and cooling to obtain the spiral ferronickel supermolecular network framework nanocomposite for the proton membrane fuel cell.

The drying temperature in the step (2) is 80 ℃, and the time is 12 hours;

the high-temperature treatment temperature in the step (3) is 950 ℃, and the reaction time is 3 h;

the active component of the proton membrane fuel cell cathode material prepared by the invention is C @ NiFe₂O₄. Due to C @ NiFe₂O₄The fuel cell has a unique spiral structure and abundant pores, increases the specific surface area, provides abundant active sites for oxygen reduction reaction, and promotes the permeation of electrolyte, so that the fuel cell shows high-efficiency catalytic performance and excellent electrochemical performances such as high stability and tolerance.

The invention has the technical advantages and beneficial effects that:

the electrocatalytic material of the invention has a spiral shape, which is mainly benefited by the natural fibrous structure of cellulose and a proper temperature rise procedure, because the cellulose contains a large number of hydroxyl groups, has high stability to introduced cations or anions, can basically keep the integrity of the shape under proper high-temperature conditions and shows a spiral-like structure. The ultrasonic synthesis method has the characteristics of full dispersion, simple process and mild conditions, is an economic and effective method, and plays an important role in doping of metal heteroatoms and stability of final appearance; the obtained active material used as a cathode electrocatalyst not only shows outstanding initial potential, half-slope potential and limiting current, but also shows the advantages of excellent stability, methanol tolerance and the like.

Drawings

FIG. 1 shows C @ NiFe obtained in example 1 of the present invention₂O₄FESEM images (a-d), elemental plane scans (e) of the sample;

FIG. 2 shows C @ NiFe obtained in example 1 of the present invention₂O₄A Transmission Electron Microscope (TEM) image (a), a High Resolution Transmission Electron Microscope (HRTEM) image (b, c) and a Selected Area Electron Diffraction (SAED) image (d) of the sample;

FIG. 3 shows C @ NiFe obtained in example 1 of the present invention₂O₄An XPS spectrum full spectrum (a), an N1s spectrogram (b), a C1s spectrogram (C), an O1 s spectrogram (d) and an Fe2p spectrogram (e) of the sample and an Ni 2p spectrogram (f);

FIG. 4 shows C @ Ni obtained in example 1 of the present inventionFe₂O₄A raman spectrum of the sample;

FIG. 5 shows C @ NiFe obtained in example 1 of the present invention₂O₄Nano material in N₂And O₂CV plot in saturated 0.1M KOH (scan range-0.9-0.1V, scan rate 50 mv/s);

FIG. 6 is a graph of C @ NiFe prepared at different temperatures obtained in example 1 of the present invention₂O₄Under the nanometer material at O₂LSV profile in saturated 0.1M KOH (scan range-0.9-0.1V, scan rate 10 mv/s);

FIG. 7 shows C @ NiFe of different metal ratios obtained in example 1 of the present invention₂O₄At O₂LSV profile in saturated 0.1M KOH (scan range-0.9-0.1V, scan rate 10 mv/s);

FIG. 8 shows C @ NiFe obtained in example 1 of the present invention₂O₄LSV diagram of the nanometer material and blank sample without adding the bimetal supermolecule framework system (scanning range is-0.9-0.1V, scanning speed is 10 mv/s);

FIG. 9 shows C @ NiFe at different rotation speeds obtained in example 1 of the present invention₂O₄LSV maps (rotation speed 625rmp, 900rmp, 1225rmp, 1600rmp, 2025rmp, scan rate 10 mv/s);

FIG. 10 shows C @ NiFe obtained in example 1 of the present invention₂O₄The curve of the K-L equation of (1);

FIG. 11 shows C @ NiFe obtained in example 1 of the present invention₂O₄And Pt/C in O₂I-t curves run in saturated 0.1M KOH for long periods of time;

FIG. 12 shows C @ NiFe obtained in example 1 of the present invention₂O₄And the i-t curve run after Pt/C addition of methanol.

FIG. 13 is a linear cyclic voltammogram comparing the final catalyst produced with the procatalyst when the synthesis conditions were changed to water bath oscillation.

Fig. 14 is an SEM image of the synthesized catalyst after changing the high temperature treatment procedure or changing the synthesis manner.

Detailed Description

The invention is further illustrated by the following figures and examples. It should be noted that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention, and those skilled in the art can make some insubstantial modifications and adjustments to the present invention based on the above disclosure and still fall within the scope of the present invention.

The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.

Example 1:

this example shows a helical structure C @ NiFe₂O₄The method of (1).

(2) respectively and fully dissolving ferric nitrate nonahydrate and nickel nitrate hexahydrate in deionized water, pouring into cellulose, stirring for 10min (the mass ratio of the three raw materials is 1: 6: 1.5 in sequence), pouring 10mg/mL plant polyphenol solution into the cellulose, fully mixing, putting into an ultrasonic machine, controlling the ultrasonic output power to be about 200W and the temperature to be (40 +/-1) DEG C, uniformly dispersing the solution in the pretreated cellulose, carrying out ultrasonic reaction for 60min, washing with water, and putting into an oven at 80 ℃ for drying for 12 h;

(3) and (3) putting the precursor obtained in the step (2) into a square boat, and carrying out high-temperature treatment in a pure argon atmosphere, wherein the temperature-raising program is set as follows: the temperature was raised from room temperature to 320 ℃ at 5 ℃/min, and after the temperature was maintained for 1.5 hours, the temperature was raised to 950 ℃ at the same rate for 1.5 hours. And after the temperature reduction is finished, obtaining the spiral ferronickel supermolecular network framework nano composite material for the proton membrane fuel cell.

FIG. 1 is C @ NiFe₂O₄FESEM image of sample, elemental plane scan. As can be seen from the figure, C @ NiFe₂O₄The composite material keeps intactThe spiral structure has different pore diameters, is favorable for the permeation of electrolyte, increases the contact area between the electrolyte and an electro-catalytic material, and can also improve O₂The transmission rate of (c). It can also be observed that C @ NiFe₂O₄The composite material has a rough surface and particle adhesion due to CO generated during calcination₂、H₂O, etc. To further understand C @ NiFe₂O₄The distribution of each element in the composite material is scanned, and the figure shows that the elements of Fe, Ni, O, N and C are uniformly distributed on the material.

FIG. 2 is C @ NiFe₂O₄Transmission Electron Microscopy (TEM) images, High Resolution Transmission Electron Microscopy (HRTEM) images and Selected Area Electron Diffraction (SAED) images of the samples. As can be seen from the figure, the material has a large number of pores, which indicates that C @ NiFe₂O₄The composite material has rich porous structure, increases active sites for the oxygen reduction process and improves the electrocatalytic performance.

FIG. 3 is C @ NiFe₂O₄An XPS spectrum full spectrum (a), a C1s spectrum (b), an O1 s spectrum (C), an Fe2p spectrum (d) and an Ni 2p spectrum (e) of the sample. As can be seen from the figure, the main existence states of the carbon atoms obtained by the peak-splitting fitting of C1s include: c ═ C (284.8eV), C — N (285.7eV), -COOH (289.3 eV). The O spectrum has an absorption peak representing that C ═ O at 532.25eV, so that C @ NiFe can be seen₂O₄Reactive functional groups are present on the nanofibers. The N1s spectra were fitted to four characteristic peaks corresponding to pyridine nitrogen, pyrrole nitrogen, graphite nitrogen and nitrogen oxide at bond energies 398.4, 400.2, 401.4 and 404eV, respectively. In the graph (d), 712.2eV and 714.5eV correspond to Fe2p_3/2The peaks at 724.5eV and 727.6eV represent Fe2p_1/2The above results illustrate C @ NiFe₂O₄Fe in composite materials³⁺Is present. In FIG. (e), represents Ni ²⁺2p of_3/2And 2p_1/2The electron binding energies of the characteristic peaks of the orbitals are 855.52eV and 872.92eV, respectively. From the above results, it was confirmed that C @ NiFe₂O₄The presence of a composite material.

FIG. 4 is C @ NiFe₂O₄Raman of samplesA spectrogram. To further determine the type of carbon layer, C @ NiFe₂O₄Nanofiber composite D/G tape Strength (1330.13/1589.24 cm)^-1) I of (A)_G/I_DThe value was calculated to be 1.06, indicating that the material was more amorphous carbon and less graphitic carbon. For the oxygen reduction reaction, the higher the graphitization degree, the better the electron conductivity can be given to the sample, but on the other hand, the doping of the hetero atoms and the formation of defect sites are not beneficial, and the electrocatalytic efficiency is affected. Therefore, the proper degree of graphitization is the most important for electrocatalysis.

Application example 1:

this example shows a composite of a nanomaterial C @ NiFe₂O₄As a performance study of the oxygen reduction electrocatalyst.

The invention uses a platinum electrode as a counter electrode, a saturated silver chloride electrode (Ag/AgCl) as a reference electrode and a Pt/C electrode as a working electrode.

The concentration of Nafion added in the preparation process of the catalyst is 5 percent, and the dosage is 15 ul.

The electrode pretreatment in the test process of the invention is to add alpha-Al on a nylon polishing cloth base₂O₃Polishing the rotating disc electrode for 10min in an 8-shaped manner by using electrode polishing powder and a small amount of deionized water, cleaning residual powder on the electrode by using the deionized water, and finally naturally drying to finish the treatment.

The catalyst test solution is prepared by placing 4mg of catalyst powder in a 1ml centrifuge tube, adding 735ul of methanol solution, 235ul of deionized water and 50ul of Nafion solution, respectively, and performing ultrasonic dispersion for 45min to obtain the catalyst ink (ink). Then gradually dripping 28 mu L of ink on the surface of the glassy carbon electrode (the loading amount of the catalyst is 0.25 mgcm)^-2) And carrying out an electrocatalysis performance test after naturally drying.

The electrochemical test method comprises the steps of installing an electrode loaded with a catalyst on a rotating rod, connecting a reference electrode and a counter electrode respectively, opening an electrochemical workstation and a rotating speed box, and controlling voltage by using computer software to scan within a given potential range. The cyclic voltammogram is usually scanned first, and then the linear voltammogram is scanned at a certain rotation speed.

All electrocatalytic performance tests described in the present invention were performed in 0.1M KOH electrolyte, and the experimentally measured potential can be converted to a potential relative to a Reversible Hydrogen Electrode (RHE) by the following equation:

E(RHE)＝E(Ag/AgCl)+0.059*pH+0.2224

the potential values referred to in the present invention are all potentials relative to the reversible hydrogen electrode.

The catalyst of the present invention requires CV activation for 3 cycles before electrochemical testing.

The catalyst is tested at normal temperature, and the influence of large temperature change difference on the performance of the catalyst is prevented.

The Nafion added in the preparation process of the catalyst is produced by Aldrich sigma company, and the concentration is 5%.

The catalyst is absorbed by a pipette gun to be 7ul and dropped on a working electrode, the step is repeated for 3 times after the catalyst is naturally aired, then the working electrode slowly enters 0.1MKOH electrolyte saturated by oxygen, bubbles are prevented from being generated on the working electrode in the step, and the electrolyte is continuously introduced into oxygen in the whole testing process to ensure oxygen saturation.

Cyclic voltammetry and linear cyclic voltammetry tests were performed on the catalyst obtained in this example: the cyclic voltammetry test was carried out using an electrochemical workstation manufactured by Pine of the United states, the test voltage sweep range was-0.9-0.1V, the sweep rate was 50mV/s, and during the test, the cyclic voltammetry test was carried out after 3 cycles of activation with a current density of 50 mV/s. And (3) performing linear cyclic voltammetry test by using a Chenghua electrochemical workstation, wherein the scanning range of the test voltage is-0.9-0.1V, and the scanning speed is 50 mV/s. The current density of the catalyst material under different rotating speeds can be obtained by rotating speed test, the number of transferred electrons can be obtained by utilizing a K-L equation, the test current density is 10mV/s, and the rotating speeds are 400rpm, 625rpm, 900rpm, 1225rpm, 1600rpm and 2025 rpm. The stability and the methanol tolerance are also important indexes of the catalyst performance, the test is also completed on an electrochemical workstation, the stability test voltage is-0.189V, and the test time length is 20000 s; the methanol tolerance test voltage was-0.189V, the test duration was 1000 s, and 2M methanol solution was dropped at 300 s.

FIG. 5 is C @ NiFe₂O₄Catalyst cyclic voltammetry characteristic curve graph (test voltage sweep range: -0.9-0.1V, sweep speed: 50mV/s) at saturation O₂In the electrolyte of (1), C @ NiFe₂O₄Exhibits a clear reduction peak, while at saturation N₂The presence of no reduction peak in the electrolyte of (2) demonstrates that a catalytic redox reaction has occurred.

FIG. 6 is C @ NiFe at different temperatures₂O₄Linear cyclic voltammogram of the catalyst (test voltage range: -0.9-0.1V, scanning speed: 50mV/s), although it was found by comparison that C @ NiFe was observed at a calcination temperature of 1000 ℃₂O₄The potential of (A) is slightly higher than C @ NiFe at the calcining temperature of 950 DEG C₂O₄However, it has a significant disadvantage in current density, and too high a temperature also increases the cost and difficulty of the preparation process. In two aspects, analysis shows that the catalyst C @ NiFe obtained by calcining at 950 ℃ is combined₂O₄Has the optimal comprehensive benefits.

FIG. 7 is a C @ NiFe study of the effect of different metal ratios on catalytic performance₂O₄At O₂LSV profile in saturated 0.1M KOH (sweep range-0.9-0.1V, sweep rate 10mv/s), Fe and Ni molar ratios 1: 0. 4: 1. 1: 1. 1: 8. 1: 16. 0: 1, catalyst C @ NiFe at a molar ratio of 1:8₂O₄Has excellent performance, the initial potential and the half-slope potential of the material are respectively 0.9V and 0.8V and are slightly lower than Pt/C, but the material has a greater limiting current density of 5.8mAcm than Pt/C^-2。

FIG. 8 is C @ NiFe₂O₄LSV diagram of the nanometer material and the blank without adding ferronickel supermolecular framework system (scanning range is-0.9-0.1V, scanning speed is 10 mv/s). Compared with the blank sample, when the iron-nickel bimetallic polyphenol network catalyst is added, the ORR activity of the absorbent cotton-based carbon material is greatly improved, and the initial performance is improvedThe potential is positively moved from 0.75V to 0.9V, the reason of the performance difference is mainly related to the change of the element contained in the nanofiber and the structure brought by the pretreatment process, the number of active sites in the carbonized material is reduced due to the MPN deficiency, and the electrochemical performance is further reduced, and the evidence proves that the nickel-iron supermolecular framework structure is a very effective ORR catalytic active center.

FIG. 9 shows the catalyst C @ NiFe at different speeds (400rmp, 625rmp, 900rmp, 1225rmp, 1600rmp, 2025rmp)₂O₄The LSV curve (scan speed: 10mV/s) shows that the current density also shows a tendency to increase gradually with increasing rotation speed, mainly because the increase in rotation speed effectively shortens the diffusion layer of the oxygen reduction reaction. A series of oxygen reduction curves of the catalyst show a better diffusion-limiting current platform, which means that the catalytic active sites of the catalyst are distributed more uniformly, and the speed of the oxygen reduction process is improved.

FIG. 10 is C @ NiFe₂O₄The linear fit is approximately parallel over the entire scanning potential range, i.e., close to the first order reaction kinetics for dissolved oxygen concentrations. Furthermore, the average number of electron transfers at each voltage during the reaction was calculated to be about 3.5 (inset in FIGS. 3-10. d) based on the slope of the K-L equation, indicating that C @ NiFe₂O₄The-950 sample tended to be 4e^-Reaction pathway.

FIG. 11 is a chronoamperometry test of C @ NiFe₂O₄And Pt/C, the initial current density of the Pt/C catalyst is significantly lost by 24% after testing for 20000s, while C @ NiFe₂O₄The catalyst was reduced by only 18%, indicating that the catalyst has better stability than the commercial Pt/C catalyst.

FIG. 12 is C @ NiFe₂O₄And an i-t curve run after addition of commercial 20% Pt/C catalyst to methanol, C @ NiFe was determined by adding 2M methanol to 0.1M KOH electrolyte at 300s₂O₄And methanol resistance of commercial 20% Pt/C catalyst, C @ NiFe was observed₂O₄Has no obvious change in the limiting current density, and the current of Pt/C is obviously reducedThis is due to the oxidation reaction occurring on the Pt/C catalyst surface with the addition of methanol to generate a mixed current, which indicates that C @ NiFe₂O₄Has excellent methanol tolerance.

FIG. 13 is a linear cyclic voltammetry curve (test voltage range: -0.9V-0.1V, scanning speed: 50mV/s) comparing the final catalyst with the procatalyst when the synthesis conditions were changed to water bath oscillation, and it was found by comparison that the ultrasonic synthesis mode apparently has stronger performance of the protoxide.

FIG. 14 is an SEM image of a catalyst synthesized by changing the high-temperature treatment procedure or the synthesis method while keeping other conditions unchanged. FIG. 14 (a) is a graphical representation of the morphology of the catalyst synthesized with water bath shaking; FIG. 14 (b) is a graph of the morphology of the catalyst produced after changing the high temperature treatment program. As can be seen from the figure, the two materials only show a fiber rod-shaped structure similar to a cellulose substrate, but a spiral structure is hardly seen, which obviously loses the physicochemical properties of the structure, such as high specific surface area, high specific modulus, high conductivity and the like, and the spiral nano carbon fiber with a special structure has a quantum size effect, a small size effect and a surface effect, and has an important effect on enhancing the electrode conductivity and accelerating the mass transfer rate. Therefore, the catalytic performance must be affected by changing the existing conditions.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The spiral nickel-iron supermolecular network framework nano composite oxygen reduction material is characterized in that: the active substance is C @ NiFe₂O₄。

2. A method for preparing the helical nickel-iron supermolecular network framework nanocomposite material according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:

(1) weighing a certain amount of directly bought cellulose, putting the directly bought cellulose into a conical flask filled with deionized water, then adjusting the pH value of a solution system by using a buffer acid solution 2M HCl solution, sealing the conical flask by using a preservative film, putting the conical flask into a water bath oscillator for oscillation so as to achieve the purpose of opening a cellulose tightening system, and washing the conical flask for later use;

(2) respectively and fully dissolving ferric nitrate nonahydrate and nickel nitrate hexahydrate in deionized water, pouring into cellulose, stirring for 10min, pouring into a plant polyphenol solution, fully mixing, performing ultrasonic treatment to uniformly disperse the solution in the pretreated cellulose, washing with water after ultrasonic treatment, and drying;

(3) and (3) placing the product obtained in the step (2) in a ark, performing high-temperature treatment in a pure argon atmosphere, and cooling to obtain the spiral ferronickel supermolecular network framework nano composite material for the proton membrane fuel cell.

3. The method for preparing helical nickel-iron supramolecular network framework nanocomposites according to claim 2, characterized in that: the pH value of the solution adjusting system in the step (1) is specifically 1.0-2.0.

4. The method for preparing helical nickel-iron supramolecular network framework nanocomposites according to claim 2, characterized in that: in the step (2), the mass ratio of the ferric nitrate nonahydrate to the nickel nitrate hexahydrate to the cellulose is 1: 6: 1.5.

5. the method for preparing helical nickel-iron supramolecular network framework nanocomposites according to claim 2, characterized in that: in the step (2), the ultrasound is specifically to control the ultrasound output power to be about 200W and the temperature to be (40 +/-1) DEG C.

6. The method for preparing helical nickel-iron supramolecular network framework nanocomposites according to claim 2, characterized in that: and (3) the ultrasonic reaction time in the step (2) is 60 min.

7. The method for preparing helical nickel-iron supramolecular network framework nanocomposites according to claim 2, characterized in that: the adding amount of the plant polyphenol solution in the step (2) is 10 mg/mL.

8. The method for preparing helical nickel-iron supramolecular network framework nanocomposites according to claim 2, characterized in that: and (3) drying in an oven at the temperature of 80 ℃ for 12 hours in the step (2).

9. The method for preparing helical nickel-iron supramolecular network framework nanocomposites according to claim 2, characterized in that: the high-temperature treatment temperature in the step (3) is 950 ℃, and the reaction time is 3 h.

10. Use of the helical nickel-iron supramolecular network framework nanocomposite material as claimed in claim 1 in the field of fuel cells.