CN113394414A - Construction of flower-core type S-doped manganese-copper electrocatalyst based on metal polyphenol modified sodium alginate/nano-cellulose composite aerogel - Google Patents
Construction of flower-core type S-doped manganese-copper electrocatalyst based on metal polyphenol modified sodium alginate/nano-cellulose composite aerogel Download PDFInfo
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Abstract
The invention discloses a method for constructing a flower core type S-doped manganese copper electrocatalyst based on metal polyphenol modified sodium alginate/nano cellulose composite aerogel, wherein the manganese copper electrocatalyst is C @ MnOCu7.2S4-TA. The nanocellulose prepared by the acidolysis method introduces a large amount of sulfur doping, the three-dimensional network structure of the sodium alginate/nanofiber composite aerogel has a large amount of pores as a porous carbon template, and the contact area with a precursor metal solution is increased, so that the tannin-modified metal polyphenol network is uniformly distributed in the sodium alginate/nanofiber composite aerogel. The nano composite material synthesized after high-temperature carbonization presents a pistil shape. The invention is used for solving the problems of low reversibility of cathode oxygen reduction reaction and exchange current density of the existing fuel cell catalystAnd the obtained oxygen reduction catalyst has the advantages of high potential, excellent limiting current, high methanol tolerance and the like.
Description
Technical Field
The invention belongs to the technical field of proton membrane fuel cell catalysts, and particularly relates to a method for constructing a core type S-doped manganese copper electrocatalyst based on metal polyphenol modified sodium alginate/nano cellulose composite aerogel.
Background
At present, the proton membrane fuel cell (PEMFC) is faced with the problems of high cost, short service life and the like, so that the wide application cannot be realized, and the further development of the PEMFC in the industrialization process is limited. At present, a main approach for improving the performance of PEMFC and reducing the cost of the catalyst is to reduce the amount of noble metal Pt used by changing the carrier, preparing an alloy catalyst, etc. from the viewpoint of intrinsic activity of the catalyst, so as to improve the activity and stability of the catalyst.
The source of nanocellulose is wide, i.e. because of the large number of hydroxyl groups contained therein, stable positive or negative charges can be introduced by cationization or carboxymethylation processes. The nano-cellulose prepared from the biomass material has the advantages of both biomass and nano-materials, and becomes a research hotspot, the nano-cellulose aerogel has rich pores and a three-dimensional network structure, and rich chemical functional groups are beneficial to functional modification, and the nano-cellulose aerogel is a good carrier for a catalyst. The nano-fiber crystal CNC solution prepared by the sulfuric acid hydrolysis method contains a large amount of sulfuric acid groups, the length and the diameter are both in a nano-scale range, the length-diameter ratio is low, and the rigidity of the prepared aerogel is insufficient. Tannin (TA), also known as tannin and boots, is a natural product mainly derived from pomegranate, tea, sumac leaves, witch hazel and other plants, belongs to a typical glucose acyl compound, and has a chemical formula of C76H52O36Because TA has a rich phenolic hydroxyl structure, the TA has unique chemical properties, two adjacent phenolic hydroxyl groups of the TA can form a stable five-membered ring chelate with metal ions, and the rest phenolic hydroxyl groups do not participate in the reaction, but promote the dissociation of the other two phenolic hydroxyl groups, thereby promoting the formation of a complex and also enabling the complex to be more stable.
According to the invention, sodium alginate is used as a support body, sodium alginate/nano-fiber crystal composite aerogel is prepared as a catalyst carrier, a metal polyphenol network is constructed by using tannin, and a litmus S-doped manganese copper electrocatalyst modified by tannin is constructed by using nano-cellulose base composite aerogel. The morphology structure and the composition of the electrocatalytic material are analyzed by characterization methods such as SEM, XRD, EDX and the like, and the oxygen reduction performance of the electrocatalytic material is inspected by means of cyclic voltammetry, chronoamperometry and the like. Electrochemical test studies show that the current density of the catalyst is far higher than that of commercial Pt/C in 0.1M KOH and the potential is equal to 0.1V, meanwhile, the reaction process of ORR in an alkaline medium is 4 electrons, and in addition, the catalyst has better methanol resistance than that of the commercial Pt/C catalyst.
Disclosure of Invention
The invention aims to solve the problems of the existing fuel cell catalyst and overcome the defects of the prior art, and the existing fuel cell catalyst generally faces the problems of single precursor obstacle and synthesis cost; a large amount of sulfur doping is introduced into the nano-cellulose based on sulfuric acid hydrolysis, sodium alginate/nano-fiber composite aerogel is prepared by taking sodium alginate as a support body, a tannin modified metal polyphenol network is uniformly distributed in the sodium alginate/nano-fiber composite aerogel, and a nano-composite material C @ MnOCu synthesized after high-temperature carbonization is adopted7.2S4the-TA presents a pistil shape, and has the advantages of high initial potential, half slope potential, excellent limiting current, good methanol tolerance, strong methanol poisoning resistance and the like when being applied to the oxygen reduction electrocatalyst.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a preparation method for constructing a flower core type S-doped manganese copper electrocatalyst based on metal polyphenol modified sodium alginate/nano cellulose composite aerogel comprises the following steps:
(1) weighing cotton in a three-neck round-bottom flask, adding concentrated sulfuric acid (98%) and deionized water, stirring at constant speed in a water bath, diluting sulfuric acid with deionized water to terminate hydrolysis reaction, standing, and removing supernatant. Centrifuging the lower layer suspension in a high-speed centrifuge (10000 rpm/min, 10 min/time) until milky white liquid appears, and sequentially collecting the milky white liquid to obtain a nanofiber crystal (CNC) solution;
(2) dissolving sodium alginate in deionized water, and magnetically stirring;
(3) mixing and stirring the nano-fiber crystal solution obtained in the step (1) and the sodium alginate solution obtained in the step (2), then pouring the mixture into a plastic mold, and then freeze-drying the mixture to obtain SA/CNC aerogel;
(4) weighing tannic acid and MnSO4·H2O、CuSO4·5H2Dissolving O in deionized water respectively, and mixing the three solutions to obtain a metal polyphenol network precursor solution constructed by tannin;
(5) soaking the SA/CNC aerogel prepared in the step (3) into the precursor solution in the step (4), oscillating in a water bath, washing with ethanol for multiple times, and freeze-drying to obtain an SA/CNC @ MnCu-TA precursor;
(6) placing the SA/CNC @ MnCu-TA precursor obtained in the step (5) in N2Carrying out heat treatment and annealing under the atmosphere to obtain the S-doped manganese copper electrocatalyst C @ MnOCu for the proton membrane fuel cell7.2S4-TA。
In the technical scheme, the solid-to-liquid ratio of the cotton used in the step (1) to concentrated sulfuric acid and deionized water is 3:13:13 (g/ml/ml), the water bath temperature is 45 ℃, and the stirring time is 1.5 hours;
in the technical scheme, the stirring temperature in the step (2) is 25 ℃, and the oscillation time is 2 hours;
in the technical scheme, the volume ratio of the nano-fiber crystal CNC solution to the sodium alginate solution used in the step (3) is 1: 1, stirring at 25 ℃ for 2 hours, freeze-drying at-78 ℃ for 48 hours;
in the technical scheme, the tannic acid and MnSO in the metal polyphenol network precursor solution in the step (4)4·H2O、CuSO4·5H2The solid-liquid ratio of O to deionized water is 1: 3: 3: 30 (g/mol/mol/mL)
In the above technical scheme, the solid-to-liquid ratio of the SA/CNC aerogel to the metal polyphenol network precursor solution in step (5) is 0.2: 30 (g/mL), wherein the water bath temperature is 50 ℃, the oscillation time is 2 hours, the freeze-drying temperature is-78 ℃, and the drying time is 48 hours;
in the above technical solution, the heat treatment and annealing in step (6) are specifically: heating to 320 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 3h, heating to 800 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 1.5h, and naturally cooling to room temperature.
Compared with a commercial Pt/C catalyst, the method for constructing the flower core type S-doped manganese copper electrocatalyst based on the metal polyphenol modified sodium alginate/nano cellulose composite aerogel has the following advantages:
(1) the preparation process has the advantages of simple equipment, simple operation steps, environmental protection, easy control of reaction conditions, water bath oscillation and high-temperature carbonization, and not only shows high initial potential, half-slope potential, excellent limiting current and good methanol tolerance, but also has strong methanol poisoning resistance and the like.
(2) The preparation method comprises the steps of preparing nano-cellulose by a sulfuric acid hydrolysis method, introducing S doping, preparing sodium alginate/nano-fiber composite aerogel by taking sodium alginate as a support body, taking tannic acid as a catalyst carrier, chelating metal ions to form a metal polyphenol network, and enabling a metal precursor solution to be in full contact with the carrier by the unique three-dimensional hole network structure of the sodium alginate/nano-fiber composite aerogel so as to improve metal loading capacity. The 3D porous carbon formed after the high-temperature carbonization of the sodium alginate/nanofiber composite aerogel carrier enables the prepared nanocomposite to have good conductivity, the sulfur-doped copper-manganese oxide nanocomposite is wrapped in staggered network fiber clusters, and a pistil-shaped S-doped manganese-copper electrocatalyst C @ MnOCu is formed7.2S4-TA。
Drawings
FIG. 1 is C @ MnOCu7.2S4XRD pattern of the TA sample at 800 ℃ (scan interval: 5 ° -80 °, step size: 0.02 °, scan rate: 1.5 °/min);
FIG. 2 is sodium alginate/nanocellulose SA/CNC composite aerogel physical diagram (a), scanning electron microscope diagram (b-C) and C @ MnOCu respectively7.2S4-scanning electron micrographs (d-e) of TA nanocomposites;
FIG. 3 is C @ MnOCu7.2S4EDX element of TAScanning the surface;
FIG. 4 is C @ MnOCu7.2S4-raman analysis of TA;
FIG. 5 is C @ MnOCu7.2S4-XPS profile of TA;
FIG. 6 is C @ MnOCu7.2S4-TA nanomaterials in N2And O2CV plot in saturated 0.1M KOH (scan range-0.9-0.1V, scan rate 50 mv/s);
FIG. 7 is C @ MnOCu at different rotational speeds7.2S4LSV plot of TA (rotation speed 400 rmp, 625 rmp, 900 rmp, 1225 rmp, 1600rmp, 2025 rmp, scan rate 10 mV/s);
FIG. 8 is C @ MnOCu7.2S4-a K-L equation curve for TA;
FIG. 9 is C @ MnOCu7.2S4I-t curves run after TA and Pt/C addition of methanol.
Detailed Description
The simple water bath oscillation and high-temperature carbonization preparation process provided by the invention synthesizes C @ MnOCu7.2S4-TA catalyst process, comprising the following steps:
(1) weighing cotton in a three-neck round-bottom flask, adding concentrated sulfuric acid (98%) and deionized water, stirring at constant speed in a water bath, diluting sulfuric acid with deionized water to terminate hydrolysis reaction, standing, and removing supernatant. And centrifuging the lower layer suspension in a high-speed centrifuge (10000 rpm/min, 10 min/time) until milky white liquid appears, and sequentially collecting the milky white liquid to obtain a nanofiber crystal (CNC) solution.
(2) Dissolving sodium alginate in deionized water, and magnetically stirring.
(3) And (3) mixing and stirring the nano-fiber crystal solution obtained in the step (1) and the sodium alginate solution obtained in the step (2), then pouring the mixture into a plastic mold, and then freeze-drying the mixture to obtain the SA/CNC aerogel.
(4) Weighing tannic acid and MnSO4·H2O、CuSO4·5H2Dissolving O in deionized water respectively, and mixing the three solutions to obtain a metal polyphenol network precursor solution constructed by tannin;
(5) soaking the SA/CNC aerogel prepared in the step (3) into the precursor solution in the step (4), oscillating in a water bath, washing with ethanol for multiple times, and freeze-drying to obtain an SA/CNC @ MnCu-TA precursor;
(6) placing the SA/CNC @ MnCu-TA precursor obtained in the step (5) in N2Performing heat treatment in the atmosphere, heating to 320 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 3h, heating to 800 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 1.5h, and naturally cooling to room temperature to obtain the litmus S-doped manganese copper electrocatalyst C @ MnOCu constructed by the nano cellulose-based composite aerogel7.2S4-TA。
The invention relates to C @ MnOCu7.2S4the-TA catalyst is prepared by water bath oscillation and high temperature carbonization.
The invention uses a carbon rod electrode as a counter electrode, a saturated silver chloride electrode (Ag/AgCl) as a reference electrode and a rotating disk electrode for catalyst ink titration as a working electrode.
The concentration of Nafion added in the preparation process of the catalyst is 5wt%, and the dosage is 15 ul.
A catalyst ink (ink) was prepared by dispersing 4 mg of the catalyst of the present invention in 1 mL of a mixed solution (250 uL of deionized water, 735 uL of isopropyl alcohol, and 15uL of a 5wt% Nafion solution) using a scale. Then, 28 uL of ink was gradually added dropwise to the surface of the rotating disk electrode (catalyst loading 0.25 mg cm)-2) And carrying out an electrocatalysis performance test after naturally drying.
All electrocatalytic performance tests described in the present invention were performed in 0.1M KOH (pH = 13.62) electrolyte, and the experimentally measured potential was converted to a potential relative to a Reversible Hydrogen Electrode (RHE) by the following formula:
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 invention will be further illustrated with reference to the following specific examples. In order to further clarify the present invention, preferred embodiments of the present invention are described in connection with the examples which are intended to illustrate various features and advantages of the present invention, but not to limit the scope of the invention which is not defined by the claims. In addition, it should be understood that various changes or modifications can be made by those skilled in the art after reading the disclosure of the present invention, and such equivalents also fall within the scope of the 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 C @ MnOCu7.2S4-method for synthesis of TA catalyst:
(1) 3g of cotton is weighed into a three-neck round-bottom flask, 13mL of concentrated sulfuric acid (98%) and 13mL of deionized water are added, the mixture is stirred at a constant speed for 1.5h in a water bath at 45 ℃, then sulfuric acid is diluted by deionized water to terminate the hydrolysis reaction, and after standing, the supernatant is removed. And centrifuging the lower layer suspension in a high-speed centrifuge (10000 rpm/min, 10 min/time) until milky white liquid appears, and sequentially collecting the milky white liquid to obtain a nanofiber crystal (CNC) solution.
(2) 2g of sodium alginate was dissolved in 100mL of deionized water and magnetically stirred at room temperature for 2 hours.
(3) 100mL of the nanofiber crystal solution and 100mL of the sodium alginate solution were mixed and magnetically stirred at room temperature for 2h, and then poured into a plastic mold, followed by freeze-drying (-78 ℃, 48 h) to obtain SA/CNC aerogel.
(4) Weighing 1g of tannic acid and 3mmol of MnSO4·H2O、3mmol CuSO4·5H2Dissolving O in 10mL of deionized water respectively, and mixing the three solutions to obtain a metal polyphenol network precursor solution constructed by tannin;
(5) soaking 0.2g of SA/CNC aerogel into 30mL of metal precursor mixed solution, oscillating in a water bath at 50 ℃ for 2h, washing with ethanol for multiple times, and freeze-drying (-78 ℃, 48 h) to obtain an SA/CNC @ MnCu-TA precursor;
(6) the precursor of SA/CNC @ MnCu-TA is added in N2Heating to 320 ℃ at a heating rate of 5 ℃/min in the atmosphere, keeping the temperature for 3h, heating to 800 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 1.5h, and naturally cooling to room temperature to obtain the tannin-modified pistil type S-doped manganese copper electrocatalyst C @ MnOCu constructed by the nano cellulose-based composite aerogel7.2S4-TA。
FIG. 1 is C @ MnOCu7.2S4XRD pattern of the TA sample (scanning interval: 5 ° -80 °, scanning rate: 8 °/min). The crystal structure and phase composition of the C-MnCu nanocomposite material at 800 ℃ calcination were analyzed by XRD characterization. From the XRD spectrum, it can be seen that the wide diffraction peak at the 25 ℃ position indicates the existence of amorphous carbon, which indicates that the main existing form of carbon in the carbonized C-MnCu nano composite material is amorphous carbon. A strong diffraction peak was observed simultaneously with respect to Mn +2O (PDF # 07-0230) crystals as compared with a standard card, manganese was mainly present as an oxide, and Cu was also observed7.2S4(PDF # 24-0061) diffraction peak of crystal, which shows that copper in the composite nano material exists mainly in the form of sulfide.
FIG. 2 is sodium alginate/nanocellulose SA/CNC composite aerogel physical diagram (a), scanning electron microscope diagram (b-C) and C @ MnOCu respectively7.2S4-scanning electron micrographs of TA nanocomposites (d-e). According to the figure, in the sodium alginate/nano-cellulose SA/CNC composite aerogel, sodium alginate crosslinks nano-cellulose into aerogel with a stable three-dimensional pore structure, and the aerogel is used as a carrier of a catalyst, so that a metal precursor solution can be fully contacted with the carrier, and the chelating amount of metal is increased. After high-temperature carbonization, the manganese-copper metal is fully wrapped in the sodium alginate/nano-cellulose composite aerogel under the modification of tanninIn the method, S-doped C @ MnOCu with a pistil shape is generated7.2S4-TA nanocomposites.
FIG. 3 is C @ MnOCu7.2S4EDX elemental plane scan of TA. As can be seen from the figure, C @ MnOCu7.2S4Distribution of elements in the TA nanocomposite, it can be seen from the figure that Mn, Cu, O, S and C elements are uniformly distributed on the material. According to EDX analysis report, C @ MnOCu7.2S4The TA nano composite material contains more than 30% of manganese element and copper element and about 10% of S element, which indicates that the metal elements are distributed in the porous carbon more uniformly.
FIG. 4 is C @ MnOCu7.2S4-raman analysis of TA nanocomposites. In the Raman spectrum of the C @ MnOCu7.2S4 nanocomposite, a D peak and a G peak can be observed at 1342cm-1 and 1601 cm-1. D and G bands indicate the presence of graphite defects and graphite carbon in the carbon material, respectively, ID/IGThe overall strength ratio of (A) reflects the degree of graphitization, C @ MnOCu7.2S4-ratio of D peak to G peak intensity of TA nanocomposite (I)D/IG= 1607/1728) is 0.9, indicating that the degree of graphitization of the MnCu nanocomposite calcined at 800 ℃ is higher and therefore the material has good electrical conductivity.
FIG. 5 is C @ MnOCu7.2S4XPS analysis of TA nanocomposites. As can be seen from the figure, the composition of each element on the surface of the material is further confirmed. (a) Is C @ MnOCu7.2S4XPS full spectrum analysis chart of TA nano composite material, which confirms that five elements of C, O, S, Mn and Cu exist on the surface of the material. The C1 s spectrogram has an absorption peak representing C-C at 284.8 eV, which indicates that the carbon matrix of the graphitized carbon with good conductivity is in the composite material. In the high resolution O ls spectrogram, the oxygen-containing functional group C — O appears together with characteristic peaks of the metal oxide, which is consistent with the results of MnO appearing upon XRD analysis. The existence of the metal sulfide is proved by characteristic peaks fitted by the S1S spectrogram. Cu2p fitting spectrum, Cu2p3/2And Cu2p1/2The peak at (A) indicates C @ MnOCu7.2S4Cu element in TA-Cu2+Are present. In thatFour signal peaks are clearly observed in the Mn 2p chromatogram. The assigned MnO electron binding energy was found to be at 643eV by peak fitting, which is consistent with the XRD analysis. The XPS results further demonstrate C @ MnOCu7.2S4Successful synthesis of TA nanocomposites.
Example 2:
this example shows a C @ MnOCu7.2S4-electrochemical performance study of TA nanocomposite catalyst.
Nafion added in the preparation process of the catalyst is produced by Aldrich sigma company, and the concentration is 5 wt%.
The catalyst is absorbed by a pipette gun to be 7 ul 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 0.1M KOH 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 50 mV/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. Linear cyclic voltammetry tests were also performed using the Pine electrochemical workstation, with a test voltage sweep range of-0.9-0.1V and a sweep rate of 50 mV/s. The current density of the catalyst material under different rotating speeds can be obtained through 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 400 rmp, 625 rmp, 900 rmp, 1225 rmp, 1600rmp and 2025 rmp. Methanol tolerance is an important indicator of catalyst performance, and the test is also carried out on an electrochemical workstation, wherein the methanol tolerance test voltage is-0.189V, the test time is 1000 s, and 2 mL of methanol solution is dropped at 250 s.
FIG. 6 is C @ MnOCu7.2S4TA nanocomposite catalyst cyclic voltammetry characteristic curve chart (test voltage sweep range: -0.9-0.1V, sweep speed: 50 mV/s)In the electrolyte solution saturated with nitrogen, we did not detect any significant oxidation peak or reduction peak, but only obtained a quasi-rectangular voltammogram typical of carbon materials with high specific surface area. When in the oxygen saturated electrolyte, there is a significant cathodic oxygen reduction peak at 0.55V, indicating C @ MnOCu7.2S4the-TA nano composite material catalyst has obvious catalytic activity on oxygen reduction reaction.
FIG. 7 is catalyst C @ MnOCu7.2S4Curves of LSV (sweep speed: 10 mV/s) of TA tested in oxygen-saturated 0.1M KOH electrolyte at different spin speed conditions (400 rmp, 625 rmp, 900 rmp, 1225 rmp, 1600rmp, 2025 rmp) show a tendency to increase in current density with increasing spin speed, mainly due to the fact that the increasing spin 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. Although the initial potential and the half-slope potential are different from the conventional platinum-carbon, when the rotation speed is 1600rmp, the limit current of 0.1V can reach-7 j/mA cm-2The C @ MnOCu has been demonstrated over the conventional platinum carbon catalyst7.2S4the-TA nano composite material has wide application prospect as oxygen reduction electrocatalysis.
FIG. 8 is C @ MnOCu7.2S4The slope of the curve remains substantially constant throughout the potential range of the sweep, which means that the oxygen reduction has the same number of transferred electrons at different potentials under the action of the catalyst. According to the RRDE test result, the catalyst C @ MnOCu is calculated and obtained in the potential range of 0.2V to 0.4V7.2S4The ORR electron transfer number (n) of TA is 3.6, which indicates that the catalyst prepared by us catalyzes the reaction by the transfer pathway of 4 electrons in the alkaline electrolyte.
FIG. 9 is C @ MnOCu7.2S4Methanol resistance of TA and commercial 20% Pt/C catalystFigure, Pt/C catalyst was found to exhibit a very significant instantaneous jump in current after 250 s addition of 2 mL of methanol, with a significant drop in ORR current to 0.3 mA cm-2 after recovery, and C @ MnOCu7.2S4The TA catalyst is essentially unreactive and the current effect is minimal, indicating some resistance to methanol.
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 (9)
1. A preparation method for constructing a flower core type S-doped manganese copper electrocatalyst based on metal polyphenol modified sodium alginate/nano cellulose composite aerogel is characterized by comprising the following steps: the preparation method comprises the following steps:
(1) weighing cotton in a three-neck round-bottom flask, adding concentrated sulfuric acid and deionized water, stirring at a constant speed in a water bath kettle, diluting sulfuric acid with deionized water to terminate hydrolysis reaction, standing, removing supernatant, centrifuging suspension in a high-speed centrifuge until milky white liquid appears, and sequentially collecting the milky white liquid to obtain a nanofiber crystal CNC solution;
(2) dissolving sodium alginate in deionized water, and magnetically stirring;
(3) mixing and stirring the nano-fiber crystal CNC solution obtained in the step (1) and the sodium alginate solution obtained in the step (2), then pouring the mixture into a plastic mold, and then carrying out freeze drying to obtain SA/CNC aerogel;
(4) weighing tannic acid and MnSO4·H2O、CuSO4·5H2Dissolving O in three parts of deionized water with the same volume respectively, and mixing the three solutions to obtain a metal polyphenol network precursor solution constructed by tannin;
(5) soaking the SA/CNC aerogel prepared in the step (3) into the precursor solution in the step (4), oscillating in a water bath, washing with ethanol for multiple times, and freeze-drying to obtain an SA/CNC @ MnCu-TA precursor;
(6) placing the SA/CNC @ MnCu-TA precursor obtained in the step (5) in N2And carrying out heat treatment and annealing in the atmosphere to obtain the S-doped manganese-copper electrocatalyst for the proton membrane fuel cell.
2. The method of claim 1, wherein: the solid-liquid ratio of the cotton used in the step (1) to concentrated sulfuric acid and deionized water is 3:13:13 g/ml/ml, the water bath temperature is 45 ℃, and the stirring time is 1.5 hours.
3. The method of claim 1, wherein: the centrifugal speed in the step (1) is 10000rpm/min and 10 min/time.
4. The method of claim 1, wherein: the stirring temperature in the step (2) is 25 ℃, and the stirring time is 2 hours.
5. The method of claim 1, wherein: the volume ratio of the nano-fiber crystal CNC solution to the sodium alginate solution used in the step (3) is 1: 1, the stirring temperature is 25 ℃, the stirring time is 2 hours, the freeze-drying temperature is-78 ℃, and the drying time is 48 hours.
6. The method of claim 1, wherein: step (4) tannic acid and MnSO in the metal polyphenol network precursor solution4·H2O、CuSO4·5H2The solid-liquid ratio of O to deionized water is 1: 3: 3: 30 g/mol/mol/mL.
7. The method of claim 1, wherein: in the step (5), the solid-to-liquid ratio of the SA/CNC aerogel to the metal polyphenol network precursor solution is 0.2: 30 g/mL, the water bath temperature is 50 ℃, the oscillation time is 2 hours, the freeze drying temperature is-78 ℃, and the drying time is 48 hours.
8. The method of claim 1, wherein: the heat treatment and annealing in the step (6) are specifically as follows: heating to 320 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 3h, heating to 800 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 1.5h, and naturally cooling to room temperature.
9. An S-doped manganin electrocatalyst C @ MnOCu prepared by the preparation method according to any one of claims 1 to 77.2S4-TA nanomaterial.
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