A preparation method of a cobalt-iron-doped Bi2O3 composite graphene oxide OER catalyst

Abstract

The present application belongs to the technical field of electrochemical catalysis, and proposes a preparation method of a Co-Fe doped Bi2O3 composite graphene oxide OER catalyst. The preparation method utilizes Co-Fe doped Bi2O3 nanowires and graphene oxide with a large surface area to form a non-noble metal-based OER catalyst with a large number of close heterostructures. The non-noble metal-based OER catalyst can promote the electron transfer between cobalt, iron and oxygen elements, improve the electrode reaction kinetics rate in the OER process, and thus has low OER overpotential and Tafel slope and excellent stability. The present application improves the performance gap between existing non-noble metal-based OER catalysts and noble metal-based OER catalysts through the modification method of constructing heterostructures.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis technology, and particularly relates to a method for preparing an OER catalyst of cobalt iron doped Bi2O3 composite graphene oxide. Background Technology

[0002] Hydrogen has a high calorific value and its combustion products are pollution-free, making it an important fuel for solving energy problems. Hydrogen production is a crucial foundation of the hydrogen industry chain, and clean and efficient hydrogen production is key to the green utilization of hydrogen energy. By combining with green power generation technologies, water electrolysis can achieve completely carbon-free hydrogen production and is considered one of the most promising methods. In principle, water electrolysis involves two half-reactions. The oxygen evolution reaction (OER) at the anolyte, due to its involvement in the adsorption and desorption of numerous reaction intermediates and the four electron transfer steps involved in the overall reaction, is considered the main rate-limiting step in water electrolysis. However, the high cost of OER catalysts and the relatively low hydrogen production efficiency limit the further development of water electrolysis for hydrogen production.

[0003] Based on the elements they contain, OER catalysts are mainly classified into noble metal-based catalysts and non-noble metal-based catalysts. Currently, commercially available OER catalysts are primarily noble metal-based, such as iridium dioxide and ruthenium dioxide oxides. This is because noble metal-based catalysts generally possess favorable electronic structures, moderate adsorption energies for reaction intermediates, and very small reaction barriers during intermediate adsorption, thus exhibiting high catalytic efficiency in OER reactions. However, due to the low abundance and limited reserves of noble metals, noble metal-based catalysts are generally expensive, hindering large-scale applications in water electrolysis for hydrogen production. Therefore, developing efficient, inexpensive, and stable non-noble metal-based OER catalysts is of great significance.

[0004] Chinese patent application CN117966198A discloses a novel metal-carbon-nitrogen composite OER catalyst and its preparation method. By growing cobalt oxide particles on the surface of Fe-C3N4, a non-noble metal-based OER catalyst with low overpotential is constructed. OER performance tests show that it achieves this at 10 mA cm⁻¹. -2 The catalyst exhibits a relatively low OER overpotential of only 361 mV at a given current density. Furthermore, it demonstrates good stability, with the overpotential increasing by only 6 mV after 1000 cyclic voltammetry tests. However, its OER performance still lags behind that of noble metal catalysts. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a method for preparing a cobalt-iron-doped Bi₂O₃ composite graphene oxide OER catalyst. This method utilizes cobalt-iron-doped Bi₂O₃ nanowires combined with graphene oxide, which has a large surface area, to form a non-noble metal-based OER catalyst with a large number of closely packed heterostructures. This non-noble metal-based OER catalyst can promote electron transfer between cobalt, iron, and oxygen, improving the electrode reaction kinetics rate in the OER process. Therefore, it not only exhibits low OER overpotential and Tafel slope but also excellent stability. This invention aims to improve the performance gap between existing non-noble metal-based OER catalysts and noble metal-based OER catalysts by constructing a heterostructure modification method.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a cobalt-iron doped Bi₂O₃ composite graphene oxide OER catalyst includes the following steps:

[0008] Step S1: Add phosphomolybdic acid (H3[P(Mo3O)) to the solution. 10 )4) Dissolved in deionized water, cobalt nitrate hexahydrate (Co(NO3)2·6H2O), ferric nitrate nonahydrate (Fe(NO3)3·9H2O) and bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) were added and stirred to obtain metal precursor solution A;

[0009] Step S2: Stir the metal precursor solution A and 1-octadecene evenly, and then add oleylamine to obtain the reaction precursor solution B;

[0010] Step S3: Perform a hydrothermal reaction on the precursor solution B, and centrifuge and wash the solid product to obtain cobalt-iron doped nanowires CoFe-Bi2O3-PMA;

[0011] Step S4: Disperse CoFe-Bi2O3-PMA in cyclohexane to form a nanowire dispersion;

[0012] Step S5: Mix and stir the nanowire dispersion with the deionized water dispersion of graphene oxide to obtain the reaction precursor solution C;

[0013] Step S6: Perform a hydrothermal reaction on the precursor solution C, and centrifuge and wash the solid product to obtain a non-noble metal-based OER catalyst based on cobalt-iron doped Bi2O3 nanowire composite graphene oxide.

[0014] Preferably, the stirring in step S1 is performed using magnetic stirring or mechanical stirring.

[0015] Preferably, the hydrothermal reaction in step S3 is carried out in a forced-air drying oven at a reaction temperature of 180°C for 8 hours.

[0016] Preferably, in step S3, the solvent used for centrifugal washing is cyclohexane and anhydrous ethanol, the centrifugation rate is 10,000 rpm, the centrifugation time is 3 min, and the number of centrifugal washing cycles is 3.

[0017] Preferably, step S4 specifically includes: dispersing CoFe-Bi2O3-PMA in 3.5 ml of cyclohexane to form a concentration of 15 mg / ml. -1 Nanowire dispersion.

[0018] Preferably, in step S5, the nanowire dispersion is the same as the graphene oxide deionized water dispersion, and the stirring is performed using magnetic stirring or mechanical stirring.

[0019] Preferably, the hydrothermal reaction in step S6 is carried out in a forced-air drying oven at a reaction temperature of 120°C for 2 hours.

[0020] Preferably, in step S1, the mass of phosphomolybdic acid is 0.8g, the volume of deionized water is 16ml, and the masses of cobalt nitrate hexahydrate, ferric nitrate nonahydrate, and bismuth nitrate pentahydrate are 0.12g, 0.03g, and 0.05g, respectively.

[0021] Preferably, in step S2, the volume of 1-octadecene is 10 ml, the stirring time is 10 min, and the volume of oleylamine is 6 ml.

[0022] Preferably, in step S6, the solvent used for centrifugal washing is cyclohexane and anhydrous ethanol, the centrifugation rate is 10,000 rpm, the centrifugation time is 3 min, and the number of centrifugal washing cycles is 3.

[0023] Compared with existing technologies, the present invention has the following advantages:

[0024] 1. This invention proposes a method for preparing a cobalt-iron-doped Bi₂O₃ composite graphene oxide OER catalyst. This method utilizes a two-stage hydrothermal process to obtain a non-noble metal-based OER catalyst composed of cobalt-iron-doped Bi₂O₃ nanowires and graphene oxide. The non-noble metal-based OER catalyst exhibits excellent OER catalytic activity, reaching 10 mA / cm². -2 The required current density is only 334mV overpotential, corresponding to a Tafel slope of 68mV dec. -1 Furthermore, stability tests showed that the non-precious metal-based OER catalyst exhibited good stability.

[0025] 2. The non-precious metal-based OER catalyst prepared by this invention has a compact heterostructure, which promotes electron transfer between cobalt, iron, and oxygen elements and enhances the synergistic effect between elements. It provides a reference for improving the performance of non-precious metal-based OER catalysts and narrowing the performance gap with precious metal-based catalysts by constructing heterostructure modification methods, and has good application prospects. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly introduced below. The features and advantages of the present invention can be more clearly understood by referring to the accompanying drawings. The accompanying drawings are schematic and should not be construed as limiting the present invention in any way. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the preparation method of the OER catalyst of cobalt-iron doped Bi2O3 composite graphene oxide according to the present invention.

[0028] Figure 2 This is a schematic diagram illustrating the synthesis of cobalt-iron doped Bi2O3 nanowire composite graphene oxide samples prepared in Examples 1-4.

[0029] Figure 3 The images show (a) X-ray diffraction pattern, (b) transmission electron microscopy image, and (c) surface distribution diagrams of phosphorus, oxygen, bismuth, cobalt, and iron in CoFe-Bi2O3-PMA.

[0030] Figure 4 It is CoFe-Bi2O3-PMA and CoFe-Bi2O3-PMA / Go prepared in Example 1. 0.01 Infrared spectrum of the composite sample.

[0031] Figure 5 It is CoFe-Bi2O3-PMA and CoFe-Bi2O3-PMA / Go prepared in Example 1. 0.01 Photoelectron spectra of the composite samples. High-resolution photoelectron spectra of (a) C 1s, (b) O 1s, (c) Co 2p and (d) Fe 2p.

[0032] Figure 6 The images show the OER catalytic performance of composite samples with different graphene oxide concentrations prepared in Examples 1-4 in 1M KOH. (a) Linear sweep voltammogram, (b) Electrochemical impedance spectroscopy, (c) Tafel slope plot, (d) Double layer capacitance plot.

[0033] Figure 7It is the CoFe-Bi2O3-PMA / Go prepared in Example 1 0.01 Stability test diagram of composite sample. Detailed Implementation

[0034] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0036] Example 1

[0037] The concentration of graphene oxide prepared was 0.01 mg / ml. -1 Cobalt-iron doped Bi₂O₃ nanowires composite graphene oxide CoFe-Bi₂O₃-PMA / Go 0.01 Composite sample:

[0038] Step 1: Take 0.8g of phosphomolybdic acid, dissolve it in 16ml of deionized water in a 40ml reaction vessel, then add 0.12g of Co(NO3)2·6H2O, 0.03g of Fe(NO3)3·9H2O and 0.05g of Bi(NO3)3·5H2O, and stir vigorously to obtain a uniformly dispersed metal precursor solution A.

[0039] Step 2: Add 10 ml of 1-octadecene to the metal precursor solution, stir magnetically for 10 min, then add 6 ml of oleylamine to obtain reaction precursor solution B. After sealing the reaction vessel, place it in a forced-air drying oven and perform a hydrothermal reaction at a reaction temperature of 180℃ for 8 hours.

[0040] Step 3: The solid product obtained from the reaction was washed three times by centrifugation with cyclohexane and anhydrous ethanol to obtain a clean cobalt-iron doped nanowire sample, CoFe-Bi₂O₃-PMA. The centrifugation rate was 10,000 rpm, and the centrifugation time was 3 minutes. The CoFe-Bi₂O₃-PMA was dispersed in cyclohexane solvent, and the concentration of the dispersion was controlled to be approximately 0.15 mg / mL. -1 .

[0041] Step 4: Add 3.5 ml of nanowire dispersion to a 10 ml reaction vessel, then add 3.5 ml of 0.01 mg / ml solution. -1 The deionized water dispersion of graphene oxide was stirred for 30 minutes to obtain a homogeneous reaction precursor solution C.

[0042] Step 5: After sealing the reactor, place it in a forced-air drying oven and perform a hydrothermal reaction at a reaction temperature of 120°C for 2 hours.

[0043] Step Six: The solid product obtained from the reaction was washed three times by centrifugation using cyclohexane and anhydrous ethanol at a speed of 10,000 rpm for 3 minutes, finally yielding clean cobalt-iron doped Bi₂O₃ nanowire composite graphene CoFe-Bi₂O₃-PMA / Go. 0.01 Composite sample.

[0044] Example 2

[0045] The concentration of graphene oxide prepared was 0.05 mg / ml. -1 Cobalt-iron doped Bi₂O₃ nanowires composite graphene oxide CoFe-Bi₂O₃-PMA / Go 0.05 Composite sample:

[0046] Step 1: Take 0.8g of phosphomolybdic acid, dissolve it in 16ml of deionized water in a 40ml reaction vessel, then add 0.12g of Co(NO3)2·6H2O, 0.03g of Fe(NO3)3·9H2O and 0.05g of Bi(NO3)3·5H2O, and stir vigorously to obtain a uniformly dispersed metal precursor solution A.

[0047] Step 2: Add 10 ml of 1-octadecene to the metal precursor solution A, stir magnetically for about 10 minutes, then add 6 ml of oleylamine to obtain the reaction precursor solution B. After sealing the reaction vessel, place it in a forced-air drying oven and perform a hydrothermal reaction at a reaction temperature of 180°C for 8 hours.

[0048] Step 3: The solid product obtained from the reaction was washed three times by centrifugation with cyclohexane and anhydrous ethanol to obtain a clean cobalt-iron doped nanowire sample, CoFe-Bi₂O₃-PMA. The centrifugation rate was 10,000 rpm, and the centrifugation time was 3 minutes. The CoFe-Bi₂O₃-PMA was dispersed in cyclohexane solvent, and the concentration of the dispersion was controlled to be approximately 0.15 mg / mL. -1 .

[0049] Step 4: Add 3.5 ml of nanowire dispersion to a 10 ml reaction vessel, then add 3.5 ml of 0.05 mg / ml solution. -1 The deionized water dispersion of graphene oxide was stirred for 30 minutes to obtain a homogeneous reaction precursor solution C.

[0050] Step 5: After sealing the reactor, place it in a forced-air drying oven and perform a hydrothermal reaction at a reaction temperature of 120°C for 2 hours.

[0051] Step Six: The solid product obtained from the reaction was washed three times by centrifugation using cyclohexane and anhydrous ethanol at a speed of 10,000 rpm for 3 minutes, finally yielding clean cobalt-iron doped Bi₂O₃ nanowire composite graphene CoFe-Bi₂O₃-PMA / Go. 0.05 Composite sample.

[0052] Example 3

[0053] The concentration of graphene oxide prepared was 0.15 mg / ml. -1 Cobalt-iron doped Bi₂O₃ nanowires composite graphene oxide CoFe-Bi₂O₃-PMA / Go 0.15 Composite sample:

[0054] Step 1: Take 0.8g of phosphomolybdic acid, dissolve it in 16ml of deionized water in a 40ml reaction vessel, then add 0.12g of Co(NO3)2·6H2O, 0.03g of Fe(NO3)3·9H2O and 0.05g of Bi(NO3)3·5H2O, and stir vigorously to obtain a uniformly dispersed metal precursor solution A.

[0055] Step 2: Add 10 ml of 1-octadecene to the metal precursor solution A, stir magnetically for about 10 minutes, then add 6 ml of oleylamine to obtain the reaction precursor solution B. After sealing the reaction vessel, place it in a forced-air drying oven and perform a hydrothermal reaction at a reaction temperature of 180°C for 8 hours.

[0056] Step 3: The solid product obtained from the reaction was washed three times by centrifugation with cyclohexane and anhydrous ethanol to obtain a clean cobalt-iron doped nanowire sample, CoFe-Bi₂O₃-PMA. The centrifugation rate was 10,000 rpm, and the centrifugation time was 3 minutes. The CoFe-Bi₂O₃-PMA was dispersed in cyclohexane solvent, and the concentration of the dispersion was controlled to be approximately 0.15 mg / mL. -1 .

[0057] Step 4: Add 3.5 ml of nanowire dispersion to a 10 ml reaction vessel, then add 3.5 ml of 0.15 mg / ml solution. -1 The deionized water dispersion of graphene oxide was stirred for 30 minutes to obtain a homogeneous reaction precursor solution C.

[0058] Step 5: After sealing the reactor, place it in a forced-air drying oven and perform a hydrothermal reaction at a reaction temperature of 120°C for 2 hours.

[0059] Step Six: The solid product obtained from the reaction was washed three times by centrifugation using cyclohexane and anhydrous ethanol at a speed of 10,000 rpm for 3 minutes, finally yielding clean cobalt-iron doped Bi₂O₃ nanowire composite graphene CoFe-Bi₂O₃-PMA / Go. 0.15 Composite sample.

[0060] Example 4

[0061] The concentration of graphene oxide prepared was 0.25 mg / ml. -1 Cobalt-iron doped Bi₂O₃ nanowires composite graphene oxide CoFe-Bi₂O₃-PMA / Go 0.25 Composite sample:

[0062] Step 1: Take 0.8g of phosphomolybdic acid, dissolve it in 16ml of deionized water in a 40ml reaction vessel, then add 0.12g of Co(NO3)2·6H2O, 0.03g of Fe(NO3)3·9H2O and 0.05g of Bi(NO3)3·5H2O, and stir vigorously to obtain a uniformly dispersed metal precursor solution A.

[0063] Step 2: Add 10 ml of 1-octadecene to the metal precursor solution A, stir magnetically for about 10 minutes, then add 6 ml of oleylamine to obtain the reaction precursor solution B. After sealing the reaction vessel, place it in a forced-air drying oven and perform a hydrothermal reaction at a reaction temperature of 180°C for 8 hours.

[0064] Step 3: The solid product obtained from the reaction was washed three times by centrifugation with cyclohexane and anhydrous ethanol to obtain a clean cobalt-iron doped nanowire sample, CoFe-Bi₂O₃-PMA. The centrifugation rate was 10,000 rpm, and the centrifugation time was 3 minutes. The CoFe-Bi₂O₃-PMA was dispersed in cyclohexane solvent, and the concentration of the dispersion was controlled to be approximately 0.15 mg / mL. -1 .

[0065] Step 4: Add 3.5 ml of nanowire dispersion to a 10 ml reaction vessel, then add 3.5 ml of 0.25 mg / ml solution. -1 The deionized water dispersion of graphene oxide was stirred for 30 minutes to obtain a homogeneous reaction precursor solution C.

[0066] Step 5: After sealing the reactor, place it in a forced-air drying oven and perform a hydrothermal reaction at a reaction temperature of 120°C for 2 hours.

[0067] Step Six: The solid product obtained from the reaction was washed three times by centrifugation using cyclohexane and anhydrous ethanol at a speed of 10,000 rpm for 3 minutes, finally yielding clean cobalt-iron doped Bi₂O₃ nanowire composite graphene CoFe-Bi₂O₃-PMA / Go. 0.25 Composite sample.

[0068] Figure 1 This is a flowchart of the preparation method of the OER catalyst of cobalt-iron doped Bi2O3 composite graphene oxide according to the present invention. Figure 2 The diagram illustrates the synthesis of the cobalt-iron doped Bi₂O₃ nanowire composite graphene oxide samples prepared in Examples 1-4. Cobalt-iron doped Bi₂O₃ nanowires were first prepared via a secondary hydrothermal method, and then a series of cobalt-iron doped Bi₂O₃ nanowire composite graphene oxide samples were prepared by adjusting the concentration of the graphene oxide dispersion. The X-ray diffraction pattern of the prepared cobalt-iron doped Bi₂O₃ nanowire CoFe-Bi₂O₃-PMA samples is shown below. Figure 3 As shown, the presence of diffraction characteristic peaks corresponding to Bi₂O₃ indicates the presence of Bi₂O₃. Transmission electron microscopy images and elemental distribution maps of phosphorus, oxygen, bismuth, cobalt, and iron demonstrate that the cobalt-iron doped nanowires have an extremely high aspect ratio, and that cobalt and iron elements are uniformly distributed on the nanowire surface.

[0069] Figure 4 It is CoFe-Bi2O3-PMA and CoFe-Bi2O3-PMA / Go prepared in Example 1. 0.01 The infrared spectra show that phosphomolybdic acid clusters are present in both the cobalt-iron doped sample and the composite sample, and the secondary hydrothermal preparation process did not affect the Keggin configuration of phosphomolybdic acid.

[0070] Figure 5 This refers to CoFe-Bi2O3-PMA and the CoFe-Bi2O3-PMA / Go prepared in Example 1. 0.01 The photoelectron spectroscopy (PES) spectra are shown. The presence of C-C and CO bonds in the C 1s spectrum indicates the presence of graphene oxide in the composite sample. High-resolution PES spectra of O 1s, Co 2p, and Fe 2p show a significant shift in the binding energy peaks after the composite graphene oxide is incorporated, indicating a strong interfacial interaction between graphene oxide and CoFe-Bi2O3-PMA. Furthermore, the shift of the binding energy peaks for the multiple valence states of cobalt, iron, and oxygen towards higher binding energies suggests that electrons in the composite sample have transferred from CoFe-Bi2O3-PMA to graphene oxide and reached thermodynamic equilibrium, indicating a close heterostructure between the two.

[0071] Figure 6These are OER catalytic performance graphs of composite samples with different graphene oxide concentrations prepared in Examples 1-4 in 1M KOH. It can be observed that all composite samples exhibit good electrocatalytic performance. (CoFe-Bi2O3-PMA / Go) x (x = 0.01, 0.05, 0.15, 0.25) Samples at a current density of 10 mA / cm² -2 The overpotentials were 334 mV, 344 mV, 345 mV, and 354 mV, respectively, and the OER performance of the composite sample gradually decreased with increasing graphene oxide concentration. Among them, the composite sample CoFe-Bi2O3-PMA / Go prepared in Example 1... 0.01 It has the lowest charge transfer resistance and Tafel slope, and its electric double-layer capacitance is 1.26 mF cm⁻¹. -2 The OER activity of the composite sample was higher than that of other composite samples, indicating that it had the largest electrochemical active area. Combining the electrocatalytic test results and photoelectron spectroscopy analysis results, the enhanced OER activity of the composite sample can be attributed to the optimized electron transfer between CoFe-Bi2O3-PMA and graphene oxide due to its compact heterostructure, which improved the electrode reaction kinetics rate of the composite sample.

[0072] Figure 7 It is the CoFe-Bi2O3-PMA / Go prepared in Example 1 0.01 The stability test graph of the composite sample shows that after 100 minutes of OER testing, the voltage increase of the working electrode at different current densities was 57mV (20mAcm). -2 ) and 87mV (50mAcm -2 This indicates that the composite sample has good stability.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an OER catalyst of cobalt-iron doped Bi₂O₃ composite graphene oxide, characterized in that, Includes the following steps: Step S1: Add phosphomolybdic acid (H3[P(Mo3O)) to the solution. 10 )4) Dissolved in deionized water, cobalt nitrate hexahydrate (Co(NO3)2·6H2O), ferric nitrate nonahydrate (Fe(NO3)3·9H2O) and bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) were added and stirred to obtain metal precursor solution A; Step S2: Stir the metal precursor solution A and 1-octadecene evenly, and then add oleylamine to obtain the reaction precursor solution B; Step S3: Perform a hydrothermal reaction on the precursor solution B, and centrifuge and wash the solid product to obtain cobalt-iron doped nanowires CoFe-Bi2O3-PMA; Step S4: Disperse CoFe-Bi2O3-PMA in cyclohexane to form a nanowire dispersion; Step S5: Mix and stir the nanowire dispersion with the deionized water dispersion of graphene oxide to obtain the reaction precursor solution C; Step S6: Perform a hydrothermal reaction on the precursor solution C, and centrifuge and wash the solid product to obtain a non-noble metal-based OER catalyst based on cobalt-iron doped Bi2O3 nanowire composite graphene oxide.

2. The preparation method according to claim 1, characterized in that, In step S1, stirring is performed using magnetic stirring or mechanical stirring.

3. The preparation method according to claim 2, characterized in that, The hydrothermal reaction in step S3 is carried out in a forced-air drying oven at a temperature of 180°C for 8 hours.

4. The preparation method according to claim 3, characterized in that, In step S3, the solvents used for centrifugal washing are cyclohexane and anhydrous ethanol, the centrifugation rate is 10,000 rpm, the centrifugation time is 3 min, and the number of centrifugal washing cycles is 3.

5. The preparation method according to claim 4, characterized in that, Step S4 specifically includes: dispersing CoFe-Bi2O3-PMA in 3.5 ml of cyclohexane to form a concentration of 15 mg / ml. -1 Nanowire dispersion.

6. The preparation method according to claim 5, characterized in that, In step S5, the nanowire dispersion is the same as the graphene oxide deionized water dispersion, and the stirring is performed using magnetic stirring or mechanical stirring.

7. The preparation method according to claim 6, characterized in that, The hydrothermal reaction in step S6 is carried out in a forced-air drying oven at a temperature of 120°C for 2 hours.

8. The preparation method according to claim 7, characterized in that, In step S1, the mass of phosphomolybdic acid is 0.8g, the volume of deionized water is 16ml, and the masses of cobalt nitrate hexahydrate, ferric nitrate nonahydrate, and bismuth nitrate pentahydrate are 0.12g, 0.03g, and 0.05g, respectively.

9. The preparation method according to claim 8, characterized in that, In step S2, the volume of 1-octadecene is 10 ml, the stirring time is 10 min, and the volume of oleylamine is 6 ml.

10. The preparation method according to claim 9, characterized in that, In step S6, the solvents used for centrifugal washing are cyclohexane and anhydrous ethanol, the centrifugation rate is 10,000 rpm, the centrifugation time is 3 min, and the number of centrifugal washing cycles is 3.

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