Preparation method of OER catalyst of cobalt-iron-doped Bi2O3 composite graphene oxide

Abstract

The invention belongs to the technical field of electrochemical catalysis, and provides a preparation method of a cobalt-iron-doped Bi2O3 composite graphene oxide OER catalyst. According to the preparation method, the non-noble metal-based OER catalyst with a large number of compact heterostructures is formed by compounding cobalt-iron-doped Bi2O3 nanowires and graphene oxide with a large surface area. The non-noble metal-based OER catalyst can promote electron transfer among cobalt, iron and oxygen elements and improve the electrode reaction kinetics rate in the OER process, so that the non-noble metal-based OER catalyst not only has low OER overpotential and Tafel slope, but also has excellent stability. The problem that the performance of an existing non-noble metal-based OER catalyst is different from that of a noble metal-based OER catalyst is solved through a modification means of constructing a heterostructure.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic chemistry, and particularly relates to a preparation method of an OER catalyst of cobalt and iron doped Bi 2 O 3 composite graphene oxide. Background Art

[0002] Hydrogen has a high calorific value of combustion and its combustion products are pollution-free, making it an important fuel for people to solve energy problems. The hydrogen production link is an important basic link in the hydrogen industrial chain, and how to produce hydrogen cleanly and efficiently is the key to the green utilization of hydrogen energy. By combining with green power generation technologies, hydrogen production by electrolyzing water can achieve completely carbon-free hydrogen production and is considered one of the most promising hydrogen production methods. In principle, hydrogen production by electrolyzing water involves two half-reactions. Among them, the anodic oxygen evolution reaction (OER) is considered the main rate-limiting step of the hydrogen production reaction by electrolyzing water because it involves the adsorption and desorption processes of a large number of reaction intermediates and a total of 4 electron transfer steps in the overall reaction. However, the high-cost OER catalysts and low hydrogen production efficiency limit the further development of hydrogen production by electrolyzing water.

[0003] OER catalysts are mainly divided into noble metal-based catalysts and non-noble metal-based catalysts according to the types of elements contained in the catalysts. Currently, commercially available OER catalysts are mainly noble metal-based catalysts, such as noble metal oxides like iridium dioxide and ruthenium dioxide. Because most noble metal-based catalysts have good electronic structures, moderate adsorption energies for reaction intermediates, and only extremely small reaction barriers during the adsorption process of reaction intermediates, they have high catalytic efficiencies in the OER reaction. However, due to the low abundance and small reserves of noble metals, noble metal-based catalysts generally have high prices, which is not conducive to the large-scale application of hydrogen production by electrolyzing water. Therefore, it is of great significance to develop non-noble metal-based OER catalysts with high efficiency, low price, and good stability.

[0004] Chinese patent application with publication number CN117966198A discloses a novel metal-carbon-nitrogen composite OER catalyst and its preparation method. By growing cobalt oxide particles on the surface of Fe-C 3 N 4 a non-noble metal-based OER catalyst with a low overpotential was constructed. OER performance tests showed that it exhibited a rather low OER overpotential of only 361 mV at a current density of 10 mA cm -2 . And this catalyst has good stability, and the overpotential only increased by 6 mV after 1000 cyclic voltammetry tests. However, there is still a certain gap compared with the OER performance of noble metal catalysts. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention proposes a cobalt and iron doped Bi2 O 3 Preparation method of composite graphene oxide OER catalyst, the preparation method using cobalt iron doped Bi 2 O 3 The nanowires are composited with graphene oxide having a large surface area to form a non-precious metal-based OER catalyst having a large number of compact heterostructures. The non-precious metal-based OER catalyst can promote electron transfer between cobalt, iron, and oxygen elements, and improve the electrode reaction kinetic rate during the OER process, so it not only has a low OER overpotential and Tafel slope, but also has excellent stability. The present invention aims to improve the performance gap between existing non-precious metal-based OER catalysts and precious metal-based OER catalysts by constructing a heterostructure modification method.

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

[0007] A cobalt-iron doped Bi 2 O 3 The preparation method of the OER catalyst of composite graphene oxide comprises the following steps:

[0008] Step S1: Phosphomolybdic acid (H 3 [P(Mo 3 O 10 ) 4 ]) was dissolved in deionized water and cobalt nitrate hexahydrate (Co(NO 3 ) 2 6H 2 O), ferric nitrate nonahydrate (Fe(NO 3 ) 3 9H 2 O) and bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O), stirring to obtain a metal precursor solution A;

[0009] Step S2: stirring the metal precursor solution A and 1-octadecene uniformly, and then adding oleylamine to obtain a reaction precursor solution B;

[0010] Step S3: hydrothermally react the reaction precursor solution B, and centrifuge and wash the solid product to obtain cobalt-iron doped nanowires CoFe-Bi 2 O 3 -PMA;

[0011] Step S4: CoFe-Bi 2 O 3 -PMA is dispersed in cyclohexane to form a nanowire dispersion;

[0012] Step S5: mixing and stirring the nanowire dispersion and the graphene oxide deionized water dispersion to obtain a reaction precursor solution C;

[0013] Step S6: hydrothermally react the reaction precursor solution C, and centrifuge and wash the solid product to obtain a cobalt-iron-doped Bi 2 O 3 Non-noble metal-based OER catalysts based on nanowire composite graphene oxide.

[0014] Preferably, the stirring in step S1 is performed by 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. and a reaction time of 8 h.

[0016] Preferably, the solvents used for the centrifugal washing in step S3 are cyclohexane and anhydrous ethanol, the centrifugal speed is 10000 rpm, the centrifugal time is 3 min, and the number of centrifugal washings is 3 times.

[0017] Preferably, the step S4 specifically comprises: 2 O 3 -PMA was dispersed in 3.5 ml of cyclohexane to a concentration of 15 mg ml -1 of nanowire dispersion.

[0018] Preferably, the nanowire dispersion in step S5 is the same as the graphene oxide deionized water dispersion, and the stirring is performed by 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. and a reaction time of 2 h.

[0020] Preferably, in step S1, the mass of phosphomolybdic acid is 0.8 g, the volume of deionized water is 16 ml, and the masses of cobalt nitrate hexahydrate, iron nitrate nonahydrate and bismuth nitrate pentahydrate are 0.12 g, 0.03 g and 0.05 g 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, the solvents used for the centrifugal washing in step S6 are cyclohexane and anhydrous ethanol, the centrifugal speed is 10000 rpm, the centrifugal time is 3 min, and the number of centrifugal washings is 3 times.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The present invention proposes a cobalt-iron doped Bi 2 O3 Preparation method of composite graphene oxide OER catalyst, the preparation method is to obtain cobalt iron doped Bi by secondary hydrothermal method 2 O 3 A non-precious metal-based OER catalyst of nanowire composite graphene oxide. The non-precious metal-based OER catalyst has excellent OER catalytic activity, reaching 10 mA cm -2 The current density only requires an overpotential of 334 mV, and the corresponding Tafel slope is 68 mV dec -1 In addition, stability tests revealed that the non-noble metal-based OER catalysts possessed good stability.

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

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use 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 drawings. The drawings are schematic and should not be understood as limiting the present invention in any way. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 The cobalt-iron doped Bi 2 O 3 Flow chart of the preparation method of OER catalyst of composite graphene oxide.

[0028] Figure 2 The cobalt-iron doped Bi prepared in Example 1-4 2 O 3 Schematic diagram of the synthesis of nanowire composite graphene oxide samples.

[0029] Figure 3 CoFe-Bi 2 O 3 -PMA (a) X-ray diffraction pattern, (b) transmission electron microscope image, and (c) distribution map of phosphorus, oxygen, bismuth, cobalt, and iron elements.

[0030] Figure 4 CoFe-Bi 2 O 3 -PMA and CoFe-Bi prepared in Example 1 2 O3 -PMA / Go 0.01 Infrared spectra of the composite samples.

[0031] Figure 5 CoFe-Bi 2 O 3 -PMA and CoFe-Bi prepared in Example 1 2 O 3 -PMA / Go 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 OER catalytic performance diagrams of the composite samples with different graphene oxide concentrations prepared in Examples 1-4 in 1M KOH are shown in Figures 1-4. (a) Linear sweep voltammogram, (b) Electrochemical impedance spectroscopy, (c) Tafel slope diagram, and (d) Double layer capacitance diagram.

[0033] Figure 7 The CoFe-Bi prepared in Example 1 2 O 3 -PMA / Go 0.01 Stability test diagram of composite samples. DETAILED DESCRIPTION

[0034] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0036] Example 1

[0037] Prepare graphene oxide with a concentration of 0.01 mg ml -1 Cobalt-Fe-doped Bi 2 O 3 Nanowire composite graphene oxide CoFe-Bi 2 O 3 -PMA / Go 0.01 Composite samples:

[0038] Step 1: Take 0.8g of phosphomolybdic acid and dissolve it in 16ml of deionized water in a 40ml reactor, then add 0.12g of Co(NO3 ) 2 6H 2 O, 0.03g Fe(NO 3 ) 3 9H 2 O and 0.05 g Bi(NO 3 ) 3 ·5H 2 O, and vigorously stir 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, and then add 6 ml of oleylamine to obtain a reaction precursor solution B. The reactor was sealed and placed in a forced air drying oven for hydrothermal reaction at a reaction temperature of 180° C. for 8 hours.

[0040] Step 3: The solid product obtained by the reaction was centrifuged and washed three times with cyclohexane and anhydrous ethanol solvent to obtain a clean cobalt-iron doped nanowire sample CoFe-Bi 2 O 3 -PMA. The centrifugal speed was 10000rpm and the centrifugal time was 3 minutes. 2 O 3 -PMA was dispersed in cyclohexane solvent and the concentration of the dispersion was controlled to be about 0.15 mg ml -1 .

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

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

[0043] Step 6: The solid product obtained by the reaction was washed three times by centrifugation using cyclohexane and anhydrous ethanol solvents at a centrifugal speed of 10000 rpm for 3 minutes to finally obtain clean cobalt-iron doped Bi 2 O 3 Nanowire composite graphene oxide CoFe-Bi 2 O 3 -PMA / Go 0.01 Composite samples.

[0044] Example 2

[0045] Prepare graphene oxide with a concentration of 0.05 mg ml -1 Cobalt-Fe-doped Bi 2 O3 Nanowire composite graphene oxide CoFe-Bi 2 O 3 -PMA / Go 0.05 Composite samples:

[0046] Step 1: Take 0.8g of phosphomolybdic acid and dissolve it in 16ml of deionized water in a 40ml reactor, then add 0.12g of Co(NO 3 ) 2 6H 2 O, 0.03g Fe(NO 3 ) 3 9H 2 O and 0.05 g Bi(NO 3 ) 3 ·5H 2 O, and vigorously stir 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, and then add 6 ml of oleylamine to obtain the reaction precursor solution B. The reactor was sealed and placed in a forced air drying oven for hydrothermal reaction at a reaction temperature of 180° C. for 8 hours.

[0048] Step 3: The solid product obtained by the reaction was centrifuged and washed three times with cyclohexane and anhydrous ethanol solvent to obtain a clean cobalt-iron doped nanowire sample CoFe-Bi 2 O 3 -PMA. The centrifugal speed was 10000rpm and the centrifugal time was 3 minutes. 2 O 3 -PMA was dispersed in cyclohexane solvent, and the concentration of the dispersion was controlled to be about 0.15 mg ml -1 .

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

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

[0051] Step 6: The solid product obtained by the reaction was washed three times by centrifugation using cyclohexane and anhydrous ethanol solvents at a centrifugal speed of 10000 rpm for 3 minutes to finally obtain clean cobalt-iron doped Bi 2 O 3 Nanowire composite graphene oxide CoFe-Bi2 O 3 -PMA / Go 0.05 Composite samples.

[0052] Example 3

[0053] Prepare graphene oxide with a concentration of 0.15 mg ml -1 Cobalt-Fe-doped Bi 2 O 3 Nanowire composite graphene oxide CoFe-Bi 2 O 3 -PMA / Go 0.15 Composite samples:

[0054] Step 1: Take 0.8g of phosphomolybdic acid and dissolve it in 16ml of deionized water in a 40ml reactor, then add 0.12g of Co(NO 3 ) 2 6H 2 O, 0.03g Fe(NO 3 ) 3 9H 2 O and 0.05 g Bi(NO 3 ) 3 ·5H 2 O, and vigorously stir 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, and then add 6 ml of oleylamine to obtain the reaction precursor solution B. The reactor was sealed and placed in a forced air drying oven for hydrothermal reaction at a reaction temperature of 180° C. for 8 hours.

[0056] Step 3: The solid product obtained by the reaction was centrifuged and washed three times with cyclohexane and anhydrous ethanol solvent to obtain a clean cobalt-iron doped nanowire sample CoFe-Bi 2 O 3 -PMA. The centrifugal speed was 10000rpm and the centrifugal time was 3 minutes. 2 O 3 -PMA was dispersed in cyclohexane solvent and the concentration of the dispersion was controlled to be about 0.15 mg ml -1 .

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

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

[0059] Step 6: The solid product obtained by the reaction was washed three times by centrifugation using cyclohexane and anhydrous ethanol solvents at a centrifugal speed of 10000 rpm for 3 minutes to finally obtain clean cobalt-iron doped Bi 2 O 3 Nanowire composite graphene oxide CoFe-Bi 2 O 3 -PMA / Go 0.15 Composite samples.

[0060] Example 4

[0061] Prepare graphene oxide with a concentration of 0.25 mg ml -1 Cobalt-Fe-doped Bi 2 O 3 Nanowire composite graphene oxide CoFe-Bi 2 O 3 -PMA / Go 0.25 Composite samples:

[0062] Step 1: Take 0.8g of phosphomolybdic acid and dissolve it in 16ml of deionized water in a 40ml reactor, then add 0.12g of Co(NO 3 ) 2 6H 2 O, 0.03g Fe(NO 3 ) 3 9H 2 O and 0.05 g Bi(NO 3 ) 3 ·5H 2 O, and vigorously stir 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, and then add 6 ml of oleylamine to obtain the reaction precursor solution B. The reactor was sealed and placed in a forced air drying oven for hydrothermal reaction at a reaction temperature of 180° C. for 8 hours.

[0064] Step 3: The solid product obtained by the reaction was centrifuged and washed three times with cyclohexane and anhydrous ethanol solvent to obtain a clean cobalt-iron doped nanowire sample CoFe-Bi 2 O 3 -PMA. The centrifugal speed was 10000rpm and the centrifugal time was 3 minutes. 2 O 3 -PMA was dispersed in cyclohexane solvent and the concentration of the dispersion was controlled to be about 0.15 mg ml-1 .

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

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

[0067] Step 6: The solid product obtained by the reaction was washed three times by centrifugation using cyclohexane and anhydrous ethanol solvents at a centrifugal speed of 10000 rpm for 3 minutes to finally obtain clean cobalt-iron doped Bi 2 O 3 Nanowire composite graphene oxide CoFe-Bi 2 O 3 -PMA / Go 0.25 Composite samples.

[0068] Figure 1 The cobalt-iron doped Bi 2 O 3 Flow chart of the preparation method of OER catalyst of composite graphene oxide. Figure 2 The cobalt-iron doped Bi prepared in Examples 1-4 is shown. 2 O 3 Schematic diagram of the synthesis of nanowire composite graphene oxide samples, in which cobalt-iron doped Bi was first prepared by a secondary hydrothermal method. 2 O 3 Then, a series of Co-Fe-doped Bi nanowires were prepared by adjusting the concentration of graphene oxide dispersion. 2 O 3 Nanowire composite graphene oxide composite sample. The prepared cobalt iron doped Bi 2 O 3 Nanowire CoFe-Bi 2 O 3 -X-ray diffraction pattern of PMA sample Figure 3 As shown. There exists a corresponding 2 O 3 The characteristic diffraction peak of Bi 2 O 3 The transmission electron microscope images and the surface distribution diagrams of phosphorus, oxygen, bismuth, cobalt and iron elements show that the cobalt-iron doped nanowires have a very high aspect ratio and the cobalt-iron elements are evenly distributed on the surface of the nanowires.

[0069] Figure 4 CoFe-Bi 2 O 3-PMA and CoFe-Bi prepared in Example 1 2 O 3 -PMA / Go 0.01 The infrared spectra of the samples indicate that phosphomolybdic acid clusters exist in both the cobalt-iron doped samples and the composite samples, and the secondary hydrothermal preparation process does not affect the Keggin configuration of phosphomolybdic acid.

[0070] Figure 5 CoFe-Bi 2 O 3 -PMA and CoFe-Bi prepared in Example 1 2 O 3 -PMA / Go 0.01 The presence of CC bonds and CO bonds in the C 1s spectrum indicates that the composite sample contains graphene oxide. From the high-resolution photoelectron energy spectra of O 1s, Co 2p and Fe2p, it can be observed that there is an obvious shift in the binding energy peak after the composite graphene oxide, indicating that the graphene oxide and CoFe-Bi 2 O 3 -PMA. In addition, the multivalent binding energy peaks of cobalt, iron, and oxygen elements shifted toward the high binding energy direction, indicating that the electrons in the composite sample shifted from CoFe-Bi 2 O 3 -PMA transfers to graphene oxide and reaches thermodynamic equilibrium, and there is a close heterostructure between the two.

[0071] Figure 6 The OER catalytic performance of the composite samples with different graphene oxide concentrations prepared in Examples 1-4 in 1M KOH shows that the composite samples all have good electrocatalytic performance. 2 O 3 -PMA / Go x (x=0.01, 0.05, 0.15, 0.25) samples were tested at a current density of 10 mA cm -2 The overpotentials of the composite samples are 334mV, 344mV, 345mV and 354mV respectively, and with the increase of graphene oxide concentration, the OER performance of the composite samples gradually decreases. 2 O 3 -PMA / Go 0.01 It has the smallest charge transfer resistance and Tafel slope, and its double layer capacitance is 1.26mF cm -2 , which is higher than other composite samples, indicating that it has the largest electrochemical active area. Combining the electrocatalytic test results and photoelectron spectroscopy analysis results, the improvement in OER activity of the composite sample can be attributed to the compact heterostructure that optimizes the CoFe-Bi2 O 3 -The electron transfer between PMA and graphene oxide improves the electrode reaction kinetics rate of the composite sample.

[0072] Figure 7 The CoFe-Bi prepared in Example 1 2 O 3 -PMA / Go 0.01 The stability test diagram of the composite sample shows that after 100 minutes of OER test, the voltage increase of the working electrode at different current densities is 57mV (20mAcm -2 ) and 87mV(50mAcm -2 ), indicating that the composite sample has good stability.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a cobalt-iron doped Bi2O3 composite graphene oxide OER catalyst, characterized in that: The following steps are involved: Step S1: Phosphomolybdic acid (H3[P(Mo3O 10 )4]) was dissolved in deionized water, and cobalt nitrate hexahydrate (Co(NO3)2·6H2O), iron nitrate nonahydrate (Fe(NO3)3·9H2O) and bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) were added and stirred to obtain a metal precursor solution A; Step S2: stirring the metal precursor solution A and 1-octadecene uniformly, and then adding oleylamine to obtain a reaction precursor solution B; Step S3: performing a hydrothermal reaction on the reaction precursor solution B, and washing the solid product by centrifugation to obtain cobalt-iron doped nanowires CoFe-Bi2O3-PMA; Step S4: dispersing CoFe-Bi2O3-PMA in cyclohexane to form a nanowire dispersion; Step S5: mixing and stirring the nanowire dispersion and the graphene oxide deionized water dispersion to obtain a reaction precursor solution C; Step S6: performing a hydrothermal reaction on the reaction precursor solution C, and centrifugally washing the solid product to obtain a non-precious metal-based OER catalyst based on cobalt-iron doped Bi2O3 nanowires composite graphene oxide.

2. The preparation method according to claim 1, characterized in that: The stirring in step S1 is performed by 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 reaction temperature of 180° C. for a reaction time of 8 h.

4. The preparation method according to claim 3, characterized in that: The solvents used for the centrifugal washing in step S3 are cyclohexane and anhydrous ethanol, the centrifugal speed is 10000 rpm, the centrifugal time is 3 min, and the number of centrifugal washing is 3 times.

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

6. The preparation method according to claim 5, characterized in that: In step S5, the nanowire dispersion liquid is the same as the graphene oxide deionized water dispersion liquid, and the stirring is performed by 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 reaction temperature of 120° C. for a reaction time of 2 h.

8. The preparation method according to claim 7, characterized in that: In the step S1, the mass of phosphomolybdic acid is 0.8 g, the volume of deionized water is 16 ml, and the masses of cobalt nitrate hexahydrate, iron nitrate nonahydrate and bismuth nitrate pentahydrate are 0.12 g, 0.03 g and 0.05 g 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: The solvents used for the centrifugal washing in step S6 are cyclohexane and anhydrous ethanol, the centrifugal speed is 10000 rpm, the centrifugal time is 3 min, and the number of centrifugal washings is 3 times.

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