Difunctional boron-doped molybdenum-cobalt microsphere full-water-splitting catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electrochemical bifunctional complete water splitting catalyst materials, and particularly relates to a bifunctional boron-doped molybdenum-cobalt microsphere complete water splitting catalyst and a preparation method and application thereof. Ammonium heptamolybdate and cobaltous acetate tetrahydrate are dissolved in water in a small amount of sulfuric acid and boric acid sodium citrate system according to a certain molar ratio; the preparation method comprises the following steps of: taking nickel foam as a working electrode, taking a platinum sheet and an Ag / AgCl electrode as a counter electrode and a reference electrode, depositing for 10-30 minutes at the temperature of 20-50 DEG C under the current density of-300 to-200mA cm <-2 >, washing the surface of the nickel foam with deionized water after electro-deposition is completed, and carrying out vacuum drying to obtain the black micro-sphere boron-doped MoCo material loaded on the nickel foam. The catalyst prepared by the invention has the characteristics of low cost, no toxicity and high chemical activity and stability, and shows high hydrogen and oxygen evolution activity and low overpotential.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical bifunctional complete water splitting catalyst materials, and specifically relates to a bifunctional boron-doped molybdenum-cobalt micron sphere complete water splitting catalyst and a preparation method and application thereof. Background Art

[0002] Due to the increasing consumption of traditional fossil fuels, urgent environmental issues have driven energy demand. Hydrogen production by water electrolysis has become an important solution for converting renewable energy into practical chemical forms due to its advantages such as high energy density and pollution-free. However, hydrogen production by water electrolysis is limited by two half reactions: the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER). Therefore, the development of efficient bifunctional catalysts has become a general trend.

[0003] Among the current catalyst materials, precious metal-based catalysts are still the mainstream materials. For example, Pt-based catalysts for HER; Ir / Ru-based catalysts for OER. Although they show ideal performance and low HER and OER overpotentials, their scarcity and high cost hinder their larger-scale development. Therefore, seeking a low-cost, easily available, efficient and stable non-precious metal-based bifunctional electrocatalyst is the focus of current scientific researchers.

[0004] Among non-precious metal elements, molybdenum-based catalysts show excellent HER catalytic performance due to their unique structure and are well-known catalysts for hydrogen evolution reaction in water electrolysis. However, there are very few reports on them in OER. Cobalt-based materials are good OER catalysts. In addition, the adjustment of electronic structure is important for providing optimized catalysts. Therefore, by introducing Co to effectively couple with Mo, the electronic structure is reformed in order to prepare a bifunctional all-water splitting catalyst that can be used for both HER and OER. In addition, boride has the advantages of low cost, high structural strength and chemical stability and can extend the service life of the catalyst. The preparation of catalysts in a boric acid system can induce the formation of an amorphous structure, thereby adjusting the electronic structure of the host material and generating electrocatalytic unsaturated coordination active sites. Sodium citrate can make metal ions uniformly dispersed in the electrolyte, which is conducive to uniform deposition on the electrode surface. Therefore, the preparation of boron-doped MoCo catalysts in a boric acid sodium citrate system is a promising method to achieve bifunctional high catalytic performance and long-term stability. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a bifunctional micron sphere self-supporting water splitting catalyst material and a preparation method thereof by a simple one-step electrodeposition method. The catalyst prepared by the present invention has the characteristics of low cost, non-toxicity, high activity and high chemical stability.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst, the preparation method of which comprises the following steps:

[0008] 1) Pretreatment of nickel foam: cutting the nickel foam into small pieces, ultrasonically cleaning in acetone, anhydrous ethanol and deionized water respectively to remove grease, impurities and oxide layer on the surface of the nickel foam sample, and vacuum drying the cleaned nickel foam sample;

[0009] 2) Prepare electrodeposition solution: Add ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 ) and cobalt acetate tetrahydrate (Co(CH 3 COO 2 ·4H 2 O) Add 80-120 mL of deionized water to the sodium borate citrate environment, then add 1-2 mL of sulfuric acid, add all the chemicals to the electrolytic cell, and heat at a constant temperature of 20-50°C until a transparent solution is obtained, which is the electrodeposition solution;

[0010] 3) Cleaning the nickel foam substrate: ultrasonically clean the nickel foam treated in step 1) with a hydrochloric acid solution, and then wash the nickel foam sample with a large amount of anhydrous ethanol and distilled water for multiple times to remove the hydrochloric acid remaining on the surface thereof, and quickly air-dry the cleaned nickel foam with a hair dryer, and then immediately immerse it in the electrodeposition solution of the electrolytic cell;

[0011] 4) Preparation of bifunctional boron-doped MoCo microspheres as a water splitting catalyst by electrodeposition in a three-electrode system: nickel foam was used as the working electrode, platinum sheet and Ag / AgCl electrode were used as the counter electrode and reference electrode, and the current density was set to -300 to -200 mA cm -2 , deposited at 20-50°C for 10-30 minutes; after the electrodeposition is completed, the surface of the nickel foam sample is rinsed with deionized water and vacuum dried to obtain a bifunctional boron-doped MoCo microsphere full water splitting catalyst.

[0012] Furthermore, in the above-mentioned bifunctional boron-doped molybdenum-cobalt microsphere complete water splitting catalyst, in step 1), the nickel foam with a thickness of 1 mm is cut into small pieces of 1 cm×1.5 cm.

[0013] Furthermore, in the above-mentioned bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst, in step 1) and step 3), the ultrasonic cleaning is performed at 20-40° C. for 10-20 minutes, and the cleaning power is 900-1200W.

[0014] Furthermore, in the above-mentioned bifunctional boron-doped molybdenum-cobalt microsphere complete water splitting catalyst, in step 1), the vacuum drying is carried out at 30-60° C. for 10-15 hours.

[0015] Further, in the above-mentioned bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst, in step 2), ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 ) accounts for the amount of ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 ), cobalt acetate tetrahydrate (Co(CH 3 COO 2 ·4H 2 O) and boric acid (H 3 BO 3 )16%-27% of the total substance.

[0016] Furthermore, in the above-mentioned bifunctional boron-doped molybdenum-cobalt microspheres for water splitting, in step 2), cobalt acetate tetrahydrate (Co(CH 3 COO 2 ·4H 2 O) accounts for the amount of ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 ), cobalt acetate tetrahydrate (Co(CH 3 COO 2 ·4H 2 O) and boric acid (H 3 BO 3 )5%-17% of the total amount of the substance.

[0017] Preferably, in the above-mentioned bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst, in step 2), boric acid (H 3 BO 3 ) accounts for the amount of ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 ), cobalt acetate tetrahydrate (Co(CH 3 COO 2 ·4H 2 O) and boric acid (H 3 BO 3 ) 60%-70% of the total amount of the substance. (That is, after a simple one-step electrodeposition, the amount ratio of Mo, Co and B is 3:1:8).

[0018] Furthermore, in the above-mentioned bifunctional boron-doped molybdenum-cobalt microsphere complete water splitting catalyst, in step 2), the constant temperature heating condition is: the temperature is 20-50°C.

[0019] Further, in the above-mentioned bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst, in step 3), the concentration of the hydrochloric acid solution is 5-8 mol L -1 .

[0020] Furthermore, in the above-mentioned bifunctional boron-doped molybdenum-cobalt microsphere complete water splitting catalyst, in step 4), the vacuum drying is carried out at 20-50° C. for 60-120 minutes.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention uses a one-step simple electrodeposition method to controllably prepare a self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst, which can save the tedious steps of coating the catalyst suspension on a glassy carbon electrode or carbon cloth, significantly improve its conductivity, and can directly test its performance, which is simple, convenient, and takes a short time.

[0023] 2. The present invention can control different morphologies by changing different electrodeposition currents, electrodeposition time, sulfuric acid concentration, boric acid concentration, electrolyte substances and proportions, and prepares micron-sized spherical materials through a one-step simple electrodeposition method. The formed catalyst coating presents a relatively uniform spherical shape. After magnification, it can be observed that the surface of the spherical catalyst is uneven and resembling a durian peel. This structure can provide a larger specific surface area, thereby providing more active sites, and ultimately improving the catalytic activity.

[0024] 3. The bifunctional boron-doped MoCo microsphere water splitting catalyst prepared by the present invention through a one-step simple electrodeposition method has a simple process flow and is easy to operate compared with other chemical synthesis methods. It can reduce waste liquid pollution to a certain extent, and is economical and environmentally friendly. Electrodeposition is assisted in a boric acid sodium citrate system to obtain a catalyst with high catalytic activity. The raw materials for preparation are cheap and easy to obtain, which is more conducive to promoting commercial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 These are SEM images of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst prepared in Example 1 of the present invention, with magnifications of 0.5K, 5K, 20K and 100K respectively.

[0026] Figure 2 This is the XRD diagram of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst prepared in Example 1 of the present invention.

[0027] Figure 3This is the ICP diagram of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst prepared in Example 1 of the present invention.

[0028] Figure 4 This is a TEM image of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst prepared in Example 1 of the present invention.

[0029] Figure 5 The current density of Example 1 of the present invention is 600 mA cm -2 A graph showing the changes in the amount of oxygen and hydrogen collected over time.

[0030] Figure 6 The LSV curves of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst deposited at different current densities. Figure (a) is the electrochemical HER performance polarization curve, and Figure (b) is the electrochemical OER performance polarization curve.

[0031] Figure 7 The LSV curves of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst deposited at different times. Figure (a) is the electrochemical HER performance polarization curve, and Figure (b) is the electrochemical OER performance polarization curve.

[0032] Figure 8 The LSV curves of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst deposited at different sulfuric acid concentrations. Figure (a) is the electrochemical HER performance polarization curve, and Figure (b) is the electrochemical OER performance polarization curve.

[0033] Fig. 9 The LSV curves of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst deposited at different boric acid concentrations. Figure (a) is the electrochemical HER performance polarization curve, and Figure (b) is the electrochemical OER performance polarization curve.

[0034] Fig.10 The LSV curves obtained by replacing the deposition of different materials. Figure (a) is the electrochemical HER performance polarization curve, and Figure (b) is the electrochemical OER performance polarization curve.

[0035] Fig.11 Figure 2 is the LSV curve obtained under different molybdenum-cobalt ratios. Figure (a) is the electrochemical HER performance polarization curve, and Figure (b) is the electrochemical OER performance polarization curve.

[0036] Fig.12 This is the LSV curve diagram of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst prepared in Example 1 of the present invention, Figure (a) is the iR-corrected HER performance polarization curve, and Figure (b) is the iR-corrected OER performance polarization curve.

[0037] Fig.13 This is the LSV curve of the self-supporting bifunctional boron-doped MoCo microsphere catalyst for complete water splitting prepared in Example 1 of the present invention.

[0038] Fig.14 It is an it curve diagram of the complete water splitting of the self-supporting bifunctional boron-doped MoCo microsphere catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] Example 1

[0040] (I) Preparation method

[0041] 1) Pretreatment of nickel foam: nickel foam (NF) with a thickness of 1 mm was cut into small pieces of 1 cm × 1.5 cm, and ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 15 minutes at room temperature (power of 1000 W) to remove grease, impurities and oxide layer on the surface of the nickel foam sample. The cleaned nickel foam sample was placed in a vacuum drying oven and dried at 50° C. for 12 h;

[0042] 2) Preparation of electrodeposition solution: ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 )0.1875M, cobalt acetate tetrahydrate (Co(CH 3 COO 2 ·4H 2 O) 0.0625M, ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 ) and cobalt acetate tetrahydrate (Co(CH 3 COO 2 ·4H 2 O) to a total of 0.25 M, and then weigh boric acid (H 3 BO 3 )0.5M and sodium citrate (C 6 O 7 H 5 Na 3 ·2H 2 O) 0.3 M, then sulfuric acid (H 2 SO 4 )0.5M, add all the chemicals into 100mL deionized water, and heat at a constant temperature of 30℃ and 15r / min to a transparent solution, which is the electrodeposition solution.

[0043] 3) Cleaning the nickel foam substrate: Wash the nickel foam treated in step 1) with 6 mol L -1The nickel foam was cleaned with hydrochloric acid solution at room temperature for 15 minutes (power 1000W), and then cleaned several times with a large amount of anhydrous ethanol and distilled water in an ultrasonic machine to remove the residual hydrochloric acid on its surface. The cleaned nickel foam was quickly air-dried with a hair dryer and then immediately immersed in the electrodeposition solution of the electrolytic cell.

[0044] 4) Preparation of self-supporting bifunctional boron-doped MoCo microspheres as a water splitting catalyst by electrodeposition in a three-electrode system: nickel foam was used as the working electrode, platinum sheet and Ag / AgCl electrode were used as the counter electrode and reference electrode, and the current density was set to -250 mA cm -2 , deposited at 30 °C for 120 min.

[0045] 5) After the electrodeposition is completed, the surface of the nickel foam sample is rinsed with deionized water and dried in a vacuum drying oven at 30° C. for 120 minutes to obtain a self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst.

[0046] Figure 1 The SEM images of the self-supporting bifunctional boron-doped MoCo microspheres for water splitting are at magnifications of 0.5K, 5K, 20K and 100K. From the images, we can see that the coating is relatively uniformly spherical with a relatively rough surface. After magnification, we can see that the shape is similar to durian skin. This structure can expose more active sites and increase its specific surface area.

[0047] Figure 2 This is the XRD pattern of the self-supported bifunctional boron-doped MoCo microspheres for water splitting. The XRD spectrum is consistent with that of Co (PDF#15-0806). The sample clearly has three diffraction peaks and one envelope peak, which are the (111), (200) and (220) crystal planes of Co and the amorphous envelope peak of B, indicating that cobalt and boron were successfully loaded on nickel foam by electrodeposition.

[0048] Figure 3 This is the ICP graph of the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst. The ICP spectrum shows that the catalyst in Example 1 contains 42.423% of Mo element, 43.272% of Co element and 13.327% of B element, indicating that molybdenum, cobalt and boron are successfully loaded on the nickel foam by electrodeposition.

[0049] Figure 4This is a TEM image of a self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst. The low-magnification TEM morphology and high-resolution HRTEM image of the deposited coating are shown respectively. From the figure, we can see the morphology of amorphous Mo, B and Co with clear lattice fringes. The mapping diagram can further prove the existence of Mo and Co elements, but the existence of B element is not found. It is considered that boron is an element with a very low atomic number and its scattering ability is very small, so it is difficult to be scattered by the electron beam and detected.

[0050] Figure 5 The current density is 600 mA cm -2 The amount of oxygen and hydrogen collected changes with time. After 1299s of water electrolysis, 25mL of oxygen and 50mL of hydrogen were collected. The Faraday efficiency was calculated to be 99.6%, which has a good conversion efficiency.

[0051] (II) Electrocatalytic performance testing

[0052] The electrocatalytic performance of the catalyst was tested at room temperature and pressure in a three-electrode system, with the electrolyte being a 1M KOH aqueous solution, the self-supporting bifunctional boron-doped MoCo microsphere full water splitting catalyst as the working electrode, the platinum sheet as the counter electrode, and the Ag / AgCl electrode as the reference electrode.

[0053] Figure 6 The LSV curves of the self-supporting bifunctional boron-doped MoCo microspheres for water splitting catalysts deposited at different current densities are used to obtain the optimal current density during deposition. According to the curve, it can be concluded that at a current density of -300 mA cm -2 The HER performance is the best when the current density is -250mA cm -2 The OER performance is the best when the OER overpotential is 349.1mV. -2 The performance is best at a current density of -250 mA cm, with a HER overpotential of 149.9 mV and an OER overpotential of 349.1 mV. -2 The electrodeposition time was studied under the current density of 300s, 600s, 900s, 1200s and 1500s.

[0054] Figure 7 The LSV curves of the self-supporting bifunctional boron-doped MoCo microspheres for water splitting catalysts deposited at different times are used to obtain the optimal deposition time. According to the curve, the best performance is obtained when the electrodeposition time is 1200s, with a HER overpotential of 97.9mV and an OER overpotential of 337.1mV. Therefore, at -250mA cm -2The current density and deposition time were 1200s, and the sulfuric acid concentration was used as a variable for further study. 0.1M, 0.25M, 0.5M, and 1M were added respectively.

[0055] Figure 8 The LSV curves of the self-supporting bifunctional boron-doped MoCo microspheres for water splitting catalysts deposited at different sulfuric acid concentrations are used to obtain the optimal sulfuric acid concentration for deposition. According to the curve, the best performance is obtained when the sulfuric acid concentration is 0.25 M, with a HER overpotential of 85.9 mV and an OER overpotential of 340.1 mV. Therefore, at -250 mA cm -2 The current density, deposition time of 1200s and sulfuric acid concentration of 0.25M were used to study the boric acid concentration as a variable. 0.25M, 0.5M and 1M were added respectively.

[0056] Fig. 9 The LSV curves of the self-supporting bifunctional boron-doped MoCo microspheres for water splitting catalysts deposited at different boric acid concentrations are used to obtain the optimal boric acid concentration during deposition. According to the curve, the best performance is achieved when the boric acid concentration is 0.5 M, with a HER overpotential of 85.9 mV and an OER overpotential of 340.1 mV. Therefore, at -250 mA cm -2 Based on the current density of 1000 s, the deposition time of 1200 s, the sulfuric acid concentration of 0.25 M and the boric acid concentration of 0.5 M, the material during deposition was used as a variable for further study. They are FeCoB, FeMoB, MoCoB, FeCoBSe, and FeMoBSe.

[0057] Fig.10 The LSV curves obtained by replacing different materials deposited are used to obtain the best material for hydrogen and oxygen evolution catalysts. According to the curve, it can be concluded that MoCoB has the best performance, with a HER overpotential of 85.9mV and an OER overpotential of 340.1mV. Therefore, boron-doped MoCo is the best species.

[0058] Fig.11 The LSV curves obtained under different molybdenum-cobalt ratios are used to obtain the optimal ratio for boron-doped MoCo catalysts. According to the curve, it can be concluded that the performance is best when molybdenum:cobalt = 3:1, with a HER overpotential of 67.9mV and an OER overpotential of 340.1mV. Therefore, boron-doped molybdenum-cobalt is the best species.

[0059] Fig.12This is the LSV curve of the self-supporting bifunctional boron-doped MoCo microsphere water splitting catalyst, which is used to characterize the catalytic activity of the sample. The test conditions are a three-electrode system, with the Ag / AgCl electrode as the reference electrode, the platinum sheet as the counter electrode, the sample as the working electrode, and the electrolyte as 1M KOH aqueous solution. It can be seen from the image that after 80% overpotential compensation, the current density is -10mA cm -2 Under the conditions, the overpotential is 49.53 mV; at a current density of 10 mA cm -2 Under the above conditions, the overpotential is 321.60mV, which is close to the overpotential of most electrode materials currently available. The lower the overpotential of water electrolysis, the higher the total voltage required for water electrolysis and the conversion efficiency of electrical energy into hydrogen energy, and the higher the Faraday efficiency. Therefore, it has good commercial prospects.

[0060] Fig.13 This is the LSV curve of the self-supporting bifunctional boron-doped MoCo microsphere catalyst for water splitting prepared in Example 1 of the present invention. It can be seen from the image that at a current density of 10 mA cm -2 Under the conditions of , the full cell voltage of water splitting is 1.617V, which is close to the vast majority of electrode materials currently available.

[0061] Fig.14 It is the it curve of the self-supporting bifunctional boron-doped MoCo microsphere catalyst for water splitting prepared in Example 1 of the present invention. It can be seen from the figure that at a current density of 10 mA cm -2 Under these conditions, the full cell voltage of water splitting remained stable at around 1.7V for up to 50h, indicating that this material has good stability.

[0062] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst, characterized in that: The preparation method comprises the following steps: 1) Pretreatment of nickel foam: cutting the nickel foam into small pieces, ultrasonically cleaning in acetone, anhydrous ethanol and deionized water respectively to remove grease, impurities and oxide layer on the surface of the nickel foam sample, and vacuum drying the cleaned nickel foam sample; 2) Prepare electrodeposition solution: Add ammonium heptamolybdate (NH4)6Mo7O 24 and tetrahydrated cobalt acetate Co(CH3COO)2·4H2O are dissolved in deionized water in a boric acid sodium citrate system, and then sulfuric acid is added and heated at a constant temperature to a transparent solution, which is an electrodeposition solution; 3) Cleaning the nickel foam substrate: The nickel foam treated in step 1) is ultrasonically cleaned with a hydrochloric acid solution, and then repeatedly cleaned with a large amount of anhydrous ethanol and distilled water to remove the hydrochloric acid remaining on the surface, quickly air-dried, and then immediately immersed in an electrodeposition solution; 4) Preparation of bifunctional boron-doped MoCo microspheres as a complete water splitting catalyst by electrodeposition in a three-electrode system: using nickel foam as a working electrode, platinum sheet and Ag / AgCl electrode as a counter electrode and reference electrode, electrodeposition was performed, the surface of the nickel foam sample was rinsed with deionized water, and vacuum dried to obtain a bifunctional boron-doped MoCo microspheres as a complete water splitting catalyst.

2. The bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst according to claim 1, characterized in that: In step 1), the nickel foam with a thickness of 1 mm is cut into small pieces of 1 cm×1.5 cm.

3. The bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst according to claim 1, characterized in that: In step 1) and step 3), the ultrasonic cleaning is carried out at 20-40°C for 10-20 minutes, and the cleaning power is 900-1200W.

4. The bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst according to claim 1, characterized in that: In step 1), the vacuum drying is carried out at 30-60° C. for 10-15 hours.

5. The bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst according to claim 1, characterized in that: In step 2), ammonium heptamolybdate (NH4)6Mo7O 24 The amount of substance accounts for ammonium heptamolybdate (NH4)6Mo7O 24 , cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 account for 16%-27% of the total amount.

6. The bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst according to claim 5, characterized in that: In step 2), the amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O is 1:1 of ammonium heptamolybdate (NH4)6Mo7O 24 , cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3, 5%-17% of the total amount of substance.

7. The bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst according to claim 5, characterized in that: In step 2), the amount of boric acid H3BO3 is 1:1 of ammonium heptamolybdate (NH4)6Mo7O 24 , cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 account for 60%-70% of the total amount.

8. The bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst according to claim 1, characterized in that: In step 2), the temperature of the constant temperature heating is 20-50°C.

9. The bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst according to claim 1, characterized in that: In step 4), the electrodeposition condition is that the current density is set to -300 to -200 mA cm -2 , deposit at 20-50°C for 10-30 minutes.

10. Use of a bifunctional boron-doped molybdenum-cobalt microsphere water splitting catalyst as claimed in any one of claims 1 to 9 in electrolysis of water.

Images