Self-supporting lanthanum-molybdenum-cobalt-boron difunctional complete water splitting catalyst as well as preparation method and application thereof

Abstract

The invention relates to a self-supporting lanthanum-molybdenum-cobalt-boron difunctional complete water splitting catalyst as well as a preparation method and application thereof, and belongs to the technical field of electro-catalytic materials. The method comprises the following steps: dissolving lanthanum salt, ammonium heptamolybdate and cobalt acetate tetrahydrate in an aqueous solution containing boric acid and sodium citrate according to a set molar ratio, adding a small amount of sulfuric acid, and heating to form a uniform electrolyte; and by taking the foamed nickel as a working electrode, carrying out electro-deposition for 100-200 minutes at the current density of-300 to-200mA cm <-2 > and the temperature of 20-50 DEG C to obtain the lanthanum-molybdenum-cobalt-boron material loaded on the foamed nickel. The catalyst has a self-supporting structure, does not need a binder, is simple in preparation process, low in cost and environment-friendly, shows high catalytic activity and excellent stability in both hydrogen evolution reaction and oxygen evolution reaction, and is suitable for an efficient all-water decomposition system.

Description

Technical Field

[0001] This invention belongs to the technical field of electrochemical bifunctional water-splitting catalyst materials, specifically relating to a self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst, its preparation method, and its application. Background Technology

[0002] To address the ever-growing global demand for clean energy, electrocatalytic water splitting technology has attracted significant attention due to its ability to efficiently convert water into hydrogen. This technology primarily involves two key half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode, representing a crucial pathway for achieving high-energy-density, zero-pollution hydrogen production. However, HER kinetics are sluggish in alkaline environments, while OER is constrained by a complex four-electron transfer process; both factors jointly limit the energy efficiency of the entire water splitting system. Currently, developing bifunctional electrocatalysts that can synergistically promote HER and OER in the same electrolyte has become a key challenge in advancing the practical application of this technology.

[0003] Because HER and OER have different intrinsic requirements for catalytic active sites, single-component materials cannot simultaneously meet the high-efficiency catalysis requirements of both. In recent years, designing composite catalysts through multi-component synergistic strategies has become an important direction for overcoming performance bottlenecks. The rational combination of transition metals (such as Mo, Co, and Ni) can tune the electronic structure of materials and enrich active sites, effectively improving overall catalytic performance. However, existing high-performance systems still generally rely on precious metals, resulting in high costs, and their HER activity in alkaline media remains unsatisfactory, with the underlying catalytic mechanism still unclear.

[0004] Rare earth elements, with their unique 4f / 5d electronic configuration and lanthanide contraction effect, offer new possibilities for the regulation of catalyst electronic structure. However, their high oxygen affinity and complex reduction behavior also pose challenges to structural control and mechanism research. Studies have shown that constructing heterointerfaces by combining rare earth elements with transition metals helps optimize charge distribution and enhance reactivity, opening up new pathways for developing high-performance bifunctional catalysts based on non-noble metals. Nevertheless, these materials still suffer from harsh synthesis conditions and limited performance in alkaline systems, necessitating further breakthroughs in material design and controllable preparation.

[0005] Given the urgent need for efficient and stable non-precious metal bifunctional catalysts in current water electrolysis for hydrogen production, and the unique potential of rare earth elements in electronic structure modulation, this study designed and prepared a lanthanum-modified molybdenum-cobalt-boron heterostructure catalyst. Previous studies have shown that developing bifunctional catalysts capable of simultaneously and efficiently driving both HER and OER in alkaline media is key to reducing energy consumption and equipment costs in water electrolysis. Although transition metal-based materials (such as cobalt, molybdenum, and their compounds) have shown potential to replace precious metal catalysts due to their synergistic effects, their intrinsic activity and stability still need further improvement. Rare earth elements, especially lanthanum, have been proven to be effective strategies for enhancing the electronic environment of catalysts due to their unique electronic structure characteristics, and are expected to become an effective strategy for enhancing electrocatalytic reaction kinetics.

[0006] Based on the above considerations, this study, building upon previous work, strategically introduced lanthanum to precisely control the electronic structure of the catalyst, thereby enhancing its electrocatalytic activity. A highly coupled heterostructure (Mo3Co1)B2La was successfully prepared via a one-step electrodeposition method. 0.02 The catalyst exhibits enhanced synergistic effects and excellent bifunctional catalytic activity. In an alkaline medium with a three-electrode system, the catalyst shows good performance at 10 mA cm⁻¹. -2 At the specified current densities, low overpotentials of 25.98 mV (HER) and 290.83 mV (OER) were achieved, respectively. When applied to a total water splitting system, (Mo3Co1)B2La... 0.02 The catalyst's electrolyzer requires only a low battery voltage of 1.6V to drive a current density of 10mA cm⁻² and maintained excellent stability during 120 hours of continuous operation without significant performance degradation.

[0007] This work not only deepens our understanding of the role of rare earth elements in electrocatalytic water splitting and confirms their key role in optimizing reaction kinetics, but also provides new ideas and universal methods for the rational design of high-performance alkaline water electrolysis catalysts through rare earth regulation strategies. Summary of the Invention

[0008] To address the technical bottlenecks of existing water electrolysis catalysts, such as strong dependence on precious metals, complex preparation processes, and insufficient stability, this invention provides a lanthanum-molybdenum-cobalt-boron self-supporting electrode material prepared by a one-step electrodeposition method. This method is simple and environmentally friendly. The prepared catalyst exhibits high catalytic activity and excellent chemical stability in both hydrogen evolution and oxygen evolution reactions, possessing significant advantages such as low cost, non-toxicity, and ease of large-scale application. This provides a promising material solution for achieving efficient and sustainable hydrogen production through water electrolysis.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A self-supported lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst is prepared by the following steps:

[0011] 1) Pretreatment of nickel foam: Cut the nickel foam into small pieces and ultrasonically clean them in acetone, anhydrous ethanol and deionized water respectively to remove grease, impurities and oxide layer from the surface of the nickel foam sample. Vacuum dry the cleaned nickel foam sample.

[0012] 2) Preparation of electrodeposition solution: Lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and ammonium heptamolybdate ((NH4)6Mo7O) are added. 24 Cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O) is added to 80-120 mL of deionized water in a sodium borate and citrate environment, followed by 1-2 mL of sulfuric acid. All reagents are then added to an electrolytic cell and heated at a constant temperature of 20-50℃ and 10-30 r / min until a transparent solution is obtained, which is the electrodeposition solution.

[0013] 3) Cleaning the substrate nickel foam: The nickel foam treated in step 1) is ultrasonically cleaned with hydrochloric acid solution, and then the nickel foam sample is repeatedly cleaned with a large amount of anhydrous ethanol and distilled water to remove the hydrochloric acid residue on its surface. The cleaned nickel foam is quickly dried with a hair dryer and then immersed in the electrodeposition solution for subsequent use.

[0014] 4) Preparation of a bifunctional lanthanum-molybdenum-cobalt-boron high-efficiency and stable total water splitting catalyst by electrodeposition in a three-electrode system: Nickel foam was used as the working electrode, and carbon rods and Ag / AgCl electrodes were used as the counter and reference electrodes, respectively. The current density was set to -300 to -200 mA / cm². -2 The electrodeposition process was carried out at 20-50℃ for 100-200 minutes. After electrodeposition, the surface of the nickel foam sample was rinsed with deionized water and vacuum dried to obtain a bifunctional lanthanum-molybdenum-cobalt-boron high-efficiency and stable total water splitting catalyst.

[0015] Furthermore, in step 1) of the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst, a 1mm thick nickel foam is cut into 1cm×1cm pieces.

[0016] Furthermore, in the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst, in steps 1) and 3), the ultrasonic cleaning is performed at 10-50°C for 10-20 minutes with a cleaning power of 400-600W.

[0017] Furthermore, in the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst, step 1) involves vacuum drying at 30-60°C for 10-15 hours.

[0018] Furthermore, in the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst, in step 2), lanthanum nitrate hexahydrate (La(NO3)3·6H2O) accounts for a proportion of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and ammonium heptamolybdate (NH4)6Mo7O 24 The total amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 is 0.5%-1%.

[0019] Furthermore, in the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst, in step 2), ammonium heptamolybdate (NH4)6Mo7O 24 The amount of substance is equal to that of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and ammonium heptamolybdate (NH4)6Mo7O. 24 The total amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 is 15%-30%.

[0020] Furthermore, in step 2) of the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water-splitting catalyst, the molar amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O accounts for a certain percentage of the amount of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and ammonium heptamolybdate (NH4)6Mo7O. 24 The total amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 is 5%-20%.

[0021] Preferably, in step 2) of the above-mentioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst, the molar amount of boric acid H3BO3 accounts for the proportion of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and ammonium heptamolybdate (NH4)6Mo7O. 24 The total amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 is 60%-70%.

[0022] Furthermore, in the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst, the molar ratio of molybdenum ions to cobalt ions is 5:1 to 1:1.

[0023] Furthermore, in step 2) of the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst, the isothermal heating conditions are: temperature 20-50℃ and rotation speed 10-30 r / min.

[0024] Furthermore, in the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst, in step 3), the concentration of the hydrochloric acid solution is 5-8 mol / L. -1 .

[0025] Furthermore, in step 4) of the aforementioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst, the vacuum drying is performed at 20-50°C for 60-150 minutes.

[0026] The above-described self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst is applied in water electrolysis.

[0027] The above application is carried out as follows: two of the above-mentioned self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water-splitting catalysts are used as the cathode and anode, respectively, for water electrolysis.

[0028] In the above application, the conditions for water electrolysis are a constant current density of 100-300 mA·s⁻ 1 Constant current electrolysis is performed within the temperature range of 20-50℃.

[0029] The beneficial effects of this invention are as follows:

[0030] 1. This invention employs a one-step electrodeposition technique to successfully prepare a self-supported lanthanum-molybdenum-cobalt-boron bifunctional catalyst, which can be directly used as a working electrode for the whole water splitting reaction. This method eliminates the complex steps of coating the catalyst slurry onto a glassy carbon electrode or carbon cloth in traditional preparation processes, simplifying the preparation process, shortening the preparation time, and effectively enhancing the conductivity and structural stability of the electrode. This makes it easier to directly test the electrocatalytic performance, and it has the advantages of simple process, high integration, and strong applicability.

[0031] 2. This invention controls different morphologies by changing the molar content of different La(NO3)3·6H2O, electrodeposition current, electrodeposition time, different substances, and different ratios of Mo and Co. Through a simple one-step electrodeposition method, a dense and flat catalyst coating is prepared. This structure can improve the bonding force between the coating and the substrate, resulting in better catalytic effect.

[0032] 3. This invention relates to a self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst and its preparation method. This catalyst is suitable for total water splitting reactions. Compared with traditional chemical synthesis processes, this invention employs a one-step electrodeposition method, introducing lanthanum into the boric acid-sodium citrate electrolyte system for regulation, thereby simplifying the process and improving operational efficiency. This method has advantages such as low raw material cost, easy availability, and minimal waste pollution. While reducing preparation costs, it also considers environmental friendliness, contributing to the large-scale preparation and commercial application of efficient, stable, and low-cost water splitting catalysts. Attached Figure Description

[0033] Figure 1 These are SEM images of the self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst prepared in Example 1 of this invention. The magnifications from left to right are 2K, 5K, and 10K, respectively.

[0034] Figure 2 This is the XRD pattern of the self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst prepared in Example 1 of this invention.

[0035] Figure 3 This is a TEM image of the self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst prepared in Example 1 of this invention.

[0036] Figure 4 The figures show the linear sweep voltammetry (LSV) curves of the self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst prepared in Example 1 of this invention under different molar amounts of lanthanum. Figure 4 (a) shows the electrochemical polarization curves of the catalyst in the hydrogen evolution reaction (HER). Figure 4 (b) corresponds to its electrochemical polarization curve in the oxygen evolution reaction (OER).

[0037] Figure 5 The LSV curves are obtained by depositing a self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst at different current densities. Figure 5 (a) shows the polarization curves of the electrochemical HER performance. Figure 5 (b) shows the polarization curves of the electrochemical OER performance.

[0038] Figure 6 The LSV curves are obtained from the deposition of a self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst at different deposition times. Figure 6 (a) shows the polarization curves of the electrochemical HER performance. Figure 6 (b) shows the polarization curves of the electrochemical OER performance.

[0039] Figure 7 LSV curves obtained for different substances and different molybdenum-cobalt ratios. Figure 7 (a) shows the polarization curves of the electrochemical HER performance. Figure 7 (b) shows the polarization curves of the electrochemical OER performance.

[0040] Figure 8 This is the LSV curve of the self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst prepared in Example 1 of this invention. Figure 8 (a) shows the HER performance polarization curves corrected for iR. Figure 8 (b) shows the OER performance polarization curve after iR correction.

[0041] Figure 9 This is the LSV curve of the self-supported lanthanum-molybdenum-cobalt-boron bifunctional catalyst prepared in Example 1 of this invention for the total water splitting.

[0042] Figure 10 This is the it curve of the complete water splitting of the self-supported lanthanum-molybdenum-cobalt-boron bifunctional catalyst prepared in Example 1 of this invention.

[0043] Figure 11 In Embodiment 1 of the present invention, the current density is 200 mA / s -1 The graph shows the changes in the amount of oxygen and hydrogen collected over time. Detailed Implementation

[0044] Example 1

[0045] (I) Preparation method

[0046] 1) Pretreatment of nickel foam: Cut 1mm thick nickel foam (NF) into 1cm×1cm pieces and ultrasonically clean them for 15 minutes each in acetone, anhydrous ethanol and deionized water at room temperature (power 500W) to remove grease, impurities and oxide layer from the surface of the nickel foam sample. Place the cleaned nickel foam sample in a vacuum drying oven and dry it at 50℃ for 12h.

[0047] 2) Preparation of electrodeposition solution: The solution is prepared according to the following concentrations: 0.005 mol / L lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and ammonium heptamolybdate ((NH4)6Mo7O) 24 0.1875 mol / L, cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O) 0.0625 mol / L, ammonium heptamolybdate ((NH4)6Mo7O) 24 Add 0.25 mol / L of cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O), then weigh out 0.5 mol / L of boric acid (H3BO3) and 0.3 mol / L of sodium citrate (C6O7H5Na3·2H2O), and then add 0.25 mol / L of sulfuric acid (H2SO4). Add all the reagents to 100 mL of deionized water and heat at 30 °C and 15 r / min until a transparent solution is obtained, which is the electrodeposition solution.

[0048] 3) Cleaning the nickel foam substrate: Clean the nickel foam treated in step 1) with 6 mol L... -1 The nickel foam sample was ultrasonically cleaned with hydrochloric acid solution at room temperature for 15 minutes (power 500W), and then repeatedly cleaned with a large amount of anhydrous ethanol and distilled water in an ultrasonic machine to remove residual hydrochloric acid on its surface. The cleaned nickel foam was quickly dried with a hair dryer and then immersed in electrodeposition solution for subsequent use.

[0049] 4) Preparation of a self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst by electrodeposition in a three-electrode system: Nickel foam was used as the working electrode, and carbon rods and Ag / AgCl electrodes were used as the counter and reference electrodes, respectively. The current density was set to -250 mA cm⁻¹. -2 Deposit at 30°C for 150 minutes.

[0050] 5) After electrodeposition, the surface of the nickel foam sample was rinsed with deionized water and dried in a vacuum drying oven at 30°C for 120 minutes to obtain a self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst.

[0051] Figure 1 SEM images of a self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst are shown at magnifications of 2K, 5K, and 10K. The images reveal a dense and smooth coating with a relatively rough surface. This structure enhances the adhesion between the coating and the substrate, resulting in improved catalytic performance.

[0052] Figure 2 The XRD pattern of the self-supported lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst is shown. The XRD pattern is in good agreement with Co (PDF#15-0806). The sample clearly shows three diffraction peaks, which are the (111), (200) and (220) crystal planes of Co, indicating that cobalt was successfully loaded onto nickel foam by electrodeposition. A broad peak is visible near 43°. The absence of crystal peaks of La2O3, Co2Mo and B suggests that they are blocked by the Co peak and the broad peak, indicating that the catalyst has formed a partially amorphous structure. The amorphous-crystalline combination forms a heterostructure, which improves the catalyst performance.

[0053] Figure 3 TEM images of the self-supported lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst are shown. The images display the low-magnification TEM morphology, high-resolution HRTEM image, selected area electron diffraction (SAED) pattern, and mapping diagrams of Mo, Co, B, and La. The images reveal the morphologies of amorphous Mo-B and La₂O₃, Co₂Mo₃, and B with clear lattice fringes. The SAED image clearly shows the diffraction rings of Co, La₂O₃, Co₂Mo₃, and B. The mapping diagrams further confirm the presence of Mo, Co, B, and La, demonstrating the successful preparation of the catalyst.

[0054] (II) Electrocatalytic performance testing

[0055] Electrocatalytic performance testing of the catalyst was conducted at room temperature and pressure in a three-electrode system. The electrolyte was 1 M KOH aqueous solution, the self-supported lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst was used as the working electrode, the carbon rod was used as the counter electrode, and the Hg / HgO electrode was used as the reference electrode.

[0056] Figure 4LSV curves were obtained from the deposition of a self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst at different lanthanum molar amounts to determine the optimal lanthanum molar amount for deposition. The curves showed that the HER performance was optimal at a lanthanum molar amount of 0.005 mol / L, with an HER overpotential of 95.9 mV. The OER performance was 396.1 mV at the same lanthanum molar amount, comparable to the optimal OER performance of 394.1 mV at 0.015 mol / L. Considering that a lanthanum molar amount of 0.005 mol / L requires less material and exhibits superior overall performance, the optimal performance (HER overpotential of 95.9 mV and OER overpotential of 396.1 mV) was determined at this lanthanum molar amount. Therefore, the electrodeposition current density was investigated at a lanthanum molar amount of 0.005 mol / L. The values ​​were -100 mA / cm². -2 -180mA cm -2 -250mA cm -2 and -300mA cm -2 .

[0057] Figure 5 LSV curves were obtained for the deposition of a self-supported lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst at different current densities to determine the optimal deposition current density. Based on the curves, it can be concluded that the optimal deposition current density is -250 mA cm⁻¹. -2 The HER performance was optimal, with an overpotential of 81.9 mV and an OER overpotential of 383.1 mV. This is comparable to the -300 mA cm⁻¹ performance of the OER. -2 The performance of OER at 377.1mV is comparable. This is because the electrodeposition current is -300mA cm⁻¹. -2 Higher energy consumption and deposition time of -250 mA / cm -2 It exhibits superior overall performance, therefore, it is suitable for applications with a lanthanum molar content of 0.005 mol / L and a current density of -250 mA cm⁻¹. -2 The deposition times were studied, specifically 5400s, 7200s, 9000s, and 10800s.

[0058] Figure 6 LSV curves of the self-supported lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst were obtained at different deposition times to determine the optimal deposition time. The curves show that the best performance is achieved at an electrodeposition time of 9000 s, with an HER overpotential of 42.2 mV and an OER overpotential of 354.1 mV. Therefore, the optimal deposition time is achieved when the lanthanum molar content is 0.005 mol / L and the current density is -250 mA cm⁻¹. -2Based on a deposition time of 9000 s, further research was conducted using different materials and different molybdenum-cobalt ion ratios as variables. The materials were Mo3Co1, with a molar ratio of molybdenum to cobalt ions of 3:1, and (Mo3Co1)La 0.02 The molar ratio of molybdenum ions to cobalt ions is 3:1, (Mo3Co1)B2; the molar ratio of molybdenum ions to cobalt ions is 3:1, (Mo5Co1)B2La. 0.02 The molar ratio of molybdenum ions to cobalt ions is 5:1, (Mo3Co1)B2La 0.02 The molar ratio of molybdenum ions to cobalt ions is 3:1 and (Mo1Co1)B2La 0.02 The molar ratio of molybdenum ions to cobalt ions is 1:1.

[0059] Figure 7 LSV curves were obtained for different substances and different molybdenum-cobalt ion ratios to determine the optimal substances and molybdenum-cobalt ion ratios for the overall water splitting catalyst. Based on the curves, it can be concluded that when the molybdenum ion:cobalt ion ratio is 3:1, the optimal ratio for (Mo3Co1)B2La is [value missing]. 0.02 The sample exhibited the best performance, with an HER overpotential of 51.9 mV and an OER overpotential of 308.8 mV. Therefore, the optimal sample for the lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst was determined.

[0060] Figure 8 The LSV curves of the self-supported lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst were used to characterize the catalytic activity of the sample. The test conditions were a three-electrode system: a Hg / HgO electrode as the reference electrode, a carbon rod as the counter electrode, and the sample as the working electrode. The electrolyte was a 1 MkOH aqueous solution. The graphs show that after 80% overpotential compensation, the catalyst operates at a current density of -10 mA cm⁻¹. -2 Under these conditions, the overpotential is 25.98 mV; at a current density of 10 mA cm⁻¹ -2 Under these conditions, the overpotential is 290.83 mV, lower than the overpotential of most existing electrode materials. A lower overpotential in water electrolysis indicates a higher total voltage required for electrolysis, a higher conversion efficiency of electrical energy to hydrogen energy, and a higher Faraday efficiency. Therefore, it has good commercial prospects.

[0061] Figure 9 This is the LSV curve of the self-supported lanthanum-molybdenum-cobalt-boron bifunctional catalyst prepared in Example 1 of this invention for the total water splitting. The image shows that at a current density of 10 mA cm⁻¹... -2 Under these conditions, the full cell voltage of the water-splitting process is 1.6V, and its performance is close to or even surpasses that of most existing electrode materials.

[0062] Figure 10This is the water splitting curve of the self-supported lanthanum-molybdenum-cobalt-boron bifunctional catalyst prepared in Example 1 of this invention. As can be seen from the figure, at a current density of 10 mA / cm²... -2 Under these conditions, the full-cell voltage of the fully hydrolyzed water remained stable at around 1.65V for 120 hours, indicating that the material has good stability.

[0063] Example 2

[0064] 1) A hydrogen / oxygen gas collection device was constructed using the water displacement method, and water electrolysis experiments were carried out in a constant current mode using an H-type electrolyzer in a dual-electrode system.

[0065] 2) Using the prepared (Mo3Co1)B2La 0.02 The electrodes served as the cathode and anode, respectively. Two 100mL graduated cylinders were filled with water, sealed with sealing film, inverted, and fixed to a large water-filled container with an iron stand. The sealing film was then removed underwater. Two thin tubes were connected to graduated cylinder No. 1 (cathode) and graduated cylinder No. 2 (anode) to collect the hydrogen and oxygen evolved during electrolysis, respectively. A stopwatch was fixed to one of the iron stands to accurately record the collection time.

[0066] 3) During the water electrolysis process, the electrodeposition conditions are set to a constant current density of 200 mA·s⁻ 1 Constant current electrolysis was performed at 25°C, and the time required to reach a specific gas volume was recorded. 50 mL of hydrogen and 25 mL of oxygen were collected separately. Based on the obtained gas volume-time relationship, the Faraday efficiency was calculated using the following formula:

[0067] FE = m / [(I × t) / (n × F)] = (m × n × F) / (I × t)

[0068] n = 4, F = 96,485 C mol -1 , I = 200 mA, and t = 1971 s.

[0069] Figure 11 It is a current density of 200 mA s -1 The graph shows the changes in the amount of oxygen and hydrogen collected over time. After 1971 s of water electrolysis, 50 mL of hydrogen and 25 mL of oxygen were collected. The calculated Faraday efficiency was 99.1%, indicating good conversion efficiency.

[0070] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst, characterized in that, The preparation method includes the following steps: 1) Pretreatment of nickel foam: Cut the nickel foam into small pieces, clean, dry, and clean with hydrochloric acid solution, ethanol, and deionized water, then air dry. 2) Preparation of electrodeposition solution: Lanthanum nitrate hexahydrate La(NO3)3·6H2O and ammonium heptamolybdate (NH4)6Mo7O 24 Cobalt acetate tetrahydrate Co(CH3COO)2·4H2O was dissolved in deionized water in a borate-citrate system, and then a small amount of sulfuric acid was added. The solution was heated at a constant temperature until it became a transparent solution, which was used as the electrodeposition solution. 3) A bifunctional lanthanum-molybdenum-cobalt-boron high-efficiency and stable total water splitting catalyst was prepared by constant current electrodeposition in a three-electrode system: using nickel foam as the working electrode, and carbon rod and Ag / AgCl electrode as the counter electrode and reference electrode, respectively, electrodeposition was performed, the sample surface was rinsed, and vacuum dried to obtain the bifunctional lanthanum-molybdenum-cobalt-boron high-efficiency and stable total water splitting catalyst.

2. The self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst according to claim 1, characterized in that, In step 2), lanthanum nitrate hexahydrate La(NO3)3·6H2O accounts for a portion of lanthanum nitrate hexahydrate La(NO3)3·6H2O and ammonium heptamolybdate (NH4)6Mo7O. 24 The total amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 is 0.5%-1%.

3. The self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst according to claim 1, characterized in that, In step 2), ammonium heptamolybdate (NH4)6Mo7O 24 The amount of substance is equal to that of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and ammonium heptamolybdate (NH4)6Mo7O. 24 The total amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 is 15%-30%.

4. The self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst according to claim 1, characterized in that, In step 2), the amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O accounts for a certain percentage of the amount of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and ammonium heptamolybdate (NH4)6Mo7O. 24 The total amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 is 5%-20%.

5. The self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst according to claim 1, characterized in that, In step 2), the amount of boric acid H3BO3 accounts for a certain percentage of the total amount of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and ammonium heptamolybdate (NH4)6Mo7O. 24 The total amount of cobalt acetate tetrahydrate Co(CH3COO)2·4H2O and boric acid H3BO3 is 60%-70%.

6. The self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst according to claim 1, characterized in that, The molar ratio of molybdenum ions to cobalt ions is 5:1 to 1:

1.

7. The self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water splitting catalyst according to claim 1, characterized in that, In step 3), the electrodeposition condition is that the current density is set to -300 to -200 mA cm⁻¹. -2 Deposit at 20-50℃ for 100-200 minutes.

8. The application of the self-supporting lanthanum-molybdenum-cobalt-boron bifunctional total water-splitting catalyst according to any one of claims 1-6 in water electrolysis.

9. The application according to claim 8, characterized in that, The method is as follows: the self-supporting lanthanum-molybdenum-cobalt-boron bifunctional water-splitting catalyst described in any one of claims 1-6 is used as the cathode and anode, respectively, for water electrolysis.

10. The application according to claim 9, characterized in that, The conditions for water electrolysis are a constant current density of 100-300 mA·s⁻ 1 Constant current electrolysis is performed within the temperature range of 20–50℃.

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