Three-dimensional self-supporting heterogeneous heterojunction electrocatalyst as well as preparation method and application thereof

Abstract

The invention provides a three-dimensional self-supporting heterogeneous heterojunction electrocatalyst and a preparation method and application thereof.The three-dimensional self-supporting heterogeneous heterojunction electrocatalyst comprises a conductive substrate and a CoMoS3. 13 / FeS2 / Co3S4 heterojunction nanosheet growing on the conductive substrate, and the CoMoS3. 13 / FeS2 / Co3S4 heterojunction nanosheet is composed of three components including CoMoS3. 13, FeS2 and Co3S4. The three-dimensional self-supporting heterogeneous heterojunction electrocatalyst provided by the invention has relatively good water electrolysis catalytic activity and cycling stability under an alkaline condition.

Description

Technical Field

[0001] The present invention relates to a three-dimensional self-supporting multiphase heterojunction electrocatalyst, a preparation method thereof, and an application thereof, belonging to the technical field of catalytic chemistry. Background Art

[0002] Currently, exploring clean and sustainable energy has become an inevitable necessity. Hydrogen energy is regarded as one of the cleanest energy sources with the greatest development potential in the future due to its environmental friendliness and high energy density, and electrocatalytic water splitting is an effective method for green production of hydrogen fuel. Generally, water splitting consists of two half-reactions, namely the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. However, the OER process involves multi-electron transfer, which usually limits the reaction rate. Therefore, it is necessary to design and develop suitable catalysts to improve the reaction rate.

[0003] Transition metal sulfides have become one of the most promising catalysts due to their high content in the earth's crust, low cost, and suitable catalytic efficiency. Among them, molybdenum-based sulfides have attracted wide attention in the field of energy storage and conversion due to their low cost, adjustable structure, and excellent performance. For water electrolysis, molybdenum-based sulfides are considered a promising catalyst due to their low price and rich reserves. However, the OER performance of molybdenum-based sulfides needs to be improved urgently, and single-component catalysts are difficult to meet the requirements of water electrolysis. Therefore, it is crucial to explore and improve the catalytic activity of molybdenum-based sulfides for hydrogen production by water electrolysis. Constructing heterojunctions can synergistically combine the characteristics and advantages of the two components at the interface, significantly changing the inherent catalytic properties of single-component molybdenum-based sulfides, so that the catalyst has unique physical and chemical properties for certain reactions, better optimizing the adsorption / desorption free energy of hydrogen and oxygen intermediates, and improving the energy conversion efficiency. The rich contact interfaces between molybdenum-based sulfides and another component can provide better electron conductivity and higher mechanical stability. The high contact interfaces lead to the formation of more charge and mass transfer channels, enabling good contact between the catalyst and the electrolyte.

[0004] CN113355692A discloses a preparation method of a molybdenum disulfide nanosheet@cobalt sulfide nanoparticle composite electrocatalyst. The preparation method includes: first, hydrothermally growing a Mo-S or Co-Mo-S nanosheet array on the surface of a substrate; then dissolving a cobalt salt in a volatile non-aqueous solvent and coating it on the surface of the Mo-S or Co-Mo-S nanosheet array; finally, placing the sample in an S atmosphere for in-situ deposition of cobalt sulfide nanoparticles. In alkaline, neutral, and acidic electrolytes at room temperature, the overpotential required to reach 10 mA cm -2 The overpotential required is around ~50 mV; for alkaline and acidic electrolytes, to reach 600 mA cm -2The required overpotential is around ~200 mV. This performance is very close to or even exceeds that of commercial Pt particles when operating at a large current density. For OER, in a room-temperature alkaline electrolyte, the overpotentials required to reach 10 mA cm -2 and 100 mA cm -2 are ~220 mV and ~330 mV respectively; however, the molybdenum disulfide nanosheet@cobalt sulfide nanoparticle composite electrocatalyst prepared by this method has fewer active sites, a slow ion transport rate, and a relatively high overpotential.

[0005] CN109019602A discloses a molybdenum carbide material, a molybdenum carbide@molybdenum sulfide composite material, and a preparation method and application thereof. First, a carbon source and a molybdenum source are added to a dispersion liquid and stirred for 6 - 12 h, then dried, ground, and collected at 80 - 120 °C to form a molybdenum carbide precursor; under an inert atmosphere, the molybdenum carbide precursor is heated from room temperature to 400 - 900 °C at a programmed rate and calcined at this temperature for 1 - 3 h, then ground and collected to obtain molybdenum carbide. The molybdenum carbide is sulfided at 160 - 400 °C using a sulfiding agent to obtain molybdenum carbide@molybdenum sulfide. Both the molybdenum carbide and the molybdenum carbide@molybdenum sulfide have a porous nanosheet-like structure morphology. This microstructure is beneficial for electrolyte storage to reduce charge transfer resistance and can also provide more electrocatalytic active sites; both can be used as HER electrocatalysts, with high catalytic activity and good stability, and are expected to replace Pt-based catalysts for electrolytic water hydrogen production. However, stacking during the formation of molybdenum carbide and molybdenum carbide@molybdenum sulfide will lead to a decrease in catalytic performance.

[0006] Therefore, providing a novel three-dimensional self-supporting multiphase heterojunction electrocatalyst and its preparation method and application has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the above-mentioned drawbacks and deficiencies, one object of the present invention is to provide a three-dimensional self-supporting multiphase heterojunction electrocatalyst.

[0008] Another object of the present invention is also to provide a preparation method for the above-mentioned three-dimensional self-supporting multiphase heterojunction electrocatalyst.

[0009] Yet another object of the present invention is also to provide the application of the above-mentioned three-dimensional self-supporting multiphase heterojunction electrocatalyst in catalytic electrolytic water hydrogen production.

[0010] To achieve the above objects, on the one hand, the present invention provides a three-dimensional self-supporting multiphase heterojunction electrocatalyst, wherein the three-dimensional self-supporting multiphase heterojunction electrocatalyst includes a conductive substrate and CoMoS 3.13 / FeS 2 / Co 3 S 4Heterojunction nanosheets, the CoMoS 3.13 / FeS 2 / Co 3 S 4 Heterojunction nanosheets made of CoMoS 3.13 , FeS 2 and Co 3 S 4 Consists of three components.

[0011] As a specific embodiment of the above catalyst of the present invention, wherein the CoMoS 3.13 / FeS 2 / Co 3 S 4 The heterojunction nanosheets are staggeredly grown on the conductive substrate and in the staggered growth process, the CoMoS 3.13 / FeS 2 / Co 3 S 4 A pore structure is formed between the heterojunction nanosheets.

[0012] As a specific embodiment of the above catalyst of the present invention, wherein the CoMoS 3.13 / FeS 2 / Co 3 S 4 The size of the heterojunction nanosheets is 500-700nm.

[0013] As a specific embodiment of the above catalyst of the present invention, wherein the conductive substrate comprises a carbon support or nickel foam;

[0014] Preferably, the carbon carrier comprises carbon paper or carbon cloth.

[0015] The present invention introduces a conductive substrate such as a carbon carrier and nickel foam (NF) into the electrocatalyst, that is, a molybdenum-based catalyst (CoMoS 3.13 / FeS 2 / Co 3 S 4 Heterojunction nanosheets) combined with a conductive substrate can achieve rapid mass diffusion, which can not only enhance the electrical contact between the conductive substrate and the sulfide, improve the conductivity of the electrocatalyst, and accelerate the electron and ion transport, but also effectively promote the uniform dispersion of the sulfide, reduce its self-accumulation and agglomeration, thereby significantly reducing the overpotential under high current density and improving the electrocatalyst's water electrolysis catalytic performance and durability.

[0016] On the other hand, the present invention also provides a method for preparing the above-mentioned three-dimensional self-supporting multiphase heterojunction electrocatalyst, wherein the preparation method comprises:

[0017] Step (1): Dissolve a molybdenum source, an iron source, and a precipitant in deionized water to obtain solution A, dissolve a cobalt source and a morphology regulator in deionized water to obtain solution B, mix solution A, solution B, and an acid-treated conductive substrate, and then carry out a hydrothermal reaction. After the hydrothermal reaction is completed, an FeCoMo precursor supported on the conductive substrate is obtained.

[0018] Step (2): Dissolve a sulfur source in deionized water to obtain solution C, mix solution C and the FeCoMo precursor supported on the conductive substrate, and then carry out a sulfidation reaction. After the sulfidation reaction is completed, the three-dimensional self-supporting heterophase junction electrocatalyst is obtained.

[0019] In the above preparation method, the molybdenum source, the iron source, and the cobalt source react to form an FeCoMo precursor supported on the conductive substrate, and then a sulfur source is added for sulfidation to form the three-dimensional self-supporting heterophase junction electrocatalyst.

[0020] As a specific embodiment of the above preparation method of the present invention, in solution A, the molar ratio of the molybdenum source, the iron source, and the precipitant is 1:1:3 - 1:1.2:4, and in solution B, the molar ratio of the cobalt source and the morphology regulator is 1:1 - 3:1.

[0021] The present invention does not make specific requirements on the specific substances of the precipitant and the morphology regulator, and can be reasonably selected according to the actual on-site operation needs. For example, in some embodiments of the present invention, the precipitant can be urea, etc., and the morphology regulator can be ammonium fluoride, etc.

[0022] As a specific embodiment of the above preparation method of the present invention, the molybdenum source includes ammonium molybdate tetrahydrate and / or sodium molybdate, etc., the iron source includes ferrous sulfate heptahydrate and / or ferric nitrate nonahydrate, etc., and the cobalt source includes cobalt nitrate hexahydrate and / or cobalt sulfate, etc.

[0023] As a specific embodiment of the above preparation method of the present invention, in step (1), pour solution B into solution A under stirring conditions and continue stirring to obtain a mixed solution, and then mix the mixed solution with the acid-treated conductive substrate. For example, the acid-treated conductive substrate can be immersed in the mixed solution. The present invention does not make specific requirements on the continuous stirring time, and can be reasonably adjusted according to the actual on-site operation needs. For example, in some embodiments of the present invention, the stirring can be strong stirring for 1 h.

[0024] As a specific embodiment of the above preparation method of the present invention, the acid treatment of the conductive substrate includes: first immerse the conductive substrate in a concentrated nitric acid solution and then carry out ultrasonic treatment, then wash it with water until the pH value is 6.5 - 7, clean it with ethanol, and finally carry out a drying treatment.

[0025] The present invention does not make specific requirements for the ultrasonic time and drying temperature after immersing the conductive substrate in the concentrated nitric acid solution, and can be reasonably adjusted according to the actual on-site operation needs. For example, in some embodiments of the present invention, the ultrasonic time can be 30 min, and the drying temperature is 60 °C.

[0026] The present invention performs acid treatment on the conductive substrate. On the one hand, the acid treatment can remove impurities such as oxides on the surface of the conductive substrate. On the other hand, after the acid treatment of the conductive substrate, more anchor points will be generated on its surface, which is beneficial to the in-situ growth of the catalyst and can increase the wettability of the conductive substrate, thereby effectively improving the activity of the catalyst.

[0027] As a specific embodiment of the above-mentioned preparation method of the present invention, wherein, the temperature of the hydrothermal reaction is 130-150 °C, and the time is 5-7 h.

[0028] As a specific embodiment of the above-mentioned preparation method of the present invention, wherein, the molar ratio of the molybdenum source, iron source, cobalt source and sulfur source is 1:1:1:1.2-1:1.2:2.3:2.

[0029] As a specific embodiment of the above-mentioned preparation method of the present invention, wherein, based on the total volume of deionized water contained in solution C, the concentration of the sulfur source is 0.04-0.06 mol / L.

[0030] As a specific embodiment of the above-mentioned preparation method of the present invention, wherein, the sulfur source includes one or a combination of several of thioacetamide, L-cysteine, thiourea, sodium sulfide, etc.

[0031] As a specific embodiment of the above-mentioned preparation method of the present invention, wherein, the temperature of the sulfidation reaction is 150-170 °C, and the time is 3-5 h.

[0032] As a specific embodiment of the above-mentioned preparation method of the present invention, wherein, step (1) further includes ultrasonic washing and drying of the hydrothermal reaction product, and step (2) further includes ultrasonic washing and drying of the sulfidation reaction product;

[0033] Among them, the ultrasonic washing is sequentially carried out in deionized water and ethanol. The present invention does not make specific requirements for the ultrasonic washing time, the drying temperature and drying time in step (1) and step (2), etc., and can be reasonably adjusted according to the actual on-site operation needs. For example, in some embodiments of the present invention, the hydrothermal reaction product or the sulfidation reaction product can be ultrasonically washed in deionized water and ethanol for 10 min each, and the drying in step (1) and step (2) can both be drying at 60 °C for 12 h.

[0034] On the other hand, the present invention also provides the application of the above-mentioned three-dimensional self-supporting heterophase heterojunction electrocatalyst in catalytic electrolytic water for hydrogen production.

[0035] Compared with the prior art, the beneficial technical effects that the present invention can achieve include:

[0036] The three-dimensional self-supporting heterophase heterojunction electrocatalyst provided by the present invention is obtained by self-assembling nanosheets on a conductive substrate, so that it has the high specific surface area advantage of the unique self-assembled nanosheets, and there is a synergistic effect among Fe, Co, Mo and S in the electrocatalyst, so that the electrocatalyst exhibits good electrocatalytic activity and stability for HER in an alkaline medium (such as 1 M KOH, pH = 14). In addition, the present invention introduces FeS 3.13 into the bimetallic CoMoS 2 sulfide and Co 3 S 4 , and the heterointerfacial structure can be regulated through the electronic interaction among the three. The presence of Fe and Co can also weaken the adsorption free energy of the *OOH intermediate during the OER process of molybdenum-based sulfide and promote the rapid formation of the O-O bond.

[0037] The three-dimensional self-supporting heterophase electrocatalyst provided by the present invention is obtained by self-assembling nanosheets on a conductive substrate, which can ensure the uniform growth of the nanosheet structure, thereby increasing the electrochemically active surface area, increasing the number of active centers, accelerating ion diffusion and electron transfer, maintaining the structural integrity of the catalyst, and inhibiting the aggregation of active species during the electrolysis process, which helps to improve the catalytic performance of water electrolysis, that is, the electrocatalyst has good water electrolysis performance under alkaline conditions.

[0038] In addition, the preparation method of the electrocatalyst provided by the present invention has simple process and mild conditions, and is suitable for large-scale production. Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0040] Figure 1 SEM image of the three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst provided in Embodiment 1 of the present invention.

[0041] Figure 2The three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst and the XRD patterns of FeCoS / CP, CoMoS / CP, and FeMoS / CP provided in Comparative Example 1 - Comparative Example 3.

[0042] Figure 3 SEM image of FeCoS / CP provided in Comparative Example 1.

[0043] Figure 4 SEM image of CoMoS / CP provided in Comparative Example 2.

[0044] Figure 5 SEM image of FeMoS / CP provided in Comparative Example 3.

[0045] Figure 6 The three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 High-magnification transmission electron microscope image of the heterojunction electrocatalyst.

[0046] Figure 7 The three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 Electrocatalytic hydrogen evolution / HER catalytic performance graph of the heterojunction electrocatalyst.

[0047] Figure 8 The three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 Electrolytic water performance graph of the heterojunction electrocatalyst.

[0048] Figure 9 The three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 Cyclic stability graph of the heterojunction electrocatalyst at a current density of 10 mA cm -2 for 24 h. Detailed implementation mode

[0049] It should be noted that the term "comprising" in the description, claims and above-mentioned drawings of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0050] The "scope" disclosed in the present invention is given in the form of a lower limit and an upper limit. There may be one or more lower limits, and one or more upper limits respectively. A given scope is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundary of a particular scope. All scopes defined in this way are combinable, that is, any lower limit can be combined with any upper limit to form a scope. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values listed are 1 and 2, and the maximum range values listed are 3, 4 and 5, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4 and 2 - 5.

[0051] In the present invention, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed in the present invention, and "0 - 5" is only an abbreviated representation of these numerical combinations.

[0052] In the present invention, if there is no special instruction, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0053] In the present invention, if there is no special instruction, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0054] In the present invention, if there is no special instruction, all steps mentioned herein can be carried out in sequence or randomly, but preferably in sequence. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out in sequence, or may also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0055] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the attached tables, drawings and embodiments. The following described embodiments are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to illustrate the present invention, and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0056] The sources of raw materials and equipment used in the embodiments of the present invention, including information such as the names, specifications, and manufacturers of raw materials and equipment, are shown in Table 1 and Table 2 below.

[0057] Table 1 Raw material source information

[0058] Reagent Name Reagent Purity Manufacturer Ferrous Sulfate Heptahydrate AR Sinopharm Chemical Reagent Co., Ltd. Ammonium Molybdate Tetrahydrate AR Sinopharm Chemical Reagent Co., Ltd. Absolute Ethanol AR Sinopharm Chemical Reagent Co., Ltd. Urea AR Sinopharm Chemical Reagent Co., Ltd. Ammonium Fluoride AR Sinopharm Chemical Reagent Co., Ltd. Thioacetamide AR Sinopharm Chemical Reagent Co., Ltd. Polytetrafluoroethylene AR Sinopharm Chemical Reagent Co., Ltd. Potassium Hydroxide AR Sinopharm Chemical Reagent Co., Ltd. 5wt% Nafion AR Sinopharm Chemical Reagent Co., Ltd. Deionized Water Self-made —

[0059] Table 2 Main instruments and equipment

[0060]

[0061]

[0062] Example 1

[0063] This example provides a three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst, which is prepared by a preparation method including the following specific steps:

[0064] Step (1): Preparation of FeCoMo precursor supported on carbon paper, that is, preparation of FeCoMo precursor supported on carbon paper:

[0065] A commercial hydrophilic carbon paper (CP, with a size of 1 cm × 2 cm) was immersed in a concentrated nitric acid solution and sonicated for 30 min, then washed with water until neutral, cleaned with ethanol, and dried at 60 °C for standby. Weigh 1.8 mmol of ammonium molybdate tetrahydrate, 2 mmol of ferrous sulfate heptahydrate, and 6 mmol of urea and dissolve them in 30 mL of deionized water to obtain solution A. Separately, weigh 4 mmol of cobalt nitrate hexahydrate and 2 mmol of ammonium fluoride and dissolve them in 30 mL of deionized water to obtain solution B. Under stirring conditions, pour solution B into solution A and continue to stir strongly for 1 h to obtain a mixed solution. Take the treated CP, immerse it in the mixed solution, and transfer it to a 100 mL autoclave for hydrothermal reaction. This hydrothermal reaction is carried out at 140 °C for 6 h. After naturally cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn, and then dry it at 60 °C for 12 h to obtain the carbon paper supported FeCoMo precursor, denoted as FeCoMo-P / CP precursor;

[0066] Step (2): Preparation of three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 Preparation of heterojunction electrocatalyst:

[0067] Dissolve 2.5 mmol of thioacetamide in 50 mL of deionized water and stir for 10 min to obtain solution C. Transfer the above solution C to a 100 mL autoclave, and immerse the FeCoMo-P / CP precursor in it. Then react the mixture at 160 °C for 4 h. After cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn to obtain CoMoS 3.13 / FeS 2 / Co 3 S 4 / CP, and then dry it at 60 °C for 12 h to obtain the three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst, denoted as FeCoMoS / CP.

[0068] Example 2

[0069] The example provides a three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst, which is prepared by a preparation method including the following specific steps:

[0070] Step (1): Preparation of carbon paper supported FeCoMo precursor, that is, preparation of FeCoMo precursor supported on carbon paper:

[0071] A commercial hydrophilic carbon paper (CP, with a size of 1 cm × 2 cm) was immersed in a concentrated nitric acid solution and ultrasonicated for 30 min, then washed with water until neutral, cleaned with ethanol, and dried at 60 °C for standby. Weigh 1.8 mmol of ammonium molybdate tetrahydrate, 2 mmol of ferrous sulfate heptahydrate, and 6 mmol of urea and dissolve them in 30 mL of deionized water to obtain solution A. Separately, weigh 4 mmol of cobalt nitrate hexahydrate and 2 mmol of ammonium fluoride and dissolve them in 30 mL of deionized water to obtain solution B. Under stirring conditions, pour solution B into solution A and continue to stir strongly for 1 h to obtain a mixed solution. Take the treated CP, immerse it in the mixed solution, and transfer it to a 100 mL reaction kettle for hydrothermal reaction. This hydrothermal reaction is carried out at 140 °C for 6 h. After naturally cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn, and then dry it at 60 °C for 12 h to obtain the carbon paper supported FeCoMo precursor, denoted as FeCoMo-P / CP precursor;

[0072] Step (2): Preparation of the three-dimensional self-supporting heterojunction electrocatalyst:

[0073] Dissolve 2 mmol of thioacetamide in 50 mL of deionized water and stir for 10 min to obtain solution C. Transfer the above solution C to a 100 mL reaction kettle, and immerse the FeCoMo-P / CP precursor in it. Then react the mixture at 160 °C for 4 h. After cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn, and then dry it at 60 °C for 12 h to obtain the three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst.

[0074] Example 3

[0075] This example provides a three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst, which is prepared by a preparation method including the following specific steps:

[0076] Step (1): Preparation of the carbon paper supported FeCoMo precursor, that is, the preparation of the FeCoMo precursor supported on the carbon paper:

[0077] A commercial hydrophilic carbon paper (CP, with a size of 1 cm × 2 cm) was immersed in a concentrated nitric acid solution and ultrasonically treated for 30 min, then washed with water until neutral, cleaned with ethanol, and dried at 60 °C for standby. Weigh 1.8 mmol of ammonium molybdate tetrahydrate, 2 mmol of ferrous sulfate heptahydrate, and 6 mmol of urea and dissolve them in 30 mL of deionized water to obtain solution A. Separately, weigh 4 mmol of cobalt nitrate hexahydrate and 2 mmol of ammonium fluoride and dissolve them in 30 mL of deionized water to obtain solution B. Under stirring conditions, pour solution B into solution A and continue to stir strongly for 1 h to obtain a mixed solution. Take the treated CP, immerse it in the mixed solution, and transfer it to a 100 mL autoclave for hydrothermal reaction. This hydrothermal reaction is carried out at 140 °C for 6 h. After naturally cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn, and then dry it at 60 °C for 12 h to obtain the carbon paper supported FeCoMo precursor, denoted as FeCoMo-P / CP precursor;

[0078] Step (2): Preparation of the three-dimensional self-supporting heterojunction electrocatalyst:

[0079] Dissolve 3 mmol of thioacetamide in 50 mL of deionized water and stir for 10 min to obtain solution C. Transfer the above solution C to a 100 mL autoclave, and immerse the FeCoMo-P / CP precursor in it. Then react the mixture at 160 °C for 4 h. After cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn, and then dry it at 60 °C for 12 h to obtain the three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst.

[0080] Example 4

[0081] The example provides a three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst, which is prepared by a preparation method including the following specific steps:

[0082] Step (1): Preparation of the carbon paper supported FeCoMo precursor, that is, the preparation of the FeCoMo precursor supported on the carbon paper:

[0083] A commercial hydrophilic carbon paper (CP, with a size of 1 cm × 2 cm) was immersed in a concentrated nitric acid solution and ultrasonically treated for 30 min, then washed with water until neutral, cleaned with ethanol, and dried at 60 °C for later use. Weigh 1.8 mmol of ammonium molybdate tetrahydrate, 2 mmol of ferrous sulfate heptahydrate, and 6 mmol of urea and dissolve them in 30 mL of deionized water to obtain solution A. Separately, weigh 4 mmol of cobalt nitrate hexahydrate and 2 mmol of ammonium fluoride and dissolve them in 30 mL of deionized water to obtain solution B. Under stirring conditions, pour solution B into solution A and continue to stir vigorously for 1 h to obtain a mixed solution. Take the treated CP, immerse it in the mixed solution, and transfer it to a 100 mL reaction kettle for hydrothermal reaction. This hydrothermal reaction is carried out at 140 °C for 6 h. After natural cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn, and then dry it at 60 °C for 12 h to obtain the carbon paper supported FeCoMo precursor, denoted as FeCoMo-P / CP precursor;

[0084] Step (2): Preparation of a three-dimensional self-supporting heterojunction electrocatalyst:

[0085] Dissolve 2.5 mmol of thiourea in 50 mL of deionized water and stir for 10 min to obtain solution C. Transfer the above solution C to a 100 mL reaction kettle and immerse the FeCoMo-P / CP precursor in it. Then react the mixture at 160 °C for 4 h. After cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn, and then dry it at 60 °C for 12 h to obtain the three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst.

[0086] Example 5

[0087] The example provides a three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst, which is prepared by a preparation method including the following specific steps:

[0088] Step (1): Preparation of a carbon paper supported FeCoMo precursor, that is, the preparation of the FeCoMo precursor supported on carbon paper:

[0089] A commercial hydrophilic carbon paper (CP, with a size of 1 cm × 2 cm) was immersed in a concentrated nitric acid solution and ultrasonicated for 30 min, then washed with water until neutral, cleaned with ethanol, and dried at 60 °C for later use. Weigh 1.8 mmol of ammonium molybdate tetrahydrate, 2 mmol of ferrous sulfate heptahydrate, and 6 mmol of urea and dissolve them in 30 mL of deionized water to obtain solution A. Separately, weigh 4 mmol of cobalt nitrate hexahydrate and 2 mmol of ammonium fluoride and dissolve them in 30 mL of deionized water to obtain solution B. Under stirring conditions, pour solution B into solution A and continue to stir strongly for 1 h to obtain a mixed solution. Take the treated CP, immerse it in the mixed solution, and transfer it to a 100 mL autoclave for hydrothermal reaction. This hydrothermal reaction is carried out at 140 °C for 6 h. After naturally cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn, and then dry it at 60 °C for 12 h to obtain the carbon paper supported FeCoMo precursor, denoted as FeCoMo-P / CP precursor;

[0090] Step (2): Preparation of the three-dimensional self-supporting heterojunction electrocatalyst:

[0091] Dissolve 2.5 mmol of L-cysteine in 50 mL of deionized water and stir for 10 min to obtain solution C. Transfer the above solution C to a 100 mL autoclave, and immerse the FeCoMo-P / CP precursor in it. Then react the mixture at 160 °C for 4 h. After cooling to room temperature, ultrasonically wash it in deionized water and ethanol for 10 min each in turn, and then dry it at 60 °C for 12 h to obtain the three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst.

[0092] Example 6

[0093] The example provides a three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst, which is prepared by a preparation method including the following specific steps:

[0094] Step (1): Preparation of the carbon paper supported FeCoMo precursor, that is, the preparation of the FeCoMo precursor supported on the carbon paper:

[0095] A commercial hydrophilic carbon paper (CP, with a size of 1 cm × 2 cm) was immersed in a concentrated nitric acid solution and sonicated for 30 min, then washed with water until neutral, cleaned with ethanol, and dried at 60 °C for standby. Weigh 1.8 mmol of ammonium molybdate tetrahydrate, 2 mmol of ferrous sulfate heptahydrate, and 6 mmol of urea and dissolve them in 30 mL of deionized water to obtain solution A. Separately, weigh 4 mmol of cobalt nitrate hexahydrate and 2 mmol of ammonium fluoride and dissolve them in 30 mL of deionized water to obtain solution B. Under stirring conditions, pour solution B into solution A and continue to stir vigorously for 1 h to obtain a mixed solution. Take the treated CP, immerse it in the mixed solution, and transfer it to a 100 mL autoclave for hydrothermal reaction. This hydrothermal reaction was carried out at 140 °C for 6 h. After naturally cooling to room temperature, it was ultrasonically washed in deionized water and ethanol for 10 min each, and then dried at 60 °C for 12 h to obtain the carbon paper supported FeCoMo precursor, denoted as FeCoMo-P / CP precursor;

[0096] Step (2): Preparation of three-dimensional self-supporting heterojunction electrocatalyst:

[0097] Dissolve 2.5 mmol of sodium sulfide in 50 mL of deionized water and stir for 10 min to obtain solution C. Transfer the above solution C to a 100 mL autoclave, and immerse the FeCoMo-P / CP precursor in it. Then the mixture was reacted at 160 °C for 4 h. After cooling to room temperature, it was ultrasonically washed in deionized water and ethanol for 10 min each, and then dried at 60 °C for 12 h to obtain the three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst.

[0098] Comparative Example 1

[0099] This comparative example provides a carbon paper supported FeS 2 / Co 3 S 4 heterojunction electrocatalyst, which is prepared by a preparation method including the following specific steps:

[0100] Step (1): Preparation of carbon paper supported FeCo precursor:

[0101] A commercial hydrophilic carbon paper (CP, with a size of 1 cm × 2 cm) was immersed in a concentrated nitric acid solution and ultrasonicated for 30 min, then washed with water until neutral, cleaned with ethanol, and dried at 60 °C for later use. Weigh 2 mmol of ferrous sulfate heptahydrate and 6 mmol of urea and dissolve them in 30 mL of deionized water to obtain solution A. Separately, weigh 4 mmol of cobalt nitrate hexahydrate and 2 mmol of ammonium fluoride and dissolve them in 30 mL of deionized water to obtain solution B. Under stirring conditions, pour solution B into solution A and continue to stir strongly for 1 h to obtain a mixed solution. Take the treated CP, immerse it in the mixed solution, and transfer it to a 100 mL autoclave for hydrothermal reaction. This hydrothermal reaction is carried out at 140 °C for 6 h. After naturally cooling to room temperature, wash it alternately with deionized water and ethanol under ultrasonic waves (each ultrasonic washing for 10 min), and then dry it at 60 °C for 12 h to obtain the carbon paper supported FeCo precursor, denoted as FeCo-P / CP precursor;

[0102] Step (2): Preparation of carbon paper supported FeS 2 / Co 3 S 4 Preparation of the heterojunction electrocatalyst:

[0103] Dissolve 2.5 mmol of thioacetamide in 50 mL of deionized water and stir for 10 min to obtain solution C. Transfer the above solution C to a 100 mL autoclave, and immerse the FeCo-P / CP precursor in it. Then react the mixture at 160 °C for 4 h. After cooling to room temperature, wash it ultrasonically for 10 min each in deionized water and ethanol in turn, and finally dry it at 60 °C for 12 h to obtain the carbon paper supported FeS 2 / Co 3 S 4 heterojunction electrocatalyst, denoted as FeCoS / CP.

[0104] Comparative Example 2

[0105] This comparative example provides a carbon paper supported CoMoS 3.13 / Co 3 S 4 heterojunction electrocatalyst, which is prepared by a preparation method including the following specific steps:

[0106] Step (1): Preparation of carbon paper supported CoMo precursor, that is, the preparation of CoMo precursor supported on carbon paper:

[0107] A commercial hydrophilic carbon paper (CP, with a size of 1 cm × 2 cm) was immersed in a concentrated nitric acid solution and ultrasonically treated for 30 min, then washed with water until neutral, cleaned with ethanol, and dried at 60 °C for later use. Weigh 1.8 mmol of ammonium molybdate tetrahydrate and 6 mmol of urea and dissolve them in 30 mL of deionized water to obtain solution A. Separately, weigh 4 mmol of cobalt nitrate hexahydrate and 2 mmol of ammonium fluoride and dissolve them in 30 mL of deionized water to obtain solution B. Under stirring conditions, pour solution B into solution A and continue to stir vigorously for 1 h to obtain a mixed solution. Take the treated CP and immerse it in the mixed solution, then transfer it to a 100 mL autoclave for hydrothermal reaction. This hydrothermal reaction is carried out at 140 °C for 6 h. After naturally cooling to room temperature, wash it alternately with deionized water and ethanol under ultrasonic waves (each washing for 10 min), and then dry it at 60 °C for 12 h to obtain the carbon paper supported CoMo precursor, denoted as CoMo-P / CP precursor;

[0108] Step (2): Preparation of carbon paper supported CoMoS 3.13 / Co 3 S 4 Preparation of CoMoS / CoS heterojunction electrocatalyst:

[0109] Dissolve 2.5 mmol of thioacetamide in 50 mL of deionized water and stir for 10 min to obtain solution C. Transfer the above solution C to a 100 mL autoclave, and immerse the CoMo-P / CP precursor in it. Then react the mixture at 160 °C for 4 h. After cooling to room temperature, wash it ultrasonically for 10 min each in deionized water and ethanol in sequence, and finally dry it at 60 °C for 12 h to obtain the carbon paper supported CoMoS 3.13 / Co 3 S 4 heterojunction electrocatalyst, denoted as CoMoS / CP.

[0110] Comparative Example 3

[0111] This comparative example provides a carbon paper supported MoS 3.13 / FeS 2 heterojunction electrocatalyst, which is prepared by a preparation method including the following specific steps:

[0112] Step (1): Preparation of carbon paper supported FeMo precursor:

[0113] Commercial hydrophilic carbon paper (CP, size 1cm×2cm) was immersed in concentrated nitric acid solution and ultrasonically treated for 30 minutes, then washed with water until neutral, washed with ethanol and dried at 60°C for use. 1.8mmol of ammonium molybdate tetrahydrate, 2mmol of ferrous sulfate heptahydrate and 6mmol of urea were weighed and dissolved in 30mL of deionized water to obtain solution A. 2mmol of ammonium fluoride was weighed and dissolved in 30mL of deionized water to obtain solution B. Solution B was poured into solution A under stirring and continued to stir vigorously for 1h to obtain a mixed solution. The treated CP was immersed in the mixed solution and transferred to a 100mL reactor for hydrothermal reaction, which was reacted at 140°C for 6h. After naturally cooling to room temperature, it was alternately washed with deionized water and ethanol under ultrasonic wave (10min each), and then dried at 60°C for 12h to obtain the carbon paper-loaded FeMo precursor, recorded as FeMo-P / CP precursor;

[0114] Step (2): Carbon paper loaded with MoS 3.13 / FeS 2 Preparation of heterojunction electrocatalysts:

[0115] 2.5mmol of thioacetamide was dissolved in 50mL of deionized water and stirred for 10min to obtain solution C. The above solution C was transferred to a 100mL reactor and the FeMo-P / CP precursor was immersed in it. The mixture was then reacted at 160℃ for 4h, cooled to room temperature, and then ultrasonically washed in deionized water and ethanol for 10min each, and finally dried at 60℃ for 12h to obtain carbon paper loaded with MoS 3.13 / FeS 2 Heterojunction electrocatalyst, denoted as FeMoS / CP.

[0116] Characterization Test Example 1

[0117] In this characterization test example, SEM analysis was performed on the FeCoMoS / CP provided in Example 1 of the present invention and the FeCoS / CP, CoMoS / CP and FeMoS / CP provided in Comparative Examples 1 to 3, and the obtained SEM images were as follows: Figure 1 and Figures 3 - 5 As shown. Figure 1 It can be seen that the FeCoMoS / CP provided in Example 1 of the present invention is composed of thin and uniform nanosheets with a size of about 500 nm. The nanosheets grow in an interlaced manner to form a flower-like structure and have a large number of pores. The large number of pores can provide abundant ion diffusion channels and electrode / electrolyte contact interfaces for rapid catalytic kinetics, which is beneficial to the catalytic reaction. In contrast, the FeCoS / CP provided in Comparative Example 1 shows agglomerated and unevenly distributed nanoparticles on CP ( Figure 3), the CoMoS / CP provided by Comparative Example 2 mainly consists of dense nanoparticles anchored on CP ( Figure 4 ), the FeMoS / CP provided by Comparative Example 3 has a flower-like aggregate of nanosheets with different sizes ( Figure 5 ), comparison Figure 1 and Figures 3 - 5 It can be seen that the reasonable coupling of Fe, Co and Mo in the present invention can endow FeCoMoS / CP with a clear microstructure.

[0118] Characterization Test Example 2

[0119] In this characterization test example, XRD analysis was performed on the FeCoMoS / CP provided in Example 1 of the present invention and the FeCoS / CP, CoMoS / CP and FeMoS / CP provided in Comparative Examples 1-3, and the obtained XRD patterns are as Figure 2 shown. From the Figure 2 XRD pattern shown, all the diffraction peaks of the FeCoMoS / CP catalyst provided in Example 1 of the present invention correspond to Co 3 S 4 (PDF#42-1448), FeS 2 (PDF#42-1340) and CoMoS 3.13 (PDF#16-0439), proving that CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst was obtained.

[0120] Characterization Test Example 3

[0121] In this characterization test example, high-magnification transmission electron microscopy analysis was performed on the FeCoMoS / CP provided in Example 1 of the present invention, and the obtained high-magnification transmission electron microscopy images are as Figure 6 shown. From Figure 6 it can be seen that the HRTEM images of this FeCoMoS / CP show different lattice spacings of 0.167, 0.197 and 0.306 nm, which can be attributed to Co 3 S 4 (440), CoMoS 3.13 and FeS 2 (311) crystal planes, indicating that CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction structure was successfully synthesized in Example 1 of the present invention, that is, CoMoS 3.13 , FeS 2 and Co 3 S4 A heterojunction structure is formed therebetween.

[0122] Performance test example 1

[0123] In this performance test example, the HER catalytic performances of FeCoMoS / CP, FeCoS / CP, CoMoS / CP and FeMoS / CP were respectively tested. The test method included: at room temperature, using a Chenhua workstation (CHI 760E) in a standard three-electrode system, with a mercury / mercuric oxide electrode and a graphite rod as the reference electrode and the counter electrode respectively, and using FeCoMoS / CP, FeCoS / CP, CoMoS / CP and FeMoS / CP as the working electrodes respectively, and 1M KOH (pH = 14) as the electrolyte.

[0124] This performance test example also tested the water electrolysis catalytic performance of FeCoMoS / CP. The test method included: in a two-electrode system, assembling FeCoMoS / CP as the cathode and the anode into an electrolytic cell respectively, and testing its water electrolysis performance in 1M KOH.

[0125] In this performance test example, linear sweep voltammetry (LSV) was used to test the HER and water electrolysis catalytic performances of FeCoMoS / CP, FeCoS / CP, CoMoS / CP and FeMoS / CP respectively at a scan rate of 5 mV / s. The obtained experimental results are as Figures 7 - 9 shown in Table 3.

[0126] Figure 7 This is the HER catalytic performance diagram of the three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst provided in Example 1 of the present invention, that is, FeCoMoS / CP. It can be seen from Figure 7 that this electrocatalyst has good catalytic activity. In the HER reaction, the overpotential is 280 mV at a current density of 20 mA cm -2 .

[0127] Figure 8 This is the water electrolysis performance diagram of the three-dimensional self-supporting CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst provided in Example 1 of the present invention, that is, FeCoMoS / CP. It can be seen from Figure 8 that this electrocatalyst has good water electrolysis catalytic activity. In the water electrolysis reaction, its potential at a current density of 10 mA cm -2 is only 1.48 V.

[0128] Figure 9 The three-dimensional self-supported CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction electrocatalyst, that is, the cyclic stability diagram of FeCoMoS / CP at a current density of 10 mA cm -2 . It can be seen from Figure 9 that the performance of this electrocatalyst shows basically no decay after 24 h of testing, indicating its good cyclic stability.

[0129] Table 3

[0130] Catalyst Source <![CDATA[Overpotential / mV at a current density of 20 mA cm -2 > FeCoMoS / CP Example 1 280 FeCoS / CP Comparative Example 1 366 CoMoS / CP Comparative Example 2 329 FeMoS / CP Comparative Example 3 386

[0131] It can be seen from Table 3 that compared with the electrocatalysts provided in Comparative Examples 1-3, the electrocatalyst provided in Example 1 of the present invention has the lowest overpotential at a current density of 20 mA cm -2 , indicating its better catalytic activity.

[0132] As mentioned above, the above are only specific embodiments of the present invention, and the scope of the invention implementation cannot be limited by them. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the scope of the invention patent protection of the present invention, should still fall within the scope covered by this patent. In addition, the technical features in the present invention, between technical features, between technical features and technical inventions, and between technical inventions can be freely combined and used.

Claims

1. A three-dimensional self-supporting multiphase heterojunction electrocatalyst, characterized in that, The three-dimensional self-supporting multiphase heterojunction electrocatalyst includes a conductive substrate and CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction nanosheets, and the CoMoS 3.13 / FeS 2 / Co 3 S 4 heterojunction nanosheets are composed of CoMoS 3.13 , FeS 2 , and Co 3 S 4 in three components.

2. The catalyst according to claim 1, characterized in that, The CoMoS 3.13 / FeS 2 / Co 3 S 4 The heterojunction nanosheets are staggeredly grown on the conductive substrate and in the staggered growth process, the CoMoS 3.13 / FeS 2 / Co 3 S 4 A pore structure is formed between the heterojunction nanosheets.

3. The catalyst according to claim 1 or 2, characterized in that, The CoMoS 3.13 / FeS 2 / Co 3 S 4 The size of the heterojunction nanosheets is 500 - 700 nm.

4. The catalyst according to claim 1 or 2, characterized in that, the conductive substrate includes a carbon support or nickel foam; Preferably, the carbon support includes carbon paper or carbon cloth.

5. A method for preparing the three-dimensional self-supporting multiphase heterojunction electrocatalyst according to any one of claims 1-4, characterized in that, the preparation method includes: Step (1): Dissolve a molybdenum source, an iron source and a precipitant in deionized water to obtain solution A, dissolve a cobalt source and a morphology regulator in deionized water to obtain solution B, mix solution A, solution B and an acid-treated conductive substrate, and then carry out a hydrothermal reaction. After the hydrothermal reaction is completed, an FeCoMo precursor supported on the conductive substrate is obtained; Step (2): Dissolve a sulfur source in deionized water to obtain solution C, mix solution C and the FeCoMo precursor supported on the conductive substrate, and then carry out a sulfidation reaction. After the sulfidation reaction is completed, the three-dimensional self-supporting multiphase heterojunction electrocatalyst is obtained.

6. The preparation method according to claim 5, characterized in that, In solution A, the molar ratio of the molybdenum source, the iron source and the precipitant is 1:1:3 - 1:1.2:4, and in solution B, the molar ratio of the cobalt source and the morphology regulator is 1:1 - 3:

1.

7. The preparation method according to claim 5 or 6, characterized in that, the molybdenum source includes ammonium molybdate tetrahydrate and / or sodium molybdate, the iron source includes ferrous sulfate heptahydrate and / or ferric nitrate nonahydrate, and the cobalt source includes cobalt nitrate hexahydrate and / or cobalt sulfate.

8. The preparation method according to claim 5, characterized in that, In step (1), under stirring conditions, pour solution B into solution A and continue stirring to obtain a mixed solution, and then mix the mixed solution with the acid-treated conductive substrate.

9. The preparation method according to claim 5 or 8, characterized in that, The acid treatment of the conductive substrate includes: first immerse the conductive substrate in a concentrated nitric acid solution and then carry out ultrasonic treatment, then wash it with water until the pH value is 6.5 - 7, clean it with ethanol, and finally carry out a drying treatment.

10. The preparation method according to claim 5 or 6, characterized in that, the temperature of the hydrothermal reaction is 130 - 150 °C and the time is 5 - 7 h.

11. The preparation method according to claim 5, characterized in that, the molar ratio of the molybdenum source, the iron source, the cobalt source and the sulfur source is 1:1:1:1.2 - 1:1.2:2.3:2; Preferably, based on the total volume of deionized water contained in solution C, the concentration of the sulfur source is 0.04 - 0.06 mol / L.

12. The preparation method according to claim 5 or 11, characterized in that, the sulfur source includes one or a combination of several of thioacetamide, L-cysteine, thiourea and sodium sulfide.

13. The preparation method according to claim 5 or 11, characterized in that, the temperature of the sulfidation reaction is 150 - 170 °C and the time is 3 - 5 h.

14. The preparation method according to claim 5 or 6, characterized in that step (1) further includes ultrasonic washing and drying of the hydrothermal reaction product, and step (2) further includes ultrasonic washing and drying of the sulfidation reaction product; wherein, the ultrasonic washing is sequentially performed in deionized water and ethanol.

15. Application of the three-dimensional self-supporting multiphase heterojunction electrocatalyst according to any one of claims 1-4 in catalytic electrolytic water for hydrogen production.

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