A kind of sulfur-doped keggin type molybdenum polyacid and nickel sulfide heterojunction composite catalyst and its preparation method and application

Abstract

The application provides a kind of sulfur-doped keggin type molybdenum polyacid and nickel sulfide heterojunction composite catalyst and its preparation method and application.The heterojunction composite catalyst is composed of keggin type molybdenum polyacid doped with sulfur and nickel sulfide;The heterostructure of the heterojunction composite catalyst is formed by MoS2 and NiS.The application uses keggin type molybdenum polyacid ([HPMo9O 34 ] 8‑ )As a polyoxometalate framework, modify the nickel source, and simultaneously sulfidize, realize the synthesis of sulfur-doped keggin type molybdenum polyacid and nickel sulfide heterojunction composite catalyst, the heterojunction composite catalyst has excellent electrocatalytic performance and excellent electrochemical stability, in oxygen evolution reaction, it shows lower overpotential, lower tafel slope and excellent long-term running stability, provides a practical strategy for developing high-performance, low-cost, corrosion-resistant OER materials.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst, its preparation method and application. Background Technology

[0002] Hydrogen production through water electrolysis refers to the process of producing hydrogen and oxygen by electrolyzing water under a certain applied voltage. This process emits no carbon dioxide (CO2), making it green and pollution-free, and is considered an effective way to produce, store, and use renewable energy in the future. Water electrolysis consists of two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. However, the reaction barrier for water electrolysis is relatively high, requiring a catalyst to reduce the overpotential during the reaction to improve the efficiency of hydrogen production.

[0003] Currently, traditional catalysts are mainly noble metal-based catalysts, such as platinum (Pt)-based catalysts, iridium oxide (IrO2), and ruthenium oxide (RuO2). Although noble metal-based catalysts can effectively improve the efficiency of hydrogen production by water electrolysis, their scarcity and high price seriously hinder their large-scale application.

[0004] Furthermore, with the increasing scarcity of freshwater resources, seawater (accounting for over 97% of global water reserves) has become an ideal raw material for hydrogen production through water electrolysis due to its abundant reserves. However, seawater has a complex composition, containing various anions and cations (such as Na+). + K + Ca 2+ Cl - SO4 2- (etc.), where Cl - The presence of [something] can severely corrode the catalyst, leading to a decrease in its electrochemical stability.

[0005] Therefore, developing non-precious metal-based catalysts with low cost and high electrochemical stability is an urgent problem to be solved. Summary of the Invention

[0006] This invention provides a heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide. This heterojunction composite catalyst exhibits excellent electrocatalytic performance and electrochemical stability. When applied to alkaline water electrolysis or seawater electrolysis for oxygen evolution reaction (OER), it demonstrates low overpotential, low Tafel slope, and excellent long-term operational stability. The raw materials for preparing this heterojunction composite catalyst are inexpensive and the preparation process is simple, providing a practical strategy for developing high-performance, low-cost, and corrosion-resistant OER materials.

[0007] This invention also provides a method for preparing the above-mentioned sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst. This method can prepare a heterojunction composite catalyst with excellent electrocatalytic performance and excellent electrochemical stability. When this heterojunction composite catalyst is applied to alkaline water electrolysis or seawater electrolysis for oxygen evolution, it exhibits low overpotential, low Tafel slope, and excellent long-term operational stability. This method is simple, easy to operate, and produces no waste, making it environmentally friendly and conducive to industrial production.

[0008] The present invention also provides an electrode comprising a metal substrate and the aforementioned sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst grown in situ on the surface of the metal substrate. In the oxygen evolution reaction, the electrode exhibits a lower overpotential, a lower Tafel slope, and excellent long-term operational stability.

[0009] This invention also provides an application of the electrode described above, using it in alkaline water electrolysis oxygen evolution reaction or seawater electrolysis oxygen evolution reaction. The inventors' research shows that an electrode made of a metal substrate and the aforementioned sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst grown in situ on the surface of the metal substrate exhibits low overpotential, low Tafel slope, and excellent long-term operational stability when used in oxygen evolution reactions in 1 M KOH solution or in simulated seawater (1.0 M KOH + 0.5 M KCl solution).

[0010] A first aspect of the present invention provides a heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide, wherein the heterojunction composite catalyst is composed of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide.

[0011] The heterostructure of the heterojunction composite catalyst is formed by MoS2 and NiS.

[0012] The heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide, as described above, has a heterostructure consisting of a (002) crystal plane of MoS2, a (101) crystal plane of NiS, and a (300) crystal plane of NiS.

[0013] The sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst described above has a morphology of a composite structure containing synaptic structures and nanosheet structures.

[0014] A second aspect of the present invention provides a method for preparing the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst, comprising the following steps:

[0015] A nickel source solution, thiourea, and keggin-type molybdenum polyacid were mixed to obtain a mixture solution;

[0016] The metal substrate is placed in the mixture solution for growth reaction, and after drying, a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst is obtained by in-situ growth on the surface of the metal substrate.

[0017] The preparation method of the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst as described above, wherein the growth reaction is carried out at a temperature of 180-230℃ for 20-30h.

[0018] The method for preparing the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst described above, wherein the keggin-type molybdenum polyacid anion has the chemical formula [HPMo9O] 34 ] 8- .

[0019] In the preparation method of the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst as described above, the mass ratio of nickel source, thiourea and keggin-type molybdenum polyacid in the nickel source solution is (10-15):(6-10):(8-12).

[0020] The preparation method of the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst as described above, wherein the mass concentration of the nickel source solution is 10-15 mg / mL, and the nickel source in the nickel source solution includes nickel nitrate hexahydrate;

[0021] And / or, the metal substrate includes either nickel-iron foam or nickel foam.

[0022] A third aspect of the present invention provides an electrode comprising a metal substrate and a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst grown in situ on the surface of the metal substrate.

[0023] The sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst is the above-mentioned sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst.

[0024] The metal substrate includes either nickel-iron foam or nickel foam.

[0025] The fourth aspect of the present invention provides an application of the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst or the electrode, wherein the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst or the electrode is used in alkaline water electrolysis oxygen evolution reaction or seawater electrolysis oxygen evolution reaction.

[0026] The solution of the present invention has at least the following effects:

[0027] The sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst provided by this invention utilizes keggin-type molybdenum polyacid ([HPMo9O)) 34 ] 8- As a polymetallic oxygen cluster framework, the nickel source (nickel nitrate hexahydrate in this embodiment) is modified and simultaneously sulfided (sulfur doping using thiourea in this embodiment) to achieve in-situ growth of a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst on the surface of a metal substrate. Firstly, the oxygen cluster framework of the keggin-type molybdenum polyacid provides an atomically dispersed template, anchoring single-atom nickel atoms within the framework, inhibiting aggregation during sulfidation, increasing active sites for water electrolysis, and facilitating the electrocatalytic process. Secondly, the heteroatoms such as Mo / P in the keggin-type molybdenum polyacid synergistically regulate the electronic structure, optimizing the d-band center of the sulfide, which helps lower the reaction energy barrier. Thirdly, sulfidation retains part of the oxygen cluster framework of the keggin-type molybdenum polyacid (the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst still retains part of the keggin-type molybdenum polyacid oxygen cluster framework), enhancing conductivity and improving electrocatalytic performance. Studies have shown that this sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst exhibits excellent electrocatalytic performance and electrochemical stability. In the oxygen evolution reaction (OER), it displays low overpotential, low Tafel slope, and excellent long-term operational stability. Furthermore, the preparation of this heterojunction composite catalyst utilizes inexpensive raw materials and a simple process, providing a practical strategy for developing high-performance, low-cost, and corrosion-resistant OER materials. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a scanning electron microscope image of S-PMo9-Ni2S NiFe NF in Example 1 of the present invention;

[0030] Figure 2 This is a scanning electron microscope (SEM) image of S-PMo9-Ni2S in Example 1 of the present invention, wherein... Figure 2 Image A is a scanning electron microscope image of S-PMo9-Ni2S at a scale of 50 μm. Figure 2Image B is a scanning electron microscope image of the synaptic structure in S-PMo9-Ni2S at the 10 μm scale. Figure 2 C is a scanning electron microscope image of the nanosheet structure in S-PMo9-Ni2S at the 500 nm scale;

[0031] Figure 3 This is an elemental mapping diagram of the synaptic structure in the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) of Example 1, wherein... Figure 3 'a' represents the mapping selection diagram for synaptic structures. Figure 3 b is the image of carbon (C) element. Figure 3 c represents the oxygen (O) element image. Figure 3 d represents the sulfur (S) elemental image. Figure 3 The image shows the element 'e', ​​which represents iron (Fe). Figure 3 f is the elemental image of nickel (Ni). Figure 3 The image for g is of molybdenum (Mo). Figure 3 h represents the phosphorus (P) element image;

[0032] Figure 4 This is an elemental mapping diagram of the nanosheet structure in the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) of Example 1, wherein... Figure 4 'a' represents the mapping selection diagram for the nanosheet structure. Figure 4 b is the image of oxygen (O). Figure 4 c represents the elemental graph of iron (Fe). Figure 4 d represents the elemental image of nickel (Ni). Figure 4 The image for element 'e' is of molybdenum (Mo). Figure 4 f is the image of phosphorus (P). Figure 4 The image of g represents carbon (C) element;

[0033] Figure 5 The XRD patterns of S-PMo9-Ni2S and S-PMo9-Ni2S NiFe NF in Example 1 of this invention are shown.

[0034] Figure 6 This is a transmission electron microscope (TEM) image of the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) in Example 1 of the present invention at a scale of 50 nm.

[0035] Figure 7 This is a transmission electron microscope (TEM) image of the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) in Example 1 of the present invention at a scale of 5 nm.

[0036] Figure 8 The keggin-type molybdenum polyacid (Na8(HPMo9O)) in Example 1 of this invention 34 Infrared spectra of the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S);

[0037] Figure 9 Linear sweep voltammetry (LSV) polarization curves of the working electrodes in Examples 1-2 and Comparative Examples 1-2 of this invention during the anodic oxygen evolution reaction (OER) test in 1 M KOH solution;

[0038] Figure 10 The Tafel slope curves of the working electrodes in Examples 1-2 and Comparative Examples 1-2 of this invention in 1 M KOH solution are shown.

[0039] Figure 11 The above are bar charts showing the overpotential of the working electrodes in 1 M KOH solution in Examples 1-2 and Comparative Examples 1-2 of this invention.

[0040] Figure 12 The working electrode in Example 1 of this invention is in 1 M KOH solution, 800 mA / cm 2 The following is a graph showing the stability test results over a long period of time.

[0041] Figure 13 Linear sweep voltammetry (LSV) polarization curves of the working electrodes in Example 1 and Comparative Examples 1-2 of this invention for anodic oxygen evolution reaction (OER) testing in 1.0 M KOH + 0.5 M KCl solution;

[0042] Figure 14 The Tafel slope curves of the working electrodes in Example 1 and Comparative Examples 1-2 of this invention in 1.0 M KOH + 0.5 M KCl solution are shown.

[0043] Figure 15 The above is a bar chart showing the overpotential of the working electrode in Example 1 and Comparative Examples 1-2 of this invention in a 1.0 M KOH + 0.5 M KCl solution;

[0044] Figure 16 The working electrodes in Example 1 and Comparative Example 3 of this invention were subjected to a 1.0 M KOH + 0.5 M KCl solution at 10000 mA cm⁻¹ -2 Long-term stability testing will be conducted. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this art or in accordance with the product instructions. Reagents or instruments used without specified manufacturers are all conventional products that can be obtained commercially.

[0046] In the following description, the term "and / or" is used to describe the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. A and B can be singular or plural.

[0047] In the following description, the terms "including," "containing," and "containing" are open-ended terms, meaning that they include but are not limited to.

[0048] Those skilled in the art should understand that, in the following description of the embodiments of the present invention, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0049] Those skilled in the art will understand that the numerical ranges in the embodiments of the present invention should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0050] Unless otherwise stated, the technical / scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention pertains. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0051] In a first aspect, the present invention provides a heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide (hereinafter referred to as heterojunction composite catalyst), wherein the heterojunction composite catalyst is composed of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide.

[0052] The heterostructure of the heterojunction composite catalyst is formed by MoS2 and NiS.

[0053] In this invention, the chemical formula of the heterojunction composite catalyst is S-PMo9-Ni2S, where S represents sulfur, P represents phosphorus, Mo represents molybdenum, and Ni represents nickel.

[0054] In this invention, the heterojunction composite catalyst exhibits excellent electrocatalytic performance and excellent electrochemical stability. In the oxygen evolution reaction (OER), it demonstrates low overpotential, low Tafel slope, and excellent long-term operational stability. The raw materials for the preparation of this heterojunction composite catalyst are inexpensive and the preparation process is simple, providing a practical strategy for developing high-performance, low-cost, and corrosion-resistant OER materials.

[0055] The principle of preparing the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst of the present invention is explained as follows: The sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst provided by the present invention utilizes keggin-type molybdenum polyacid ([HPMo9O)) 34 ] 8- As a polymetallic oxygen cluster framework, the nickel source (nickel nitrate hexahydrate in this embodiment of the invention) is modified and sulfided simultaneously (sulfur doping is performed using thiourea in this embodiment of the invention) to achieve in-situ growth of a heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide on the surface of a metal substrate. First, the oxygen cluster framework of keggin-type molybdenum polyacid provides an atomically dispersed template, anchoring single-atom nickel atoms within it. This inhibits aggregation during sulfidation, increases active sites for water electrolysis, and facilitates the electrocatalytic process. Second, the synergistic regulation of the electronic structure by heteroatoms such as Mo / P in keggin-type molybdenum polyacid optimizes the d-band centers of the sulfides (sulfur-doped keggin-type molybdenum polyacid and nickel sulfide), which helps lower the reaction energy barrier. Finally, sulfidation retains some of the oxygen cluster framework of keggin-type molybdenum polyacid (the heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide still retains some of the oxygen cluster framework of keggin-type molybdenum polyacid), enhancing conductivity and improving electrocatalytic performance.

[0056] In one specific embodiment, the heterostructure of the above-mentioned heterojunction composite catalyst is composed of a (002) crystal plane of MoS2, a (101) crystal plane of NiS and a (300) crystal plane of NiS.

[0057] In one specific embodiment, the morphology of the above-mentioned sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst is a composite structure containing synaptic structures and nanosheet structures. This composite structure can be exposed to the maximum extent, allowing it to fully contact the electrolyte, increasing the contact area of ​​the reaction, which is beneficial to enhancing the reaction activity and improving the catalytic efficiency.

[0058] Secondly, the present invention provides a method for preparing the above-mentioned sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst, comprising the following steps:

[0059] A nickel source solution, thiourea, and keggin-type molybdenum polyacid were mixed to obtain a mixture solution;

[0060] The metal substrate is placed in the mixture solution for growth reaction, and after drying, a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst is obtained by in-situ growth on the surface of the metal substrate.

[0061] In this invention, the nickel source solution is prepared by dissolving a nickel source in an aqueous solution.

[0062] The present invention does not limit the shape, size, or thickness of the metal substrate; it can be selected according to actual needs.

[0063] This invention does not impose particular limitations on the specific reaction equipment used when placing the metal substrate in the mixture solution for the growth reaction; reaction equipment commonly used by those skilled in the art can be used. For example, a polytetrafluoroethylene high-pressure reactor can be used.

[0064] This invention utilizes a hydrothermal reaction to grow a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst in situ on the surface of a metal substrate, thereby increasing the interfacial bonding strength between the catalyst and the metal substrate. When the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst and the metal substrate are used as a whole, the problem of easy detachment of the catalyst under high current is prevented.

[0065] In one specific embodiment, the temperature for the growth reaction is 180-230°C and the time is 20-30 hours.

[0066] In one specific embodiment, the chemical formula of the above-mentioned keggin-type molybdenum polyacid anion is [HPMo9O]. 34 ] 8- .

[0067] This invention relates to the preparation of anions with the chemical formula [HPMo9O] 34 ]8- The specific preparation method of the keggin-type molybdenum polyacid is not particularly limited. Preferably, the present invention obtains it through a preparation method including the following process:

[0068] A molybdate solution is prepared by dissolving molybdate in water. Phosphoric acid and glacial acetic acid are added to the molybdate solution, and the mixture is stirred vigorously and then filtered to obtain the final product.

[0069] In one specific embodiment, the mass ratio of the nickel source, the thiourea and the keggin-type molybdenum polyacid in the nickel source solution is (10-15):(6-10):(8-12).

[0070] In one specific embodiment, the mass concentration of the nickel source solution is 10-15 mg / mL; the nickel source in the nickel source solution includes nickel nitrate hexahydrate.

[0071] In one specific embodiment, the metal substrate includes either foamed nickel-iron or foamed nickel, preferably foamed nickel-iron.

[0072] Thirdly, the present invention provides an electrode comprising a metal substrate and a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst grown in situ on the surface of the metal substrate; wherein the heterojunction composite catalyst is the aforementioned sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst; and the metal substrate comprises either nickel-iron foam or nickel foam.

[0073] Fourthly, this invention provides an application of the aforementioned sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst or electrode, which is used in alkaline water electrolysis oxygen evolution reaction or seawater electrolysis oxygen evolution reaction. The inventors' research shows that an electrode made from a metal substrate and the aforementioned sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst grown in situ on the surface of the metal substrate exhibits low overpotential, low Tafel slope, and excellent long-term operational stability when used in 1 mol / L KOH solution or in simulated seawater (a mixed solution of 1 mol / L KOH and 0.5 mol / L KCl).

[0074] The present invention will be further described below through specific embodiments.

[0075] In the following examples, nickel foam (NF) was purchased from Lizhiyuan Technology Co., Ltd., nickel-iron foam (NiFe NF) was purchased from Sigma-Aldrich, and the commercial Pt / C (20%) catalyst was purchased from Sigma-Aldrich.

[0076] Example 1 (metal substrate is foamed nickel iron)

[0077] This embodiment provides a method for preparing a heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide grown in situ on the surface of nickel-iron foam, including the following steps:

[0078] (1) Dissolve 12g of sodium molybdate (Na2MoO4) in 15mL of water to prepare a molybdate solution. Then add 0.3mL of phosphoric acid (H3PO4) and 2.2mL of glacial acetic acid to the molybdate solution, stir vigorously, and filter under vacuum to obtain a white crystalline precipitate, namely keggin-type molybdenum polyacid, with the chemical formula Na8(HPMo9O) 34 );

[0079] (2) Dissolve 1.30g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) in 100mL of deionized water to prepare a nickel source solution; then stir and mix the nickel source solution, 0.8g of thiourea and 1g of keggin-type molybdenum polyacid from step (1) until homogeneous to obtain a mixture solution;

[0080] (3) Foamed nickel-iron (with an area of ​​1×1cm) 2 After being sonicated in acetone for 10 min, it was then sonicated in ethanol for 10 min to obtain pretreated nickel-iron foam (NiFeNF).

[0081] The pretreated nickel-iron foam (NiFe NF) was placed in the mixture solution in step (2) and grown in a polytetrafluoroethylene high-pressure reactor at 210°C for 24 hours. After the polytetrafluoroethylene high-pressure reactor cooled naturally to room temperature, the reacted nickel-iron foam was taken out, rinsed with deionized water, and dried in a vacuum drying oven at 60°C to obtain a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (hereinafter referred to as heterojunction composite catalyst) grown in situ on the surface of nickel-iron foam. The sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst is designated as S-PMo9-Ni2S, and the nickel-iron foam and the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst grown in situ on the surface of the nickel-iron foam are collectively designated as S-PMo9-Ni2S NiFe NF.

[0082] Example 2 (metal substrate is nickel foam)

[0083] This embodiment provides a method for preparing a heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide grown in situ on the surface of nickel foam, including the following steps:

[0084] (1) Dissolve 12g of sodium molybdate (Na2MoO4) in 15mL of water to prepare a molybdate solution. Then add 0.3mL of phosphoric acid (H3PO4) and 2.2mL of glacial acetic acid to the molybdate solution, stir vigorously, and filter under vacuum to obtain a white crystalline precipitate, namely keggin-type molybdenum polyacid, with the chemical formula Na8(HPMo9O) 34 );

[0085] (2) Dissolve 1.30g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) in 100mL of deionized water to prepare a nickel source solution; then stir and mix the nickel source solution, 0.8g of thiourea and 1g of keggin-type molybdenum polyacid from step (1) until homogeneous to obtain a mixture solution;

[0086] (3) Place nickel foam (with an area of ​​1×1cm) 2 After being sonicated in acetone for 10 min, the pretreated nickel foam (NF) was then sonicated in ethanol for 10 min to obtain pretreated nickel foam.

[0087] The pretreated nickel foam (NF) was placed in the mixture solution in step (2) and grown in a polytetrafluoroethylene high-pressure reactor at 210°C for 24 hours. After the polytetrafluoroethylene high-pressure reactor cooled naturally to room temperature, the reacted nickel foam was taken out, rinsed with deionized water, and dried in a vacuum drying oven at 60°C to obtain a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (hereinafter referred to as heterojunction composite catalyst) grown in situ on the surface of nickel foam. The sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst is designated as S-PMo9-Ni2S, and the nickel foam and the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst grown in situ on the surface of the nickel foam are collectively designated as S-PMo9-Ni2S NF.

[0088] Comparative Example 1 (without keggin-type molybdenum polyacid)

[0089] This comparative example provides a method for preparing a nickel sulfide catalyst grown in situ on the surface of nickel-iron foam, comprising the following steps:

[0090] (2) Dissolve 1.30g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) in 100mL of deionized water to prepare a nickel source solution; then mix the nickel source solution with 0.8g of thiourea to obtain a mixture solution.

[0091] (3) Foamed nickel-iron (with an area of ​​1×1cm) 2 After being sonicated in acetone for 10 min, it was then sonicated in ethanol for 10 min to obtain pretreated nickel-iron foam (NiFeNF).

[0092] The pretreated nickel-iron foam (NiFe NF) was placed in the mixture solution in step (2) and grown in a polytetrafluoroethylene high-pressure reactor at 210°C for 24 hours. After the polytetrafluoroethylene high-pressure reactor cooled naturally to room temperature, the reacted nickel-iron foam was taken out, rinsed with deionized water, and dried in a vacuum drying oven at 60°C to obtain a nickel sulfide catalyst grown in situ on the surface of the nickel-iron foam. The nickel sulfide catalyst was denoted as Ni2S, and the nickel-iron foam and the nickel sulfide catalyst grown in situ on the surface of the nickel-iron foam were collectively denoted as Ni2S NiFe NF.

[0093] Comparative Example 2

[0094] This comparative example provides a foamed nickel-iron (NiFe NF) with an area of ​​1×1 cm² without any treatment. 2 ).

[0095] Comparative Example 3

[0096] This comparative example provides a method for preparing a molybdenum polyacid catalyst on a foamed nickel-iron surface, comprising the following steps:

[0097] (1) Dissolve 12g of sodium molybdate (Na2MoO4) in 15mL of water to prepare a molybdate solution. Then add 0.3mL of phosphoric acid (H3PO4) and 2.2mL of glacial acetic acid to the molybdate solution, stir vigorously, and filter under vacuum to obtain a white crystalline precipitate, namely keggin-type molybdenum polyacid, with the chemical formula Na8(HPMo9O) 34 );

[0098] (2) Dissolve 1g of keggin-type molybdenum polyacid from step (1) in 100mL of deionized water to prepare a polyacid solution;

[0099] (3) Foamed nickel-iron (with an area of ​​1×1cm) 2 After being sonicated in acetone for 10 min, it was then sonicated in ethanol for 10 min to obtain pretreated nickel-iron foam (NiFeNF).

[0100] The pretreated nickel-iron foam (NiFe NF) was placed in the polyacid solution in step (2) and reacted in a polytetrafluoroethylene high-pressure reactor at 210°C for 24 hours. After the polytetrafluoroethylene high-pressure reactor cooled naturally to room temperature, the reacted nickel-iron foam was taken out, rinsed with deionized water, and placed in a vacuum drying oven at 60°C for drying to obtain the keggin-type molybdenum polyacid catalyst prepared on the surface of the nickel-iron foam. The keggin-type molybdenum polyacid catalyst was denoted as POMs, and the nickel-iron foam and the keggin-type molybdenum polyacid catalyst prepared on the surface of the nickel-iron foam were collectively denoted as POMs NiFe NF.

[0101] Performance testing

[0102] 1. Scanning electron microscopy test

[0103] Scanning electron microscopy was performed on the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) in Example 1 of the present invention, as well as on the foamed nickel iron and the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst whole (S-PMo9-Ni2S NiFe NF) grown in situ on the surface of the foamed nickel iron. Figure 1 This is a scanning electron microscope image of S-PMo9-Ni2S NiFe NF in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of S-PMo9-Ni2S in Embodiment 1 of the present invention, wherein, Figure 2 Image A is a scanning electron microscope image of S-PMo9-Ni2S at a scale of 50 μm. Figure 2 Image B is a scanning electron microscope image of the synaptic structure in S-PMo9-Ni2S at the 10 μm scale. Figure 2 C is a scanning electron microscope image of the nanosheet structure in S-PMo9-Ni2S at the 500 nm scale.

[0104] Depend on Figure 1 It can be seen that S-PMo9-Ni2S is uniformly distributed on the surface of NiFe NF.

[0105] Depend on Figure 2 It can be seen that S-PMo9-Ni2S is a composite structure with synaptic structure and nanosheet structure.

[0106] 2. Element mapping analysis

[0107] Elemental mapping analysis was performed on the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) in Example 1. Figure 3 This is an elemental mapping diagram of the synaptic structure in the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) of Example 1, wherein... Figure 3 'a' represents the mapping selection diagram for synaptic structures. Figure 3 b is the image of carbon (C) element. Figure 3 c represents the oxygen (O) element image. Figure 3 d represents the sulfur (S) elemental image. Figure 3 The image shows the element 'e', ​​which represents iron (Fe). Figure 3 f is the elemental image of nickel (Ni). Figure 3 The image for g is of molybdenum (Mo). Figure 3 h represents the phosphorus (P) element image; Figure 4This is an elemental mapping diagram of the nanosheet structure in the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) of Example 1, wherein... Figure 4 'a' represents the mapping selection diagram for the nanosheet structure. Figure 4 b is the image of oxygen (O). Figure 4 c represents the elemental graph of iron (Fe). Figure 4 d represents the elemental image of nickel (Ni). Figure 4 The image for element 'e' is of molybdenum (Mo). Figure 4 f is the image of phosphorus (P). Figure 4 The image shows g as the carbon (C) element.

[0108] Depend on Figure 3 It can be seen that the synaptic structure of S-PMo9-Ni2S contains uniformly distributed elements such as S, Mo, Ni and C, indicating that S-PMo9-Ni2S is doped with S element.

[0109] Depend on Figure 4 It can be seen that the nanosheet structure of S-PMo9-Ni2S contains elements such as Mo, Ni and C evenly distributed.

[0110] 3. X-ray diffraction (XRD) test

[0111] X-ray diffraction (XRD) tests were performed on S-PMo9-Ni2S and S-PMo9-Ni2S NiFe NF in Example 1 of the present invention, respectively; Figure 5 The XRD patterns of S-PMo9-Ni2S and S-PMo9-Ni2S NiFe NF in Example 1 of this invention are shown.

[0112] Depend on Figure 5 It can be seen that in the XRD pattern, S-PMo9-Ni2S has a characteristic peak at 13.67° belonging to the (002) crystal plane of 2H type molybdenum disulfide (MoS2), a characteristic peak at 32.46° belonging to the (100) crystal plane of molybdenum disulfide, a characteristic peak at 18.60° belonging to the (110) crystal plane of β type nickel sulfide (NiS), a characteristic peak at 32.46° belonging to the (330) crystal plane of nickel sulfide, and a characteristic peak at 35.90° belonging to the (021) crystal plane of nickel sulfide.

[0113] 4. Transmission electron microscopy test

[0114] Transmission electron microscopy was performed on the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) in Example 1 of the present invention. Figure 6This is a transmission electron microscope (TEM) image of the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S) in Example 1 of the present invention at a scale of 50 nm. Figure 7 This is a transmission electron microscope (TEM) image at the 5 nm scale of the heterojunction composite catalyst (S-PMo9-Ni2S) of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide in Example 1 of the present invention.

[0115] Depend on Figure 6 It can be seen that the crystal lattice structure of S-PMo9-Ni2S is uniform.

[0116] Depend on Figure 7 It is known that S-PMo9-Ni2S has a heterostructure formed by MoS2 (molybdenum disulfide) and NiS (nickel sulfide); the heterostructure in S-PMo9-Ni2S is composed of the (002) crystal plane of MoS2, the (101) crystal plane of NiS and the (300) crystal plane of NiS.

[0117] 5. Infrared spectroscopy test

[0118] Regarding the keggin-type molybdenum polyacid (Na8(HPMo9O)) in Example 1 of this invention 34 Infrared spectroscopy was performed on the sulfur-doped keggin-type molybdenum polyacid and the heterojunction composite catalyst of nickel sulfide (S-PMo9-Ni2S). Figure 8 The keggin-type molybdenum polyacid (Na8(HPMo9O)) in Example 1 of this invention 34 Infrared spectra of the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst (S-PMo9-Ni2S).

[0119] Depend on Figure 8 It can be known that the chemical formula of keggin-type molybdenum polyacid is Na8(HPMo9O). 34 The heterojunction composite catalyst (S-PMo9-Ni2S) of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide still retains part of the oxygen cluster framework of keggin-type molybdenum polyacid.

[0120] 6. Alkaline water electrolysis and oxygen evolution reaction experiment

[0121] The S-PMo9-Ni2S NiFe NF from Example 1, the S-PMo9-Ni2S NF from Example 2, the Ni2S NiFe NF from Comparative Example 1, and the NiFe NF from Comparative Example 2 were used as working electrodes (with an area of ​​1×1 cm²). 2A platinum sheet was used as the counter electrode, and a mercury / mercury oxide electrode was used as the reference electrode. A 1 mol / L potassium hydroxide solution (1.0 M KOH solution) was used as the electrolyte. The oxygen evolution reaction (OER) was tested at room temperature (25℃) using a CS350M electrochemical workstation (Wuhan Koster Instrument Co., Ltd.) at a scan rate of 10 mV / s. Figure 9 Linear sweep voltammetry (LSV) polarization curves of the working electrodes in Examples 1-2 and Comparative Examples 1-2 of this invention during the anodic oxygen evolution reaction (OER) test in 1M KOH solution; Figure 10 The Tafel slope curves of the working electrodes in Examples 1-2 and Comparative Examples 1-2 of this invention in 1 M KOH solution are shown. Figure 11 The above are bar charts showing the overpotential of the working electrodes in 1 M KOH solution in Examples 1-2 and Comparative Examples 1-2 of this invention. Figure 12 The working electrode in Example 1 of this invention is in 1 M KOH solution, 800 mA / cm 2 The following is a graph showing the stability test results over a long period of time.

[0122] Depend on Figure 9 It can be seen that the S-PMo9-Ni2S NiFe NF in Example 1 has the best oxygen evolution performance.

[0123] Depend on Figure 10 It can be seen that the Tafel slope of S-PMo9-Ni2S NiFe NF in Example 1 is 70.51 mV / dec, the Tafel slope of S-PMo9-Ni2S NF in Example 2 is 138.77 mV / dec, the Tafel slope of Ni2S NiFe NF in Comparative Example 1 is 76.85 mV / dec, and the Tafel slope of NiFe NF in Comparative Example 2 is 151.78 mV / dec. These results indicate that the heterojunction composite catalyst provided in the embodiments of the present invention exhibits a low Tafel slope in the oxygen evolution reaction in 1 M KOH solution.

[0124] Depend on Figure 11 It can be seen that at 100mA·cm -2 At current densities, the overpotential of S-PMo9-Ni2S NiFe NF in Example 1 was 265 mV, the overpotential of S-PMo9-Ni2S NF in Example 2 was 296 mV, the overpotential of Ni2S NiFe NF in Comparative Example 1 was 325 mV, and the overpotential of NiFe NF in Comparative Example 2 was 326 mV; at 300 mA·cm -2At current densities, the overpotential of S-PMo9-Ni2S NiFe NF in Example 1 was 302 mV, the overpotential of S-PMo9-Ni2S NF in Example 2 was 338 mV, the overpotential of Ni2S NiFe NF in Comparative Example 1 was 414 mV, and the overpotential of NiFe NF in Comparative Example 2 was 503 mV; at 500 mA·cm -2 At the specified current densities, the overpotential of S-PMo9-Ni2S NiFe NF in Example 1 was 322 mV, the overpotential of S-PMo9-Ni2S NF in Example 2 was 366 mV, the overpotential of Ni2S NiFe NF in Comparative Example 1 was 462 mV, and the overpotential of NiFe NF in Comparative Example 2 was 530 mV. These results indicate that the heterojunction composite catalyst provided in these embodiments exhibits a low overpotential at high current densities during the oxygen evolution reaction in 1 M KOH solution.

[0125] Depend on Figure 12 It can be seen that the S-PMo9-Ni2S NiFe NF in Example 1 has a performance of 800 mA / cm². 2 The fact that it can maintain its high performance even during long-term operation indicates that the heterojunction composite catalyst provided in this embodiment of the invention has excellent long-term operational stability.

[0126] Figures 9-12 The results show that the heterojunction composite catalyst provided in the embodiments of the present invention has excellent water electrolysis catalytic performance.

[0127] 7. Experiment on the oxygen evolution reaction of alkaline seawater electrolysis

[0128] The S-PMo9-Ni2S NiFe NF from Example 1, the Ni2S NiFe NF from Comparative Example 1, the NiFe NF from Comparative Example 2, and the POMs NiFe NF from Comparative Example 3 were used as working electrodes (with an area of ​​1×1 cm²). 2 A platinum sheet was used as the counter electrode, and a mercury / mercury oxide electrode was used as the reference electrode. A mixed solution containing 1 mol / L potassium hydroxide and 0.5 mol / L potassium chloride (1.0 M KOH + 0.5 M KCl solution, simulating seawater) was used as the electrolyte. The anodic oxygen evolution reaction (OER) was tested at room temperature (25℃) using a CS350M electrochemical workstation (Wuhan Koster Instrument Co., Ltd.) at a scanning rate of 10 mV / s. Figure 13 Linear sweep voltammetry (LSV) polarization curves of the working electrodes in Example 1 and Comparative Examples 1-2 of this invention for anodic oxygen evolution reaction (OER) testing in 1.0 M KOH + 0.5 M KCl solution; Figure 14The Tafel slope curves of the working electrodes in Example 1 and Comparative Examples 1-2 of this invention in 1.0 M KOH + 0.5 M KCl solution are shown. Figure 15 The above is a bar chart showing the overpotential of the working electrode in Example 1 and Comparative Examples 1-2 of this invention in a 1.0 M KOH + 0.5 M KCl solution; Figure 16 The working electrodes in Example 1 and Comparative Example 3 of this invention were subjected to a 1.0 M KOH + 0.5 M KCl solution at 10000 mA cm⁻¹ -2 The following is a graph showing the stability test results over a long period of time.

[0129] Depend on Figure 13 It can be seen that the S-PMo9-Ni2S NiFe NF in Example 1 has the best oxygen evolution performance.

[0130] Depend on Figure 14 It can be seen that the Tafel slope of S-PMo9-Ni2S NiFe NF in Example 1 is 51.99 mV / dec, the Tafel slope of Ni2S NiFe NF in Comparative Example 1 is 57.41 mV / dec, and the Tafel slope of NiFe NF in Comparative Example 2 is 79.09 mV / dec. These results indicate that the heterojunction composite catalyst provided in the embodiments of the present invention exhibits a lower Tafel slope in the oxygen evolution reaction (OER) in simulated seawater (1.0 M KOH + 0.5 M KCl solution).

[0131] Depend on Figure 15 It can be seen that at 100mA·cm -2 At current densities, the overpotential of S-PMo9-Ni2S NiFe NF in Example 1 was 290 mV, the overpotential of Ni2S NiFe NF in Comparative Example 1 was 299 mV, and the overpotential of NiFe NF in Comparative Example 2 was 401 mV; at 300 mA·cm⁻¹ -2 At current densities, the overpotential of S-PMo9-Ni2S NiFe NF in Example 1 was 324 mV, the overpotential of Ni2S NiFe NF in Comparative Example 1 was 346 mV, and the overpotential of NiFe NF in Comparative Example 2 was 442 mV; at 500 mA·cm⁻¹ -2 At the specified current density, the overpotential of S-PMo9-Ni2S NiFe NF in Example 1 was 339 mV, the overpotential of Ni2S NiFe NF in Comparative Example 1 was 376 mV, and the overpotential of NiFe NF in Comparative Example 2 was 456 mV. These results indicate that the heterojunction composite catalyst provided in these embodiments exhibits a low overpotential at high current densities during the oxygen evolution reaction in simulated seawater (1.0 M KOH + 0.5 M KCl solution).

[0132] Depend on Figure 16 It can be seen that at 10000A m -2 At the current density, the voltage of the S-PMo9-Ni2S NiFe NF in Example 1 is only 2.57 V, and it operates stably for more than 1500 hours with a performance degradation of only 2.33%, indicating that the heterojunction composite catalyst provided in this embodiment of the invention has excellent long-term operating stability.

[0133] Figures 13-16 The results show that the heterojunction composite catalyst provided in the embodiments of the present invention has excellent catalytic performance for seawater electrolysis.

[0134] In summary, the heterojunction composite catalyst provided in this invention exhibits excellent electrocatalytic performance and excellent electrochemical stability. In the oxygen evolution reaction of water electrolysis or seawater electrolysis, it demonstrates low overpotential, low Tafel slope, and excellent long-term operational stability, providing a practical strategy for developing high-performance, low-cost, and corrosion-resistant OER materials.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst, characterized in that, Includes the following steps: A nickel source solution, thiourea, and keggin-type molybdenum polyacid were mixed to obtain a mixture solution; The metal substrate is placed in the mixture solution for growth reaction, and after drying, a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst grown in situ on the surface of the metal substrate is obtained; the growth reaction is carried out at a temperature of 180-230℃ for 20-30h. The chemical formula of the keggin-type molybdenum polyacid anion is [HPMo9O]. 34 ] 8- .

2. The method for preparing the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst according to claim 1, characterized in that, The mass ratio of the nickel source, the thiourea, and the keggin-type molybdenum polyacid in the nickel source solution is (10-15):(6-10):(8-12).

3. The method for preparing the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst according to claim 1, characterized in that, The nickel source solution has a mass concentration of 10-15 mg / mL, and the nickel source in the nickel source solution includes nickel nitrate hexahydrate. And / or, the metal substrate includes either nickel-iron foam or nickel foam.

4. The sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst prepared by the method according to any one of claims 1-3, characterized in that, The heterojunction composite catalyst is composed of a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide. The heterostructure of the heterojunction composite catalyst is formed by MoS2 and NiS.

5. The heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide according to claim 4, characterized in that, The heterostructure of the heterojunction composite catalyst is composed of a (002) crystal plane of MoS2, a (101) crystal plane of NiS and a (300) crystal plane of NiS.

6. The heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide according to claim 4, characterized in that, The sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst has a morphology that includes synaptic structures and nanosheet structures.

7. An electrode, characterized in that, The catalyst includes a metal substrate and a sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction grown in situ on the surface of the metal substrate. Wherein, the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst is the sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst according to any one of claims 4-6. The metal substrate includes either nickel-iron foam or nickel foam.

8. The application of a heterojunction composite catalyst of sulfur-doped keggin-type molybdenum polyacid and nickel sulfide as described in any one of claims 4-6, or the electrode as described in claim 7, characterized in that, The sulfur-doped keggin-type molybdenum polyacid and nickel sulfide heterojunction composite catalyst or the electrode is used for alkaline water electrolysis oxygen evolution reaction or seawater electrolysis oxygen evolution reaction.

Images