Nickel sulfide-based heterostructure catalyst as well as preparation method and application thereof

Abstract

The invention discloses a nickel sulfide-based heterostructure catalyst and a preparation method and application thereof, the nickel sulfide-based heterostructure catalyst comprises foamed nickel and a Ni (OH) 2 / NiSx heterostructure loaded on the surface of the foamed nickel in a nanosheet array mode, the surface of Ni (OH) 2 is coated with NiSx in the Ni (OH) 2 / NiSx heterostructure, and NiSx represents a mixture of NiS and NiS2. A HERSOR dual-electrode system is constructed through a nickel sulfide-based heterostructure catalyst, the high theoretical potential of an anode oxygen evolution reaction is overcome, the current density of 100 mA / cm < 2 > can be driven by only needing 0.843 V battery voltage, and the energy-saving efficiency reaches 59.7%. The composite material can be stably output under complex components of seawater, has good adaptability to a seawater environment, and has tolerance.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a nickel sulfide-based heterogeneous structure catalyst and a preparation method and application thereof. Background Art

[0002] With global climate change and the continued intensification of fossil fuel consumption, the development of clean, sustainable energy has become a top priority. Hydrogen (H2) is considered an ideal energy carrier due to its high energy density and zero carbon emissions. Electrocatalytic water splitting technology can convert renewable energy (such as wind and solar energy) into hydrogen energy and is an important way to achieve green hydrogen production. However, traditional water electrolysis technology is heavily dependent on freshwater resources, which only accounts for 3.5% of the world's water reserves, making it difficult to meet the needs of large-scale industrialization.

[0003] In contrast, seawater reserves account for 96.5% of global water resources, but its electrolysis hydrogen production faces two core challenges:

[0004] 1) High overpotential problem of anodic oxygen evolution reaction (OER): OER involves a four-electron transfer process (4OH - →O2+2H2O+4e - ), the theoretical potential is 1.23 V (vs. RHE), but in actual application, a voltage far exceeding the theoretical value (>1.5 V) must be applied to achieve industrial-grade current density (>500 mA cm -2 ). High overpotential leads to a sharp increase in energy consumption, which seriously restricts the efficiency and economy of electrolysis.

[0005] 2) Competition with the Chlorine Evolution Reaction (ClOR) and Corrosive Byproducts: Seawater is rich in Cl- ions. When the anode potential exceeds 0.48 V (vs. RHE), Cl- competes with OH- for oxidation, generating corrosive substances such as Cl2 and ClO-. This leads to dissolution of the electrode material, shortening its lifespan and reducing hydrogen purity. Although alkaline conditions can inhibit ClOR, this requires a compromise in current density, making it difficult to meet practical requirements.

[0006] To reduce energy consumption, existing technologies have proposed replacing OER with low-potential oxidation reactions, such as hydrazine oxidation (HzOR), urea oxidation (UOR), and sulfide oxidation (SOR). Among them, SOR has attracted much attention due to its low theoretical potential (-0.48V vs. RHE) and the recyclability of the byproduct sulfur. However, existing catalysts have the following limitations: 1) Over-reliance on precious metals. Although catalysts such as Pt / C and RuO2 have excellent activity, they are expensive and resource-scarce, making them difficult to apply on a large scale; 2) Single-functionality limitation. Transition metal-based catalysts (such as Pt, Ni sulfide, and Co sulfide) are mostly optimized for a single reaction (HER or SOR) and lack bifunctional synergistic catalytic ability; 3) Insufficient stability. S8 generated during sulfur oxidation easily covers the active sites, leading to catalyst deactivation and substandard long-term stability. In addition, existing research has mostly focused on freshwater systems, and there is insufficient research on tolerance to the complex components of seawater and adaptability to actual working conditions. Therefore, developing a low-cost, highly active, and corrosion-resistant bifunctional catalyst to achieve efficient coupling of seawater electrolysis for hydrogen production and sulfur resource recovery is the key to breaking through the current technical bottleneck. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a nickel sulfide-based heterogeneous structure catalyst.

[0008] Another object of the present invention is to provide a method for preparing a nickel sulfide-based heterogeneous structure catalyst.

[0009] Another object of the present invention is to provide a HER||SOR dual-electrode system.

[0010] Another object of the present invention is to provide an application of a nickel sulfide-based heterogeneous structure catalyst for electrocatalysis in seawater.

[0011] The purpose of the present invention is achieved through the following technical solutions.

[0012] A nickel sulfide-based heterogeneous structure catalyst, comprising: nickel foam and Ni(OH)2 / NiS nanosheet arrays supported on the surface of the nickel foam. x Heterostructure, Ni(OH)2 / NiS x NiS in heterostructure x Coated on the surface of Ni(OH)2, NiS x Indicates a mixture of NiS and NiS2.

[0013] A method for preparing a nickel sulfide-based heterogeneous structure catalyst comprises the following steps:

[0014] Step 1: uniformly mix a nickel source, urea, ammonium fluoride and a solvent to obtain a homogeneous solution, immerse the nickel foam as a substrate in the homogeneous solution, and perform a hydrothermal reaction at 100-260° C. for 0.5-30 hours in a closed environment (the vapor pressure of the solvent provides the required pressure for the hydrothermal reaction), cool to room temperature, filter, wash, and dry to obtain a precursor, wherein the ratio of nickel, urea and ammonium fluoride in the nickel source is (1-10): (1-10): (1-10) in terms of molar mass;

[0015] In the step 1, the ratio of nickel, urea and ammonium fluoride in the nickel source is preferably (1-6): (3-7): (2-6), more preferably (1-3): (4-6): (3-5), calculated by amount.

[0016] In step 1, the nickel source is one of nickel nitrate hexahydrate, nickel acetate tetrahydrate, nickel sulfate and nickel chloride; and the solvent is a mixture of one or more of water and ethanol.

[0017] In the step 1, the nickel source, urea, ammonium fluoride and solvent are uniformly mixed by ultrasound for 1 to 120 minutes.

[0018] In the step 1, the nickel foam is ultrasonically cleaned in acetone, hydrochloric acid, water and anhydrous ethanol in sequence for 15 to 60 minutes before being immersed in the homogeneous solution, and then dried in an oven at 40 to 100° C. for 6 to 24 hours.

[0019] In the step 1, the ratio of the amount of nickel in the nickel source to the volume of the solvent is 1:(10-50), the unit of the amount of nickel is mmol, and the unit of the volume is mL.

[0020] In the step 1, the washing operation includes: washing with anhydrous ethanol and water alternately in sequence.

[0021] In step 1, the drying temperature is 20 to 100° C., and the drying time is 0.5 to 24 hours.

[0022] Step 2: Under an inert gas atmosphere, vapor-phase chemically deposit sulfur element on the precursor, cool it to room temperature, and obtain a nickel sulfide-based heterostructure catalyst, wherein the ratio of the mass fraction of the precursor to the amount of sulfur element is (1-200): (1-100), the unit of the mass fraction is g, and the unit of the amount of substance is mmol.

[0023] In the step 2, the vapor phase chemical deposition is achieved through a sulfur source.

[0024] In step 2, the time of vapor phase chemical deposition is 0.5 to 12 hours, preferably 1 to 3 hours.

[0025] In step 2, during the vapor phase chemical deposition, the temperature of the precursor is 250-450°C, preferably 300-400°C, and the temperature of the sulfur source is 200-400°C.

[0026] In step 2, an inert gas is continuously introduced at a gas flow rate of 10 to 100 mL / min to form an inert gas atmosphere.

[0027] In step 2, during the vapor phase chemical deposition, the precursor is placed downstream of the gas flow formed by the inert gas atmosphere, and the sulfur source is placed upstream of the gas flow formed by the inert gas atmosphere.

[0028] In step 2, the sulfur source is sulfur powder, sodium sulfide or thiourea, and the sulfur powder includes sublimated sulfur.

[0029] In step 2, the inert gas is argon or nitrogen.

[0030] In step 2, the ratio of the mass fraction of the precursor to the amount of sulfur is preferably (1-50):(1-10), more preferably (15-30):(1-2), the unit of the mass fraction is g, and the unit of the amount of sulfur is mmol.

[0031] A HER||SOR dual-electrode system comprises: a cathode, an anode, an electrolyte, and a diaphragm, wherein both the cathode and the anode are the above-mentioned nickel sulfide-based heterostructure catalyst; the diaphragm is arranged in a reaction chamber to separate the reaction chamber into a cathode chamber and an anode chamber; the anode is placed in the anode chamber, and the cathode is placed in the cathode chamber; the anode chamber is used for a sulfur ion oxidation reaction, and the cathode chamber is used for a hydrogen evolution reaction.

[0032] Application of the above nickel sulfide-based heterostructure catalyst in electrocatalysis in seawater.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention constructs a HER||SOR dual-electrode system by using a nickel sulfide-based heterostructure catalyst to overcome the high theoretical potential of the anodic oxygen evolution reaction (1.23 V vs. RHE). The HER||SOR dual-electrode system only requires a battery voltage of 0.843 V to drive 100 mA / cm 2 The current density is 1.250V lower than that of the traditional HER||OER system, and the energy saving efficiency reaches 59.7%.

[0035] (2) The nickel sulfide-based heterostructure catalyst of the present invention has the dual functions of sulfur ion oxidation and hydrogen evolution reaction. Its hydrogen evolution performance is similar to that of commercial Pt / C and is more stable. Its sulfur ion oxidation performance is significantly better than that of commercial RuO2. It has efficient proton adsorption and electron transfer capabilities. The nickel sulfide-based heterostructure catalyst also has excellent resistance to sulfur product passivation, so that the HER||SOR dual-electrode system constructed by the nickel sulfide-based heterostructure catalyst can stably output under the complex composition of seawater, and has good adaptability and tolerance in the seawater environment.

[0036] (3) The HER||SOR dual-electrode system of the present invention can recover high-purity sulfur products from sulfur-containing wastewater with a recovery rate exceeding 95%. It can be used in the production of lithium-sulfur batteries or chemical raw materials, achieving efficient treatment of sulfur pollution in industrial wastewater.

[0037] (4) The preparation method of the present invention is low-cost and has a simplified process. It uses non-precious metal nickel-based materials, avoids relying on expensive catalysts such as Pt and RuO2, and the preparation process only requires two steps: hydrothermal growth and sulfurization treatment, which is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the synthesis of nickel sulfide-based heterostructure catalysts;

[0039] Figure 2 The XRD pattern of the nickel sulfide-based heterostructure catalyst prepared in Example 2;

[0040] Figure 3 (a) High-resolution Ni 2p spectrum, (b) high-resolution O 1s spectrum, and (c) high-resolution S 2p spectrum of the nickel sulfide-based heterostructure catalyst prepared in Example 2;

[0041] Figure 4 This is a SEM image of the nickel sulfide-based heterostructure catalyst prepared in Example 2;

[0042] Figure 5 The hydrogen evolution reaction-polarization curves of the three-electrode system using the nickel sulfide-based heterostructure catalysts prepared in Examples 1 to 3 and the catalysts prepared in Comparative Examples 1 to 2 and Comparative Example 4;

[0043] Figure 6 is the Tafel slope of the hydrogen evolution reaction of the three-electrode system using the nickel sulfide-based heterostructure catalysts prepared in Examples 1 to 3 and the catalysts prepared in Comparative Examples 1 to 2 and Comparative Example 4;

[0044] Figure 7 The overpotentials of the hydrogen evolution reaction at different current densities in a three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Example 2 and the catalysts prepared in Comparative Examples 1-2 and Comparative Example 4;

[0045] Figure 8 This is a voltage test diagram of the hydrogen evolution reaction occurring in the three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Example 2;

[0046] Figure 9 The sulfide ion oxidation reaction-polarization curve of the three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Examples 1 to 3 and the catalyst prepared in Comparative Example 1 and Comparative Examples 3 to 4;

[0047] Figure 10 is the Tafel slope of the sulfide ion oxidation reaction of the three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Examples 1 to 3 and the catalyst prepared in Comparative Example 1 and Comparative Examples 3 to 4;

[0048] Figure 11 The overpotential of the sulfide ion oxidation reaction at different current densities in a three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Example 2 and the catalysts prepared in Comparative Example 1 and Comparative Examples 3-4;

[0049] Figure 12 This is a voltage test diagram of the sulfide ion oxidation reaction in the three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Example 2;

[0050] Figure 13 is the XRD pattern of elemental sulfur;

[0051] Figure 14 Schematic diagram of the HER||SOR two-electrode system;

[0052] Figure 15 Current-voltage curves of HER||SOR two-electrode system and HER||OER two-electrode system;

[0053] Figure 16 The Faradaic efficiency and hydrogen collection capacity of the HER||SOR two-electrode system;

[0054] Figure 17 This is the voltage test diagram of the HER||SOR two-electrode system. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0056] In the following examples, acetone and hydrochloric acid were purchased from Chengdu Clone Chemicals Co., Ltd.

[0057] Anhydrous ethanol was purchased from Chongqing Dandong Co., Ltd.;

[0058] Sublimed sulfur was purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.;

[0059] Nickel nitrate hexahydrate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0060] Urea was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0061] Hydrogen fluoride was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0062] In the following examples, seawater comes from the Yellow Sea in Rizhao City, Shandong Province, with a pH value of 8. The ions contained in the seawater and their concentrations are shown in Table 1.

[0063] Table 1

[0064] Ions in seawater <![CDATA[Cl - ]]> <![CDATA[K + ]]> <![CDATA[Na + ]]> <![CDATA[Ca 2+ ]]> <![CDATA[Br - ]]> <![CDATA[Mg 2+ ]]> concentration 19,800ppm 500ppm 11,000ppm 300ppm 50ppm 1500ppm

[0065] In the following embodiments, the instruments and models involved are as follows:

[0066] X-ray diffractometer (XRD), model: Bruker D8, Germany;

[0067] Scanning electron microscope (SEM), model: Quanta feg250;

[0068] Transmission electron microscope (TEM), model: Talos F200X;

[0069] Electrochemical workstation, model: Metrohm, Switzerland.

[0070] In the following examples, the three-electrode system includes: a working electrode, a reference electrode and a counter electrode. The electrolyte and its pH of the three-electrode system are specifically described in each example. The reference electrode is Hg / HgO; the counter electrode is graphite; and the working electrode is one of the nickel sulfide-based heterostructure catalysts prepared in Examples 1 to 6 and the catalysts prepared in Comparative Examples 1 to 4.

[0071] In the following examples, a sheet of nickel foam (1 cm × 2 cm, surface density 110 ppi, thickness 2.0 mm) was ultrasonically cleaned in acetone, hydrochloric acid, water, and anhydrous ethanol for 15 min in sequence before being placed in a homogenous solution, and then dried in an oven at 60°C for 12 h.

[0072] Examples 1 to 6

[0073] like Figure 1 As shown, a method for preparing a nickel sulfide-based heterogeneous structure catalyst comprises the following steps:

[0074] Step 1: The nickel source, urea (CO(NH2)2), ammonium fluoride (NH4F) and solvent (the solvent is deionized water) are mixed uniformly in a polytetrafluoroethylene-lined autoclave by ultrasound for 30 minutes to obtain a homogeneous solution, and the foamed nickel (area 1cm×2cm, surface density 110ppi, thickness 2.0mm) is placed (immersed) in 20mL of the above homogeneous solution, and the autoclave is sealed (the vapor pressure of the solvent provides the required pressure for the hydrothermal reaction). The hydrothermal reaction is carried out at 100°C for 12 hours, cooled to room temperature, filtered to obtain a precipitate, and the precipitate is alternately rinsed with anhydrous ethanol and water, and dried at 60°C for 12 hours to obtain a precursor, wherein, in terms of the amount of substance, the ratio of nickel, urea and ammonium fluoride in the nickel source is 1:5:4; the ratio of the amount of nickel in the nickel source to the volume of the solvent is 1:20, the unit of the amount of substance is mmol, and the unit of the volume is mL.

[0075] Step 2: Continuously introduce nitrogen gas at a gas flow rate of 20 mL / min into the dual-temperature zone tubular furnace to form an inert gas atmosphere. Under the inert gas atmosphere, place the precursor downstream of the gas flow formed by the inert gas atmosphere, and place the sulfur source (the sulfur source is sublimated sulfur) upstream of the gas flow formed by the inert gas atmosphere. Then, heat the precursor to T2°C at a heating rate of 5°C / min, and vapor-phase chemically deposit sulfur element on the T2°C precursor through a sulfur source at T1°C for 2 hours, and cool to room temperature to obtain a nickel sulfide-based heterostructure catalyst, wherein the ratio of the mass fraction of the precursor to the amount of sulfur in the sulfur source is 15:1, the unit of mass fraction is g, and the unit of amount of substance is mmol.

[0076] The numbers of the nickel source, T1, T2 and the sulfide nickel-based heterostructure catalyst prepared in Examples 1 to 6 are shown in Table 2.

[0077] Table 2

[0078] Example Nickel source <![CDATA[T1 (Unit: °C)]]> <![CDATA[T2 (Unit: °C)]]> serial number Example 1 Nickel nitrate hexahydrate 200℃ 250℃ <![CDATA[Ni(OH)2 / NiS x / NF-250]]> Example 2 Nickel nitrate hexahydrate 300℃ 350℃ <![CDATA[Ni(OH)2 / NiS x / NF-350]]> Example 3 Nickel nitrate hexahydrate 400℃ 450℃ <![CDATA[Ni(OH)2 / NiS x / NF-450]]> Example 4 Nickel acetate tetrahydrate 300℃ 350℃ <![CDATA[Ni(OH)2 / NiS x / NF-350-1]]> Example 5 Nickel sulfate 300℃ 350℃ <![CDATA[Ni(OH)2 / NiS x / NF-350-2]]> Example 6 Nickel chloride 300℃ 350℃ <![CDATA[Ni(OH)2 / NiS x / NF-350-3]]>

[0079] Comparative Example 1

[0080] A catalyst (number: Ni(OH)2 / NF) is the precursor in Example 2.

[0081] Comparative Example 2

[0082] A method for preparing a catalyst (code: Pt / C / NF) comprises the following steps: uniformly mixing 1.0 mg of an electrode material, 90 μL of a Nafion solution (the Nafion solution is purchased from Shanghai Hesen Electric Co., Ltd., and the Nafion content in the Nafion solution is 5 wt%), and 10 μL of ethanol by ultrasonication for 20 minutes to obtain a mixed solution; uniformly drop-coating the entire mixed solution on both sides of a nickel foam (manufacturer: Shanghai Hesen Electric Co., Ltd.) with a single-side area of 1 cm×3 cm; and drying the mixture at 110°C to obtain a catalyst (code: Pt / C / NF), wherein the electrode material is Pt / C purchased from Shanghai Hesen Electric Co., Ltd., and the platinum (Pt) content in the Pt / C is 20 wt%.

[0083] Comparative Example 3

[0084] A method for preparing a catalyst (number: RuO2 / NF) is basically the same as the method in Comparative Example 2, except that the electrode material is RuO2, which is purchased from Shanghai Aladdin.

[0085] Comparative Example 4

[0086] A method for preparing a catalyst (number: NF) is foamed nickel (manufacturer: Shanghai Hesen Electric Co., Ltd.).

[0087] Figure 2 The XRD pattern of the nickel sulfide-based heterostructure catalyst prepared in Example 2. Figure 2 It can be seen that the diffraction peaks at 44.5°, 51.9° and 76.4° correspond to nickel foam (NF), and two obvious diffraction peaks at 19.2° and 39.0° correspond to the (001) and (101) crystal planes in the Ni(OH)2 standard card (PDF#01-073-6992). In addition, the XRD spectrum also shows characteristic peaks corresponding to NiS (standard card: PDF#01-075-0613) and NiS2 (standard card: PDF#00-011-0099). This means that the Ni(OH)2 on the surface is sulfurized to NiS x (NiS x Represents a mixture of NiS and NiS2), while the internal Ni(OH)2 and NiS x A specific interface is formed between the two, forming Ni(OH)2 / NiS x Heterogeneous structure.

[0088] Further high-resolution analysis, such as Figure 3 As shown, Figure 3 (a) High-resolution Ni 2p spectrum, (b) high-resolution O1s spectrum, and (c) high-resolution S2p spectrum of the nickel sulfide-based heterostructure catalyst prepared in Example 2. Figure 3 From (a to c), we can see that the fitting peaks at 853.7eV and 871.0eV in the high-resolution Ni 2p spectrum are attributed to Ni 2+ The fitted peaks at 856.2 eV and 874.1 eV are attributed to Ni 3+ , and Ni appeared at 861.0eV and 878.6eV 3+ In the high-resolution O1s spectrum, the three fitting peaks at 531.1eV, 532.0eV and 532.8eV correspond to the Ni-O bond, Ni-OH bond and adsorbed water, respectively. In the high-resolution S2p spectrum, the fitting peaks at 162.0eV and 163.4eV are attributed to S 2- , the two fitted peaks at 162.9 eV and 164.1 eV correspond to S2 2- , indicating that Ni(OH)2 on the surface forms NiS and NiS2 during the sulfurization process, which is consistent with Figure 2 A broad SO bond peak was found at 169.2 eV, which is due to NiS x There is an obvious interfacial interaction between it and Ni(OH)2.

[0089] Figure 4 This is the SEM image of the nickel sulfide-based heterogeneous structure catalyst prepared in Example 2. Figure 4 It can be seen that there is a dense nanosheet array on the surface of the nickel sulfide-based heterostructure catalyst prepared in Example 2. In addition, there is a lattice spacing of 0.305 nm in the nickel sulfide-based heterostructure catalyst prepared in Example 2, which corresponds to the (100) crystal plane of NiS, and there are lattice spacings of 0.192 nm and 0.319 nm belonging to the (221) and (111) crystal planes of NiS2, respectively. This shows that the nanosheet array is Ni(OH)2 / NiS x Heterogeneous structure, its Ni(OH)2 / NiS x The heterostructure is loaded on nickel foam in the form of nanosheet arrays to form a three-dimensional porous structure. This unique structure enables the exposure of active sites and faster electron / proton transfer processes, promotes material transport, and improves electrolyte penetration efficiency, thereby optimizing the catalytic performance of nickel sulfide-based heterostructure catalysts.

[0090] Example 7

[0091] According to the literature (Min Gao, el. Interface engineering of the Ni(OH)2–Ni3N nanoarray heterostructure for the alkaline hydrogen evolution reaction. Journal of Materials Chemistry A. ssue 3, 2018.), it is known that the hydrogen evolution reaction (HER) occurs in the electrode voltage range of -0.7 to 0 V (versus. RHE). In addition, the working electrode containing Pt / C has excellent performance in HER and is one of the most commonly used commercial catalysts. Therefore, at an electrode voltage of -0.7 V to 0 V, a three-electrode system (the electrolyte is a mixture of KOH and seawater, and the concentration of KOH in the electrolyte is 1 M) using the nickel sulfide-based heterostructure catalysts prepared in Examples 1 to 3 and the catalysts prepared in Comparative Examples 1 to 2 and Comparative Example 4 as the "working electrode" is subjected to a linear sweep voltammetry (LSV) test to obtain a hydrogen evolution reaction-polarization curve (HER-LSV). The HER-LSV is as follows: Figure 5 As shown, when the current density reaches 100 mA cm -2 The overpotential (corresponding to Figure 5 -100mA cm on the vertical axis -2 The absolute value of the horizontal axis when ) is shown in Table 3. Figure 5 As shown in Table 3, the performance of the nickel sulfide-based heterogeneous structure catalysts prepared in Examples 1 to 3 is excellent, which is better than that of Comparative Example 1 and Comparative Example 4. The nickel sulfide-based heterogeneous structure catalyst prepared in Example 2 only needs 169 mV to reach 100 mA cm -2 , which is similar to commercial Pt / C (Comparative Example 2).

[0092] Table 3

[0093]

[0094]

[0095] The current obtained by the linear sweep voltammetry (LSV) is processed logarithmically to obtain the Tafel curve of electrocatalytic hydrogen evolution. The Tafel curve is as follows: Figure 6 As shown in Table 4, the Tafel slope is shown in Table 4. It can be seen from Table 4 that among Examples 1 to 3, the Tafel slope of the nickel sulfide-based heterogeneous structure catalyst prepared in Example 2 is the lowest, which is 151.2 mVdec. -1 , indicating that the kinetic performance of the nickel sulfide-based heterogeneous structure catalyst prepared in Example 2 is more favorable. The excellent HER activity of the nickel sulfide-based heterogeneous structure catalyst is due to the formation of Ni(OH)2 / NiS at an appropriate sulfurization temperature.x The heterogeneous structure contributes to the enhancement of surface chemical adsorption performance and catalytic kinetics, and also helps the ordered nanosheet arrays promote the diffusion of electrolyte and the release of H2 bubbles.

[0096] Table 4

[0097] Examples / Comparative Examples <![CDATA[Tafel slope (unit: mVdec -1 )]]> Example 1 <![CDATA[190.0mVdec -1 ]]> Example 2 <![CDATA[151.2mVdec -1 ]]> Example 3 <![CDATA[171.5mVdec -1 ]]> Comparative Example 1 <![CDATA[157.1mVdec -1 ]]> Comparative Example 2 <![CDATA[95.6mVdec -1 ]]> Comparative Example 4 <![CDATA[220.0mVdec -1 ]]>

[0098] Example 8

[0099] At an electrode voltage of -0.7 V to 0 V, a three-electrode system (the electrolyte is the same as that used in Example 7) using the nickel sulfide-based heterostructure catalyst prepared in Example 2 and the catalysts prepared in Comparative Examples 1 to 2 and Comparative Example 4 as the "working electrode" was tested using a linear sweep voltammetry (LSV) test. When the current density reached 50 mA cm -2 、100mAcm -2 and 300mAcm -2 The overpotential when Figure 7 As shown by Figure 7 It can be seen that the overpotentials of the three-electrode system of nickel sulfide-based heterogeneous structure catalyst prepared in Example 2 at different current densities are comparable to those of commercial Pt / C. -2 When the sulfide nickel-based heterostructure catalyst prepared in Example 2 is higher than the commercial Pt / C.

[0100] Example 9

[0101] Stability is an important indicator of working electrode performance. The three-electrode system with the nickel sulfide-based heterostructure catalyst prepared in Example 2 as the "working electrode" was tested at 100 mA cm -2 After running for 30 hours at the current density, the voltage test diagram of the hydrogen evolution reaction was obtained, as shown in FIG. Figure 8 As shown by Figure 8 It can be seen that after 30 hours of testing, the electrode voltage of the three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Example 2 decreased by about 6 mV. According to the literature (Lihan Zhang, el. Potential-Cycling Synthesis of Single Platinum Atoms for Efficient Hydrogen Evolution in Neutral Media. Angew Chem Int Ed, Volume 56, Issue: 44, Pages: 13694-13698.), at 100 mA cm -2After running for 24 hours at the same current density, the electrode voltage of the three-electrode system containing Pt / C decreased by about 250 mV. Therefore, the nickel sulfide-based heterostructure catalyst prepared in Example 2 of the present invention has better stability.

[0102] Example 10

[0103] According to the literature (Junyang Ding,el.Coupling Nitrate-to-Ammonia Conversion andSulfion Oxidation Reaction Over Hierarchical Porous Spinel MFe2O4(M-Ni,Co,Fe,Mn) in Wastewater.Small.Volume 21,Issue 19.May 12,2025) It can be seen that sulfide ion oxidation (SOR) occurs in the electrode voltage range of 0V~0.6V (versus.RHE). Therefore, at an electrode voltage of 0V~0.6V, a three-electrode system (the electrolyte is a mixture of KOH, Na2S and seawater, wherein the concentration of KOH in the electrolyte is 1M and the concentration of Na2S is 1M) using the nickel sulfide-based heterostructure catalysts prepared in Examples 1 to 3 and the catalysts prepared in Comparative Examples 1 to 4 as the "working electrode" was subjected to a linear sweep voltammetry (LSV) test. During the test, the three-electrode system containing Pt / C / NF showed obvious passivation phenomenon. The surface of the working electrode (Comparative Example 2) changed significantly after electrolysis, and a passivation layer was formed, making it difficult to obtain a sulfide ion oxidation reaction-polarization curve.

[0104] The sulfide ion oxidation reaction-polarization curves (SOR-LSV) of the nickel sulfide-based heterostructure catalysts prepared in Examples 1 to 3 and the catalysts prepared in Comparative Example 1 and Comparative Examples 3 to 4 are as follows: Figure 9 As shown, when the current density reaches 100 mA cm -2 The overpotential (corresponding to Figure 9 100mA cm on the vertical axis -2 The horizontal axis is shown in Table 5. Figure 9 As shown in Table 5, the nickel sulfide-based heterogeneous structure catalysts prepared in Examples 1 to 3 are superior to those in Comparative Examples 1 and 3 to 4. Among them, the nickel sulfide-based heterogeneous structure catalyst prepared in Example 2 provides the best SOR performance, requiring only 244 mV to reach 100 mVcm -2 , and its overpotential is much lower than that of commercial RuO2.

[0105] Table 5

[0106] Examples / Comparative Examples <![CDATA[100mAcm -2 Overpotential at time (unit: mV)]]> Example 1 362mV Example 2 244mV Example 3 240mV Comparative Example 1 519mV Comparative Example 3 436mV Comparative Example 4 527mV

[0107] The current obtained by the above linear sweep voltammetry (LSV) is logarithmically processed to obtain the Tafel curve of the electrocatalytic sulfur ion oxidation reaction. The Tafel curve is as follows: Figure 10 As shown in Table 5, the Tafel slope is shown in Table 5. It can be seen from Table 5 that the Tafel slope of the nickel sulfide-based heterostructure catalyst prepared in Example 2 is the lowest, which is 163.8 mVdec -1 , indicating that the nickel sulfide-based heterostructure catalyst prepared in Example 2 has more favorable kinetics.

[0108] Table 5

[0109] Examples / Comparative Examples Tafel slope Example 1 <![CDATA[256.2mVdec -1 ]]> Example 2 <![CDATA[163.8mVdec -1 ]]> Example 3 <![CDATA[207.7mVdec -1 ]]> Comparative Example 1 <![CDATA[270.7mVdec -1 ]]> Comparative Example 3 <![CDATA[265.9mVdec -1 ]]> Comparative Example 4 <![CDATA[172.5mVdec -1 ]]>

[0110] Example 11

[0111] At an electrode voltage of 0V to 0.6V, a three-electrode system (the electrolyte was the same as that in Example 10) using the nickel sulfide-based heterostructure catalyst prepared in Example 2 and the catalysts prepared in Comparative Examples 1 to 2 and Comparative Example 4 as the "working electrode" was subjected to a linear sweep voltammetry (LSV) test. When the current density reached 50 mA cm -2 、100mAcm -2 and 300mAcm -2 The overpotential when Figure 11 As shown by Figure 11 It can be seen that the overpotential of the three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Example 2 is optimal when reaching different current densities.

[0112] Example 12

[0113] The nickel sulfide-based heterostructure catalyst prepared in Example 2 was used as the working electrode in a three-electrode system at 100 mA cm -2 The system was operated at the same current density for 48 hours. The electrolyte of the three-electrode system was the same as that in Example 10, and the electrolyte was replaced every 12 hours to obtain a sulfide ion oxidation voltage test graph, as shown in FIG. Figure 12 As shown by Figure 12 It can be seen that after 48 hours of testing, the electrode voltage of the three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Example 2 always remains stable, and the voltage fluctuation is less than 1%.

[0114] After 48 hours of testing, all the electrolyte was recovered and 1M sulfuric acid was added to adjust the pH to 1. The electrolyte was allowed to stand for 12 hours and the solid was collected by centrifugation to obtain a yellow powder. The XRD characterization confirmed that the solid was elemental sulfur (such as Figure 13 As shown), it is proved that at 100mAcm -2Under the operation of current density, the nickel sulfide-based heterogeneous structure catalyst promotes the oxidation of S2- in the electrolyte to generate intermediate sulfur species (such as polysulfides), and further converts the polysulfide into free sulfide ions (S8 2- ) by acidification (S8 2- +2H + →H2S↑+S8↓) is converted into insoluble elemental sulfur (S8). The calculated recovery rate of elemental sulfur is as high as over 95%, indicating that the three-electrode system with the nickel sulfide-based heterogeneous structure catalyst prepared in Example 2 as the working electrode has the economic feasibility of recovering high-value-added sulfur products from sulfur-containing wastewater. Its stability also shows that compared with the traditional SOR catalyst, the NiS in the nickel sulfide-based heterogeneous structure catalyst is x For S 2- The affinity of the electrolyte is stronger, which further promotes the adsorption of sulfide ions and effectively inhibits the deposition of S8 products on the surface to cause passivation.

[0115] Example 13

[0116] Referring to the electrolyte and electrode voltage of the linear sweep voltammetry test in Example 7 or Example 10, a linear sweep voltammetry (LSV) test was performed on a three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Examples 4 to 6 as the working electrode. Under the test conditions of Example 7, a hydrogen evolution reaction occurred and a hydrogen evolution reaction-polarization curve was obtained, and the current density reached 100 mA cm -2 The overpotential when is shown in Table 6; Under the test conditions of Example 10, the sulfide ion oxidation reaction occurs to obtain the sulfide ion oxidation reaction-polarization curve, and its current density reaches 100mAcm -2 The overpotentials at 100 nm are shown in Table 6.

[0117] Table 6

[0118] Example Overpotential of hydrogen evolution reaction Overpotential of Sulfide Oxidation Reaction Example 4 169mV 245mV Example 5 171mV 244mV Example 6 170mV 244mV

[0119] Example 14

[0120] During the research, the present invention found that the sulfide ion oxidation reaction-polarization curve of the three-electrode system using the nickel sulfide-based heterostructure catalyst prepared in Example 2 as the "working electrode" and the sulfide ion oxidation reaction-polarization curve measured in 1M NaOH aqueous solution as the electrolyte almost overlapped with the sulfide ion oxidation reaction-polarization curve measured in seawater as the electrolyte. Therefore, the overpotential (corresponding to a current density of 100 mA cm) obtained by the electrolyte test in Example 10 was -2The overpotentials reported in the literature can be compared with those reported in existing literature (electrolyte mixtures of NaOH / KOH, Na2S, and water). Compared with the existing literature reports (Comparative Examples 5-10), the nickel sulfide-based heterostructure catalyst of the present invention not only avoids the use of precious metals but also exhibits a lower overpotential. The working electrodes, overpotentials, and literature sources for the existing literature reports (Comparative Examples 5-10) are shown in Table 7.

[0121] Table 7

[0122]

[0123]

[0124] The references for Comparative Examples 5 to 10 are as follows:

[0125] [1]X.Hao,K.Jiang,G.Liu,S.Zhou,D.Wang,Y.Zhang,T.Zhang,Y.Liu and P.Gu,Amultifunctional MoS2 / Ni9S8 / NF catalyst for synchronous desulfurization and hydrogen evolution by a self-driven system.Journal of Materials Chemistry A,2024,12,23732-23742

[0126] [2] J.Huo, L.Jin, C.Chen, D.Chen, Z.Xu, CDWilfred, Q.Xu and J.Lu, Improving the Sulfurophobicity of the NiS-Doping CoS Electrocatalyst Boosts the Low-Energy-Consumption Sulfide Oxidation Reaction Process. ACS Applied Materials&Interfaces, 2023, 15, 43976-43984.

[0127] [3]X.Liu,W.Wang,L.Wan,Y.Hu,C.Xia,L.Cao and B.Partially Amorphous Ru-Doped CoSe Nanoparticles with Optimized Intermediates Adsorption for HighlyEfficient Sulfur Oxidation Reaction.Dong,Small,2024,20,2406012.

[0128] [4]X.Tang,Y.Zhang,F.Wu,B.Li,J.Wang,X.Li,R.Rao,J.Hu,D.Xiao and T.Gao,Mo-doped cobaltous sulfide nanosheet arrays as efficient catalysts for thesulfion oxidation reaction promoting hydrogen production with ultra-lowelectric energy consumption.Inorganic Chemistry Frontiers,2023,10,6728-6737.

[0129] [5]J.Huo,Q.Liu,X.Liu,X.Cheng,D.Chen,N.Li,K.Liao,Q.Xu and J.Lu,SulfurRecovery Assisted Electrochemical Water Splitting for H2 Production UsingCoMo-Based Nanorod Arrays Catalysts.ACS Materials Letters,2024,6,2633-2641.

[0130] [6] Z.Wang, G.Yang, P.Tian,

[0131] Example 15

[0132] like Figure 14 As shown, a HER||SOR dual-electrode system includes: a cathode, an anode, an electrolyte and a diaphragm, the diaphragm is installed in the reaction chamber, and is used to separate the reaction chamber into a cathode chamber and an anode chamber, the cathode and the anode are both nickel sulfide-based heterostructure catalysts prepared in Example 2, and the diaphragm is a proton exchange membrane (manufacturer: DuPont, USA); the anode is placed in the anode chamber, and the electrolyte used in the anode chamber is a mixture of KOH, Na2S and seawater, and the concentration of KOH in the electrolyte used in the anode chamber is 1M, and the concentration of Na2S in the electrolyte used in the anode chamber is 1M; the cathode is placed in the cathode chamber, and the electrolyte in the cathode chamber is a mixture of KOH and seawater, and the concentration of KOH in the electrolyte used in the cathode chamber is 1M.

[0133] A HER||OER two-electrode system. The HER||OER two-electrode system is basically the same as the HER||SOR two-electrode system. The only difference is that the electrolyte used in the anode cavity is a mixture of KOH and seawater, and the concentration of KOH in the electrolyte in the anode cavity is 1M.

[0134] At an electrode voltage of 0V to 2.5V, the HER||SOR dual-electrode system and the HER||OER dual-electrode system were tested for current-voltage, and the current-voltage curves were obtained, as shown in FIG. Figure 15 As shown by Figure 15 It can be seen that the HER||SOR dual-electrode system is significantly better than the HER||OER dual-electrode system (2.093V), and only a battery voltage of 0.843V is required to achieve 100mA cm -2 The current density is 59.7%, and the energy saving efficiency is 59.7%. During the electrolysis process, a large number of bubbles are rapidly generated on the surface of the nickel sulfide-based heterogeneous structure catalyst in the cathode cavity. They are confirmed to be hydrogen and no obvious chlorine is precipitated. The hydrogen produced is collected every 10 minutes by the drainage method, and the hydrogen production per 10 minutes is obtained. Figure 16 As shown by Figure 16It can be seen that the actual collection amount of hydrogen produced in the HER||SOR dual-electrode system is highly consistent with the theoretical output value (the theoretical output value is calculated according to the Taaffe slope formula in the literature Junyang Ding, el. Coupling Nitrate-to-Ammonia Conversion and Sulfion Oxidation Reaction Over Hierarchical Porous Spinel MFe2O4 (M-Ni, Co, Fe, Mn) in Wastewater. Small. Volume 21, Issue 19. May 12, 2025), and its Faraday efficiency is close to 100%.

[0135] Example 16

[0136] The HER||SOR two-electrode system was tested at 50 mA cm -2 The current density was set to run for 36 hours, and the corresponding electrolyte in the cathode cavity and the anode cavity was replaced every 12 hours to obtain the voltage test graph, as shown in FIG. Figure 17 As shown by Figure 17 It can be seen that after 36 hours of testing, the cell voltage of the HER||SOR dual-electrode system is stable. This shows that the HER||SOR dual-electrode system of the present invention has a dual-functional synergistic catalytic ability, and the S8 generated during the sulfur oxidation process will not cover the active sites, resulting in catalyst deactivation. - Mg 2+ ) in seawater, especially in an environment with high concentration of Cl-, it still maintains high stability without obvious chlorine precipitation, and has tolerance.

[0137] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A nickel sulfide-based heterogeneous structure catalyst, characterized in that: Nickel sulfide-based heterogeneous structure catalysts include nickel foam and Ni(OH)2 / NiS nanosheet arrays supported on the surface of nickel foam. x Heterostructure, Ni(OH)2 / NiS x NiS in heterostructure x Coated on the surface of Ni(OH)2, NiS x Indicates a mixture of NiS and NiS2.

2. A method for preparing a nickel sulfide-based heterogeneous structure catalyst, characterized in that: The following steps are involved: Step 1: uniformly mixing a nickel source, urea, ammonium fluoride and a solvent to obtain a homogeneous solution, immersing the nickel foam in the homogeneous solution, and performing a hydrothermal reaction at 100-260° C. in a closed environment for 0.5-30 hours, cooling to room temperature, filtering, washing and drying to obtain a precursor, wherein the ratio of nickel, urea and ammonium fluoride in the nickel source is (1-10): (1-10): (1-10) in terms of molar mass; Step 2: Under an inert gas atmosphere, vapor-phase chemically deposit sulfur element on the precursor, cool it to room temperature, and obtain a nickel sulfide-based heterostructure catalyst, wherein the ratio of the mass fraction of the precursor to the amount of sulfur element is (1-200): (1-100), the unit of the mass fraction is g, and the unit of the amount of substance is mmol.

3. The preparation method according to claim 2, characterized in that Calculated by amount, the ratio of nickel, urea and ammonium fluoride in the nickel source is preferably (1-6): (3-7): (2-6), more preferably (1-3): (4-6): (3-5).

4. The preparation method according to claim 2, characterized in that The nickel source is one of nickel nitrate hexahydrate, nickel acetate tetrahydrate, nickel sulfate and nickel chloride; and the solvent is a mixture of one or more of water and ethanol.

5. The preparation method according to claim 2, characterized in that The vapor phase chemical deposition is achieved by a sulfur source; The time for the vapor phase chemical deposition is 0.5 to 12 hours, preferably 1 to 3 hours.

6. The preparation method according to claim 2, characterized in that During vapor chemical deposition, the temperature of the precursor is 250-450°C, preferably 300-400°C, and the temperature of the sulfur source is 200-400°C.

7. The preparation method according to claim 5, characterized in that During vapor phase chemical deposition, the precursor is placed downstream of the gas flow formed by the inert gas atmosphere, and the sulfur source is placed upstream of the gas flow formed by the inert gas atmosphere.

8. The preparation method according to claim 2, characterized in that The ratio of the mass fraction of the precursor to the molar fraction of sulfur element is preferably (1-50):(1-10), more preferably (15-30):(1-2), the unit of the mass fraction is g, and the unit of the molar fraction is mmol.

9. A HER||SOR dual-electrode system comprising: A cathode, an anode, an electrolyte and a diaphragm, wherein the cathode and the anode are the nickel sulfide-based heterostructure catalyst according to claim 1; The diaphragm is arranged in the reaction chamber to separate the reaction chamber into a cathode chamber and an anode chamber; the anode is placed in the anode chamber, and the cathode is placed in the cathode chamber.

10. Use of the nickel sulfide-based heterostructure catalyst as claimed in claim 1 in electrocatalysis in seawater.

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