A high-entropy metal sulfide electrode material, its preparation method and application

Abstract

The present invention provides a preparation method of a high-entropy metal sulfide electrode material. A three-electrode system is constructed with a substrate material as the working electrode, a saturated calomel electrode as the reference electrode, and a Pt sheet as the counter electrode. A mixed solution of at least five metal nitrates containing different transition metal ions is used as the electrolyte, and electrodeposition is carried out under the three-electrode system to obtain a metal hydroxide electrode precursor. The electrode precursor is subjected to sulfidation treatment to obtain a high-entropy metal sulfide electrode material. The present invention also provides an electrolytic cell using the above high-entropy metal sulfide electrode material as the anode electrode, which can efficiently and with low energy consumption oxidize sulfide ions in sulfur-containing wastewater and then assist in hydrogen production by electrolyzing water. At the same time, the electrolytic cell uses a carbon-modified sodium ion exchange membrane, which can effectively avoid the shuttle of sulfide ions and improve the efficiency and purity of hydrogen production at the cathode. As a new solution combining environmental treatment and clean energy hydrogen production, the present invention has important significance and application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical fields of electrocatalytic material preparation, electrochemical treatment of sulfur-containing wastewater, and hydrogen evolution technology. It relates to a high-entropy metal sulfide electrode material and a preparation method thereof, and also relates to an electrolytic cell with the high-entropy metal sulfide electrode material as the anode electrode, and the application of the above electrolytic cell in sulfur ion oxidation-assisted electrolytic water hydrogen production. Background Art

[0002] Hydrogen is considered to be the ultimate energy substance in the future, with the advantages of cleanliness, high calorific value, and renewability. People's demand for hydrogen energy is increasing day by day, so hydrogen production technology is of great significance. Electrochemical water splitting for hydrogen production is considered to be one of the most promising technologies for producing clean hydrogen energy. This benefits from the fact that clean water can be used as a hydrogen source and can integrate new energy power technologies, which is a green zero-carbon emission technology means. However, the cost of electrolytic water hydrogen production is relatively high compared with that of fossil energy hydrogen production, and its competitiveness in the market is relatively low. More than about 50% of the cost comes from the consumption of electric energy. Therefore, reducing the electric energy consumption is one of the main directions to solve the problem of high cost of electrolytic water hydrogen production. The anodic reaction in electrolytic water is the oxygen evolution reaction (4OH - → 2H 2 O + O 2 + 4e - ), which has a relatively high redox potential (1.23 V), and its kinetic reaction is slow, resulting in a relatively high overpotential, making the electrolytic voltage of the two electrodes relatively high. This is one of the main reasons for the high electric energy consumption.

[0003] On the other hand, sulfur ion-containing waste liquid is obtained by adsorbing hydrogen sulfide waste gas in industry with an alkali solution. The discharge amount is large and the pollution is serious. Therefore, it is very important to remove sulfur ions and utilize them resourcefully. The oxidation potential of the sulfur ion oxidation reaction can be as low as 0.17 V. Replacing the oxygen evolution reaction with it and coupling it with the hydrogen evolution reaction to construct a sulfur ion oxidation-assisted electrolytic water hydrogen production system will greatly reduce the electrolytic voltage and hydrogen production cost, and at the same time can realize the oxidation treatment of sulfur-containing wastewater (wastewater after absorbing H 2 S with concentrated alkali solution in fields such as petrochemical industry) and reduce its chemical oxygen demand (COD).

[0004] Existing electrode materials for catalyzing the sulfur ion oxidation reaction are difficult to balance the stability and activity at a large current density. This is because sulfur ions have strong corrosiveness, and the oxidation products polysulfide / sulfur elemental have poor conductivity, which is easy to cover the active sites and block the reaction substrates. Therefore, it is of great significance to find a suitable electrode material to avoid sulfur ion corrosion and coverage by insulating oxidation products.

[0005] In some current research, one design concept for catalysts for the sulfur ion oxidation reaction is to coat the surface of metal nanocatalytic particles with a conductive carbon shell layer to prevent sulfur ions from directly contacting the metal and causing corrosion. Moreover, the carbon shell layer has good conductivity, which alleviates the decrease in activity caused by the coverage of insulating products. Another approach is to synthesize metal sulfide electrode materials and utilize their compatibility with the sulfur ion environment to obtain better catalytic stability. However, these catalytic electrode materials for the sulfur ion oxidation reaction usually have single components and active sites, making it difficult to simultaneously optimize the processes of sulfur ion adsorption and the desorption of polysulfides / sulfur monomers to promote both the stability and catalytic activity of the reaction. Therefore, they cannot meet the demand for continuous and stable electrolysis at industrial-level electrolysis current densities ( ~1 A cm -2 ).

[0006] In addition, in existing research, sulfur ion oxidation-assisted water electrolysis for hydrogen production systems are generally completed in traditional H-type electrolytic cells, where both the cathode and anode electrode solutions are strongly alkaline. Traditional alkaline electrolytic water cells often use porous Zirfon ion exchange membranes, which easily cause anions to shuttle between the cathode and anode, making it difficult to obtain high-purity hydrogen. There are also problems such as large mass transfer resistance and low current density.

[0007] Based on this, there is an urgent need for an inexpensive, highly efficient, and sulfur-resistant electrocatalytic material to solve problems such as sulfur ion corrosion, low electrochemical stability and activity, and to design a suitable supporting electrolytic cell and catalytic system to optimize the mass transfer process and reaction path, thereby realizing the construction of a large-scale electrochemical sulfur ion oxidation-assisted water electrolysis for hydrogen production system. Summary of the Invention

[0008] One objective of the present invention is to provide a preparation method for a high-entropy metal sulfide electrode material that is efficient, low-cost, and can stably electrolyze at a low overpotential under a high current density.

[0009] Another objective of the present invention is to provide an electrolytic cell for a sulfur ion oxidation-assisted water electrolysis for hydrogen production system that can effectively prevent anion shuttling.

[0010] A third objective of the present invention is to provide the application of an electrolytic cell containing a high-entropy metal sulfide electrode material in a sulfur ion oxidation-assisted water electrolysis for hydrogen production system.

[0011] The technical solution adopted by the present invention to achieve the first objective is as follows: providing a preparation method for a high-entropy metal sulfide electrode material, comprising the following steps:

[0012] S1. Mix at least five metal nitrate solutions containing different transition metal ions to obtain a mixed metal nitrate solution;

[0013] S2. Use the substrate material as the working electrode, the saturated calomel electrode as the reference electrode, and the Pt sheet as the counter electrode to construct a three-electrode system;

[0014] S3, using the metal nitrate mixed solution as the electrolyte of the three-electrode system, and performing electrodeposition in a constant potential mode at a deposition potential of -0.5 to -1.5 V to obtain a metal hydroxide electrode precursor;

[0015] S4, placing the metal hydroxide electrode precursor in a sulfur-containing solution for sulfurization treatment, and washing and drying to obtain a high entropy metal sulfide electrode material.

[0016] The overall idea and inventive principle of the present invention are as follows:

[0017] The present invention aims to solve the problem of poor activity and stability of catalytic materials for sulfur ion oxidation reactions, and synthesizes a catalytic electrode in which an amorphous high-entropy metal sulfide with a "soft-hard" acid site gradient is in-situ grown on the surface of a substrate. The amorphous high-entropy metal sulfide with a "soft-hard" acid site gradient has the characteristics of promoting rapid adsorption of reactant sulfur ions and rapid desorption of product polysulfide / sulfur element, and improves the reaction rate during the catalytic cycle, thereby enabling stable electrolysis at a relatively low overpotential under industrial-grade current density.

[0018] In the above preparation method, a three-electrode system is constructed with a substrate material as a working electrode, a saturated calomel electrode as a reference electrode, and a Pt sheet as a counter electrode, and a metal nitrate mixed solution is used as an electrolyte. In a constant potential mode, a specific deposition potential (-0.5 to -1.5 V) is used and the deposition time (10-2000s) is controlled. During the electrodeposition process, the nitrate is decomposed to a limited extent, the nitrate is reduced to an ammonium ion, and hydroxide is generated. The metal ions combine with the hydroxide to form a metal hydroxide electrode precursor. Further, the metal hydroxide electrode precursor is immersed in a sulfur-containing solution for sulfidation treatment. Due to the large solubility product difference between metal hydroxide and sulfide, the sulfur ions replace the hydroxide in the lattice, and finally sulfidation is performed to form metal sulfide. Compared with the hydrothermal reaction, this operation method is cheap, simple and easy to scale up. In addition, due to the lattice distortion of the mild sulfurization process, the formation of amorphous crystals is promoted, and the disadvantage of hydrothermal sulfurization that it is easy to form a crystalline phase and cause phase separation is avoided, ensuring that the metal cations are evenly dispersed at the atomic level, thereby promoting the precise control of the electronic state and chemical environment between metals.

[0019] Furthermore, in step S1, the transition metal ions in the metal nitrate mixed solution include Cu 2+ 、Ni 2+ 、Co 2+ , Fe 2+ , Mn 2+ , Fe 3+ Cr 3+At least five of them. Different transition metal ions have different soft-hardness, thus providing a "soft-hard" acid site gradient for the amorphous high-entropy metal sulfide.

[0020] Preferably, in the metal nitrate mixed solution, the transition metal ions include Cu 2+ , Ni 2+ , Co 2+ , Mn 2+ and Cr 3 + . Under the specific deposition conditions of the present invention, the nitrates are limitedly decomposed to generate OH - which precipitates with metal ions. Instead of growing a metal phase on the substrate surface, a metal hydroxide phase (CuCoNiMnCr(OH) x ) is formed. And the elemental valence states on the surface of the material obtained after sulfidation are not in the metal phase, but from Cu + at the soft acid site, Ni 2+ / Co 2+ at the intermediate acid site, to the positive valence states of Mn 2+ / Cr 3+ at the hard acid site. Thus, an amorphous high-entropy metal sulfide with a "soft-hard" acid site gradient is in-situ grown on the substrate surface as an electrode material.

[0021] Furthermore, in step S1, in the metal nitrate mixed solution, the total concentration of the transition metal ions is 0.01 - 0.1 mol L -1 .

[0022] Furthermore, in step S2, the substrate material includes one of nickel foam, carbon paper, carbon cloth, and conductive glass (indium tin oxide or fluorine-doped indium tin oxide).

[0023] Preferably, the substrate material is nickel foam, and it undergoes the following pretreatment operations: The nickel foam is successively immersed in hydrochloric acid solution, deionized water, and absolute ethanol and ultrasonically cleaned to remove impurities, and then dried for standby. More preferably, the thickness of the nickel foam is 0.05 - 1 cm, and it is cut into flakes with a size of 2 × 2 cm 2 . The concentration of the hydrochloric acid solution is 0.1 - 6.0 mol L -1 , and the ultrasonic cleaning time is 10 min - 1 h. Compared with other substrate materials, nickel foam has a highly conductive skeleton structure and a higher specific surface area. The active substance is in-situ grown on the surface of the nickel foam substrate material, without the need for additional electrode material coating and the use of a binder. The preparation process is simple and controllable, and the catalyst structure grown on the substrate surface is stable.

[0024] Furthermore, in step S4, the sulfur-containing solution is an aqueous solution of sodium sulfide, and the concentration of sulfide ions is 0.1 - 2 mol L-1 ; The vulcanization treatment time is 1 min - 24 h. Preferably, the vulcanization treatment is carried out at room temperature.

[0025] The second technical solution adopted to achieve the second object of the present invention is: to provide an electrolytic cell, including: a cathode chamber, an anode chamber, a cathode electrode, an anode electrode, an ion exchange membrane, a cathode electrolyte, an anode electrolyte, and a tab;

[0026] The anode electrode adopts a high-entropy metal sulfide electrode material prepared by the preparation method according to the first object of the present invention; the cathode electrode adopts a Pt / C electrode; the anode electrolyte adopts a sulfur ion-containing solution with a sulfur ion concentration of 0.01 - 4 mol L -1 ; the cathode electrolyte adopts an aqueous sodium hydroxide solution with a concentration of 0.01 - 6 mol L -1 ; the ion exchange membrane adopts a carbon-modified sodium ion exchange membrane.

[0027] In the electrolytic cell provided by the present invention, a hydrogen evolution reaction occurs in the cathode chamber, and a sulfur ion oxidation reaction occurs in the anode chamber. The cathode and anode chambers are separated by an ion exchange membrane, which only conducts sodium ions to achieve charge balance and at the same time avoids the anion shuttle effect. The electrolytic cell is electrolyzed under constant potential or constant current conditions, and hydrogen and concentrated sodium hydroxide solution are obtained at the cathode end, and sodium polysulfide solution is obtained at the anode end.

[0028] Furthermore, the electrolytic cell adopts a flow mode, and the cathode electrolyte and the anode electrolyte are separately filled in two containers and circulated by a peristaltic pump. The electrolytic cell is equipped with a heating device and can be electrolyzed under heating conditions.

[0029] Furthermore, to prevent sulfur ions or alkali from corroding the electrolytic cell housing, the electrolytic cell body in contact with the solution is made of corrosion-resistant materials, including polytetrafluoroethylene, plexiglass, etc.

[0030] Preferably, the sulfur ion-containing solution includes one of sodium sulfide and potassium sulfide, and the sulfur ion exists in the form of HS - .

[0031] Preferably, the pH of the sulfur ion-containing solution is 12 - 14, and the temperature is 20 - 80 °C.

[0032] Further, the ion exchange membrane is a carbon-modified sodium ion exchange membrane, and its preparation method includes the following steps: using a Nafion membrane as the base membrane, first pretreating the base membrane with an aqueous sodium hydroxide solution to obtain a sodium ion exchange membrane; then coating a mixed slurry of porous carbon and a binder on the surface of the sodium ion exchange membrane, drying it, and immersing it in deionized water for storage. Through a large number of studies, it is found that in the electrolytic cell provided by the present invention, the carbon-modified sodium ion exchange membrane can adsorb anions and form an anion electrostatic repulsion layer, effectively avoiding the occurrence of anion shuttle phenomenon.

[0033] Preferably, in the preparation method of the carbon-modified sodium ion exchange membrane, the concentration of the aqueous sodium hydroxide solution is 0.1 - 6 mol L -1 , the pretreatment temperature is 70 - 90 °C, and the pretreatment time is 1 - 4 h; the porous carbon includes one or a combination of activated carbon, Super P, carbon black, etc.; the binder includes polyvinylidene fluoride or polytetrafluoroethylene. The mixed slurry uses water or an organic solvent such as N-methylpyrrolidone as a dispersant.

[0034] The technical solution adopted by the present invention to achieve the third object is: to provide an application of the electrolytic cell according to the second object of the present invention in a sulfur ion oxidation-assisted electrolytic water hydrogen production system.

[0035] Further, the application includes: under constant potential or constant current conditions, performing electrolysis operation on the electrolytic cell to obtain hydrogen and concentrated sodium hydroxide solution at the cathode end, and obtaining sodium polysulfide solution at the anode end.

[0036] Preferably, the constant potential voltage range is 0.1 - 1.5 V vs. reversible hydrogen electrode (RHE), and the constant current density range is 0.1 - 1 A cm -2 .

[0037] Further, in the electrolytic cell, the anolyte is a sulfur ion-containing waste liquid obtained by adsorbing hydrogen sulfide waste gas produced in industry (such as in the petrochemical industry) with an alkaline solution. By constructing a sulfur ion oxidation-assisted electrolytic water hydrogen production system, the present invention uses a sulfur ion oxidation reaction with a lower oxidation potential to replace the conventional oxygen evolution reaction and couple it with the hydrogen evolution reaction, not only greatly reducing the electrolysis voltage and hydrogen production cost, but also being able to treat industrial wastewater containing sulfur ion waste liquid.

[0038] Further, the application also includes: adding concentrated sulfuric acid to the sodium polysulfide solution obtained at the anode end to obtain a yellow precipitate, and obtaining sulfur through filtration and washing.

[0039] The electrolytic cell structure provided by the present invention replaces the traditional alkaline water electrolysis ion exchange membrane with a carbon-modified sodium ion exchange membrane, hinders the anion from shuttling between the anode and cathode through the anion repulsion shielding effect, and applies the above-mentioned high entropy metal sulfide electrode as an anode catalytic material to a flow cell electrolysis system for sulfide ion oxidation-assisted water electrolysis to produce hydrogen, catalyzes the oxidation of sulfur ions into polysulfides, recovers sulfur element after acidification, and realizes the treatment of sulfur-containing wastewater and resource utilization.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention provides a method for preparing a high-entropy metal sulfide electrode material, which has the advantages of mild synthesis conditions, no need for high-temperature sintering, simple and controllable preparation process, high efficiency and low cost. The preparation method aims to solve the problem of poor activity and stability of catalytic materials for sulfur ion oxidation reaction, and synthesizes an amorphous high-entropy metal sulfide with a "soft-hard" acid site gradient in situ grown on the substrate surface. The catalytic electrode can drive the sulfur ion oxidation reaction to 100 mA cm with only 0.25 V vs. RHE. -2 The electrolysis can be continued stably for 120 h at a current density of 10000 m / s and can be stably electrolyzed at a low overpotential at an industrial current density, maintaining high activity and stability.

[0042] (2) The present invention provides an electrolytic cell for a sulfide ion oxidation-assisted water electrolysis hydrogen production system, in which the anode electrode is made of a high-entropy metal sulfide electrode material, which can promote the efficiency of the sulfide ion oxidation reaction, improve the activity and stability, and meet the application requirements under industrial-grade current density. At the same time, the electrolytic cell uses a carbon-modified sodium ion exchange membrane, which can effectively avoid sulfide ion shuttling, improve the efficiency and purity of cathode hydrogen production, and is also beneficial to the recovery of alkaline solution in the cathode. The electrolytic cell provided by the present invention consumes only 1.64 kWh of electricity per standard cubic meter of hydrogen (based on 200 mA cm -2 Current density calculation), which is higher than the current mainstream alkaline electrolyzed water (4-5 kwh / Nm 3 ) and PEM electrolyzed water (3.8-4.5 kwh / Nm 3 )’s energy consumption is significantly reduced.

[0043] (3) The electrolytic cell provided by the present invention is applied to a two-electrode system for sulfur ion oxidation-assisted electrolytic hydrogen production. The sulfur ion-containing waste liquid obtained by adsorbing hydrogen sulfide waste gas produced in industry with an alkaline solution can be used as the anolyte. It can not only meet the production requirements of low voltage, industrial-grade high current density, and high stability, but also realize the treatment and resource utilization of sulfur ion-containing wastewater, and synchronously and efficiently complete operations such as hydrogen production, sodium hydroxide lye recovery, sulfur-containing waste liquid treatment, and sulfur element recovery. The present invention is of great significance for waste liquid recovery and resource utilization, low-energy-consumption and high-efficiency hydrogen production, and environmental protection, and has broad promotion and application prospects. Description of the Drawings

[0044] Figure 1 X-ray diffraction pattern of the high-entropy metal sulfide CuNiCoMnCrS x / NF and its precursor CuNiCoMnCr(OH) x / NF electrode;

[0045] Figure 2 X-ray diffraction pattern of the high-entropy metal sulfide CuNiCoMnCrS x Scanning electron microscope image of the / NF electrode;

[0046] Figure 3 X-ray diffraction pattern of the high-entropy metal sulfide CuNiCoMnCrS x Polarization curve of the / NF electrode for catalytic anodic sulfur ion oxidation, 90% iR correction;

[0047] Figure 4 Schematic structural diagram of the electrolytic cell for sulfur ion oxidation-assisted electrolytic hydrogen production provided in Application Example 1 of the present invention;

[0048] Figure 5 LSV curve of the electrolytic cell provided in Application Example 2 of the present invention, without iR correction;

[0049] Figure 6 Stability test diagram of the electrolytic cell provided in Application Example 3 of the present invention;

[0050] Figure 7 XRD pattern of the sulfur element obtained in Application Example 4 of the present invention;

[0051] Figure 8 Schematic diagram of the reaction mechanism for sulfur ion oxidation-assisted electrolytic hydrogen production with sulfur-containing wastewater as the anolyte provided in Application Example 5 of the present invention. Detailed Embodiments

[0052] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the scope of protection of the present invention.

[0053] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0054] The embodiment of the present invention provides a preparation method of a high-entropy metal sulfide electrode material, including the following steps:

[0055] Step 1: Mix at least five metal nitrate solutions containing different transition metal ions to obtain a mixed metal nitrate solution; in the mixed metal nitrate solution, the transition metal ions include Cu 2+ , Ni 2+ , Co 2+ , Fe 2+ , Mn 2+ , Fe 3 + , Cr 3+ and at least five of them, and the total concentration of the transition metal ions is 0.01 - 0.1 mol L -1 .

[0056] Step 2: Construct a three-electrode system with the substrate material as the working electrode, the saturated calomel electrode as the reference electrode, and the Pt sheet as the counter electrode; the substrate material includes one of nickel foam, carbon paper, carbon cloth, and conductive glass (indium tin oxide, fluorine-doped indium tin oxide).

[0057] Step 3: Use the mixed metal nitrate solution as the electrolyte of the three-electrode system, and perform electrodeposition for 10 - 2000 s under the conditions of a constant potential mode and a deposition potential of -0.5 to -1.5 V to obtain a metal hydroxide electrode precursor.

[0058] Step 4: Place the metal hydroxide electrode precursor in an aqueous solution of sodium sulfide with a sulfur ion concentration of 0.1 - 2 mol L -1 , and perform sulfidation treatment at room temperature for 1 min - 24 h. The product is washed and dried to obtain the high-entropy metal sulfide electrode material.

[0059] The present invention will be further described below in conjunction with specific embodiments, but it is not a limitation of the present invention.

[0060] Example 1

[0061] A preparation method of a high-entropy metal sulfide / nickel foam electrode material, comprising the following steps:

[0062] Step 1: Take 0.25 mmol of metal nitrates (copper nitrate, nickel nitrate, cobalt nitrate, manganese nitrate, chromium nitrate, a total of 1.25 mmol) and dissolve them in 50 mL of water, stir until the solution is evenly mixed to obtain a mixed metal nitrate solution;

[0063] Step 2: Immerse nickel foam (with a thickness of 1 mm) successively in HCl solution, deionized water, and absolute ethanol, and ultrasonically clean to remove impurities, then dry to obtain a substrate material; use the substrate material as the working electrode, a saturated calomel electrode as the reference electrode, and a Pt sheet as the counter electrode to construct a three-electrode system;

[0064] Step 3: Using the mixed metal nitrate solution prepared in Step 1 as the electrolyte, perform electrodeposition with the three-electrode system in Step 2, the deposition potential is -1 V vs. SCE, the deposition time is 1200 s, after the electrodeposition is completed, take out the electrode, rinse it with water and dry it at room temperature to obtain a metal hydroxide electrode precursor;

[0065] Step 4: Immerse the metal hydroxide electrode precursor obtained in Step 3 into a 1 mol L -1 Na 2 S solution and keep it for 12 h, after complete sulfidation, take it out, wash it with deionized water and absolute ethanol, and dry it to obtain a high-entropy metal sulfide CuNiCoMnCrS x / NF electrode.

[0066] Figure 1 The XRD patterns of the electrode precursor and the electrode material show that a metal hydroxide structure grows in-situ on the surface of the electrodeposited nickel foam. After sulfidation, the peaks belonging to the hydroxide disappear and no new characteristic peaks appear, indicating that amorphous sulfide crystals are produced during the sulfidation process.

[0067] Figure 2 It can be seen from the scanning electron microscope pictures in

[0068] Furthermore, perform three-electrode electrochemical performance tests on the high-entropy metal sulfide / nickel foam electrode prepared in Example 1 to investigate the activity and stability of electrochemically oxidizing sulfide ions: use the high-entropy metal sulfide CuNiCoMnCrS x / NF electrode (anode) prepared in Example 1, use a 1 mol L -1 NaOH + 1 mol L -1 Na 2 S solution as the electrolyte for the anode part (pH = 13 - 14), and use a 1 mol L -1An aqueous NaOH solution is used as the cathode (hydrogen evolution reaction) electrolyte, a Pt sheet electrode is used as the counter electrode (cathode), a saturated calomel electrode is used as the reference electrode, and the cathode and anode chambers are separated by a Nafion 117 membrane.

[0069] Figure 3 The polarization curve (LSV curve) of the electrode material prepared in Example 1 applied to the electrocatalytic oxidation reaction of sulfide ions under a three-electrode system. Figure 3 It can be seen that current densities of 100 and 400 mA cm -2 can be obtained at potentials of 0.25 and 0.30 V vs. RHE, respectively.

[0070] Example 2

[0071] The difference between this example and Example 1 is as follows:

[0072] In step 1, 0.25 mol of each metal nitrate (ferrous nitrate, nickel nitrate, cobalt nitrate, manganese nitrate, chromium nitrate, a total of 1.25 mol) is dissolved in 50 mL of water, and the solution is stirred until evenly mixed to obtain a mixed metal nitrate solution.

[0073] The remaining steps and operations remain unchanged to obtain a high-entropy metal sulfide FeNiCoMnCrS x / NF electrode.

[0074] Example 3

[0075] The difference between this example and Example 1 is as follows:

[0076] In step 1, 0.25 mol of each metal nitrate (copper nitrate, nickel nitrate, cobalt nitrate, manganese nitrate, iron nitrate, a total of 1.25 mol) is dissolved in 50 mL of water, and the solution is stirred until evenly mixed to obtain a mixed metal nitrate solution.

[0077] The remaining steps and operations remain unchanged to obtain a high-entropy metal sulfide CuNiCoMnFeS x / NF electrode.

[0078] Application Example 1

[0079] This application example provides an electrolytic cell for hydrogen production by electrolyzing water assisted by sulfide ion oxidation. Its structural schematic diagram is as Figure 4 shown, including: a cathode chamber, an anode chamber, a cathode electrode, an anode electrode, an ion exchange membrane, and a tab. It is fixed by long screws through a polytetrafluoroethylene module to form a sealed electrolytic cell. The cathode and anode electrolytes enter the chamber from the liquid inlet and are discharged from the liquid outlet to achieve a flowing cycle.

[0080] This electrolytic cell uses the high-entropy metal sulfide CuNiCoMnCrS prepared in Example 1x The / NF electrode is the anode electrode, with a 3 mol L -1 Na 2 S solution as the electrolyte for the anode part (pH = 13 - 14), a 1 mol L -1 NaOH aqueous solution as the cathode (hydrogen evolution reaction) electrolyte, and a Pt / C-loaded carbon paper electrode as the counter electrode (cathode). The anode and the cathode are both welded to nickel tabs, with an area of 1 × 1 cm 2 . The anode and the cathode are in close contact with the ion exchange membrane to reduce the internal resistance of the system.

[0081] Among them, the ion exchange membrane is a carbon-modified sodium ion exchange membrane, and its preparation method is as follows: Using a Nafion membrane as the base membrane, treating it with a 1 mol L -1 NaOH aqueous solution at 80 °C and soaking it in deionized water for cation replacement to make the Nafion membrane a Na ion exchange membrane. Coating a slurry (using N-methylpyrrolidone as a dispersant) of activated carbon and binder polyvinylidene fluoride mixed in a mass ratio of 9:1 on the surface of the substrate, and drying and immersing it in deionized water for storage.

[0082] Both the anode and cathode electrolytes are 100 mL, stored in a closed container. The electrolytic cell is heated to 80 °C to promote the kinetic activity of the electrode reaction and reduce the mass transfer internal resistance. The anode and cathode electrolytes are introduced into the electrolytic cell by a pump, with a flow rate of 100 sccm for both.

[0083] Application Example 2

[0084] Under a two-electrode system, the electrolysis voltage and current density of the electrolytic cell provided in Application Example 1 are tested. Among them, the anode electrolyte is a 3 mol L -1 Na 2 S aqueous solution, and the cathode electrolyte is a 1 mol L -1 NaOH aqueous solution. The polarization curve is tested at a scan rate of 10 mV s -1 , and the temperature is 80 °C. According to Figure 5 the LSV curve (without iR correction) of the electrolytic cell in -2 it can be seen that the electrolytic cell provided by the present invention has an initial voltage of only ~0.3 V in the two-electrode system, and when the current density reaches 200 mA cm

[0085] Application Example 3

[0086] Under a two-electrode system, the stability of the electrolytic cell provided in Application Example 1 is tested. Among them, the anode electrolyte is a 3mol L -1 Na 2 S aqueous solution, and the cathode electrolyte is a 1 mol L -1NaOH aqueous solution. Constant current electrolysis was performed at 80 °C and a current density of 200 mA cm -2 .like Figure 6 As shown, the electrolytic cell provided by the present invention has no obvious attenuation in the two-electrode system during continuous electrolysis for 192 h (the electrolyte is replaced every 12 h), and the voltage is maintained at ~0.8 V.

[0087] Application Example 4

[0088] The sodium polysulfide obtained from the electrolyzed sulfur ion oxidation anode electrolyte obtained in Application Example 3 is further acidified to produce elemental sulfur, and the specific method is as follows:

[0089] The sodium polysulfide solution produced by the oxidation of sulfur ions in the anode electrolyte was used as a substrate, and concentrated sulfuric acid was added dropwise to the substrate solution to precipitate sulfur. The sulfur was filtered, washed, and dried to obtain elemental sulfur. XRD characterization test confirmed that S 8 powder( Figure 7 ), with a purity greater than 98wt.%.

[0090] Application Example 5

[0091] The electrolytic cell provided by Application Example 1 is used, and the anolyte in Application Example 1 is replaced by the waste liquid containing sulfur ions to perform sulfur ion oxidation-assisted water electrolysis to produce hydrogen. Figure 8 The figure is a schematic diagram of the reaction mechanism. The sulfur ion-containing waste liquid is obtained by adsorbing hydrogen sulfide waste gas produced in the petrochemical industry through alkaline solution.

[0092] like Figure 8 As shown, the sulfur-containing wastewater is used as the anolyte to flow into the anode chamber through a flow pump, and the sodium hydroxide solution is used as the cathode electrolyte to flow into the cathode chamber. A carbon-modified sodium ion exchange membrane is used in the middle to block and transfer ions. During electrolysis, sodium ions are continuously transferred from the anode to the cathode, and hydrogen precipitation reaction occurs at the cathode to generate high-purity hydrogen. The pH value increases due to the continuous consumption of hydrogen ions, and alkali concentration and recovery are achieved; at the same time, the sulfur ions in the anolyte are continuously oxidized to polysulfides. After the electrolysis is completed, an acidic substance is added to the polysulfide solution for neutralization, and the sulfur element is precipitated and filtered to recover sulfur resources.

[0093] In this application example, by constructing a sulfur ion oxidation-assisted water electrolysis hydrogen production system, the sulfur ion oxidation reaction with a lower oxidation potential is used to replace the conventional oxygen evolution reaction and coupled with the hydrogen evolution reaction, thereby greatly reducing the electrolysis voltage and hydrogen production cost. The high entropy metal sulfide electrode material is used as the anode electrode in the flow cell electrolysis system for sulfur ion oxidation-assisted water electrolysis hydrogen production, catalyzing the oxidation of sulfur ions into polysulfides, and recovering sulfur after acidification. The overall process can simultaneously produce hydrogen, recover alkali, and remove and recycle sulfur ions.

[0094] The above are only preferred embodiments of the present invention, and thus do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all the solutions obtained by equivalent substitution and obvious changes made by using the content of the specification of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high entropy metal sulfide electrode material, characterized in that: The following steps are involved: S1. Mix at least five metal nitrate solutions containing different transition metal ions to obtain a metal nitrate mixed solution; in the metal nitrate mixed solution, the transition metal ions include Cu 2+ 、Ni 2+ 、Co 2+ , Fe 2+ , Mn 2+ , Fe 3+ Cr 3+ At least five of the following; S2, using the substrate material as the working electrode, the saturated calomel electrode as the reference electrode, and the Pt sheet as the counter electrode to construct a three-electrode system; S3, using the metal nitrate mixed solution as the electrolyte of the three-electrode system, and performing electrodeposition for 10-2000s in a constant potential mode at a deposition potential of -0.5 to -1.5 V to obtain a metal hydroxide electrode precursor; S4, placing the metal hydroxide electrode precursor in a sulfur-containing solution for sulfurization treatment, wherein the sulfur-containing solution is an aqueous solution of sodium sulfide, and the concentration of sulfur ions is 0.1-2 mol L -1 The sulfurization treatment time is 1min-24h; after cleaning and drying, a high entropy metal sulfide electrode material is obtained.

2. The preparation method according to claim 1, characterized in that In step S1, the total concentration of transition metal ions in the metal nitrate mixed solution is 0.01-0.1 mol L -1 .

3. The preparation method according to claim 1, characterized in that: In step S2, the base material includes one of nickel foam, carbon paper, carbon cloth, and conductive glass.

4. An electrolytic cell comprising: A cathode chamber, an anode chamber, a cathode electrode, an anode electrode, an ion exchange membrane, a cathode electrolyte, an anode electrolyte and an electrode ear, characterized in that: The anode electrode is made of a high entropy metal sulfide electrode material prepared by the preparation method according to any one of claims 1 to 3; the cathode electrode is made of a Pt / C electrode; The anolyte solution has a sulfur ion concentration of 0.01-4 mol L -1 The cathode electrolyte has a concentration of 0.01-6 mol L -1 The ion exchange membrane is a carbon-modified sodium ion exchange membrane.

5. The electrolytic cell according to claim 4, characterized in that The preparation method of the carbon-modified sodium ion exchange membrane comprises the following steps: using a Nafion membrane as a base membrane, pre-treating the base membrane with a sodium hydroxide aqueous solution to obtain a sodium ion exchange membrane; and then coating a mixed slurry of porous carbon and a binder on the surface of the sodium ion exchange membrane, drying it, and immersing it in deionized water for storage.

6. The electrolytic cell according to claim 4 or 5 is used in a sulfide ion oxidation assisted water electrolysis hydrogen production system, characterized in that: The electrolytic cell is subjected to electrolysis operation under constant potential or constant current conditions to obtain hydrogen and concentrated sodium hydroxide solution at the cathode end and sodium polysulfide solution at the anode end; The voltage of the constant potential is 0.01-1.5 V vs. reversible hydrogen electrode; the current density of the constant current is 0.01-1 A cm -2 .

7. The use according to claim 6, characterized in that: In the electrolytic cell, the anode electrolyte adopts sulfur ion-containing waste liquid; the sulfur ion waste liquid is prepared by adsorbing hydrogen sulfide waste gas through alkaline solution.

8. The use according to claim 6, characterized in that: The application also includes: adding concentrated sulfuric acid to the sodium polysulfide solution obtained at the anode end to obtain a yellow precipitate, and filtering and washing to obtain sulfur.

Images