Preparation method and application of medium-entropy sulfide electrolyzed water catalyst based on crystal structure regulation and control

Abstract

The invention belongs to the technical field of preparation of anion exchange membrane electrolyzed water catalysts, and particularly relates to a method for preparing medium-entropy sulfide based on crystal structure regulation and control and electro-deposition and application of the medium-entropy sulfide. The preparation method comprises the following steps: mixing choline chloride and ethylene glycol to prepare an ionic liquid (DEIL); and adding metal salt and thiourea into DEIL, stirring to form a uniform solution, and carrying out electro-deposition in a three-electrode system to prepare the amorphous medium-entropy sulfide catalyst. The catalyst has the catalytic advantages of an amorphous material and a medium-entropy sulfide, can significantly improve the OER performance in electrolyzed water, and has the advantages of good repeatability, high stability and excellent catalytic performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of anion exchange membrane water electrolysis catalyst preparation, and specifically relates to a method and application of preparing medium-entropy sulfide by electrodeposition based on crystal structure regulation. Background Art

[0002] The increasingly severe environmental crisis urgently requires the development of green and renewable energy technologies. Among them, anion exchange membrane water electrolysis technology stands out as a promising clean energy generation pathway. However, the oxygen evolution reaction (OER) in the electrolysis process remains a major bottleneck due to its inevitably slow reaction kinetics. Traditionally, noble metal catalysts RuO2 and IrO2 have been widely used for OER due to their high activity and stability. However, the high cost and limited supply of noble metals restrict their commercial application. This has led to an urgent need for efficient non-noble metal catalysts to reduce the OER overpotential.

[0003] Transition metal sulfides have significant advantages as catalysts in the OER process due to their unique and tunable electronic structure. However, most crystalline sulfide catalysts often face the challenges of structural instability and loss of active sites during water electrolysis. In contrast, amorphous catalysts have abundant surface active sites, excellent physicochemical tunability, and stability advantages over crystalline materials. However, the preparation of amorphous catalysts with high-performance OER is challenging.

[0004] As an emerging multi-component system, intermediate-entropy sulfides, with their unique lattice distortion and cocktail effect, have shown great potential in the field of catalysis. Developing high-performance amorphous catalysts based on intermediate-entropy sulfides is an important direction to break through the bottleneck of OER kinetics. Summary of the Invention

[0005] Based on this, the present invention provides a method for preparing a medium-entropy sulfide water electrolysis catalyst based on crystal structure regulation and its application. The medium-entropy sulfide is grown on nickel foam (NF) by electrodeposition. An ionic liquid (DEIL) is prepared by mixing choline chloride and ethylene glycol. A metal salt and thiourea are added to the DEIL, stirred to form a homogeneous solution, and then an amorphous medium-entropy sulfide catalyst is prepared by electrodeposition in a three-electrode system.

[0006] The present invention uses ionic liquid as the electrolyte and prepares a medium-entropy sulfide material with an amorphous structure through a one-step electrodeposition reaction. By gradually adding metals to the precursor solution, the material is promoted to transform from a crystalline structure to an amorphous structure, so that it has the catalytic advantages of both amorphous materials and medium-entropy sulfides. Using it as a catalyst for electrocatalytic water decomposition can effectively accelerate the charge transfer rate during the electrolysis reaction and significantly improve the OER performance in electrolysis water. It has the advantages of good repeatability, high stability and excellent catalytic performance.

[0007] As a preferred embodiment of the present invention, the temperature of the electrodeposition reaction is 20-80°C; the reaction time is 600 s-7200 s, and the deposition potential is -0.7 V to -1.5 V.

[0008] Preferably, in step (1), the temperature of the electrodeposition reaction is 60-80°C, and the electrodeposition time is 900-1500 s; As a preferred embodiment of the present invention, the ratio of the total molar number of metal elements to the molar number of sulfur elements is 1:2. The material prepared under the above ratio has excellent catalytic performance.

[0009] By adding metal elements, the crystallinity of the catalyst can be regulated, further significantly improving the activity of the water electrolysis catalyst. When the added metal elements are Ni, Fe, Co, and W, the catalytic activity of the material is the best. Specifically: in 1 M KOH electrolyte, OER produces 100 mA cm -2 The current density of 100 h@100 mA cm-3 was achieved with a low overpotential of only 249 mV and a Tafel slope of 43 mV / dec. -2 Shows higher stability.

[0010] Compared with the existing technology, the beneficial effects of the present invention are: the present invention adopts a one-step electrodeposition preparation method, the synthesis process is simple and environmentally friendly, the prepared amorphous mesotropic sulfide material can quickly promote the catalyst to produce a truly active phase, and has the potential to be applied on a large scale in the electrolysis of water to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION

[0011] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0012] Where specific techniques or conditions are not specified in the examples, all methods were performed according to conventional methods, techniques or conditions described in literature in the field, or according to product specifications. Reagents and instruments used, for which the manufacturers are not specified, are conventional products that can be purchased through regular channels.

[0013] The preparation process flow chart of the amorphous medium entropy sulfide material of the present invention is as follows: Figure 1 shown.

[0014] Example 1.

[0015] This example provides an amorphous mesotropic sulfide material, prepared as follows: 1) 100 mM choline chloride and 400 mM ethylene glycol were mixed in a 100 mL reagent bottle to obtain solution A. 2) 22.5 mM NiCl2·6H2O, 13.5 mM FeCl3·6H2O, 3 mM WCl6, and 13.5 mM CoCl2·6H2O were weighed and added to solution A, stirring for 30 minutes to obtain solution B. 3) 22.5 mM CH4N2S was added to solution B, and ultrasonic stirring was performed for 30 minutes to obtain solution C. 4) Electrodeposition was performed in a CHI760E electrochemical workstation using an Ag / AgCl reference electrode, a nickel foam (1 cm × 2 cm) working electrode, and a platinum mesh electrode as a counter electrode at 60°C. The electrochemical reaction was carried out using a constant potential method at -0.9 V for 900 s. 5) The product obtained in step 4 is centrifugally washed three times with anhydrous ethanol and dried in an oven to obtain an amorphous mesotropic sulfide material NiFeCoWS electrode.

[0016] Comparative Example.

[0017] This comparative example provides three sulfide materials, and the preparation methods thereof differ from those in Example 1 only in that in step 2, the electrolyte formulas are NiCl2·6H2O, NiCl2·6H2O+FeCl3·6H2O, and NiCl2·6H2O+FeCl3·6H2O+CoCl2·6H2O, respectively, and the remaining electrodeposition steps remain the same.

[0018] Test example 1.

[0019] The structure and morphology of the materials prepared in the above examples were characterized.

[0020] like Figure 2 As shown, X-ray diffraction (XRD) analysis reveals that all materials exhibit peaks characteristic of the nickel foam support, while the NiFeCoWS catalyst exhibits only a broad amorphous peak, confirming its amorphous structure. In contrast, the spectra of the comparative catalysts (NiS, NiFeS, and NiFeCoS) are similar to those of Ni3S2, with the crystallinity gradually decreasing with increasing doping levels. This suggests that metal doping effectively promotes the catalyst's transition to an amorphous structure.

[0021] Figure 3 a shows the morphology of NiFeCoWS, which exhibits a nanoflower morphology formed by vertical growth and stacking of nanosheets, similar to the morphologies of NiS, NiFeS, and NiFeCoS (see Figure 4a). The transmission electron microscopy (TEM) image in the inset further confirms the nanoflower morphology, indicating that the stacking of nanosheets forms an effective electron / ion transport channel, enhancing the exposure of reaction sites and thus improving the mass transfer rate. The high-resolution TEM image of NiFeCoWS does not show a clear lattice pattern, and the selected area electron diffraction (SAED) image in the inset shows only diffuse central spots in the catalyst, indicating that it has an amorphous structure ( Figure 3 b). Energy dispersive spectroscopy (EDS) mapping shows the presence of constituent elements, with Ni being the main element and the elements being evenly distributed ( Figure 3 c). In contrast, the clear lattice rings observed in NiS, NiFeS, and NiFeCoS indicate that these synthesized catalysts have crystalline structures ( Figure 4 bd). This indicates that the crystal structure of the catalyst was successfully regulated by adding metal elements for electrodeposition.

[0022] Test example 2.

[0023] In this test example, the OER performance of the materials prepared in the examples and comparative examples was tested in 1 M KOH solution.

[0024] like Figure 5 As shown in a, at 5 mV s -1 The linear sweep voltammetry (LSV) polarization curves of the intermediate entropy sulfide NiFeCoWS material were measured at a scan rate of 100 mA cm -2 The overpotential at the current density is the smallest, which is 249 mV. The Tafel curve is calculated based on the LSV curve to estimate the OER reaction kinetics, such as Figure 5 As shown in b, the Tafel slope of the medium-entropy sulfide NiFeCoWS material is the lowest, which is 41 mV dec. -1 , further indicating that NiFeCoWS has the best kinetic activity.

[0025] To further test the stability of the material, the long-term chronoamperometry was used to test the material electrode at 100 mA cm -2 Stability under constant current, such as Figure 6 As shown, the intermediate entropy sulfide NiFeCoWS material electrode only increased its voltage by 41.3 mV after 500 h of electrocatalysis, still retaining most of its initial activity.

[0026] NiS material: at 100mA cm -2 The overpotential at the current density is 409 mV ( Figure 5 a), Tafel slope is 197.33mV dec -1 ( Figure 5b) Increase the voltage by 248 mV in a short time, and the stability is poor ( Figure 6 illustration).

[0027] NiFeS material: at 100mA cm -2 The overpotential at the current density is 356 mV ( Figure 5 a), Tafel slope is 84.58mV dec -1 ( Figure 5 b).

[0028] NiFeCoS material: at 100mA cm -2 The overpotential at the current density is 337 mV ( Figure 5 a), Tafel slope is 46.55 mV dec -1 ( Figure 5 b).

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a medium-entropy sulfide material with an amorphous structure, characterized in that: include: (1) Ethylene glycol and choline chloride are mixed evenly to form an ionic liquid; (2) Different types of metal salts are added to the ionic liquid in sequence and mixed evenly, and then an electrodeposition reaction is carried out to gradually form a medium-entropy sulfide material with an amorphous structure.

2. The preparation method according to claim 1, characterized in that In step (1), the mass ratio of ethylene glycol to choline chloride in the ionic liquid is 1:1 to 4.

3. The preparation method according to claim 1, wherein in step (2), The temperature of the solvothermal reaction is 20~80℃; the reaction time is 600 s-7200 s, and the deposition potential is -0.7 V to -1.5 V.

4. The preparation method according to claim 1, wherein in step (2), The ratio of the total molar number of metal elements to the molar number of sulfur element is 1:

2.

5. The preparation method according to claim 1, wherein in step (2), The molar ratio of Fe, Co, Ni, and W metal elements is 1:0.8~1.2:0.8~1.2:0.8~1.

2.

6. The preparation method according to claim 1, wherein in step (2), The addition ratio of ionic liquid to inorganic salt was 18.25 ml:6 mM.

7. A medium-entropy sulfide material having an amorphous structure, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 5; its chemical formula is NiFeCoWS.

8. Use of the medium-entropy sulfide material with an amorphous structure according to claim 6 in hydrogen production by alkaline water electrolysis.

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