Preparation method of efficient electrocatalyst based on Fe7S8 / 1T MoS2 nanosheet array

Abstract

The invention discloses a preparation method of a Fe7S8 / 1T MoS2 nanosheet array based on efficient electro-catalysis application. According to the method, (NH4) 6Mo7O24. 4H2O, CH4N2S, L (+)-ascorbic acid and foam iron are adopted as main raw materials, the (NH4) 6Mo7O24. 4H2O and the CH4N2S are mixed through magnetic stirring, the L (+)-ascorbic acid is added, the mixed solution and the pretreated foam iron are sintered for 18 h at the temperature of 200 DEG C, and the target product is prepared. According to the method, foam iron is used as a substrate, so that the specific surface area of a sample is remarkably increased, surface active sites are increased, electron transmission is promoted, and the electro-catalytic performance and stability are improved. The method is simple to operate and clear in steps, has the advantages of environmental protection, economy, convenience, high repeatability and the like, and is easy to realize large-scale production.

Description

Technical Field

[0001] The present invention relates to a method for preparing a Fe7S8 / 1T MoS2 nanosheet array suitable for high-efficiency electrocatalytic applications. Specifically, the Fe7S8 / 1T MoS2 nanosheet array is grown on an iron foam (IF) substrate to form a material with high-efficiency electrocatalytic properties. Background Art

[0002] In recent years, water electrolysis technology has attracted widespread attention due to its advantages such as low cost, high efficiency, environmental friendliness and high safety. The water electrolysis process consists of two half reactions: hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode. Since pure water is not conductive, the electrolytes commonly used in laboratories are mainly sulfuric acid (H2SO4), potassium hydroxide (KOH) and phosphate buffer solution (PBS). The principle is to apply the catalysts of hydrogen evolution reaction and oxygen evolution reaction on the cathode and anode respectively, and then immerse them in the electrolyte solution. When a stable direct current passes through the circuit, hydrogen ions consume electrons at the cathode to generate hydrogen, and hydroxide ions lose electrons at the anode to generate oxygen. The currently used precious metal electrocatalysts such as Pt and RuO2 / IrO2 are expensive, which limits the large-scale promotion of water electrolysis. Therefore, it is urgent to find a cheap and efficient electrocatalyst to reduce the overpotential of hydrogen evolution and oxygen evolution reactions and improve the efficiency of electrocatalysis. Transition metals have the advantages of low price and adjustable structure and morphology, which have led to a large number of studies and applications in the field of electrocatalysis. Molybdenum disulfide (MoS2) is the most widely studied two-dimensional material besides graphene. It has the advantages of low cost, abundant reserves and easy structural control. More importantly, the ΔGH* of the edge site of MoS2 is only 0.08 eV, which is even better than the commercial electrocatalyst precious metal Pt. Therefore, MoS2 is considered to be the most promising alternative to the precious metal Pt. Depending on the atomic arrangement and unit cell structure, MoS2 can be mainly divided into semiconductor 2H phase and metallic 1T phase. The research on the semiconductor 2H phase was the earliest, but it has been limited by problems such as fewer edge sites and low electron mobility. The metallic phase 1T-MoS2 has richer active sites and higher electron mobility (about 10 of the 2H phase). 7 times). Therefore, the catalytic activity of the metal phase 1T-MoS2 is much higher than that of the semiconductor 2H-MoS2. However, since the powder sample is easy to agglomerate and fall off during the electrocatalytic water splitting process, its stability and electrocatalytic efficiency will be reduced. Summary of the invention

[0003] To solve the above problems, the present invention adopts a simple one-step hydrothermal method to (NH4)6Mo7O 24· 4H2O, CH4N2S, L(+)-ascorbic acid and foamed iron are used as the main raw materials to grow 1T-MoS2 in situ on the foamed iron substrate. On the one hand, it can effectively improve the dispersibility, active specific surface area and chemical stability, and on the other hand, the interaction between Fe7S8 and 1T-MoS2 can effectively regulate the interface electronic structure, promote the rapid migration of carriers, and improve the electrocatalytic efficiency.

[0004] The present invention proposes a method for preparing a high-efficiency electrocatalyst based on Fe7S8 / 1T MoS2 nanosheet array, and the specific steps are as follows: (1) Pretreatment of the foamed iron: using acetone and deionized water to clean and remove impurities on the surface of the foamed iron and then drying it; wherein the drying condition is preferably vacuum drying at 60°C for 6 hours.

[0005] (2) Preparation of Fe7S8 / 1T MoS2 electrocatalyst: a. Add 0.8~1.2 mmol (NH4)6Mo7O to 20 mL of deionized water. 24 4H2O and 11.2~16.8 mmolCH4N2S are stirred and dissolved; b. Add 0.0145-0.0155 g of L(+)-ascorbic acid to the solution and stir for 5 min. c. Transfer the mixed solution into a 25 mL autoclave, insert the treated foam iron, and heat at 200 °C for 18 h; d. After naturally cooling to room temperature, the foamed iron is taken out, washed with deionized water and anhydrous ethanol, and dried to obtain the Fe7S8 / 1T MoS2.

[0006] Beneficial effects of the present invention: 1. The present invention adopts a simple one-step hydrothermal method to synthesize Fe7S8 / 1T MoS2 and prepares a highly efficient electrocatalyst suitable for electrocatalytic applications.

[0007] 2. The method of the present invention uses foamed iron as the substrate, which significantly increases the specific surface area of ​​the sample, increases the surface active sites, promotes electron transport, and improves the electrocatalytic performance and stability.

[0008] 3. The present invention is not only simple to operate and has clear steps, but also has the advantages of being green, environmentally friendly, economical, convenient, and highly repeatable, and is easy to realize large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 These are the X-ray diffraction patterns of the target products 1T-MoS2, Fe7S8, and Fe7S8 / 1T MoS2 of the present invention.

[0010] Figure 2 The scanning image (a) and contact angle (b) of the target product Fe7S8 of the present invention are shown.

[0011] Figure 3 The scanning image (a) and contact angle (b) of the target product 1T-MoS2 of the present invention.

[0012] Figure 4 The scanning image (a) and contact angle (b) of the target product Fe7S8 / 1T MoS2 of the present invention are shown.

[0013] Figure 5 The linear sweep voltammetric curves (a) and stability test diagram (b) of hydrogen production of the target products 1T-MoS2, Fe7S8, and Fe7S8 / 1T MoS2 of the present invention.

[0014] Figure 6 The linear sweep voltammetric curves (a) and stability test diagram (b) of oxygen production of the target products 1T-MoS2, Fe7S8, and Fe7S8 / 1T MoS2 of the present invention are shown.

[0015] Figure 7 The linear sweep voltammetric curve (a) and stability test (b) of the target product Fe7S8 / 1T MoS2 for the complete decomposition of water are shown in FIG. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further explained and illustrated in the form of specific embodiments below.

[0017] The raw materials required for the present invention are as follows: Ammonium molybdate ((NH4)6Mo7O 24 4H2O, Sinopharm Chemical Reagent Co., Ltd.) was analytically pure; Thiourea (CH4N2S, Sinopharm Chemical Reagent Co., Ltd.) was of analytical grade; L(+)-ascorbic acid (Sinopharm Chemical Reagent Co., Ltd.) was analytically pure; Acetone (CH3COCH3, Sinopharm Chemical Reagent Co., Ltd.) was of analytical grade.

[0018] (1) Pretreatment of foamed iron: Take foam iron (20 mm × 30 mm), wash it with acetone and deionized water for several times to remove surface impurities, and dry it in vacuum at 60°C for 6 h.

[0019] (2) Preparation of Fe7S8 / 1T MoS2: Add 1mmol (NH4)6Mo7O in 20mL deionized water 24·4H2O and 14mmol CH4N2S were stirred for 30min; then 0.015g (0.085mol) of L(+)-ascorbic acid was added to the solution and stirred for 5min; finally, the mixed solution was transferred to a 25ml autoclave, and the treated foam iron was inserted, heated at 200℃ for 18h, and then naturally cooled to room temperature, the foam iron was taken out, washed with deionized water and anhydrous ethanol for 3 times, and dried at 60℃ for 6h.

[0020] (3) Preparation of Fe7S8: Add 14 mmol CH4N2S to 20 mL deionized water and stir for 30 min; transfer the mixed solution to a 25 ml autoclave and insert the treated foam iron, heat at 200 °C for 18 h, then cool naturally to room temperature, take out the foam iron, wash it three times with deionized water and anhydrous ethanol, and dry it at 60 °C for 6 h.

[0021] (4) Preparation of 1T-MoS2: Add 1mmol (NH4)6Mo7O in 20mL deionized water 24 ·4H2O and 14mmol CH4N2S were stirred for 30min; then 0.015g of L-Ascorbic acid was added to the solution and stirred for 5min; finally, the mixed solution was transferred to a 25ml autoclave, heated at 200℃ for 18h, then naturally cooled to room temperature, centrifuged three times with deionized water and anhydrous ethanol, and dried at 60℃ for 6h.

[0022] Figure 1 It is the X-ray diffraction diagram of the target product 1T-MoS2, Fe7S8, and Fe7S8 / 1T MoS2 of the present invention. It can be seen from the figure that all the diffraction peaks in the Fe7S8 sample correspond to the Fe7S8PDF#24-0220 structure, MoS2 presents a 1T phase structure, and the diffraction peaks of 1T-MoS2 / Fe7S8 contain the structures of both Fe7S8 and 1T MoS2, indicating that the Fe7S8 / 1T MoS2 electrocatalyst was successfully prepared.

[0023] The target product Fe7S8 was characterized by scanning electron microscopy and contact angle analysis, such as Figure 2 As shown in the figure, the Fe7S8 sample has a nanosheet morphology (a). The contact angle shows that Fe7S8 has excellent hydrophilicity (b).

[0024] The target product 1T-MoS2 was characterized by scanning electron microscopy and contact angle analysis, such as Figure 3 As shown, the 1T-MoS2 sample has a nanoflower morphology ( Figure 3 a). At the same time, the contact angle shows that the hydrophilicity of 1T-MoS2 is weaker than that of Fe7S8 ( Figure 3 b).

[0025] The target product Fe7S8 / 1T MoS2 was characterized by scanning electron microscopy and contact angle analysis, such as Figure 4 As shown in the figure, the Fe7S8 / 1TMoS2 sample is a composite nanoflower morphology on the nanosheet array (a). At the same time, the contact angle shows that the 1T-MoS2 / Fe7S8 nanosheet array has better hydrophilicity (b).

[0026] Figure 5 The electrocatalytic hydrogen production property diagram of the target product of the present invention is shown in the figure. It can be seen from the figure that at a current density of 10 mA cm -2 When the target product Fe7S8 / 1T MoS2 has a low overpotential of 9 mV, its electrocatalytic properties are superior to those of Pt / C (a). After 48 hours of continuous testing, the current density remains stable (b).

[0027] Figure 6 The electrocatalytic oxygen production property diagram of the target product of the present invention is shown in the figure. It can be seen from the figure that at a current density of 10 mA cm -2 When the target product has a lower overpotential of 183 mV (a), the current density remains stable after 48 hours of continuous testing (b).

[0028] Figure 7 It is the target product of the present invention, Fe7S8 / 1T MoS2(+) || Fe7S8 / 1T MoS2(-) water splitting properties diagram. It can be seen from the figure that at a current density of 10 mAcm -2 When the overpotential of the target product is 1.41 V (a), the current density remains stable after 48 hours of continuous testing (b).

Claims

1. A method for preparing a high-efficiency electrocatalyst based on Fe7S8 / 1T MoS2 nanosheet array, characterized in that: The specific steps of this method are as follows: (1) Pretreatment of the foamed iron: using acetone and deionized water to clean and remove impurities on the surface of the foamed iron and then drying it; wherein the drying condition is preferably vacuum drying at 60°C for 6 hours; (2) Preparation of Fe7S8 / 1T MoS2 electrocatalyst: a. Add 0.8~1.2 mmol (NH4)6Mo7O to 20 mL of deionized water 24 4H2O and 11.2~16.8 mmol CH4N2S are stirred and dissolved; b. Add 0.0145-0.0155 g of L(+)-ascorbic acid to the solution and stir for 5 min. c. Transfer the mixed solution into a 25 mL autoclave, insert the treated foam iron, and heat at 200 °C for 18 h; d. After naturally cooling to room temperature, the foamed iron was taken out, washed with deionized water and anhydrous ethanol, and dried to obtain the high-efficiency electrocatalyst based on the Fe7S8 / 1T MoS2 nanosheet array.

2. The method for preparing a high-efficiency electrocatalyst based on Fe7S8 / 1T MoS2 nanosheet array according to claim 1, characterized in that: In step a, (NH4)6Mo7O 24 4H2O is 1 mmol, CH4N2S is 14 mmol.

3. The method for preparing a high-efficiency electrocatalyst based on Fe7S8 / 1T MoS2 nanosheet array according to claim 1, characterized in that: In step b, the amount of L(+)-ascorbic acid is 0.015 g.

4. The method for preparing a high-efficiency electrocatalyst based on Fe7S8 / 1T MoS2 nanosheet array according to claim 1, characterized in that: The temperature during the drying treatment in step d is 60° C., and vacuum drying is adopted for 6 hours.

5. A high-efficiency electrocatalyst based on Fe7S8 / 1T MoS2 nanosheet array prepared according to the method according to any one of claims 1 to 4.

6. Use of the high-efficiency electrocatalyst based on Fe7S8 / 1T MoS2 nanosheet array according to claim 5 coated on a cathode and / or an anode for electrolysis of water.

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