Sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst as well as preparation method and application thereof

Abstract

The invention discloses a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst and a preparation method and application thereof.The preparation method comprises the steps that firstly, nickel foam is subjected to surface modification, a NiCo LDH nanosheet array evenly distributed grows on the surface of the nickel foam, then the nickel foam is soaked in a solution containing iron ions and sodium thiosulfate, and an S-NiCoFe LDH nanosheet array is obtained; and the nickel-cobalt-based self-supporting OER electrocatalyst is prepared. The electrode material has the advantages that the three-dimensional porous self-supporting electrode does not need an organic adhesive or a supporting electrode; the raw materials are non-noble metals, low in price and wide in source. The obtained nickel-cobalt-based self-supporting electrode material shows good OER performance in 1mol / L KOH, the overpotential of the catalyst at 100mA / cm < 2 > is 283mV, and after 48h stability test, the performance of the catalyst is not obviously attenuated.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conversion material preparation, and more particularly to a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, the global energy demand has been continuously increasing. The overexploitation and use of fossil fuels have led to various problems such as energy scarcity and the greenhouse effect. There is an urgent need for alternative new energy sources for mankind. At the same time, new energy sources such as solar energy, wind energy, and tidal energy are restricted in their further development due to regional and intermittent characteristics. As the most abundant element in nature, hydrogen is not only an important role in accelerating the global transition to a low-carbon economy but also an indispensable element in a "decarbonized, sustainable energy system". The electrolytic water system converts unstable energy (such as solar energy, wind energy) into hydrogen production by electrolyzing water, and finally stores this energy in the form of hydrogen. Therefore, hydrogen production by electrolyzing water is considered the most promising and green hydrogen production route. Electrolyzing water mainly includes two important electrode reactions: the hydrogen evolution reaction at the cathode and the oxygen evolution reaction at the anode. Among them, the oxygen evolution process involves a complex four-electron reaction, with many intermediates and slow kinetics, making the reaction require a higher overpotential. Currently, the catalysts used commercially are mostly platinum-based metals and oxides of precious metals iridium and ruthenium. However, their low reserves and high costs limit their large-scale application and further development. To solve this problem, a great deal of effort has been spent exploring efficient and stable non-precious metal electrocatalysts, such as transition metal (oxy) hydroxides, oxides, nitrides, phosphides, sulfides, and selenides.

[0003] Among them, layered double hydroxides are composed of a positively charged metal hydroxide main layer and interlayer anions and water molecules overlapping with each other. Due to their diversity, adjustable composition, hydrophilicity, unique redox function, and excellent catalytic activity, they have become excellent and promising candidates for electrolytic water catalysts. Nickel-cobalt layered double hydroxide (NiCo LDH) has become one of the catalysts with research value due to its good stability and relatively high catalytic performance. However, there are still some places that need to be modified. Among them, the strong bonding interaction between nickel sites and oxygen-containing intermediates leads to poor activity, and NiCo LDH has a semiconductor-like electronic structure with poor conductivity. Summary of the Invention

[0004] In view of this, the present invention provides a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst, a preparation method thereof, and an application thereof. The S-NiCoFe LDH catalyst with a nanosheet array is prepared by an electrodeposition method and an immersion method, making the catalyst preparation process simple and the cost low. Electrochemical tests show that the obtained catalyst has a good electrolytic water effect.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A preparation method of a three-dimensional self-supporting sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst, comprising the following steps:

[0007] (1) Cut the nickel foam into sheets, ultrasonically clean them in hydrochloric acid and ethanol respectively, then rinse with deionized water and dry.

[0008] (2) Use the dried nickel foam as the working electrode, and perform constant current deposition in a mixed solution of nickel nitrate, cobalt nitrate, and ammonium chloride to modify its surface, and grow a nickel-cobalt layered double hydroxide nanosheet array (NiCo LDH / NF) on the surface.

[0009] (3) Prepare a mixed solution of ferric chloride and sodium thiosulfate, and immerse the electrode modified in step (2) in the mixed solution to obtain a sulfur-doped nickel-cobalt-iron layered double hydroxide (S-NiCoFe LDH) nanosheet array electrode.

[0010] The cation layer of LDH can be regarded as metal hydroxide. Immersing NiCo LDH in a solution containing iron ions can successfully dope iron into the cation layer. Because ferric hydroxide has the lowest solubility and tends to displace nickel and cobalt, the regulation of the cation layer of LDH is realized. The doping of iron can enhance the conductivity of NiCo LDH and effectively expose the active sites.

[0011] Adding a suitable sulfur source during the sulfidation process of LDH can successfully prepare sulfur-doped LDH, realize the sulfidation of LDH, and achieve the purpose of structural regulation. Using sodium thiosulfate as the sulfur source can realize the mild sulfidation of LDH. The sulfidation treatment can change the electronic structure of LDH and improve the intrinsic activity. By performing the above two methods simultaneously, the regulation of the cation layer and sulfidation of LDH can be achieved in one step, further improving the catalytic performance of the catalyst.

[0012] Preferably, in step (1), the concentration of the hydrochloric acid is 3 mol / L, and the ethanol is anhydrous ethanol;

[0013] The time of ultrasonic cleaning is 10 min.

[0014] Preferably, in step (2), the concentrations of nickel nitrate, cobalt nitrate, and ammonium chloride are 0.1 mol / L, 0.05 mol / L, and 0.1 mol / L respectively, and the volume is 25 mL.

[0015] Preferably, the constant current deposition in step (2) is carried out at -50 mA for 600 s.

[0016] Preferably, in step (3), the concentrations of ferric chloride and sodium thiosulfate in the mixed solution are 0.01 mol / L and 0.02 mol / L respectively, and the volume is 20 mL.

[0017] Preferably, the soaking time in step (3) is 40 min.

[0018] Preferably, the soaking temperature in step (3) is room temperature.

[0019] Another object of the present invention is to provide a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst, which is prepared by the preparation method of the sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst described above.

[0020] Another object of the present invention is to provide the application of the above-mentioned sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst in the oxygen evolution reaction.

[0021] Through the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) Three-dimensional porous self-supporting electrode, without organic binder and supporting electrode;

[0023] 2) The raw materials are non-noble metals, with low price and wide sources;

[0024] 3) The catalyst has good catalytic performance in alkaline medium, with low overpotential and good stability. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0026] Figure 1 It is the flow chart for preparing the three-dimensional self-supporting S-NiCoFe LDH nanosheet array catalyst in Example 1;

[0027] Figure 2 It is the SEM image of the three-dimensional self-supporting S-NiCoFe LDH nanosheet array catalyst obtained in Example 1;

[0028] Figure 3 It is the XRD pattern of the three-dimensional self-supporting S-NiCoFe LDH nanosheet array catalyst obtained in Example 1;

[0029] Figure 4The electrochemical performance diagram of the products obtained in Examples 1, 2, 3 and Comparative Examples 1 and 2, where Figure 4 a is the LSV curve of implementation cases 1, 2, and 3; Figure 4 b is the EIS graph of implementation cases 1, 2, and 3;

[0030] Figure 4 c, d are LSV curves of comparative examples 1 and 2; Figure 4 e is the stability test diagram of S-NiCoFe LDH / NF. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment provides a method for preparing a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst, comprising the following steps:

[0034] (1) Cut nickel foam (NF) into 1×2 cm 2 The flakes were ultrasonically cleaned in 3 mol / L hydrochloric acid and ethanol for 10 min, then rinsed with deionized water and dried in an oven;

[0035] (2) Nickel foam (NF) was used as the working electrode in 0.1 mol / L nickel nitrate (Ni(NO 3 ) 2 )、0.05mol / L cobalt nitrate (Co(NO 3 ) 2 )、0.1mol / L ammonium chloride (NH 4 Cl) mixed solution was subjected to constant current deposition for 600 s to modify the surface of the nanostructured carbon nanotubes and grow nickel-cobalt layered double hydroxide nanosheet arrays (NiCo LDH / NF) on the surface.

[0036] (3) Prepare 0.01 mol / L ferric chloride (FeCl 3 ) and 0.02 mol / L sodium thiosulfate (Na 2 S 2 O 3 ), immersing NiCo LDH / NF in the mixed solution and reacting at room temperature for 40 min to obtain sulfur-doped nickel-cobalt-iron layered double hydroxide (S-NiCoFe LDH) nanosheet array electrode;

[0037] Example 2

[0038] This example provides a method for preparing a nickel-cobalt-iron layered double hydroxide catalyst, which includes the following steps:

[0039] (1) Cut nickel foam (NF) into flakes of 1×2 cm 2 , ultrasonically clean them in 3 mol / L hydrochloric acid and ethanol for 10 min respectively, then rinse with deionized water, and place them in an oven to dry;

[0040] (2) Use nickel foam (NF) as the working electrode and perform constant current deposition for 600 s in a mixed solution of 0.1 mol / L nickel nitrate (Ni(NO 3 )) 2 , 0.05 mol / L cobalt nitrate (Co(NO 3 )) 2 , 0.1 mol / L ammonium chloride (NH 4 Cl) to perform surface modification on it, and grow a nickel-cobalt layered double hydroxide nanosheet array (NiCo LDH / NF) on the surface;

[0041] (3) Prepare a 0.01 mol / L iron chloride solution, immerse NiCo LDH / NF in the solution, and react at room temperature for 40 min to obtain a nickel-cobalt-iron layered double hydroxide (NiCoFe LDH) electrode;

[0042] Example 3

[0043] This example provides a method for preparing a sulfur-doped nickel-cobalt layered double hydroxide catalyst, which includes the following steps:

[0044] (1) Cut nickel foam (NF) into flakes of 1×2 cm 2 , ultrasonically clean them in 3 mol / L hydrochloric acid and ethanol for 10 min respectively, then rinse with deionized water, and place them in an oven to dry;

[0045] (2) Use nickel foam (NF) as the working electrode and perform constant current deposition for 600 s in a mixed solution of 0.1 mol / L nickel nitrate (Ni(NO 3 )) 2 , 0.05 mol / L cobalt nitrate (Co(NO 3 )) 2 , 0.1 mol / L ammonium chloride (NH 4 Cl) to perform surface modification on it, and grow a nickel-cobalt layered double hydroxide nanosheet array (NiCo LDH / NF) on the surface;

[0046] (3) Prepare a 0.02 mol / L sodium thiosulfate (Na 2 S2 O 3 ) solution, soak NiCo LDH / NF in the solution, react at room temperature for 40 min to obtain a sulfur-doped nickel cobalt layered double hydroxide (S-NiCo LDH) electrode;

[0047] Comparative Example 1

[0048] The difference between Comparative Example 1 and Example 1 is that in step (3), 0.02 mol / L sodium thiosulfate (Na 2 S 2 O 3 ) is replaced with 0.02 mol / L sodium sulfide (Na 2 S) and 0.02 mol / L thiourea (CH 4 N 2 S), respectively.

[0049] Comparative Example 2

[0050] The difference between Comparative Example 2 and Example 1 is that in step (3), NiCo LDH / NF is soaked in a mixed solution of 0.01 mol / L iron chloride (FeCl 3 ) and 0.02 mol / L sodium thiosulfate (Na 2 S 2 O 3 ), and the reaction time is strictly controlled to be 20 min, 30 min, and 50 min, respectively.

[0051] Figure 2 is the scanning electron microscope image of the S-NiCoFe LDH / NF electrode sample. It can be clearly seen from the SEM image that the morphology of the S-NiCoFe LDH / NF catalyst is a nanosheet array supported on the NF substrate.

[0052] Figure 3 is the XRD pattern of the S-NiCoFe LDH / NF electrode sample and the NiCo LDH / NF sample. It can be seen from the XRD that the prepared NiCo LDH has good crystallinity and no impurity phase appears. Its characteristic peaks are mainly composed of NiCo LDH (PDF#33-0429) and Ni (PDF#01-1206). After doping with iron and sulfidation, only the diffraction peak of Ni appears, which may be caused by low catalyst loading or poor crystallinity.

[0053] Figure 4 is to test the OER electrocatalytic performance of different catalysts in a three-electrode system with an electrolyte of 1 mol / L KOH. As Figure 4 shown in a, the S-NiCoFe LDH / NF electrode sample at 100 mA / cm 2The overpotential is 283 mV, showing good OER catalytic activity. Electrochemical impedance test ( Figure 4 b) The results show that S-NiCoFe LDH / NF has the smallest internal resistance, which is beneficial to reducing the polarization phenomenon of the catalyst during the catalytic process and can effectively reduce the overpotential of the catalyst during the catalytic process. From Figure 4 c, it can be seen that when the sulfur source is sodium thiosulfate, the catalyst has the best OER performance. Figure 4 d The results show that when the soaking time is 40 min, the catalytic activity of S-NiCoFe LDH / NF is the best. Long-term stability tests were carried out on the S-NiCoFe LDH / NF electrode samples ( Figure 4 e). After 48 h of stability test, the performance of the catalyst hardly decreased significantly. At 100 mA / cm 2 , the overpotential only increased by 5 mV, proving that the catalyst has excellent stability.

[0054] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0055] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst, characterized in that: The following steps are involved: (1) Cut the nickel foam into sheets, ultrasonically clean them in hydrochloric acid and ethanol, then rinse them with deionized water and dry them; (2) using the dried nickel foam as a working electrode, performing constant current deposition in a mixed solution of nickel nitrate, cobalt nitrate, and ammonium chloride to modify its surface, and growing a nickel-cobalt layered double hydroxide nanosheet array on the surface; (3) preparing a mixed solution of ferric chloride and sodium thiosulfate, and immersing the electrode modified in step (2) in the mixed solution to obtain a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array electrode.

2. The method for preparing a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst according to claim 1, characterized in that: In step (1), the concentration of hydrochloric acid is 3 mol / L, and the ethanol is anhydrous ethanol; The ultrasonic cleaning time is 10 minutes.

3. The method for preparing a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst according to claim 1, characterized in that: In step (2), the concentrations of nickel nitrate, cobalt nitrate and ammonium chloride are 0.1 mol / L, 0.05 mol / L and 0.1 mol / L respectively, and the volume is 25 mL.

4. The method for preparing a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst according to claim 1, characterized in that: The constant current deposition in step (2) is deposition at -50 mA for 600 s.

5. The method for preparing a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst according to claim 1, characterized in that: The concentrations of ferric chloride and sodium thiosulfate in the mixed solution in step (3) are 0.01 mol / L and 0.02 mol / L respectively, and the volume is 20 mL.

6. The method for preparing a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst according to claim 1, characterized in that: The soaking time in step (3) is 40 minutes.

7. The method for preparing a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst according to claim 1, characterized in that: The soaking temperature in step (3) is room temperature.

8. A sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst, characterized in that: The sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst is prepared by the preparation method of the sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst according to any one of claims 1 to 7.

9. Use of the sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst as claimed in claim 8 in oxygen evolution reaction.

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