A sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst, a preparation method and application thereof

Abstract

The application discloses a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst and a preparation method and application thereof. First, a nickel foam is subjected to surface modification, and a uniformly distributed NiCo LDH nanosheet array is grown on the surface of the nickel foam, then the nickel foam is soaked in a solution containing iron ions and sodium thiosulfate to obtain an S-NiCoFe LDH nanosheet array, and a nickel-cobalt-based self-supporting OER electrocatalyst is prepared. The electrode material has the following advantages: a three-dimensional porous self-supporting electrode is not required to have an organic binder and a supporting electrode; raw materials are non-noble metals, which are cheap and widely available. The obtained nickel-cobalt-based self-supporting electrode material exhibits good OER performance in 1 mol / L KOH, and the catalyst has a 283 mV overpotential at 100 mA / cm 2 The catalyst performance does not obviously attenuate after a 48 h stability test.

Description

Technical Field

[0001] This invention relates to the field of energy conversion material preparation technology, and more specifically to a sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst, its preparation method, and its application. Background Technology

[0002] In recent years, global energy demand has continued to grow, and the overexploitation and use of fossil fuels has led to energy scarcity and the greenhouse effect, among other problems. Humanity urgently needs alternative new energy sources. Meanwhile, the development of new energy sources such as solar, wind, and tidal power is limited by their geographical and intermittent nature. Hydrogen, as the most abundant element in nature, plays a crucial role not only in accelerating the global transition to a low-carbon economy but is also an indispensable element in a "decarbonized, sustainable energy system." Water electrolysis systems utilize unstable energy sources (solar, wind, etc.) to produce hydrogen, ultimately storing this energy as hydrogen gas. Therefore, water electrolysis is considered the most promising and green hydrogen production method. Water electrolysis mainly involves two important electrode reactions: the hydrogen evolution reaction at the cathode and the oxygen evolution reaction at the anode. The oxygen evolution process involves a complex four-electron reaction with many intermediates and slow kinetics, requiring a higher overpotential. Currently, commercially used catalysts are mostly oxides of platinum group metals and precious metals such as iridium and ruthenium, but their low reserves and high costs limit their large-scale application and further development. To address this problem, considerable effort has been devoted to exploring efficient and stable non-precious metal electrocatalysts, such as transition metal (oxy) hydroxides, oxides, nitrides, phosphides, sulfides, and selenides.

[0003] Layered double hydroxides, composed of positively charged metal hydroxide main layers and interlayered anions and water molecules, have become promising candidates for water electrolysis catalysts due to their diversity, tunable composition, hydrophilicity, unique redox function, and excellent catalytic activity. Nickel-cobalt layered double hydroxides (NiCo LDH) are among the catalysts of research value due to their good stability and high catalytic performance. However, some aspects still require modification. The strong bonding interaction between nickel sites and oxygen-containing intermediates leads to poor activity, and NiCo LDH has a semiconductor-like electronic structure, resulting in poor electrical 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, its preparation method and application. The S-NiCoFe LDH catalyst with nanosheet array was prepared by electrodeposition and immersion methods, which makes the catalyst preparation process simple and low cost. Electrochemical tests show that the obtained catalyst has good water electrolysis performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a three-dimensional self-supporting sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst includes the following steps:

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

[0008] (2) The dried nickel foam was used as the working electrode and its surface was modified by constant current deposition in a mixed solution of nickel nitrate, cobalt nitrate and ammonium chloride. A nickel-cobalt layered double hydroxide nanosheet array (NiCo LDH / NF) was grown 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 a metal hydroxide. Immersing NiCo LDH in a solution containing iron ions can successfully dope iron into the cation layer. Because iron hydroxide has the lowest solubility, it tends to displace nickel and cobalt, thereby achieving regulation of the cation layer of LDH. Iron doping can enhance the conductivity of NiCo LDH and effectively expose active sites.

[0011] By adding a suitable sulfur source during the sulfidation process of LDH, sulfur-doped LDH can be successfully prepared, achieving the goal of structural control through LDH sulfidation. Using sodium thiosulfate as a sulfur source allows for mild sulfidation of LDH. Sulfidation treatment can alter the electronic structure of LDH and improve its intrinsic activity. By simultaneously performing these two methods, the cation layer control and sulfidation of LDH can be achieved in one step, further enhancing the catalytic performance of the catalyst.

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

[0013] The ultrasonic cleaning time is 10 minutes.

[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, in step (2), the constant current deposition is performed at -50mA for 600s.

[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 minutes.

[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 above-mentioned method for preparing the sulfur-doped nickel-cobalt-iron layered double hydroxide nanosheet array catalyst.

[0020] Another objective of this 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] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) Three-dimensional porous self-supporting electrode, requiring no organic binder or supporting electrode;

[0023] 2) The raw materials are non-precious metals, which are inexpensive and widely available;

[0024] 3) This catalyst exhibits good catalytic performance in alkaline media, with low overpotential and good stability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating the preparation of a three-dimensional self-supporting S-NiCoFe LDH nanosheet array catalyst in Implementation Case 1;

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

[0028] Figure 3 The image shows the XRD pattern of the three-dimensional self-supporting S-NiCoFe LDH nanosheet array catalyst obtained in Implementation Case 1.

[0029] Figure 4Electrochemical performance diagrams of the products obtained from Examples 1, 2, and 3 and Comparative Examples 1 and 2 are shown. Figure 4 a represents the LSV curves for implementation cases 1, 2, and 3; Figure 4 b is the EIS diagram for implementation cases 1, 2, and 3;

[0030] Figure 4 c and d are the LSV curves of comparative examples 1 and 2; Figure 4 e represents the stability test result of S-NiCoFe LDH / NF. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort 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, including the following steps:

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

[0035] (2) Using nickel foam (NF) as the working electrode, surface modification was carried out by constant current deposition for 600s in a mixed solution of 0.1 mol / L nickel nitrate (Ni(NO3)2), 0.05 mol / L cobalt nitrate (Co(NO3)2), and 0.1 mol / L ammonium chloride (NH4Cl), and nickel-cobalt layered double hydroxide nanosheet array (NiCo LDH / NF) was grown on the surface.

[0036] (3) Prepare a mixed solution of 0.01 mol / L ferric chloride (FeCl3) and 0.02 mol / L sodium thiosulfate (Na2S2O3), immerse NiCo LDH / NF in the mixed solution, and react 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 embodiment provides a method for preparing a nickel-cobalt-iron layered double hydroxide catalyst, including the following steps:

[0039] (1) Cut the nickel foam (NF) into 1×2cm pieces. 2 The flakes were ultrasonically cleaned in 3 mol / L hydrochloric acid and ethanol for 10 min respectively, then rinsed with deionized water and dried in an oven.

[0040] (2) Using nickel foam (NF) as the working electrode, surface modification was carried out by constant current deposition for 600s in a mixed solution of 0.1 mol / L nickel nitrate (Ni(NO3)2), 0.05 mol / L cobalt nitrate (Co(NO3)2), and 0.1 mol / L ammonium chloride (NH4Cl), and nickel-cobalt layered double hydroxide nanosheet array (NiCo LDH / NF) was grown on the surface.

[0041] (3) Prepare a 0.01 mol / L ferric 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 embodiment provides a method for preparing a sulfur-doped nickel-cobalt layered double hydroxide catalyst, comprising the following steps:

[0044] (1) Cut the nickel foam (NF) into 1×2cm pieces. 2 The flakes were ultrasonically cleaned in 3 mol / L hydrochloric acid and ethanol for 10 min respectively, then rinsed with deionized water and dried in an oven.

[0045] (2) Using nickel foam (NF) as the working electrode, surface modification was carried out by constant current deposition for 600s in a mixed solution of 0.1 mol / L nickel nitrate (Ni(NO3)2), 0.05 mol / L cobalt nitrate (Co(NO3)2), and 0.1 mol / L ammonium chloride (NH4Cl), and nickel-cobalt layered double hydroxide nanosheet array (NiCo LDH / NF) was grown on the surface.

[0046] (3) Prepare a 0.02 mol / L sodium thiosulfate (Na2S2O3) solution, immerse NiCo LDH / NF in the solution, and 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 (Na2S2O3) is replaced with 0.02 mol / L sodium sulfide (Na2S) and 0.02 mol / L thiourea (CH4N2S), respectively.

[0049] Comparative Example 2

[0050] The difference between Comparative Example 2 and Example 1 is that in step (3), NiCo LDH / NF was soaked in a mixed solution of 0.01 mol / L ferric chloride (FeCl3) and 0.02 mol / L sodium thiosulfate (Na2S2O3), and the reaction time was strictly controlled to be 20 min, 30 min and 50 min respectively.

[0051] Figure 2 This is a scanning electron microscope (SEM) image of the S-NiCoFe LDH / NF electrode sample. The SEM images clearly show that the S-NiCoFe LDH / NF catalyst consists of a nanosheet array supported on an NF substrate.

[0052] Figure 3 The XRD patterns of the S-NiCoFe LDH / NF electrode sample and the NiCo LDH / NF sample are shown. The XRD patterns reveal that the prepared NiCo LDH catalyst exhibits good crystallinity and no impurity phases. Its characteristic peaks are mainly composed of NiCo LDH (PDF#33-0429) and Ni (PDF#01-1206). After iron doping and sulfidation, only Ni diffraction peaks appeared, possibly due to low catalyst loading or poor crystallinity.

[0053] Figure 4 To test the OER electrocatalytic performance of different catalysts in a three-electrode system with 1 mol / L KOH electrolyte. Figure 4 As shown in figure a, the S-NiCoFe LDH / NF electrode sample at 100 mA / cm 2 The overpotential was 283 mV, exhibiting good OER catalytic activity. Electrochemical impedance spectroscopy (EIS) Figure 4 b) The results show that S-NiCoFe LDH / NF has the lowest internal resistance, which is beneficial for reducing the polarization phenomenon of the catalyst during the catalytic process and can effectively reduce the overpotential of the catalyst during the catalytic process. Figure 4 c shows that when the sulfur source is sodium thiosulfate, the catalyst has the best OER performance. Figure 4 The results showed that the S-NiCoFe LDH / NF catalytic activity was optimal when the soaking time was 40 min. Long-term stability tests were conducted on the S-NiCoFe LDH / NF electrode samples. Figure 4 e) After a 48-hour stability test, the catalyst performance showed almost no significant degradation at 100 mA / cm². 2 At that time, the overpotential increased by only 5mV, proving that the catalyst has excellent stability.

[0054] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0055] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to 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, Includes the following steps: (1) Cut the nickel foam into sheets, and ultrasonically clean them in hydrochloric acid and ethanol respectively, then rinse them with deionized water and dry them; (2) The dried nickel foam was used as the working electrode and its surface was modified by constant current deposition in a mixed solution of nickel nitrate, cobalt nitrate and ammonium chloride. A nickel-cobalt layered double hydroxide nanosheet array was grown on the surface. (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 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, In step (2), the constant current deposition is performed at -50mA for 600s.

5. 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 (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.

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 method described in any one of claims 1-7.

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

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