A Ni(OH)2 / MoS2 heterostructure electrocatalyst and its preparation method and application

Abstract

The present invention belongs to the technical field of catalysts for alkaline water electrolysis, and discloses a Ni(OH)2 / MoS2 heterostructure electrocatalyst, a preparation method thereof, and an application thereof. The microstructure of the electrocatalyst is a twisted heterostructure, wherein treated nickel foam is placed in deionized water, two-dimensional Ni(OH)2 nanosheets are in situ grown on the nickel foam, Ni(OH)2-NF is clamped by platinum electrodes as a working electrode, a carbon rod is used as a counter electrode, and an AgCl electrode is used as a reference electrode, and the NF-Ni(OH)2 is immersed in 10-20 mmol / L of thiourea and 37.5-60 mmol / L of (NH4)6Mo7O 24 MoS2 was produced by electrodeposition growth on Ni(OH)2-NF using a constant voltage method in a three-electrode system in an electrolyte containing 0.06 mol / L sodium citrate. This electrocatalyst exhibits dual hydrogen and oxygen evolution functions and can be applied in alkaline water electrolysis.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts for alkaline water electrolysis, and more specifically, relates to a Ni(OH)2 / MoS2 heterostructured electrocatalyst and its preparation method and application. Background Art

[0002] Due to the increasing depletion of fossil fuels and people's growing concern about environmental issues, finding sustainable clean energy to replace fossil fuels has become an urgent task. Hydrogen has the advantages of being green and clean (carbon-free) and having high energy density, so it is believed to help deal with the energy and environmental problems caused by the long-term and large-scale use of fossil fuels. The electrolysis of water to produce hydrogen in an alkaline electrolyzer is currently a widespread means of industrial hydrogen production. Generally speaking, the entire water splitting consists of two half reactions: the anodic oxygen evolution reaction (OER) and the cathode hydrogen evolution reaction (HER). However, these two half reactions are slow continuous multiple electron transfer processes that need to overcome huge reaction energy barriers, resulting in slow electrode reaction kinetics of the water electrolysis reaction. Therefore, it is necessary to develop highly active catalysts to reduce the overpotential required for the reaction and promote its reaction.

[0003] Currently, widely used electrocatalysts for OER, such as IrO2 and RuO2, and for HER, such as Pt / C and Raney nickel, suffer from safety and poor stability (Raney nickel), scarcity, and high cost (IrO2, RuO2, Pt / C). These drawbacks severely hinder their large-scale application. To maximize the utilization of inexpensive transition metals to replace precious metals without compromising catalytic activity, the rational design and controllable preparation of transition metal catalysts based on a deep understanding of reaction mechanisms and structural relationships are crucial. Transition metal nickel-based electrocatalysts have attracted considerable attention due to their high catalytic activity, high conductivity, and low cost, and hold great promise for replacing precious metal electrocatalysts. Over the past decade, researchers have extensively developed nickel-based electrocatalysts to enhance their intrinsic catalytic activity and increase their number of active sites, including through surface-based structural design, heteroatom doping, crystal defect engineering, and alloying with other metals. However, the harsh preparation conditions of these catalysts hinder their industrial application. Therefore, the development of nickel-based hydrogen and oxygen evolution electrocatalysts with low cost, simple preparation processes, and high catalytic activity is urgently needed.

[0004] Ordinary nickel foil or nickel foam rarely exhibits good electrocatalytic oxygen and hydrogen evolution activity in alkaline electrolytic cells. To enhance the catalytic activity of nickel metal, it is often modified by doping to prepare nickel-based metal oxides, nickel-based alloys, and nickel-based heterostructures as catalytic materials. The main preparation methods include hydrothermal, vapor deposition, and thermal reduction. However, these methods generally require high temperatures and high pressures, creating demanding conditions that are unsuitable for large-scale industrial production. Summary of the Invention

[0005] In order to solve the above-mentioned deficiencies and shortcomings of the prior art, the primary purpose of the present invention is to provide a Ni(OH)2 / MoS2 heterostructured electrocatalyst.

[0006] Another object of the present invention is to provide a method for preparing the Ni(OH)2 / MoS2 heterostructure electrocatalyst. The method uses a room temperature etching method and an electrodeposition method to prepare the Ni(OH)2 / MoS2 heterostructure electrocatalyst.

[0007] Another object of the present invention is to provide an application of the above-mentioned Ni(OH)2 / MoS2 heterostructured electrocatalyst.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A Ni(OH)2 / MoS2 heterostructure electrocatalyst, wherein the microstructure of the Ni(OH)2 / MoS2 heterostructure electrocatalyst is a twisted heterostructure. The treated nickel foam is placed in deionized water for 24 to 48 hours, and two-dimensional Ni(OH)2 nanosheets are in situ grown on the nickel foam, which are recorded as Ni(OH)2-NF. The Ni(OH)2-NF is clamped by a platinum electrode as a working electrode, a carbon rod is used as a counter electrode, and an AgCl electrode is used as a reference electrode. The working electrode NF-Ni(OH)2 is immersed in an electrolyte, wherein the electrolyte is prepared by deionizing water with 10 to 20 mmol / L of thiourea and 37.5 to 60 mmol / L of (NH4)6Mo7O 24 , then add 0.06 mol / L sodium citrate, and use the constant voltage method in a three-electrode system at 50-60 ° C and a voltage of -0.9 to -1.5 V to electrodeposit two-dimensional MoS2 on Ni(OH)2-NF to obtain it.

[0010] Preferably, the thickness of the nickel foam is 0.5-1.5 mm, the pore size is 90-110 ppi, and the area is (1-2)×(1-3) cm 2 .

[0011] The preparation method of the Ni(OH)2 / MoS2 heterostructure electrocatalyst comprises the following specific steps:

[0012] S1. Using nickel foam as a catalyst support, ultrasonically cleaning the nickel foam with acetone to remove organic contaminants, soaking the treated nickel foam in nitric acid to remove the surface oxide film, and etching the surface of the nickel foam, and finally rinsing with deionized water and anhydrous ethanol, and drying at 50 to 70 ° C to obtain a treated nickel foam;

[0013] S2. The treated nickel foam was placed in deionized water for 24 to 48 hours to in situ grow two-dimensional Ni(OH)2 nanosheets on the nickel foam, denoted as Ni(OH)2-NF;

[0014] S3. Use platinum electrode to clamp Ni(OH)2-NF as working electrode, carbon rod as counter electrode, AgCl electrode as reference electrode, immerse the working electrode Ni(OH)2-NF in electrolyte, and adopt constant voltage method in three-electrode system. At 50-60℃ and voltage of -0.9-1.5V, two-dimensional MoS2 is electrodeposited on Ni(OH)2-NF to obtain Ni(OH)2 / MoS2 heterostructure electrocatalyst on nickel foam.

[0015] Preferably, the concentration of nitric acid in step S1 is 0.05-0.15 mol / L.

[0016] Preferably, in step S1, the drying time is 6 to 12 hours, the cleaning time is 20 to 60 minutes, and the soaking time is 10 to 30 minutes.

[0017] Preferably, the pH of the electrolyte in step S3 is 8 to 9; and the electrodeposition time is 50 to 200 seconds.

[0018] The application of the Ni(OH)2 / MoS2 heterostructure electrocatalyst in the field of alkaline water electrolysis.

[0019] The present invention utilizes an etching method to corrode nickel foam at room temperature, and grows a nickel hydroxide lamellar structure on the surface of the nickel foam, abbreviated as Ni(OH)2-NF, where Ni+2H2O+O2=Ni(OH)2. Molybdenum disulfide is then grown on the Ni(OH)2-NF by electrodeposition. This unique heterostructured composite material not only inherits the inherent properties of the two components, but also benefits from the synergistic effect associated with the heterogeneous interface, resulting in a strong interaction between the MoS2 and Ni(OH)2 flakes, promoting charge transfer between them. In addition, a large number of sulfur vacancies appear in the MoS2 flakes, thereby ensuring the exposure of the reaction active sites of the two-dimensional nanosheets. Through the above method, a Ni(OH)2 / MoS2 heterostructured bifunctional electrocatalyst for hydrogen and oxygen evolution is efficiently and economically prepared, which can be used for full hydrolysis, solving the problems of insufficient catalytic activity and harsh preparation conditions of nickel-based electrocatalysts.

[0020] Compared with the existing technology, the above technical solution has the following beneficial effects:

[0021] 1. The present invention adopts room temperature etching and electrodeposition method to prepare Ni(OH)2 / MoS2 heterostructure electrocatalyst, which has the advantages of being simple, fast and efficient compared with hydrothermal method, chemical vapor deposition method and thermal reduction method.

[0022] 2. In the present invention, nickel hydroxide nanosheets and molybdenum disulfide sheets are intertwined to prepare Ni(OH)2 / MoS2 with a twisted heterostructure. This structure provides a significant synergistic coupling effect, which can promote electron transfer, help reduce the energy barrier required to overcome the rate-determining step of the reaction, and at the same time expose a large number of catalytic reaction active sites, effectively improving its hydrogen evolution (HER) / oxygen evolution (OER) catalytic performance;

[0023] 3. The present invention prepares a bifunctional electrocatalyst that can be used for both hydrogen and oxygen evolution, avoiding the tedious steps of preparing two catalysts separately. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 SEM and EDS images of Ni(OH)2 / MoS2 of Example 1;

[0025] Figure 2 SEM and EDS photos of Ni(OH)2 / MoS2 of Example 2;

[0026] Figure 3 SEM photos of different tissues grown on nickel foam in Examples 1-2 and Comparative Example 1;

[0027] Figure 4 HER polarization curves of nickel foam (NF), Ni(OH)2-NF of comparative example 1, Ni(OH)2 / MoS2(1) of example 1, and Ni(OH)2 / MoS2(2) of example 2 in 1 mol / L KOH, respectively.

[0028] Figure 5 HER Tafel curves of Ni(OH)2-NF of Comparative Example 1, Ni(OH)2 / MoS2(1) of Example 1, and Ni(OH)2 / MoS2(2) of Example 1 in 1 mol / L KOH, respectively;

[0029] Figure 6 OER polarization curves of NF, Ni(OH)2-NF of comparative example 1, Ni(OH)2 / MoS2(1) of example 1, and Ni(OH)2 / MoS2(2) of example 2 in 1 mol / L KOH, respectively.

[0030] Figure 7 OER Tafel curves of NF, Ni(OH)2-NF of comparative example 1, Ni(OH)2 / MoS2(1) of example 1, and Ni(OH)2 / MoS2(2) of example 2 in 1 mol / L KOH, respectively. DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments described herein are only used to illustrate and explain the present invention and should not be understood as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Example 1

[0033] 1. Use nickel foam (NF, with a thickness of 1 mm and a pore size of 110 ppi) as the catalyst carrier and use acetone to 2 The nickel foam was ultrasonically cleaned for 30 minutes to remove organic contaminants. The treated nickel foam was then immersed in 0.1 mol / L nitric acid to remove the surface oxide film and slightly etched for 30 minutes. Finally, it was rinsed with deionized water and anhydrous ethanol and dried in an oven at 60°C for 6 hours.

[0034] 2. The treated nickel foam was placed in deionized water for 48 hours to in situ grow two-dimensional nickel hydroxide nanosheets, abbreviated as Ni(OH)2-NF, on the nickel foam;

[0035] 3. Prepare 10mmol / L thiourea and 37.5mmol / L (NH4)6Mo7O with deionized water. 24 , 0.06 mol / L sodium citrate solution was used as the electrolyte, and the pH of the electrolyte was 9.

[0036] 4. Use the platinum electrode clip to cut into 1×1.5cm 2 The Ni(OH)2-NF was clamped as the working electrode, the carbon rod was the counter electrode, and the AgCl electrode was the reference electrode. The working electrode Ni(OH)2-NF was immersed in the electrolyte to form a three-electrode system. The constant potential method was used at a temperature of 60°C and a voltage of -0.9V (vs AgCl) for 50 seconds to electroplating grow two-dimensional MoS2 on the Ni(OH)2-NF, that is, Ni(OH)2 / MoS2 (1) was prepared on nickel foam.

[0037] Figure 1 The SEM and EDS images of Ni(OH)2 / MoS2 of Example 1 are shown. (a)-(d) are the SEM images of the local area of ​​Ni(OH)2 / MoS2, the corresponding molybdenum (Mo) element distribution, sulfur (S) element distribution, and nickel (Ni) element distribution, respectively. Figure 1 It can be seen that the sulfur, molybdenum and nickel elements are evenly distributed, but due to the low electrodeposition voltage and short deposition time, the amount of molybdenum disulfide generated is small, the molybdenum disulfide layer is not evenly combined with the nickel hydroxide, and the sulfur and molybdenum elements are less distributed in some areas.

[0038] Example 2

[0039] 1. Use nickel foam (NF, with a thickness of 1 mm and a pore size of 110 ppi) as the catalyst carrier. 2 The nickel foam was ultrasonically cleaned for 30 minutes to remove organic contaminants. The treated nickel foam was then immersed in 0.1 mol / L nitric acid to remove the surface oxide film and slightly etch the surface for 30 minutes. Finally, it was rinsed with deionized water and anhydrous ethanol and dried in an oven at 60°C for 6 hours.

[0040] 2. The treated nickel foam was placed in deionized water for 48 hours to in situ grow two-dimensional nickel hydroxide nanosheets on the nickel foam.

[0041] 3. Prepare 10mmol / L thiourea and 37.5mmol / L (NH4)6Mo7O with deionized water. 24 , 0.06 mol / L sodium citrate solution was used as the electrolyte, and the pH of the electrolyte was 9.

[0042] 4. Use platinum electrode clip to clamp and cut into 1×1.5cm 2 Ni(OH)2-NF was used as the working electrode, the carbon rod was used as the counter electrode, and the AgCl electrode was used as the reference electrode. The working electrode Ni(OH)2-NF was immersed in the electrolyte to form a three-electrode system. The constant potential method was used at a temperature of 60°C and a voltage of -1.2V (vs AgCl) for 150 seconds to electrodeposit two-dimensional MoS2 on the Ni(OH)2-NF, that is, Ni(OH)2 / MoS2(2) was prepared on nickel foam.

[0043] Figure 2 The SEM and EDS photos of Ni(OH)2 / MoS2 of Example 2. Among them, (a)-(d) are SEM photos of local areas, corresponding Mo element distribution, corresponding S element distribution, and corresponding Ni element distribution. Figure 2 It can be seen that sulfur, molybdenum and nickel elements are evenly distributed in the nanosheets, and the molybdenum disulfide layers are evenly combined with nickel hydroxide.

[0044] Comparative Example 1

[0045] 1. Use nickel foam (NF, with a thickness of 1 mm and a pore size of 110 ppi) as the catalyst carrier. 2The nickel foam was ultrasonically cleaned for 30 minutes to remove organic contaminants. The treated nickel foam was then immersed in 0.1 mol / L nitric acid to remove the surface oxide film and slightly etch the surface for 30 minutes. Finally, it was rinsed with deionized water and anhydrous ethanol and dried in an oven at 60°C for 6 hours.

[0046] 2. The treated nickel foam was placed in deionized water for 48 hours. It can be seen that the nickel foam changed from the original bright silver to dark silver, which means that two-dimensional nickel hydroxide nanosheets, abbreviated as Ni(OH)2-NF, were in situ grown on the nickel foam.

[0047] Figure 3 The following are SEM photos of different tissues grown on nickel foam in Example 1-2 and Comparative Example 1. Among them, (a) is nickel foam (NF), (b) is two-dimensional nickel hydroxide nanosheets (Ni(OH)2-NF) grown in situ on nickel foam, (c) is Ni(OH)2 / MoS2(2) in Example 2, and (d) is Ni(OH)2 / MoS2(1) in Example 1. Figure 3 As can be seen in (b), nickel hydroxide grows vertically on the smooth, bare nickel foam and has a typical layered structure. Figure 3 As can be seen in (c) and (d), the lamellar nickel hydroxide and molybdenum disulfide are entangled with each other to form a twisted heterostructure.

[0048] The electrochemical properties were characterized using a three-electrode system, with the nickel-based catalyst prepared above as the working electrode, a carbon rod as the auxiliary electrode, a mercury oxide electrode as the reference electrode, and a 1 mol / L KOH solution as the electrolyte. Before evaluating the HER and OER performance, all catalysts were activated to a stable state by cyclic voltammetry (CV) scanning at a scan rate of 50 mV / s and linear sweep voltammetry (LSV) at a scan rate of 5 mV / s. IR compensation was not performed in all electrochemical tests.

[0049] Figure 4 HER polarization curves of NF, Ni(OH)2-NF of comparative example 1, Ni(OH)2 / MoS2(1) of example 1, and Ni(OH)2 / MoS2(2) of example 2 in 1 mol / L KOH, respectively. Figure 4 It can be seen that compared with nickel foam, the HER activity of Ni(OH)2-NF is significantly improved, and the HER activity of Ni(OH)2 / MoS2 is further improved after electrodeposition growth of MoS2. The HER performance of Ni(OH)2 / MoS2(2) in Example 2 is the best, and the overpotential is the lowest among all samples. At a current density of 10 mA / cm 2When the overpotentials of Ni(OH)2 / MoS2(2) of Example 2, Ni(OH)2 / MoS2(1) of Example 1, and Ni(OH)2-NF and NF of Comparative Example 1 are 52mV, 167mV, 279mV, and 245mV, respectively. 2 At the same current density, the overpotentials of Ni(OH)2 / MoS2(2) of Example 2, Ni(OH)2 / MoS2(1) of Example 1, Ni(OH)2-NF and NF of Comparative Example 1 were 230mV, 430mV, 482mV and 527mV respectively. These results are consistent with Figure 5 The Tafel curve shows the same behavior. Figure 5 The HER Tafel curves of Ni(OH)2-NF of comparative example 1, Ni(OH)2 / MoS2(1) of example 1, and Ni(OH)2 / MoS2(2) of example 2 in 1 mol / L KOH are shown. Figure 5 It can be seen that the Tafel slopes corresponding to Ni(OH)2 / MoS2(2) of Example 2, Ni(OH)2 / MoS2(1) of Example 1, and Ni(OH)2-NF of Comparative Example 1 are 43 mV / dec, 72 mV / dec, and 101 mV / dec, respectively. Ni(OH)2 / MoS2(2) of Example 2 has the lowest Tafel slope, which means that it exhibits the fastest HER kinetics. Figure 6 The OER polarization curves of NF, Ni(OH)2-NF of comparative example 1, Ni(OH)2 / MoS2(1) of example 1, and Ni(OH)2 / MoS2(2) of example 2 in 1 mol / L KOH are shown in Table 1. Figure 6 It can be seen that at a current density of 10 mA / cm 2 When the overpotential of Ni(OH)2 / MoS2(2), Ni(OH)2 / MoS2(1), Ni(OH)2-NF, NF is 83mV, 93mV, 134mV, 364mV respectively. 2 Under the current density, the overpotentials of Ni(OH)2 / MoS2(2) of Example 2, Ni(OH)2 / MoS2(1) of Example 1, and Ni(OH)2-NF and NF of Comparative Example 1 are 280mV, 354mV, 446mV, and 650mV, respectively. Figure 7 OER Tafel curves of NF, Ni(OH)2-NF of comparative example 1, Ni(OH)2 / MoS2(1) of example 1, and Ni(OH)2 / MoS2(2) of example 2 in 1 mol / L KOH, respectively. Figure 7It can be seen that the Tafel slopes corresponding to Ni(OH)2 / MoS2(2) of Example 2, Ni(OH)2 / MoS2(1) of Example 1, Ni(OH)2-NF and NF of Comparative Example 1 are 46mV / dec, 62mV / dec, 89mV / dec and 101mV / dec, respectively. Ni(OH)2 / MoS2(2) of Example 2 has the lowest Tafel slope, which means that it exhibits the fastest OER kinetics.

[0050] Considering the HER and OER performances, the introduction of MoS2 and Ni(OH)2 to form a heterostructure can effectively improve the reaction kinetics of water electrolysis of nickel-based catalysts. The bifunctional water electrolysis performance of Ni(OH)2 / MoS2 in Example 2 is comparable to that of nickel-based catalysts recently reported in the literature, showing excellent industrial application prospects.

[0051] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A Ni(OH)2 / MoS2 heterostructure electrocatalyst, characterized in that The microstructure of the Ni(OH)2 / MoS2 heterostructure electrocatalyst is a twisted heterostructure. The preparation method of the electrocatalyst is as follows: using nickel foam as a catalyst carrier, ultrasonically cleaning the nickel foam with acetone to remove organic pollutants, immersing the treated nickel foam in nitric acid to remove the surface oxide film, and corroding the surface of the nickel foam, finally rinsing with deionized water and anhydrous ethanol, and drying at 50-70°C to obtain a treated nickel foam; placing the treated nickel foam in deionized water for 24-48 hours, and in situ growing two-dimensional Ni(OH)2 nanosheets on the nickel foam, recorded as Ni(OH)2-NF; using a platinum electrode to clamp the Ni(OH)2-NF as a working electrode, a carbon rod as a counter electrode, and an AgCl electrode as a reference electrode, and immersing the working electrode NF-Ni(OH)2 in an electrolyte, wherein the electrolyte is prepared with deionized water to contain 10-20 mmol / L thiourea, 37.5-60 mmol / L (NH4)6Mo7O 24 , then add 0.06 mol / L sodium citrate, and use the constant voltage method in a three-electrode system at 50~60℃ and a voltage of -0.9~-1.5V to grow two-dimensional MoS2 by electrodeposition on Ni(OH)2-NF for 50~200 seconds.

2. The Ni(OH)2 / MoS2 heterostructure electrocatalyst according to claim 1, characterized in that The thickness of the nickel foam is 0.5-1.5 mm, the pore size is 90-110 ppi, and the area is (1-2) × (1-3) cm 2 .

3. The method for preparing the Ni(OH)2 / MoS2 heterostructure electrocatalyst according to claim 1 or 2, characterized in that: The specific steps include: S1. Using nickel foam as a catalyst support, the nickel foam was ultrasonically cleaned with acetone to remove organic contaminants. The treated nickel foam was then immersed in nitric acid to remove the surface oxide film and etched. Finally, the nickel foam was rinsed with deionized water and anhydrous ethanol and dried at 50-70°C to obtain the treated nickel foam. S2. The treated nickel foam was placed in deionized water for 24–48 h to in situ grow two-dimensional Ni(OH)2 nanosheets on the nickel foam, designated as Ni(OH)2-NF. S3. A platinum electrode was used to clamp the Ni(OH)2-NF as the working electrode, a carbon rod as the counter electrode, and an AgCl electrode as the reference electrode. The working electrode Ni(OH)2-NF was immersed in an electrolyte containing 10-20 mmol / L thiourea and 37.5-60 mmol / L (NH4)6Mo7O in deionized water. 24 , then add 0.06 mol / L sodium citrate, and use the constant voltage method in a three-electrode system. At 50~60℃ and a voltage of -0.9~-1.5V, two-dimensional MoS2 is electrodeposited on Ni(OH)2-NF for 50~200 seconds to grow, thus obtaining a Ni(OH)2 / MoS2 heterostructure electrocatalyst on nickel foam.

4. The method for preparing the Ni(OH)2 / MoS2 heterostructure electrocatalyst according to claim 3, characterized in that: The concentration of nitric acid in step S1 is 0.05-0.15 mol / L.

5. The method for preparing the Ni(OH)2 / MoS2 heterostructure electrocatalyst according to claim 3, characterized in that: In step S1, the drying time is 6 to 12 hours, the cleaning time is 20 to 60 minutes, and the soaking time is 10 to 30 minutes.

6. The method for preparing the Ni(OH)2 / MoS2 heterostructure electrocatalyst according to claim 3, characterized in that: The pH of the electrolyte in step S3 is 8-9.

7. Application of the Ni(OH)2 / MoS2 heterostructure electrocatalyst according to claim 1 or 2 in the field of alkaline water electrolysis.

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