Synthesis method of oxygen-rich vacancy ruthenium / nickel molybdate material and application thereof in hydrogen evolution reaction in seawater

Abstract

The application discloses a method for preparing a material capable of electrolyzing seawater under a large current density and having high performance and excellent long-term stability by taking NiMoO4 nanorods as a precursor. 4‑x An oxygen vacancy-rich ruthenium / nickel molybdate material (Ru / NiMoO 4‑x ) is prepared, oxygen vacancies are introduced into the NiMoO4 by reduction of sodium borohydride, and the existence of the vacancies significantly improves the activity and stability of the catalyst. In a 1 M KOH seawater solution, a low overpotential of 206 mV is required to reach a current density of 3.0 A cm ‑2 , a Tafel slope of 28.8 mV dec ‑1 , and the catalyst can stably perform an HER process under a current density of 1.5 A cm ‑2 for 110 hours. Meanwhile, an electrolytic cell assembled by using the catalyst as a cathode can drive an electrolysis seawater process under a cell voltage of 2.11 V and a current density of 3.0 A cm ‑2 , and can stably work under a current density of 1.5 A cm ‑2 for more than 10 hours. The material has high activity and excellent stability in electrolysis of seawater under a large current density.

Description

Technical Field

[0001] This invention belongs to the field of vacancy engineering materials, and particularly relates to a method for preparing ruthenium / nickel molybdate materials and their application in the hydrogen evolution reaction in seawater. Background Technology

[0002] Hydrogen, due to its high energy density and environmentally friendly characteristics, is considered the most likely energy carrier to replace fossil resources. Water electrolysis is an effective method for producing hydrogen, and it also provides a favorable pathway for converting electrical energy into chemical energy. Since seawater reserves are much larger than freshwater reserves in nature, seawater has become a suitable substitute for water electrolysis, while also alleviating freshwater shortages. The hydrogen evolution reaction (HER), as a half-reaction in seawater electrolysis, has a significant impact on the rate of the electrolysis process. However, the large amounts of chloride ions, microorganisms, silt, and other impurities present in seawater can poison the catalyst and significantly increase the cathode reaction potential, thus deactivating the catalyst. Therefore, current research poses greater challenges to the activity and stability of seawater electrolysis catalysts.

[0003] Introducing vacancies into catalysts through vacancy engineering can significantly improve their catalytic performance because the presence of vacancies can enhance electron transport rates and optimize electronic structure. Materials rich in oxygen vacancies have been shown to promote charge transfer between catalyst phase interfaces, optimize the adsorption and desorption processes of reactive intermediates, and thus modulate and enhance the HER performance of the catalyst. Summary of the Invention

[0004] 1. The purpose of this invention is to provide a method for synthesizing oxygen-vacancy-rich ruthenium / nickel molybdate materials. Extremely low Ru content is incorporated into NiMoO4 rich in O vacancies. Through vacancy engineering strategies, the problems of low catalyst activity and poor durability in the HER half-reaction of seawater electrolysis are solved. The resulting Ru / NiMoO4 material... 4-x The alkaline electrolyzer with cathode exhibits excellent performance in high current density electrolysis of seawater.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] The preparation method of the oxygen-enriched vacancy ruthenium / nickel molybdate electrocatalyst provided by this invention can be achieved through the following preparation route:

[0007] (1) Treatment of nickel foam substrate: Cut the nickel foam substrate into appropriate size, and then immerse it in dilute hydrochloric acid (1.0 M), deionized water and ethanol in sequence. After ultrasonic cleaning, dry it overnight in a vacuum drying oven.

[0008] (2) Preparation of NiMoO4 nanowires: Ni(NO3)2·6H2O and Na2MoO4·2H2O were dissolved in deionized water and stirred for 5-10 minutes. The mixture was then transferred to a stainless steel autoclave lined with polytetrafluoroethylene. A clean piece of nickel foam was then immersed in the solution, sealed in the autoclave, and heated at 160-180°C. o Heating at C for 5-10 hours, the prepared sample is removed and washed with deionized water to obtain NiMoO4 nanowires.

[0009] (3) NiMoO 4-x Preparation of nanowires: Previously synthesized NiMoO4 nanowires were immersed in NaBH4 solution at room temperature for 10–30 minutes. The samples were then washed with deionized water and heated to 60–80 °C. o Drying at C overnight to prepare NiMoO 4-x Nanowires.

[0010] (4) Ru / NiMoO 4-x Preparation of nanospheres: NiMoO 4-x The nanowires were uniformly dispersed in an acidic solution containing RuCl3 for 4–6 hours. Finally, the sample was washed with deionized water and heated to 60–80 °C. o Drying at C overnight to prepare Ru / NiMoO 4-x Nanospheres.

[0011] (5) Preparation of Ru / NiMoO4 nanospheres: NiMoO4 nanowires were uniformly dispersed in an acidic solution containing RuCl3 for 4-6 hours. Finally, the sample was washed with deionized water and heated to 60-80 °C. o Ru / NiMoO4 nanospheres were prepared by drying at C overnight.

[0012] According to the preparation method of the technical route, the feature is that: in step (1), the nickel foam is cut into 2 cm * 3 cm pieces, and the temperature of the vacuum drying oven is set to 50~80°C. o C, to remove organic matter and oxides from the surface of the nickel foam.

[0013] According to the preparation method of the technical route, the characteristic is that the amount of Ni(NO3)2 6H2O and Na2MoO42H2O used in step (2) is 0.1~0.3g, so as to synthesize NiMoO4 nanowire precursor with uniform morphology.

[0014] According to the preparation method of the technical route, the characteristic is that the concentration of the NaBH4 solution prepared in step (3) is 0.1~1 M.

[0015] According to the preparation method of the technical route, the characteristic is that the acidic solution of RuCl3 used in step (4) is 0.01~0.1 M.

[0016] According to the preparation method of the technical route, the characteristic is that the concentration of sodium borohydride in step (5) is 0.1~2.5 M.

[0017] This invention also provides the application of an alkaline seawater electrolyzer based on an oxygen-rich vacancy ruthenium / nickel molybdate electrocatalyst as the cathode.

[0018] As a further feature of this invention, the oxygen-vacancy-enriched ruthenium / nickel molybdate catalyst constructed in this invention addresses a key challenge in preparing electrocatalysts for HER (hermetic ion exchange) seawater electrolysis at high current densities. We demonstrate that the introduction of oxygen vacancies significantly improves the catalyst's activity and long-term catalytic stability at high current densities, thereby reducing the voltage during electrolysis and achieving energy savings. The material obtained in this invention has low preparation cost, good performance, and broad application prospects in the field of seawater electrolysis. Detailed Implementation

[0019] Example 1

[0020] This invention relates to a method for preparing oxygen-vacancy-rich ruthenium / nickel molybdate (Ru / NiMoO). 4-x The method includes the following steps:

[0021] (1) Commercially available nickel foam, Ni(NO3)2·6H2O and Na2MoO4·2H2O were selected as raw materials. The three were added to 30 mL of water to dissolve them. Then the mixture solution was transferred to a 50 mL stainless steel autoclave and heated at 160 °C. o The scanning electron microscope (SEM) results of the material after heating at C for 6 hours are shown in the figure. Figure 1 This proves that the material has a nanowire morphology.

[0022] (2) After the reaction was completed, the sample obtained in (1) was immersed in 0.5 M NaBH4 solution for 30 minutes at room temperature, and then dried in an oven. The scanning electron microscope (SEM) results of the material are shown in the figure. Figure 2 This proves that the material has a nanowire morphology.

[0023] (3) Then, take an appropriate amount of the dried sample obtained in step (2) and soak it in an acidic solution of RuCl3 for 6 hours. Subsequently, wash the sample with deionized water and then at 60°C. o Drying at C overnight to prepare Ru / NiMoO 4-x Nanospheres. The scanning electron microscope (SEM) results of this material are shown in the figure. Figure 3 This confirms that the material has a nanosphere morphology. The X-ray diffraction (XRD) results of the material are shown in the figure. Figure 4 This proves that the material is a Ru / NiMoO4 phase. Figure 5 Ru / NiMoO 4-x The high-resolution transmission electron microscope (HRTEM) image of the sample shows the presence of Ru and NiMoO4 lattices in the sample; Figure 6 Ru / NiMoO 4-x Images obtained from Fourier and inverse Fourier transforms of the sample show the presence of numerous O vacancies in the catalyst. During testing in an electrolyzer containing the catalyst, the prepared material served as the cathode in the seawater electrolysis reactor. The Ru / NiMoO prepared above... 4-x The electrocatalyst exhibits excellent HER activity. Figure 7 It requires only a 2.11 V operating voltage to achieve 3.0 A cm⁻¹. -2 current density ( Figure 8 This indicates that Ru / NiMoO 4-x The two-electrode electrolysis system, with the cathode as the electrode, exhibits excellent catalytic activity and can achieve catalytic activity at 1.5 A cm⁻¹. -2 Stable operation for 10 hours at current density ( Figure 9 This indicates that Ru / NiMoO 4-x The two-electrode electrolysis system, which serves as the cathode, exhibits excellent long-term durability.

[0024] Example 2

[0025] This invention discloses a method for preparing oxygen-vacancy-rich ruthenium / nickel molybdate (Ru / NiMoO4), comprising the following steps:

[0026] (1) Commercially available nickel foam, Ni(NO3)2·6H2O and Na2MoO4·2H2O were selected as raw materials. The three were added to 30 mL of water to dissolve them. Then the mixture solution was transferred to a 50 mL stainless steel autoclave and heated at 160 °C. o Heat at C for 6 hours.

[0027] (2) Then, take an appropriate amount of the dried sample obtained in step (1) and soak it in an acidic solution of RuCl3 for 6 hours. Subsequently, wash the sample with deionized water and then at 60°C. o Ru / NiMoO4 nanospheres were prepared by drying at C overnight.

[0028] The bifunctional electrocatalysts obtained in the above examples exhibit excellent hydrogen evolution reaction activity. Figure 10 ). Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of the NiMoO4 sample from Example 1.

[0030] Figure 2 The NiMoO sample in Example 1 4-x Scanning electron microscope image.

[0031] Figure 3 The sample Ru / NiMoO in Example 1 4-x Scanning electron microscope image.

[0032] Figure 4 The sample Ru / NiMoO in Example 1 4-x X-ray diffraction images.

[0033] Figure 5 The sample Ru / NiMoO in Example 1 4-x High-resolution transmission electron microscope image.

[0034] Figure 6 The sample Ru / NiMoO in Example 1 4-x Images with Fourier and inverse Fourier transforms.

[0035] Figure 7 The sample Ru / NiMoO in Example 1 4-x Properties of the hydrogen evolution reaction; the horizontal axis E (V) vs. RHE represents voltage (V), and the vertical axis Current density represents current density (A cm⁻¹). -2 ).

[0036] Figure 8 The sample Ru / NiMoO in Example 1 4-x Properties of the seawater electrolyzer as the cathode; the horizontal axis represents voltage (V), and the vertical axis represents current density (A cm⁻¹). -2 ).

[0037] Figure 9 The sample Ru / NiMoO in Example 1 4-x Stability test of seawater electrolysis cell as cathode; the horizontal axis Time is time (h), and the vertical axis E (V) vs. RHE is voltage (V).

[0038] Figure 10 The hydrogen evolution reaction properties of the Ru / NiMoO4 sample in Example 2 are shown; the horizontal axis E (V) vs. RHE represents voltage (V), and the vertical axis Current density represents current density (A cm⁻¹). -2 ).

Claims

1. A method for preparing an oxygen-enriched vacancy ruthenium / nickel molybdate electrocatalyst, characterized in that, The preparation is carried out by the following steps: (1) Cut the nickel foam substrate into appropriate sizes, then immerse it in dilute hydrochloric acid, deionized water and ethanol in sequence, clean it with ultrasonication and dry it in a vacuum drying oven overnight; (2) Dissolve Ni(NO3)2•6H2O and Na2MoO4•2H2O in deionized water and stir for 5 to 10 minutes. The mixture solution was transferred to a stainless steel autoclave with a polytetrafluoroethylene liner; a clean piece of nickel foam was immersed in the solution, sealed in the autoclave, and heated at 160-180 °C for 5-10 hours. The prepared sample was removed and washed with deionized water to obtain NiMoO4 nanowires; (3) NiMoO4 nanowires were immersed in NaBH4 solution at room temperature for 10-30 minutes; then the sample was washed with deionized water and dried overnight at 60-80 °C to prepare NiMoO4 nanowires. 4-x Nanowires; (4) NiMoO 4-x Nanowires were uniformly dispersed in an acidic solution containing RuCl3 for 4–6 hours; finally, the sample was washed with deionized water and dried overnight at 60–80 °C to prepare Ru / NiMoO. 4-x Nanospheres.

2. The application of the electrocatalyst obtained by the preparation method of the oxygen-enriched vacancy ruthenium / nickel molybdate electrocatalyst according to claim 1, characterized in that, The electrocatalyst is used as a cathode in a seawater electrolyzer.

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