Preparation of porous titanium carbide supported copper-molybdenum sulfide electrode material and application thereof

Abstract

The present application relates to a kind of porous titanium carbide (MXene) load copper molybdenum sulfide (Cu2S / MoS2@C / MXene) electrode material preparation, the composite material obtained is used for electrocatalytic nitrate reduction synthesis ammonia at normal temperature and pressure.The present application is by in-situ growth synthesis method copper ion is introduced in layered MXene dispersion, forms MXene hydrogel, with it as base, in-situ growth NENU-5, obtains NENU-5 / MXene composite material, further through high-temperature sulfuration process, obtains Cu2S / MoS2@C / MXene composite material.The material combines the advantages of Cu2S, MoS2 and MXene, improves the stability of catalyst, conductivity and electrocatalytic performance.The electrocatalyst prepared in the present application has a yield of 20.24mg h ‑1 mgcat. ‑1 for the reduction of nitrate to synthesize ammonia, and a faradic efficiency of 85.34%.The preparation process of the present application is simple and convenient, and the cost is low, and the obtained material has good electrocatalytic synthesis ammonia performance.

Description

Technical Field

[0001] This invention relates to the field of catalyst materials for the electrocatalytic reduction of nitrate to ammonia synthesis, specifically the preparation and application of a porous titanium carbide-supported copper-molybdenum sulfide electrode material. Background Technology

[0002] Nitrate (NO3) - NO3 is a common pollutant in surface water and groundwater. - The accumulation of NO3 is mainly caused by human activities, such as the burning of fossil fuels, the overuse of nitrogen-rich fertilizers, and wastewater discharge. - The presence of NO3 can cause eutrophication in water bodies, thereby reducing the oxygen available to aquatic organisms and damaging aquatic ecosystems. Furthermore, NO3 in the human body... - It can be reduced to nitrite (NO2) by microorganisms in the gastrointestinal tract. - This can lead to liver damage, methemoglobinemia, and even cancer. Therefore, researchers are trying various methods to reduce NO3 in water. - The content of.

[0003] Electrocatalytic NO3 - The reduction synthesis of ammonia has its unique advantages. First, it electrocatalyzes NO3-. - Ammonia, the main product of ammonia reduction synthesis, is a fundamental raw material for the production of nitrogen fertilizers and fibers, and has high application value. Secondly, the electrical energy used in the electrochemical reaction can be obtained from renewable energy sources. Thirdly, in the electrochemical reaction, electrons act as a reducing agent, neither introducing new impurities nor causing secondary pollution to the environment. However, electrocatalysis of NO3... - Reduction is a complex reaction process involving multiple redox reactions and spanning multiple valence states. It has numerous reduction pathways and is accompanied by the formation of many intermediates and byproducts. Therefore, exploring electrode materials with excellent catalytic activity is crucial for the electrocatalysis of NO3-. - The research focus is on the reduction synthesis of ammonia.

[0004] Transition metal carbon / nitrogen / carbonitridion compound (MXene) materials have wide applications in energy storage, sensing, catalysis, and biology due to their unique morphology, metalloid conductivity, and high chemical stability. Cuprous sulfide (Cu₂S) is a narrow-bandgap p-type semiconductor material with good chemical and thermal stability, making it an excellent conductor. Molybdenum disulfide (MoS₂) consists of three atomic layers, with molybdenum atoms sandwiched between two sulfur atoms, forming a unique layered morphology similar to a "sandwich," thus exhibiting excellent anisotropy and electrocatalytic performance.

[0005] Polyoxometalate-based metal-organic frameworks (POMOFs) are constructed by introducing polyoxometalates (POMs) as guest molecules into the host metal-organic framework (MOF). They not only retain the excellent physicochemical properties of POMs themselves, but also provide a platform for the good dispersion of POMs through the high porosity of the MOF. Using POMOFs as precursors, multi-component metal composites with heterogeneous interfaces can be prepared. This invention uses a phosphomolybdenum polyoxometalate-based copper metal-organic framework (NENU-5) composite material (NENU-5@MXene) grown in situ on the surface of three-dimensional porous MXene as a precursor, and further obtains a three-dimensional porous MXene-supported copper-molybdenum sulfide composite material (Cu2S / MoS2@C / MXene) through high-temperature calcination, which is then applied to the electrocatalysis of NO3. - The reduction synthesis of ammonia is a promising and significant research endeavor. Summary of the Invention

[0006] The purpose of this invention is to synthesize a NENU-5 / MXene composite material by in-situ growth of a copper metal-organic framework (NENU-5) on a three-dimensional porous MXene structure, and further prepare a Cu2S / MoS2@C / MXene composite material by high-temperature calcination in a tube furnace. The in-situ growth of Cu2S and MoS2 with synergistic catalytic activity on the MXene surface can prevent the accumulation of MXene nanosheets, increase the specific surface area of ​​the composite material, and maintain the good conductivity and stability of MXene. Using this material as a catalyst can improve the electrocatalytic reduction of nitrate to ammonia.

[0007] To achieve the objectives of the invention described above, the present invention provides the following technical solution:

[0008] I. Preparation of MXene hydrogel: A monolayer of MXene was dispersed in deionized water, and copper nitrate hexahydrate (Cu(NO3)2·6H2O) was dissolved in deionized water. The two were mixed rapidly, and the MXene hydrogel was formed within a few seconds.

[0009] II. Preparation of NENU-5 / MXene: Solution A, a mixed solution of MXene hydrogel dispersion and trimesic acid; Solution B, copper acetate (Cu(Ac)2·H2O) and phosphomolybdic acid (PMo) 12 A mixed solution of NENU-5 and MXene. Solution A was quickly poured into solution B, stirred thoroughly at room temperature and pressure, washed, centrifuged, vacuum dried, and the product NENU-5 / MXene was collected.

[0010] III. Preparation of Cu2S / MoS2@C / MXene composite material: A certain amount of NENU-5 / MXene composite material and thiourea were mixed in a ratio of 1:20, placed in a crucible and calcined at high temperature in a tube furnace, cooled down, and the product was collected.

[0011] 1. The MXene hydrogel dispersion described in step one, wherein the mass of MXene is 60-65 mg (concentration is...).

[0012] 10 mg / mL), Cu(NO3)2·6H2O has a mass of 60-65 mg (concentration of 0.81 mol / L).

[0013] 2. The pyromellitic acid mentioned in step two has a mass of 0.14-0.15g and is dissolved in anhydrous ethanol.

[0014] 3. The copper nitrate mentioned in step two has a mass of 0.2-0.3g (concentration of 0.025mol / L).

[0015] 4. The phosphomolybdic acid mentioned in step two has a mass of 0.3 to 0.4 g.

[0016] 5. The stirring time in step two is 30 minutes, and the washing is performed several times with anhydrous ethanol and deionized water respectively.

[0017] 6. The NENU-5 / MXene composite material described in step three has a mass of 0.2 to 0.3 g.

[0018] 7. The thiourea mentioned in step three has a mass of 4-5g.

[0019] 8. The temperature of the tube furnace mentioned in step 3 is 800℃, and the calcination time is 2 hours. The heating and cooling rates are 7℃ / min.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention yields a porous titanium carbide-supported copper-molybdenum sulfide electrode material, Cu2S / MoS2@C / MXene. The three-dimensional porous MXene possesses a larger specific surface area, effectively preventing the re-stacking of two-dimensional MXene nanosheets and facilitating the loading of catalytically active materials. Simultaneously, the functional groups on the MXene surface exhibit certain reactivity and electronegativity, promoting the deprotonation of organic ligands as strong electron donors. This allows NENU-5 to nucleate in situ on the MXene surface, resulting in NENU-5 / MXene, which is further synthesized into a Cu2S / MoS2@C / MXene composite material through high-temperature calcination. The uniform dispersion of Cu2S and MoS2 on the porous MXene surface solves problems such as catalyst structural instability and poor conductivity. When this material is used for the electrocatalytic reduction of nitrate to ammonia, its electrocatalytic performance is significantly improved. Attached Figure Description

[0022] Figure 1 The image shows a comparison of the Fourier transform infrared (FT-IR) spectra of the Cu2S / MoS2@C / MXene composite material prepared in Embodiment 1 of the present invention.

[0023] Figure 2 The image shows a scanning electron microscope (SEM) image of the Cu2S / MoS2@C / MXene composite material prepared for Embodiment 1 of the present invention.

[0024] Figure 3 The image shows the X-ray diffraction (XRD) pattern of the Cu2S / MoS2@C / MXene composite powder prepared in Embodiment 1 of the present invention.

[0025] Figure 4 The Cu2S / MoS2@C / MXene composite material prepared for Embodiment 1 of the present invention, with or without NO3 - Current-potential (LSV) curve in electrolyte.

[0026] Figure 5 The Cu2S / MoS2@C / MXene composite material prepared for Embodiment 1 of the present invention was subjected to nitrate reduction to ammonia synthesis reaction in neutral electrolytes (0.1 mol / L Na2SO4 and 0.1 mol / L NaNO3). After 1 hour of testing at different voltages, the ultraviolet-visible absorption spectra of the electrolytes were obtained.

[0027] Figure 6The Cu2S / MoS2@C / MXene composite material prepared for Embodiment 1 of the present invention was subjected to nitrate reduction to ammonia synthesis reaction in neutral electrolytes (0.1 mol / L Na2SO4 and 0.1 mol / L NaNO3). The ammonia yield and Faraday efficiency were measured after 1 hour at different voltages. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to implementation, comparative cases and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0029] Implementation Case 1

[0030] This embodiment provides a Cu2S / MoS2@C / MXene composite electrocatalyst, which is prepared according to the following method:

[0031] Preparation of MXene hydrogel: A monolayer of MXene was dispersed in deionized water, and Cu(NO3)2·6H2O was dissolved in deionized water. The two were mixed rapidly, and the MXene hydrogel was formed within a few seconds.

[0032] Preparation of NENU-5 / MXene: Solution A, a mixed solution of MXene hydrogel dispersion and trimesic acid; Solution B, Cu(Ac)2·H2O and PMo 12 A mixed solution. Quickly pour solution A into solution B, stir thoroughly at room temperature and pressure, wash, centrifuge, vacuum dry, and collect the product.

[0033] Preparation of Cu2S / MoS2@C / MXene composite material: A certain amount of NENU-5 / MXene composite material and thiourea were mixed in a ratio of 1:20, placed in a crucible and calcined at high temperature in a tube furnace, cooled down and the product was collected.

[0034] Comparison Case 1

[0035] This comparative case provides a Cu2S@C / MXene composite electrocatalyst, which differs from Example 1 in that PMo is not added to solution B in step two. 12 .

[0036] Comparison Case 2

[0037] This comparative case provides a MoS2@C / MXene composite electrocatalyst, which differs from Implementation Case 1 in that Cu(Ac)2·H2O is not added to solution B in step two.

[0038] The invention will be further described below with reference to the accompanying drawings:

[0039] Figure 1The Fourier transform infrared spectrum comparison of the Cu2S / MoS2@C / MXene composite material prepared in Embodiment 1 of the present invention is shown in the figure. As can be seen from the figure, the wavelengths in the 1571-1673 cm⁻¹ range are... -1 Within the range, relatively weak broad peaks can be observed, which are attributed to the vibrations of ν(CC) and ν(CH) generated in the carbon layer formed after the organic ligands in NENU-5 / MXene are calcined. Furthermore, the composite material exhibits obvious Cu2S@C / MXene and MoS2@C / MXene infrared characteristic peaks, indicating that both are successfully loaded onto MXene.

[0040] Figure 2 The images show scanning electron microscope (SEM) images of the Cu2S / MoS2@C / MXene composite material prepared according to Embodiment 1 of the present invention. As shown in Figure a, the MXene substrate surface is rough and has a distinct three-dimensional porous structure. As shown in Figures b and c, nanoparticle structures are distributed on the MXene surface, indicating that Cu2S and MoS2 were successfully loaded onto the three-dimensional porous MXene.

[0041] Figure 3 X-ray diffraction pattern of Cu2S / MoS2@C / MXene composite powder prepared for Embodiment 1 of the present invention. As shown in the figure, the 2θ peaks at 27.4°, 31.7°, 45.5°, and 53.9° belong to the (111), (200), (220), and (311) crystal planes of Cu2S, respectively, which conforms to the Cu2S standard card (JCPDS NO.84-1770); the 2θ peaks at 14.1°, 32.9°, 35.9°, 43.3°, and 69.1° belong to the (002), (100), (102), (006), and (200) crystal planes of MoS2, respectively, which conforms to the MoS2 standard card (JCPDS NO.75-1539); and the Cu2S / MoS2@C / MXene composite material has the characteristic peaks of MXene, indicating that Cu2S and MoS2 were successfully loaded onto MXene, and the Cu2S / MoS2@C / MXene composite material was successfully synthesized.

[0042] Figure 4 The Cu2S / MoS2@C / MXene composite material prepared for Embodiment 1 of the present invention, with or without NO3 - Electrochemical linear sweep voltammogram in the electrolyte. As shown in the figure, within the voltage range of -1.1V vs. RHE to -1.5V vs. RHE, the reduction current density of the Cu2S / MoS2@C / MXene composite material in the electrolyte containing nitrate ions is significantly higher than that in the electrolyte without nitrate ions, indicating that the Cu2S / MoS2@C / MXene composite material has a certain electrocatalytic nitrate reduction capability.

[0043] Figure 5 The Cu2S / MoS2@C / MXene composite material prepared for Embodiment 1 of this invention underwent a nitrate reduction to ammonia synthesis reaction in neutral electrolytes (0.1 mol / L Na2SO4 and 0.1 mol / L NaNO3). The UV-Vis absorption spectra of the electrolytes were measured after 1 hour at different voltages. As shown in the figure, with the increase of the applied voltage, the absorbance of the electrolyte after electrocatalytic testing and color development gradually increased in the absorbance test.

[0044] Figure 6 The Cu2S / MoS2@C / MXene composite material prepared for Embodiment 1 of this invention underwent a nitrate reduction to ammonia synthesis reaction in neutral electrolytes (0.1 mol / L Na2SO4 and 0.1 mol / L NaNO3). The ammonia yield and Faradaic efficiency were measured after 1 hour at different voltages. As shown in the figure, the highest Faradaic efficiency of 85.34% was achieved at a potential of -1.3 V vs. RHE, with a corresponding ammonia yield of 20.24 mg / h. –1 mg cat. 1 Therefore, Cu2S / MoS2@C / MXene composite material can serve as a highly efficient electrocatalytic catalyst for the reduction of nitrates to ammonia.

[0045] In summary, the Cu₂S / MoS₂@C / MXene composite material of Example 1 was successfully prepared using a synthesis method involving room-temperature stirring and high-temperature calcination, and it was successfully applied to the electrocatalytic reduction of nitrate to ammonia. The addition of MXene increased the specific surface area and electron transport rate of the composite material, while the synergistic catalytic effect of Cu₂S and MoS₂ enhanced the electrocatalytic activity. This material exhibits good redox activity, excellent conductivity, and electrocatalytic stability, showing great potential in the electrocatalytic reduction of nitrate to ammonia.

Claims

1. A method for preparing a Cu2S / MoS2@C / MXene composite material, characterized in that, Comprising the following steps: (1) Preparation of MXene hydrogel: 60-65 mg of single-layer MXene is dispersed in deionized water to form a dispersion liquid with a concentration of 10 mg / mL, 60-65 mg of copper nitrate hexahydrate (Cu(NO3)2·6H2O) is dissolved in deionized water to form a solution with a concentration of 0.81 mol / L, and the two liquids are quickly mixed, and the MXene hydrogel is formed within a few seconds; (2) Preparation of NENU-5 / MXene: Solution A and Solution B were prepared, wherein Solution A was a mixed solution of MXene hydrogel dispersion and 0.14-0.15 g of trimesic acid in anhydrous ethanol, and Solution B was a mixed solution of 0.2-0.3 g of copper acetate (Cu(Ac)2·H2O) and 0.3-0.4 g of phosphomolybdic acid (PMo12O40·H2O) in anhydrous ethanol, and the concentration of copper acetate in Solution B was 0.025 mol / L; Solution A was quickly poured into Solution B, stirred at room temperature and normal pressure for 30 min, washed with anhydrous ethanol and deionized water several times in sequence, vacuum dried after centrifugation, and the product NENU-5 / MXene was collected. 12 ) Preparation of NENU-5 / MXene: Solution A and Solution B were prepared, wherein Solution A was a mixed solution of MXene hydrogel dispersion and 0.14-0.15 g of trimesic acid in anhydrous ethanol, and Solution B was a mixed solution of 0.2-0.3 g of copper acetate (Cu(Ac)2·H2O) and 0.3-0.4 g of phosphomolybdic acid (PMo12O40·H2O) in anhydrous ethanol, and the concentration of copper acetate in Solution B was 0.025 mol / L; Solution A was quickly poured into Solution B, stirred at room temperature and normal pressure for 30 min, washed with anhydrous ethanol and deionized water several times in sequence, vacuum dried after centrifugation, and the product NENU-5 / MXene was collected. (3) Preparation of Cu2S / MoS2@C / MXene composite material: 0.2-0.3 g of NENU-5 / MXene composite material is mixed with 4-5 g of thiourea at a mass ratio of 1:20, placed in a tube furnace, heated to 800℃ at a rate of 7℃ / min, calcined for 2h, and then cooled at a rate of 7℃ / min, and the product is collected to obtain the Cu2S / MoS2@C / MXene composite material.

2. The use of the Cu2S / MoS2@C / MXene composite material prepared by the preparation method of claim 1, characterized in that, The composite material is used as an electrode material and applied to the electrocatalytic reduction of nitrate to synthesize ammonia at room temperature and normal pressure.

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