Ni-W bimetallic catalyst, its preparation method and application

Abstract

The application relates to a Ni-W bimetallic catalyst and a preparation method and application thereof, and the preparation method comprises the following steps: I. dissolving a soluble nickel salt, a soluble tungsten salt, and urea and ammonium fluoride in water to form a precursor solution; II. taking carbon paper as a carrier, immersing the precursor solution obtained in the step I in water, and performing hydrothermal reaction to grow the catalyst on the carbon paper; III. performing heat treatment on the carbon paper loaded with the catalyst obtained in the step II under a nitrogen atmosphere to prepare the Ni-W bimetallic catalyst. The Ni-W bimetallic catalyst prepared by the application presents a nano flower morphology, exposes more reaction active sites, the surface of the Ni-W bimetallic catalyst co-modified by single-atom tungsten and metal defects can enhance the adsorption of 5-hydroxymethylfurfural, the bulk phase composed of the Ni-W solid solution induces the generation of more active sites, greatly improves the overall catalytic activity, and realizes high HMF conversion rate, high 2,5-furan dicarboxylic acid yield and high faraday efficiency.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a Ni-W bimetallic catalyst, its preparation method, and its application. Background Technology

[0002] Compared with the traditional thermocatalytic conversion of 5-hydroxymethylfurfural (HMF), the electro-oxidation reaction of HMF in aqueous solution shows significant advantages, including avoiding the high temperature and high pressure environment, replacing organic solvents with water phase, high energy utilization, precise voltage control of the reaction process, and green environmental protection characteristics, thus reducing environmental pollution.

[0003] In recent years, noble metal catalysts such as gold, palladium, and platinum, as well as transition metal catalysts such as iron, cobalt, and nickel, have been widely used in the catalytic system for the electrooxidation of HMF. However, due to the high cost of noble metal catalysts and the insufficient activity of transition metal catalysts, the performance of most currently designed catalysts is unsatisfactory considering both economic benefits and catalytic effects. Nickel-based catalysts possess excellent physicochemical properties and a flexible, tunable electronic structure, making them a widely studied transition metal material. In practical applications, nickel-based catalysts exhibit weak adsorption of HMF, and the intrinsic activity of the metal sites is poor, resulting in low yields and Faradaic efficiencies for the electrocatalytic oxidation of HMF to 2,5-furandicarboxylic acid (FDCA). To improve the performance of nickel-based catalysts, researchers have introduced dopant metals such as Co, Fe, and Cu to optimize the coordination environment of Ni sites and adjust the electronic states of Ni to enhance the kinetics of the reaction sites. Wang et al. introduced W to modulate the electronic structure of Ni and prepared a Ni-WOx catalyst using a co-precipitation method for the electrocatalytic oxidation of urea. The incorporation of high-valence W promoted the generation of highly intrinsic active sites, resulting in a nearly 100% performance improvement compared to the NiOx catalyst, demonstrating the catalytic potential of the Ni-W system (Angew. Chem. Int. Ed. 2021, 60, 10577.). Hu et al. prepared a three-dimensional porous WO3 / Ni electrode using a one-step hydrothermal method for HMF oxidation, but due to its simple structure, the yield and Faradaic efficiency were low (Molecular Catalysis, 2021, 504, 111459.). Currently, the challenges of weak adsorption capacity and slow kinetics of the reaction substrate in the 5-hydroxymethylfurfural oxidation reaction (HMFOR) remain unresolved. For catalytic sites in a single coordination environment, it is difficult to simultaneously possess both favorable adsorption sites and highly active catalytic sites. Summary of the Invention

[0004] The purpose of this invention is to provide a Ni-W bimetallic catalyst, its preparation method, and its application in order to solve the above-mentioned problems, thereby addressing the shortcomings of the prior art.

[0005] The present invention achieves the above objectives through the following technical solutions:

[0006] This invention provides a method for preparing a Ni-W bimetallic catalyst, comprising the following steps:

[0007] Step 1: Dissolve soluble nickel salt, soluble tungsten salt, urea, and ammonium fluoride in water to form a precursor solution;

[0008] Step 2: Using carbon paper as a carrier, immerse it in the precursor solution obtained in Step 1, and the hydrothermal reaction causes the catalyst to grow on the carbon paper.

[0009] Step 3: Heat-treat the carbon paper with the catalyst supported in Step 2 under a nitrogen atmosphere to prepare the Ni-W bimetallic catalyst.

[0010] As a further optimization of the present invention, the Ni-W bimetallic catalyst has a nanoflower-like morphology.

[0011] As a further optimization of the present invention, the soluble nickel salt is at least one of nickel nitrate, nickel chloride, and nickel sulfate.

[0012] As a further optimization of the present invention, the soluble tungsten salt is sodium tungstate.

[0013] As a further optimization of the present invention, the molar ratio of Ni to W in the precursor solution is 100:3 to 100:30.

[0014] As a further optimization of the present invention, the temperature of the hydrothermal reaction is 100-130°C and the time is 5-7 hours.

[0015] As a further optimization of the present invention, the heat treatment is carried out in a nitrogen atmosphere, with a heating rate of 1 to 2 °C / min, a heat treatment temperature of 400 to 450 °C, and a time of 2 to 3 hours.

[0016] The present invention also provides a Ni-W bimetallic catalyst, which is prepared by the above-described preparation method. The Ni-W bimetallic catalyst is composed of a surface co-modified with single-atom tungsten and metal defects, and a Ni-W solid solution bulk phase.

[0017] This invention also provides the application of a Ni-W bimetallic catalyst in the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) to prepare 2,5-furandicarboxylic acid (FDCA).

[0018] As a further optimization of the present invention, the preparation specifically involves placing the constructed three-electrode system into an electrolyte, applying an electric field, and obtaining FDCA; wherein the three-electrode system includes a working electrode containing the Ni-W bimetallic catalyst, a Hg / HgO reference electrode, and a platinum sheet counter electrode; the electrolyte includes an anolyte KOH+HMF and a catholyte KOH; the electric field voltage is 1.0-1.7V; and the catalytic time is 1-5h.

[0019] The beneficial effects of this invention are as follows:

[0020] 1) The Ni-W bimetallic catalyst of the present invention exhibits a nanoflower morphology, exposing more reactive sites. The surface of the Ni-W bimetallic catalyst, which is co-modified by single-atom tungsten and metal defects, can enhance the adsorption of 5-hydroxymethylfurfural (HMF). The bulk phase composed of Ni-W solid solution induces the generation of more active sites, which greatly improves the overall catalytic activity and achieves high HMF conversion, high 2,5-furandicarboxylic acid (FDCA) yield and high Faradaic efficiency.

[0021] 2) The surface of the Ni-W bimetallic catalyst of the present invention is co-modified with single-atom tungsten and metal defects, and the bulk phase is composed of Ni-W solid solution. This structure can enrich the adsorption sites of 5-hydroxymethylfurfural and the catalytic sites with stronger kinetics, thereby improving the overall catalytic activity and synergistically improving the performance of electro-oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid in both thermodynamic and kinetic aspects. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the Ni-W bimetallic catalyst prepared in Example 1 of the present invention.

[0023] Figure 2 This is a transmission electron microscope image of the Ni-W bimetallic catalyst prepared in Example 1 of the present invention.

[0024] Figure 3 This is a scanning transmission electron microscope image of the Ni-W bimetallic catalyst prepared in Example 1 of the present invention.

[0025] Figure 4 These are scanning transmission electron microscopy (STEM) images and energy dispersive spectroscopy (EDS) spectra of the Ni-W bimetallic catalyst prepared in Example 1 of this invention.

[0026] Figure 5 The figures show linear sweep voltammetric curves of HMFOR of a series of Ni-W bimetallic catalysts prepared in Examples 1-7 of the present invention and NiO of Comparative Example 1 in 1M KOH + 10mM HMF.

[0027] Figure 6 These are X-ray diffraction patterns of the Ni-W bimetallic catalyst prepared in Example 1 of the present invention and NiO in Comparative Example 1.

[0028] Figure 7 These are the UV-Vis spectra of the Ni-W bimetallic catalyst prepared in Example 1 of the present invention and the NiO of Comparative Example 1.

[0029] Figure 8 These are the open-circuit potential diagrams of the Ni-W bimetallic catalyst prepared in Example 1 of the present invention and the NiO of Comparative Example 1 in 1M KOH and 1M KOH+10mM HMF solutions, respectively.

[0030] Figure 9 This is a linear sweep voltammetric curve of OER and HMFOR of the Ni-W bimetallic catalyst prepared in Example 1 of the present invention in 1M KOH and 1M KOH + 10mM HMF solutions.

[0031] Figure 10 This is a graph showing the conversion rate, yield, and Faraday efficiency of the Ni-W bimetallic catalyst prepared in Example 1 of this invention for the electrocatalytic oxidation of HMF to FDCA after seven cycles. Detailed Implementation

[0032] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0033] I. Materials

[0034] Unless otherwise specified, all methods used in this application are conventional methods known to those skilled in the art, and all reagents and materials used are commercially available products unless otherwise specified.

[0035] II. Methods

[0036] Example 1

[0037] A method for preparing a Ni-W bimetallic catalyst, in this embodiment, wherein the molar ratio of Ni:W in the precursor solution is 10:1 (equivalent to 100:10), includes the following steps:

[0038] (1) Carbon paper pretreatment: Cut carbon paper with a thickness of 1 mm into 1 cm × 2 cm size, and ultrasonically treat it with 3M HCl solution, acetone, ethanol and distilled water for 30 min in sequence to remove the oxide layer and organic matter on the surface. Finally, wash it repeatedly with distilled water and dry it in a vacuum drying oven to obtain the treated carbon paper, which is used as the electrode substrate for the subsequent growth of catalyst.

[0039] (2) Preparation of precursor solution: Disperse 1.06g Ni(NO3)2·6H2O, 0.96g CO(NH2)2 and 0.3g NH4F in deionized water (60mL) to form liquid A; dissolve 120mg Na2WO4·2H2O in deionized water (20mL) to form liquid B, sonicate for 5min, then inject liquid B into liquid A and stir for 60min to form precursor solution;

[0040] (3) Hydrothermal reaction: The above precursor solution and a clean carbon paper (1cm×2cm) were transferred to a 100mL Teflon-lined stainless steel autoclave; then, the autoclave was sealed and placed in an oven at 120℃ for 5 hours; after the autoclave cooled to room temperature, the carbon paper was removed, washed several times with deionized water and ethanol respectively, and dried under vacuum at 60℃ for 5 hours.

[0041] (4) Heat treatment: The carbon paper loaded with the catalyst was placed in a tube furnace, nitrogen gas was introduced, and the temperature was increased to 400℃ at a rate of 1℃ / min. The catalyst was then placed at this temperature for 2 hours. The resulting Ni-W bimetallic catalyst was denoted as W1-Ni. 1-x O / NiWO(-10), abbreviated as W1-Ni 1-x O / NiWO.

[0042] Note: x indicates that there is an unknown amount of metal missing at the Ni site.

[0043] Example 2

[0044] In this embodiment, the preparation method is the same as in Example 1, except that the content of Na2WO4·2H2O in the precursor solution is changed to 36 mg, the molar ratio of Ni:W in the precursor solution is 100:3, and the catalyst is denoted as W1-Ni. 1-x O / NiWO-3.

[0045] Example 3

[0046] In this embodiment, the preparation method is the same as in Example 1, except that the content of Na2WO4·2H2O in the precursor solution is changed to 60 mg, the molar ratio of Ni:W in the precursor solution is 100:5, and the catalyst is denoted as W1-Ni. 1-x O / NiWO-5.

[0047] Example 4

[0048] In this embodiment, the preparation method is the same as in Example 1, except that the content of Na2WO4·2H2O in the precursor solution is changed to 84 mg, the molar ratio of Ni:W in the precursor solution is 100:7, and the catalyst is denoted as W1-Ni. 1-x O / NiWO-7.

[0049] Example 5

[0050] In this embodiment, the preparation method is the same as in Example 1, except that the content of Na2WO4·2H2O in the precursor solution is changed to 180 mg, the molar ratio of Ni:W in the precursor solution is 100:15, and the catalyst is denoted as W1-Ni. 1-x O / NiWO-15.

[0051] Example 6

[0052] In this embodiment, the preparation method is the same as in Example 1, except that the content of Na2WO4·2H2O in the precursor solution is changed to 240 mg, the molar ratio of Ni:W in the precursor solution is 100:20, and the catalyst is denoted as W1-Ni. 1-x O / NiWO-20.

[0053] Example 7

[0054] In this embodiment, the preparation method is the same as in Example 1, except that the content of Na2WO4·2H2O in the precursor solution is changed to 360 mg, the molar ratio of Ni:W in the precursor solution is 100:30, and the catalyst is denoted as W1-Ni. 1-x O / NiWO-30.

[0055] Example 8

[0056] In this embodiment, the preparation method is the same as in Example 1, except that 1.06g Ni(NO3)2·6H2O in the precursor solution is replaced with 0.87g NiCl2·6H2O, and the molar ratio of Ni:W in the precursor solution is 10:1, which is consistent with Example 1.

[0057] Example 9

[0058] In this embodiment, the preparation method is the same as in Example 1, except that 1.06g Ni(NO3)2·6H2O in the precursor solution is replaced with 1.03g NiSO4·7H2O, and the molar ratio of Ni:W in the precursor solution is 10:1, which is consistent with Example 1.

[0059] Comparative Example 1

[0060] In this comparative example, the preparation method is the same as that in Example 1. The only difference from Example 1 is that sodium tungstate is not added to the precursor solution in this comparative example, and the catalyst obtained is denoted as NiO.

[0061] Comparative Example 2

[0062] In this comparative example, the preparation method is the same as in Example 1, except that the 120 mg Na₂WO₄·2H₂O in the precursor solution is replaced with 88 mg (NH₄)₆H₂WO₄. 12 O 40 ·xH2O was used to maintain the N:W molar ratio in the precursor solution at 10:1, consistent with Example 1.

[0063] Comparative Example 3

[0064] In this comparative example, the preparation method is the same as in Example 1, except that the heat treatment atmosphere is changed to air.

[0065] Comparative Example 4

[0066] In this comparative example, the preparation method is the same as in Example 1, except that the heat treatment atmosphere is changed to ammonia.

[0067] The catalysts prepared above were characterized and analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM), elemental mapping (EDS), X-ray diffraction (XRD), and ultraviolet-visible spectrophotometry (UV-Vis), as detailed below:

[0068] Figure 1 and Figure 2 These are the catalysts W1-Ni from Example 1. 1-x Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of O / NiWO; such as Figure 1-2 As shown, the catalyst of Example 1 exhibits a nanoflower morphology with thin edge nanosheets;

[0069] Figure 3 The catalyst W1-Ni in Example 1 1-x Scanning transmission electron microscopy (STEM) images of O / NiWO; based on differences in atomic contrast, the brighter, more dispersed bright spots represent W single atoms, while the slightly dimmer, more regularly arranged bright spots represent Ni atoms arranged in rows. The black voids appearing in the atomic phase are metallic defects. Figure 3 As shown, the catalyst sample of Example 1 has abundant tungsten single atoms and metal defects on its surface;

[0070] Figure 4 The catalyst W1-Ni in Example 11-x Scanning transmission electron microscopy (STEM) images and energy-dispersive X-ray spectroscopy (EDS) spectra of O / NiWO3; such as Figure 4 As shown, Ni, W, and O are uniformly distributed on the surface of the catalyst sample in Example 1, and W atoms do not agglomerate, which confirms that W exists in the form of single atoms on the catalyst surface.

[0071] Performance Testing: The electrochemical performance of the catalyst was tested using a three-electrode system. All tests were conducted in an H-type electrolytic cell, with the carbon paper fixed using electrode clamps to ensure an effective exposed area of ​​1 × 1.5 cm. 2 The electrode was used as the working electrode, and an Hg / HgO electrode and a platinum sheet electrode were used as the reference and counter electrodes, respectively. An H-type electrolytic cell with a DuPont proton exchange membrane (Nafion-117) separating the anode and cathode chambers was used. Both the cathode and anode chambers contained 1M KOH solution as the electrolyte. During testing, 10 mmol / L HMF was added to the anode chamber. The linear voltammetry curves were measured in the range of 1.0–1.7 V, and the cyclic voltammetry curves were measured in the range of 0.52–1.72 V, with a scan rate of 5 mV / s for both. Details are as follows:

[0072] Figure 5 The NiO prepared in Comparative Example 1 and the tungsten-containing catalyst W1-Ni prepared in Examples 1-7 are compared. 1-x Comparison of linear sweep voltammetric curves for O / NiWO-X' (X' = 3, 5, 7, 10, 15, 20, 30); by Figure 5 It can be seen that, compared to pure NiO, W1-Ni doped with W... 1-x The HMF electrocatalytic oxidation performance of O / NiWO-X' catalysts was improved; among them, the W1-Ni catalyst prepared when the Ni:W molar ratio in the precursor solution was 10:1 was particularly enhanced. 1-x The O / NiWO-10 catalyst exhibits superior HMF electrocatalytic performance, with a lower onset site and a higher current density.

[0073] Figure 6 NiO and W1-Ni 1-x X-ray diffraction pattern of O / NiWO; by Figure 6 It can be seen that, compared to NiO, W1-Ni 1-x The appearance of new diffraction peaks in O / NiWO can be explained by the fact that after W doping, some Ni in the original NiO unit cell is replaced by W, forming a Ni-W solid solution. In this solid solution, Ni and W exhibit a regular arrangement, resulting in new XRD diffraction peaks. These new peaks are shifted to varying degrees compared to the diffraction peaks of NiO, thus proving the presence of W1-Ni. 1-xIn addition to modifying the catalyst surface, the tungsten in O / NiWO also dops the bulk phase, optimizing the overall structure of the catalyst. That is, the Ni-W bimetallic catalyst prepared in this application consists of a surface co-modified with single-atom tungsten and metal defects, as well as a Ni-W solid solution bulk phase.

[0074] Figure 7 NiO and W1-Ni 1-x UV-Vis spectrum of O / NiWO; such as Figure 7 As shown, compared to pure NiO, W1-Ni formed after doping with tungsten atoms... 1-x O / NiWO significantly reduces the band gap of the material, improves conductivity, and makes it easier for electrons to jump and participate in the reaction.

[0075] Figure 8 NiO and W1-Ni 1-x Open-circuit potential curves of O / NiWO in 1M KOH and 1M KOH+10mM HMF solutions, respectively; compared to NiO, W1-Ni 1-x O / NiWO exhibits a larger open-circuit potential difference ΔOCP after the addition of HMF, indicating that it has a stronger HMF adsorption capacity.

[0076] Figure 9 W1-Ni 1-x Linear sweep voltammetric curves of O / NiWO in 1M KOH and 1M KOH + 10mM HMF solutions for OER (oxygen evolution reaction) and HMFOR (5-hydroxymethylfurfural oxidation reaction); indicating that W1-Ni 1-x O / NiWO exhibits high activity for the electrocatalytic oxidation of HMF, but low activity for OER, ensuring that competitive side reactions are weak during the HMF oxidation process and maintaining high Faradaic efficiency of the reaction.

[0077] Figure 10 W1-Ni 1-x The HMF conversion, yield, and Faradaic efficiency diagram for seven cycles of O / NiWO electrocatalytic oxidation of HMF to prepare FDCA; indicating that the W1-Ni 1-x O / NiWO possesses high HMF conversion rate, high yield, high Faraday efficiency, and relatively high stability.

[0078] The catalysts prepared in Examples 1, 8, and 9, and Comparative Examples 1-4, were used to electrocatalytically oxidize HMF to FDCA. The experimental conditions and the HMF conversion, yield, and Faraday efficiency are recorded in Table 1.

[0079] Table 1

[0080]

[0081] Experimental Conclusions: The HMF conversion, FDCA yield, and Faraday efficiency of Examples 1, 8, 9, and Comparative Examples 1-4 are shown in the table above. It can be seen that the Ni-W bimetallic catalysts prepared according to this experimental method all exhibit superior performance compared to pure NiO, demonstrating the universality of this preparation method. Among them, the catalysts using Ni(NO3)2·6H2O and Na2WO4·2H2O as Ni and W sources, respectively, have the best performance. In addition, the heat treatment atmosphere has a significant impact on the material properties. The catalysts obtained under a nitrogen atmosphere have the best effect, while the yield and Faraday efficiency of the catalysts obtained under air and ammonia atmospheres cannot reach the effect of the nitrogen atmosphere.

[0082] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a Ni-W bimetallic catalyst, characterized in that: Includes the following steps: Step 1: Dissolve nickel nitrate, sodium tungstate, urea, and ammonium fluoride in water to form a precursor solution; Step 2: Using carbon paper as a carrier, immerse it in the precursor solution obtained in Step 1, and the hydrothermal reaction causes the catalyst to grow on the carbon paper. Step 3: Heat-treat the carbon paper with the catalyst supported in Step 2 under a nitrogen atmosphere to prepare the Ni-W bimetallic catalyst.

2. The method for preparing a Ni-W bimetallic catalyst according to claim 1, characterized in that: The Ni-W bimetallic catalyst exhibits a nanoflower-like morphology.

3. The method for preparing a Ni-W bimetallic catalyst according to claim 1, characterized in that: In the precursor solution, the molar ratio of Ni to W is 100:3 to 100:

30.

4. The method for preparing a Ni-W bimetallic catalyst according to claim 1, characterized in that: The hydrothermal reaction is carried out at a temperature of 100–130°C for 5–7 hours.

5. The method for preparing a Ni-W bimetallic catalyst according to claim 1, characterized in that: The heat treatment is carried out in a nitrogen atmosphere, with a heating rate of 1-2℃ / min, a heat treatment temperature of 400-450℃, and a time of 2-3 hours.

6. A Ni-W bimetallic catalyst, characterized in that: It is prepared by any one of the preparation methods described in claims 1-5.

7. The application of the Ni-W bimetallic catalyst as described in claim 6 in the electrocatalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid.

8. The application according to claim 7, characterized in that: The preparation process specifically involves placing the constructed three-electrode system into an electrolyte, applying an electric field, and obtaining FDCA. The three-electrode system includes a working electrode containing the Ni-W bimetallic catalyst, a Hg / HgO reference electrode, and a platinum sheet counter electrode. The electrolyte includes an anolyte KOH+HMF and a catholyte KOH. The electric field voltage is 1.0–1.7 V, and the catalytic time is 1–5 h.

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