Ni-based catalyst, preparation method and application in methanol electrochemical oxidation reaction

Abstract

The application discloses a Ni-based catalyst, a preparation method and application of the Ni-based catalyst in methanol electrochemical oxidation reaction, and particularly provides a preparation method of Ni5(II)O(OH)8, realizes artificial synthesis of Ni5(II)O(OH)8 for the first time, and the Ni5(II)O(OH)8 is used as a main active phase of methanol electrochemical oxidation; the unique crystal structure of the Ni5(II)O(OH)8 makes the Ni5(II)O(OH)8 have significantly enhanced intrinsic oxidation resistance after being coupled with FeOOH, and effectively inhibits irreversible conversion of Ni(II) to high-valence Ni species such as NiOOH at an oxidation potential. The application further provides a Ni5(II)O(OH)8 / FeOOH catalyst with a core-shell heterostructure, and an interface structure with a crystal lattice matching relationship is formed between the Ni5(II)O(OH)8 and the FeOOH. When the Ni5(II)O(OH)8 and the Ni5(II)O(OH)8 / FeOOH are applied to methanol electrochemical oxidation reaction for preparing formate, compared with a traditional nickel-based catalyst, the Ni5(II)O(OH)8 and the Ni5(II)O(OH)8 / FeOOH have a lower current response starting potential and a higher current density at the same potential. The application provides a new type of high-stability electrocatalyst for methanol electrochemical oxidation for preparing formate.

Description

Technical Field

[0001] This invention relates to the field of electrochemical catalysis technology, and in particular to a Ni-based catalyst, its preparation method, and its application in the electrochemical oxidation reaction of methanol. Background Technology

[0002] Methanol is a widely available, high-energy-density, and easily stored and transported carbonaceous compound, considered an important liquid energy carrier and basic chemical raw material. In electrolysis systems driven by renewable energy sources (such as wind and solar power), the selective oxidation of methanol to formate via electrochemical means not only achieves high-value-added conversion of methanol but also enables the efficient storage and utilization of electrical energy into chemical energy, demonstrating significant application potential in energy conversion and carbon cycle systems. Furthermore, compared to the oxygen evolution reaction (1.23 V vs. reversible hydrogen electrode), the selective oxidation of methanol to formate exhibits a lower theoretical reaction potential (0.19 V vs. reversible hydrogen electrode) and faster reaction kinetics, showing promising application prospects in electrolytic coupling reaction systems.

[0003] Currently, catalysts used for the electrochemical oxidation of methanol mainly include noble metal catalysts (such as Pt, Pd and their alloys) and non-noble metal catalysts (such as Ni and Co-based materials). Among them, Ni-based catalysts have attracted widespread attention due to their abundant resources, low cost, and high catalytic activity for methanol oxidation under alkaline conditions. However, traditional Ni-based catalysts often undergo structural or phase transformations at higher oxidation potentials, and are easily oxidized to form high-valence Ni species such as NiOOH (NiO2). 3+ or Ni 4+ These high-valence Ni species promote the competitive oxygen evolution reaction (OER), thereby reducing the selectivity of methanol to formate production and failing to meet the requirements for high reaction selectivity and long-term stable operation under renewable power fluctuation conditions. Therefore, achieving stable Ni(II) active sites over a wide potential range and preventing the formation of high-valence Ni-based phases such as NiOOH to suppress the competitive OER side reaction is of great significance for realizing a highly selective methanol-to-formate production process driven by renewable power. Summary of the Invention

[0004] The purpose of this invention is to provide a Ni-based catalyst, its preparation method, and its application in the electrochemical oxidation of methanol. This addresses the problem that traditional Ni-based catalysts are easily oxidized to high-valence Ni species such as NiOOH under high potential conditions, thereby achieving highly selective oxidation of methanol to formate over a wider oxidation potential range.

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

[0006] A first aspect of the present invention provides a Ni-based catalyst, wherein the Ni-based catalyst is... Ni5(Ⅱ)O(OH)8 / FeOOH catalysts with shell / core heterogeneous nanosheet structures or Ni5(Ⅱ)O(OH)8 catalysts with nanofiber structures.

[0007] A second aspect of the present invention provides a method for preparing the above-mentioned Ni-based catalyst, wherein the Ni-based catalyst is a Ni5(Ⅱ)O(OH)8 / FeOOH catalyst having a shell / core heterogeneous nanosheet structure, comprising the following steps: S1. Pre-treat the conductive substrate; S2. Add the nickel salt precursor, iron salt precursor and alkaline regulator to deionized water, mix and stir to form a uniform mixture. S3. The pretreated conductive substrate is placed in the mixed solution and subjected to a hydrothermal reaction to form a Ni-based catalyst, namely Ni5(Ⅱ)O(OH)8 / FeOOH catalyst, which is grown in situ on the surface of the conductive substrate.

[0008] A third aspect of the present invention provides a method for preparing the above-mentioned Ni-based catalyst, wherein the Ni-based catalyst is a Ni5(Ⅱ)O(OH)8 catalyst having a nanofiber structure, comprising the following steps: A1. Pretreatment of the conductive substrate; A2. Add the nickel salt precursor and alkaline regulator to deionized water, mix and stir to form a homogeneous mixed solution; A3. The pretreated conductive substrate is placed in a mixed solution and subjected to a hydrothermal reaction to form a Ni-based catalyst, namely Ni5(Ⅱ)O(OH)8 catalyst, which is grown in situ on the surface of the conductive substrate.

[0009] Preferably, in steps S1 and A1, the conductive substrate is selected from any one of nickel foam, carbon cloth, or carbon paper.

[0010] Preferably, in steps S1 and A1, the pretreatment of the conductive substrate includes: sequentially placing the conductive substrate in an acidic solution, deionized water, and an organic solvent for cleaning to remove the surface oxide layer and impurities; the acidic solution is one or a combination of two or more of dilute hydrochloric acid, dilute sulfuric acid, or dilute nitric acid, with a mass fraction of 1% to 10%; the organic solvent is one or a combination of two or more of acetone, ethanol, or isopropanol; the cleaning is performed using ultrasonic cleaning, with each cleaning step lasting 10 to 40 minutes.

[0011] Preferably, in step S2, the iron salt precursor is selected from one or more combinations of ferric nitrate, ferric chloride, or ferric sulfate.

[0012] Preferably, in step S2, the molar ratio of the nickel salt precursor, the iron salt precursor and the alkaline regulator is 1:(0.1~10):(1~50).

[0013] Preferably, in step A2, the molar ratio of the nickel salt precursor to the alkaline regulator is 1:(1~50).

[0014] Preferably, in steps S2 and A2, the nickel salt precursor is selected from one or more combinations of nickel nitrate, nickel chloride, or nickel sulfate; and the alkalinity regulator is selected from one or more combinations of urea, ammonium carbonate, sodium hydroxide, or potassium hydroxide.

[0015] Preferably, in steps S3 and A3, the temperature of the hydrothermal reaction is 100 ~ 200 ℃, and the reaction time is 4 ~ 24 h.

[0016] Preferably, in steps S3 and A3, after the hydrothermal reaction is completed, a post-processing step is performed, specifically: after the reaction is completed, the reaction product is taken out and washed and dried.

[0017] Preferably, the washing reagent is deionized water and / or ethanol; the drying is carried out under vacuum at 40-80°C for 6-24 hours.

[0018] A fourth aspect of the present invention provides the application of Ni5(Ⅱ)O(OH)8 catalyst or Ni5(Ⅱ)O(OH)8 / FeOOH catalyst in the electrochemical oxidation reaction of methanol. Specifically, a conductive substrate supported on the above-mentioned Ni5(Ⅱ)O(OH)8 or Ni5(Ⅱ)O(OH)8 / FeOOH is used as the working electrode in the methanol electrochemical oxidation reaction system to achieve selective conversion of methanol to formate.

[0019] Preferably, the conductive substrate loaded with Ni5(Ⅱ)O(OH)8 or Ni5(Ⅱ)O(OH)8 / FeOOH is selected from nickel foam, carbon cloth or carbon paper, and is more preferably nickel foam, and is used as the working electrode for the electrochemical oxidation reaction of methanol.

[0020] Preferably, the electrolyte in the methanol electrochemical oxidation reaction system is a mixed solution of alkaline electrolyte and methanol, wherein the alkaline electrolyte is a potassium hydroxide solution with a concentration of 0.1 ~ 5.0 M and the methanol concentration is 0.1 ~ 5.0 M.

[0021] Preferably, the methanol electrochemical oxidation reaction adopts a three-electrode system, wherein the working electrode is a conductive substrate supported on Ni5(Ⅱ)O(OH)8 or Ni5(Ⅱ)O(OH)8 / FeOOH, the reference electrode is an Ag / AgCl electrode or a Hg / HgO electrode, and the counter electrode is a platinum electrode or a carbon-based electrode.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention discloses a method for preparing a Ni-based catalyst and its application in the electrochemical oxidation of methanol. Specifically, it provides a method for preparing a Ni5(II)O(OH)8 catalyst. The Ni5(II)O(OH)8 catalyst prepared by this method exhibits a nanofiber morphology, achieving the first artificial synthesis of Ni5(II)O(OH)8, which serves as the main active phase in the electrochemical oxidation of methanol. This material differs from traditional Ni(OH)2, NiFe-LDH, and other nickel-based catalysts. Its unique crystal structure gives it significantly enhanced intrinsic antioxidant capacity after coupling with FeOOH, effectively suppressing the irreversible transformation of Ni(II) to high-valence Ni species such as NiOOH at the oxidation potential, thereby avoiding competitive oxygen evolution side reactions caused by changes in the active phase. This catalyst provides a new material basis for solving the common problem of a sharp decline in selectivity of traditional Ni-based catalysts with increasing potential.

[0023] (2) This invention also provides a Ni5(II)O(OH)8 / FeOOH catalyst with a core-shell heterostructure, wherein the constructed Ni5(II)O(OH)8 and FeOOH form an interface structure with a lattice-matched relationship. Directed electron transfer from Ni5(II)O(OH)8 to FeOOH is generated through interface orbital coupling and energy level modulation. This electron rearrangement process optimizes the adsorption capacity of the Ni5(II)O(OH)8 surface for methanol molecules and its activation effect on key reaction intermediates, thereby improving the catalytic efficiency of methanol oxidation to formate. The construction of the Ni5(II)O(OH)8 / FeOOH shell / core heterostructure achieves a synergistic effect of "structural stability" and "performance enhancement," which is key to achieving high selectivity conversion of methanol over a wide potential range.

[0024] (3) The catalyst raw materials obtained by the present invention are widely available and inexpensive. The preparation process is simple and reproducible, and has good potential for large-scale preparation and engineering application prospects.

[0025] (4) The preparation method of the present invention is simple and suitable for large-scale industrial production. Attached Figure Description

[0026] Figure 1 The XRD patterns of the catalysts prepared in Examples 1 and 2 are shown below. Figure 2SEM images of the catalysts prepared in Examples 1 and 2; Figure 3 Here are high-resolution transmission electron microscope images of the catalyst prepared in Example 1 and its corresponding energy-dispersive X-ray spectral elemental distribution map; Figure 4 The HAADF-STEM image of the catalyst prepared in Example 2 and its corresponding energy-dispersive X-ray spectral elemental distribution map are shown below. Figure 5 Here is an HRTEM image of the catalyst prepared in Example 2; Figure 6 Ni 2 is the catalyst prepared in Examples 1 and 2. p Regional X-ray photoelectron spectroscopy; Figure 7 Linear sweep voltammetry (LSV) curves of the catalysts prepared in Examples 1, 2 and Comparative Example 1 in the electrochemical oxidation reaction of methanol; Figure 8 The graph shows the relationship between the Faraday efficiency (FE) of the catalyst prepared in Example 2 for the formation of formate in the electrochemical oxidation reaction of methanol and the change in potential. Figure 9 The image shows the in-situ Raman spectrum of the catalyst prepared in Example 2 during the electrochemical oxidation reaction of methanol. Figure 10 The image shows the in-situ infrared spectrum of the catalyst prepared in Example 2 during the methanol electrochemical oxidation reaction. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] Example 1 (1) Cut a 1 mm thick nickel foam into 3×3 cm sizes, and then perform ultrasonic cleaning in acetone solution, 5% hydrochloric acid solution, ethanol solution and deionized water in sequence. Each cleaning step takes 30 min to remove the surface oxide layer and impurities.

[0029] (2) Dissolve 0.5 mmol NiCl2·5H2O and 4 mmol (NH2)2CO in 30 mL of deionized water and stir magnetically for 30 min at a stirring speed of 500 rpm to form a homogeneous solution.

[0030] (3) The cleaned nickel foam and the mixed solution were transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor and hydrothermally reacted at 120 °C for 12 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The sample was taken out, washed three times with deionized water, and vacuum dried at 60 °C for 12 h to obtain the Ni5(Ⅱ)O(OH)8 catalyst grown in situ on the surface of nickel foam.

[0031] Example 2 (1) Cut a 1 mm thick nickel foam into 3×3 cm sizes, and then perform ultrasonic cleaning in acetone solution, 5% hydrochloric acid solution, ethanol solution and deionized water in sequence. Each cleaning step takes 30 min to remove the surface oxide layer and impurities.

[0032] (2) Dissolve 0.2 mmol NiCl2·5H2O, 0.3 mmol FeCl3 and 4 mmol (NH2)2CO in 30 mL of deionized water and stir magnetically for 30 min at a stirring speed of 500 rpm to form a homogeneous solution.

[0033] (3) The cleaned nickel foam and the mixed solution were transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor and hydrothermally reacted at 120 °C for 12 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The sample was taken out, washed three times with deionized water, and vacuum dried at 60 °C for 12 h to obtain the Ni5(Ⅱ)O(OH)8 / FeOOH catalyst grown in situ on the surface of nickel foam.

[0034] Example 3 The steps are basically the same as in Example 2, except that “0.2 mmol NiCl2·5H2O, 0.3 mmol FeCl3 and 4 mmol (NH2)2CO” is replaced with “0.2 mmol NiCl2·5H2O, 2 mmol FeCl3 and 8 mmol (NH2)2CO”.

[0035] Example 4 The steps are basically the same as in Example 2, except that “0.2 mmol NiCl2·5H2O, 0.3 mmol FeCl3 and 4 mmol (NH2)2CO” are replaced with “0.2 mmol Ni(NO3)2·6H2O, 1 mmol FeCl3 and 6 mmol ammonium carbonate”, and the hydrothermal reaction is carried out at 180 °C for 5 h.

[0036] Example 5 The steps are basically the same as in Example 1, except that “0.5 mmol NiCl2·5H2O and 4 mmol (NH2)2CO” is replaced with “0.5 mmol NiCl2·5H2O and 10 mmol (NH2)2CO”.

[0037] Comparative Example 1 A method for preparing a Ni(OH)₂ / FeOOH catalyst for methanol oxidation, comprising the following steps: (1) Dissolve 2.1 mmol Ni(NO3)2·6H2O, 0.7 mmol Fe(NO3)3·9H2O, 5 mmol NH4F and 10 mmol (NH2)2CO in 30 mL of deionized water and stir at 500 rpm for 30 min to form a homogeneous solution.

[0038] (2) The obtained mixed solution was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor and hydrothermally reacted at 120 °C for 12 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The sample was taken out, centrifuged at 8000 rpm for 3 min, washed with deionized water 3 times, and vacuum dried at 60 °C for 12 h to obtain a solid product.

[0039] (3) The obtained solid product was soaked in Na2S solution for 120 min and washed with deionized water 3 times. It was then vacuum dried at 60 °C for 12 h to obtain Ni(OH)2 / FeOOH catalyst.

[0040] The catalysts prepared in Examples 1 and 2 were characterized, and the results are shown in the figure. Figure 1-6 .

[0041] Depend on Figure 1 The results showed that the catalyst obtained in Example 1 exhibited characteristic diffraction peaks consistent with those of natural Ni5(II)O(OH)8 ore, thus confirming the successful synthesis of Ni5(II)O(OH)8. The catalyst obtained in Example 2 showed characteristic diffraction peaks of both the Ni5(II)O(OH)8 and FeOOH phases, with several characteristic peaks overlapping or adjacent at the same or similar 2θ positions. This indicates a lattice matching relationship between the Ni5(II)O(OH)8 and FeOOH phases.

[0042] Depend on Figure 2 The results show that the catalyst prepared in Example 1 exhibits a nanofiber morphology, while the catalyst prepared in Example 2 exhibits a nanosheet morphology.

[0043] Depend on Figure 3The results showed that Ni and O elements were uniformly distributed in the catalyst prepared in Example 1.

[0044] Depend on Figure 4 The results showed that the Ni signal in the catalyst prepared in Example 2 was mainly enriched in the outer region of the nanostructure, while the Fe signal was mainly distributed in the inner region, exhibiting obvious shell / core distribution characteristics in space, which confirmed the successful synthesis of the Ni5(Ⅱ)O(OH)8 / FeOOH shell-core structure.

[0045] Depend on Figure 5 The results showed that the lattice spacings of the two regions corresponding to the catalyst prepared in Example 2 were 0.26 nm and 0.23 nm, respectively, and belonged to the Ni5(Ⅱ)O(OH)8 and FeOOH crystal phases. A continuous and uniformly oriented lattice arrangement was observed at the interface between the inner and outer layers, thus confirming that an interface structure with a lattice-matched relationship was formed between Ni5(Ⅱ)O(OH)8 and FeOOH.

[0046] Depend on Figure 6 The results showed that the Ni(II) in the Ni5(II)O(OH)8 catalyst prepared in Example 1 exhibited characteristic peaks at 873.6 and 855.9 eV. Compared with Ni5(II)O(OH)8, the binding energy of Ni(II) in Ni5(II)O(OH)8 / FeOOH shifted positively by about 0.3 eV, indicating that its electronic structure was regulated by the heterojunction and charge redistribution occurred, showing a trend of electron transfer from Ni5(II)O(OH)8 to FeOOH.

[0047] In summary, this invention provides Ni-based catalysts and yields Ni5(II)O(OH)8 nanofiber structures and Ni5(II)O(OH)8 / FeOOH shell / core heterogeneous nanosheet structures. Specifically, Ni5(II)O(OH)8 and FeOOH form an interface structure with lattice-matched characteristics, accompanied by modulation of the interface electronic structure and charge redistribution, verifying the successful construction of the heterostructure and its structure-electronic synergistic features.

[0048] Application Example 1 To further verify the application performance of the catalysts prepared in Examples 1 and 2 in the electrochemical oxidation reaction of methanol, the nickel foam electrodes obtained in Examples 1 and 2 were placed in an H-type electrolytic cell equipped with a bipolar membrane for electrochemical performance testing. The specific steps are as follows: The nickel foams prepared in Examples 1 and 2 were fixed with electrode clamps and immersed in electrolyte as working electrodes. A saturated Ag / AgCl electrode was used as the reference electrode, and a platinum mesh with an area of ​​1×1 cm was used as the counter electrode. All electrochemical tests were performed on an electrochemical workstation.

[0049] As a control, the catalyst prepared in Comparative Example 1 was subjected to methanol electrochemical oxidation performance testing. The specific steps are as follows: 10 mg of Ni(OH)2 / FeOOH catalyst prepared in Comparative Example 1 was dispersed in 1 mL of ethanol solution, and 50 μL of Nafion was added as a binder. After ultrasonic treatment for 30 min, a uniform catalyst ink was obtained. 20 μL of catalyst ink was drop-coated onto the surface of a glassy carbon electrode, dried, and used as the working electrode. The working electrode was placed in the electrolyte, a saturated Ag / AgCl electrode was used as the reference electrode, and a platinum mesh with an area of ​​1×1 cm was used as the counter electrode. Electrochemical performance testing was performed using an electrochemical workstation.

[0050] (1) Methanol oxidation activity test The methanol oxidation performance of the catalyst was evaluated by using 1.0 M KOH solution and a mixed solution of 1.0 M KOH and 1.0 M CH3OH as electrolytes, and by performing linear scan voltammetry at a scan rate of 50 mV / s in a potential range of 1.25–1.95 V (vs. reversible hydrogen electrode).

[0051] (2) Selectivity test for methanol oxidation The system was subjected to constant potential electrolysis within a potential range of 1.35–1.80 V (vs. reversible hydrogen electrode) for 1 h. After electrolysis, the liquid phase products were quantitatively analyzed by nuclear magnetic resonance (NMR), and the Faraday efficiency of the formate was calculated according to formula (1) to evaluate the product selectivity of the catalyst for the methanol oxidation reaction.

[0052] FE=z·n·F / Q(1) Where z is the number of electrons transferred per mole of liquid product; n is the number of moles of formate produced; F is the Faraday constant; and Q is the total charge transferred in the reaction. Performance results for the electrochemical oxidation of methanol are shown in [Figure number missing]. Figure 7-8 .

[0053] Depend on Figure 7The results showed that the catalysts prepared in Examples 1-2 and Comparative Example 1 could all participate in the electrochemical oxidation reaction of methanol in a mixed electrolyte of 1.0 M KOH + 1.0 M CH3OH. Specifically, the polarization curve of the Ni(OH)2 / FeOOH catalyst prepared in Comparative Example 1 exhibited a broad and obvious oxidation characteristic peak, indicating that its components underwent significant oxidation during the reaction. This is a common component oxidation phenomenon in traditional Ni-based catalysis and is the main reason for the significant oxygen evolution reaction at high potentials. In contrast, no obvious oxidation peak was observed in the polarization curve of the Ni5(II)O(OH)8 / FeOOH catalyst prepared in Example 2, indicating that it has a more stable structural state within the corresponding potential range. The different structural stabilizations exhibited by the catalysts prepared in Comparative Example 1 and Example 2 strongly demonstrate the uniqueness of the Ni5(II)O(OH)8 phase in the electrochemical oxidation reaction of methanol. The unique crystal structure of the Ni5(Ⅱ)O(OH)8 phase endows it with significantly enhanced intrinsic antioxidant capacity after coupling with FeOOH, effectively suppressing the irreversible transformation of Ni(Ⅱ) to higher-valence Ni species such as NiOOH at the oxidation potential, thus avoiding the competitive oxygen evolution side reaction caused by the change of active phase at the source. Therefore, compared with Ni5(Ⅱ)O(OH)8 alone, Ni5(Ⅱ)O(OH)8 / FeOOH exhibits a lower current response onset potential and a higher current density at the same potential.

[0054] Figure 8 The results showed that the catalyst Ni5(II)O(OH)8 / FeOOH prepared in Example 2 maintained a high formate Faraday efficiency consistently within the potential range of 1.35-1.80 V (vs. reversible hydrogen electrode), with a value close to 100%. The superior catalytic performance exhibited by this Ni5(II)O(OH)8 / FeOOH indicates that the heterostructure interface structure formed between Ni5(II)O(OH)8 and FeOOH significantly optimizes the electronic structure of the Ni(II) active sites. Specifically, through interfacial orbital coupling and energy level modulation, directional electron transfer occurs from Ni5(II)O(OH)8 to FeOOH. This electron rearrangement process optimizes the adsorption capacity of methanol molecules on the Ni5(II)O(OH)8 surface and its activation of key reaction intermediates, thereby improving the catalytic efficiency of methanol oxidation to formate. The construction of the Ni5(II)O(OH)8 / FeOOH shell / core heterostructure achieves a synergistic effect of "structural stability" and "performance enhancement".

[0055] The above results indicate that Ni5(Ⅱ)O(OH)8 and the Ni5(Ⅱ)O(OH)8 / FeOOH shell / core heterostructure constructed with FeOOH are superior to traditional Ni-based systems in terms of catalytic performance and stability.

[0056] In addition, to further investigate the structural evolution of the catalyst prepared in Example 2 during the methanol oxidation process, in-situ Raman spectroscopy and in-situ infrared spectroscopy were performed on the catalyst, and the results are as follows: Figure 9 and Figure 10 As shown.

[0057] Depend on Figure 9 The results showed that, at open-circuit potentials, Ni5(Ⅱ)O(OH)8 / FeOOH at 212, 457, and 635 cm⁻¹ -1 A characteristic Raman peak appears at approximately 683 cm⁻¹, which is attributed to the Ni₅(Ⅱ)O(OH)₈ related vibrational mode. -1 Characteristic vibrational peaks of FeOOH were observed at [value missing], further confirming the successful construction of the heterostructure. As the potential gradually increased, the positions and intensities of its main characteristic peaks remained generally stable, indicating that the catalyst exhibits good structural stability under methanol electrochemical oxidation conditions. Furthermore, characteristic peaks related to the adsorption of methanol and formate were detected, located at 1018 / 1470 cm⁻¹, respectively. -1 and 1339 cm -1 This indicates that the catalyst can effectively adsorb reactants and intermediates during the reaction process, which is beneficial to the conversion of methanol to formate.

[0058] Depend on Figure 10 The results showed that Ni5(Ⅱ)O(OH)8 / FeOOH was at 1571, 1382, and 1350 cm⁻¹. -1 A distinct infrared absorption peak appears at [location], corresponding to the antisymmetric stretching vibration (ν) of OCO in formate. as ), CH bending vibration (δ), and OCO symmetric stretching vibration (ν) s The results indicate that the catalyst can effectively promote the formation of formate-related species under the reaction conditions. Furthermore, no obvious carbonate-related absorption peaks were observed under these test conditions, suggesting that the catalyst tends to form formate products during the electrochemical oxidation of methanol.

[0059] Based on the above in-situ Raman and infrared spectroscopy results, it can be seen that introducing FeOOH into Ni5(Ⅱ)O(OH)8 to construct a Ni5(Ⅱ)O(OH)8 / FeOOH shell / core heterostructure further improves the structural stability, reaction selectivity and overall catalytic efficiency of the catalyst.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A Ni-based catalyst, characterized in that, The Ni-based catalyst is a Ni5(Ⅱ)O(OH)8 / FeOOH catalyst with a shell / core heterogeneous nanosheet structure or a Ni5(Ⅱ)O(OH)8 catalyst with a nanofiber structure.

2. A method for preparing a Ni-based catalyst as described in claim 1, characterized in that, The Ni-based catalyst is a Ni5(Ⅱ)O(OH)8 / FeOOH catalyst with a shell / core heterogeneous nanosheet structure, comprising the following steps: S1. Pre-treat the conductive substrate; S2. Add the nickel salt precursor, iron salt precursor and alkaline regulator to deionized water, mix and stir to form a uniform mixture. S3. The pretreated conductive substrate is placed in the mixed solution and subjected to a hydrothermal reaction to form a Ni-based catalyst, namely Ni5(Ⅱ)O(OH)8 / FeOOH catalyst, which is grown in situ on the surface of the conductive substrate.

3. A method for preparing a Ni-based catalyst as described in claim 1, characterized in that, The Ni-based catalyst is a Ni5(Ⅱ)O(OH)8 catalyst with a nanofiber structure, comprising the following steps: A1. Pretreatment of the conductive substrate; A2. Add the nickel salt precursor and alkaline regulator to deionized water, mix and stir to form a homogeneous mixed solution; A3. The pretreated conductive substrate is placed in a mixed solution and subjected to a hydrothermal reaction to form a Ni-based catalyst, namely Ni5(Ⅱ)O(OH)8 catalyst, which is grown in situ on the surface of the conductive substrate.

4. The method for preparing the Ni-based catalyst according to claim 2 or 3, characterized in that, In steps S1 and A1, the conductive substrate is selected from any one of nickel foam, carbon cloth, or carbon paper; The pretreatment of the conductive substrate includes: sequentially cleaning the conductive substrate in an acidic solution, deionized water, and an organic solvent to remove the surface oxide layer and impurities; The acidic solution is one or a combination of two or more of dilute hydrochloric acid, dilute sulfuric acid, or dilute nitric acid, with a mass fraction of 1% to 10%; the organic solvent is one or a combination of two or more of acetone, ethanol, or isopropanol; the cleaning is performed using ultrasonic cleaning, with each cleaning step taking 10 to 40 minutes.

5. The method for preparing the Ni-based catalyst according to claim 2, characterized in that, In step S2, the molar ratio of the nickel salt precursor, the iron salt precursor and the alkaline regulator is 1:(0.1~10):(1~50); the iron salt precursor is selected from one or more combinations of ferric nitrate, ferric chloride or ferric sulfate.

6. The method for preparing the Ni-based catalyst according to claim 3, characterized in that, In step A2, the molar ratio of the nickel salt precursor to the alkaline regulator is 1:(1~50).

7. The method for preparing the Ni-based catalyst according to claim 2 or 3, characterized in that, In steps S2 and A2, the nickel salt precursor is selected from one or more combinations of nickel nitrate, nickel chloride, or nickel sulfate; the alkalinity regulator is selected from one or more combinations of urea, ammonium carbonate, sodium hydroxide, or potassium hydroxide.

8. The method for preparing the Ni-based catalyst according to claim 2 or 3, characterized in that, In steps S3 and A3, the temperature of the hydrothermal reaction is 100 ~ 200 ℃, and the reaction time is 4 ~ 24 h.

9. The method for preparing the Ni-based catalyst according to claim 2 or 3, characterized in that, In steps S3 and A3, after the hydrothermal reaction is completed, a post-processing step is performed, specifically: after the reaction is completed, the reaction product is taken out and washed and dried; the washing reagent is deionized water and / or ethanol; the drying is carried out under vacuum conditions of 40 ~ 80 ℃ for 6 ~ 24 h.

10. The application of the Ni-based catalyst as described in claim 1 in the electrochemical oxidation reaction of methanol.

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