Phosphate-modified Ni x Co y Preparation method of O@C cross-linked nanosheet array and application of electro-oxidized 5-hydroxymethylfurfural

Abstract

This invention discloses a phosphate-modified Ni x Co y Preparation method of O@C cross-linked nanosheet array and its application in electro-oxidation of 5-hydroxymethylfurfural: Nickel foam is immersed in a mixed solution of cobalt nitrate hexahydrate and nickel nitrate hexahydrate for hydrothermal reaction, followed by ligand adsorption reaction in sodium phytate or sodium phenylphosphonite solution. Finally, calcination is performed to obtain phosphate-modified Ni. x Co y O@C cross-linked nanosheet array catalyst. This invention induces Ni through phosphate modification and surface carbon layer coating on the catalyst surface. x Co y The O@C surface electronic structure reorganization promotes the formation of high-valence active species; simultaneously, the surface carbon layer helps regulate the adsorption characteristics of reactive species, thereby effectively suppressing OER competitive reactions. The excellent cycling stability of this catalyst, and the successful separation and purification of FDCA products, indicate that this catalyst has broad market application prospects.

Description

Technical Field

[0002] This invention belongs to the fields of biomass conversion, electrocatalysis, and green chemistry, and relates to the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) (HMFOR) to prepare 2,5-furandicarboxylic acid (FDCA), specifically involving a phosphate-modified Ni x Co y Preparation method of O@C cross-linked nanosheet array and its application in electro-oxidation of 5-hydroxymethylfurfural. Background Technology

[0004] With the rapid advancement of human civilization, the overexploitation of fossil fuels has exacerbated environmental problems, prompting people to actively explore sustainable alternative energy solutions. Among numerous resources, lignocellulose, as a widely distributed and inedible carbon resource, has seen its derived HMF platform compounds become a hot research topic in recent years due to their high value utilization. Significant progress has been made in the technical route of preparing FDCA through electrocatalytic HMF oxidation, which is highly likely to be the first to achieve industrial-scale production. FDCA possesses excellent heat resistance, good mechanical strength, and is renewable and environmentally friendly, making it an ideal substitute for terephthalic acid. It can be applied in various fields such as biodegradable plastics and unsaturated resins, with extremely broad market prospects.

[0005] In the electrocatalytic oxidation of HMF, catalyst selection is crucial. While traditional noble metal electrocatalysts exhibit excellent catalytic performance and high stability, their high cost hinders their large-scale industrial application. In recent years, transition metal catalytic systems have attracted considerable attention from researchers due to their rich catalytic diversity, superior catalytic activity, and low preparation cost. Among them, nickel-based electrocatalysts, with their strong electrooxidation capabilities, can efficiently oxidize the carboxyl and hydroxyl functional groups in HMF and have been widely used in the research of HMF electrooxidation to FDCA. However, the HMF oxidation process depends on Ni... 3+ Active species generation, while Ni 3+ The generation potential of HMFOR is usually within the potential range of the competing reaction of HMFOR, namely the oxygen evolution reaction (OER), which severely limits the activity and potential range of HMFOR and makes it difficult to meet the actual production needs. Improving the catalyst activity to improve the HMF conversion rate has become a key problem that urgently needs to be solved.

[0006] The prior art patent document CN202210017792.8 discloses a method for preparing Co-Ni-based electrocatalytic materials and their applications. The specific preparation process is as follows: terephthalic acid is dissolved in N,N-dimethylformamide to obtain a terephthalic acid solution; nickel salt is dissolved in anhydrous ethanol and deionized water to obtain a nickel salt solution; the two solutions are mixed and transferred to a reaction vessel, pretreated carbon paper is added, and the mixture is calcined in a muffle furnace, washed, and dried to obtain Ni-loaded carbon paper; cobalt salt is dissolved in deionized water, and the resulting solution is used as the electrolyte. The Ni-loaded carbon paper is used as the deposition electrode, with an Ag / AgCl electrode as the reference electrode and a graphite electrode as the counter electrode. The deposition potential is maintained at -0.8V. RHE Electrodeposition was performed for 10 min, followed by rinsing the deposited carbon paper with deionized water and drying to obtain the Co-Ni-based electrocatalytic material. The prepared Co-Ni-based electrocatalytic material exhibited high catalytic efficiency in the electrocatalytic oxidation of 5-hydroxymethylfurfural. However, this patented technology lacks information on phosphate-modified Ni. x Co y There are no reports on the electrooxidation of 5-hydroxymethylfurfural using O@C cross-linked nanosheet arrays, nor are there any reports on inducing Ni oxidation through phosphate modification and carbon layer coating on the catalyst surface. x Co y The reorganization of the electronic structure on the O@C surface promotes the formation of high-valence active species; simultaneously, the surface carbon layer helps to regulate the adsorption characteristics of reactive species, thereby effectively suppressing the OER competitive reaction. This provides a technological inspiration. Patent document CN202210516864.3 discloses a method for preparing nickel-cobalt bimetallic nitride electrocatalysts and their application in the electrooxidation of 5-hydroxymethylfurfural (HMF). The specific preparation process is as follows: first, clean the foamed nickel, then grow a cobalt metal-organic framework (CoMOF) material on it as a substrate, then etch the CoMOF with Ni to obtain a nickel-cobalt layered bimetallic hydroxide (Ni8Co2-LDH) array structure, and finally nitridate at high temperature to obtain the nickel-cobalt bimetallic nitride electrocatalyst Ni8Co2-N. The prepared Ni8Co2-N electrocatalyst exhibits excellent HMF electrooxidation performance, surpassing many NiCo-based electrocatalysts. Even after six consecutive electrolysis cycles, the catalyst structure remains intact. However, this patent technology does not mention phosphate-modified Ni. x Co y There are no reports on the electrooxidation of 5-hydroxymethylfurfural using O@C cross-linked nanosheet arrays, nor are there any reports on inducing Ni oxidation through phosphate modification and carbon layer coating on the catalyst surface. x Co y The reorganization of the electronic structure on the O@C surface promotes the formation of high-valence active species; at the same time, the surface carbon layer helps to regulate the adsorption characteristics of reactive species, thereby effectively inhibiting the OER competitive reaction.

[0007] To address the aforementioned technical problems, this invention employs phosphate modification to regulate the charge distribution around nickel and cobalt metal sites, promoting the dehydrogenation of lattice hydroxyl groups to form high-valence active species, effectively enhancing the catalyst's HMFOR activity. Furthermore, the carbonization of the sample surface after calcination helps regulate the adsorption characteristics of reactants, thereby effectively suppressing OER competition reactions and ultimately achieving higher oxidation current density and charge utilization. Based on these research findings, this invention proposes an innovative catalyst preparation method, using nickel foam as a substrate, and preparing phosphate-modified Ni through a series of processes including hydrothermal reaction, water bath heating, and calcination. x Co y O@C cross-linked nanosheet array catalysts exhibit significant OER suppression, excellent HMF conversion, high Faradaic efficiency, and superior cycling stability, enabling efficient electrocatalytic oxidation of HMF to FDCA. However, there are currently no related reports in this area. Summary of the Invention

[0009] The technical problem solved by this invention is to provide a phosphate-modified Ni x Co y Preparation method of O@C cross-linked nanosheet array and its application in the electro-oxidation of 5-hydroxymethylfurfural. This method uses nickel foam as a substrate and synthesizes phosphate-modified Ni for the efficient electrocatalytic oxidation of HMF to FDCA through hydrothermal, water bath and calcination processes. x Co y O@C cross-linked nanosheet array catalyst.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: Ni modified with phosphate. x Co y The method for preparing O@C cross-linked nanosheet arrays is characterized by the following specific preparation steps:

[0011] Step S1: Cut the nickel foam and put it into anhydrous ethanol and dilute hydrochloric acid for ultrasonic cleaning to remove organic matter and oxides attached to the surface of the nickel foam. Then, use anhydrous ethanol for ultrasonic cleaning again to obtain material A.

[0012] Step S2: Add cobalt nitrate hexahydrate and nickel nitrate hexahydrate to deionized water and stir continuously until homogeneous to obtain material B;

[0013] Step S3: Place material A obtained in step S1 and material B obtained in step S2 together in the reactor and ensure that material B completely submerges material A. Then place the reactor in a forced-air drying oven and carry out a hydrothermal reaction at 80~150℃. After the reaction is completed, material C is obtained.

[0014] Step S4: Add sodium phenylphosphonite or sodium phytate to deionized water and stir continuously until homogeneous to obtain material D1 or D2;

[0015] Step S5: Immerse the material C obtained in step S3 in the material D1 or D2 obtained in step S4, and then place it in a water bath at 30~60℃ for constant temperature stirring reaction to obtain material E1 or E2.

[0016] Step S6: Wash the material E1 or E2 obtained in step S5 with deionized water and anhydrous ethanol in sequence, and then dry it to obtain material F1 or F2.

[0017] Step S7: Place the material F1 or F2 obtained in step S6 into a tube furnace and calcine it at 300~400℃ for 1~4 hours to obtain the target product G1 or G2, i.e., phosphate-modified Ni. x Co y O@C cross-linked nanosheet array catalyst, through phosphate modification and surface carbon layer coating on the catalyst surface, induces Ni x Co y The reorganization of the electronic structure on the O@C surface promotes the formation of high-valence active species, providing abundant active sites and more material transport channels for electrocatalytic reactions. It also helps to optimize the electron delocalization of Ni in the catalyst, accelerate charge transfer, and thus improve catalytic activity. At the same time, the surface carbon layer helps to regulate the adsorption characteristics of reactive species, thereby effectively suppressing the OER competitive reaction and achieving selectivity in the electro-oxidation of HMF.

[0018] Further specifying, the thickness of the nickel foam mentioned in step S1 is 1~3mm, and the cutting size is (1~5)×(1~15)cm. 2 The nickel foam is ultrasonically cleaned in anhydrous ethanol for 15-25 minutes and in dilute hydrochloric acid for 25-40 minutes, with a molar concentration of 0.5-2.5 mol / L. -1 Finally, ultrasonic cleaning in anhydrous ethanol is performed for 10-25 minutes.

[0019] Further specifying, the molar concentration of cobalt nitrate hexahydrate or nickel nitrate hexahydrate in material B in step S2 is 50~200 mmol / L. -1 In step S4, the molar concentration of sodium phytate or sodium phenylphosphonite in material D1 or D2 is 50-200 mmol / L. -1 .

[0020] Further specifying, the hydrothermal reaction time in step S3 is 12~48h, and the isothermal stirring reaction time in step S5 is 4~9h.

[0021] Further specifying, the drying temperature in step S6 is 50~80℃, and the drying time is 1~3h.

[0022] Further specifying, the heating rate of the calcination treatment in step S7 is 3~8℃ min. -1 .

[0023] The phosphate-modified Ni of the present invention x Co y The O@C cross-linked nanosheet array was used as the working electrode to form a three-electrode system for the electrocatalytic oxidation of HMF to synthesize FDCA in an alkaline electrolyte.

[0024] Further specifying, in the three-electrode system, the platinum sheet and the Hg / HgO electrode are the counter electrode and the reference electrode, respectively; the alkaline electrolyte is a 1M KOH solution or NaOH solution; and the concentration of HMF is 10~100 mmol / L. -1 The applied potential is 1.35~1.55V, and Ni is modified with phosphate. x Co y O@C cross-linked nanosheet arrays can selectively electrocatalyze the oxidation of HMF to prepare FDCA in alkaline electrolyte.

[0025] Further, activated carbon was added to the reaction solution for preparing FDCA by electrocatalytic oxidation of HMF, and the mixture was stirred to adsorb residual impurities. After treatment with activated carbon, the reaction solution was filtered to obtain a transparent FDCA solution. The filtrate was then heated to 40-60°C and allowed to stand for 20-30 minutes. After cooling to room temperature, hydrochloric acid solution was added to adjust the pH value to 1-3, and finally high-purity FDCA was precipitated.

[0026] Further specifying, the amount of activated carbon added to the reaction solution for the electrocatalytic oxidation of HMF to prepare FDCA is 3-8 g / L.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] 1. This invention involves the preparation of phosphate-modified Ni x Co y O@C cross-linked nanosheet array catalyst enables highly efficient electrocatalytic oxidation of HMF to prepare FDCA. The carbon layer formed by catalyst calcination can regulate the charge density around nickel sites, which is conducive to the bond breaking and dehydrogenation reaction of lattice hydroxyl groups to form high-valence nickel and cobalt active species, thereby significantly improving the catalyst's catalytic activity for HMF oxidation.

[0029] 2. This invention carbonizes the sample surface through calcination, which helps to regulate the adsorption characteristics of reactants and thus effectively suppresses the OER competing reaction. The optimal catalyst at 1.47V exhibits a current density approximately 112 mA cm⁻¹ higher than OER at HMFOR.-2 This resulted in higher selectivity for the electro-oxidation of HMF.

[0030] 3. The optimal catalyst synthesized in this invention exhibits a three-dimensional cross-linked nanosheet structure, which exposes more active sites, thereby effectively improving the electrocatalytic oxidation performance of HMF. At a potential of 1.47 V, this catalyst exhibits a high flux density of 132.2 mA cm⁻¹. -2 The current density.

[0031] 4. The catalyst synthesized in this invention can be used in a flow cell for the electro-oxidation of HMF. After approximately 70 hours of cycling stability testing, it still maintains a high oxidation current density, fully demonstrating the effect of phosphate-modified Ni. x Co y The O@C cross-linked nanosheet array catalyst exhibits excellent cycling stability during the electrocatalytic oxidation of HMF to prepare FDCA.

[0032] 5. The method for purifying FDCA from the reaction solution of HMF prepared by electrocatalytic oxidation is simple to operate and easy to implement in the laboratory and industrial production. It can effectively remove residual impurities in the solution by utilizing the adsorption properties of activated carbon. By precisely controlling the heating and cooling conditions and adjusting the pH value, FDCA can be precipitated efficiently, and a high-purity product can be obtained. Moreover, the overall reaction conditions are mild, which reduces the potential damage to the product caused by harsh conditions and helps to maintain the stability of product quality. Attached Figure Description

[0034] Figure 1 The image shows a scanning electron microscope (SEM) image of product G1 prepared in Example 1.

[0035] Figure 2 The image shows a scanning electron microscope (SEM) image of product G2 prepared in Example 2.

[0036] Figure 3 The image shows the XRD pattern of product G1 prepared in Example 1.

[0037] Figure 4 The image shows a comparison of the OER and HMFOR linear sweep voltammetric curves of product G1 prepared in Example 1.

[0038] Figure 5 HMFOR linear sweep voltammetric curves of products G1~G4 prepared in Examples 1 and 2 and Comparative Examples 1 and 2.

[0039] Figure 6 HMFOR linear sweep voltammetric curves of products G5, G6 and G7 prepared for comparative examples 3, 4 and 5.

[0040] Figure 7 This is a test diagram for a continuous flow cell.

[0041] Figure 8 The it curve of product G1 prepared in Example 1 after 20 cycles of electro-oxidation of HMF.

[0042] Figure 9 A diagram showing the purified FDCA products prepared in large quantities.

[0043] Figure 10 Infrared comparison images of purified FDCA and FDCA pharmaceutical products. Detailed Implementation

[0045] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0046] Example 1

[0047] Step S1: Cut to size (2×3) cm 2 Nickel foam was ultrasonically cleaned in anhydrous ethanol for 15 min, followed by cleaning with 1 mol L... -1 The material A1 was obtained by ultrasonic cleaning with hydrochloric acid solution for 30 min and then ultrasonic cleaning with anhydrous ethanol for 15 min.

[0048] Step S2: Add cobalt nitrate hexahydrate and nickel nitrate hexahydrate to 30 mL of deionized water, and stir continuously until homogeneous to obtain material B1, wherein the concentration of both cobalt nitrate hexahydrate and nickel nitrate hexahydrate is 50 mmol / L. -1 ;

[0049] Step S3: Place material A1 and material B1 in a 50mL reaction vessel, ensuring that material B1 completely submerges material A1, and then place it in a forced-air drying oven to react at 95℃ for 12h to obtain material C1;

[0050] Step S4: Add sodium phenylphosphonite to 30 mL of deionized water and stir continuously until homogeneous to obtain material D1, wherein the concentration of sodium phenylphosphonite is 50 mmol / L. -1 ;

[0051] Step S5: Wash material C1 repeatedly with deionized water and anhydrous ethanol, then immerse material C1 in material D1, and then put it in a water bath and react at 50°C for 6 hours to obtain material E1.

[0052] Step S6: Wash material E1 repeatedly with deionized water and anhydrous ethanol, and then dry it in a 60℃ forced-air drying oven for 3 hours to obtain material F1;

[0053] Step S7: Place material F1 in a tube furnace and heat at 5°C for 5 min.-1 The product G1 was obtained by heating the product at a rate of 300℃ for 1 hour.

[0054] Example 2

[0055] Step S1: Cut to size (2×3) cm 2 Nickel foam was ultrasonically cleaned in anhydrous ethanol for 15 min, followed by cleaning with 1 mol L... -1 The material A2 was obtained by ultrasonic cleaning with hydrochloric acid for 30 minutes and then ultrasonic cleaning with anhydrous ethanol for 15 minutes.

[0056] Step S2: Add cobalt nitrate hexahydrate and nickel nitrate hexahydrate to 30 mL of deionized water, and stir continuously until homogeneous to obtain material B2, wherein the concentration of both cobalt nitrate hexahydrate and nickel nitrate hexahydrate is 50 mmol / L. -1 ;

[0057] Step S3: Place material A2 and material B2 in a 50mL reaction vessel, ensuring that material B2 completely submerges material A2, and then place it in a forced-air drying oven to react at 95℃ for 12h to obtain material C2;

[0058] Step S4: Add sodium phytate to 30 mL of deionized water and stir continuously until homogeneous to obtain material D2, wherein the concentration of sodium phytate is 50 mmol / L. -1 ;

[0059] Step S5: Wash material C2 repeatedly with deionized water and anhydrous ethanol, then immerse material C2 in material D2, and then put it in a water bath and react at 50°C for 6 hours to obtain material E2.

[0060] Step S6: Wash material E2 repeatedly with deionized water and anhydrous ethanol, and then dry it in a 60℃ forced-air drying oven for 3 hours to obtain product F2;

[0061] Step S7: Place material F2 in a tube furnace and heat at 5°C for 5 minutes. -1 The product G2 was obtained by heating the product at a rate of 300℃ for 1 hour.

[0062] Comparative Example 1

[0063] Step S1: Cut to size (2×3) cm 2 Nickel foam was ultrasonically cleaned in anhydrous ethanol for 15 min, followed by cleaning with 1 mol L... -1 The material A3 was obtained by ultrasonic cleaning with hydrochloric acid for 30 minutes and then ultrasonic cleaning with anhydrous ethanol for 15 minutes.

[0064] Step S2: Add nickel nitrate hexahydrate to 30 mL of deionized water and stir continuously until homogeneous to obtain material B3, wherein the concentration of nickel nitrate hexahydrate is 50 mmol / L.-1 ;

[0065] Step S3: Place material A3 and material B3 in a 50mL reaction vessel, ensuring that material B3 completely submerges material A3, and then place it in a forced-air drying oven to react at 95℃ for 12h to obtain material C3;

[0066] Step S4: Add sodium phytate to 30 mL of deionized water and stir continuously until homogeneous to obtain material D3, wherein the concentration of sodium phytate is 50 mmol / L. -1 ;

[0067] Step S5: Wash material C3 repeatedly with deionized water and anhydrous ethanol, then immerse material C3 in material D3, and then put it in a water bath and react at 50°C for 6 hours to obtain material E3.

[0068] Step S6: Wash material E3 repeatedly with deionized water and anhydrous ethanol, and then dry it in a 60℃ forced-air drying oven for 3 hours to obtain material F3;

[0069] Step S7: Place material F3 in a tube furnace and heat at 5°C for 5 minutes. -1 The product G3 was obtained by heating the product at a rate of 300℃ for 1 hour.

[0070] Comparative Example 2

[0071] Step S1: Cut to size (2×3) cm 2 Nickel foam was ultrasonically cleaned in anhydrous ethanol for 15 min, followed by cleaning with 1 mol L... -1 The material A4 was obtained by ultrasonic cleaning with hydrochloric acid for 30 minutes and then ultrasonic cleaning with anhydrous ethanol for 15 minutes.

[0072] Step S2: Add cobalt nitrate hexahydrate to 30 mL of deionized water and stir continuously until homogeneous to obtain material B4, wherein the concentration of cobalt nitrate hexahydrate is 50 mmol / L. -1 ;

[0073] Step S3: Place material A4 and material B4 in a 50mL reaction vessel, ensuring that material B3 completely submerges material A3, and then place it in a forced-air drying oven to react at 95℃ for 12h to obtain material C4;

[0074] Step S4: Add sodium phytate to 30 mL of deionized water and stir continuously until homogeneous to obtain material D4, wherein the concentration of sodium phytate is 50 mmol / L. -1 ;

[0075] Step S5: Wash material C4 repeatedly with deionized water and anhydrous ethanol, then immerse material C4 in material D4, and then put it in a water bath and react at 50°C for 6 hours to obtain material E4.

[0076] Step S6: Wash material E4 repeatedly with deionized water and anhydrous ethanol, and then dry it in a 60℃ forced-air drying oven for 3 hours to obtain product F4.

[0077] Step S7: Place material F4 in a tube furnace and heat at 5°C for 5 min. -1 The product G4 was obtained by heating the product at a rate of 300℃ for 1 hour.

[0078] Comparative Example 3

[0079] Step S1: Cut to size (2×3) cm 2 Nickel foam was ultrasonically cleaned in anhydrous ethanol for 15 min, followed by cleaning with 1 mol L... -1 The material A5 was obtained by ultrasonic cleaning with hydrochloric acid for 30 minutes and then ultrasonic cleaning with anhydrous ethanol for 15 minutes.

[0080] Step S2: Add cobalt nitrate hexahydrate and nickel nitrate hexahydrate to 30 mL of deionized water, and stir continuously until homogeneous to obtain material B5, wherein the concentration of both cobalt nitrate hexahydrate and nickel nitrate hexahydrate is 50 mmol / L. -1 ;

[0081] Step S3: Place material A5 and material B5 in a 50mL reaction vessel, ensuring that material B5 completely submerges material A5, and then place it in a forced-air drying oven to react at 95℃ for 12h to obtain material C5;

[0082] Step S4: Add sodium phytate to 30 mL of deionized water and stir continuously until homogeneous to obtain material D5, wherein the concentration of sodium phytate is 50 mmol / L. -1 ;

[0083] Step S5: Wash material C5 repeatedly with deionized water and anhydrous ethanol, then immerse material C5 in material D5, and then put it in a water bath and react at 50°C for 6 hours to obtain material E5.

[0084] Step S6: Wash material E5 repeatedly with deionized water and anhydrous ethanol, and then dry it in a 60℃ forced-air drying oven for 3 hours to obtain product G5.

[0085] Comparative Example 4

[0086] Step S1: Cut to size (2×3) cm 2 Nickel foam was ultrasonically cleaned in anhydrous ethanol for 15 min, followed by cleaning with 1 mol L... -1 The material A6 was obtained by ultrasonic cleaning with hydrochloric acid for 30 minutes and then ultrasonic cleaning with anhydrous ethanol for 15 minutes.

[0087] Step S2: Add nickel nitrate hexahydrate to 30 mL of deionized water and stir continuously until homogeneous to obtain material B6, wherein the concentration of nickel nitrate hexahydrate is 50 mmol / L. -1 ;

[0088] Step S3: Place material A6 and material B6 in a 50mL reaction vessel, ensuring that material B6 completely submerges material A6, and then place it in a forced-air drying oven to react at 95℃ for 12h to obtain material C6;

[0089] Step S4: Add sodium phytate to 30 mL of deionized water and stir continuously until homogeneous to obtain material D6, wherein the concentration of sodium phytate is 50 mmol / L. -1 ;

[0090] Step S5: Wash material C6 repeatedly with deionized water and anhydrous ethanol, then immerse material C6 in material D6, and then put it in a water bath and react at 50°C for 6 hours to obtain material E6.

[0091] Step S6: Wash material E6 repeatedly with deionized water and anhydrous ethanol, and then dry it in a 60℃ forced-air drying oven for 3 hours to obtain material G6.

[0092] Comparative Example 5

[0093] Step S1: Cut to size (2×3) cm 2 Nickel foam was ultrasonically cleaned in anhydrous ethanol for 15 min, followed by cleaning with 1 mol L... -1 The material A7 was obtained by ultrasonic cleaning with hydrochloric acid for 30 minutes and then ultrasonic cleaning with anhydrous ethanol for 15 minutes.

[0094] Step S2: Add cobalt nitrate hexahydrate to 30 mL of deionized water and stir continuously until homogeneous to obtain material B7, wherein the concentration of cobalt nitrate hexahydrate is 50 mmol / L. -1 ;

[0095] Step S3: Place material A7 and material B7 in a 50mL reaction vessel, ensuring that material B7 completely submerges material A7, and then place it in a forced-air drying oven to react at 95℃ for 12h to obtain material C7;

[0096] Step S4: Add sodium phytate to 30 mL of deionized water and stir continuously until homogeneous to obtain material D7, wherein the concentration of sodium phytate is 50 mmol / L. -1 ;

[0097] Step S5: Wash material C7 repeatedly with deionized water and anhydrous ethanol, then immerse material C7 in material D7, and then put it in a water bath and react at 50°C for 6 hours to obtain material E7.

[0098] Step S6: Wash material E7 repeatedly with deionized water and anhydrous ethanol, and then dry it in a 60℃ forced-air drying oven for 3 hours to obtain product G7.

[0099] Electrocatalytic oxidation of HMF performance test:

[0100] Electrochemical performance was tested using a traditional three-electrode system. The target product G1 was cut into pieces of (1×1.5) cm. 2 It is then fixed with electrode clips to make its effective area (1×1) cm. 2 The electrode was used as the working electrode. Hg / HgO and a platinum sheet were used as the reference electrode and counter electrode, respectively. An H-type electrolytic cell with a DuPont proton exchange membrane (Nafion-117) was used, and the electrolyte was 1 mol / L. -1 KOH solution. During the test, 30 mL of KOH solution was added to both the cathode and anode chambers, with an additional 10 mmol / L KOH solution added to the anode chamber. -1 HMF. The scan rate for measuring the polarization curve was 5 mV / s. -1 The scanning range was 1.0~1.7V. Products G2, G3, G4, G5, G6 and G7 were tested using the same method.

[0101] Continuous flow cell electro-oxidation performance test of HMF:

[0102] Assembling the flow cell: First, place the PTFE gasket and fluororubber gasket on the end plate. Cut the target product G1 catalyst according to the area of ​​the serpentine reflux channel and assemble it on the anode working module, ensuring it fits firmly against the serpentine reflux channel. Cut the pre-prepared RuFe-based hydrogen evolution catalyst according to the area of ​​the serpentine reflux channel and assemble it on the cathode working module, ensuring it fits firmly against the serpentine reflux channel. Then, separate the cathode and anode chambers with an 80μm thick AEM membrane, closing and assembling the flow cell. The fluid transfer device uses a peristaltic pump with easily adjustable flow rate, which can be adjusted by setting parameters. To ensure sufficient contact between the liquid flow cell and the catalyst surface, the liquid enters from the flow hole on the lower side of the flow cell body and flows out from the higher side. The peristaltic pump draws liquid from the storage tank and transports it to the flow cell body. Finally, connect the flow cell body to the electrochemical workstation.

[0103] Specifically, the target product G1 is cut into (2.3 × 2.3) cm pieces. 2 As the working electrode, the RuFe-based hydrogen evolution catalyst was cut into (2.3 × 2.3) cm pieces. 2 The electrode is used as the counter electrode. A flow cell with an AEM membrane is used, and the electrolyte is 1 mol / L. -1 KOH solution. During the test, 30 mL of KOH solution was added to both the cathode and anode chambers, with an additional 100 mmol / L KOH solution added to the anode chamber. -1HMF was used as the external fluid transfer device, employing a peristaltic pump with easily adjustable flow rate, a fixed voltage of 2V, and a fixed rotation speed of 50rpm. Activated carbon (5g / L) was added to the reaction solution for the electrocatalytic oxidation of HMF to prepare FDCA, and the mixture was stirred to adsorb residual impurities. After activated carbon treatment, the reaction solution was filtered to obtain a transparent FDCA solution. The filtrate was then heated to 40-60℃ and allowed to stand for 20-30 minutes, then cooled to room temperature, and hydrochloric acid solution was added to adjust the pH to 1-3, ultimately precipitating high-purity FDCA.

[0104] The performance characterization of the products obtained in the examples and comparative examples is as follows:

[0105] Figure 1 This is a scanning electron microscope image of product G1 obtained in Example 1. Figure 2 The image shows a scanning electron microscope (SEM) image of product G2 obtained in Example 2. As can be seen from the image, products G1 and G2 exhibit a cross-linked nanosheet array structure. This structure is beneficial for increasing the contact area with HMF, thereby improving the HMFOR performance. Figure 3 The image shows the XRD pattern of product G1 obtained in Example 1, which proves that NiO phase is generated in product G1. Since Co element is introduced during the preparation process, it can be inferred that G1 is mainly a Co-doped NiO phase. Figure 4 This is a comparison of the HMFOR and OER polarization curves of product G1 obtained in Example 1. The figure shows that the HMFOR process of product G1 has a larger current density; at a potential of 1.47V, the current density of HMFOR is approximately 112 mA cm⁻¹ higher than that of OER. -2 This indicates that product G1 is more inclined to preferentially oxidize HMF and effectively inhibits the OER competing reaction. Figure 5 The HMFOR polarization curves of products G1 to G4 obtained in Examples 1-2 and Comparative Examples 1-2 are shown. It was found that products G1, G2 and G3 all have high current densities, indicating that phosphate modification helps to improve the electro-oxidation activity of the catalyst for HMF. Figure 6 The HMFOR polarization curves of products G5-G7 obtained in Comparative Examples 3-5 were obtained. It was found that products G5 and G6 both had very high current densities, indicating that phosphate ligand modification also helps to improve HMF oxidation activity. Figure 7 This is a test diagram for a continuous flow cell. Figure 8 The it curve of product G1 after 20 cycles of electro-oxidation of HMF is shown. Even after approximately 70 hours of cycling stability testing, it maintained a high oxidation current density, fully demonstrating the effectiveness of phosphate-modified Ni. x Co y The O@C cross-linked nanosheet array catalyst exhibits excellent cycling stability during the electrocatalytic oxidation of HMF to prepare FDCA. Figure 9 This demonstrates the phosphate-modified Ni x Co y7.5 g of FDCA was prepared using O@C cross-linked nanosheet array catalyst. Figure 10 The infrared comparison images of the product FDCA and the FDCA reagent demonstrate that the FDCA obtained by this experimental treatment method has high purity and no extra impurity peaks.

[0106] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. Phosphate-modified Ni x Co y The method for preparing O@C cross-linked nanosheet arrays is characterized by: The specific preparation steps are as follows: Step S1: Cut the nickel foam and put it into anhydrous ethanol and dilute hydrochloric acid for ultrasonic cleaning to remove organic matter and oxides attached to the surface of the nickel foam. Then, use anhydrous ethanol for ultrasonic cleaning again to obtain material A. Step S2: Add cobalt nitrate hexahydrate and nickel nitrate hexahydrate to deionized water and stir continuously until homogeneous to obtain material B; Step S3: Place material A obtained in step S1 and material B obtained in step S2 together in the reactor and ensure that material B completely submerges material A. Then place the reactor in a forced-air drying oven and carry out a hydrothermal reaction at 80~150℃. After the reaction is completed, material C is obtained. Step S4: Add sodium phenylphosphonite or sodium phytate to deionized water and stir continuously until homogeneous to obtain material D1 or D2; Step S5: Immerse the material C obtained in step S3 in the material D1 or D2 obtained in step S4, and then place it in a water bath at 30~60℃ for constant temperature stirring reaction to obtain material E1 or E2. Step S6: Wash the material E1 or E2 obtained in step S5 with deionized water and anhydrous ethanol in sequence, and then dry it to obtain material F1 or F2. Step S7: Place the material F1 or F2 obtained in step S6 into a tube furnace and calcine it at 300~400℃ for 1~4 hours to obtain the target product G1 or G2, i.e., phosphate-modified Ni. x Co y O@C cross-linked nanosheet array catalyst, through phosphate modification and surface carbon layer coating on the catalyst surface, induces Ni x Co y The reorganization of the electronic structure on the O@C surface promotes the formation of high-valence active species, providing abundant active sites and more material transport channels for electrocatalytic reactions. It also helps to optimize the electron delocalization of Ni in the catalyst, accelerate charge transfer, and thus improve catalytic activity. At the same time, the surface carbon layer helps to regulate the adsorption characteristics of reactive species, thereby effectively suppressing the OER competitive reaction and achieving selectivity in the electro-oxidation of HMF.

2. The phosphate-modified Ni according to claim 1 x Co y The method for preparing O@C cross-linked nanosheet arrays is characterized by: The thickness of the nickel foam mentioned in step S1 is 1~3mm, and the cutting size is (1~5)×(1~15)cm. 2 The nickel foam is ultrasonically cleaned in anhydrous ethanol for 15-25 minutes and in dilute hydrochloric acid for 25-40 minutes, with a molar concentration of 0.5-2.5 mol / L. -1 Finally, ultrasonic cleaning in anhydrous ethanol is performed for 10-25 minutes.

3. The phosphate-modified Ni according to claim 1 x Co y The method for preparing O@C cross-linked nanosheet arrays is characterized by: In step S2, the molar concentration of cobalt nitrate hexahydrate or nickel nitrate hexahydrate in material B is 50-200 mmol / L. -1 In step S4, the molar concentration of sodium phytate or sodium phenylphosphonite in material D1 or D2 is 50-200 mmol / L. -1 .

4. The phosphate-modified Ni according to claim 1 x Co y The method for preparing O@C cross-linked nanosheet arrays is characterized by: The hydrothermal reaction time in step S3 is 12~48h, and the constant temperature stirring reaction time in step S5 is 4~9h.

5. The phosphate-modified Ni according to claim 1 x Co y The method for preparing O@C cross-linked nanosheet arrays is characterized by: The drying temperature in step S6 is 50~80℃, and the drying time is 1~3h.

6. The phosphate-modified Ni according to claim 1 x Co y The method for preparing O@C cross-linked nanosheet arrays is characterized by: The heating rate of the calcination treatment in step S7 is 3~8℃ / min. -1 .

7. Phosphate-modified Ni prepared by the method according to any one of claims 1 to 6 x Co y The O@C cross-linked nanosheet array was used as the working electrode to form a three-electrode system for the electrocatalytic oxidation of HMF to synthesize FDCA in an alkaline electrolyte.

8. The application according to claim 7, characterized in that: In the three-electrode system, the platinum sheet and the Hg / HgO electrode are the counter electrode and reference electrode, respectively. The alkaline electrolyte is a 1M KOH solution or NaOH solution, and the concentration of HMF is 10~100 mmol / L. -1 The applied potential is 1.35~1.55V, and Ni is modified with phosphate. x Co y O@C cross-linked nanosheet arrays can selectively electrocatalyze the oxidation of HMF to prepare FDCA in alkaline electrolyte.

9. The application according to claim 8, characterized in that: Activated carbon was added to the reaction solution for preparing FDCA by electrocatalytic oxidation of HMF, and the mixture was stirred to adsorb residual impurities. After treatment with activated carbon, the reaction solution was filtered to obtain a transparent FDCA solution. The filtrate was then heated to 40-60℃ and allowed to stand for 20-30 minutes. After cooling to room temperature, hydrochloric acid solution was added to adjust the pH value to 1-3, and finally high-purity FDCA was precipitated.

10. The application according to claim 9, characterized in that: The amount of activated carbon added to the reaction solution for the electrocatalytic oxidation of HMF to prepare FDCA is 3-8 g / L.

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