Preparation of anode catalyst and method for electrocatalytic high-selectivity preparation of glycolate from glycol

Abstract

This invention relates to the preparation of an anode catalyst and a method for the highly selective electrocatalytic preparation of glycolates from ethylene glycol. The main challenge is addressing the low selectivity and insufficient conversion rates in current ethylene glycol electrocatalytic oxidation reactions. This invention employs a three-step method—hydrothermal-hydrogen annealing-impregnation—to prepare a Pd-NiCrO2 catalyst. The Pd-NiCrO2 catalyst exhibits strong activity, high selectivity, and good stability in the electrocatalytic oxidation of ethylene glycol, achieving a conversion rate of 100 mA / cm². 2 At the current density, the operating voltage is only 0.70 V; in addition, the chronocurrent stability of this anode catalyst can be maintained at more than 80% under different voltages, and the chronocurrent stability at 1.0 V can reach more than 91%.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic small molecule oxidation, specifically to the preparation of anolyte catalysts and a method for the highly selective electrocatalytic preparation of glycolates from ethylene glycol. Background Technology

[0002] Ethylene glycol (EG) is an important chemical raw material. Its selective oxidation can produce a variety of high-value-added chemicals, among which glycolic acid (GA), as a monomer for the biodegradable material polyglycolic acid (PGA), is experiencing increasing market demand. Traditional industrial production routes for glycolic acid use chloroacetic acid as a raw material, which suffers from problems such as highly toxic and corrosive raw materials and significant environmental pressure. In recent years, electrocatalytic ethylene glycol oxidation (EGOR) technology has become a research hotspot for the upgrading and conversion of ethylene glycol and the resource utilization of waste PET plastics due to its advantages such as mild reaction conditions, a green and controllable process, and the ability to utilize renewable electricity.

[0003] In the electrocatalytic oxidation of ethylene glycol, the catalyst is crucial for achieving high selectivity and activity. Noble metal palladium (Pd)-based catalysts are widely used for the selective oxidation of ethylene glycol to glycolic acid due to their moderate C–C bond breaking ability. However, existing Pd-based catalysts still face the following key technological bottlenecks: (1) Insufficient selectivity, prone to excessive oxidation Ethylene glycol molecules have a symmetrical dihydroxyl structure, making them highly susceptible to C-C bond breakage or deep oxidation during oxidation, generating byproducts such as formic acid and oxalic acid. This hinders the improvement of selectivity for the target product, glycolic acid. Precisely controlling the adsorption strength of reaction intermediates on the catalyst surface and inhibiting C-C bond breakage is crucial for achieving highly selective conversion.

[0004] (2) The preparation method has structural defects. For example, the composite catalyst with publication number CN 117448880 A (such as Pd / Co) x Cr O2 / nickel foam typically employs a preparation sequence of "first loading palladium, then air calcining". This process has the following problems: ① High-temperature air calcination causes the formation of an inert Ni2O3 layer on the surface of the nickel foam substrate, reducing the substrate's conductivity; ② During air calcination, the loaded palladium is partially oxidized to PdO. x This leads to uncontrollable chemical states of the active centers; ③ The support metal (such as Co and Cr) exhibits a high valence state in an oxidizing atmosphere, resulting in a weak electronic cooperation effect with Pd, which is unfavorable for the selective oxidation of ethylene glycol. In addition, existing methods mostly employ organic solvothermal systems and use organometallic precursors such as acetylacetonate, which are costly and not environmentally friendly enough. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for preparing an anode catalyst and for electrocatalyzing the highly selective preparation of glycolate from ethylene glycol, mainly addressing the problems of low selectivity and insufficient conversion rate in the current electrocatalytic oxidation reaction of ethylene glycol.

[0006] The technical solution of the present invention is as follows: The preparation method of the anode catalyst includes the following steps: Step 1, hydrothermal reaction: The pretreated nickel foam is placed in an aqueous solution containing nickel source, chromium source, ammonium fluoride and urea to carry out a hydrothermal reaction to obtain a nickel foam precursor loaded with nickel-chromium hydroxide; Step 2, Annealing: The nickel foam precursor obtained in Step 1 is annealed in an Ar / H2 mixed atmosphere to obtain nickel foam loaded with NiCrO2. Step 3, Impregnation: The nickel foam loaded with NiCrO2 obtained in Step 2 is impregnated in a palladium chloride solution, removed and dried to obtain the anode catalyst.

[0007] The catalyst is based on nickel foam, on which metal oxide nanoparticles are loaded; the nickel foam is coated with palladium nanosheets.

[0008] The nickel source is one or more of nickel nitrate hexahydrate, nickel chloride, and nickel sulfate; the chromium source is one or more of chromium acetate, chromium sulfate, chromium nitrate, and chromium acetylacetone; the molar ratio of the nickel source to the chromium source is 9:1, and the molar ratio of the metal ions, ammonium fluoride, and urea is 2:3:6.

[0009] The pretreatment mentioned in step one involves placing the nickel foam in hydrochloric acid solution, ethanol, and deionized water in sequence for pretreatment, and then drying it at room temperature.

[0010] In the hydrothermal reaction of step one, the hydrothermal temperature is 100~200℃ and the hydrothermal time is 6 hours.

[0011] In the annealing process of step two, the annealing temperature is 300~500℃, the atmosphere is Ar / H2, and the annealing time is 2 hours.

[0012] The volume of palladium chloride solution used was 1 ml / cm. 2 The solution concentration was 1.2 mg / ml, the immersion time was 12 hours, and the immersion process should be kept away from light.

[0013] A method for the highly selective electrocatalytic preparation of glycolate from ethylene glycol involves a three-electrode system consisting of a reference electrode, a counter electrode, and a working electrode. An alkaline solution containing ethylene glycol is used as the electrolyte. An anode catalyst prepared by the above-described anode catalyst preparation method is used as the working electrode. A voltage is applied using an electrochemical workstation to catalyze the electrocatalytic conversion of ethylene glycol in the anode into glycolate. The reference electrode is an Hg / HgO electrode or an Ag / AgCl electrode; the counter electrode is a platinum sheet, platinum wire, or carbon rod.

[0014] The electrolyte is 1-3 mol / L potassium hydroxide or sodium hydroxide and 1-3 mol / L ethylene glycol. The beneficial effects of this invention are: 1) This invention employs a three-step method of "hydrothermal-hydrogen annealing-impregnation" to prepare a Pd-NiCrO2 catalyst. The Pd-NiCrO2 catalyst exhibits strong activity, high selectivity, and good stability in the electrocatalytic oxidation of ethylene glycol, reaching a maximum efficiency of 100 mA / cm². 2 At the current density, the operating voltage is only 0.70 V; in addition, the chronocurrent stability of this anode catalyst can be maintained at more than 80% under different voltages, and the chronocurrent stability at 1.0 V can reach more than 91%.

[0015] 2) The electrocatalytic process for preparing glycolic acid from ethylene glycol provided by this invention has the advantages of simple process, readily available raw materials, and mild reaction conditions. In particular, this technology can be directly applied to the upgrading and recycling of waste PET plastics: through the closed-loop path of "depolymerization-electrocatalytic conversion", the difficult-to-degrade plastic waste is efficiently converted into high-value-added glycolic acid products, which not only solves the environmental problem of white pollution, but also realizes the recycling of resources and value enhancement, providing an innovative solution that is both economical and environmentally friendly for the green transformation of the chemical industry. Attached Figure Description

[0016] Figure 1 The experimental procedure for Example 1 is as follows.

[0017] Figure 2 The image shows the X-ray diffraction pattern of the anolyte catalyst Pd-NiCrO2 prepared in Example 1.

[0018] Figure 3 This is a scanning electron microscope image of the anolyte catalyst Pd-NiCrO2 prepared in Example 1.

[0019] Figure 4 The blank nickel foam anolyte catalyst prepared in Example 1, Ni 1-X Cr X Physical images of (OH)2, NiCrO2, and Pd-NiCrO2.

[0020] Figure 5 Linear sweep voltammetric curves of the electrocatalytic oxidation of ethylene glycol and electrolysis of water by the anolyte catalyst Pd-NiCrO2 in the performance test example.

[0021] Figure 6For the performance test examples, the anode catalysts are NiCrO2, Pd-NiCrO2, and Pd-Ni 1-X Cr X Linear sweep voltammetric curves of electrocatalytic ethylene glycol oxidation by (OH)2 and Pd-NF.

[0022] Figure 7 Linear sweep voltammetric curves of the electrocatalytic oxidation of ethylene glycol by the anode catalysts Pd-NiCrO2, Pd-NiO, and Pd-CrO in the performance test examples.

[0023] Figure 8 Linear sweep voltammetric curves of the electrocatalytic oxidation of ethylene glycol using the anolyte catalysts Pd-NiCrO2, Pd-NiCrO2-HT100, and Pd-NiCrO2-HT200 in the performance test examples.

[0024] Figure 9 Linear sweep voltammetric curves of the electrocatalytic oxidation of ethylene glycol by the anode catalysts Pd-NiCrO2, Pd-NiCrO2-CT300, and Pd-NiCrO2-CT500 in the performance test examples.

[0025] Figure 10 This is a stability test diagram of the anode catalyst Pd-NiCrO2 in the performance test example.

[0026] Figure 11 The image shows the 1H NMR spectrum of the electrocatalytic products of the anolyte catalyst Pd-NiCrO2 in the application example. Detailed Implementation

[0027] The invention will be further described below with reference to the accompanying drawings. Example 1: Preparation of Pd-NiCrO2 anode catalyst a. Cut nickel foam into 2 cm × 3 cm pieces, and ultrasonically clean them sequentially with hydrochloric acid, ethanol, and distilled water, 10 minutes each time, for a total of 30 minutes. After cleaning, place them in a vacuum oven at 60°C to dry for later use.

[0028] b. Add 3.6 mmol of Ni(NO3)2·6H2O to 30 ml of deionized water. 0.4 mmol (CH3CO2)3Cr, 12 mmol urea, and 6 mmol NH4F were mixed and stirred for 30 minutes until completely dissolved to obtain a transparent solution. The solution was then transferred to a 100 ml high-pressure reactor, and the cleaned nickel foam was placed inside. The reactor was then transferred to an oven and heated to 150°C for 6 hours. After the reaction was completed, the reactor was cooled to room temperature, and the high-pressure reactor was removed. The precursors were then cleaned and dried for later use. c. Subsequently, the precursor was placed in a tube furnace and annealed under an Ar / H2 atmosphere, heated to 400°C at 5°C per minute and held for 2 h. After the reaction was completed, a catalyst NiCrO2 loaded with spherical metal oxide particles was obtained, which was then washed and set aside for later use.

[0029] d. Cut the NiCrO2 catalyst into 1 cm × 1.5 cm pieces. Place the 1 cm × 1.5 cm pieces of foamed metal into a reagent bottle, and then use a pipette to add 1.5 ml of a 1.2 mg / ml palladium chloride solution, ensuring the sample is completely submerged in the solution. Screw the cap on the bottle. Store at room temperature in the dark for 8 hours. After impregnation, wash several times with deionized water, then rinse twice with ethanol. Finally, dry in a vacuum drying oven at 60℃ for 6 hours to obtain the Pd-NiCrO2 catalyst, in which the mass density of palladium is 1.2 mg / cm³. 2 about.

[0030] The obtained Pd-NiCrO2 was structurally characterized as follows: Figures 2-3 .

[0031] Figure 2 XRD analysis showed that the prepared material contained elemental palladium and NiO-CrO, indicating that Pd-NiCrO2 was successfully prepared.

[0032] Figure 3 The SEM images show that NiCrO2 is dispersed in the form of spherical particles on the nickel foam, and the loaded palladium metal is coated on the nickel foam in layers.

[0033] Figure 4 The images show a comparison of the catalyst Pd-NiCrO2, the catalyst NiCrO2, the precursor, and blank nickel foam. The blank nickel foam exhibits a light gray metallic luster. The precursor, loaded with Ni(OH)2 and Cr(OH)3, is light green. NiCrO2, after annealing in an Ar / H2 atmosphere, has its original light green Ni(OH)2 and Cr(OH)3 reduced and decomposed into NiO and CrO, resulting in a light black color. In contrast, Pd-NiCrO2, which has been impregnated with palladium, is dark black, further indicating the successful synthesis of the catalyst.

[0034] Comparative Example 1: Preparation of NiCrO2 Anode Catalyst a. Cut nickel foam into 2 cm × 3 cm pieces and ultrasonically clean them sequentially with hydrochloric acid, ethanol, and distilled water. Each cleaning session lasts 10 minutes, for a total of 30 minutes. After cleaning, place them in a vacuum oven and dry at 60°C for later use.

[0035] b. Add 3.6 mmol Ni(NO3)2·6H2O to 30 ml of deionized water. 0.4 mmol (CH3CO2)3Cr, 12 mmol urea, and 6 mmol NH4F were mixed and stirred for 30 minutes until completely dissolved to obtain a transparent solution. The solution was then transferred to a 100 ml high-pressure reactor, and the cleaned nickel foam was placed inside. The reactor was then transferred to an oven and heated to 150°C for 6 hours. After the reaction was completed, the reactor was cooled to room temperature, and the high-pressure reactor was removed to obtain the catalyst precursor. The precursor was cleaned and dried for later use. c. Subsequently, the precursor was cut into 1 cm × 1.5 cm sizes, placed in a tube furnace and annealed under an Ar / H2 atmosphere. It was heated to 400°C at 5°C per minute and held for 2 h. After the reaction was completed, foam metal loaded with spherical NiCrO2 particles was obtained. After cleaning, the catalyst NiCrO2 was obtained.

[0036] Comparative Example 2: Preparation of Pd-NF Anode Catalyst This embodiment provides a method for preparing a Pd-NF electrode (compared to Example 1, the variable is the removal of the hydrothermal portion), as detailed below: a. Cut nickel foam (NF) to a size of 1 cm × 1.5 cm, and ultrasonically clean it sequentially with hydrochloric acid, ethanol, and distilled water. Each cleaning session lasts 10 minutes, for a total of 30 minutes. After cleaning, place it in a vacuum oven and dry at 60°C for later use.

[0037] b. Place the prepared 1 cm × 1.5 cm nickel foam into a reagent bottle, then use a pipette to add 1.5 ml of a 1.2 mg / ml palladium chloride solution, ensuring the sample is completely submerged in the solution. Tighten the cap. Store at room temperature in the dark for 8 hours. After impregnation, wash several times with deionized water, then rinse twice with ethanol. Finally, dry in a vacuum oven at 60°C for 6 hours to obtain the catalyst Pd-NF, where the palladium mass density is 1.2 mg / cm³. 2 about.

[0038] Comparative Example 3: Pd-Ni Anode Catalyst 1-X Cr X Preparation of (OH)2 This comparative example provides an anode catalyst Pd-Ni 1-X Cr X The preparation of (OH)2 (compared to Example 1, the variable is the hydrogen removal annealing process) is as follows: a. Cut nickel foam into 2 cm × 3 cm pieces and ultrasonically clean them sequentially with hydrochloric acid, ethanol, and distilled water. Each cleaning session lasts 10 minutes, for a total of 30 minutes. After cleaning, place them in a vacuum oven and dry at 60°C for later use.

[0039] b. Add 3.6 mmol Ni(NO3)2·6H2O to 30 ml of deionized water. 0.4 mmol (CH3CO2)3Cr, 12 mmol urea, and 6 mmol NH4F were mixed and stirred for 30 minutes until completely dissolved to obtain a clear solution. The solution was then transferred to a 100 ml high-pressure reactor, and the cleaned nickel foam was placed inside. The reactor was then transferred to an oven and heated to 150°C for 6 hours. After the reaction was complete, the mixture was cooled to room temperature, and the high-pressure reactor was removed to obtain the catalyst Ni. 1-X Cr X (OH)2, clean it and dry it for later use; c. The catalyst Ni obtained after the above reaction is completed 1-X Cr X (OH)₂ is cut into 1 cm × 1.5 cm pieces, and the resulting 1 cm × 1.5 cm Ni catalyst is then... 1-X Cr X (OH)₂ was placed in a reagent bottle, and then 1.5 ml of a 1.2 mg / ml palladium chloride solution was added dropwise using a pipette, ensuring the sample was completely submerged in the solution before tightening the cap. The sample was then stored at room temperature in the dark for 8 hours. After impregnation, it was rinsed several times with deionized water, then rinsed twice with ethanol, and finally dried in a vacuum oven at 60°C for 6 hours to obtain the Pd-Ni catalyst. 1-X Cr X (OH)₂, wherein the mass density of palladium is 1.2 mg / cm³. 2 about.

[0040] Comparative Example 4: Preparation of Pd-NiO Anode Catalyst This comparative example provides a method for preparing an anode catalyst Pd-NiO (compared to Example 1, the variable is the removal of Cr metal ions), as detailed below: a. Cut nickel foam into 2 cm × 3 cm pieces and ultrasonically clean them sequentially with hydrochloric acid, ethanol, and distilled water. Each cleaning session lasts 10 minutes, for a total of 30 minutes. After cleaning, place them in a vacuum oven and dry at 60°C for later use.

[0041] b. Add 4 mmol Ni(NO3)2·6H2O, 12 mmol urea, and 6 mmol NH4F to 30 ml of deionized water. Mix and stir for 30 minutes until completely dissolved to obtain a transparent solution. Then transfer the solution to a 100 ml high-pressure reactor, put the cleaned nickel foam into it, transfer it to an oven, heat to 150°C, and maintain for 6 h. After the reaction is completed, cool to room temperature, remove the high-pressure reactor, clean the precursor after the reaction, and blow it dry for later use. c. Subsequently, the precursor was placed in a tube furnace and annealed under an Ar / H2 atmosphere, heated to 400°C at 5°C per minute and held for 2 hours. After the reaction was completed, NiO catalyst loaded with spherical metal oxide particles was obtained, which was then washed and set aside for later use.

[0042] d. Cut the NiO catalyst into 1 cm × 1.5 cm pieces. Place the cut 1 cm × 1.5 cm pieces of foam metal into a reagent bottle, then use a pipette to add 1.5 ml of a 1.2 mg / ml palladium chloride solution, ensuring the sample is completely submerged in the solution. Screw on the bottle cap. Store at room temperature in the dark for 8 hours. After impregnation, wash several times with deionized water, then rinse twice with ethanol. Finally, dry in a vacuum drying oven at 60℃ for 6 hours to obtain the Pd-NiO catalyst, in which the mass density of palladium is 1.2 mg / cm³. 2 about.

[0043] Comparative Example 5: Preparation of Pd-CrO anode catalyst This comparative example provides a method for preparing an anode catalyst Pd-CrO (compared to Example 1, the variable is the removal of Ni metal ions), as detailed below: a. Cut nickel foam into 2 cm × 3 cm pieces and ultrasonically clean them sequentially with hydrochloric acid, ethanol, and distilled water. Each cleaning session lasts 10 minutes, for a total of 30 minutes. After cleaning, place them in a vacuum oven and dry at 60°C for later use.

[0044] b. Add 4 mmol (CH3CO2)3Cr, 12 mmol urea, and 6 mmol NH4F to 30 ml of deionized water. Mix and stir for 30 minutes until completely dissolved to obtain a transparent solution. Then transfer the solution to a 100 ml high-pressure reactor, put the cleaned nickel foam into it, transfer it to an oven, heat to 150°C, and maintain for 6 h. After the reaction is completed, cool to room temperature, remove the high-pressure reactor, clean the precursor after the reaction, and blow it dry for later use. c. Subsequently, the precursor was placed in a tube furnace and annealed under an Ar / H2 atmosphere, heated to 400°C at 5°C per minute and held for 2 h. After the reaction was completed, a catalyst CrO loaded with spherical metal oxide particles was obtained, which was then washed and set aside for use.

[0045] d. Cut the CrO catalyst into 1 cm × 1.5 cm pieces. Place the 1 cm × 1.5 cm pieces of foamed metal into a reagent bottle, and then use a pipette to add 1.5 ml of a 1.2 mg / ml palladium chloride solution, ensuring the sample is completely submerged in the solution. Screw on the bottle cap. Store at room temperature in the dark for 8 hours. After impregnation, wash several times with deionized water, then rinse twice with ethanol. Finally, dry in a vacuum oven at 60℃ for 6 hours to obtain the Pd-CrO catalyst, where the palladium mass density is 1.2 mg / cm³. 2 about.

[0046] Example 2: Preparation of Pd-NiCrO2-HT100 anode catalyst a. Cut nickel foam into 2 cm × 3 cm pieces, and ultrasonically clean them sequentially with hydrochloric acid, ethanol, and distilled water, 10 minutes each time, for a total of 30 minutes. After cleaning, place them in a vacuum oven at 60°C to dry for later use.

[0047] b. Add 3.6 mmol Ni(NO3)2·6H2O to 30 ml of deionized water. 0.4 mmol (CH3CO2)3Cr, 12 mmol urea, and 6 mmol NH4F were mixed and stirred for 30 minutes until completely dissolved to obtain a transparent solution. The solution was then transferred to a 100 ml high-pressure reactor, and the cleaned nickel foam was placed inside. The reactor was then transferred to an oven and heated to 100 °C for 6 h. After the reaction was completed, the reactor was cooled to room temperature, the high-pressure reactor was removed, and the precursors were cleaned and dried for later use. c. Subsequently, the precursor was placed in a tube furnace and annealed under an Ar / H2 atmosphere, heated to 400°C at 5°C per minute and held for 2 h. After the reaction was completed, a catalyst NiCrO2 loaded with spherical metal oxide particles was obtained, which was then washed and set aside for later use.

[0048] d. Cut the NiCrO2 catalyst into 1 cm × 1.5 cm pieces. Place the 1 cm × 1.5 cm pieces of foamed metal into a reagent bottle, and then add 1.5 ml of a 1.2 mg / ml palladium chloride solution using a pipette, ensuring the sample is completely submerged in the solution. Screw on the bottle cap. Store at room temperature in the dark for 8 hours. After impregnation, wash several times with deionized water, then rinse twice with ethanol. Finally, dry in a vacuum oven at 60℃ for 6 hours to obtain the catalyst Pd-NiCrO2-HT100, where the palladium mass density is 1.2 mg / cm³. 2 about.

[0049] Example 3: Preparation of Pd-NiCrO2-HT200 anode catalyst a. Cut nickel foam into 2 cm × 3 cm pieces, and ultrasonically clean them sequentially with hydrochloric acid, ethanol, and distilled water, 10 minutes each time, for a total of 30 minutes. After cleaning, place them in a vacuum oven at 60°C to dry for later use.

[0050] b. Add 3.6 mmol Ni(NO3)2·6H2O to 30 ml of deionized water. 0.4 mmol (CH3CO2)3Cr, 12 mmol urea, and 6 mmol NH4F were mixed and stirred for 30 minutes until completely dissolved to obtain a transparent solution. The solution was then transferred to a 100 ml high-pressure reactor, and the cleaned nickel foam was placed inside. The reactor was then transferred to an oven and heated to 200 °C for 6 h. After the reaction was completed, the reactor was cooled to room temperature, and the high-pressure reactor was removed. The precursors after the reaction were cleaned and dried for later use. c. Subsequently, the precursor was placed in a tube furnace and annealed under an Ar / H2 atmosphere, heated to 400°C at 5°C per minute and held for 2 h. After the reaction was completed, a catalyst NiCrO2 loaded with spherical metal oxide particles was obtained, which was then washed and set aside for later use.

[0051] d. Cut the NiCrO2 catalyst into 1 cm × 1.5 cm pieces. Place the 1 cm × 1.5 cm pieces of foamed metal into a reagent bottle, and then use a pipette to add 1.5 ml of a 1.2 mg / ml palladium chloride solution, ensuring the sample is completely submerged in the solution. Screw on the bottle cap. Store at room temperature in the dark for 8 hours. After impregnation, wash several times with deionized water, then rinse twice with ethanol. Finally, dry in a vacuum drying oven at 60℃ for 6 hours to obtain the catalyst Pd-NiCrO2-HT200, where the palladium mass density is 1.2 mg / cm³. 2 about.

[0052] Example 4: Preparation of Pd-NiCrO2-CT300 anolyte catalyst a. Cut nickel foam into 2 cm × 3 cm pieces, and ultrasonically clean them sequentially with hydrochloric acid, ethanol, and distilled water, 10 minutes each time, for a total of 30 minutes. After cleaning, place them in a vacuum oven at 60°C to dry for later use.

[0053] b. Add 3.6 mmol Ni(NO3)2·6H2O to 30 ml of deionized water. 0.4 mmol (CH3CO2)3Cr, 12 mmol urea, and 6 mmol NH4F were mixed and stirred for 30 minutes until completely dissolved to obtain a transparent solution. The solution was then transferred to a 100 ml high-pressure reactor, and the cleaned nickel foam was placed inside. The reactor was then transferred to an oven and heated to 150°C for 6 hours. After the reaction was completed, the reactor was cooled to room temperature, and the high-pressure reactor was removed. The precursors were then cleaned and dried for later use. c. Subsequently, the precursor was placed in a tube furnace and annealed under an Ar / H2 atmosphere, heated to 300°C at 5°C per minute and held for 2 h. After the reaction was completed, a catalyst NiCrO2 loaded with spherical metal oxide particles was obtained, which was then washed and set aside for use.

[0054] d. Cut the NiCrO2 catalyst into 1 cm × 1.5 cm pieces. Place the 1 cm × 1.5 cm pieces of foamed metal into a reagent bottle, and then use a pipette to add 1.5 ml of a 1.2 mg / ml palladium chloride solution, ensuring the sample is completely submerged in the solution. Screw on the bottle cap. Store at room temperature in the dark for 8 hours. After impregnation, wash several times with deionized water, then rinse twice with ethanol. Finally, dry in a vacuum drying oven at 60℃ for 6 hours to obtain the catalyst Pd-NiCrO2-CT300, where the palladium mass density is 1.2 mg / cm³. 2 about.

[0055] Example 5: Preparation of Pd-NiCrO2-CT500 anolyte catalyst a. Cut nickel foam into 2 cm × 3 cm pieces, and ultrasonically clean them sequentially with hydrochloric acid, ethanol, and distilled water, 10 minutes each time, for a total of 30 minutes. After cleaning, place them in a vacuum oven at 60°C to dry for later use.

[0056] b. Add 3.6 mmol Ni(NO3)2·6H2O to 30 ml of deionized water. 0.4 mmol (CH3CO2)3Cr, 12 mmol urea, and 6 mmol NH4F were mixed and stirred for 30 minutes until completely dissolved to obtain a transparent solution. The solution was then transferred to a 100 ml high-pressure reactor, and the cleaned nickel foam was placed inside. The reactor was then transferred to an oven and heated to 150°C for 6 hours. After the reaction was completed, the reactor was cooled to room temperature, and the high-pressure reactor was removed. The precursors were then cleaned and dried for later use. c. Subsequently, the precursor was placed in a tube furnace and annealed under an Ar / H2 atmosphere, heated to 500°C at 5°C per minute and held for 2 h. After the reaction was completed, a catalyst NiCrO2 loaded with spherical metal oxide particles was obtained, which was then washed and set aside for later use.

[0057] d. Cut the NiCrO2 catalyst into 1 cm × 1.5 cm pieces. Place the 1 cm × 1.5 cm pieces of foamed metal into a reagent bottle, and then use a pipette to add 1.5 ml of a 1.2 mg / ml palladium chloride solution, ensuring the sample is completely submerged in the solution. Screw on the bottle cap. Store at room temperature in the dark for 8 hours. After impregnation, wash several times with deionized water, then rinse twice with ethanol. Finally, dry in a vacuum drying oven at 60℃ for 6 hours to obtain the catalyst Pd-NiCrO2-CT500, in which the mass density of palladium is 1.2 mg / cm³. 2 about.

[0058] Performance test example: The anode catalysts prepared in Examples 1-5 and Comparative Examples 1-5 were used as working electrodes for electrochemical performance testing.

[0059] Taking Example 1 as an example, a three-electrode system was constructed, consisting of a reference electrode, a counter electrode, and a working electrode. A total of 50 ml of 1 M KOH and 1 MEG solution was used as the electrolyte. The working electrode was a Pd-NiCrO2 anode catalyst with a working area of ​​1 cm × 1 cm. Hg / HgO served as the reference electrode, and a platinum sheet with an area of ​​1 cm × 1 cm was used as the counter electrode. A CS310X multichannel electrochemical workstation was used to apply voltage for catalysis, converting ethylene glycol in the electrolyte into glycolic acid. Figure 5 The figure shows the LSV curves for water electrolysis and ethylene glycol electrolysis using Pd-NiCrO2 as the anode. It can be seen from the figure that when the current density reaches 100 mA / cm², the electrolysis results in a higher LSV. 2 At this time, the voltage required for the electrolysis of ethylene glycol is only 0.701 V, far lower than the 1.583 V required for the electrolysis of water. This indicates that the catalyst Pd-NiCrO2 has excellent electrocatalytic activity for the oxidation of ethylene glycol.

[0060] Figure 6 For Example 1, and the LSV curves of electrolytic ethylene glycol in Comparative Examples 1-3, Pd-NiCrO2 showed significantly higher efficiency than NiCrO2, Pd-NF, and Pd-Ni for the electrocatalytic oxidation of ethylene glycol. 1-x Cr x The electrocatalytic performance of (OH)2 indicates that the interaction between Pd and NiCrO2 plays a crucial role in enhancing the oxidation activity of ethylene glycol.

[0061] Figure 7For Example 1 and the LSV curves of ethylene glycol electrolysis in Comparative Examples 4-5, Pd-NiCrO2 showed significantly higher electrocatalytic performance than Pd-NiO and Pd-CrO for the electrocatalytic oxidation of ethylene glycol. This indicates that Pd interacts with NiO and CrO and possesses good electrocatalytic performance for ethylene glycol oxidation. When all three are present, the electrocatalytic activity for ethylene glycol oxidation is greatly enhanced, thus Pd-NiCrO2 exhibits superior performance. This also proves that both nickel and chromium sources are indispensable in the synthesis process.

[0062] Figure 8 The LSV curves for the electrolysis of ethylene glycol in Examples 1-3 show that Pd-NiCrO2 exhibits significantly higher electrocatalytic performance than Pd-NiCrO2-HT100 and Pd-NiCrO2-HT200 for the electrocatalytic oxidation of ethylene glycol. This indicates that the hydrothermal temperature was too low (100°C) during the hydrothermal process, resulting in incomplete reaction and insufficient Ni production. 1-x Cr x (OH)2 results in poor final performance. If the hydrothermal temperature is too high (200℃), the reaction may be over-oxidized to generate hydroxides with higher valence states, which are difficult to reverse in subsequent reducing annealing, leading to poor performance. Overall, a hydrothermal temperature of 150℃ is the most suitable choice.

[0063] Figure 9 The LSV curves for the electrolytic oxidation of ethylene glycol in Examples 1, 4-5 show that Pd-NiCrO2 exhibits significantly higher electrocatalytic performance than Pd-NiCrO2-CT300 for the electrocatalytic oxidation of ethylene glycol, and its performance is comparable to that of Pd-NiCrO2-CT500. This indicates that the calcination temperature was too low (300℃) during the reducing annealing process, resulting in weak reducing power and incomplete reaction, failing to completely oxidize Ni. 1-x Cr x (OH)2 is fully reduced to NiCrO 2， This results in poor final performance. If the calcination temperature is too high (500℃), the performance improvement is not significant, resulting in additional waste of resources. Overall, a calcination temperature of 400℃ is the most suitable choice.

[0064] Figure 10 The figure shows the it curve of Pd-NiCrO2 electrolysis of ethylene glycol. As can be seen from the figure, the catalyst has extremely strong stability and achieves stable electrolysis of ethylene glycol. Under a voltage of 1 V vs. RHE, the current retention rate is as high as 90% or more after two hours of continuous operation.

[0065] Application example: The electrolysis products were analyzed after electrochemical performance testing using the Pd-NiCrO2 anode catalyst prepared in Example 1 as the electrode. The electrolyte after the reaction was collected and analyzed by nuclear magnetic resonance spectroscopy. Dimethyl sulfoxide was used as an internal standard and dispersed in deuterated heavy water.

[0066] Figure 11 The 1H NMR spectra of the products collected after electrolysis of Pd-NiCrO2 catalyst at different voltages for 2 h are shown. With the increase of voltage, the peak of ethylene glycol at 3.5 ppm gradually decreases, the peak of glycolic acid at 3.8 ppm gradually increases, and no peak of formate is found at 8.2 ppm. This indicates that the Pd-NiCrO2 catalyst has high selectivity and good conversion rate, and can directionally convert ethylene glycol into glycolic acid.

[0067] The embodiments described with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention. The embodiments should not be considered as limiting the invention, but any improvements made based on the spirit of the invention should be within the scope of protection of the invention.

Claims

1. A method for preparing an anode catalyst, characterized in that, Includes the following steps, Step 1, hydrothermal reaction: The pretreated nickel foam is placed in an aqueous solution containing nickel source, chromium source, ammonium fluoride and urea to carry out a hydrothermal reaction to obtain a nickel foam precursor loaded with nickel-chromium hydroxide; Step 2, Annealing: The nickel foam precursor obtained in Step 1 is annealed in an Ar / H2 mixed atmosphere to obtain nickel foam loaded with NiCrO2. Step 3, Impregnation: The nickel foam loaded with NiCrO2 obtained in Step 2 is impregnated in a palladium chloride solution, removed and dried to obtain the anode catalyst.

2. The method for preparing the anode catalyst according to claim 1, characterized in that, The nickel source is one or more of nickel nitrate hexahydrate, nickel chloride, and nickel sulfate; the chromium source is one or more of chromium acetate, chromium sulfate, chromium nitrate, and chromium acetylacetone; the molar ratio of the nickel source to the chromium source is 9:1, and the molar ratio of the metal ions, ammonium fluoride, and urea is 2:3:

6.

3. The method for preparing the anode catalyst according to claim 1, characterized in that, The pretreatment mentioned in step one involves placing the nickel foam in hydrochloric acid solution, ethanol, and deionized water in sequence for pretreatment, and then drying it at room temperature.

4. The method for preparing the anode catalyst according to claim 1, characterized in that, In the hydrothermal reaction of step one, the hydrothermal temperature is 100~200℃ and the hydrothermal time is 6 hours.

5. The method for preparing the anode catalyst according to claim 1, characterized in that, In the annealing process of step two, the annealing temperature is 300~500℃, the atmosphere is Ar / H2, and the annealing time is 2 hours.

6. The method for preparing the anode catalyst according to claim 1, characterized in that, In the impregnation process of step three, the amount of palladium chloride solution used is 1 ml / cm². 2 The solution concentration was 1.2 mg / ml, the immersion time was 12 hours, and the immersion process should be kept away from light.

7. A method for the highly selective electrocatalytic preparation of glycolate from ethylene glycol, characterized in that, A three-electrode system consisting of a reference electrode, a counter electrode, and a working electrode is used. An alkaline solution containing ethylene glycol is used as the electrolyte. The anode catalyst prepared by the method described in any one of claims 1-6 is used as the working electrode. A voltage is applied using an electrochemical workstation to catalyze the conversion of ethylene glycol in the anode to glycolate.

8. The method for highly selective electrocatalytic preparation of glycolate from ethylene glycol according to claim 7, characterized in that, The reference electrode is an Hg / HgO electrode or an Ag / AgCl electrode; the counter electrode is a platinum sheet, platinum wire, or carbon rod.

9. The method for highly selective electrocatalytic preparation of glycolate from ethylene glycol according to claim 7, characterized in that, The electrolyte is 1-3 mol / L potassium hydroxide or sodium hydroxide and 1-3 mol / L ethylene glycol.

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