NiOx / NF loaded palladium nanoparticle catalyst, preparation method thereof and method for electrocatalyzing PET (polyethylene terephthalate) plastic by NiOx / NF loaded palladium nanoparticle catalyst

Abstract

The invention provides a preparation method of a NiOx / NF loaded palladium nanoparticle catalyst, which comprises the following steps: sequentially placing foamed nickel (NF) in a hydrochloric acid solution, an acetone solution and deionized water for ultrasonic treatment, and drying to obtain pretreated NF; the preparation method comprises the following steps: dissolving nickel nitrate hexahydrate and hexamethylenetetramine in deionized water, performing ultrasonic treatment to form a uniform solution, pouring the uniform solution into a high-pressure reaction kettle, vertically immersing pretreated NF into the uniform solution, sealing, performing hydrothermal reaction, taking out, washing and drying to obtain a Ni (OH) 2 / NF intermediate attached with an ultrathin nickel hydroxide nanosheet array; and placing the obtained Ni (OH) 2 / NF intermediate in a tubular furnace, and sintering under a nitrogen condition to obtain a NiOx / NF precursor attached with a porous nickel oxide nanosheet array. And placing the obtained NiOx / NF precursor in a palladium salt solution, carrying out a constant temperature reaction, taking out, washing, and drying to finally obtain the NiOx / NF supported palladium nanoparticle catalyst. The invention also discloses a NiOx / NF supported palladium nanoparticle catalyst and a method for electrocatalyzing PET plastic by using the NiOx / NF supported palladium nanoparticle catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of waste plastic upgrading and conversion, and particularly relates to a NiO x / NF loaded palladium nanoparticle catalyst and its preparation method and its electrocatalytic method for PET plastic. Background Art

[0002] Plastics are widely used due to their excellent performance, convenient molding and processing characteristics, and low cost advantages. The large-scale production and widespread use of plastics have greatly facilitated people's daily lives, but at the same time, they have also caused serious environmental problems. In addition, if petroleum-based synthetic plastic products cannot be effectively recycled and reused, this will undoubtedly cause a serious waste of petroleum resources.

[0003] Polyethylene glycol terephthalate (PET) is a polyester that ranks second in the global production of thermoplastic polymer materials, and China's polyester production ranks first. PET itself has extremely outstanding characteristics, excellent physical and mechanical properties, good electrical insulation, outstanding fatigue and friction resistance, and stable size. These advantages make it the main component of synthetic polyester, accounting for more than 80% of the total amount of synthetic fibers. In addition, PET is odorless and non-toxic, and can be safely in direct contact with food-grade products, so it is widely used in many fields such as food packaging and catering packaging. However, at this stage, most PET plastic products are used as disposable consumer products. Once discarded, it is difficult for them to degrade on their own in the natural environment. There are two main ways to recycle it: physical regeneration and chemical recycling. In the physical regeneration process, due to the simultaneous action of thermal processing and mechanical processing, the molecular weight of the recycled product will inevitably decrease, which means that most of them can only be downgraded and cannot be recycled multiple times, and it is also difficult to handle waste fibers with complex compositions. Chemical recycling, on the other hand, is to depolymerize the long molecular chains of waste PET plastics into monomers or crack them into small molecular organic matter under specific chemical or biochemical conditions, and then obtain upgraded products such as raw materials through product purification or cracking oil and gas refining. In theory, chemical recycling has the potential to achieve a "closed" cycle of waste plastics, and for this reason, it has been receiving much attention in the fields of science and technology and industry in recent years.

[0004] PET has the chemical formula (C 10 H8O4) nIn an alkaline environment, it can undergo chemical hydrolysis to produce purified terephthalic acid (PTA) and ethylene glycol (EG). However, it is difficult to separate the products generated in this process. In recent years, with the help of special chemical conditions such as light and electricity and with the assistance of catalysts, EG has been catalytically converted into high-value and easily separable chemicals such as glycolic acid (GA), which has become a very promising way to recycle PET at a high value. Recently, it has been reported that PET plastics can be converted into valuable formates and glycolates by photoelectrocatalysis. However, even though the relevant methods have made progress, the process still has problems such as low spatial productivity and poor selectivity for single high-value oxidation products.

[0005] In order to solve the above technical problems, the present invention designs a NiO x / NF loaded palladium nanoparticle catalyst and its preparation method and its electrocatalytic method for PET plastic. Summary of the invention

[0006] The present invention provides a NiO x / NF supported palladium nanoparticle catalyst, preparation method thereof and method for electrocatalyzing PET plastic thereof are aimed at solving the problems of low spatial productivity and poor selectivity for a single high-value oxidation product.

[0007] To achieve the above object, the present invention provides the following technical solution: a NiO x The preparation method of the NF-supported palladium nanoparticle catalyst comprises the following steps: S1, placing nickel foam (NF) in a hydrochloric acid solution, an acetone solution and deionized water for ultrasonic treatment in sequence, and then drying in a vacuum drying oven to obtain pretreated NF; S2, dissolving nickel nitrate hexahydrate and hexamethylenetetramine in deionized water, ultrasonicating to form a uniform solution, pouring into a high-pressure reactor, vertically immersing the pretreated NF into the uniform solution, sealing for hydrothermal reaction, cooling to room temperature after the reaction is complete, taking out and washing with deionized water and anhydrous ethanol for several times, and then placing in a vacuum drying oven for drying to obtain a Ni(OH)2 / NF intermediate with an ultrathin nickel hydroxide nanosheet array attached; S3, placing the obtained Ni(OH)2 / NF intermediate in a tube furnace and sintering it under nitrogen conditions to obtain NiO with porous nickel oxide nanosheet arrays attached. x / NF precursor; S4, the obtained NiO xThe / NF precursor was placed in a palladium salt solution, reacted at a constant temperature, and washed with deionized water and anhydrous ethanol respectively, and then placed in a vacuum drying oven for drying to finally obtain NiO x / NF supported palladium nanoparticle catalyst.

[0008] Based on the above technical solution, in step S1, the concentration of the hydrochloric acid solution is 1-3 mol / L, the ultrasonic time is 5-10 min, and the vacuum drying temperature is 60°C.

[0009] Based on the above technical solution, in step S2, the molar ratio of nickel nitrate hexahydrate to hexamethylenetetramine is 1:2, the hydrothermal temperature is 100-120° C., and the hydrothermal time is 10 h.

[0010] Based on the above technical solution, in step S3, the sintering temperature is 300-500° C. and the sintering time is 2 hours.

[0011] Based on the above technical solution, in step S4, the palladium salt solution is a palladium chloride solution or a potassium tetrachloropalladate solution, and the concentration of the palladium salt solution is 5-20 mg / ml.

[0012] In a second aspect, the present invention provides a NiO x / NF supported palladium nanoparticle catalyst, according to any one of the above examples of NiO x / NF is prepared by the preparation method of supported palladium nanoparticle catalyst.

[0013] In a third aspect, the present invention provides a NiO x The method for electrocatalyzing PET plastics by using a palladium nanoparticle catalyst supported by a NF includes the following steps: A1, washing and drying the PET plastic, then dissolving it in an alkaline solution at high temperature, cooling it to room temperature, and filtering it for solid-liquid separation to obtain an ethylene glycol alkaline solution as a PET hydrolysis product; A2, assemble a flow-type electrolytic cell, the working electrode is the NiO described in claim 6 x / NF loaded with palladium nanoparticle catalyst, the electrolyte in the anode region is PET hydrolysis product, the electrolyte in the cathode region is potassium hydroxide solution, and the cathode region and the anode region are separated by an ion exchange membrane; A3, heating the flow-type electrolytic cell and applying voltage to the electrolytic cell, so that the PET hydrolysis product in the anode electrolyte undergoes an electrocatalytic oxidation reaction, and glycolic acid is obtained after the reaction is completed.

[0014] Based on the above technical solution, in step A1, the alkaline solution is a potassium hydroxide solution or a sodium hydroxide solution, the concentration of the alkaline solution is 3-10 mol / L, the dissolution temperature is 80-120°C, the dissolution time is 12-72h, and the pH is adjusted to 1-3.

[0015] On the basis of the above technical scheme, in the step A2, the cathode electrode is Ni2P / NF obtained by phosphating the Ni(OH)2 / NF intermediate obtained in the step S2 in a tubular furnace. During the phosphating process, sodium hypophosphite powder is placed at one end of the steam inlet, and the Ni(OH)2 / NF intermediate is placed at the other end. Sintering is performed in a nitrogen atmosphere at a sintering temperature of 300-400°C and a sintering time of 2-3h. The concentration of the ethylene glycol solution in the electrolyte of the anode region is 320-1000mmol / L, and the concentration of the potassium hydroxide solution is 1-10mol / L.

[0016] Based on the above technical solution, in step A3, the heating temperature is 25-60° C., the applied voltage range is 0.4-1.3 V vs. RHE, and the electrocatalytic oxidation reaction time is 0.5 h-300 h.

[0017] Compared with the related art, the beneficial effects of the present invention are as follows: 1. The present invention adopts a simple method to synthesize NiO x / NF supported palladium nanoparticle catalyst Pd-NiO x / NF, the catalyst has the advantages of large specific surface area, low Pd loading and high activity. In the catalytic process, the material can provide more active sites and increase its contact range with the reactants, thereby significantly improving the catalytic activity, providing a highly efficient and low-cost electrocatalyst for the electrocatalytic oxidation of PET; 2. Pd-NiO synthesized by the present invention x By introducing NiO x As an oxophilic compound, it can adjust the electronic structure of palladium and thus change the adsorption of carbonyl intermediates on the surface of the material. x The presence of promotes the formation of hydroxyl radicals. The synergistic effect of the two not only improves the selectivity of the catalyst, but also increases the anti-poisoning ability of the material, thereby improving the process of PET electrocatalytic oxidation and increasing the reaction rate; 3. The material preparation method provided by the present invention is simple and easy to implement, the required raw materials are easy to obtain and the preparation process is environmentally friendly and green. In the technical field of electrocatalytic oxidation of PET, the method has significant application value and broad application prospects and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0019] Figure 1 The NiO provided by the present invention x / Flow chart of the preparation method of NF-supported palladium nanoparticle catalyst.

[0020] Figure 2 The NiO provided by the present invention x Flow chart of the method for electrocatalysis of PET plastic with palladium nanoparticle catalyst supported on / NF.

[0021] Figure 3 is the Pd obtained in Example 1 of the present invention 1.0 -NiO x / NF scanning electron micrograph.

[0022] Figure 4 is the Pd scraped off from the catalyst in Example 1 of the present invention 1.0 -NiO x High-resolution transmission electron microscopy image.

[0023] Figure 5 The Pd-NiO with different palladium contents prepared in Examples 1-4 of the present invention x Current density curve of EG oxidation process over / NF catalyst.

[0024] Figure 6 is Pd in ​​Example 5 of the present invention and Comparative Example 1 1.0 -NiO x Linear sweep voltammetric characteristic curves of EG oxidation process and traditional oxygen evolution reaction of / NF catalyst respectively.

[0025] Figure 7 is Pd in ​​Example 5 of the present invention 1.0 -NiO x H NMR spectra of / NF catalyst under different charge passages.

[0026] Figure 8 is Pd in ​​Example 5 of the present invention 1.0 -NiO x Bar graph of the Faradaic efficiency of glycolic acid over the TU / NF catalyst at different charge passes.

[0027] Fig. 9It is the nuclear magnetic resonance hydrogen spectrum of the PET hydrolysis product before and after electrocatalysis in Example 6 of the present invention.

[0028] Fig.10 is Pd in ​​Example 6 of the present invention 1.0 -NiO x Time-current curve of PET hydrolysis products catalyzed by / NF catalyst. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings and examples: Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0033] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0034] The present invention provides a NiO x The preparation method of the NF-supported palladium nanoparticle catalyst comprises the following steps: S1, placing nickel foam (NF) in a hydrochloric acid solution, an acetone solution and deionized water for ultrasonic treatment in sequence, and then drying in a vacuum drying oven to obtain pretreated NF; S2, dissolving nickel nitrate hexahydrate and hexamethylenetetramine in deionized water, ultrasonicating to form a uniform solution, pouring into a high-pressure reactor, vertically immersing the pretreated NF into the uniform solution, sealing for hydrothermal reaction, cooling to room temperature after the reaction is complete, taking out and washing with deionized water and anhydrous ethanol for several times, and then placing in a vacuum drying oven for drying to obtain a Ni(OH)2 / NF intermediate with an ultrathin nickel hydroxide nanosheet array attached; S3, placing the obtained Ni(OH)2 / NF intermediate in a tube furnace and sintering it under nitrogen conditions to obtain NiO with porous nickel oxide nanosheet arrays attached. x / NF precursor; S4, the obtained NiO x The / NF precursor was placed in a palladium salt solution, reacted at a constant temperature, and washed with deionized water and anhydrous ethanol respectively, and then placed in a vacuum drying oven for drying to finally obtain NiO x / NF supported palladium nanoparticle catalyst.

[0035] Based on the above technical solution, in step S1, the concentration of the hydrochloric acid solution is 1-3 mol / L, the ultrasonic time is 5-10 min, and the vacuum drying temperature is 60° C. Preferably, the concentration of the hydrochloric acid solution is 1 mol / L, and the ultrasonic time is 10 min.

[0036] Based on the above technical solution, in step S2, the molar ratio of nickel nitrate hexahydrate to hexamethylenetetramine is 1:2, the hydrothermal temperature is 100-120°C, and the hydrothermal time is 10 hours. Preferably, the hydrothermal temperature is 100°C.

[0037] Based on the above technical solution, in step S3, the sintering temperature is 300-500°C, and the sintering time is 2 hours. Preferably, the sintering temperature is 400°C.

[0038] Based on the above technical solution, in step S4, the palladium salt solution is a palladium chloride solution or a potassium tetrachloropalladate solution, and the concentration of the palladium salt solution is 5-20 mg / ml. Preferably, the palladium salt concentration is 10 mg / ml.

[0039] In a second aspect, the present invention provides a NiO x / NF supported palladium nanoparticle catalyst, according to any one of the above examples of NiO x / NF is prepared by the preparation method of supported palladium nanoparticle catalyst.

[0040] In a third aspect, the present invention provides a NiO x The method for electrocatalyzing PET plastics by using a palladium nanoparticle catalyst supported by a NF includes the following steps: A1, washing and drying the PET plastic, then dissolving it in an alkaline solution at high temperature, cooling it to room temperature, and filtering it for solid-liquid separation to obtain an ethylene glycol alkaline solution as a PET hydrolysis product; A2, assemble a flow-type electrolytic cell, the working electrode is the NiO described in the above embodiment x / NF loaded with palladium nanoparticle catalyst, the electrolyte in the anode region is PET hydrolysis product, the electrolyte in the cathode region is potassium hydroxide solution, and the cathode region and the anode region are separated by an ion exchange membrane; A3, heating the flow-type electrolytic cell and applying voltage to the electrolytic cell, so that the PET hydrolysis product in the anode electrolyte undergoes an electrocatalytic oxidation reaction, and glycolic acid is obtained after the reaction is completed.

[0041] Based on the above technical solution, in step A1, the alkaline solution is a potassium hydroxide solution or a sodium hydroxide solution, the concentration of the alkaline solution is 3-10 mol / L, the dissolution temperature is 80-120°C, the dissolution time is 12-72h, and the pH is adjusted to 1-3. Preferably, the concentration of the alkaline solution is 5 mol / L, the dissolution temperature is 80°C, the dissolution time is 24h, and the pH is adjusted to 2.

[0042] On the basis of the above technical scheme, in step A2, the cathode electrode is Ni2P / NF obtained by phosphating the Ni(OH)2 / NF intermediate obtained in step S2 in a tube furnace, and during the phosphating process, sodium hypophosphite powder is placed at one end of the steam inlet, and the Ni(OH)2 / NF intermediate is placed at the other end, and sintering is performed in a nitrogen atmosphere, the sintering temperature is 300-400°C, the sintering time is 2-3h, the concentration of the ethylene glycol solution in the anode electrolyte is 320-1000mmol / L, and the concentration of the potassium hydroxide solution is 1-10mol / L. Preferably, the sintering temperature is 300°C, the sintering time is 2h, the concentration of the ethylene glycol solution is 1000mmol / L, and the concentration of the potassium hydroxide solution is 1mol / L.

[0043] Based on the above technical solution, in step A3, the heating temperature is 25-60°C, the applied voltage range is 0.4-1.3V vs. RHE, and the electrocatalytic oxidation reaction time is 0.5h-300h. Preferably, the heating temperature is 60°C and the applied voltage is 1.2V.

[0044] The present invention adopts a simple method to synthesize NiO x / NF supported palladium nanoparticle catalyst Pd-NiO x / NF, the catalyst has the advantages of large specific surface area, low Pd loading and high activity. In the catalytic process, the material can provide more active sites and increase its contact range with the reactants, thereby significantly improving the catalytic activity, providing a highly efficient and low-cost electrocatalyst for the electrocatalytic oxidation of PET.

[0045] Pd-NiO synthesized by the present invention x By introducing NiO x As an oxophilic compound, it can adjust the electronic structure of palladium and thus change the adsorption of carbonyl intermediates on the surface of the material. x The presence of promotes the formation of hydroxyl radicals. The synergistic effect of the two not only improves the selectivity of the catalyst, but also increases the material's anti-poisoning ability, thereby improving the process of PET electrocatalytic oxidation and increasing the reaction rate.

[0046] The material preparation method provided by the invention is simple and easy to implement, the required raw materials are easy to obtain and the preparation process is environmentally friendly and green. In the technical field of electrocatalytic oxidation of PET, the method has significant application value and broad application prospects and is suitable for industrial production.

[0047] Example 1 like Figure 1 As shown, the embodiment of the present disclosure provides a NiO x The preparation method of the NF-supported palladium nanoparticle catalyst comprises the following steps: S1, placing nickel foam (NF) with a size of 2 cm*3 cm*1.6 mm in 1 mol / L hydrochloric acid solution, 1 mol / L acetone solution and deionized water in sequence and ultrasonicating for 10 min, then placing it in a vacuum drying oven at 60 °C for 12 h to obtain the pretreated NF; S2, dissolving 1.09g nickel nitrate hexahydrate and 1.05g hexamethylenetetramine in 30mL deionized water, ultrasonicating to form a uniform solution, pouring into a high-pressure reactor, vertically immersing the pretreated NF into the uniform solution, sealing, and hydrothermally reacting at 100°C for 10h. After the reaction is complete, cooling to room temperature, taking out the reacted NF, washing it with deionized water and anhydrous ethanol for 3 times respectively, and then placing it in a vacuum drying oven at 60°C for 12h to obtain a Ni(OH)2 / NF intermediate with an ultrathin nickel hydroxide nanosheet array attached; S3, the obtained Ni(OH)2 / NF intermediate is placed in a tube furnace, sintered under nitrogen conditions, and kept at 400°C for 2h to obtain NiO with porous nickel oxide nanosheet arrays. x / NF precursor; S4, the obtained NiO xThe / NF precursor was cut into square pieces of 1cm*2cm in size, placed vertically in 200mL of 10mg / mL palladium chloride solution, and kept at 28℃ for 2h. After being taken out, it was washed with deionized water and anhydrous ethanol for 3 times respectively, and then placed in a vacuum drying oven at 60℃ for 12h to finally obtain a palladium content of 1.0mg / cm 2 NiO x Pd / NF supported palladium nanoparticle catalyst 1.0 -NiO x / NF.

[0048] Example 2 The preparation method of this embodiment is the same as that of embodiment 1, and the same parts are omitted. The difference from embodiment 1 is that in this embodiment, the concentration of palladium chloride solution or potassium tetrachloropalladate solution is 5 mg / mL, and the final palladium content is 0.5 mg / cm 2 NiO x Pd / NF supported palladium nanoparticle catalyst 0.5 -NiO x / NF.

[0049] Example 3 The preparation method of this embodiment is the same as that of embodiment 1, and the same parts are omitted. The difference from embodiment 1 is that in this embodiment, the concentration of palladium chloride solution or potassium tetrachloropalladate solution is 15 mg / mL, and the final palladium content is 1.5 mg / cm 2 NiO x Pd / NF supported palladium nanoparticle catalyst 1.5 -NiO x / NF.

[0050] Example 4 The preparation method of this embodiment is the same as that of embodiment 1, and the same parts are omitted. The difference from embodiment 1 is that in this embodiment, the concentration of palladium chloride solution or potassium tetrachloropalladate solution is 20 mg / mL, and the final palladium content is 2.0 mg / cm 2 NiO x Pd / NF supported palladium nanoparticle catalyst 2.0 -NiO x / NF.

[0051] Example 5 A three-electrode system was used to carry out catalytic oxidation in an electrolytic cell, with the palladium content of 1 mg / cm2 prepared in Example 1 being 1 mg / cm2. 2 NiO x The palladium nanoparticle catalyst supported on NF was used as the working electrode, Ag / AgCl was used as the reference electrode, and platinum sheet was used as the counter electrode. The volume ratio was 18:1 with 1 mol·L -1of potassium hydroxide solution and 1 mol·L -1 The mixed solution of ethylene glycol solution is the electrolyte, which together constitutes an electrocatalytic reactor. At room temperature and pressure, the linear sweep voltammetric characteristic curve test is carried out under the condition of 0.4~1.3V vs.RHE, and the reaction is continuously stirred at a constant voltage of 0.8V vs.RHE.

[0052] Comparative Example 1 The preparation method of this embodiment is the same as that of embodiment 5, and the same parts are omitted. The difference from embodiment 5 is that in this embodiment, the electrolyte is 1 mol·L -1 of potassium hydroxide solution, and the voltage range is 0.4~2.0V vs.RHE.

[0053] Example 6 like Figure 2 As shown, the embodiment of the present disclosure provides a NiO x The method for electrocatalyzing PET plastics by using a palladium nanoparticle catalyst supported by a NF includes the following steps: A1, 10g of PET plastic is washed and dried, then placed in a potassium hydroxide alkaline solution, heated to 80°C by oil bath reflux, heated for 24 hours, cooled to room temperature, and solid-liquid separated by suction filtration to obtain ethylene glycol solution and potassium terephthalate precipitate, the potassium terephthalate precipitate is washed with deionized water, and acidified with 12 mol / L hydrochloric acid to obtain terephthalic acid, and the separated ethylene glycol and potassium hydroxide mixed solution is used as the PET hydrolysis product; A2, assemble a flow-type electrolytic cell, the working electrode is the palladium content of 1 mg / cm prepared in Example 1 2 NiO x / NF loaded with palladium nanoparticle catalyst, the cathode electrode is Ni2P / NF obtained by phosphating the Ni(OH)2 / NF intermediate obtained in step S2 of Example 1 in a tube furnace at 300°C, the electrolyte in the anode region is a PET hydrolyzate, the electrolyte in the cathode region is a potassium hydroxide solution, and the cathode region and the anode region are separated by an ion exchange membrane; A3, the flow-type electrolytic cell is heated at 60°C and a voltage of 1.2V is applied to the electrolytic cell. The PET hydrolysis product of the anode electrolyte is subjected to an electrocatalytic oxidation reaction for 250 hours, and glycolic acid is obtained after the reaction is completed.

[0054] Figure 3 is the Pd obtained in Example 1 of the present invention 1.0 -NiO x From the scanning electron microscope image of / NF, we can see that it has a distinct coral-like structure and good contact with the substrate, which provides a possibility for increasing conductivity and exposing more active sites.

[0055] Figure 4 It is the Pd scraped off from the catalyst in Example 1 of the present invention. 1.0 -NiO x High-resolution transmission electron microscopy images of Pd and NiO show different interplanar spacings and clear x The lattice bending phenomenon can also be observed, which indicates that there is an interaction between Pd and the NF substrate, providing a basis for improving activity and selectivity.

[0056] Figure 5 The Pd-NiO with different palladium contents prepared in Examples 1-4 of the present invention are x The current density curve of EG oxidation process of Pd-NiO / NF catalyst clearly shows that x / NF catalyst with a palladium content of 1 mg / cm 2 When , the electrocatalytic oxidation performance of EG is the best.

[0057] Figure 6 is Pd in ​​Example 5 of the present invention and Comparative Example 1 1.0 -NiO x Linear sweep voltammetric curves of the EG oxidation process and the traditional oxygen evolution reaction of the Pd-NiO / NF catalyst. In contrast, the Pd-NiO / NF catalyst has a higher current density than the Pd-NiO catalyst in the EG oxidation process. x The / NF catalyst requires a lower potential and shows good potential PET electrocatalytic effect.

[0058] Figure 7 is Pd in ​​Example 5 of the present invention 1.0 -NiO x The H NMR spectra of the / NF catalyst under different charges describe the dynamic process of EG to GA oxidation. It can be found that with the increase of charge, the content of EG gradually decreases and the content of GA gradually increases.

[0059] Figure 8 is Pd in ​​Example 5 of the present invention 1.0 -NiO x The Faradaic efficiency bar graph of glycolic acid under different charge passing of Pd-NiO / NF catalyst. During the whole electrocatalytic process, the Faradaic efficiency of glycolic acid remained above 90%, indicating that the Pd-NiO x / NF catalyst has higher selectivity.

[0060] Fig. 9 It is the nuclear magnetic resonance hydrogen spectrum of the PET hydrolyzate before and after electrocatalysis in Example 6 of the present invention. The results show that the content of EG in the PET hydrolyzate decreases and the content of GA increases after electrocatalysis.

[0061] Fig.10 is Pd in ​​Example 6 of the present invention 1.0 -NiO x Figure 3 is the time-current curve of the electrocatalytic hydrolysis product of PET by / NF catalyst. The constant voltage method was used to carry out electrocatalytic reaction on the hydrolysis product of PET. Under the condition of 1.2V voltage, the electrolyte flow rate in the anode and cathode regions was 40ml / min. The PET hydrolysis product was completely electrolyzed within 250h to obtain glycolic acid solution with a yield of 50.2%, wherein the yield is the ratio of the amount of glycolic acid actually obtained by electrolysis of the same mass of PET to the amount of glycolic acid produced theoretically.

[0062] The present invention is described above by way of examples, but the present invention is not limited to the above specific embodiments, and any changes or modifications made based on the present invention belong to the scope of protection claimed by the present invention.

Claims

1. A NiO x A method for preparing a palladium nanoparticle catalyst supported by a NF, characterized in that: The following steps are involved: S1, placing nickel foam (NF) in a hydrochloric acid solution, an acetone solution and deionized water for ultrasonic treatment in sequence, and then drying in a vacuum drying oven to obtain pretreated NF; S2, dissolving nickel nitrate hexahydrate and hexamethylenetetramine in deionized water, ultrasonicating to form a uniform solution, pouring into a high-pressure reactor, vertically immersing the pretreated NF into the uniform solution, sealing for hydrothermal reaction, cooling to room temperature after the reaction is complete, taking out and washing with deionized water and anhydrous ethanol for several times, and then placing in a vacuum drying oven for drying to obtain a Ni(OH)2 / NF intermediate with an ultrathin nickel hydroxide nanosheet array attached; S3, placing the obtained Ni(OH)2 / NF intermediate in a tube furnace and sintering it under nitrogen conditions to obtain NiO with porous nickel oxide nanosheet arrays attached. x / NF precursor; S4, the obtained NiO x The / NF precursor was placed in a palladium salt solution, reacted at a constant temperature, and washed with deionized water and anhydrous ethanol respectively, and then placed in a vacuum drying oven for drying to finally obtain NiO x / NF supported palladium nanoparticle catalyst.

2. NiO according to claim 1 x A method for preparing a palladium nanoparticle catalyst supported by a NF, characterized in that: In the step S1, the concentration of the hydrochloric acid solution is 1-3 mol / L, the ultrasonic time is 5-10 min, and the vacuum drying temperature is 60°C.

3. NiO according to claim 1 x A method for preparing a palladium nanoparticle catalyst supported by a NF, characterized in that: In the step S2, the molar ratio of nickel nitrate hexahydrate to hexamethylenetetramine is 1:2, the hydrothermal temperature is 100-120° C., and the hydrothermal time is 10 h.

4. NiO according to claim 1 x A method for preparing a palladium nanoparticle catalyst supported by a NF, characterized in that: In step S3, the sintering temperature is 300-500° C. and the sintering time is 2 hours.

5. NiO according to claim 1 x A method for preparing a palladium nanoparticle catalyst supported by a NF, characterized in that: In step S4, the palladium salt solution is a palladium chloride solution or a potassium tetrachloropalladate solution, and the concentration of the palladium salt solution is 5-20 mg / ml.

6. A NiO x / NF supported palladium nanoparticle catalyst, characterized in that NiO according to any one of claims 1 to 5 x / NF is prepared by the preparation method of supported palladium nanoparticle catalyst.

7. A NiO x / NF supported palladium nanoparticle catalyst electrocatalyzed PET plastic method, characterized in that, The following steps are involved: A1, washing and drying the PET plastic, then dissolving it in an alkaline solution at high temperature, cooling it to room temperature, and filtering it for solid-liquid separation to obtain an ethylene glycol alkaline solution as a PET hydrolysis product; A2, assemble a flow-type electrolytic cell, the working electrode is the NiO described in claim 6 x / NF loaded with palladium nanoparticle catalyst, the electrolyte in the anode region is PET hydrolysis product, the electrolyte in the cathode region is potassium hydroxide solution, and the cathode region and the anode region are separated by an ion exchange membrane; A3, heating the flow-type electrolytic cell and applying voltage to the electrolytic cell, so that the PET hydrolysis product in the anode electrolyte undergoes an electrocatalytic oxidation reaction, and glycolic acid is obtained after the reaction is completed.

8. NiO according to claim 7 x / NF supported palladium nanoparticle catalyst electrocatalyzed PET plastic method, characterized in that, In the step A1, the alkaline solution is a potassium hydroxide solution or a sodium hydroxide solution, the concentration of the alkaline solution is 3-10 mol / L, the dissolution temperature is 80-120° C., the dissolution time is 12-72 h, and the pH is adjusted to 1-3.

9. NiO according to claim 7 x / NF supported palladium nanoparticle catalyst electrocatalyzed PET plastic method, characterized in that, In the step A2, the cathode electrode is Ni2P / NF obtained by phosphating the Ni(OH)2 / NF intermediate obtained in the step S2 in a tubular furnace. During the phosphating process, sodium hypophosphite powder is placed at one end of the steam inlet, and the Ni(OH)2 / NF intermediate is placed at the other end. Sintering is performed in a nitrogen atmosphere at a sintering temperature of 300-400°C and a sintering time of 2-3h. The concentration of the ethylene glycol solution in the anode electrolyte is 320-1000mmol / L, and the concentration of the potassium hydroxide solution is 1-10mol / L.

10. NiO according to claim 7 x / NF supported palladium nanoparticle catalyst electrocatalyzed PET plastic method, characterized in that, In the step A3, the heating temperature is 25-60° C., the applied voltage range is 0.4-1.3 V vs. RHE, and the electrocatalytic oxidation reaction time is 0.5 h-300 h.

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