ELECTROCATALYST FOR BIOMASS UPGRADING AND PLASTIC DEGRADATION, PREPARATION METHOD THEREFOR, AND USE THEREOF

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of PCT application No. PCT/CN2023/095893 filed on May 23, 2023, which claims the benefit of Chinese Patent Application No. 202310496089.4 filed on May 5, 2023. The contents of all of the aforementioned applications are incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention belongs to the technical field of electro-catalysis for biomass upgrading and plastic degradation, and particularly relates to an electrocatalyst for biomass upgrading and plastic degradation, a preparation method therefor, and use thereof.

BACKGROUND

Biomass is an important energy source, and the selective catalytic oxidation of biomass-based alcohol-aldehyde molecules is one of the most important reactions in organic synthesis, with wide applications in fine chemical production and other fields. Catalytic oxidation of alcohol-aldehyde compounds is a key pathway for converting carbohydrates into various organic acids and furan chemicals. However, due to the complexity of the reaction system and the multiple reaction pathways, the catalytic mechanism is not yet fully understood. For example, 5-hydroxymethylfurfural (HMF), as an important biomass platform chemical, is widely available and can be directly generated from the dehydration of glucose or fructose. Because it has both alcohol hydroxyl and aldehyde groups, it is considered an ideal model for studying the liquid-phase selective oxidation catalytic mechanism of alcohol and aldehyde compounds (selective activation of carbon-oxygen single bonds and carbon-oxygen double bonds). However, at present, the selective catalytic oxidation of biomass-based alcohols and aldehydes (such as 5-hydroxymethylfurfural) is mainly carried out by thermocatalysis. The reaction inevitably requires high temperature and pressure, noble metal catalysts, and some toxic oxidants, which does not conform to the principles of modern green synthesis. In contrast, electrocatalytic alcohol/aldehyde oxidation offers mild and controllable operating conditions (ambient temperature and pressure), allows for continuous reactions, and is low in cost, making it a promising alternative method for the production of fine chemicals. The selective electrocatalytic oxidation reaction of 5-hydroxymethylfurfural can not only replace the traditional anodic oxygen evolution reaction to reduce cell pressure, but also selectively generate high-value-added products such as 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), 2,5-diformylfuran (DFF), 5-formyl-2-furancarboxylic acid (FFCA), and 2,5-furandicarboxylic acid (FDCA), making it a “two birds with one stone” reaction. A review of numerous literature and patents revealed that there is considerable research on the high-potential HMF oxidation to prepare FDCA (>1 V), mainly focusing on the design of transition metal Co-based and Ni-based catalysts. Unfortunately, the HMF electro-oxidation that occurs on typical nickel-based electrocatalysts such as β-Ni(OH)₂ usually requires a relatively high potential (approximately 1.36 V vs. RHE) for oxidative dehydrogenation to form the active intermediate NiOOH. In addition, the reaction that generates the 6-electron product (FDCA) usually requires a higher voltage than the reactions that generate the 2-electron product (HMFCA) and the 4-electron product (FFCA). In this regard, people have adjusted and optimized nickel hydroxide by introducing noble metals such as Pt, but the reaction still requires a very high voltage (>1.35 V). For example, in the literature: Hunan University, Shuangyin Wang, et al., “Platinum Modulates Redox Properties and 5-Hydroxymethylfurfural Adsorption Kinetics of Ni(OH)₂ for Biomass Upgrading”, Angew. Chem. Int. Ed. 2021(60), a nickel hydroxide-supported Pt nanoparticle catalyst was designed and synthesized by hydrothermal and high-temperature reduction with ethylene glycol. As a three-dimensional structure electrocatalyst with high FDCA selectivity at a high potential (1.40 V), Pt itself cannot be used as an active species because it is oxidized, but it improves the electrocatalytic activity of nickel hydroxide for HMF. There are also reports on the regulation of NiO by Ru, such as Tsinghua University, Haohong Duan, et al., “Selective Electro-oxidation of Biomass-Derived Alcohols to Aldehydes in a Neutral Medium: Promoted Water Dissociation over a Nickel-Oxide-Supported Ruthenium Single-Atom Catalyst”, Angew. Chem. Int. Ed. 2022(61), where nickel hydroxide is generated by hydrothermal treatment and then calcined to nickel oxide. A Ru₁/NiO catalyst is then prepared by impregnation and calcination. The Ru single atom itself does not act as an active species but only provides the *OH species. At a high potential (1.30 V), it promotes the selective oxidation of HMF by the NiO catalyst under neutral conditions. However, no catalysts that can achieve 100% FDCA selectivity at a low potential have been reported so far.

In addition, plastics, especially PET plastics, are a major source of “white pollution”. The mineral water bottles and plastic cans we commonly use in our daily lives are mostly made of PET plastics, the main component of which is polyethylene terephthalate. This polymer is difficult to degrade under natural conditions for hundreds of years. Currently, the world consumes 245 million tons of plastics annually. The current methods for treating PET plastic waste include landfill, incineration, and recycling. Although landfill and incineration are simple, the resulting waste gas and wastewater can cause secondary pollution to the environment. Recycling is currently a more advocated treatment method, but due to the economic costs of recycling and the performance issues of recycled plastics, the current recycling rate is low. Currently, recycling is mainly achieved through physical crushing, heating, and catalytic degradation. This requires catalysts to react under high temperature and high pressure conditions, and product collection is difficult, making automated continuous degradation impossible. However, electrocatalytic plastic degradation offers milder conditions, and the products can be controlled by controlling the potential, enabling automated continuous production. This is an emerging technological means in recent years. The polyester structure of PET enables it to be easily hydrolyzed in the alkaline electrolyte into terephthalic acid and ethylene glycol. For example, ethylene glycol can undergo highly selective electro-oxidation to generate formate. This process holds promise for coupling with electrocatalytic oxidative cracking to prepare high-value chemicals from PET. Therefore, research on the electrocatalytic upcycling of waste PET plastics has broad prospects. For example, Tsinghua University, Haohong Duan, et al., “Electrocatalytic upcycling of polyethylene terephthalate to commodity chemicals and H₂ fuel”, Nature Communications, 2021(12), used non-noble metal cobalt nickel phosphide as a bifunctional electrocatalyst to upcycle waste polyethylene terephthalate (PET) plastics. The waste PET plastics are subjected to electrocatalytic conversion into high-value-added terephthalic acid (PTA), potassium diformate (KDF), and H₂ fuel. However, this technology requires a relatively high potential (approximately 1.36 V vs. RHE) for oxidative dehydrogenation to form active intermediates NiOOH and CoOOH, which determines that the electrocatalyst can only react at a high potential and cannot achieve electrocatalytic conversion at a low potential.

A deep understanding of the relationship between the catalyst structure and its selectivity for activating C—C, C—O, and C═O bonds is a key step in achieving a universal design of efficient catalysts for ultra-low potential biomass upgrading and plastic degradation. Once high selectivity for six-electron products (FDCA) at a low potential is achieved on noble metal-based materials, the high-efficiency hydrogen evolution reaction (HER) at an ultra-low input voltage (<1 V) and the production of high-value-added organic products will be achieved. More importantly, it provides a new solution for rationally designing low-cost, low-voltage, and stable electrolytic cells to convert intermittent electrical energy generated from renewable energy sources.

Therefore, based on the above problems, developing a catalyst and catalytic method for the electrocatalytic selective oxidation of biomass upgrading and plastic degradation with a high catalytic reaction rate, good stability, low costs, energy saving, and environmental protection is of great practical significance.

SUMMARY

The present invention aims to overcome the defects in the prior art and provide an electrocatalyst and catalytic method for the electrocatalytic oxidation of biomass upgrading and plastic degradation that has a high catalytic oxidation reaction rate, high selectivity for corresponding multi-electron products, good CO tolerance, good stability, and strong reproducibility at a low potential (<1.0 V).

In order to solve the technical problems, the present invention adopts the following technical solution:

• • A catalyst for electrocatalytic selective oxidation of biomass upgrading and plastic degradation, using a carbon-based material as a catalyst support, on which multi-component metals and multi-component metal hydroxides are supported to form a supported catalyst with a binary metal interface structure, denoted as NM/TM(OH)₂/C, where NM is one or more of noble metals Pt, Pd, Ru, Au, Rh, Ir, or Ag, and TM is one or more of transition metals Ni, Co, Cu, or Fe, where an NM loading is 0.5 wt % to 35 wt %, and a TM loading is 1 wt % to 30 wt %. The metal loading is obtained by measuring the content of transition metals or heavy metals in the catalyst using ICP-MS.

A preparation method for the catalyst for electrocatalytic selective oxidation of biomass upgrading and plastic degradation, including the following steps:

• • (1) taking a transition metal salt solution, adding a coordinating solvent, stirring, then adding the catalyst support, and stirring;
  • (2) adding an alkaline solution to a solution obtained in step (1) to adjust pH of the solution to 8-14; and carrying out a mechanical stirring reaction at 5° C.-35° C. for 0.5-48 hours;
  • (3) obtaining a sample TM(OH)₂/C, in which a transition metal is supported on the catalyst support, by filtration, washing, centrifugation, and drying;
  • (4) dispersing the sample TM(OH)₂/C obtained in step (3) in one or two noble metal precursor solutions, stirring continuously, carrying out a precipitation reaction at room temperature for 0.5-24 hours, and then obtaining a catalyst NM—O_x/TM(OH)₂/C by filtration, washing, centrifugation, and drying; and
  • (5) obtaining NM/TM(OH)₂/C by in-situ electrochemical reduction of the NM—O_x/TM(OH)₂/C obtained in step (4).

Further, the transition metal in step (1) is one or more of Ni, Co, Cu, or Fe.

Further, the coordinating solvent in step (1) is ethanol, ethylene glycol, aniline, or ethylenediamine.

Further, the catalyst support in step (1) is carbon black, activated carbon, graphene, derivatives of graphene, carbon quantum dots, or carbon nanotubes.

Further, in step (1), the volume ratio of the transition metal salt solution to the coordinating solvent is 9:1.

Further, the alkaline solution in step (2) is a NaOH solution, a sodium bicarbonate solution, a sodium carbonate solution, hydrazine hydrate, or NH₃·H₂O.

Further, the noble metal precursor solution in step (4) is one or more of an aqueous solution containing Pt⁴⁺, Pd²⁺, Ru³⁺, Au³⁺, Rh³⁺, Ir⁴⁺, or Ag⁺.

Further, in step (5), the in-situ electrochemical reduction is carried out by cyclic voltammetry or a potentiostatic method within a reduction potential range of noble metals (e.g., the reduction potential range of Pd is 0-0.6 V vs. RHE).

The catalyst for the electrocatalytic oxidation of biomass upgrading and plastic degradation prepared by the above method is applied to the electro-catalysis of biomass or plastics; in particular, the catalyst can be applied to the electrocatalytic oxidation of 5-hydroxyfurfural, benzyl alcohol, ethylene glycol, glucose, glycerol, and PET at a low potential (<1.0 V).

Specifically, the method for electrocatalytic oxidation of biomass or plastics using the above catalyst is as follows:

• • First, 0.3 M PET plastic is hydrolyzed in 2 M KOH at 60° C. for 18 hours to obtain a PET hydrolysate solution, which is then prepared into a 1 mol/L KOH+1.0 mol/L PET plastic hydrolysate solution (terephthalic acid and ethylene glycol monomers), which is transferred to a three-electrode system (H-type electrolytic cell, with cathodes being a 1 mol/L KOH solution). For biomass upgrading, a different substrate was used; for example, in the selective electro-oxidation of HMF to prepare FDCA, the electrolyte is 1 mol/L KOH+50 mmol/L HMF, carbon paper (1 cm²) is used as a working electrode, platinum foil is used as a counter electrode, and a mercury/mercury oxide electrode (Hg/HgO) is used as a reference electrode. 300 μL of catalyst ink (5 mg/mL, 0.25% Nafion) is taken and dropped onto the surface of the working electrode. Both biomass upgrading and plastic electro-oxidation are carried out at room temperature using an electrochemical workstation (BioLogic EC-Lab).

Compared with the existing technical solutions, the innovations of the technical solution of the present invention lie in that:

According to the present invention, the metal hydroxide supported on the surface of carbon black is prepared by precipitation. A weakly acidic noble metal precursor aqueous solution (pH<7) is then added, and the mixture is stirred to etch the metal hydroxide. The etching of the metal hydroxide leads to the rising the pH of the solution, causing the noble metal to precipitate directionally on the hydroxide surface, thereby preparing a noble metal oxide supported on the ultra-thin hydroxide surface. The noble metal is then subjected to in-situ electrochemical reduction by cyclic voltammetry to form sufficient noble metal/transition metal hydroxide NM/TM(OH)_x interfaces, thereby effectively promoting efficient electrocatalytic oxidation of biomass upgrading and plastic degradation at room temperature. Unlike existing technologies that use hydrothermal methods with reducing agents to prepare noble metal/transition metal hydroxides, in the present invention, first, the metal hydroxide supported on the surface of carbon black is prepared, and directional precipitation and in-situ electrochemical reduction are then carried out, such that precise supporting of noble metals can be achieved at room temperature without adding a reducing agent. Furthermore, the resulting transition metal hydroxide (ultra-thin) is much smaller than transition metal hydroxide nanoparticles prepared by traditional hydrothermal methods. Supporting noble metals onto ultra-thin transition metal hydroxides is an important prerequisite for forming sufficient noble metal/transition metal hydroxide NM/TM(OH)_x interfaces, which cannot be achieved by traditional methods. Thanks to this structure which is different from that of traditional catalysts, the NM/TM(OH)_x designed in the present invention, such as a Pd/Ni(OH)₂/C catalyst, achieves 100% FDCA selectivity in an HMF electrocatalytic reaction at a low voltage (0.6 V), which is the highest selectivity reported at low potential at present. Furthermore, it exhibits good catalyst stability and selectivity after five consecutive electrochemical cycles. According to the present invention, by constructing the binary metal interface structure of NM/TM(OH)₂/C, the electrocatalytic oxidation performance of the catalyst for biomass upgrading and plastic degradation at a low potential (<1.0 V) is significantly improved.

The present invention has the following advantages and beneficial effects:

• • (1) The multi-metal interface structure nanocatalyst NM/TM(OH)₂/C in the present invention can achieve efficient electrocatalytic oxidation of biomass upgrading and plastic degradation at room temperature, thereby improving the selectivity for multi-electron products. For example, the catalyst can achieve approximately 100% selective oxidation of HMF to FDCA at a low voltage (0.6 V).
  • (2) According to the present invention, by constructing the binary metal interface structure of NM/TM(OH)₂/C, the electrocatalytic oxidation performance of the catalyst for biomass upgrading and plastic degradation at a low potential (<1.0 V) is significantly improved. For example, at a low potential of 0.75 V, the HMF oxidation current is as high as 200 mA or more, which can achieve the high-current and efficient electrocatalytic oxidation process for biomass upgrading and plastic degradation.

BRIEF DESCRIPTION OF DRAWINGS

The technical solution of the present invention will be further described in detail below in conjunction with the drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention.

FIG. 1 is a high-resolution transmission electron microscopy image of a Pd/Ni(OH)₂/C bimetallic catalyst in embodiment 1 of the present invention.

FIG. 2 shows the CV test reaction results of catalysts under HMF oxidation at room temperature using cyclic voltammetry in embodiment 2 of the present invention.

FIG. 3 shows the charge-time curve of catalysts under HMF electro-oxidation testing at 0.75 V vs. RHE using a potentiostatic method in embodiment 3 of the present invention.

FIG. 4 shows the sampling detection product distribution results of electrolytes after the HMF electrocatalytic oxidation reaction at different voltages (0.3 V, 0.4 V, 0.5 V, 0.6 V, 0.75 V, and 0.9 V) using catalysts in embodiment 3 of the present invention.

FIG. 5 shows the product distribution results of five consecutive cyclic stability tests of a Pd/Ni(OH)₂/C catalyst at a voltage of 0.75 V vs. RHE in embodiment 3 of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

First, it should be noted that the specific structure, features, and advantages of the present invention will be described in detail below by way of examples. However, all descriptions are for illustrative purposes only and should not be construed as limiting the present invention in any way. Furthermore, any single technical feature described or implied in the embodiments mentioned herein can still be combined or deleted in any way among these technical features (or their equivalents) to obtain more other embodiments of the present invention that may not be directly mentioned herein.

It should be noted that the terms used herein are for the purpose of describing particular implementations only and are not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

It should be noted that, in the absence of conflict, the embodiments in the present application and the features of the embodiments can be combined with each other.

Embodiment 1

Preparation of Ni(OH)₂/C, Pd/Ni(OH)₂/C, and Pd/Ni(OH)₂/C-etching catalysts.

Preparation method of Ni(OH)₂/C: 0.717 g of Ni(NO₃)₂·6H₂O was weighed into a 250 mL Erlenmeyer flask, 12.5 mL of ethanol and 82.5 mL of deionized water were added, and the mixture was stirred at room temperature for 15 minutes; 0.125 g of carbon black was weighed and added into the Erlenmeyer flask, the mixture was sonicated for 15 minutes and then stirred for 60 minutes, the prepared NaOH solution was added to adjust the pH of the solution to 13.5, and the solution in the Erlenmeyer flask was sealed and stirred for 20 hours; the solution was filtered, washed several times with ethanol and deionized water, and placed in a vacuum drying oven for drying at 60° C. for 12 hours, and the product was ground and weighed to obtain Ni(OH)₂/C.

Preparation method of Pd/Ni(OH)₂/C: 0.084 g of Ni(OH)₂/C prepared by the above method was taken into a beaker, deionized water was added to dilute to 200 mL; 5.238 mL of a Na₂PdCl₄·6H₂O solution with a concentration of 19 mg/mL was added dropwise, and the mixture was stirred for 20 hours; the mixture was filtered, washed several times with ethanol and deionized water, and placed into a vacuum drying oven for drying at 60° C. for 12 hours, and the product was ground, subjected to in-situ electrochemical reduction at 0-0.8 V for 200 cycles, scraped off, and dried to obtain Pd/Ni(OH)₂/C.

Preparation method of Pd/Ni(OH)₂/C-etching: 0.035 g of the above Pd/Ni(OH)₂/C catalyst was transferred into a beaker, 25 mL of a dilute nitric acid solution with a concentration of 0.5 mol/L was added, the mixture was stirred mechanically at room temperature for 1.5 hours to remove nickel hydroxide, filtered, washed several times with ethanol and deionized water, and placed in a vacuum drying oven for drying at 60° C. for 12 hours, and the product was ground and weighed to obtain Pd/Ni(OH)₂/C-etching after etching.

FIG. 1 is a transmission electron microscopy image of the Pd/Ni(OH)₂/C bimetallic catalyst. FIG. 1 shows that the lattice fringe spacing of Pd was 0.225 nm, and the Pd in the catalyst had an average particle size of about 2 nm and was supported on the surface of nickel hydroxide without obvious aggregation.

Embodiment 2

Experiments of electrocatalytic oxidation of HMF are carried out using the catalysts prepared in embodiment 1 and commercial Pd/C.

Pd/Ni(OH)₂/C as a catalyst: a 1 mol/L KOH solution was prepared as a catholyte (20 mL), a 1 mol/L KOH+50 mmol/L HMF solution was prepared as an anolyte (20 mL), and they were transferred to a three-electrode system (H-type electrolytic cell); carbon paper (1 cm²) was used as a working electrode, platinum foil was used as a counter electrode, and a mercury/mercury oxide electrode (Hg/HgO) was used as a reference electrode. 300 μL of catalyst ink (5 mg/mL, 0.25% Nafion) was taken and dropped onto the surface of the working electrode. Both biomass upgrading and plastic electro-oxidation were carried out at room temperature using an electrochemical workstation (BioLogic EC-Lab). The reaction results are shown in FIG. 2.

Pd/Ni(OH)₂/C-etching as a catalyst: the operation steps were the same as those for Pd/Ni(OH)₂/C as a catalyst mentioned above, except that Pd/Ni(OH)₂/C was replaced with Pd/Ni(OH)₂/C-etching. The reaction results are shown in FIG. 2.

Ni(OH)₂/C as a catalyst: the operation steps were the same as those for Pd/Ni(OH)₂/C as a catalyst mentioned above, except that Pd/Ni(OH)₂/C was replaced with Ni(OH)₂/C. The reaction results are shown in FIG. 2.

Commercial Pd/C as a catalyst: the operation steps were the same as those for Pd/Ni(OH)₂/C as a catalyst mentioned above, except that Pd/Ni(OH)₂/C was replaced with commercial Pd/C, with a scan rate of 5 mV/s. The reaction results are shown in FIG. 2.

As can be seen from FIG. 2, for the HMF electrocatalytic oxidation reaction, Ni(OH)₂/C did not exhibit reactivity, while the peak current density of the Pd/Ni(OH)₂/C bimetallic catalyst reached 243.6 mA/cm², which was 4.4 times that of the commercial Pd/C catalyst (55.6 mA/cm²). More importantly, the catalytic performance of the single metallic catalyst after etching away nickel hydroxide (Pd/Ni(OH)₂/C-etching) was significantly reduced, with a peak current density dropping to 123.1 mA/cm². This is because the Ni—O—Pd interface is crucial for the HMF electrocatalytic oxidation reaction, and the noble metal/transition metal hydroxide NM/TM(OH)_x interface effectively promotes the efficient electrocatalytic oxidation of biomass upgrading and plastic degradation at room temperature.

Embodiment 3

Constant-voltage product testing of Pd/Ni(OH)₂/C, Pd/Ni(OH)₂/C-etching, and commercial Pd/C catalysts.

The reaction conditions were as follows: a 1 mol/L KOH solution was prepared as a catholyte (20 mL), a 1 mol/L KOH+5 mmol/L HMF solution was prepared as an anolyte (10 mL), and they were transferred to a three-electrode system (H-type electrolytic cell); carbon paper (1 cm²) was used as a working electrode, platinum foil was used as a counter electrode, and a mercury/mercury oxide electrode (Hg/HgO) was used as a reference electrode. 300 μL of catalyst ink (5 mg/mL, 0.25% Nafion) was taken and dropped onto the surface of the working electrode. The tests were carried out at a constant voltage of 0.75 V (vs. RHE) at room temperature using an electrochemical workstation (BioLogic EC-Lab). The reaction results are shown in FIG. 3.

As can be seen from FIG. 3, except for Ni(OH)₂/C (since Ni(OH)₂/C has no reactivity, there are no product performance results), the charge transfer of each catalyst reached its peak after about 5 hours of chronoamperometry under a constant voltage of 0.75 V, at which point the current tended to 0, and Pd/Ni(OH)₂/C had the maximum value in the corresponding charge-time curve; compared with the etched Pd/Ni(OH)₂/C, Ni(OH)₂/C, and commercial Pd/C (10% Pd content) catalysts, the Pd/Ni(OH)₂/C bimetallic catalyst exhibited the highest reactivity.

Embodiment 4

The electrolytes after the HMF electrocatalytic oxidation reaction at different voltages (0.3 V, 0.4 V, 0.5 V, 0.6 V, 0.75 V, and 0.9 V) using the catalysts in embodiment 3 were sampled for detection product distribution.

The product detection conditions were as follows:

Reactions were carried out at different voltages (0.3 V, 0.4 V, 0.5 V, 0.6 V, 0.75 V, and 0.9 V), 50 μL of samples were taken at different coulometric quantities(0 C, 9.65 C, 19.3 C, and 29.95 C), and the samples were diluted to 1 mL with 950 μL of 5 mM ammonium formate aqueous solution (70%)+methanol (30%). Quantitative detection of the products was carried out using high-performance liquid chromatography. After the column pressure was stabilized, detection was carried out using a full-wavelength ultraviolet detector with a diode array. The wavelength (265 nm) with the strongest product response and highest resolution was selected for spectral collection and quantification. Each injection volume was 10 μL. Product data were converted using a standard sample, and statistically analyzed.

The product test results of Pd/Ni(OH)₂/C, Pd/Ni(OH)₂/C-etching, and commercial Pd/C catalysts at different voltages are shown in FIG. 4.

As can be seen from FIG. 4, the products of the reactions of the catalysts at different voltages (0.3 V, 0.4 V, 0.5 V, 0.6 V, 0.75 V, and 0.9 V) differed significantly; the Pd/Ni(OH)₂/C catalyst exhibited approximately 100% FDCA selectivity at 0.75 V, which was significantly improved compared with the etched Pd/Ni(OH)₂/C-etching catalyst (66.3% FDCA selectivity) and the commercial Pd/C catalyst (37.1% FDCA selectivity). Literature review and comparison revealed that the Pd/Ni(OH)₂/C bimetallic catalyst exhibited the highest FDCA product selectivity at a low potential (<1.0 V), not previously reported.

Embodiment 5

Cyclic stability testing and product detection is carried out for Pd/Ni(OH)₂/C.

The stability testing and product detection conditions were as follows: a 1 mol/L KOH solution was prepared as a catholyte (20 mL), a 1 mol/L KOH+5 mmol/L HMF solution was prepared as an anolyte (10 mL), and they were transferred to a three-electrode system (H-type electrolytic cell); carbon paper (1 cm²) was used as a working electrode, platinum foil was used as a counter electrode, and a mercury/mercury oxide electrode (Hg/HgO) was used as a reference electrode. 300 μL of catalyst ink (5 mg/mL, 0.25% Nafion) was taken and dropped onto the surface of the working electrode. Five chronoamperometry tests were carried out at 0.75 V (vs. RHE) at room temperature using an electrochemical workstation (BioLogic EC-Lab), 50 μL of samples were collected at different coulometric quantities (0 C, 9.65 C, 19.3 C, and 29.95 C), and the samples were diluted to 1 mL with 950 μL of 5 mM ammonium formate aqueous solution (70%)+methanol (30%). Quantitative detection of the products was carried out using high-performance liquid chromatography. After the column pressure was stabilized, detection was carried out using a full-wavelength ultraviolet detector with a diode array. The wavelength (265 nm) with the strongest product response and highest resolution was selected for spectral collection and quantification. Each injection volume was 10 μL. The product data from 5 reactions were recorded, converted using a standard sample, and statistically analyzed.

As can be seen from FIG. 5, the products of the five consecutive cycles of the Pd/Ni(OH)₂/C catalyst at a voltage of 0.75 V exhibited little difference, and the selectivity for FDCA was very high, approximately 100%, indicating that the Pd/Ni(OH)₂/C catalyst has good stability and strong repeatability.

Embodiment 6

Preparation of a Pt/Co(OH)₂/C catalyst:

Preparation method of Co(OH)₂/C: 0.065 g of Co(NO₃)₂·6H₂O was weighed into a 250 mL Erlenmeyer flask, 12.5 mL of ethanol and 82.5 mL of deionized water (introducing argon gas for 15 minutes to remove oxygen) were added, and the mixture was stirred at room temperature for 30 minutes; 0.125 g of carbon black was weighed and added into the Erlenmeyer flask, the mixture was sonicated for 30 minutes and then stirred for 60 minutes, the prepared NaOH solution was added to adjust the pH of the solution to 12, and the solution in the Erlenmeyer flask was sealed and stirred for 20 hours; the solution was filtered, washed several times with ethanol and deionized water, and placed in a vacuum drying oven for drying at 60° C. for 12 hours, and the product was ground and weighed to obtain Co(OH)₂/C.

Preparation method of Pt/Co(OH)₂/C: 0.065 g of Co(OH)₂/C prepared by the above method was taken into a beaker, deionized water was added to dilute to 200 mL; 7.5 mL of a H₂PtCl₆·6H₂O solution with a concentration of 20 mg/mL was added dropwise, and the mixture was stirred for 10 hours; the mixture was filtered, washed several times with ethanol and deionized water, and placed into a vacuum drying oven for drying at 60° C. for 24 hours, and the product was ground, subjected to electrochemical reduction at a constant potential (0.75 V vs. RHE) for 200 cycles, scraped off, and dried to obtain Pt/Co(OH)₂/C.

Preparation method of Pt/Co(OH)₂/C-etching: 0.035 g of the above Pt/Co(OH)₂/C was transferred into a beaker, 30 mL of a dilute nitric acid solution with a concentration of 0.5 mol/L was added, the mixture was stirred mechanically at room temperature for 2.0 hours to remove cobalt hydroxide, filtered, washed several times with ethanol and deionized water, and placed in a vacuum drying oven for drying at 60° C. for 24 hours, and the product was ground and weighed to obtain Pt/Co(OH)₂/C-etching after etching.

Embodiment 7

Experiments of electrocatalytic oxidative degradation reaction of plastics is carried out using the catalyst prepared in embodiment 6.

First, 0.3 M PET plastic was hydrolyzed in 2 M KOH at 60° C. for 18 hours to obtain a PET hydrolysate solution, which was then prepared into a 1 mol/L KOH+1.0 mol/L PET hydrolysate solution (terephthalic acid and ethylene glycol monomers), which was transferred to a three-electrode system (H-type electrolytic cell, with cathodes being a 1 mol/L KOH solution). The electrolyte was 1 mol/L KOH+50 mmol/L HMF, carbon paper (1 cm²) was used as a working electrode, platinum foil was used as a counter electrode, and a mercury/mercury oxide electrode (Hg/HgO) was used as a reference electrode. 300 μL of catalyst ink (5 mg/mL, 0.25% Nafion) was taken and dropped onto the surface of the working electrode. Biomass electro-oxidation was carried out at room temperature using an electrochemical workstation (BioLogic EC-Lab).

Embodiment 8

The solution after the electrocatalytic oxidative degradation reaction of plastics in embodiment 7 was sampled for product detection.

The nuclear magnetic detection of the product revealed that ethylene glycol in the PET hydrolysate underwent oxidation at the anode, selectively breaking C—C bonds to generate formate. Further addition of formic acid to the electrolyte and filtration yielded high-purity, high-value-added terephthalic acid. The filtrate was further concentrated and crystallized to obtain high-value-added potassium diformate (KDF). The purity of the product was determined by X-ray powder diffraction and single-crystal diffraction. Studies revealed that different catalysts yielded different test results in the electrocatalytic oxidation degradation reaction of plastics. Compared with the etched Pt/Co(OH)₂/C, Co(OH)₂/C, and commercial Pt/C (20% Pt content) catalysts, the Pt/Co(OH)₂/C bimetallic catalyst exhibited the highest reactivity.

It should be noted that the room temperature in the above embodiments in the present invention refers to a temperature of 15° C.-25° C.; in addition, the atomic ratio of noble metals in the catalyst is obtained by ICP-OES testing and calculation.

In summary, the present invention overcomes the defects of the prior art, and provides a method for constructing a binary metal interface structure of NM/TM(OH)₂/C, achieving a high reaction rate, high selectivity for corresponding multi-electron products, good stability, and strong reproducibility in the electrocatalytic oxidation of biomass upgrading and plastic degradation at a low potential (<1.0 V).

The above embodiments have provided a detailed description of the present invention, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of application of the present invention shall still fall within the patent coverage of the present invention.