Preparation method and application of phosphorus-doped lignin-derived carbon-loaded NiCu alloy material

Abstract

The invention relates to a preparation method and application of a phosphorus-doped lignin-derived carbon-loaded NiCu alloy material. The preparation method comprises the following steps: preparing phosphorized lignin by phosphorizing a plurality of pairs of lignin, taking the phosphorized lignin as a phosphorus source and a carbon source, regulating pH to enable the phosphorized lignin to be coordinated and combined with Ni and Cu ions to form a nickel / copper-lignin-based supramolecular precursor, and then performing high-temperature carbon burning to obtain the nickel / copper-lignin-based supramolecular composite material. The catalyst combines the advantages of a biomass carbon material and transition metals Cu and Ni, is a catalyst with relatively excellent performance, can be widely applied to electrocatalytic conversion of glycerol, furfural, glucose and other biomass micromolecules into high-value chemicals, and particularly has an excellent effect on conversion of glycerol into a high-value product dihydroxyacetone. The construction of a P-C structure on the carrier is beneficial to the local enrichment of active oxygen groups, the generation of metal active sites is promoted, the oxidation rate of glycerol is accelerated, and NiCu alloying obviously improves the selectivity of dihydroxyacetone. The catalyst is stable in effect, rich in resources and low in price.

Description

Technical Field

[0001] This invention belongs to the technical field of biomass materials and electrocatalytic materials, and particularly relates to a phosphorus-doped lignin-derived carbon-supported NiCu alloy material, its preparation method, and its application. Background Technology

[0002] With the increasingly severe energy crisis and environmental pollution caused by the overuse of fossil fuels, the development and utilization of clean and renewable energy has become an urgent priority. Biomass, as an abundant and renewable source of hydrocarbons, can effectively alleviate environmental pressure and solve the problem of renewable resource shortages by converting its derivatives into high-value chemicals. Glycerin, a byproduct of biodiesel production, is listed as one of the top ten biomass-based platform compounds and has significant value-added potential. The rapid development of the biodiesel industry has led to a surplus of glycerin. Due to its low price, converting it into high-value chemicals has become an efficient way to utilize this surplus glycerin. Among many high-value chemicals, dihydroxyacetone (DHA) has attracted much attention due to its widespread use in the cosmetics, pharmaceutical, and food industries, and as a raw material for important industrial products such as lactic acid. Furthermore, the market price of DHA is much higher than that of glycerin, making the production of DHA from glycerin a highly attractive production route. However, due to its inherent instability, the catalytic conversion of DHA usually takes place in a relatively mild environment, resulting in a lower number of active sites on the transition metal catalyst, insufficient kinetics of the glycerol oxidation reaction, and low selectivity due to the high activation energy of the secondary hydroxyl group. Therefore, developing catalysts for the efficient production of DHA under mild conditions is currently a research hotspot. Biomass carbon materials, with their tunable properties and excellent electrical conductivity, have attracted increasing attention in the field of catalysis in recent years.

[0003] Lignin is an abundant, renewable natural resource derived from lignin cellulose. As the second largest natural organic polymer after cellulose, it is considered a high-quality carbon source for preparing functional carbon materials. Lignin has a carbon content as high as 60% and is rich in various functional groups. These functional groups can serve as reaction sites for grafting modification, such as demethylation and polyhydroxylation, effectively increasing the number of oxygen-containing functional groups (such as phenolic hydroxyl groups) in lignin. They can also coordinate with transition metal ions to form metal-lignin-based supramolecular structures, thereby effectively improving electrocatalytic performance. Ni and Cu-based materials, in particular, have exhibited extremely high catalytic activity and are gradually replacing high-cost precious metals in the field of catalysis.

[0004] For catalytic materials, increasing the number of active sites is crucial, and introducing Lewis acid sites into catalytic materials can effectively promote the formation of active sites. Constructing Lewis acid sites on a support can enrich oxygen-containing active groups at the reaction interface, increasing the number of active sites and promoting catalytic reactions. Furthermore, alloying specific metals between metal sites on the support can optimize the electronic structure and alter the adsorption behavior of the sites, thereby improving the selectivity of single products. These advantages make the introduction of Lewis acid sites and alloying important strategies for designing efficient, stable, and low-cost electrocatalysts. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects and shortcomings of existing technologies, thereby providing a phosphorus-doped lignin-derived carbon-supported NiCu alloy material, its preparation method, and its application. Phosphate-modified lignin is obtained by phosphating lignin, and the modified lignin is then coordinated with Cu and Ni ions to form a CuNi-lignin supramolecular precursor, which is prepared by high-temperature carbonization. The phosphorus-doped lignin-derived carbon-supported NiCu alloy material combines the advantages of heteroatom-doped biomass carbon support and bimetallic alloying, making it a relatively high-performance catalyst. It can be widely used in the electrocatalytic conversion of small biomass molecules such as glycerol, furfural, and glucose into high-value chemicals, especially showing excellent results in the conversion of glycerol into the high-value product dihydroxyacetone. The construction of the PC structure on the support facilitates the local enrichment of active oxygen groups, promotes the generation of metal active sites, and accelerates the oxidation rate of glycerol, while NiCu alloying significantly improves the selectivity for dihydroxyacetone.

[0006] To achieve the above objectives, the present invention is accomplished by the following means: The first aspect of this invention provides a method for preparing phosphorus-doped lignin-derived carbon-supported NiCu alloy materials, comprising the following steps: (1) Dissolve lignin in an organic solvent, add 4-dimethylaminopyridine and triethylamine to react; after the reaction is complete, add phosphating reagent to react further to obtain phosphated lignin, wash and dry it; (2) Dissolve the phospholignin obtained in step (1) in an alkaline solution, add nickel salt and copper salt and stir thoroughly to form a mixed solution, adjust the pH of the mixed solution, and then carry out a hydrothermal reaction. After the reaction is completed, dry to obtain nickel / copper-lignin-based supramolecular precursor. (3) The nickel / copper-lignin-based supramolecular precursor obtained in step (2) is calcined at high temperature, and then washed with water and dried to obtain the final product.

[0007] Preferably, the lignin in step (1) is selected from one or more of enzymatically hydrolyzed lignin, alkali lignin, sulfite-processed lignin, organic solvent lignin, and lignin sulfonate; most preferably, the lignin is selected from alkali lignin.

[0008] Preferably, the organic solvent in step (1) is selected from one or more of tetrahydrofuran, chloroform, methanol, acetone, and ethanol.

[0009] Preferably, the phosphating agent in step (1) is selected from one or more of diphenylphosphonic chloride, diphenylphosphine chloride, di-tert-butylphosphine chloride and dicyclohexylphosphine chloride. Most preferably, the phosphating agent is selected from di-tert-butylphosphine chloride.

[0010] Preferably, in step (1), the mass concentration of 4-dimethylaminopyridine in the mixed solution is 0.01-0.1 g / mL, the volume concentration of triethylamine is 0.05-0.5 vt, and the mass concentration of the phosphating agent is 0.01-0.5 g / mL; most preferably, the mass concentration of 4-dimethylaminopyridine in the mixed solution is 0.0183 g / mL, the volume concentration of triethylamine is 0.11 vt, and the mass concentration of the phosphating agent is 0.1085 g / mL.

[0011] Preferably, in step (1), the reaction temperature of adding 4-dimethylaminopyridine and triethylamine is 25-50℃ and the reaction time is 0.5-3h; most preferably, the reaction temperature is 25℃ and the reaction time is 1h.

[0012] Preferably, the reaction temperature for adding the phosphating agent in step (1) is 25-50℃ and the reaction time is 0.5-3h; most preferably, the reaction temperature is 25℃ and the reaction time is 1h.

[0013] Preferably, the washing in step (1) specifically involves washing with ethyl acetate.

[0014] Preferably, the alkaline solution in step (2) is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia solution, and sodium carbonate solution; more preferably, the alkaline solution is selected from sodium hydroxide solution; most preferably, the concentration of the sodium hydroxide solution is 0.1-1 wt%.

[0015] Preferably, in step (2), one or more of ammonia, sodium carbonate, potassium hydroxide, and sodium hydroxide are used to adjust the pH to 6-10; most preferably, sodium hydroxide is used to adjust the pH to 8.

[0016] Preferably, the temperature of the hydrothermal reaction in step (2) is 90-200℃ and the time is 2-24h; most preferably, the temperature of the hydrothermal reaction is 180℃ and the time is 8h.

[0017] Preferably, the copper salt in step (2) is selected from one or more of copper chloride, copper nitrate, copper sulfate, and copper acetate; most preferably, the copper salt is selected from copper chloride.

[0018] Preferably, the nickel salt in step (2) is selected from one or more of nickel chloride hexahydrate, nickel nitrate, nickel sulfate, and nickel acetate; most preferably, the nickel salt is selected from nickel chloride hexahydrate.

[0019] Preferably, the total concentration of copper and nickel in the mixed solution in step (2) is 0.1-1 mmol / mL; most preferably, the concentration is 0.2 mmol / mL.

[0020] Preferably, the molar ratio of copper to nickel in the mixed solution in step (2) is 1:1-15; most preferably, the molar ratio of copper to nickel is 1:4.

[0021] Preferably, the high-temperature charcoal burning temperature in step (3) is 600-1000℃, the heating rate is 0.5-5℃ / min, and the time is 1-4h; most preferably, the high-temperature charcoal burning temperature is 800℃, the heating rate is 5℃ / min, and the time is 2h.

[0022] Preferably, the high-temperature charring in step (3) is optionally carried out under a protective gas atmosphere.

[0023] Preferably, the protective gas is selected from one or more of hydrogen, nitrogen, and argon; most preferably, the protective gas is nitrogen.

[0024] Preferably, the lignin may be modified before step (1); the modification is selected from one or more of demethylation modification and polyhydroxylation modification.

[0025] Preferably, the demethylation modification includes the following steps: dissolving lignin raw material in lithium bromide aqueous solution, adding hydrobromic acid, stirring evenly and heating to react; after the reaction is completed, collecting the product, washing and drying to obtain demethylated lignin.

[0026] Preferably, the concentration of the lithium bromide aqueous solution is 1-2 g / mL; most preferably, the concentration of the lithium bromide aqueous solution is 1.4-1.7 mg / mL.

[0027] Preferably, the mass-to-volume ratio (g:mL) of lignin to hydrobromic acid is 1:1-3; most preferably, the mass-to-volume ratio (g:mL) of lignin to hydrobromic acid is 1:1.5-2.5. For example, when the mass-to-volume ratio of lignin to hydrobromic acid is 1:1.8, if the amount of lignin added is 5g, then the amount of hydrobromic acid added is 9mL.

[0028] Preferably, during the demethylation modification process, the lignin raw material is selected from one or more of lignin and polyhydroxylated lignin.

[0029] Preferably, the lignin is selected from one or more of enzymatically hydrolyzed lignin, alkali lignin, sulfite-processed lignin, organic solvent lignin, and lignin sulfonate; most preferably, the lignin is selected from alkali lignin.

[0030] Preferably, the heating reaction is carried out at a temperature of 90-100°C for 1-5 hours; most preferably, the heating reaction is carried out at a temperature of 100°C for 4 hours.

[0031] Preferably, the washing process involves using deionized water.

[0032] Preferably, the polyhydroxylation modification includes the following steps: dissolving lignin raw material in sodium hydroxide solution, adding ferric hydroxide and hydrogen peroxide sequentially, and heating to react; after the reaction is completed, adjusting the pH of the solution to obtain a precipitate, washing and drying to obtain polyhydroxylated lignin.

[0033] Preferably, in the polyhydroxylation modification process, the lignin raw material is selected from one or more of lignin and polyhydroxylated lignin.

[0034] Preferably, the lignin is selected from one or more of enzymatically hydrolyzed lignin, alkali lignin, sulfite-processed lignin, organic solvent lignin, and lignin sulfonate; most preferably, the lignin is selected from alkali lignin.

[0035] Preferably, the sodium hydroxide solution has a mass fraction of 1-10 wt%; most preferably, the sodium hydroxide solution has a mass fraction of 5 wt%.

[0036] Preferably, the mass concentration of ferric hydroxide in the mixed solution is 0.5-5 mg / mL, and the mass concentration of hydrogen peroxide is 0.01-0.05 g / mL; most preferably, the mass concentration of ferric hydroxide in the mixed solution is 1.2 mg / mL, and the mass concentration of hydrogen peroxide is 0.048 g / mL.

[0037] Preferably, the heating reaction is carried out at a temperature of 40-90°C for 0.5-3 hours; most preferably, the heating reaction is carried out at a temperature of 60°C for 1 hour.

[0038] Preferably, the pH of the solution is adjusted to 3-7; most preferably, the pH of the solution is adjusted to 3.

[0039] Preferably, the washing process involves using deionized water.

[0040] A second aspect of the present invention provides a phosphorus-doped lignin-derived carbon-supported NiCu alloy material prepared according to the above preparation method.

[0041] The third aspect of this invention provides the application of the above-mentioned phosphorus-doped lignin-derived carbon-supported NiCu alloy material in biomass electrocatalytic conversion.

[0042] Preferably, the biomass is selected from one or more of glycerol, furfural, and glucose.

[0043] This invention obtains phosphinized lignin through multi-step modification of lignin, enabling the modified lignin to coordinate with Cu and Ni ions to form a CuNi-lignin supramolecular precursor, which is then prepared by high-temperature carbonization. The phosphorus-doped lignin-derived carbon-supported NiCu alloy material combines the advantages of heteroatom-doped biomass carbon support and bimetallic alloying, making it a relatively high-performance catalyst. It can be widely used in the electrocatalytic conversion of small biomass molecules such as glycerol, furfural, and glucose into high-value chemicals, especially showing excellent results in the conversion of glycerol into the high-value product dihydroxyacetone. The construction of the PC structure on the support facilitates the local enrichment of active oxygen groups, promotes the generation of metal active sites, and accelerates the oxidation rate of glycerol, while NiCu alloying significantly improves the selectivity for dihydroxyacetone.

[0044] This invention modifies lignin in multiple steps by using oxygen-containing functional groups as grafting sites to prepare phosphinized lignin. Then, using phosphinized lignin as a carbon and phosphorus source, it precisely coordinates with metal ions Cu and Ni to form CuNi-lignin supramolecular structures. Finally, the CuNi-lignin precursor undergoes complexation precipitation self-assembly treatment and is then carbonized in situ in a tube furnace to prepare phosphorus-doped lignin-derived carbon-supported NiCu alloy materials, thereby improving the electrochemical activity of the CuNi-lignin supramolecular complex. During the carbonization process of the CuNi-lignin supramolecular complex precursor, the interaction between Cu and Ni ions and lignin molecules not only creates pores in situ for the lignin carbon material, but also, combined with the synergistic catalytic effect between metals, yields metal-doped modified lignin-based carbon materials. The doped sites can serve as catalytically active sites, significantly enhancing their electrocatalytic performance.

[0045] Compared with existing technologies, the present invention has the following advantages: (1) This invention directly utilizes the waste lignin extracted from papermaking black liquor, and forms a highly efficient electrocatalyst through self-assembly and in-situ carbonization, thereby making high-value use of industrial waste and effectively reducing the pollution of the environment caused by papermaking waste liquid discharged in the industrial papermaking industry.

[0046] (2) This invention utilizes the characteristic that lignin contains abundant oxygen-containing functional groups to prepare phosphin-modified lignin by phosphorylation through P doping. After in-situ carbonization, Lewis acid sites of PC are generated on the surface of the carbon support, which can enrich local oxygen active groups during the catalytic reaction, promote the generation of metal active sites, and improve the catalytic reaction efficiency.

[0047] (3) Based on the coordination characteristics between Cu and Ni ions and lignin, an in-situ carbonization process forms a NiCu alloy structure, which significantly improves the selectivity of the catalyst for a single product. This structure is stable, efficient, abundant in resources, and inexpensive, and can be widely applied to the electrocatalytic conversion of small biomass molecules such as glycerol, furfural, and glucose into high-value chemicals. It is particularly effective in converting glycerol into the high-value product dihydroxyacetone. The construction of the PC structure on the support facilitates the local enrichment of active oxygen groups, promotes the generation of metal active sites, and accelerates the oxidation rate of glycerol. Furthermore, NiCu alloying significantly improves the selectivity for dihydroxyacetone. Attached Figure Description

[0048] Figure 1 The infrared spectra of the demethylated lignin, polyhydroxylated lignin, and phosphine prepared in Example 1 are shown.

[0049] Figure 2 The nuclear magnetic resonance 31P spectrum of the phospholignin prepared in Example 1.

[0050] Figure 3 The image shows the morphology of the phosphorus-doped lignin-derived carbon-supported NiCu alloy material prepared in Example 1.

[0051] Figure 4 The images show the XRD patterns of the alloy materials prepared in Examples 1-4 and Comparative Example 1.

[0052] Figure 5 Linear sweep voltammetric curves of the alloy materials GOR prepared in Examples 1-4 and Comparative Example 1 are shown.

[0053] Figure 6 Tafel graphs of the alloy materials GOR prepared in Examples 1-4 and Comparative Example 1.

[0054] Figure 7 The images show the XRD patterns of the phosphorus-doped lignin-derived carbon-supported NiCu alloy materials prepared in Examples 5-7.

[0055] Figure 8 Linear sweep voltammetric curves of GOR, the phosphorus-doped lignin-derived carbon-supported NiCu alloy material prepared in Examples 1 and 5-7.

[0056] Figure 9 Tafel graphs of the phosphorus-doped lignin-derived carbon-supported NiCu alloy material GOR prepared in Examples 1 and 5-7.

[0057] Figure 10 The XRD patterns are those of the phosphorus-doped lignin-derived carbon-supported metal materials prepared in Examples 8-9 and Comparative Examples 2-3.

[0058] Figure 11 Linear sweep voltammetry curves of the phosphorus-doped lignin-derived carbon-supported metal materials GOR prepared in Examples 1, 8-9, and Comparative Examples 2-3.

[0059] Figure 12 Tafel graphs of phosphorus-doped lignin-derived carbon-supported monometallic materials GOR prepared in Examples 1, 8-9, and Comparative Examples 2-3.

[0060] Figure 13 The XRD patterns are those of the phosphorus-doped lignin-derived carbon bimetallic materials prepared in Comparative Examples 4-6.

[0061] Figure 14 The linear sweep voltammetric curve of glucose oxidation of the phosphorus-doped lignin-derived carbon-supported NiCu alloy material prepared in Example 1 is shown.

[0062] Figure 15 The linear sweep voltammetric curve of furfural oxidation of the phosphorus-doped lignin-derived carbon-supported NiCu alloy material prepared in Example 1 is shown. Detailed Implementation

[0063] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0064] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0065] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared by existing methods. The lignin used in the embodiments and comparative examples of this invention is alkali lignin (AL) as an example. It should be understood that lignin is only used as a raw material to provide a carbon source, and its specific type has no significant impact on the properties of the finished catalyst. When other types of lignin are used for catalyst preparation, such as enzymatically hydrolyzed lignin, sulfite-processed lignin, or lignin sulfonates, the resulting catalyst performance is not significantly different from that of alkali lignin, and therefore will not be listed here.

[0066] Example 1 A method for preparing a phosphorus-doped lignin-derived carbon-supported NiCu alloy material includes the following steps: (1) Add 61g LiBr and 39g deionized water to a round-bottom flask and stir thoroughly to dissolve completely; then add 5g alkali lignin and 10mL HBr; heat the mixture to 100℃ and carry out a reflux reaction in an oil bath for 4h; after the reaction is completed, cool the mixture to room temperature and filter it through a glass Buchner funnel; wash the obtained product repeatedly with deionized water until the filtrate is neutral, and finally freeze-dry to obtain demethylated lignin.

[0067] (2) Take 2g of the demethylated lignin obtained in step (1) and add it to 50mL of deionized water. Dissolve it in deionized water and adjust the pH to 8 with sodium hydroxide. Add 60mg Fe(OH)3 and 2.4g H2O2 to the beaker in sequence and react at 60℃ for 1h. Then filter to remove Fe(OH)3, add dilute hydrochloric acid to the filtrate to adjust the pH to 3 to obtain a precipitate. Centrifuge to collect the precipitate, wash the precipitate with deionized water until the filtrate is neutral, and freeze dry to obtain polyhydroxylated lignin.

[0068] (3) Dissolve 3g of the polyhydroxylated lignin obtained in step (2) in a three-necked flask and dissolve it with 60mL of tetrahydrofuran; then add 1.1g of 4-dimethylaminopyridine and 5.5mL of triethylamine and react at 25℃ for 1h; after the reaction is completed, add 6.51g of t-Bu2PCl dropwise and react at 25℃ for 1h; after the reaction is completed, centrifuge to collect the solid and wash it with ethyl acetate until the fluorescence of the supernatant disappears; dry it in a vacuum drying oven at 60℃ to obtain phosphinized lignin.

[0069] (4) Take 1g of the phospholignin obtained in step (3) and dissolve it in a 0.4wt% NaOH solution. Add 1.896g NiCl2·6H2O and 0.272g CuCl2 and mix and stir evenly. Add sodium hydroxide solution to adjust the pH of the mixed solution to 8 and stir for 60min to carry out coordination. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h. After the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain CuNi-lignin-based supramolecular precursor.

[0070] (5) 1g of CuNi-lignin-based supramolecular precursor obtained in step (4) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain phosphorus-doped lignin-derived carbon-supported NiCu alloy material.

[0071] Example 2 A method for preparing a phosphorus-doped lignin-derived carbon-supported NiCu alloy material includes the following steps: (1) Add 61g LiBr and 39g deionized water to a round-bottom flask and stir thoroughly to dissolve completely; then add 5g alkali lignin and 10mL HBr; heat the mixture to 100℃ and carry out a reflux reaction in an oil bath for 4h; after the reaction is completed, cool the mixture to room temperature and filter it through a glass Buchner funnel; wash the obtained product repeatedly with deionized water until the filtrate is neutral, and finally freeze-dry to obtain demethylated lignin.

[0072] (2) Dissolve 3g of the demethylated lignin obtained in step (1) in a three-necked flask and dissolve it with 60mL of tetrahydrofuran; then add 1.1g of 4-dimethylaminopyridine and 5.5mL of triethylamine and react at 25℃ for 1h; after the reaction is completed, add 6.51g of t-Bu2PCl dropwise and react at 25℃ for 1h; after the reaction is completed, centrifuge to collect the solid and wash it with ethyl acetate until the fluorescence of the supernatant disappears; dry it in a vacuum drying oven at 60℃ to obtain phospholignin.

[0073] (4) Take 1g of the phospholignin obtained in step (2) and dissolve it in a 0.4wt% NaOH solution. Add 1.896g NiCl2·6H2O and 0.272g CuCl2 and mix and stir evenly. Add sodium hydroxide solution dropwise to adjust the pH of the mixed solution to 8 and stir for 60min to carry out coordination. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h. After the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain CuNi-lignin-based supramolecular precursor.

[0074] (4) 1g of CuNi-lignin-based supramolecular precursor obtained in step (3) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain phosphorus-doped lignin-derived carbon-supported NiCu alloy material.

[0075] Example 3 A method for preparing a phosphorus-doped lignin-derived carbon-supported NiCu alloy material includes the following steps: (1) Take 2g of alkali lignin and add it to a 50mL beaker. Dissolve it with deionized water and adjust the pH to 8 with sodium hydroxide. Add 60mg of Fe(OH)3 and 2.4g of H2O2 to the beaker in sequence and react at 60℃ for 1h. Then filter to remove Fe(OH)3, add dilute hydrochloric acid to the filtrate to adjust the pH to 3 to obtain a precipitate. Centrifuge to collect the precipitate, wash the precipitate with deionized water until the filtrate is neutral, and freeze dry to obtain polyhydroxylated lignin.

[0076] (2) Dissolve 3g of the polyhydroxylated lignin obtained in step (1) in a three-necked flask and dissolve it with 60mL of tetrahydrofuran; then add 1.1g of 4-dimethylaminopyridine and 5.5mL of triethylamine and react at 25℃ for 1h; after the reaction is completed, add 6.51g of t-Bu2PCl dropwise and react at 25℃ for 1h; after the reaction is completed, centrifuge to collect the solid and wash it with ethyl acetate until the fluorescence of the supernatant disappears; dry it in a vacuum drying oven at 60℃ to obtain phosphinized lignin.

[0077] (3) Take 1g of the phospholignin obtained in step (2) and dissolve it in a 0.4wt% NaOH solution. Add 1.896g NiCl2·6H2O and 0.272g CuCl2 and mix and stir evenly. Add sodium hydroxide solution dropwise to adjust the pH of the mixed solution to 8 and stir for 60min to carry out coordination. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h. After the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain CuNi-lignin-based supramolecular precursor.

[0078] (4) 1g of CuNi-lignin-based supramolecular precursor obtained in step (3) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain phosphorus-doped lignin-derived carbon-supported NiCu alloy material.

[0079] Example 4 A method for preparing a phosphorus-doped lignin-derived carbon-supported NiCu alloy material includes the following steps: (1) Dissolve 3g of alkali lignin in a three-necked flask and dissolve it with 60mL of tetrahydrofuran; then add 1.1g of 4-dimethylaminopyridine and 5.5mL of triethylamine and react at 25℃ for 1h; after the reaction is completed, add 6.51g of t-Bu2PCl dropwise and react at 25℃ for 1h; after the reaction is completed, centrifuge to collect the solid and wash it with ethyl acetate until the fluorescence of the supernatant disappears; dry it in a vacuum drying oven at 60℃ to obtain phospholignin.

[0080] (2) Take 1g of the phospholignin obtained in step (1) and dissolve it in a 0.4wt% NaOH solution. Add 1.896g NiCl2·6H2O and 0.272g CuCl2 and mix and stir evenly. Add sodium hydroxide solution dropwise to adjust the pH of the mixed solution to 8 and stir for 60min to carry out coordination. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h. After the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain CuNi-lignin-based supramolecular precursor.

[0081] (3) 1g of CuNi-lignin-based supramolecular precursor obtained in step (2) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain phosphorus-doped lignin-derived carbon-supported NiCu alloy material.

[0082] Examples 5-9 The preparation was carried out according to the method in Example 1, with only some conditions adjusted. In Example 5, diphenylphosphonic chloride was used as the phosphinizing agent; in Example 6, diphenylphosphine chloride was used as the phosphinizing agent; in Example 7, dicyclohexylphosphine chloride was used as the phosphinizing agent; in Example 8, the molar ratio of Ni to Cu was 1:4; and in Example 9, the molar ratio of Ni to Cu was 1:1.

[0083] Comparative Example 1 A method for preparing a lignin-derived carbon-supported NiCu alloy material includes the following steps: (1) Dissolve 1g of alkali lignin in a 0.4wt% NaOH solution, add 1.896g NiCl2·6H2O and 0.272g CuCl2, mix and stir evenly, add sodium hydroxide solution to adjust the pH of the mixed solution to 8, stir for 60min to carry out coordination; then transfer to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h; after the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze, and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain CuNi-lignin-based supramolecular precursor.

[0084] (2) 1g of CuNi-lignin-based supramolecular precursor obtained in step (1) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain lignin-derived carbon-supported NiCu alloy material.

[0085] Comparative Example 2 A method for preparing a phosphorus-doped lignin-derived carbon-supported Ni material includes the following steps: (1) Add 61g LiBr and 39g deionized water to a round-bottom flask and stir thoroughly to dissolve completely; then add 5g alkali lignin and 10mL HBr; heat the mixture to 100℃ and carry out a reflux reaction in an oil bath for 4h; after the reaction is completed, cool the mixture to room temperature and filter it through a glass Buchner funnel; wash the obtained product repeatedly with deionized water until the filtrate is neutral, and finally freeze-dry to obtain demethylated lignin.

[0086] (2) Take 2g of the demethylated lignin obtained in step (1) and add it to a 50mL beaker. Dissolve it with deionized water and adjust the pH to 8 with sodium hydroxide. Add 60mg Fe(OH)3 and 2.4g H2O2 to the beaker in sequence and react at 60℃ for 1h. Then filter to remove Fe(OH)3, add dilute hydrochloric acid to the filtrate to adjust the pH to 3 to obtain a precipitate. Centrifuge to collect the precipitate, wash the precipitate with deionized water until the filtrate is neutral, and freeze dry to obtain polyhydroxylated lignin.

[0087] (3) Dissolve 3g of the polyhydroxylated lignin obtained in step (2) in a three-necked flask and dissolve it with 60mL of tetrahydrofuran; then add 1.1g of 4-dimethylaminopyridine and 5.5mL of triethylamine and react at 25℃ for 1h; after the reaction is completed, add 6.51g of t-Bu2PCl dropwise and react at 25℃ for 1h; after the reaction is completed, centrifuge to collect the solid and wash it with ethyl acetate until the fluorescence of the supernatant disappears; dry it in a vacuum drying oven at 60℃ to obtain phosphinized lignin.

[0088] (4) Take 1g of the phospholignin obtained in step (3) and dissolve it in a 0.4wt% NaOH solution. Add 2.37g of NiCl2·6H2O and mix and stir evenly. Add sodium hydroxide solution dropwise to adjust the pH of the mixed solution to 8 and stir for 60min to carry out coordination. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h. After the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze, and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain the Ni-lignin-based supramolecular precursor.

[0089] (5) 1g of the Ni-lignin-based supramolecular precursor obtained in step (4) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain phosphorus-doped lignin-derived carbon-supported Ni material.

[0090] Comparative Example 3 A method for preparing a phosphorus-doped lignin-derived carbon-supported Cu material includes the following steps: (1) Add 61g LiBr and 39g deionized water to a round-bottom flask and stir thoroughly to dissolve completely; then add 5g alkali lignin and 10mL HBr; heat the mixture to 100℃ and carry out a reflux reaction in an oil bath for 4h; after the reaction is completed, cool the mixture to room temperature and filter it through a glass Buchner funnel; wash the obtained product repeatedly with deionized water until the filtrate is neutral, and finally freeze-dry to obtain demethylated lignin.

[0091] (2) Take 2g of the demethylated lignin obtained in step (1) and add it to a 50mL beaker. Dissolve it with deionized water and adjust the pH to 8 with sodium hydroxide. Add 60mg Fe(OH)3 and 2.4g H2O2 to the beaker in sequence and react at 60℃ for 1h. Then filter to remove Fe(OH)3, add dilute hydrochloric acid to the filtrate to adjust the pH to 3 to obtain a precipitate. Centrifuge to collect the precipitate, wash the precipitate with deionized water until the filtrate is neutral, and freeze dry to obtain polyhydroxylated lignin.

[0092] (3) Dissolve 3g of the polyhydroxylated lignin obtained in step (2) in a three-necked flask and dissolve it with 60mL of tetrahydrofuran; then add 1.1g of 4-dimethylaminopyridine and 5.5mL of triethylamine and react at 25℃ for 1h; after the reaction is completed, add 6.51g of t-Bu2PCl dropwise and react at 25℃ for 1h; after the reaction is completed, centrifuge to collect the solid and wash it with ethyl acetate until the fluorescence of the supernatant disappears; dry it in a vacuum drying oven at 60℃ to obtain phosphinized lignin.

[0093] (4) Take 1g of the phospholignin obtained in step (3) and dissolve it in a 0.4wt% NaOH solution. Add 1.36g of CuCl2 and mix and stir evenly. Add sodium hydroxide solution dropwise to adjust the pH of the mixed solution to 8 and stir for 60min to carry out coordination. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h. After the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze, and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain Cu-lignin-based supramolecular precursor.

[0094] (5) 1g of Cu-lignin-based supramolecular precursor obtained in step (4) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain phosphorus-doped lignin-derived carbon-supported Cu material.

[0095] Comparative Example 4 A method for preparing a phosphorus-doped lignin-derived carbon-supported NiFe alloy material includes the following steps: (1) Add 61g LiBr and 39g deionized water to a round-bottom flask and stir thoroughly to dissolve completely; then add 5g alkali lignin and 10mL HBr; heat the mixture to 100℃ and carry out a reflux reaction in an oil bath for 4h; after the reaction is completed, cool the mixture to room temperature and filter it through a glass Buchner funnel; wash the obtained product repeatedly with deionized water until the filtrate is neutral, and finally freeze-dry to obtain demethylated lignin.

[0096] (2) Take 2g of the demethylated lignin obtained in step (1) and add it to a 50mL beaker. Dissolve it with deionized water and adjust the pH to 8 with sodium hydroxide. Add 60mg Fe(OH)3 and 2.4g H2O2 to the beaker in sequence and react at 60℃ for 1h. Then filter to remove Fe(OH)3, add dilute hydrochloric acid to the filtrate to adjust the pH to 3 to obtain a precipitate. Centrifuge to collect the precipitate, wash the precipitate with deionized water until the filtrate is neutral, and freeze dry to obtain polyhydroxylated lignin.

[0097] (3) Dissolve 3g of the polyhydroxylated lignin obtained in step (2) in a three-necked flask and dissolve it with 60mL of tetrahydrofuran; then add 1.1g of 4-dimethylaminopyridine and 5.5mL of triethylamine and react at 25℃ for 1h; after the reaction is completed, add 6.51g of t-Bu2PCl dropwise and react at 25℃ for 1h; after the reaction is completed, centrifuge to collect the solid and wash it with ethyl acetate until the fluorescence of the supernatant disappears; dry it in a vacuum drying oven at 60℃ to obtain phosphinized lignin.

[0098] (4) Take 1g of the phospholignin obtained in step (3) and dissolve it in a 0.4wt% NaOH solution. Add 1.896g NiCl2·6H2O and 0.328g FeCl3 and mix and stir evenly. Add sodium hydroxide solution dropwise to adjust the pH of the mixed solution to 8 and stir for 60min to carry out coordination. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h. After the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain the NiFe-lignin-based supramolecular precursor.

[0099] (5) 1g of the NiFe-lignin-based supramolecular precursor obtained in step (4) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain phosphorus-doped lignin-derived carbon-supported NiFe material.

[0100] Comparative Example 5 A method for preparing a phosphorus-doped lignin-derived carbon-supported NiCo alloy material includes the following steps: (1) Add 61g LiBr and 39g deionized water to a round-bottom flask and stir thoroughly to dissolve completely; then add 5g alkali lignin and 10mL HBr; heat the mixture to 100℃ and carry out a reflux reaction in an oil bath for 4h; after the reaction is completed, cool the mixture to room temperature and filter it through a glass Buchner funnel; wash the obtained product repeatedly with deionized water until the filtrate is neutral, and finally freeze-dry to obtain demethylated lignin.

[0101] (2) Take 2g of the demethylated lignin obtained in step (1) and add it to a 50mL beaker. Dissolve it with deionized water and adjust the pH to 8 with sodium hydroxide. Add 60mg Fe(OH)3 and 2.4g H2O2 to the beaker in sequence and react at 60℃ for 1h. Then filter to remove Fe(OH)3, add dilute hydrochloric acid to the filtrate to adjust the pH to 3 to obtain a precipitate. Centrifuge to collect the precipitate, wash the precipitate with deionized water until the filtrate is neutral, and freeze dry to obtain polyhydroxylated lignin.

[0102] (3) Dissolve 3g of the polyhydroxylated lignin obtained in step (2) in a three-necked flask and dissolve it with 60mL of tetrahydrofuran; then add 1.1g of 4-dimethylaminopyridine and 5.5mL of triethylamine and react at 25℃ for 1h; after the reaction is completed, add 6.51g of t-Bu2PCl dropwise and react at 25℃ for 1h; after the reaction is completed, centrifuge to collect the solid and wash it with ethyl acetate until the fluorescence of the supernatant disappears; dry it in a vacuum drying oven at 60℃ to obtain phosphinized lignin.

[0103] (4) Take 1g of the phospholignin obtained in step (3) and dissolve it in a 0.4wt% NaOH solution. Add 1.896g NiCl2·6H2O and 0.262g CoCl2 and mix and stir evenly. Add sodium hydroxide solution dropwise to adjust the pH of the mixed solution to 8 and stir for 60min to carry out coordination. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h. After the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain the NiCo-lignin-based supramolecular precursor.

[0104] (5) 1g of the NiCo-lignin-based supramolecular precursor obtained in step (4) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain phosphorus-doped lignin-derived carbon-supported NiCo material.

[0105] Comparative Example 6 A method for preparing a phosphorus-doped lignin-derived carbon-supported NiZn alloy material includes the following steps: (1) Add 61g LiBr and 39g deionized water to a round-bottom flask and stir thoroughly to dissolve completely; then add 5g alkali lignin and 10mL HBr; heat the mixture to 100℃ and carry out a reflux reaction in an oil bath for 4h; after the reaction is completed, cool the mixture to room temperature and filter it through a glass Buchner funnel; wash the obtained product repeatedly with deionized water until the filtrate is neutral, and finally freeze-dry to obtain demethylated lignin.

[0106] (2) Take 2g of the demethylated lignin obtained in step (1) and add it to a 50mL beaker. Dissolve it with deionized water and adjust the pH to 8 with sodium hydroxide. Add 60mg Fe(OH)3 and 2.4g H2O2 to the beaker in sequence and react at 60℃ for 1h. Then filter to remove Fe(OH)3, add dilute hydrochloric acid to the filtrate to adjust the pH to 3 to obtain a precipitate. Centrifuge to collect the precipitate, wash the precipitate with deionized water until the filtrate is neutral, and freeze dry to obtain polyhydroxylated lignin.

[0107] (3) Dissolve 3g of the polyhydroxylated lignin obtained in step (2) in a three-necked flask and dissolve it with 60mL of tetrahydrofuran; then add 1.1g of 4-dimethylaminopyridine and 5.5mL of triethylamine and react at 25℃ for 1h; after the reaction is completed, add 6.51g of t-Bu2PCl dropwise and react at 25℃ for 1h; after the reaction is completed, centrifuge to collect the solid and wash it with ethyl acetate until the fluorescence of the supernatant disappears; dry it in a vacuum drying oven at 60℃ to obtain phosphinized lignin.

[0108] (4) Take 1g of the phospholignin obtained in step (3) and dissolve it in a 0.4wt% NaOH solution. Add 1.896g NiCl2·6H2O and 0.275g ZnCl2 and mix and stir evenly. Add sodium hydroxide solution dropwise to adjust the pH of the mixed solution to 8 and stir for 60min to carry out coordination. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and react at 180℃ for 8h. After the reaction is completed, centrifuge the obtained sample, put it in a refrigerator to freeze and then transfer it to a freeze dryer for drying. The obtained sample is ground to obtain the NiZn-lignin-based supramolecular precursor.

[0109] (5) 1g of the NiZn-lignin-based supramolecular precursor obtained in step (4) was calcined at high temperature under N2 atmosphere using a thermal stabilization procedure. The high temperature calcination temperature was 800℃, the heating rate was 5℃ / min, and the high temperature calcination time was 2h. After the high temperature calcination was completed, the sample was cooled to room temperature, washed with deionized water, and dried at 60℃ for 12h to obtain phosphorus-doped lignin-derived carbon-supported NiZn material.

[0110] Verification Example 1 The lignin-derived carbon-supported NiCu alloy materials prepared in Examples 1-4 and Comparative Example 1 were subjected to electrochemical performance tests to investigate their catalytic performance in glycerol oxidation, glucose electrooxidation, and furfural electrooxidation. Electrochemical performance tests were conducted on a Gamry Interface 1010 electrochemical workstation using a traditional three-electrode system. A spectroscopically pure graphite rod (99.999% purity) was used as the counter electrode, and Hg / HgO or Hg / Hg2Cl2 was used as the reference electrode. The working electrode was fabricated using a drop-coating method, where 4 mg of carbon material powder was added to 200 μL of 0.25% Nafion-ethanol solution and ultrasonically dispersed for 15 min. 50 μL of the sample dispersion was then dropped onto carbon paper (0.5 × 0.5 mm). The resulting catalyst loading was 4.0 mg·cm³. -2 OER and electrocatalytic conversion performance were tested in 1M KOH electrolyte solution or 0.1M Na2B4O7 electrolyte solution. Polarization curves were measured by linear sweep voltammetry at 2 mV·s⁻¹. -1 The rate was scanned up to 1V, and the current density was taken as 10mA·cm. -2 Electrocatalytic activity was measured in a standard three-electrode system. To eliminate the potential gain effect of Pt on the catalyst, the auxiliary electrode was replaced with a spectroscopically pure graphite rod.

[0111] Chronoamperometry (CA) was performed at different constant potentials using an H-type electrolytic cell to obtain the products of glycerol electrooxidation. The electrolytic cell was separated from the working electrode by Nafion 117 to prevent the glycerol oxidation products from contacting the counter electrode and thus preventing product reduction. A mixed solution of 0.1M Glycerol and 0.1M Na₂B₄O₇ was used as the electrolyte. 50 mL of the electrolyte was stirred at 250 rpm, and the temperature was maintained at room temperature during the test.

[0112] Take 1 mL of the product solution and dilute it to acidic pH with dilute sulfuric acid. Filter the solution using a 0.22 μm PTFE syringe filter. Analyze the product sample using a high-performance liquid chromatography (HPLC, 1260 / 1290 Infinity LC, Agilent) instrument equipped with a refractive index (RID-10A) and ultraviolet (UV) detector. Use a Bio-Rad HPX-87H HPLC column with guard column, at 50 °C, with a concentration of 5 mmol / L. -1 Sulfuric acid was used as the mobile phase, and the product separation was performed at a flow rate of 0.5 mL / min.

[0113] Infrared spectroscopy was performed on the lignin prepared in each step of the modification process in Example 1. The results were as follows: Figure 1As shown, AL represents unmodified lignin; DAL represents demethylated lignin; HAL represents polyhydroxylated lignin; and PAL represents phospholated lignin. The results show that 1403 cm⁻¹... -1 The characteristic peak at 1126 cm⁻¹ can be assigned to the CH structure on the aromatic ring. -1 The signal at this location is CH produced by the alkane structure, 1500 cm⁻¹ -1 The two characteristic peaks appearing nearby represent the C-C vibrations on the benzene ring. After phosphine modification, the peak at 1164 cm⁻¹ in the spectrum... -1 A new characteristic peak appeared at [location], corresponding to the PO bond, indicating the success of phosphination modification. The 31P NMR spectrum of the phosphinated lignin in Example 1 further confirms the presence of the PO structure (see [reference]). Figure 2 This indicates that the grafting sites of the phosphating reagent and lignin are oxygen-containing functional groups; while the phenolic hydroxyl groups may be the main active sites for the phosphating reaction. Therefore, increasing the content of phenolic hydroxyl groups in lignin can improve the degree of phosphating of lignin.

[0114] The morphological characterization of Example 1 is as follows: Figure 3 As shown, the structure of its phosphorus-doped lignin-derived carbon-supported NiCu alloy is displayed. Scanning electron microscopy (SEM) Figure 3 The results of (a) show that Example 1 exhibits the characteristics of a supported catalyst, namely, spherical metal uniformly supported on an amorphous carbon support. Furthermore, transmission electron microscopy (TEM) Figure 3 (b) This further confirmed the dispersion of the metal on the support. High-magnification transmission electron microscopy (TEM) Figure 3 c) Clear lattice fringes of the NiCu(111) crystal plane are displayed, a result corresponding to the X-ray diffraction pattern. The elemental distribution of Example 1 is as follows. Figure 3 As shown in diagram di, the alloying effect between Ni and Cu is obvious, and their distributions are almost identical. At the same time, it can be observed that the distribution of P is more closely matched with that of C, indicating that P mainly exists in the carbon support rather than coordinating with the metal.

[0115] Figure 4 The XRD results for Examples 1-4 and Comparative Example 1 show that all samples exhibit a NiCu alloy structure. Table 1 shows the XPS results for Examples 1-4 and Comparative Example 1, indicating that phosphating modification can effectively increase the number of Lewis acid sites on the support. Example 1 has the highest P element content, indicating that multi-step modification promotes the generation of more phosphating sites, indirectly increasing the number of Lewis acid sites on the support.

[0116] Table 1. Atomic percentage results of P and C elements in Examples 1-4 and Comparative Example 1

[0117] Furthermore, electrochemical performance tests were conducted on Examples 1-4 and Comparative Example 1, and the DHA selectivity and conversion efficiency in their products were detected. Figure 5 and Figure 6 The GOR linear sweep voltammetry curves and Tafel slope plots for Examples 1-4 and Comparative Example 1 are shown in Table 2. The electrochemical testing and liquid-phase product analysis results for Examples 1-4 and Comparative Example 1 are also shown in Table 2.

[0118] Table 2. Results of GOR testing and liquid phase product analysis in Examples 1-4 and Comparative Example 1

[0119] The results showed that, compared with Comparative Example 1 without phosphating modification, Example 4 showed significantly improved performance in preparing DHA by electro-oxidation of glycerol in a mild environment after phosphating modification. At the same time, the multi-step modification treatment of lignin by simultaneously demethylating the nucleus and / or polyhydroxylating on the basis of phosphating modification can more effectively improve the reaction kinetics of GOR, obtain a higher current density at a low potential, and promote the rapid generation of DHA.

[0120] Figure 7 The XRD results for Examples 5-7 are shown. The results are similar to those for Examples 1-4, all showing the formation of NiCu alloy structures, indicating that the change in the phosphating agent has no significant impact on the subsequent formation of the metal alloy phase. Table 3 shows the XPS results for Examples 1 and 5-7. Although the different structures of the phosphating agents lead to different degrees of phosphating reaction, resulting in changes in the P doping amount, the overall doping amount remains stable at a high level.

[0121] Table 3. Atomic percentage results of P and C elements in Examples 1, 5-7

[0122] Furthermore, the electrochemical and liquid-phase product analysis tests described above were performed on Examples 5-7. Figure 8 and Figure 9 The GOR linear sweep voltammetry curves and Tafel slope plots for Examples 1 and 5-7 are shown in Table 4. The electrochemical testing and liquid-phase product analysis results for Examples 1 and 5-7 are also shown in Table 4.

[0123] Table 4. Results of GOR testing and liquid phase product analysis in Examples 1, 5-7

[0124] The results show that even when different phosphating agents are used to prepare phosphinated lignin, the impact on the final GOR performance is relatively small, with the differences mainly related to the P element doping content. This also indicates that this phosphating method has a certain degree of universality for many phosphine compounds with similar structures. Overall, Example 1, which uses di-tert-butylphosphine chloride as the phosphating agent, still exhibits a significant advantage in GOR performance.

[0125] Figure 10 The XRD results are for Examples 8-9 and Comparative Examples 2-3. Although different molar ratios of copper and nickel salts were used in Examples 8-9, a NiCu alloy structure was still formed, while Comparative Examples 2 and 3 produced elemental Ni and elemental Cu, respectively.

[0126] Furthermore, the above-described electrochemical and liquid-phase product analysis tests were performed on Examples 8-9 and Comparative Examples 2-3. Figure 11 and Figure 12 The GOR linear sweep voltammetry curves and Tafel slope plots for Examples 1, 8-9, and Comparative Examples 2-3 are shown in Table 5. The electrochemical testing and liquid-phase product analysis results for Examples 1, 8-9, and Comparative Examples 2-3 are also shown in Table 5.

[0127] Table 5. Results of GOR testing and liquid phase product analysis in Examples 1, 8-9, and Comparative Examples 2-3

[0128] The results show that an appropriate ratio of copper to nickel salts can enhance both GOR catalytic activity and DHA selectivity. While nickel salt alone exhibits strong GOR catalytic activity, its DHA selectivity is too low, resulting in low product value. Conversely, excessive copper salt content leads to a decrease in GOR catalytic activity due to insufficient active sites. In summary, the copper-nickel salt ratio in Example 1 is optimal, resulting in high GOR activity and DHA selectivity.

[0129] Figure 13 To compare the XRD results of Examples 4-6, the same preparation method as in Example 1 was used. Ni salt was mixed with salt solutions of other metals, and then coordinated with phosphine lignin before carbonization. The resulting catalysts all formed their own bimetallic alloy structures.

[0130] Furthermore, the above electrochemical and liquid-phase product tests were performed on Comparative Examples 4-6, and the results are shown in Table 6.

[0131] Table 6. Results of GOR testing and liquid phase product analysis in Comparative Examples 4-6

[0132] The results show that Ni alloys with other metals cannot effectively catalyze the conversion of glycerol to dihydroxyacetone and also exhibit poor reaction kinetics. Therefore, NiCu alloys have unique advantages in the catalytic conversion of glycerol to dihydroxyacetone.

[0133] Figure 14 This is a linear sweep voltammetry curve of the catalyst in Example 1 for the electrocatalytic oxidation of glucose. The catalyst provided an ultra-low potential of 1.47 V for the electrooxidation of glucose, achieving a potential of 10 mA / cm². 2 The current density was much lower than that of OER (1.80V), indicating that the electro-oxidation of glucose in Example 1 was more favorable than OER. Figure 15 This is a linear sweep voltammetry curve of the catalyst used in Example 1 for the electrocatalytic oxidation of furfural. The catalyst provided an ultra-low potential of 1.57 V for the electrooxidation of furfural, achieving a current-voltage ratio of 10 mA / cm². 2 The current density was much lower than that of OER (1.80V), indicating that furfural electro-oxidation was more favorable than OER in Example 1. The results of glucose oxidation and furfural oxidation in Example 1 are shown in Table 7.

[0134] Table 7 Results of glucose oxidation and furfural oxidation in Example 1

[0135] In summary, the phosphorus-doped lignin-derived carbon-supported NiCu alloy material prepared in this invention exhibits significantly superior electrocatalytic conversion performance of glycerol to DHA under mild conditions compared to catalysts synthesized via other routes. In Comparative Example 1, phosphine-derived carbon-supported NiCu alloy material was prepared without using phosphine-modified lignin as the carbon source; therefore, no phosphorus was detected in XPS elemental analysis, and consequently, no large number of PC-Lewis sites were introduced onto the support. Its GOR catalytic activity was significantly weaker than the catalyst materials prepared using phosphine-modified lignin as a raw material in Examples 1-7. Comparative Example 2, a single-nickel component, showed significantly lower DHA selectivity compared to the NiCu alloy materials prepared by the methods in Examples 1-9. Furthermore, Comparative Example 3, a single-copper component, exhibited much lower GOR catalytic activity than the NiCu alloy materials in Examples 1-9. This demonstrates that NiCu alloying can effectively utilize the advantages of each component to improve catalytic activity and product selectivity. However, the results of the GOR tests in Comparative Examples 4-6 show that when Ni forms an alloy structure with other metals, it does not improve the GOR performance of the material and may even weaken its original activity. Therefore, NiCu alloys have unique properties for the electro-oxidation of glycerol. Furthermore, Example 1 also exhibited strong catalytic activity in catalyzing biomass such as glucose and furfural, indicating that Example 1 may have general catalytic performance for biomass.

[0136] The above detailed embodiments provide a specific description of the analytical methods involved in this invention. It should be noted that the above description is only intended to help those skilled in the art better understand the methods and ideas of this invention, and is not intended to limit the scope of the invention. Without departing from the principles of this invention, those skilled in the art can make appropriate adjustments or modifications to this invention, and such adjustments and modifications should also fall within the protection scope of this invention.

Claims

1. A method for preparing phosphorus-doped lignin-derived carbon supported NiCu alloy material, characterized in that, The method comprises the following steps: (1) dissolving lignin in an organic solvent, adding 4-dimethylaminopyridine and triethylamine for reaction; after the reaction is completed, further adding a phosphine reagent for reaction to obtain phosphonated lignin, washing and drying; (2) dissolving the phosphonated lignin obtained in step (1) in an alkaline solution, adding nickel salt and copper salt to the solution and stirring to form a mixed solution, adjusting the pH of the mixed solution, and then performing hydrothermal reaction, and drying after the reaction is completed to obtain a nickel / copper-lignin-based supermolecular precursor; (3) performing high-temperature carbonization on the nickel / copper-lignin-based supermolecular precursor obtained in step (2), and then performing water washing and drying to obtain the product.

2. The production method according to claim 1, characterized by, The lignin in step (1) is selected from one or more of enzymatic lignin, alkali lignin, sulfite lignin, organic solvent lignin and lignin sulfonate.

3. The production method according to claim 1, characterized by, The phosphine reagent in step (1) is selected from one or more of diphenylphosphine chloride, diphenylphosphine chloride, di-tert-butylphosphine chloride and dicyclohexylphosphine chloride.

4. The method of claim 1, wherein, The alkaline solution in step (2) is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia solution and sodium carbonate solution.

5. The preparation method according to claim 1, characterized in that, The temperature of the hydrothermal reaction in step (2) is 90-200°C, and the time is 2-24h.

6. The method of claim 1, wherein, In step (2), the pH is adjusted to 6-10 using one or more of ammonia, sodium carbonate, potassium hydroxide and sodium hydroxide.

7. The preparation method according to claim 1, characterized in that, The temperature of the high-temperature carbonization in step (3) is 600-1000°C, the heating rate is 0.5-5°C / min, and the time is 1-4h.

8. The method of claim 1, wherein, Optionally, the lignin can be modified before step (1); the modification is selected from one or more of demethylation modification and polyhydroxylation modification; the demethylation modification comprises the following steps: dissolving lignin raw material in a lithium bromide aqueous solution, adding hydrobromic acid, stirring uniformly and heating for reaction; after the reaction is completed, the product is collected, washed and dried to obtain demethylated lignin; the polyhydroxylation modification comprises the following steps: dissolving lignin raw material in a sodium hydroxide solution, sequentially adding iron hydroxide and hydrogen peroxide, and heating for reaction; after the reaction is completed, the pH of the solution is adjusted to obtain a precipitate, which is washed and dried to obtain polyhydroxylated lignin.

9. The phosphorus-doped lignin-derived carbon-supported NiCu alloy material prepared by the method according to any one of claims 1-8.

10. Application of the phosphorus-doped lignin-derived carbon-supported NiCu alloy material prepared by the method according to any one of claims 1-8 in biomass electrocatalytic conversion.

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