Cu@metal phthalocyanine heterojunction catalyst, preparation method thereof and application thereof in electrocatalytic hydrogenation of 5-hydroxymethylfurfural to prepare 2,5-furandimethanol

Abstract

The application discloses a Cu@ metal phthalocyanine heterojunction catalyst and a preparation method and application thereof in electrocatalytic hydrogenation of 5-hydroxymethylfurfural to prepare 2,5-furan dimethyl alcohol; the CuO nanowire is used as a carrier, metal phthalocyanine nanoparticles are effectively loaded by coordination of 3,4-dihydroxybenzonitrile through a solvothermal reaction, and then the Cu@ metal phthalocyanine heterojunction catalyst is prepared through electro-reduction; the preparation method is simple, raw material prices are low, no noble metal is used, production cost is effectively reduced, and the method has a good industrial application prospect; the catalyst has excellent electrocatalytic hydrogenation performance; at room temperature and normal pressure, the selectivity of 2,5-furan dimethyl alcohol can reach about 100%, the conversion rate of 5-hydroxymethylfurfural reaches 95%, and the faraday efficiency reaches 89%.

Description

Technical Field

[0001] This invention belongs to the field of biomass electrocatalytic conversion, specifically relating to a Cu@metal phthalocyanine heterojunction catalyst and its preparation method, as well as its application in the electrocatalytic hydrogenation of 5-hydroxymethylfurfural to synthesize 2,5-furandiethanol. Background Technology

[0002] 5-Hydroxymethylfurfural (HMF) is an important biomass platform molecule derived from hexoses, showing great promise for conversion into more valuable commodities. A significant product of HMF hydrogenation is 2,5-dihydroxymethylfuran (DHMF). Currently, the main methods for synthesizing DHMF from HMF are traditional thermocatalytic reduction and electrocatalytic reduction. The former suffers from drawbacks such as high temperature and pressure, high pollution, low selectivity, and multiple byproducts. For example, Chinese invention patent application No. 202211473597.2 discloses a catalyst and its preparation method for the selective hydrogenation of 5-hydroxymethylfurfural to 2,5-furandimethyl. Using platinum and iridium as active components and titanium dioxide as a support, selective hydrogenation can be carried out under relatively mild conditions under the synergistic effect of the metals. Compared with existing catalysts, it can achieve better HMF conversion and DHMF selectivity. Using water as a solvent is more environmentally friendly, and the catalyst can be reused more than 5 times without significant decrease in activity. However, this process uses the reactive gas H2 as a hydrogen source, which poses certain safety risks.

[0003] Electrocatalytic reduction offers advantages such as ambient temperature and pressure, low pollution, and high selectivity. For example, Chinese invention patent application number 202310543011.3 discloses a method for the electrocatalytic hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dihydroxymethylfuran using a copper-iron bimetallic catalyst. This method utilizes a copper-iron bimetallic material as the cathode, achieving the electrocatalytic hydrogenation of HMF to DHMF, avoiding the use of silver as the electrocatalyst. Furthermore, the electrodeposition method is mature and easily controlled, reducing production costs. Because copper-based materials have a high hydrogen evolution overpotential, the electrocatalytic hydrogenation from HMF to DHMF preferentially occurs during the reduction process, and the addition of iron significantly improves the selectivity of the reaction.

[0004] However, HMF electrocatalytic hydrogenation often competes with the hydrogen evolution reaction (HER), leading to a decrease in the DHMF Faradaic efficiency (FE), especially on electrodes with low HER overpotentials (such as Pt, Rh, and Ru). To circumvent this problem, HMF hydrogenation is preferably carried out on electrodes with high HER overpotentials (such as Cu and Ag). Although DHMF Faradaic efficiencies above 90% can be achieved, an overpotential as high as 0.51 V (relative to the reversible hydrogen electrode RHE) is required to activate the proton-electron transfer process or generate H from water activation. Therefore, there is always a trade-off between Faradaic efficiency and activity for electrocatalytic hydrogenation, which makes current catalysts insufficient for practical applications. In view of this, there is an urgent need to develop non-precious metal electrocatalysts with low cost, high activity, and strong stability to achieve highly selective cathodic electroreduction of 5-hydroxymethylfurfural to 2,5-furandiethanol. Summary of the Invention

[0005] The present invention aims to provide a Cu@metal phthalocyanine heterojunction catalyst and its preparation method. Using CuO nanowires as a support, metal phthalocyanine nanoparticles are effectively loaded via a solvothermal reaction through the coordination of 3,4-dihydroxybenzonitrile, and then the Cu@metal phthalocyanine heterojunction catalyst is obtained by electroreduction. This catalyst can be used in the electrocatalytic hydrogenation of 5-hydroxymethylfurfural to synthesize 2,5-furandimethyl.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a Cu@metal phthalocyanine heterojunction catalyst includes the following steps:

[0008] Step 1: Using copper foam as a substrate and copper source, immerse it in a mixed aqueous solution of NaOH and (NH4)2S2O8, then remove it, rinse and dry it, and calcine it in a muffle furnace to obtain a carrier with CuO nanowire array.

[0009] In the preferred mixed aqueous solution of NaOH and (NH4)2S2O8, the concentration of NaOH is 0.1 g / mL and the concentration of (NH4)2S2O8 is 0.023 g / mL.

[0010] Soaking time: 20-30 minutes, preferably 25 minutes;

[0011] Calcination conditions: temperature 200-300℃, holding time 1-3h; preferably, the temperature is increased to 250℃ at a rate of 10℃ / min, and held for 2h.

[0012] Step 2: The support with CuO nanowire array obtained in Step 1 is added to an ethanol solution of metal phthalocyanine (MPc) and 3,4-dihydroxybenzonitrile, and a solvothermal reaction is carried out at 100-150℃ (preferably 120℃) for 2-6 hours (preferably 2 hours). After that, it is taken out, rinsed and dried to obtain the pre-catalyst (denoted as CuO@MPc).

[0013] In an ethanol solution of metal phthalocyanine and 3,4-dihydroxybenzonitrile, the concentration of metal phthalocyanine is 0.1-1 mg / mL (preferably 0.5 mg / mL), and the concentration of 3,4-dihydroxybenzonitrile is 0.1-0.5 mg / mL (preferably 0.25 mg / mL).

[0014] Metallic phthalocyanines can be single-metal or bimetallic; specific examples include: cobalt phthalocyanine, copper phthalocyanine, iron phthalocyanine, zinc phthalocyanine, copper-cobalt phthalocyanine, copper-zinc phthalocyanine, and copper-iron phthalocyanine.

[0015] Step 3: In an H-type electrolytic cell containing a proton exchange membrane, a three-electrode system is constructed using the pre-catalyst obtained in Step 2 as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Constant potential reduction is performed in PBS solution to obtain Cu@metal phthalocyanine heterojunction catalyst (denoted as R-Cu@MPc).

[0016] The preferred PBS solution concentration is 1M;

[0017] Electroreduction conditions: -0.8 to -1.2 V vs. Ag / AgCl, reaction time 30 to 60 min; preferably -1 V vs. Ag / AgCl, reaction time 40 min.

[0018] In this invention, the preparation method of metal phthalocyanine is as follows:

[0019] Acid anhydride, urea, ammonium compound, and transition metal salt are mixed, ground evenly, and then transferred to a muffle furnace for calcination in air atmosphere. After calcination, the mixture is removed, washed, and dried to obtain titanium cyanide (powder).

[0020] The preferred molar ratio of acid anhydride, urea, ammonium compound, and transition metal salt is 6:45:12:1.1;

[0021] The acid anhydride is selected from at least one of pyromellitic dianhydride and phthalic anhydride;

[0022] The ammonium compound is selected from at least one of ammonium chloride and ammonium molybdate;

[0023] The transition metal salt is selected from at least one of cobalt chloride hexahydrate, copper acetate monohydrate, zinc chloride, and ferric chloride hexahydrate;

[0024] Calcination conditions: Heat to 150-300℃ (preferably 220℃) at a rate of 3℃ / min, and hold for 0.5-5h (preferably 3h).

[0025] This invention relates to Cu@metal phthalocyanine heterojunction catalysts prepared by the above-described method.

[0026] The Cu@metal phthalocyanine heterojunction catalyst described in this invention can be used in the electrocatalytic hydrogenation of 5-hydroxymethylfurfural (HMF) to prepare 2,5-furandiethanol (DHMF). Specific application methods are as follows:

[0027] In an H-type electrolytic cell containing a proton exchange membrane, a three-electrode system was constructed using a Cu@metal phthalocyanine heterojunction catalyst as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. A phosphate buffer solution containing 5-hydroxymethylfurfural was added to the cathode chamber as the cathode electrolyte, and a phosphate buffer solution was added to the anode chamber as the anode electrolyte. The cathode electrolyte was stirred and electrolyzed under constant potential at room temperature and atmospheric pressure to obtain 2,5-furandiethanol.

[0028] The phosphate buffer solution has a pH of 8 to 10, preferably pH 9;

[0029] In the cathode electrolyte, the concentration of 5-hydroxymethylfurfural is 10–40 mM, preferably 20 mM;

[0030] Electrolysis potential -0.1 to -0.6V vs. RHE, electrolysis time 0.5 to 2h; preferably -0.35V vs. RHE, electrolysis time 1h.

[0031] The beneficial effects of this invention are as follows:

[0032] This study marks the first application of phthalocyanine-based heterojunction materials in the electrocatalytic hydrogenation of 5-hydroxymethylfurfural. A method using 3,4-dihydroxybenzonitrile as a coordinating agent to effectively bridge metal phthalocyanine and copper nanowires to construct a heterojunction catalyst is proposed. This method is simple, uses inexpensive raw materials, and avoids the use of precious metals, effectively reducing production costs and demonstrating promising industrial application prospects.

[0033] The heterojunction catalyst prepared by this invention can effectively increase active sites, promote charge transport, and improve the kinetics of the electrocatalytic hydrogenation reaction of 5-hydroxymethylfurfural. The phthalocyanine loading can greatly suppress the hydrogen evolution side reaction and improve the selectivity of the organic reaction, exhibiting excellent electrocatalytic hydrogenation performance of 5-hydroxymethylfurfural: at room temperature and atmospheric pressure, the selectivity of 2,5-furandiethanol can reach ~100%, the conversion rate of 5-hydroxymethylfurfural reaches 95%, and the Faraday efficiency reaches 89%. Attached Figure Description

[0034] Figure 1Scanning electron microscope image of R-Cu@CoPc in Example 1.

[0035] Figure 2 High-performance liquid chromatography (HPLC) of the R-Cu@CoPc catalyst before and after 1 hour of electrolysis in Example 2.

[0036] Figure 3 Linear scanning voltammetry plots of different catalyst materials in Example 3.

[0037] Figure 4 Performance of different monometallic phthalocyanine heterojunction catalysts under -0.35V vs. RHE for 1 hour of electrolysis.

[0038] Figure 5 Linear scan voltammetry of different catalyst materials in Example 4. Detailed Implementation

[0039] To facilitate understanding of the present invention, specific embodiments will be further described below. These embodiments are for illustrative purposes only and do not limit the scope of the invention. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention.

[0040] Example 1:

[0041] Mix and grind 0.6098 g of pyromellitic dianhydride, 0.4740 g of phthalic anhydride, 2.721 g of urea, 0.6419 g of ammonium chloride, 0.0034 g of ammonium molybdate, and 0.2617 g of cobalt chloride hexahydrate. Heat the mixture in a muffle furnace at 3°C ​​for 1 minute. -1 The temperature was raised to 220℃ and held for 3 hours. After the reaction was completed, the mixture was washed successively with deionized water, acetone, and ethanol, and then dried under vacuum at 60℃ for 12 hours to obtain cobalt phthalocyanine powder.

[0042] Clean the 1×4cm 2 Copper foam substrates of various sizes were placed in 25 mL of deionized water containing NaOH (2.5 g) and ammonium persulfate (0.575 g) and soaked for 25 minutes. After soaking, the substrates were removed, rinsed with deionized water, and dried to obtain Cu(OH)₂. The substrates were then calcined in a muffle furnace, heated to 250 °C at a rate of 10 °C / min, and held at that temperature for 2 hours. Once the reaction was complete, CuO nanowires were obtained.

[0043] Weigh 10 mg of cobalt phthalocyanine powder and 5 mg of 3,4-dihydroxybenzonitrile and add them to 20 mL of ethanol. After dispersing evenly, transfer the mixture to a hydrothermal reactor containing CuO and solvothermal react at 120 °C for 2 hours. After the reaction, rinse and dry the material to obtain CuO@CoPc.

[0044] In an H-type electrolytic cell containing a proton exchange membrane, a three-electrode system was constructed with CuO@MPc as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The R-Cu@CoPc heterojunction catalyst was obtained by reduction in 1M PBS solution at -1.0V vs. Ag / AgCl for 40 minutes.

[0045] Figure 1 This is a morphology image of R-Cu@CoPc, which shows that cobalt phthalocyanine nanoparticles are uniformly attached to copper nanowires.

[0046] Example 2:

[0047] In an H-type electrolytic cell containing a proton exchange membrane diaphragm, a three-electrode system was constructed using R-Cu@CoPc as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. A phosphate buffer solution (pH=9) containing 20 mM 5-hydroxymethylfurfural was added to the cathode chamber as the cathode electrolyte, and a phosphate buffer solution (pH=9) was added to the anode reaction chamber as the anode electrolyte. The cathode electrolytes were stirred at room temperature and atmospheric pressure, and electrolysis was performed at -0.35 V vs. RHE for 1 hour. The products were analyzed by high-performance liquid chromatography (HPLC). Figure 2 The results are before and after electrolysis. Calculations show that the selectivity of 2,5-furandiethanol is ~100%, the conversion rate of 5-hydroxymethylfurfural is 95%, and the Faraday efficiency is 89%.

[0048] Example 3:

[0049] The preparation method and process are the same as in Example 1, except that the metal salt is adjusted to 0.2196 g of copper acetate monohydrate, while other amounts remain unchanged. An R-Cu@CuPc catalytic electrode is obtained.

[0050] The preparation method and process were the same as in Example 1, except that the metal salt was adjusted to 0.2973 g of ferric chloride hexahydrate, while other amounts remained unchanged. An R-Cu@FePc catalytic electrode was obtained.

[0051] The preparation method and process were the same as in Example 1, except that the metal salt was adjusted to 0.1499 g of zinc chloride, while other amounts remained unchanged. An R-Cu@ZnPc catalytic electrode was obtained.

[0052] like Figure 3 As shown, at -0.35V vs. RHE, the current density of R-Cu@CuPc is -19.24 mA / cm². 2 The current density of R-Cu@FePc is -22.09 mA / cm². 2 The current density of R-Cu@ZnPc is -32.89 mA / cm². 2 .

[0053] Figure 4The performance of different monometallic phthalocyanine heterojunction catalysts under -0.35V vs. RHE conditions for 1 hour of electrolysis is as follows: R-Cu@CuPc exhibits a 96% selectivity for 2,5-furandiethanol, a 94% conversion of 5-hydroxymethylfurfural, and a Faradaic efficiency of 78%. R-Cu@FePc shows a 85% selectivity for 2,5-furandiethanol, an 82% conversion of 5-hydroxymethylfurfural, and a 70% Faradaic efficiency. R-Cu@ZnPc exhibits a 90% selectivity for 2,5-furandiethanol, a 90% conversion of 5-hydroxymethylfurfural, and a 62% Faradaic efficiency.

[0054] Example 4:

[0055] The preparation method and process are the same as in Example 1, except that the metal salts are adjusted to 0.1098 g of copper acetate monohydrate and 0.1309 g of cobalt chloride hexahydrate, while other amounts remain unchanged. An R-Cu@CuCoPc catalytic electrode was obtained.

[0056] The preparation method and process are the same as in Example 1, except that the metal salts are adjusted to 0.1098 g of copper acetate monohydrate and 0.1487 g of ferric chloride hexahydrate, while other amounts remain unchanged. An R-Cu@CuFePc catalytic electrode was obtained.

[0057] The preparation method and process are the same as in Example 1, except that the metal salts are adjusted to 0.1098 g of copper acetate monohydrate and 0.0749 g of zinc chloride, while other amounts remain unchanged. An R-Cu@CuZnPc catalytic electrode was obtained.

[0058] like Figure 5 As shown, at -0.35V vs. RHE, the current density of R-Cu@CuCoPc is -34.45 mA / cm². 2 The current density of R-Cu@CuFePc is -20.53 mA / cm². 2 The current density of R-Cu@CuZnPc is -23.79 mA / cm². 2 .

Claims

1. A method for preparing a Cu@metal phthalocyanine heterojunction catalyst, characterized in that, Includes the following steps: Step 1: Using copper foam as a substrate and copper source, immerse it in a mixed aqueous solution of NaOH and (NH4)2S2O8, then remove it, rinse and dry it, and calcine it in a muffle furnace to obtain a carrier with CuO nanowire array. Calcination conditions: temperature 200~300℃, holding time 1~3h; Step 2: The support with CuO nanowire array obtained in Step 1 is added to an ethanol solution of metal phthalocyanine and 3,4-dihydroxybenzonitrile, and a solvothermal reaction is carried out at 100~150℃ for 2~6h. After that, it is taken out, rinsed and dried to obtain the pre-catalyst. In an ethanol solution of metal phthalocyanine and 3,4-dihydroxybenzonitrile, the concentration of metal phthalocyanine is 0.1~1 mg / mL and the concentration of 3,4-dihydroxybenzonitrile is 0.1~0.5 mg / mL. The metal phthalocyanine is selected from one or more of the following: cobalt phthalocyanine, copper phthalocyanine, iron phthalocyanine, zinc phthalocyanine, copper cobalt phthalocyanine, copper zinc phthalocyanine, and copper iron phthalocyanine; Step 3: In an H-type electrolytic cell containing a proton exchange membrane, a three-electrode system is constructed using the pre-catalyst obtained in Step 2 as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Constant potential reduction is carried out in PBS solution to obtain Cu@metal phthalocyanine heterojunction catalyst. Electroreduction conditions: -0.8~-1.2V vs. Ag / AgCl, reaction time 30~60min.

2. The preparation method of the Cu@metal phthalocyanine heterojunction catalyst as described in claim 1, characterized in that, In step one, the concentration of NaOH in the mixed aqueous solution of NaOH and (NH4)2S2O8 is 0.1 g / mL and the concentration of (NH4)2S2O8 is 0.023 g / mL.

3. The preparation method of the Cu@metal phthalocyanine heterojunction catalyst as described in claim 1, characterized in that, In step one, the soaking time is 20-30 minutes.

4. The preparation method of the Cu@metal phthalocyanine heterojunction catalyst as described in claim 1, characterized in that, In step two, the preparation method of metal phthalocyanine is as follows: Acid anhydride, urea, ammonium compound, and transition metal salt are mixed, ground evenly, and then transferred to a muffle furnace for calcination in air atmosphere. After calcination, the mixture is removed, washed, and dried to obtain metallic titanium cyanide. The molar ratio of acid anhydride, urea, ammonium compound, and transition metal salt is 6:45:12:1.1; The acid anhydride is selected from at least one of pyromellitic dianhydride and phthalic anhydride; The ammonium compound is selected from at least one of ammonium chloride and ammonium molybdate; The transition metal salt is selected from at least one of cobalt chloride hexahydrate, copper acetate monohydrate, zinc chloride, and ferric chloride hexahydrate; Calcination conditions: Heat to 150~300℃ at a rate of 3℃ / min and hold for 0.5~5h.

5. The Cu@metal phthalocyanine heterojunction catalyst prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the Cu@metal phthalocyanine heterojunction catalyst as described in claim 5 in the electrocatalytic hydrogenation of 5-hydroxymethylfurfural to prepare 2,5-furandiethanol.

7. The application as described in claim 6, characterized in that, The method is as follows: In an H-type electrolytic cell containing a proton exchange membrane, a three-electrode system was constructed using a Cu@metal phthalocyanine heterojunction catalyst as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. A phosphate buffer solution containing 5-hydroxymethylfurfural was added to the cathode chamber as the cathode electrolyte, and a phosphate buffer solution was added to the anode chamber as the anode electrolyte. The cathode electrolyte was stirred and electrolyzed under constant potential at room temperature and atmospheric pressure to obtain 2,5-furandiethanol. The pH of the phosphate buffer solution is 8-10; The concentration of 5-hydroxymethylfurfural in the cathode electrolyte is 10~40 mM; Electrolysis potential -0.1~-0.6V vs. RHE, electrolysis time 0.5~2h.

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