Preparation method of Cu / ZnO catalyst for electrocatalytic reduction of alkynes

Abstract

The present invention relates to a preparation method of a Cu / ZnO catalyst for electrocatalytic alkyne reduction. First, carbon paper cut into small pieces is soaked with dilute nitric acid, rinsed with deionized water, dried, and calcined. Then ZnO and NaBH4 are added to deionized water and stirred, centrifuged, washed, and dried. The obtained pretreated ZnO and CuNO3 are added to deionized water and stirred, centrifuged, washed, dried, and calcined. The obtained Cu / ZnO-300 catalyst is dispersed in isopropanol and ultrasonically applied, dripped onto the pretreated carbon paper, and then dried to prepare a Cu / ZnO catalyst. The present invention uses a simple synthesis of a Cu / ZnO catalyst to electroreducing alkynes in an alkaline electrolyte. The olefin selectivity reaches 59.71% and the Faraday efficiency is 24.66%.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and particularly relates to a method for preparing a Cu / ZnO catalyst for electrocatalytic reduction of alkynes. Background Art

[0002] Olefins play an important role in the manufacture of natural products, pharmaceuticals, and advanced materials. The selective reduction of alkynes to alkenes is an important route for producing alkenes in organic synthesis. Traditional catalysis uses flammable and explosive hydrogen or expensive and toxic organic hydrogen sources as the main hydrogen source for the selective semi-hydrogenation of alkynes to alkenes. This is expensive and poses serious safety and environmental concerns. Electrochemical transformation represents a powerful, environmentally friendly, and easy-to-operate method in organic synthesis. The use of H* generated in situ by water electrolysis for electrochemical transfer hydrogenation to produce high-value-added chemicals provides an environmentally friendly and sustainable alternative to traditional hydrogenation methods. Using water as the hydrogen source and using inexpensive metal catalysts for the electrocatalytic selective reduction of alkynes to alkenes can not only avoid potential environmental pollution and safety issues, but also save production costs. Summary of the Invention

[0003] To achieve the above object, the present invention provides a method for preparing a Cu / ZnO catalyst for electrocatalytic reduction of alkynes.

[0004] The technical solution adopted in the present invention is:

[0005] A method for preparing a Cu / ZnO catalyst for electrocatalytic alkyne reduction comprises the following steps:

[0006] 1) Pretreatment of carbon paper: The carbon paper was cut into 1×2 cm pieces, then soaked in dilute nitric acid for 30 min, rinsed with deionized water, dried, and calcined in a muffle furnace to obtain pretreated carbon paper;

[0007] 2) ZnO pretreatment: 0.01 mol ZnO was added to 0.01 mol NaBH4 and 50 mL deionized water, stirred for 5 h, then centrifuged, washed, and dried to obtain pretreated ZnO;

[0008] 3) Preparation of Cu / ZnO-w catalyst: 0.02 g of the pretreated ZnO obtained in step 2) was added with 0.25 mmol of CuNO3 and 20 mL of deionized water, stirred for 25 h, then centrifuged, washed, and dried to obtain a Cu / ZnO-w catalyst;

[0009] 4) Preparation of Cu / ZnO Catalyst: 0.01 g of the Cu / ZnO-w catalyst obtained in step 3) was calcined in a muffle furnace to obtain Cu / ZnO-300 catalyst powder. 5 mg of the Cu / ZnO-300 catalyst powder was dispersed in 2 mL of isopropanol and sonicated for 5 min. The resulting mixture was then dropped onto the pretreated carbon paper obtained in step 1) and dried to prepare a Cu / ZnO catalyst.

[0010] Furthermore, in the above preparation method, in step 1), the calcination condition is calcination at 300° C. for 5 hours.

[0011] Furthermore, in the above preparation method, in step 2) and step 3), the stirring speed is 500 r / min.

[0012] Furthermore, in the above preparation method, in step 2) and step 3), the drying condition is drying at 60° C. overnight.

[0013] Furthermore, in the above preparation method, in step 4), the calcination condition is calcination at 300° C. for 2 hours.

[0014] Furthermore, in the above preparation method, in step 4), the drying condition is drying at 60° C. for 2 h.

[0015] Application of the Cu / ZnO catalyst prepared by any of the above preparation methods in electrocatalytic reduction of alkynes.

[0016] The beneficial effects of the present invention are:

[0017] This invention utilizes a simple synthetic Cu / ZnO catalyst to electrocatalyze the reduction of alkynes in an alkaline electrolyte using water as a hydrogen source. Using water as the hydrogen source, the electrocatalytic reduction of alkynes in a 1M KOH electrolyte produces high-value-added alkenes, achieving an olefin selectivity of 59.71% and a Faradaic efficiency of 24.66%. This method avoids the use of expensive and toxic organic hydrogen sources and achieves transfer hydrogenation of organic compounds in an alkaline electrolyte, yielding high-value-added products. This approach achieves both cost savings and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the scanning electron microscopy (SEM) image of the Cu / ZnO catalyst.

[0019] Figure 2 is the X-ray diffraction pattern (XRD) of Cu / ZnO catalyst.

[0020] Figure 3 Linear sweep voltammograms of electrocatalytic alkyne reduction over Cu / ZnO catalyst and CP catalyst.

[0021] Figure 4This is a graph showing the change in current density over time for the electrocatalytic reduction of alkynes over Cu / ZnO catalyst. DETAILED DESCRIPTION

[0022] The present invention is further described below with reference to specific embodiments.

[0023] Example 1 Preparation of Cu / ZnO Catalyst

[0024] 1) Pretreatment of carbon paper: The purchased carbon paper was cut into 1×2 cm small pieces, then soaked in dilute nitric acid for 30 min, rinsed with deionized water, blown dry, and calcined in a muffle furnace at 300°C for 5 h to obtain pretreated carbon paper (CP catalyst);

[0025] 2) ZnO pretreatment: 0.01 mol ZnO was added to 0.01 mol NaBH4 and 50 mL deionized water, and the mixture was stirred at 500 rpm for 5 h, followed by centrifugation, washing, and drying at 60°C overnight to obtain pretreated ZnO.

[0026] 3) Preparation of Cu / ZnO-w catalyst: 0.02 g of the pretreated ZnO obtained in step 2) was added with 0.25 mmol of CuNO3 and 20 mL of deionized water. The mixture was stirred at 500 rpm for 25 h, then centrifuged, washed, and dried at 60°C overnight to obtain a Cu / ZnO-w catalyst.

[0027] 4) Preparation of Cu / ZnO catalyst: 0.01 g of the Cu / ZnO-w catalyst obtained in step 3) was calcined in a muffle furnace at 300°C for 2 h to obtain Cu / ZnO-300 catalyst powder. 5 mg of the Cu / ZnO-300 catalyst powder was dispersed in 2 mL of isopropanol and sonicated for 5 min. The resulting mixture was then dropped onto the pretreated carbon paper obtained in step 1) and dried at 60°C for 2 h to prepare a Cu / ZnO catalyst.

[0028] from Figure 1 From the scanning electron microscope (SEM) image, we can see that the Cu / ZnO catalyst particles are irregular and disorderly arranged. Figure 2 From the XRD pattern in , we can see that the peak at 38.7 corresponds to CuO; 31.7, 34.5, 36.5, 47.5 and 56.6 correspond to the (100), (001), (101), (102) and (110) planes of ZnO, respectively, indicating that the Cu / ZnO catalyst was successfully synthesized.

[0029] Example 2 Electrochemical Performance Test of Cu / ZnO Catalyst and CP Catalyst

[0030] Electrochemical performance test of Cu / ZnO catalyst:

[0031] The electrochemical performance of Cu / ZnO catalyst was tested using CHI760 electrochemical workstation. The electrochemical performance test was carried out using an H-type electrolytic cell and a three-electrode working system. 1M KOH was used as the electrolyte, 15 mL of electrolyte was added to the anode chamber and the cathode chamber respectively, and 2.2 mg of 4-ethynylaniline and 0.7 mL of 1,4-dioxane were added to the cathode chamber. The Cu / ZnO catalyst was the working electrode, the carbon rod was the counter electrode, and the Ag / AgCl electrode was the reference electrode. The electrolytic cell was sealed, and nitrogen was passed through it for 30 minutes to remove oxygen in the solution. Subsequently, the electrochemical performance test was carried out to obtain the LSV curve of the Cu / ZnO catalyst, as shown in FIG. Figure 3 Solid line.

[0032] Electrochemical performance test of CP catalyst:

[0033] The electrochemical performance of the CP catalyst was tested using a CHI760 electrochemical workstation. The electrochemical performance test was carried out using an H-type electrolytic cell and a three-electrode working system. 1M KOH was used as the electrolyte, 15mL of electrolyte was added to the anode chamber and the cathode chamber respectively, and 2.2mg of 4-ethynylaniline and 0.7ml of 1,4-dioxane were added to the cathode chamber. The CP catalyst was the working electrode, the carbon rod was the counter electrode, and the Ag / AgCl electrode was the reference electrode. The electrolytic cell was sealed and nitrogen was passed through it for 30 minutes to remove oxygen in the solution. The electrochemical performance test was then carried out to obtain the LSV curve of the CP catalyst, as shown in FIG. Figure 3 dotted line.

[0034] The voltage used in the electrochemical performance test was based on the standard hydrogen electrode potential. The electrochemical workstation model was CHI760E, and the linear sweep voltammetry parameters were a rotation rate of 1600 rpm and a scan rate of 10 mV s -1 .

[0035] The performance of Cu / ZnO catalyst and CP catalyst was compared by electrochemical testing. Figure 3 From the LSV curve, it can be seen that the current density of Cu / ZnO catalyst can reach 6.27 mA / cm at -0.55 V vs. RHE. 2 When CP is -0.55V vs.RHE, the current density is only 2.01mA / cm 2 At -0.55 V vs. RHE, the current density of the Cu / ZnO catalyst is approximately 3.2 times that of the CP catalyst. The voltage used in this example is based on the standard hydrogen electrode potential. By comparison, it can be found that the current density of the Cu / ZnO catalyst is significantly higher than that of the CP catalyst, and the Cu / ZnO catalyst has a better catalytic effect on the reduction of alkynes.

[0036] Example 3 Chronoamperometry (IT)

[0037] Chronoamperometry (IT): Using water as the hydrogen source and a Cu / ZnO catalyst as the working electrode, the selective reduction of alkynes to alkenes was achieved through long-term chronoamperometry (IT).

[0038] Voltage of IT experiment: from Figure 3 As can be seen from the LSV curve, the current density difference between the Cu / ZnO catalyst and the CP catalyst is the largest at -0.55 V vs. RHE, so the IT experiment was performed at -0.55 V vs. RHE. The electrolytic cell and electrolyte for the IT experiment: an H-type electrolytic cell was used. The electrolyte in the cathode electrolytic cell was 14.3 ml of 1 M KOH, and the electrolyte in the anodic electrolytic cell was 15 ml of 1 M KOH solution. The cathode and anodic electrolytic cells were connected by a proton exchange membrane. The electrocatalytic reaction was carried out in the cathode electrolytic cell. The electrolytic substrate was 2.2 mg of 4-ethynylaniline, and 0.7 mL of 1,4-dioxane was added as a co-solvent. The working electrode for the IT experiment was a Cu / ZnO catalyst. The counter electrode for the IT experiment was a carbon rod. The reference electrode for the IT experiment was an Ag / AgCl electrode. The IT experiment lasted 3 h at a speed of 400 r / min. The electrochemical workstation model was CHI 760E.

[0039] Detection of olefin products: After a 3-hour IT experiment, the electrolyte was extracted with dichloromethane. The lower layer was removed and the internal standard, n-octane, was added. Mixing was performed by sonication for 5 seconds, and 1 μl of the sample was injected into the gas phase. The selectivity for olefin products was calculated using the internal standard method. The gas chromatograph used was a GC-2014.

Claims

1. A Cu / ZnO catalyst for electrocatalytic reduction of alkynes to produce alkenes, characterized in that: The preparation method of the Cu / ZnO catalyst comprises the following steps: 1) Carbon paper pretreatment: Cut the carbon paper into 1×2 cm pieces, soak them in dilute nitric acid for 30 min, rinse them with deionized water, blow dry them, and calcine them in a muffle furnace to obtain pretreated carbon paper. 2) ZnO pretreatment: Take 0.01 mol ZnO, add 0.01 mol NaBH4, add 50 mL deionized water, stir for 5 hours, then centrifuge, wash, and dry to obtain pretreated ZnO; 3) Preparation of Cu / ZnO-w catalyst: 0.02 g of the pretreated ZnO obtained in step 2) was added with 0.25 mmol of CuNO3 and 20 mL of deionized water. The mixture was stirred for 25 h, then centrifuged, washed, and dried to obtain a Cu / ZnO-w catalyst. 4) Preparation of Cu / ZnO Catalyst: 0.01 g of the Cu / ZnO-w catalyst obtained in step 3) was calcined in a muffle furnace to obtain Cu / ZnO-300 catalyst powder. 5 mg of the Cu / ZnO-300 catalyst powder was dispersed in 2 mL of isopropanol and sonicated for 5 min. The resulting mixture was then dropped onto the pretreated carbon paper obtained in step 1) and dried to prepare a Cu / ZnO catalyst.

2. The use according to claim 1, characterized in that In step 1), the calcination condition is calcination at 300° C. for 5 hours.

3. The use according to claim 1, characterized in that In step 2) and step 3), the stirring speed is 500 r / min.

4. The use according to claim 1, characterized in that In step 2) and step 3), the drying condition is drying at 60° C. overnight.

5. The use according to claim 1, characterized in that In step 4), the calcination condition is calcination at 300° C. for 2 h.

6. The use according to claim 1, characterized in that In step 4), the drying condition is drying at 60° C. for 2 h.

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