A silver nanoparticle / cuprous selenide composite catalyst, its preparation method and application

Abstract

This invention discloses a silver nanoparticle / cuprous selenide composite catalyst, its preparation method, and its applications. The composite catalyst is formed by electrodepositing silver nanoparticles onto cuprous selenide, wherein the cuprous selenide is formed by chemical oxidation of copper foam. The preparation method of the silver nanoparticle / cuprous selenide composite catalyst of this invention is simple and inexpensive. Furthermore, the synthesized composite catalyst exhibits high catalytic activity, stable catalytic performance, good carbon dioxide reduction effect, and high selectivity for ethanol.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a silver nanoparticle / cuprous selenide composite catalyst, its preparation method, and its application. Background Technology

[0002] Among the various carbon dioxide reduction products, C 2+ Ethanol has attracted much attention due to its higher energy density and economic value compared to C1 products. As a liquid oxygen-containing C2 product that is easy to store and transport, ethanol has been widely used as a solvent and raw material in the production of organic chemicals and disinfectants.

[0003] However, developing highly efficient electrocatalysts remains a challenge. Due to the low controllability of C / C coupling, the reduction of carbon dioxide to C... 2+ The product of. Even if CC coupling is successful, due to its relative performance compared to other C... 2+ The products have relatively low activation energy barriers, and the major products of ethylene commonly found in carbon dioxide reduction still hinder this reaction system. Controlling the evolution of reaction intermediates is key to overcoming this limitation, which depends on catalyst design. Copper is an effective catalyst for the reduction of carbon dioxide to produce multi-carbon products, but its high surface mobility and low cohesive energy typically limit its activity and selectivity. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a silver nanoparticle / cuprous selenide composite catalyst that can efficiently electrocatalyze the reduction of carbon dioxide; another purpose of this invention is to provide a method for preparing the silver nanoparticle / cuprous selenide composite catalyst and its application.

[0005] Technical solution: The silver nanoparticle / cuprous selenide composite catalyst of the present invention is composed of copper selenide loaded with silver nanoparticles by electrodeposition, wherein the copper selenide is formed by chemical oxidation of copper foam.

[0006] Preferably, the cuprous selenide is in the shape of a flower stick.

[0007] Preferably, the mass ratio of silver nanoparticles in the silver nanoparticle / cuprous selenide composite catalyst is 2.1-3.3%.

[0008] More preferably, the mass ratio of silver nanoparticles in the silver nanoparticle / cuprous selenide composite catalyst is 2.69%.

[0009] The preparation method of the silver nanoparticle / cuprous selenide composite catalyst of the present invention includes the following steps:

[0010] (1) Place the foamed copper in acetone, hydrochloric acid and deionized water in sequence and perform ultrasonic treatment to remove the oily substances and oxide layer on the surface of the foamed copper.

[0011] (2) Prepare a mixed solution of sodium hydroxide and ammonium persulfate, and stir to mix;

[0012] (3) Immerse the foamed copper treated in step (1) in the mixed solution obtained in step (2) until a layer of blue copper hydroxide can be seen on the surface of the foamed copper;

[0013] (4) Extract the product from step (3), rinse, and vacuum dry;

[0014] (5) Take selenium powder, sodium borohydride and potassium hydroxide and add them to deionized water. Stir and mix at 40-60℃ to obtain a mixed solution.

[0015] (6) Place the material obtained in step (4) into the mixed solution obtained in step (5) and react at 100-150°C for 4-6 hours, then cool to room temperature;

[0016] (7) Separate the product obtained in step (6), rinse and dry it to obtain cuprous selenide;

[0017] (8) The copper selenide obtained in step (7) is connected to the three-electrode system as the working electrode and scanned CV test is performed to reactivate the copper selenide; then, a constant current is applied to the copper selenide and the deposition time is 30 to 180 s to obtain the silver nanoparticle / copper selenide composite catalyst.

[0018] Preferably, in step (1), the concentration of hydrochloric acid is 0.5 to 2 mol / L.

[0019] Preferably, in step (2), the concentration of sodium hydroxide in the mixed solution is 0.8 to 1.2 mol / L, the concentration of ammonium persulfate is 0.05 to 0.1 mol / L, and the mixture is stirred magnetically for 5 to 10 minutes.

[0020] Preferably, the reaction time in step (3) is 2 to 10 minutes.

[0021] Preferably, the rinsing in step (4) is done by rinsing with deionized water 2 to 3 times, and the vacuum drying is carried out in a vacuum oven at a temperature of 60°C.

[0022] Preferably, in step (5), the concentration of selenium powder in the mixed solution is 0.02-0.05 mol / L, the concentration of sodium borohydride is 0.05-0.1 mol / L, and the concentration of potassium hydroxide is 0.02-0.05 mol / L. The mixture is heated to 40-60°C under magnetic stirring and stirred for 20-30 minutes.

[0023] Preferably, the specific method of step (6) is as follows: 50-100 ml of the mixed solution from step (5) is loaded into a 100 ml Teflon stainless steel reactor, the material obtained in step (4) is placed in it, and the reaction is carried out at 100-150°C for 4-6 hours, and then naturally cooled to room temperature.

[0024] More preferably, the specific method of step (6) is as follows: 50-100 ml of the mixed solution from step (5) is loaded into a 100 ml Teflon stainless steel reactor, the material obtained in step (4) is placed in it, and the reaction is carried out at 120°C for 4-6 hours, followed by natural cooling to room temperature.

[0025] Preferably, the specific method of step (7) is as follows: separate the product obtained in step (6), wash it with deionized water 2 to 3 times, dry it at a temperature of 50 to 70°C for 8 to 12 hours under vacuum to obtain cuprous selenide.

[0026] Preferably, the specific method of step (8) is as follows: prepare a mixed solution of citric acid trihydrate, silver nitrate and sulfuric acid, and stir to disperse; connect the cuprous selenide obtained in step (7) as the working electrode to a three-electrode system composed of a saturated calomel reference electrode and a platinum sheet counter electrode, and use the mixed solution of citric acid trihydrate, silver nitrate and sulfuric acid as the electrolyte; perform scanning CV test to reactivate the cuprous selenide; then apply a constant current to the cuprous selenide and deposit it for 30 to 180 s to obtain a silver nanoparticle / cuprous selenide composite catalyst.

[0027] Preferably, the concentration of citric acid trihydrate in the mixed solution is 0.1–0.2 mol / L, the concentration of silver nitrate is 1.5–2.5 mol / L, and the concentration of sulfuric acid is 0.1–0.2 mol / L, and the mixture is stirred for 10–30 minutes.

[0028] Preferably, in step (8), the range of the scanning CV test is 0.2 to -0.8V (vs. SHE), and the constant current applied to the cuprous selenide is 15 to 30mA.

[0029] More preferably, the deposition time in step (8) is 90s.

[0030] The application of the silver nanoparticle / cuprous selenide composite catalyst described in this invention in the preparation of catalytic electrodes.

[0031] The application of the silver nanoparticle / cuprous selenide composite catalyst described in this invention in the electrocatalytic reduction of carbon dioxide.

[0032] The application of the silver nanoparticle / cuprous selenide composite catalyst described in this invention in the electrocatalytic reduction of carbon dioxide to ethanol.

[0033] The detection process of the silver nanoparticle / cuprous selenide composite catalyst described in this invention is as follows:

[0034] a) A working electrode for the silver nanoparticle / cuprous selenide composite catalyst was prepared. The catalyst was sealed with epoxy resin adhesive to precisely control the actual contact area (1 square centimeter) between the catalyst and the electrolyte. A three-electrode electrocatalytic system was constructed, using a platinum sheet electrode as the counter electrode and a silver chloride electrode as the reference electrode.

[0035] b) Before the electrocatalytic experiment, the cathode cell was aerated at a flow rate of 180-200 sccm for 25-30 minutes to saturate the electrolyte, and a certain flow rate was maintained during the experiment; 40-45 ml of 0.5 mol / L potassium bicarbonate electrolyte was added to the cathode and anode reaction cells respectively.

[0036] c) The three-electrode system was placed in a potassium bicarbonate solution, and the electrocatalytic carbon dioxide reduction performance of the silver nanoparticle / cuprous selenide composite catalyst was determined by linear sweep voltammetry under two different conditions: argon saturation and carbon dioxide saturation. The Faradaic efficiency of the silver nanoparticle / cuprous selenide composite catalyst in the electrocatalytic reduction of carbon dioxide to ethanol was also detected.

[0037] Preferably, in step b), the flow rate of carbon dioxide is 25–35 sccm, and the concentration of potassium bicarbonate is 0.45–0.55 mol / L.

[0038] Preferably, the potential range of the linear scanning voltammetry in step c) is -1.5 to 0.1 V.

[0039] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: 1. The present invention successfully synthesizes a silver nanoparticle / cuprous selenide composite catalyst through chemical oxidation, hydrothermal method, and potentiostatic deposition method. The synthesis is simple and inexpensive; 2. The silver nanoparticle / cuprous selenide composite catalyst synthesized by the present invention has high catalytic activity and stable catalytic performance, exhibits good carbon dioxide reduction effect, and has high selectivity for ethanol. In particular, the 90-silver nanoparticle / cuprous selenide composite catalyst obtained when the silver deposition time is 90 seconds achieves the best electrocatalytic carbon dioxide reduction to ethanol performance; this nanoparticle-modified interface strategy balances the Cu on the catalyst surface. δ+ The active valence state causes enriched *CO to migrate to Cu. δ+ The active sites accelerate the asymmetric coupling of *CO and *CHO. At a low potential of -0.52V (vs. RHE), the silver nanoparticle / cuprous selenide structure achieves a 70.1% Faradaic efficiency and a 13.9 mA ethanol partial current in the electrocatalytic reduction of carbon dioxide to ethanol. Compared with existing catalysts, it has a lower overpotential, a larger ethanol partial current, and good ethanol selectivity. Attached Figure Description

[0040] Figure 1 This is a scanning electron microscope image of the silver nanoparticle / cuprous selenide composite catalyst of Example 2 of the present invention;

[0041] Figure 2 The X-ray diffraction pattern of the silver nanoparticle / cuprous selenide composite catalyst of Example 3 of the present invention is shown below.

[0042] Figure 3 The following are linear voltammetry curves of the various catalysts in Example 4 of the present invention under different gas conditions;

[0043] Figure 4 The image shows the Faraday efficiency distribution of the silver nanoparticle / cuprous selenide composite catalyst of Example 5 of the present invention at various potentials under carbon dioxide conditions.

[0044] Figure 5 This is a Faraday efficiency distribution diagram of the ethanol products of each catalyst in Example 5 of the present invention under carbon dioxide conditions. Detailed Implementation

[0045] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0046] Example 1

[0047] (1) First, place the foamed copper in acetone, 0.5 mol / L hydrochloric acid and deionized water in sequence, and ultrasonically treat each for 10 minutes to remove the oily substances and oxide layer on the surface.

[0048] (2) Then, add 3.2 g of sodium hydroxide and 1.2 g of ammonium persulfate to 100 ml of water and mix for about 10 minutes under magnetic stirring;

[0049] (3) Immerse the foamed copper in step (1) in the mixed solution in (2) for 10 minutes. A layer of blue copper hydroxide can be seen on the surface of the foamed copper.

[0050] (4) The material in (3) was then extracted, rinsed three times with deionized water, and dried in a vacuum oven at 60°C.

[0051] (5) Add 0.156 g of selenium powder, 0.178 g of sodium borohydride and 0.115 g of potassium hydroxide to 100 ml of deionized water, heat the solution to 60 degrees Celsius and stir for 20 minutes;

[0052] (6) The mixed solution from step (5) is loaded into a 100 ml Teflon stainless steel reactor, the material from step (4) is placed in it, and heated in an oven at 150 degrees Celsius for 4 hours, and then naturally cooled to room temperature.

[0053] (7) The product obtained in step (6) was washed three times with deionized water and dried in a vacuum oven at 70 degrees Celsius for 8 hours to obtain cuprous selenide.

[0054] (8) Mix 0.1 mol / L citric acid trihydrate, 2.0 mol / L silver nitrate and 0.1 mol / L sulfuric acid and stir for 30 minutes to ensure they are fully dispersed;

[0055] (9) The cuprous selenide prepared in step (7) is connected as the working electrode to a three-electrode system consisting of a saturated calomel reference electrode and a platinum sheet counter electrode, and the mixed solution in step (8) is used as the electrolyte. The catalyst is reactivated by scanning CV test in the range of 0.2 to -0.8V (vs. SHE). Subsequently, a constant current of 30mA is applied to the catalyst and the deposition time is 60s.

[0056] Example 2

[0057] (1) First, place the foamed copper in acetone, 2 mol / L hydrochloric acid and deionized water in sequence, and ultrasonically treat each for 10 minutes to remove the oily substances and oxide layer on the surface.

[0058] (2) Then, add 4.4 g of sodium hydroxide and 2.28 g of ammonium persulfate to 100 ml of water and mix for about 10 minutes under magnetic stirring;

[0059] (3) Immerse the foamed copper in step (1) in the mixed solution in (2) for 5 minutes. A layer of blue copper hydroxide can be seen on the surface of the foamed copper.

[0060] (4) The material in (3) was then extracted, rinsed three times with deionized water, and dried in a vacuum oven at 60°C.

[0061] (5) Add 0.39 g of selenium powder, 0.376 g of sodium borohydride and 0.28 g of potassium hydroxide to 100 ml of deionized water, heat the solution to 40 degrees Celsius and stir for 30 minutes;

[0062] (6) The mixed solution from step (5) is loaded into a 100 mL Teflon stainless steel reactor, the material from step (4) is placed in it, and heated in an oven at 100 degrees Celsius for 6 hours, and then naturally cooled to room temperature.

[0063] (7) The product obtained in step (6) was washed three times with deionized water and dried in a vacuum oven at 50 degrees Celsius for 12 hours to obtain cuprous selenide.

[0064] (8) Mix 0.1 mol / L citric acid trihydrate, 2.0 mol / L silver nitrate and 0.1 mol / L sulfuric acid and stir for 10 minutes to ensure thorough dispersion;

[0065] (9) The cuprous selenide prepared in step (7) is connected as the working electrode to a three-electrode system consisting of a saturated calomel reference electrode and a platinum sheet counter electrode, and the mixed solution in step (8) is used as the electrolyte. The catalyst is reactivated by scanning CV test in the range of 0.2 to -0.8V (vs. SHE). Subsequently, a constant current of 15mA is applied to the catalyst and the deposition time is 90s.

[0066] Figure 1 This is a scanning electron microscope image of the silver nanoparticle / cuprous selenide composite catalyst prepared in this invention.

[0067] Example 3:

[0068] (1) First, place the foamed copper in acetone, 1.0 mol / L hydrochloric acid and deionized water in sequence, and ultrasonically treat each for 10 minutes to remove the oily substances and oxide layer on the surface.

[0069] (2) Then, add 3.9 g of sodium hydroxide and 1.75 g of ammonium persulfate to 100 ml of water and mix for about 10 minutes under magnetic stirring;

[0070] (3) Immerse the foamed copper in step (1) in the mixed solution in (2) for 5 minutes. A layer of blue copper hydroxide can be seen on the surface of the foamed copper.

[0071] (4) The material in (3) was then extracted, rinsed three times with deionized water, and dried in a vacuum oven at 60°C.

[0072] (5) Add 0.156 g of selenium powder, 0.376 g of sodium borohydride and 0.115 g of potassium hydroxide to 100 ml of deionized water, heat the solution to 50 degrees Celsius and stir for 30 minutes;

[0073] (6) The mixed solution from step (5) is loaded into a 100 mL Teflon stainless steel reactor, the material from step (4) is placed in it, and heated in an oven at 120 degrees Celsius for 6 hours, and then naturally cooled to room temperature.

[0074] (7) The product obtained in step (6) was washed three times with deionized water and dried in a vacuum oven at 60 degrees Celsius for 12 hours to obtain cuprous selenide.

[0075] (8) Mix 0.1 mol / L citric acid trihydrate, 2.0 mol / L silver nitrate and 0.1 mol / L sulfuric acid and stir for 10 minutes to ensure thorough dispersion;

[0076] (9) The cuprous selenide prepared in step (7) is connected as the working electrode to a three-electrode system consisting of a saturated calomel reference electrode and a platinum sheet electrode, and the mixed solution in step (8) is used as the electrolyte. The catalyst is reactivated by scanning CV test in the range of 0.2 to -0.8V (vs. SHE). Subsequently, a constant current of 20mA is applied to the catalyst, and the deposition time is maintained at 30, 90 and 180s, respectively, to obtain silver nanoparticle / cuprous selenide composite catalysts, which are named 30-silver / cuprous selenide, 90-silver / cuprous selenide and 180-silver / cuprous selenide, respectively.

[0077] Figure 2 The crystal structure of the silver nanoparticle / cuprous selenide composite catalyst indicates that the composite catalyst is composed of cuprous selenide and silver.

[0078] Example 4:

[0079] The electrocatalytic system employed a traditional three-electrode system, using a platinum sheet electrode as the counter electrode, a silver chloride electrode as the reference electrode, and a silver nanoparticle / cuprous selenide composite catalyst as the working electrode. Before the electrocatalytic experiment, the cathode cell was aerated at a flow rate of 200 sccm for 30 minutes to saturate the electrolyte; the flow rate was maintained at 25 sccm during the experiment. 40 mL of 0.5 mol / L potassium bicarbonate electrolyte was added to both the cathode and anode cells. The catalyst was sealed with epoxy resin adhesive to precisely control the actual contact area (1 cm²) between the catalyst and the electrolyte. The three-electrode system was placed in a 0.5 M potassium bicarbonate solution, and the electrocatalytic carbon dioxide reduction performance of the silver nanoparticle / cuprous selenide composite catalyst was determined using linear sweep voltammetry under two different conditions: argon saturation and carbon dioxide saturation. The carbon dioxide reduction performance of copper foam and cuprous selenide under the same conditions was also compared.

[0080] Figure 3 The figure shows the current changes of copper foam, cuprous selenide, 30-silver / cuprous selenide, 90-silver / cuprous selenide and 180-silver / cuprous selenide under carbon dioxide and argon conditions. The figure shows that compared with copper foam and cuprous selenide, silver nanoparticles / cuprous selenide have higher current densities under both argon saturation and carbon dioxide saturation, and 90-silver / cuprous selenide has the highest current density.

[0081] Example 5:

[0082] Online gas chromatography was used to analyze gaseous products, with argon as the carrier gas. Quantification of the gaseous products was performed by obtaining a standard curve using a mixed gas while quantifying hydrogen with a TCD detector. Acetylene, ethylene, methane, and carbon monoxide were quantified using an FID-1 detector. A flow stabilizer was used at the chromatographic front end for gas filtration and dehumidification, and the carbon dioxide flow rate was controlled by a gas flow mass controller. After a 30-minute reaction period, the liquid product was filtered to remove larger impurities. The liquid was injected into the chromatograph using a 1.0 mL syringe, and ethanol was quantified using a high-precision FID-2 detector. Standard solutions of 10, 25, 50, and 100 ppm ethanol were added to the chromatograph to obtain ethanol standard curves. Formate concentrations were analyzed using ion chromatography, and standard curves for formate were obtained using sodium formate standard solutions of 0, 5, 25, 50, and 100 ppm.

[0083] The three-electrode system was placed in a 0.5 M potassium bicarbonate solution, and the Faraday efficiency of the silver nanoparticle / cuprous selenide composite catalyst for the electrocatalytic reduction of carbon dioxide products was tested under carbon dioxide saturation conditions.

[0084] Figure 4 The distribution of the Faradaic efficiency of the 90-silver / cuprous selenide composite catalyst at various potentials under carbon dioxide conditions is shown. The Faradaic efficiency of the 90-silver / cuprous selenide composite catalyst for ethanol increases with the increase of the applied test potential, reaching 41.44% at -0.47V, and exhibiting an optimal Faradaic efficiency of 70.1% at -0.52V (vs. RHE).

[0085] Based on Example 5, the Faraday efficiency of the electrocatalytic reduction of ethanol by copper foam, cuprous selenide, 30-silver / cuprous selenide, 90-silver / cuprous selenide and 180-silver / cuprous selenide at various potentials was compared under carbon dioxide conditions.

[0086] Figure 5 The distribution of the Faraday efficiency of copper foam, cuprous selenide, 30-silver / cuprous selenide, 90-silver / cuprous selenide, and 180-silver / cuprous selenide for ethanol under carbon dioxide conditions is shown. Copper foam exhibits the lowest selectivity for ethanol; this is improved after selenization, with cuprous selenide showing a significant increase in ethanol selectivity. The loading of silver nanoparticles diversifies the active sites, alters the local charge distribution, and thus modulates the interaction between the intermediate and the active sites, further improving the selectivity for ethanol. Among the silver / cuprous selenide composite catalysts, the 90-silver / cuprous selenide composite catalyst achieves the best Faraday efficiency for ethanol.

Claims

1. A method for preparing a silver nanoparticle / cuprous selenide composite catalyst, characterized in that, Includes the following steps: (1) Place the foamed copper in acetone, hydrochloric acid and deionized water in sequence and perform ultrasonic treatment to remove the oily substances and oxide layer on the surface of the foamed copper; (2) Prepare a mixed solution of sodium hydroxide and ammonium persulfate, and stir to mix; (3) Immerse the foamed copper treated in step (1) in the mixed solution obtained in step (2) until a layer of blue copper hydroxide is visible on the surface of the foamed copper; (4) Extract the product from step (3), rinse, and vacuum dry; (5) Take selenium powder, sodium borohydride and potassium hydroxide and add them to deionized water. Stir and mix at 40~60℃ to obtain a mixed solution; (6) Place the material obtained in step (4) into the mixed solution obtained in step (5) and react at 100~150℃ for 4~6 hours, then cool to room temperature; (7) Separate the product obtained in step (6), wash and dry it to obtain cuprous selenide; (8) Prepare a mixed solution of citric acid trihydrate, silver nitrate and sulfuric acid, and stir to disperse; connect the copper selenide obtained in step (7) to the three-electrode system as the working electrode, and use the mixed solution of citric acid trihydrate, silver nitrate and sulfuric acid as the electrolyte; perform scanning CV test to reactivate copper selenide; then apply constant current to copper selenide and deposit for 30~180s to obtain silver nanoparticle / copper selenide composite catalyst.

2. The preparation method of the silver nanoparticle / cuprous selenide composite catalyst according to claim 1, characterized in that, In step (2), the concentration of sodium hydroxide in the mixed solution is 0.8~1.2 mol / L, and the concentration of ammonium persulfate is 0.05~0.1 mol / L. The mixture is stirred magnetically for 5~10 minutes.

3. The preparation method of the silver nanoparticle / cuprous selenide composite catalyst according to claim 1, characterized in that, The reaction time in step (3) is 2 to 10 minutes.

4. The preparation method of the silver nanoparticle / cuprous selenide composite catalyst according to claim 1, characterized in that, In step (5), the concentration of selenium powder in the mixed solution is 0.02~0.05 mol / L, the concentration of sodium borohydride is 0.05~0.1 mol / L, and the concentration of potassium hydroxide is 0.02~0.05 mol / L. The solution is heated to 40~60℃ under magnetic stirring and stirred for 20~30 minutes.

5. The preparation method of the silver nanoparticle / cuprous selenide composite catalyst according to claim 1, characterized in that, The specific method of step (7) is as follows: separate the product obtained in step (6), wash it with deionized water 2 to 3 times, and dry it; the drying temperature is 50 to 70°C, the drying time is 8 to 12 hours, and the drying condition is vacuum, to obtain cuprous selenide.

6. The preparation method of the silver nanoparticle / cuprous selenide composite catalyst according to claim 1, characterized in that, In step (8), the copper selenide obtained in step (7) is used as the working electrode and connected to a three-electrode system consisting of a saturated calomel reference electrode and a platinum sheet counter electrode.

7. The preparation method of the silver nanoparticle / cuprous selenide composite catalyst according to claim 1, characterized in that, In step (8), the scanning CV test range is 0.2 to -0.8 V vs. SHE, and the constant current applied to cuprous selenide is 15 to 30 mA.

8. A silver nanoparticle / cuprous selenide composite catalyst prepared by any one of the preparation methods described in claims 1 to 7.

9. The application of the silver nanoparticle / cuprous selenide composite catalyst of claim 8 in the electrocatalytic reduction of carbon dioxide.

Images