Electrocatalytic reduction of carbon monoxide to produce c 2+ Catalysts for alcohol production and their use

Abstract

Electrocatalytic reduction of carbon monoxide to prepare C 2+ The application relates to a catalyst for catalytic reduction of alcohol and application thereof, and belongs to the technical field of electrocatalytic reduction. A copper cage catalyst with controllable Cu + / Cu 0 ratio is prepared first, and then is applied to electrocatalytic reduction of carbon monoxide to selectively generate C 2+ alcohol. The catalyst can generate C 2+ alcohol through electrocatalytic reduction of carbon monoxide, and the Faraday efficiency (selectivity) can reach 58.3% (in which the Faraday efficiency of ethanol is 27.5%, and the Faraday efficiency of n-propanol is 30.8%). The raw material for preparing the catalyst is widely sourced and low in price, the preparation method is simple, and the catalyst has market application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalytic reduction, and in particular to a catalyst for electrocatalytic reduction of carbon monoxide to prepare C 2+ alcohol (ethanol and n-propanol) and its application. BACKGROUND

[0002] At present, due to the overuse of fossil fuels, a large amount of CO2 is emitted, resulting in a series of environmental problems such as global warming and ocean acidification. In order to solve these problems, people put forward the strategy of artificial fixation of carbon dioxide, among which electrocatalytic reduction of carbon dioxide attracts people's attention because of its environmental protection, high efficiency and simple operation. Compared with neutral or acidic electrolyte environment, alkaline electrolyte is more conducive to the reduction of CO2 to generate high value-added products. However, CO2 is easy to form bicarbonate in alkaline electrolyte, which is not conducive to the activity conversion of electrocatalytic reaction. Since CO is a key intermediate of electroreduction of CO2, in the industry, direct electrocatalytic reduction of CO in alkaline electrolyte can avoid the formation of bicarbonate and efficiently convert CO2 into high value-added products. 2+ alcohol.

[0003] C 2+ alcohol (ethanol and n-propanol) as an important chemical product is widely used in important fields such as chemical industry, medical and health care, food industry and agricultural production, and the use of carbon monoxide electrocatalytic reduction to obtain C 2+ alcohol has important industrial value. However, due to the competition of hydrogen evolution side reaction and the factors such as high overpotential, the current faradic efficiency of electrocatalytic reduction of carbon monoxide to prepare C 2+ alcohol is still at a low level, which has a large gap with the industrial application level. It is a difficult problem in current technology to develop a catalyst with high catalytic efficiency for industrial production of C 2+ alcohol. SUMMARY

[0004] The present application aims to solve the above problems in the prior art, and provides a catalyst for electrocatalytic reduction of carbon monoxide to prepare C 2+ alcohol and its preparation method. By means of precise control of Cu + / Cu 0 ratio and polyhedral morphology regulation in the catalyst, the coverage of reaction intermediates is improved, and a catalyst with high efficiency, selectivity and reaction activity is prepared for industrial electrocatalytic reduction of carbon monoxide to prepare C2+ Alcohol. The catalyst in the method is optimal C 2+ The faradic efficiency of alcohol can reach 58.3% (in which the faradic efficiency of ethanol is 27.5%, and the faradic efficiency of n-propanol is 30.8%), and the product has high added value.

[0005] To achieve the above object, the application adopts the following technical scheme:

[0006] An electrocatalytic reduction of carbon monoxide to prepare C 2+ The preparation method of the catalyst for alcohol includes the following steps:

[0007] 1) Preparation of 26 face cuprous oxide: dissolve copper salt precursor in deionized water, water bath stirring, dropwise add NaOH to the solution, after uniform stirring, add glucose, stir to make it react fully; after the reaction is completed, wash with water and ethanol for several times, centrifugal, vacuum drying, to obtain 26 face cuprous oxide powder;

[0008] 2) Preparation of copper cage catalyst: disperse a certain amount of 26 face cuprous oxide powder in ethylene glycol, water bath stirring, dropwise add a certain amount of NaOH to the solution, after fully stirring, add a certain amount of hydroxylamine, react for a certain time, after the reaction is completed, wash with water and ethanol for several times, centrifugal, vacuum drying, to obtain copper cage powder; place the copper cage powder in a joule heat instrument, heat to a certain temperature by joule heat, cool to room temperature and take out, finally get the copper cage catalyst by electro-reduction.

[0009] The copper salt precursor in step 1) of the application is selected from one or more of copper acetate, copper nitrate, copper sulfate pentahydrate, and tetraammine copper sulfate.

[0010] In step 1) of the application, the water bath stirring, dropwise add NaOH to the solution, control the water bath temperature to be 30-90℃, the concentration of NaOH is 2-8mol / L, and the molar ratio of NaOH to copper salt is 1:0.02-0.25.

[0011] In step 2) of the application, the dispersion concentration of 26 face cuprous oxide powder in ethylene glycol is 0.2-3mg / mL.

[0012] In step 2) of the application, the water bath stirring, dropwise add a certain amount of NaOH to the solution, control the water bath temperature to be 30-90℃, the concentration of NaOH is 2-8mol / L, and the molar ratio of NaOH to 26 face cuprous oxide powder is 1:0.0012-0.028.

[0013] In step 2) of the application, the concentration of hydroxylamine is 0.2-2.5mol / L, the molar ratio of hydroxylamine to 26 face cuprous oxide powder is 1:0.003-0.015, and the control reaction time is 0.5-8h.

[0014] In step 2) of the present application, the Joule heat heating and the electric reduction are controlled as follows: the temperature of the Joule heat is 700-950 DEG C, and the maintaining time is 0.5-2 s; the cathode potential of the electric reduction is-1.2 to-2.0 V (vs Ag / AgCl), and the maintaining time is 2-15 min.

[0015] In step 2) of the present application, the copper cage catalyst contains one or more of zero-valence, one-valence and two-valence of copper, wherein Cu + / Cu 0 The ratio of Cu

[0016] The catalyst prepared by the above preparation method is applied to the electrocatalytic reduction of carbon monoxide to generate C 2+ alcohol, the electrolyte is potassium hydroxide solution, the flow rate of the reaction gas carbon monoxide is controlled according to the reaction scale, and the carbon monoxide is reduced to C 2+ alcohol under the condition of-1.2 V to-2.0 V (vs Ag / AgCl) cathode potential.

[0017] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0018] 1. The catalyst provided by the present application has good electrocatalytic carbon monoxide reduction performance, and compared with similar materials, it performs excellently in the Faraday efficiency of C 2+ alcohol.

[0019] 2. The catalyst provided by the present application has appropriate Cu + / Cu 0 ratio and polyhedral morphology wrapped by nanoparticles, which improves the coverage of reaction intermediates and further improves the selectivity and activity of the material in reducing carbon monoxide to C 2+ alcohol.

[0020] 3. The catalyst provided by the present application has wide raw material sources and low price, the preparation process is simple and environmentally friendly, the whole electrocatalytic reduction reaction process is carried out at normal temperature and pressure, the electrolyte used is a common solution without adding any organic matter, and the generated C 2+ alcohol has high added value, clean fuel, convenient transportation and broad market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0021] Fig. 1 It is the X-ray diffraction image of the copper cage catalyst in Example 1;

[0022] Fig. 2 It is the scanning electron microscope image of the copper cage catalyst in Example 1;

[0023] Fig. 3 Figure 1 is a graph of the electrocatalytic performance of the copper cage catalyst of Example 1. DETAILED DESCRIPTION

[0024] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects more clear, specific, the following will be combined with the drawings and examples, make further detailed description of the present application.

[0025] Example 1

[0026] The preparation of the catalyst of the present embodiment is as follows:

[0027] 1) 3g of copper nitrate precursor was dissolved in deionized water, after stirring in a water bath at 70°C for 5min, 30mL of NaOH (5mol / L) was added dropwise into the solution;

[0028] 2) The above mixed solution was stirred at 70°C for more than 5min;

[0029] 3) 0.6g of glucose was added to the above solution, and stirred for 30min to make the reaction complete; after the reaction was completed, it was washed several times with water and ethanol, centrifuged and dried in a vacuum drying oven to obtain 26-face cuprous oxide powder;

[0030] 4) 0.06g of 26-face cuprous oxide powder was dispersed in 150mL of ethylene glycol, after stirring in a water bath at 60°C for 10min, 50mL of NaOH (5mol / L) was added dropwise into the solution;

[0031] 5) The above mixed solution was stirred at 60°C for more than 5min;

[0032] 6) 50mL of hydroxylamine (1.1mol / L) was added to the above solution, and the reaction was carried out for 6h; after the reaction was completed, it was washed several times with water and ethanol, centrifuged and dried in a vacuum drying oven to obtain copper cage powder.

[0033] The copper cage powder was placed in a joule heat instrument, and heated to 700°C for 1s and then cooled to room temperature and taken out. Then it was electro-reduced, the cathode potential was controlled at -1.8V (vs Ag / AgCl) for 5min, and finally Cu + / Cu 0 The ratio of the copper cage catalyst was 1:0.34 (the ratio was measured and analyzed by X-ray photoelectron spectroscopy), see Figs. 1-2 , the XRD and TEM graphs of the copper cage catalyst prepared in the present embodiment, in the XRD graph, the mark H-Cu-6h represents the copper cage catalyst prepared in the present embodiment, from the graph, it can be seen that the copper cage catalyst prepared in the present embodiment has Cu2O and Cu peaks.

[0034] The catalyst prepared in this example was applied to the electrocatalytic reduction of carbon monoxide. Specifically, the copper cage catalyst prepared in this example was dispersed in 1920 μL of isopropanol solvent, 80 μL of Nafion was added, and the mixture was ultrasonically dispersed. The catalyst was then dropped onto a carbon paper gas diffusion layer by hand coating, and dried. The dried catalyst was clamped as a working electrode using an electrode clamp, a saturated silver chloride electrode was used as a reference electrode, and a platinum plate was used as a counter electrode to form a three-electrode system. The three electrodes were tested in an H-type electrolysis cell. The electrolyte was 30 mL of 1 mol / L potassium hydroxide solution in each electrode chamber. The reaction gas was high-purity carbon monoxide gas, and the flow rate of the gas was controlled at 14 mL / min. Carbon monoxide was reduced to C 2+ alcohols at a cathode potential of -1.2 V to -2.0 V. The faradic efficiency of C 2+ alcohols was 58.3% (the faradic efficiency of ethanol was 27.5%, and the faradic efficiency of n-propanol was 30.8%, see Fig. 3 .

[0035] Example 2

[0036] The catalyst of this example was prepared as follows:

[0037] 1) 3 g of copper nitrate precursor was dissolved in deionized water, and 30 mL of NaOH (5 mol / L) was added dropwise to the solution after stirring in a 70°C water bath for 5 min;

[0038] 2) The mixed solution was stirred at 70°C for more than 5 min;

[0039] 3) 0.6 g of glucose was added to the solution, and the mixture was stirred for 30 min to complete the reaction. After the reaction was completed, the mixture was washed several times with water and ethanol, centrifuged, and dried in a vacuum drying oven to obtain 26-sided cuprous oxide powder;

[0040] 4) 0.06 g of 26-sided cuprous oxide powder was dispersed in 150 mL of ethylene glycol, and 50 mL of NaOH (5 mol / L) was added dropwise to the solution after stirring in a 60°C water bath for 10 min;

[0041] 5) The mixed solution was stirred at 60°C for more than 5 min;

[0042] 6) 50 mL of hydroxylamine (1.1 mol / L) was added to the solution, and the mixture was reacted for 1 h. After the reaction was completed, the mixture was washed several times with water and ethanol, centrifuged, and dried in a vacuum drying oven to obtain copper cage powder.

[0043] The copper cage powder was placed in a Joule heating instrument, heated to 700°C by Joule heating for 1 s, then cooled to room temperature and taken out. Then, through electro-reduction, the cathode potential was controlled at -1.8 V (vs Ag / AgCl) for 5 min, and finally Cu + / Cu 0 The copper cage catalyst had a ratio of 1:0.41 (the ratio was measured and analyzed by X-ray photoelectron spectroscopy).

[0044] The catalyst prepared in this example was applied to the electrocatalytic reduction of carbon monoxide. Specifically, the copper cage catalyst prepared in this example was dispersed in 1920 μL of isopropanol solvent, 80 μL of Nafion was added, and ultrasonic dispersion was performed. The catalyst was uniformly dispersed on the gas diffusion layer carbon paper by hand coating, and then dried. The dried catalyst was clamped as a working electrode by using an electrode clamp, saturated silver chloride was used as a reference electrode, and a platinum sheet was used as a counter electrode. The three electrodes formed a three-electrode system, and the test was performed in an H-type electrolysis cell. The electrolyte: 30 mL of 1 mol / L potassium hydroxide solution was placed in each electrode chamber. The reaction gas: high-purity carbon monoxide gas, the flow rate of which was controlled at 14 mL / min. Under the condition of a cathode potential of -1.2 V to -2.0 V, carbon monoxide was reduced to C 2+ alcohols. The faradic efficiency of C 2+ alcohols could reach 47.7% (the faradic efficiency of ethanol was 19.2%, and the faradic efficiency of n-propanol was 28.5%.

[0045] Example 3

[0046] The catalyst of this example was prepared as follows:

[0047] 1) 3 g of copper nitrate precursor was dissolved in deionized water, and 30 mL of NaOH (5 mol / L) was added dropwise to the solution after stirring in a water bath at 70°C for 5 min;

[0048] 2) The above mixed solution was stirred at 70°C for more than 5 min;

[0049] 3) 0.6 g of glucose was added to the above solution, and stirred for 30 min to complete the reaction. After the reaction was completed, the product was washed several times with water and ethanol, centrifuged, and dried in a vacuum drying oven to obtain 26-sided cuprous oxide powder;

[0050] 4) 0.06 g of 26-sided cuprous oxide powder was dispersed in 150 mL of ethylene glycol, and 50 mL of NaOH (5 mol / L) was added dropwise to the solution after stirring in a water bath at 60°C for 10 min;

[0051] 5) The above mixed solution was stirred at 60°C for more than 5 min;

[0052] 6) 50 mL of hydroxylamine (1.1 mol / L) was added to the above solution, and the reaction was carried out for 0.5 h; after the reaction was completed, the product was washed several times with water and ethanol, centrifuged, and dried in a vacuum drying oven to obtain copper cage powder.

[0053] The copper cage powder was placed in a Joule heat instrument, heated to 700°C for 1 s, and then cooled to room temperature and taken out. Then, through electro-reduction, the cathode potential was controlled at -1.8 V (vs Ag / AgCl) for 5 min, and finally Cu + / Cu 0 with a proportion of 1:0.57 (the ratio was measured and analyzed by X-ray photoelectron spectroscopy).

[0054] The catalyst prepared in this example was applied to the electrocatalytic reduction of carbon monoxide. Specifically, the copper cage catalyst prepared in this example was dispersed in 1920 μL of isopropanol solvent, 80 μL of Nafion was added, and ultrasonic dispersion was carried out. The catalyst was drop-coated on a gas diffusion layer carbon paper by hand, and then dried. After drying, the catalyst was clamped as a working electrode by using an electrode clamp, a saturated silver chloride electrode was used as a reference electrode, and a platinum sheet was used as a counter electrode, to form a three-electrode system. The three electrodes were tested in an H-type electrolysis cell. The electrolyte: 30 mL of 1 mol / L potassium hydroxide solution was placed in each electrode chamber. The reaction gas: high-purity carbon monoxide gas, the flow rate of which was controlled at 14 mL / min. Under the conditions of a cathode potential of -1.2 V to -2.0 V, carbon monoxide was reduced to C 2+ alcohols. The faradic efficiency of C 2+ alcohols could reach 42.5% (the faradic efficiency of ethanol was 20.2%, and the faradic efficiency of n-propanol was 22.3%).

Claims

1. An electrocatalytic reduction method for preparing C from carbon monoxide 2+ The method using alcohols is characterized by: The electrolyte is potassium hydroxide solution, and the reactant gas is carbon monoxide. Under a cathode potential of -1.2V to -2.0V (vs Ag / AgCl), carbon monoxide is electrocatalytically reduced to C using a copper cage catalyst. 2+ alcohol; The preparation method of the copper cage catalyst includes the following steps: 1) Preparation of 26-faceted cuprous oxide: Dissolve the copper salt precursor in deionized water, then add NaOH dropwise, then add glucose solution. After the reaction is complete, wash, centrifuge, and dry to obtain 26-faceted cuprous oxide powder. 2) Preparation of copper cage catalyst: 26-sided cuprous oxide powder was dispersed in ethylene glycol, then NaOH was added dropwise, followed by hydroxylamine. After the reaction was completed, the powder was washed, centrifuged, and dried to obtain copper cage powder. The copper cage powder was placed in a Joule heating apparatus, heated to a certain temperature by Joule heating, cooled to room temperature and removed. Finally, it was electroreduced to obtain copper cage catalyst. In step 2), the copper cage catalyst has copper with the main valence state Cu. + / Cu 0 The ratio ranges from 1:0.34 to 1.

2. The electrocatalytic reduction of carbon monoxide to prepare C as described in claim 1 2+ The method using alcohols is characterized by: In step 1), the copper salt precursor is selected from one or more of copper acetate, copper nitrate, copper sulfate pentahydrate, and tetraamminecopper sulfate.

3. The electrocatalytic reduction of carbon monoxide to prepare C as described in claim 1 2+ The method using alcohols is characterized by: In step 1), the concentration of NaOH is 2-8 mol / L, and the molar ratio of NaOH to copper salt precursor is 1:0.02-0.

25.

4. The electrocatalytic reduction of carbon monoxide to prepare C as described in claim 1 2+ The method using alcohols is characterized by: In step 2), the dispersion concentration of cuprous oxide powder in ethylene glycol is 0.2–3 mg / mL.

5. The electrocatalytic reduction of carbon monoxide to prepare C as described in claim 1 2+ The method using alcohols is characterized by: In step 2), the concentration of NaOH is 2-8 mol / L, and the molar ratio of NaOH to cuprous oxide powder is 1:0.0012-0.

028.

6. The electrocatalytic reduction of carbon monoxide to prepare C as described in claim 1 2+ The method using alcohols is characterized by: In step 2), the concentration of hydroxylamine is 0.2–2.5 mol / L, the molar ratio of hydroxylamine to cuprous oxide powder is 1:0.003–0.015, and the reaction time is 0.5–8 h.

7. The electrocatalytic reduction of carbon monoxide to prepare C as described in claim 1 2+ The method using alcohols is characterized by: In step 2), the Joule heating temperature is 700–950℃ and the duration is 0.5–2s; the cathode potential of electroreduction is controlled at -1.2–-2.0V (vs Ag / AgCl) and the duration is 2–15min.

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