Copper-based electrocatalytic material, preparation method and application thereof

Abstract

The present application relates to the technical field of electrocatalytic CO2 reduction, and specifically discloses a copper-based electrocatalytic material, which comprises a plurality of element-doped copper-based nanowires, wherein the doping elements are one or more of S, F, Br, N and O. The present application also discloses a preparation method of the copper-based electrocatalytic material, which comprises: mixing a solution containing a phenylthiophenol ligand with a copper salt solution to obtain a suspension; performing ultrasonic treatment, heating, stirring and aging treatment on the suspension, and then performing centrifugal, washing and drying treatment to obtain a copper-based nanowire precursor; performing calcination on the copper-based nanowire precursor; and performing in-situ electrochemical activation treatment on the calcined copper-based nanowire precursor. The preparation method is simple and effective, and does not require multi-step doping. When the copper-based electrocatalytic material is applied to an electrocatalytic carbon dioxide reduction reaction to prepare ethylene, the copper-based electrocatalytic material has high ethylene selectivity and can work efficiently and stably at a large current density.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic CO2 reduction, and in particular to a copper-based electrocatalytic material and a preparation method and application thereof. Background Art

[0002] Electrochemical catalytic reduction of CO2 to small organic molecules is one of the important ways to realize the resource utilization of CO2, reduce the CO2 content in the atmosphere, and alleviate the "greenhouse effect". It is also an important link in establishing a new carbon resource balance system. The electrocatalytic CO2 reduction reaction involves a multi-electron transfer process, which puts forward new requirements for catalyst design. Copper is the only catalyst that can electrocatalyze the reduction of CO2 to generate C1 and C 2+ The metal content of the product is crucial for regulating its catalytic selectivity. Currently, research on Cu-based catalysts focuses on the influence of catalyst size, composition, exposed crystal faces, and chemical valence on CO2 electroreduction catalytic performance. However, achieving highly selective and active catalysts remains unsatisfactory. Therefore, the search for and development of efficient and stable catalysts to improve catalytic efficiency and optimize product selectivity plays a crucial role in the advancement of electrocatalytic CO2 reduction.

[0003] However, the copper-based nano-electrocatalytic materials obtained by the currently commonly used precipitation method or sacrificial template method have complex surface active component morphology and variable crystal faces, resulting in poor ethylene selectivity. During the electrocatalytic process, the spatial structure of the above copper-based electrocatalytic materials is unstable, especially at higher current densities (>500mAcm -2 ) under low temperature, catalyst agglomeration is likely to occur, leading to structural damage and rapid performance degradation.

[0004] CN112316965A discloses a method for preparing a laccase-copper phosphate nanoflower material, belonging to the field of electrocatalysis. This method involves ultrasonically mixing laccase in a phosphate buffer solution, adding copper sulfate solution, allowing the mixture to stand, and then centrifuging the precipitate. The precipitate is washed with ethanol and vacuum-dried to obtain the laccase-copper phosphate La / Cu3(PO4)2 nanoflower.

[0005] CN103303962B discloses a method for preparing nano-copper oxide using a solid-phase template method. Equal amounts of copper salt and sodium carbonate are ground separately, transferred to the same mortar, and ligninamine is added to the mortar and further ground to obtain a mixture. The resulting mixture is ultrasonically cleaned with deionized water and centrifuged. The precipitate is washed with deionized water, then with anhydrous ethanol, and centrifuged. The separated solid is dried in a constant-temperature drying oven. Finally, the dried solid is calcined at high temperature to obtain the nano-copper oxide.

[0006] Therefore, developing efficient and stable catalysts, improving catalytic efficiency, and optimizing product selectivity are of great strategic significance for the research on electrocatalytic CO2 reduction. SUMMARY

[0007] The present application aims to overcome the problems of low activity, low ethylene selectivity and poor stability of copper-based catalysts for electrocatalytic CO2 reduction in the prior art, and provides an element-doped copper-based electrocatalytic material, a preparation method and application thereof.

[0008] To achieve the above-mentioned purpose, the first aspect of the present application provides a copper-based electrocatalytic material, wherein the copper-based electrocatalytic material comprises a plurality of element-doped copper-based nanowires.

[0009] The second aspect of the present application provides a preparation method of a copper-based electrocatalytic material, wherein the preparation method comprises:

[0010] (1) mixing a solution containing a benzene thiol ligand with a copper salt solution to obtain a suspension;

[0011] (2) performing ultrasonic, heating, stirring and aging treatment on the suspension, and then performing centrifugation, washing and drying treatment to obtain a copper-based nanowire precursor;

[0012] (3) calcining the copper-based nanowire precursor;

[0013] (4) performing in-situ electrochemical activation treatment on the calcined copper-based nanowire precursor to obtain the copper-based electrocatalytic material.

[0014] The third aspect of the present application provides application of the copper-based electrocatalytic material in electrocatalytic carbon dioxide reduction reaction to prepare ethylene.

[0015] Through the above technical solution, the benzene thiol ligand is used as a precipitant, and the copper ions and the benzene thiol ligand are used to form a high-coordination, multi-element-doped copper-based nanowire precursor-metal organic framework (MOF) material by self-assembly; the benzene thiol ligand contains a large amount of doping elements such as sulfur and oxygen, and under calcination conditions, pyrolysis forms a multi-element-doped copper-based catalyst material; finally, through electrochemical activation treatment, in-situ reduction and electrochemical reconstruction, the copper-based catalyst material is obtained.

[0016] By controlling the process conditions (ultrasonic, heating, stirring, aging, centrifugation and drying) in the preparation process, the copper-based catalyst material prepared has a nanowire structure, a length of 1-10 μm and a diameter of 20-200 nm; by controlling the calcination temperature, the multi-element-doped copper-based nanowire precursor is fully pyrolyzed, and at the same time, the loss of doping elements and the occurrence of metal element sintering phenomenon are reduced, so that the copper-based catalyst material has a specific surface area of 500-2000 m Figure 1 and Figure 4 It can be seen that the copper-based nanowire obtained has a loose and porous surface, and the sintering phenomenon is not obvious, and the catalyst has a specific surface area of 500-2000 m 2 / g and a pore volume of 50-200 cm3 / g. The size and morphology of the copper-based catalyst of the present invention are conducive to promoting the electrocatalytic reduction of CO2 to produce ethylene and improving the ethylene selectivity. The fluorine- and sulfur-doped copper-based catalyst prepared in Example 1 of the present invention has a current density of 800 mA / cm 2 When the Faraday efficiency of ethylene is 55.2%, and at 1200mA / cm 2 At high current density, its ethylene Faraday efficiency is still 30.0%. By controlling the voltage or current value, scan number or activation time during electrochemical activation, the copper-based catalyst material is well activated and its electrocatalytic CO2 reduction to ethylene performance is improved while also ensuring good catalyst stability. The obtained copper-based catalyst is applied to electrocatalytic CO2 reduction. At a current density of 800 mA / cm 2 The ethylene Faradaic efficiency was 55.2% when the reaction was carried out for 48 hours, and even after 48 hours, the ethylene Faradaic efficiency was still high (50%). This shows that the copper-based catalyst has good performance in electrocatalytic CO2 reduction to ethylene and can operate efficiently and stably at high current density.

[0017] The preparation process of the copper-based catalytic material is simple and effective, and does not require multi-step doping. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a scanning electron microscope image of the copper-based electrocatalytic material prepared in Example 1;

[0019] Figure 2 This is a performance test comparison chart of the copper-based electrocatalytic material and nano copper oxide prepared in Example 1;

[0020] Figure 3 This is a graph showing the constant current stability test of the copper-based electrocatalytic material prepared in Example 1;

[0021] Figure 4 is a transmission electron microscope image of the copper-based electrocatalytic material prepared in Example 1. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0024] A first aspect of the present invention provides a copper-based electrocatalytic material, wherein the copper-based electrocatalytic material comprises a plurality of element-doped copper-based nanowires.

[0025] The copper-based electrocatalytic material described in the present invention comprises a plurality of copper-based nanowires doped with the elements, and the plurality of copper-based nanowires doped with the elements are loosely stacked together to form the copper-based catalytic material. The plurality of copper-based nanowires doped with the elements have a nanostructure, and gaps are left between the nanowires, which increases the specific surface area and pore volume of the copper-based catalyst material, and is beneficial to improving the activity of the catalyst when used for electrocatalytic CO2 reduction to produce ethylene. In addition, the doping elements in the copper-based nanowires doped with the elements exist inside and on the surface of the nanowires, which is beneficial to promoting the production of ethylene products; the doping elements on the surface of the copper-based nanowires doped with the elements are precipitated in large quantities during the reduction process, and some heteroatoms remaining on the subsurface or deeper levels affect the adsorption and production process of the intermediates, so that some positively valenced Cu (Cu*) is retained on the catalyst surface, and the Cu* and Cu in adjacent positions are not included in the catalyst surface. 0 It is beneficial to the coupling between *CO intermediates to generate multi-carbon products, improving the ethylene selectivity in the electrocatalytic CO2 reduction reaction and the stability at high current density.

[0026] In the present invention, the copper-based electrocatalytic material can be prepared by the preparation method provided in the second aspect of the present invention.

[0027] According to the copper-based electrocatalytic material of the present invention, preferably, in the copper-based electrocatalytic material, the packing density of the plurality of copper-based nanowires doped with the element is 0.3-0.4 g / cm 3 .

[0028] In some embodiments of the present invention, in the copper-based electrocatalytic material, the packing density of the plurality of copper-based nanowires doped with the element is 0.35 g / cm 3 , 0.8g / cm 3 , 0.7g / cm 3 , 0.6g / cm 3 , 0.5g / cm 3 .

[0029] According to the present invention, in order to make the copper-based electrocatalytic material have a large specific surface area and pore volume, and to improve the activity of the catalyst in electrocatalytic CO2 reduction to produce ethylene, preferably, in the copper-based electrocatalytic material, the diameter of the element-doped copper-based nanowires is 20-200nm, the length is 1-10μm, and the specific surface area is 1500-2000m 2 / g, pore volume of 150-200cm 3 / g.

[0030] In some embodiments of the present invention, preferably, in the copper-based electrocatalytic material, the diameters of the element-doped copper-based nanowires are 20-50 nm, 60-100 nm, 100-200 nm, 150-200 nm, respectively, and the lengths are 1-10 μm, respectively, and the specific surface area is 2000 m 2 / g、1200m 2 / g、800m 2 / g、500m 2 / g、1500m 2 / g, pore volume is 200cm 3 / g、120cm 3 / g、80cm 3 / g, 50cm 3 / g、150cm 3 / g.

[0031] According to the copper-based electrocatalytic material of the present invention, preferably, in the element-doped copper-based nanowires, the copper element is in the form of Cu 2+ 、Cu + 、Cu 0 exists in one or more forms.

[0032] In some embodiments of the present invention, preferably, in the element-doped copper-based nanowires, the copper element is mainly in the form of Cu 2+ 、Cu + or Cu 0 exists in the form of .

[0033] According to the preparation method of the second aspect of the present invention, specifically, when the nanowire precursor formed by self-assembly of the metal-organic framework material is calcined in air, the doping element is partially lost, and most of the copper element is in the form of Cu 2+ When sintered under nitrogen, the doping elements are less lost, and most of the copper elements are in the form of Cu + When calcined under hydrogen, most of the doping elements are lost, and most of the copper elements are in the form of Cu 0 In addition, when calcined at different temperatures under the same atmosphere, the components of the catalyst also vary.

[0034] The present invention uses surface enhanced Raman spectroscopy to detect the existing form of copper elements in the element-doped copper-based nanowires.

[0035] According to the copper-based electrocatalytic material of the present invention, preferably, in the element-doped copper-based nanowires, the doping element is selected from non-metallic elements, preferably one or more selected from S, F, Br, N, and O.

[0036] In some embodiments of the present invention, preferably, in the element-doped copper-based nanowires, the doping elements are F and S, Br and S, F, Br, N and S, S respectively.

[0037] According to the present invention, in order to make the copper-based electrocatalytic material have better electrocatalytic CO2 reduction activity to produce ethylene, ethylene selectivity and stability at a large current density, preferably, in the element-doped copper-based nanowires, the content of the doping element is 0.1-10wt%.

[0038] In the present invention, the composition and structure of the copper-based electrocatalytic material can be determined by scanning electron microscopy, inductively coupled plasma spectroscopy and BET specific surface area testing, or by the amount of each material added during the preparation process.

[0039] A second aspect of the present invention provides a method for preparing a copper-based electrocatalytic material, wherein the method comprises:

[0040] (1) mixing a solution containing a thiophenol ligand with a copper salt solution to obtain a suspension;

[0041] (2) subjecting the suspension to ultrasonic, heating, stirring and aging treatments, and then to centrifugation, washing and drying to obtain a copper-based nanowire precursor;

[0042] (3) calcining the copper-based nanowire precursor;

[0043] (4) The calcined copper-based nanowire precursor is subjected to in-situ electrochemical activation treatment to obtain the copper-based electrocatalytic material.

[0044] The preparation method of the present invention uses thiophenol ligands as precipitants, and copper ions and thiophenol ligands self-assemble to form a highly coordinated, multi-element-doped copper-based nanowire precursor—a metal-organic framework (MOF) material. The thiophenol ligands contain a large amount of doping elements such as sulfur and oxygen, and under calcination conditions, they pyrolyze to form a multi-element-doped copper-based catalytic material. Finally, the copper-based catalytic material is electrochemically reconstructed through in-situ reduction and electrochemical activation. As described above, the copper-based electrocatalytic material prepared using the preparation method of the present invention comprises a plurality of the aforementioned element-doped copper-based nanowires, which are loosely stacked together to form the copper-based catalytic material. When used for electrocatalytic CO2 reduction to produce ethylene, this improves catalyst activity, ethylene selectivity, and stability at high current densities.

[0045] According to the preparation method of the present invention, preferably, in step (1), the copper salt is selected from one or more of copper chloride, copper nitrate and copper sulfate;

[0046] According to the application, in order to make the copper salt and the ligand self-assemble into nanowire structure after complexation, and to make the copper salt and the ligand have spatial stability after complexation and not easy to agglomerate, preferably, in the step (1), the molar concentration of the copper salt solution is 1-100 mmol / L.

[0047] More preferably, the molar concentration of the copper salt solution is 37.2-100 mmol / L.

[0048] In some embodiments of the application, in the step (1), the molar concentration of the copper salt solution is 37.2 mmol / L, 10 mmol / L, 90 mmol / L, 100 mmol / L and 50 mmol / L.

[0049] According to the preparation method of the application, preferably, in the step (1), the phenylthiol ligand is selected from one or more of 4-bromophenylthiol, 4-fluorophenylthiol, 4-aminophenylthiol and 4-hydroxyphenylthiol.

[0050] According to the application, in order to form a high coordination structure of the phenylthiol ligand and copper ions, form an active site conducive to C-C coupling, and avoid local agglomeration during the dropwise addition process, form large particles and lose the advantage of micro-morphology, preferably, in the step (1), the molar concentration of the ligand solution is 100-1000 mmol / L.

[0051] More preferably, the molar concentration of the ligand solution is 100-500 mmol / L.

[0052] In some embodiments of the application, in the step (1), the molar concentration of the ligand solution is 264 mmol / L, 100 mmol / L, 300 mmol / L and 500 mmol / L.

[0053] According to the preparation method of the application, preferably, in the step (1), the mixing method of the ligand solution and the copper salt solution is: adding the solution containing the phenylthiol ligand dropwise into the copper salt solution to obtain a suspension; or directly mixing the solution containing the phenylthiol ligand with the copper salt solution and then stirring to obtain a suspension.

[0054] According to the application, the solvent in the solution containing the phenylthiol ligand and the copper salt solution is not particularly limited, and dissolution is sufficient, preferably, the solvent is selected from one or more of ethanol, diethyl ether and carbon disulfide.

[0055] According to the preparation method of the application, preferably, in the step (1), the volume ratio of the copper salt solution to the ligand solution is 0.5:1-2:1.

[0056] In some embodiments of the present invention, preferably, in step (1), the mixing volume ratio of the copper salt solution to the ligand solution is 1:1.

[0057] According to the preparation method of the present invention, preferably, in the step (2), the ultrasonic power is 50-500W, the ultrasonic time is 0.01-2h, the heating temperature is 60-100°C, the stirring rate is 100-1000rpm, the aging time is 0.01-12h, the centrifugal rate is 2000-10000rpm, and the drying temperature is 50-100°C.

[0058] According to the present invention, in order to control the length and diameter of the element-doped copper-based nanowires contained in the copper-based electrocatalytic material and ensure a higher product yield, preferably, in the step (2), the ultrasonic power is 500W, the ultrasonic time is 1h, the heating temperature is 60-80°C, the stirring rate is 400-800rpm, the aging time is 1-12h, the centrifugal rate is 8000rpm, and the drying temperature is 60-90°C.

[0059] In some embodiments of the present invention, preferably, in step (2), the ultrasonic power is 500W, 200W, and 250W, respectively; the ultrasonic time is 1h, 2h, and 1.5h, respectively; the heating temperature is 80°C, 90°C, 70°C, and 60°C; the stirring rate is 400rpm, 800rpm, 600rpm, and 700rpm; the aging time is 1h, 6h, and 12h; the centrifugal rate is 8000rpm, 10000rpm, and 5000rpm; and the drying temperature is 60°C, 90°C, and 50°C.

[0060] According to the preparation method of the present invention, in the step (2), the washing is performed by alternating washing with water and ethanol.

[0061] According to the preparation method of the present invention, preferably, in step (3), the calcination temperature is 400-1000°C, the calcination time is 1-5h, the heating rate is 0.5-10°C / min, and the calcination atmosphere is selected from one or more of air, nitrogen and hydrogen.

[0062] According to the present invention, in order to fully pyrolyze the multi-element doped copper-based nanowire precursor and at the same time reduce the loss of doping elements and the occurrence of metal element sintering, preferably, in the step (3), the calcination temperature is 600-700°C, the calcination time is 2-4h, and the heating rate is 0.5-2°C / min.

[0063] In some embodiments of the present invention, preferably, in step (3), the calcination temperature is 700°C, 900°C, or 600°C; the calcination time is 2h, 4h, 5h, or 1h; and the heating rate is 2°C / min, 5°C / min, 10°C / min, or 0.5°C / min.

[0064] According to the preparation method of the present invention, preferably, in the step (4), the electrochemical activation treatment method is selected from one or more of linear sweep voltammetry, cyclic voltammetry, constant current method and constant voltage method.

[0065] According to the present invention, in order to effectively activate the calcined copper-based nanowire precursor and ensure the stability of the obtained copper-based catalytic material, preferably, in the step (4), when the linear sweep voltammetry and cyclic voltammetry are used, a three-electrode system is adopted, the voltage is relative to the reversible hydrogen electrode (VS.RHE), the voltage range is between -2.5 and 0V, and the scan or cycle is 1-80 times.

[0066] More preferably, when the linear sweep voltammetry and cyclic voltammetry are used, the voltage range is between -1.8 and -1.2 V, and the scans or cycles are performed 40 times.

[0067] Preferably, in step (4), when the constant current method is used, the current density is between -10 and -1500 mA / cm 2 The reaction time is 0.05-3h.

[0068] More preferably, when the constant current method is used, the current density is -100 mA / cm 2 , the reaction time is 5min.

[0069] Preferably, in step (4), when the constant voltage method is adopted, the voltage range is between -3.5 and -1.5 V, and the reaction time is 0.05-3 h.

[0070] More preferably, when the constant voltage method is adopted, the voltage is -1.6 V and the reaction time is 5 min.

[0071] According to the present invention, in step (4), preferably, the calcined solid is coated on the electrode material and then electrochemical in-situ activation is performed.

[0072] According to the present invention, in step (4), more preferably, the calcined solid is coated on a carbon electrode material and then electrochemically activated in situ; specifically, the carbon electrode material is selected from carbon paper, carbon felt or carbon cloth.

[0073] In some embodiments of the present invention, preferably, the carbon electrode material is a carbon paper electrode.

[0074] The third aspect of the present invention provides the use of the copper-based electrocatalytic material in the electrocatalytic reduction reaction of carbon dioxide to produce ethylene.

[0075] The copper-based catalyst obtained by the present invention was applied to electrocatalytic CO2 reduction at a current density of 800 mA / cm 2 The copper-based catalyst has an ethylene Faradaic efficiency of 55.2% when the current is 1200 mA / cm 2 At a high current density of 800mA / cm 2 At the same current density, after 48 hours of electrocatalytic reduction, the copper-based catalyst's ethylene Faradaic efficiency did not significantly decrease, remaining at approximately 50%. This demonstrates that the copper-based catalyst has excellent electrocatalytic CO2 reduction performance and can operate efficiently and stably at high current densities.

[0076] The following examples are used to illustrate the technical solutions of the present invention, wherein the raw materials and reagents used are commercially available, and room temperature refers to 15-35°C.

[0077] Cupric chloride dihydrate, purity AR (≥99.0%, Shanghai test), purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0078] Copper nitrate trihydrate, purity AR (≥99.0%, Shanghai test), purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0079] Copper sulfate pentahydrate, purity AR (≥99.0%, Shanghai test), purchased from Sinopharm Chemical Reagent Co., Ltd.

[0080] 4-Bromothiophenol, 97% purity, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0081] 4-Fluorothiophenol, purity 98%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0082] 4-Aminothiophenol, purity ≥98% (GC), was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0083] 4-Hydroxythiophenol, with a purity of 97%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0084] Example 1

[0085] Preparation of fluorine- and sulfur-doped copper-based catalytic materials

[0086] A copper nitrate ethanol solution with a molar concentration of 37.2 mmol / L and a 4-fluorothiophenol ethanol solution with a molar concentration of 264 mmol / L were prepared; an equal volume of the 4-fluorothiophenol / ethanol solution was dropwise added to the copper nitrate / ethanol solution to obtain a suspension; ultrasonication (500 W) was performed for 1 hour, heating to 80° C., aging at a stirring rate of 400 rpm for 1 hour, washing alternately with water and ethanol at a centrifugal speed of 8000 rpm, and drying at 60° C.; the dried solid was calcined at 700° C. in an air atmosphere for 2 hours, wherein the heating rate was 2° C. / min; the calcined solid was coated on a carbon paper electrode, and electrochemical in situ activation was performed by a constant current method, wherein the current during the electrochemical in situ activation treatment was -100 mA / cm 2 , the treatment time is 5 minutes, and fluorine and sulfur doped copper-based catalytic materials are obtained.

[0087] The fluorine and sulfur doped copper-based catalytic materials were subjected to electron microscopy scanning and BET specific surface area measurement. Figure 1 The scanning electron microscope image shows that the fluorine- and sulfur-doped copper-based catalytic material comprises a plurality of copper-based nanowires, and the packing density of the plurality of copper-based nanowires doped with the elements is 0.35 g / cm 3 ; Among them, the diameter of the nanowire is 20-50nm and the length is 1-10μm; In addition, Figure 4 The transmission electron microscope image shown in the figure shows that the surface of the nanowire is loose and porous, with a specific surface area of ​​2000m 2 / g, pore volume is 200cm 3 / g; the content of the doping element is 5wt%.

[0088] Surface enhanced Raman spectroscopy was used to detect the fluorine and sulfur doped copper-based catalytic material prepared in Example 1. From the test results, it can be seen that the copper element is mainly in the form of Cu 2+ exists in the form of .

[0089] The fluorine and sulfur doped copper-based catalytic material prepared in Example 1 was subjected to electrochemical performance test of electrocatalytic CO2 reduction to ethylene in a flow electrolysis cell apparatus, with pure CO2 as the raw material, a flow rate of 30 mL / min, and normal temperature and pressure. The results are shown in 2. Figure 3 shown.

[0090] Figure 2 The performance test comparison chart of fluorine and sulfur doped copper-based catalytic materials and nano copper oxide is shown in the figure. It can be seen from the figure that at a current density of 800mA / cm 2 When the fluorine and sulfur doped copper-based electrocatalytic material has an ethylene Faradaic efficiency of 55.2%, and at 1200mA / cm 2The ethylene faradic efficiency of the copper-based catalytic material doped with fluorine and sulfur is still 30.0% under a large current density. It is shown that the copper-based catalytic material doped with fluorine and sulfur has a good performance of electrocatalytic reduction of CO2 to ethylene and a good selectivity of ethylene. In addition, the hydrogen faradic efficiency of the copper-based electrocatalytic material doped with multiple elements is 30.1% when the current density is 800 mA / cm 2 , and the hydrogen faradic efficiency of the copper-based electrocatalytic material doped with multiple elements is 54.8% when the current density is 1200 mA / cm 2 .

[0091] Figure 3 The constant-current stability test diagram of the copper-based catalytic material doped with fluorine and sulfur is shown in the figure. It can be seen from the figure that the overpotential of the copper-based catalytic material doped with fluorine and sulfur does not increase obviously after 48 h of testing under a current density of 800 mA / cm 2 , and the faradic efficiency of ethylene does not decrease obviously, and is still about 50%. It is shown that the copper-based catalytic material doped with fluorine and sulfur has excellent stability.

[0092] Example 2

[0093] Preparation of copper-based catalytic material doped with bromine and sulfur

[0094] An ethanol solution of copper nitrate is prepared, and the molar concentration is 10 mmol / L. An ethanol solution of 4-bromothiophenol is prepared, and the molar concentration is 100 mmol / L. Equal volumes of the 4-bromothiophenol / ethanol solution are added dropwise into the copper nitrate / ethanol solution to obtain a suspension. The suspension is ultrasonically treated (200 W) for 2 h, heated to 90°C, and aged at a stirring speed of 800 rpm for 6 h. The suspension is washed with water and ethanol alternately at a centrifugal speed of 10000 rpm, and dried at a temperature of 90°C. The dried solid is calcined at 700°C for 4 h under a nitrogen atmosphere, and the temperature increasing rate is 5°C / min. The calcined solid is coated on a carbon paper electrode, and electrochemically in-situ activated by a constant current method, and the current during the electrochemical in-situ activation is-200 mA / cm 2 , and the treatment time is 2 min. The copper-based catalytic material doped with bromine and sulfur is obtained.

[0095] The copper-based catalytic material doped with bromine and sulfur is subjected to electron microscope scanning and BET specific surface area measurement, respectively. It is shown that the copper-based catalytic material doped with bromine and sulfur prepared in Example 2 comprises a plurality of copper-based nanowires. The packing density of the plurality of element-doped copper-based nanowires is 0.8 g / cm 3 . The diameter of the nanowires is 60-100 nm, and the length is 1-10 μm. In addition, the surface of the nanowires is loose and porous, the specific surface area is 1200 m 2 / g, and the pore volume is 120 cm 3 / g.

[0096] Surface enhanced Raman spectroscopy was used to detect the bromine and sulfur doped copper-based catalytic material prepared in Example 2. From the test results, it can be seen that the copper element is mainly in the form of Cu + exists in the form of .

[0097] The bromine and sulfur doped copper-based catalytic material prepared in Example 2 was subjected to electrochemical performance testing for electrocatalytic CO2 reduction to ethylene in a flow electrolysis cell apparatus under the same test conditions as in Example 1. At a current density of 800 mA / cm 2 When the bromine and sulfur doped copper-based catalytic material has an ethylene Faraday efficiency of 20.3% and a hydrogen Faraday efficiency of 55.6%, the ethylene Faraday efficiency of the bromine and sulfur doped copper-based catalytic material is 20.3% and 55.6% respectively; 2 At high current density, its ethylene Faraday efficiency is 9.1% and hydrogen Faraday efficiency is 80.7%. 2 Under the current density, there is no significant increase in overpotential after 2 hours of testing, and the Faradaic efficiency of ethylene does not decrease significantly.

[0098] Example 3

[0099] Preparation of copper-based catalytic materials doped with bromine, fluorine, nitrogen and sulfur

[0100] A mixed ethanol solution containing copper nitrate, copper sulfate and copper chloride is prepared, wherein the molar concentration of each copper salt is 30 mmol / L; a mixed ethanol solution containing 4-bromothiophenol, 4-fluorothiophenol and 4-aminothiophenol ligands is prepared, wherein the molar concentration of each ligand is 100 mmol / L; an equal volume of the mixed thiophenol ligand / ethanol solution is added dropwise to the mixed copper salt / ethanol solution to obtain a suspension; ultrasonication (500 W) is performed for 1.5 h, heating to 70° C., aging for 12 h at a stirring rate of 600 rpm, alternating washing with water and ethanol at a centrifugal speed of 5000 rpm, and drying at 50° C.; the dried solid is calcined at 900° C. for 5 h in a hydrogen / nitrogen mixed atmosphere, wherein the heating rate is 10° C. / min; the calcined solid is coated on a carbon paper electrode, and electrochemical in situ activation is performed by a constant current method, wherein the current during the electrochemical in situ activation treatment is -100 mA / cm 2 The treatment time is 10 min. A copper-based catalytic material doped with bromine, fluorine, nitrogen and sulfur is obtained.

[0101] Electron microscope scanning and BET specific surface area measurement were performed on the copper-based catalytic materials doped with bromine, fluorine, nitrogen and sulfur, respectively. It was found that the copper-based catalytic materials doped with bromine, fluorine, nitrogen and sulfur prepared in Example 3 contained a plurality of copper-based nanowires, and the packing density of the plurality of copper-based nanowires doped with the elements was 0.7 g / cm 3 The diameter of the nanowires is 100-200nm and the length is 1-10μm. In addition, the surface of the nanowires is loose and porous, with a specific surface area of ​​800m2 / g, pore volume 80cm 3 / g.

[0102] Surface enhanced Raman spectroscopy was used to detect the copper-based catalytic material doped with bromine, fluorine, nitrogen and sulfur prepared in Example 3. The test results showed that the copper element was mainly in the form of Cu 0 exists in the form of .

[0103] The copper-based catalytic material doped with bromine, fluorine, nitrogen and sulfur prepared in Example 3 was subjected to electrochemical performance test of electrocatalytic CO2 reduction to ethylene in a flow electrolysis cell device. The test conditions were the same as those in Example 1. At a current density of 800 mA / cm 2 When the bromine, fluorine, nitrogen and sulfur doped copper-based catalytic materials have an ethylene Faraday efficiency of 27.3% and a hydrogen Faraday efficiency of 50.9%, respectively, at 1200 mA / cm 2 At high current density, its ethylene Faraday efficiency is 6.1% and hydrogen Faraday efficiency is 90.6%. 2 Under the current density, after 10 hours of testing, its overpotential did not increase significantly, and the Faradaic efficiency of ethylene did not decrease significantly.

[0104] Example 4

[0105] Preparation of sulfur-doped copper-based catalytic materials

[0106] A copper nitrate / ethanol / carbon disulfide mixed solution with a molar concentration of 100 mmol / L and a 4-hydroxythiophenol / ethanol / carbon disulfide mixed solution with a molar concentration of 500 mmol / L were prepared. An equal volume of the 4-hydroxythiophenol / ethanol / carbon disulfide mixed solution was dropwise added to the copper nitrate / ethanol / carbon disulfide mixed solution to obtain a suspension. The suspension was then ultrasonicated (500 W) for 1 hour, heated to 80°C, and aged for 12 hours at a stirring rate of 700 rpm. The suspension was then washed alternately with water and ethanol at a centrifugal speed of 8000 rpm and dried at 60°C. The dried solid was calcined at 700°C in an air atmosphere for 4 hours at a heating rate of 0.5°C / min. The calcined solid was coated on a carbon paper electrode and electrochemically activated in situ by cyclic voltammetry. The voltage range of the electrochemical in situ activation treatment was -2.5-0 V, and the reaction was repeated 80 times. This yielded a sulfur-doped copper-based catalytic material.

[0107] Electron microscopy scanning and BET specific surface area measurement were performed on the sulfur-doped copper-based catalytic material. It was found that the oxygen- and sulfur-doped copper-based catalytic material prepared in Example 4 contained a plurality of copper-based nanowires. The packing density of the plurality of copper-based nanowires doped with the element was 0.6 g / cm 3Among them, the diameter of the nanowire is 150-200nm and the length is 1-10μm. In addition, the surface of the nanowire is loose and porous, with a specific surface area of ​​500m 2 / g, pore volume 50cm 3 / g.

[0108] The sulfur-doped copper-based catalytic material prepared in Example 4 was tested by surface-enhanced Raman spectroscopy. The test results showed that the copper element was mainly in the form of Cu 2+ exists in the form of .

[0109] The sulfur-doped copper-based catalytic material prepared in Example 4 was subjected to electrochemical performance testing for electrocatalytic CO2 reduction to ethylene in a flow electrolysis cell apparatus under the same test conditions as in Example 1. At a current density of 800 mA / cm 2 When the sulfur-doped copper-based catalytic material is used, the ethylene Faraday efficiency is 30.9%, and the hydrogen Faraday efficiency is 43.6%. 2 At high current density, its ethylene Faraday efficiency is 14.3% and hydrogen Faraday efficiency is 76.3%. 2 Under the current density, after 1 hour of testing, its overpotential did not increase significantly, and the Faradaic efficiency of ethylene did not decrease significantly.

[0110] Example 5

[0111] Preparation of fluorine- and sulfur-doped copper-based catalytic materials

[0112] A copper nitrate ethanol solution with a molar concentration of 50 mmol / L and a 4-fluorothiophenol ethanol solution with a molar concentration of 100 mmol / L were prepared; an equal volume of the 4-fluorothiophenol / ethanol solution was dropwise added to the copper nitrate / ethanol solution to obtain a suspension; ultrasonication (250 W) was performed for 1 hour, heating to 60° C., and aging was performed at a stirring rate of 800 rpm for 1 hour; washing was performed alternately with water and ethanol at a centrifugal speed of 8000 rpm, and drying was performed at a temperature of 90° C.; the dried solid was calcined at 600° C. in a hydrogen atmosphere for 1 hour, wherein the heating rate was 2° C. / min; the calcined solid was coated on a carbon paper electrode, and electrochemical in-situ activation was performed by constant current method and constant voltage method, wherein the current during the electrochemical in-situ treatment was -200 mA / cm 2 The treatment time was 2 min, the voltage was -1.6 V, and the treatment time was 0.5 h. Fluorine and sulfur doped copper-based catalytic materials were obtained.

[0113] Electron microscopy scanning and BET specific surface area measurement were performed on the fluorine- and sulfur-doped copper-based catalytic materials, respectively. It was found that the fluorine- and sulfur-doped copper-based catalytic material prepared in Example 5 contained a plurality of copper-based nanowires, and the packing density of the plurality of copper-based nanowires doped with the elements was 0.5 g / cm3 ; wherein the nanowires have a diameter of 60-100 nm and a length of 1-10 μm; in addition, the nanowires have a loose porous surface, a specific surface area of 1500 m 2 / g, and a pore volume of 150 cm 3 / g.

[0114] The fluorine and sulfur doped copper-based catalytic material prepared in Example 5 is detected by surface enhanced Raman spectroscopy, and it can be known from the detection result that the copper element mainly exists in the form of Cu 0 .

[0115] The fluorine and sulfur doped copper-based catalytic material prepared in Example 5 is subjected to electrochemical performance testing of electrocatalytic CO2 reduction for preparing ethylene on a flow electrolytic cell device, and the testing conditions are the same as those in Example 1. When the current density is 800 mA / cm 2 , the ethylene Faraday efficiency of the fluorine and sulfur doped copper-based catalytic material is 40.2%, and the hydrogen Faraday efficiency is 44.9%; and when the current density is 1200 mA / cm 2 , the ethylene Faraday efficiency thereof is 3.1%, and the hydrogen Faraday efficiency is 84.7%. When the current density is 800 mA / cm 2 , the overpotential does not obviously increase after 0.5 h of testing, and the Faraday efficiency of ethylene also does not obviously decrease.

[0116] It can be seen from the above examples that the preferred embodiment of the present application can prepare a multi-element doped copper-based nanowire electrocatalytic material, the material has a nano structure, and gaps are left between the nanowires, thereby increasing the specific surface area and pore volume of the copper-based catalytic material, which is beneficial to improving the activity of the catalyst when used for electrocatalytic CO2 reduction for preparing ethylene. In addition, the doped elements in the element doped copper-based nanowires exist in the inside and surface of the nanowires, which is beneficial to promoting the generation of ethylene products; the doped elements on the surface of the element doped copper-based nanowires are precipitated in a large amount in the reduction process, and the partial heteroatoms remaining in the subsurface or deeper layers have an influence on the adsorption and generation process of intermediates, so that part of Cu (Cu*) with positive valence is reserved on the surface of the catalyst, and the Cu* and Cu 0 adjacent to each other are beneficial to coupling between *CO intermediates to generate multi-carbon products, thereby improving the selectivity of ethylene in the electrocatalytic CO2 reduction reaction and the stability under a large current density.

[0117] The preferred embodiments of the present application are described in detail above with reference to the drawings, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including combining various specific technical features in any suitable manner, but these simple modifications and combinations should also be considered as disclosed content of the present application, and all belong to the protection scope of the present application.

Claims

1. A copper-based electrocatalytic material, characterized in that: The copper-based electrocatalytic material includes a plurality of element-doped copper-based nanowires; In the copper-based electrocatalytic material, the packing density of the plurality of copper-based nanowires doped with the element is 0.3-1 g / cm 3 ; The element-doped copper-based nanowires have a diameter of 20-200 nm, a length of 1-10 μm, and a specific surface area of ​​500-2000 m 2 / g, pore volume of 50-200cm 3 / g; The copper element in the element-doped copper-based nanowires is Cu 2+ 、Cu + 、Cu 0 One or more forms of The doping elements in the element-doped copper-based nanowires are selected from one or more of S, F, Br, N, and O.

2. The copper-based electrocatalytic material according to claim 1, wherein In the element-doped copper-based nanowires, the content of the doping element is 0.1-10 wt %.

3. A method for preparing the copper-based electrocatalytic material according to claim 1, characterized in that: The preparation method comprises: (1) mixing a solution containing a thiophenol ligand with a copper salt solution to obtain a suspension; (2) subjecting the suspension to ultrasonic, heating, stirring and aging treatments, and then to centrifugation, washing and drying to obtain a copper-based nanowire precursor; (3) calcining the copper-based nanowire precursor; (4) The calcined copper-based nanowire precursor is subjected to in-situ electrochemical activation treatment to obtain the copper-based electrocatalytic material.

4. The preparation method according to claim 3, wherein In step (1), the copper salt is selected from one or more of copper chloride, copper nitrate and copper sulfate.

5. The preparation method according to claim 3, wherein The molar concentration of the copper salt solution is 1-100 mmol / L.

6. The preparation method according to claim 5, wherein The molar concentration of the copper salt solution is 37.2-100 mmol / L.

7. The preparation method according to claim 3, wherein In step (1), the thiophenol ligand is selected from one or more of 4-bromothiophenol, 4-fluorothiophenol, 4-aminothiophenol and 4-hydroxythiophenol.

8. The preparation method according to claim 3, wherein The molar concentration of the solution containing the thiophenol ligand is 100-1000 mmol / L.

9. The preparation method according to claim 8, wherein The molar concentration of the solution containing the thiophenol ligand is 100-500 mmol / L.

10. The preparation method according to claim 3, wherein In step (1), the mixing volume ratio of the copper salt solution to the solution containing the thiophenol ligand is 0.2-5:

1.

11. The preparation method according to claim 3, wherein In step (2), the ultrasonic power is 50-500W, the ultrasonic time is 0.01-2h, the heating temperature is 60-100°C, the stirring rate is 100-1000rpm, the aging time is 0.01-12h, the centrifugal rate is 2000-10000rpm, the washing is performed by alternating washing with deionized water and ethanol, and the drying temperature is 50-100°C.

12. The preparation method according to claim 3, wherein In step (3), the calcination temperature is 400-1000°C, the calcination time is 1-5h, the heating rate is 0.5-10°C / min, and the calcination atmosphere is selected from one or more of air, nitrogen and hydrogen.

13. The preparation method according to claim 12, wherein The calcination temperature is 600-700° C., the calcination time is 2-4 hours, and the heating rate is 0.5-2° C. / min.

14. The preparation method according to claim 3, wherein In step (4), the electrochemical activation treatment method is selected from one or more of linear sweep voltammetry, cyclic voltammetry, constant current method and constant voltage method.

15. The preparation method according to claim 14, wherein The voltage range of the linear sweep voltammetry and cyclic voltammetry is -2.5 to 0 V, and the scan or cycle is 1-80 times; The current density of the constant current method is -10 to -1500 mA / cm 2 , reaction time is 0.05-3h; The voltage of the constant voltage method is -1.5 to -3.5 V, and the reaction time is 0.05-3 hours.

16. Use of the copper-based electrocatalytic material according to claim 1 or 2 in the electrocatalytic reduction of carbon dioxide to produce ethylene.

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