An octahedral Cu 2 O / CuO heterojunction catalyst, its preparation method and application

Abstract

The present invention discloses an octahedral Cu2O / CuO heterojunction catalyst, a preparation method thereof, and an application thereof, belonging to the technical fields of new energy materials and electrocatalytic technology, and solving the technical problem of low selectivity of ethylene products during the electrocatalytic reduction of carbon dioxide. When the disclosed octahedral Cu2O / CuO heterojunction catalyst is used for electrocatalytic carbon dioxide reduction, the Faraday efficiency of the carbon-containing product generated is 60.5%, wherein the highest Faraday efficiency of ethylene can reach 37.5%, and it has excellent electrocatalytic carbon dioxide effect; at the same time, a preparation method of the above-mentioned octahedral Cu2O / CuO heterojunction catalyst is disclosed. This method prepares a copper-based heterojunction catalyst through a simple co-precipitation method and an ozone oxidation method, making it have high catalytic activity and ethylene product selectivity in the electrocatalytic reduction of carbon dioxide; this preparation method is simple in operation and easy to implement, and the prepared octahedral Cu2O / CuO heterojunction catalyst has excellent carbon dioxide reduction performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials and electrocatalytic technologies, and particularly relates to an octahedral Cu 2 O / CuO heterojunction catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The excessive consumption of fossil energy has led to a continuous increase in the concentration of carbon dioxide in the atmosphere. The resulting "greenhouse effect" has led to global warming, which greatly harms the environment on which we depend for survival and has triggered in-depth discussions on social sustainable development and environmental impact consequences. Reducing the concentration of carbon dioxide in the atmosphere is the top priority of scientific research at this stage. In the process of reducing the carbon dioxide concentration, on the one hand, low-carbon or non-carbon energy is used to replace the use of fossil fuels to reduce carbon dioxide emissions; on the other hand, carbon dioxide in the air is captured, stored, and converted. The conversion of carbon dioxide into high-value-added chemicals and energy has attracted extensive attention, and the main measures include thermochemical, photochemical, biochemical, and electrocatalytic conversion, etc. In recent years, electrocatalytic carbon dioxide reduction (CO 2 RR) has developed rapidly, mainly for two reasons: 1) Using wind energy, solar energy, and nuclear energy as electrical energy to provide power for electrocatalytic CO 2 RR; 2) H 2 O in the reduction process provides protons for the reaction.

[0003] Electrocatalysts play a crucial role because they directly determine the types of target products obtained from the carbon dioxide reduction reaction, such as CO, HCOOH, and C 2 H 4 etc. Developing efficient electrocatalytic CO 2 RR catalysts to reduce the concentration of carbon dioxide in the atmosphere while generating value-added fuels and chemicals is of great significance. In the process of electrocatalytic reduction of carbon dioxide by copper-based catalysts, due to the unique electronic structure of Cu, it can tightly adsorb reaction intermediates * CO during the reduction of carbon dioxide, promoting C-C coupling to produce C 2+ products and has attracted extensive attention. Copper is the only single-metal material reported so far that can reduce carbon dioxide to C 2+ (hydrocarbons, alcohols, etc.) products. Due to its strong reduction ability, the Cu-based catalyst has poor selectivity. Therefore, there is an urgent need to explore effective strategies to improve the selectivity of copper-based catalysts for reducing carbon dioxide to high-value-added ethylene.

[0004] A heterojunction refers to an interfacial region formed by the contact of two materials with different Fermi levels, which has non-linear impedance characteristics (rectifying characteristics). Due to the different Fermi levels, carriers (electrons and holes) will migrate in the interfacial region, changing the electron distribution on the surface and interface of the material. Eventually, positive and negative charge regions and a built-in electric field pointing from the positive charge region to the negative charge region are generated at the interface, leading to the rectifying characteristics of the heterojunction. The heterojunction can not only construct a new energy band structure, but its built-in electric field can also promote the injection or transfer of photo-generated electron-hole pairs at the interface, improve the separation efficiency of carriers, extend the carrier lifetime, and thus improve the catalytic performance. The improvement of the electrocatalytic activity of these materials stems from the rectifying characteristics of their heterojunctions. In addition, the directional flow of carriers at the heterojunction interface can also change the electron distribution on the surface and interface of the material, affect the adsorption and desorption ability of the substrate, change the electron transfer behavior between the material and the substrate, and thus regulate the activity of redox reactions. Since the catalytic reaction of the catalyst mainly occurs on the surface of the catalyst, the activity of the catalyst changes with the structure. If the structure of the catalyst can be controlled by constructing a heterojunction, the adsorption and conversion of substrate molecules can be changed to control the activity of the catalyst, which is a very effective means to optimize the performance of the catalyst. Then, how to achieve the controllable preparation of catalysts with specific heterojunction structures has become an urgent technical problem to be solved currently. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide an octahedral Cu 2 2O / CuO heterojunction catalyst, its preparation method and application, to develop a controllable preparation technology for copper-based heterojunction catalysts and solve the technical problem of low selectivity of ethylene products during the electrocatalytic reduction of carbon dioxide. To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The present invention discloses a preparation method for an octahedral Cu 2 2O / CuO heterojunction catalyst, including the following steps:

[0007] S1: Add polyvinylpyrrolidone and metal copper salt into water to obtain a mixed solution;

[0008] S2: Under the condition of a water bath, add alkali powder and reducing agent to the mixed solution in sequence for reaction. After the reaction ends, obtain a precipitate; wash and dry the precipitate to obtain a cuprous oxide precursor;

[0009] S3: Perform plasma ozone treatment on the cuprous oxide precursor to obtain an octahedral Cu 2 2O / CuO heterojunction catalyst.

[0010] Further, in S1, the metal copper salt is copper chloride, copper nitrate or copper sulfate; the concentration of the metal copper salt in the mixed solution is 0.01~0.1 mmol / mL.

[0011] Further, in S1, the mass ratio of the metal copper salt to polyvinylpyrrolidone is (1:30)~(30:1).

[0012] Further, in S1, the molecular weight of the polyvinylpyrrolidone is 8000~360000.

[0013] Further, in S2, the mass ratio of the alkali powder to the reducing agent is (1:3)-(3:1); the alkali powder is sodium hydroxide, potassium hydroxide or calcium hydroxide; the reducing agent is ascorbic acid or sodium borohydride.

[0014] Further, in S2, the temperature for the reaction under the water bath condition is 50~80 °C, and the reaction time is 2~6 h.

[0015] Further, in S3, the time for the plasma ozone treatment is 1~5 h.

[0016] The present invention also discloses an octahedral Cu 2 O / CuO heterojunction catalyst prepared by the above preparation method.

[0017] The present invention also discloses the application of the above octahedral Cu 2 O / CuO heterojunction catalyst, and the octahedral Cu 2 O / CuO heterojunction catalyst is used in the electrocatalytic carbon dioxide reduction reaction.

[0018] Further, when the octahedral Cu 2 O / CuO heterojunction catalyst is used in the electrocatalytic carbon dioxide reduction reaction, the partial current density of the generated ethylene is 0.5 m~5.7 mA cm -2 .

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention discloses a preparation method of an octahedral Cu 2 O / CuO heterojunction catalyst. By using metal copper salt, polyvinylpyrrolidone, sodium hydroxide and ascorbic acid as raw materials, the controllable preparation of Cu 2 O materials with specific crystal planes can be realized; the present invention realizes the controllable preparation of Cu 2 O / CuO heterojunction structure catalysts by regulating the reduction of oxygen in the synthesis process through plasma ozone; the method has simple process and low production cost, and is suitable for industrial production.

[0021] The present invention also discloses the octahedral Cu prepared by the above method 2 O / CuO heterojunction catalyst, and the generated catalyst has high purity and good catalytic activity, and has broad application prospects.

[0022] The present invention also discloses the application of the above octahedral Cu 2 O / CuO heterojunction catalyst in electrocatalytic carbon dioxide reduction. Since the octahedral Cu 2 O / CuO heterojunction catalyst has high crystallinity and the crystal plane orientation is Cu 2 O(110) / CuO(002). The Faraday efficiency of the prepared octahedral Cu 2 O / CuO heterojunction material for electrocatalytic reduction of carbon dioxide to produce carbon-containing products is 60.5%. Among them, the partial current density of ethylene is 0.5 mA cm -2 ~5.7 mA cm -2 , and it has excellent electrocatalytic carbon dioxide catalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the X-ray diffraction pattern of the octahedral Cu 2 O / CuO heterojunction catalyst prepared in Example 1;

[0024] Figure 2 is the transmission electron microscope image and high-resolution transmission electron microscope image of the octahedral Cu 2 O / CuO heterojunction catalyst prepared in Example 1;

[0025] wherein: a - transmission electron microscope image; b - high-resolution transmission electron microscope image;

[0026] Figure 3 is the high-resolution fine spectrum of Cu 2p XPS of the octahedral Cu 2 O / CuO heterojunction catalyst prepared in Example 1;

[0027] Figure 4 is the Faraday efficiency diagram of the electrocatalytic carbon dioxide reduction products of the octahedral Cu 2 O / CuO heterojunction catalyst prepared in Example 1;

[0028] Figure 5 is the linear sweep voltammogram of the octahedral Cu 2 O / CuO heterojunction catalyst in an electrolyte saturated with nitrogen or carbon dioxide. DETAILED DESCRIPTION OF THE INVENTION

[0029] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meanings understood by those skilled in the art with respect to the present invention. In case of conflict, the definitions in this specification shall prevail.

[0030] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall in no way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0031] In this document, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0032] In this document, unless otherwise specified, the terms "comprise", "include", "contain", "have", or similar expressions cover the meanings of "consist of" and "consist essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0033] In this document, for the sake of brevity, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as being within the scope described in this specification.

[0034] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught in the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0035] Conventional instruments and equipment in the art are used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturers. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratios represent weight ratios.

[0036] Example 1

[0037] An octahedral Cu2 Preparation method of O / CuO heterojunction catalyst, comprising the following steps:

[0038] S1: Add 2 mmol of CuCl 2 ∙2H 2 O (0.341 g) and 6 g of polyvinylpyrrolidone (M.W., 8000) to 100 mL of water, and stir to obtain a mixed solution; the concentration of CuCl 2 ∙2H 2 O in the mixed solution is 0.02 mmol / mL;

[0039] S2: Place the above mixed solution in a water bath at 60 °C, add 1.6 g of sodium hydroxide under constant stirring conditions, stir until it turns dark brown, then add 2 g of ascorbic acid and react for 4 h, collect the precipitate by centrifugation, wash it 3 times with water and ethanol, and vacuum dry to obtain a cuprous oxide precursor;

[0040] S3: Perform plasma ozone treatment on the precipitate precursor for 3 h to obtain an octahedral Cu 2 O / CuO heterojunction catalyst.

[0041] The following method is used to conduct a reduction test on carbon dioxide.

[0042] Assembly of H-type electrolytic cell: Use the octahedral Cu 2 O / CuO heterojunction electrocatalyst as the working electrode, Ag / AgCl as the reference electrode, place it in the cathode cavity, and use a Pt sheet as the counter electrode on the anode side. Use a Nafion 117 membrane to separate the two electrolytes to ensure proton exchange and avoid contamination of the electrolyte. 0.5 M KOH saturated CO 2 aqueous solution is used as the electrolyte. All potentials are measured on the Ag / AgCl reference electrode (saturated KCl).

[0043] Electrochemical test: All electrochemical experiments are carried out using an electrochemical workstation (CHI660E) in a three-electrode H-type cell.

[0044] Figure 1 Shown is the X-ray diffraction pattern of the octahedral Cu 2 O / CuO heterojunction catalyst prepared in Example 1. It can be seen from the X-ray diffraction pattern of the product that the synthesized product is Cu 2 O / CuO, corresponding to the cubic Cu 2 O and monoclinic CuO structures, with space groups Pn3m, a = 4.217 Å; C2 / c, a = 4.6853 Å, b = 3.4257 Å, c = 5.1303 Å respectively.

[0045] Figure 2 The octahedral Cu prepared in Example 1 is shown 2 The transmission electron microscopy (TEM) image and high-resolution transmission electron microscopy (HRTEM) image of the O / CuO heterojunction catalyst. The TEM image shows that the Cu 2 O / CuO heterojunction catalyst is octahedral particles. The HRTEM image further shows that the interplanar spacing of the octahedral Cu 2 O / CuO heterojunction catalyst is 0.30 nm, and the corresponding crystal plane is Cu 2 O (110) crystal plane; the interplanar spacing is 0.255 nm, and the corresponding crystal plane is the CuO (002) crystal plane

[0046] Figure 3 The octahedral Cu prepared in Example 1 is shown 2 The high-resolution X-ray photoelectron spectroscopy (XPS) fine spectrum of Cu 2p of the O / CuO heterojunction catalyst prepared in Example 1. It can be seen from the total spectrum that the Cu 2p spectrum of the sample can be fitted into two pairs of corresponding peaks of Cu 1+ and Cu 2+ . The two peaks appearing at the electron binding energies of 936.6 eV and 952.4 eV can be attributed to Cu 2p 3 / 2 and Cu 2p 1 / 2 , which proves the existence of Cu 1+ in the sample. Two peaks of Cu 2p appear at the electron binding energies of 954.8 eV and 934.5 eV, which can be attributed to Cu 2p 3 / 2 and Cu 2p 1 / 2 , which proves the existence of Cu 2+ .

[0047] Figure 4 The octahedral Cu prepared in Example 1 is shown 2 The Faraday efficiency diagram of the electrocatalytic carbon dioxide reduction products of the O / CuO heterojunction catalyst. It can be seen from the graph that at -1.25 V vs. RHE voltage, the Faraday efficiency of electrocatalytic reduction of carbon dioxide to produce carbon-containing products is 60.5%, and among them, the Faraday efficiency of ethylene reaches 37.5%.

[0048] Figure 5 The octahedral Cu prepared in Example 1 is shown 2 The linear sweep voltammogram of the O / CuO heterojunction catalyst in an electrolyte saturated with nitrogen or carbon dioxide. It can be known from the linear sweep voltammogram that the octahedral Cu 2 O / CuO heterojunction catalyst shows a more positive onset potential and a significant increase in current density in the CO 2 -saturated electrolyte than in the corresponding N 2 -saturated electrolyte, indicating that it has a higher CO 2Electroreduction activity. At a voltage of -1.2 V vs. RHE, Cu 2 The partial current density of the Cu -2 O / CuO heterojunction for electrocatalytic reduction of carbon dioxide to ethylene reaches 5.7 mA cm

[0049] Example 2:

[0050] According to the method of Example 1, the difference is that the metal copper salt used in S1 is copper nitrate, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0051] Example 3:

[0052] According to the method of Example 1, the difference is that the metal copper salt used in S1 is copper sulfate, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0053] Example 4:

[0054] According to the method of Example 1, the difference is that the concentration of the metal copper salt in step S1 is 0.01 mmol / mL, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0055] Example 5:

[0056] According to the method of Example 1, the difference is that the concentration of the metal copper salt in S1 is 0.05 mmol / mL, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0057] Example 6:

[0058] According to the method of Example 1, the difference is that the concentration of the metal copper salt in S1 is 0.1 mmol / mL, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0059] Example 7:

[0060] According to the method of Example 1, the difference is that the molecular weight of the polyvinylpyrrolidone used in S1 is 40000, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0061] Example 8:

[0062] According to the method of Example 1, the difference is that the molecular weight of the polyvinylpyrrolidone used in S1 is 58,000, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0063] Example 9:

[0064] According to the method of Example 1, the difference is that the molecular weight of the polyvinylpyrrolidone used in S1 is 360,000, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0065] Example 10:

[0066] According to the method of Example 1, the difference is that the mass ratio of the metal copper salt to the polyvinylpyrrolidone in S1 is 0.033, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0067] Example 11:

[0068] According to the method of Example 1, the difference is that the mass ratio of the metal copper salt to the polyvinylpyrrolidone in S1 is 1, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0069] Example 12:

[0070] According to the method of Example 1, the difference is that the mass ratio of the metal copper salt to the polyvinylpyrrolidone in S1 is 5, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0071] Example 13:

[0072] According to the method of Example 1, the difference is that the mass ratio of the metal copper salt to the polyvinylpyrrolidone in S1 is 10, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0073] Example 14:

[0074] According to the method of Example 1, the difference is that the mass ratio of the metal copper salt to the polyvinylpyrrolidone in S1 is 15, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0075] Example 15:

[0076] According to the method of Example 1, the difference is that the mass ratio of metal copper salt to polyvinylpyrrolidone in S1 is 20, and the rest are the same as in Example 1, obtaining a Cu 2 O / CuO heterojunction catalyst.

[0077] Example 16:

[0078] According to the method of Example 1, the difference is that the mass ratio of metal copper salt to polyvinylpyrrolidone in S1 is 30, and the rest are the same as in Example 1, obtaining a Cu 2 O / CuO heterojunction catalyst.

[0079] Example 17:

[0080] According to the method of Example 1, the difference is that the alkali powder in S2 is potassium hydroxide, and the rest are the same as in Example 1, obtaining a Cu 2 O / CuO heterojunction catalyst.

[0081] Example 18:

[0082] According to the method of Example 1, the difference is that the alkali powder in S2 is calcium hydroxide, and the rest are the same as in Example 1, obtaining a Cu 2 O / CuO heterojunction catalyst.

[0083] Example 19:

[0084] According to the method of Example 1, the difference is that the reducing agent in S2 is sodium borohydride, and the rest are the same as in Example 1, obtaining a Cu 2 O / CuO heterojunction catalyst. Example 20:

[0085] According to the method of Example 1, the difference is that the mass ratio of alkali powder to reducing agent in S2 is 0.33, and the rest are the same as in Example 1, obtaining a Cu 2 O / CuO heterojunction catalyst.

[0086] Example 21:

[0087] According to the method of Example 1, the difference is that the mass ratio of alkali powder to reducing agent in S2 is 1, and the rest are the same as in Example 1, obtaining a Cu 2 O / CuO heterojunction catalyst.

[0088] Example 22:

[0089] According to the method of Example 1, the difference is that the mass ratio of alkali powder to reducing agent in S2 is 1.5, and the rest are the same as in Example 1, obtaining a Cu 2 O / CuO heterojunction catalyst.

[0090] Example 23:

[0091] According to the method of Example 1, the difference is that the mass ratio of the alkali powder to the reducing agent in S2 is 2, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0092] Example 24:

[0093] According to the method of Example 1, the difference is that the mass ratio of the alkali powder to the reducing agent in S2 is 3, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0094] Example 25:

[0095] According to the method of Example 1, the difference is that the water bath temperature in S2 is 50 °C, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0096] Example 26:

[0097] According to the method of Example 1, the difference is that the water bath temperature in S2 is 70 °C, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0098] Example 27:

[0099] According to the method of Example 1, the difference is that the water bath temperature in S2 is 80 °C, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0100] Example 28:

[0101] According to the method of Example 1, the difference is that the reaction time in S2 is 2 h, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0102] Example 29:

[0103] According to the method of Example 1, the difference is that the reaction time in S2 is 3 h, and the rest are the same as in Example 1, to obtain a Cu 2 O / CuO heterojunction catalyst.

[0104] Example 30:

[0105] According to the method of Example 1, the difference is that the reaction time in S2 is 5 h, and the rest are the same as in Example 1, to obtain a Cu2 O / CuO heterojunction catalyst.

[0106] Example 31:

[0107] According to the method of Example 1, the difference is that the reaction time in S2 is 6 h, and the rest are the same as in Example 1, obtaining a kind of Cu 2 O / CuO heterojunction catalyst.

[0108] Example 32:

[0109] According to the method of Example 1, the difference is that the time of plasma ozone treatment in S3 is 1 h, and the rest are the same as in Example 1, obtaining a kind of Cu 2 O / CuO heterojunction catalyst.

[0110] Example 33:

[0111] According to the method of Example 1, the difference is that the time of plasma ozone treatment in S3 is 2 h, and the rest are the same as in Example 1, obtaining a kind of Cu 2 O / CuO heterojunction catalyst.

[0112] Example 34:

[0113] According to the method of Example 1, the difference is that the time of plasma ozone treatment in S3 is 4 h, and the rest are the same as in Example 1, obtaining a kind of Cu 2 O / CuO heterojunction catalyst.

[0114] Example 35:

[0115] According to the method of Example 1, the difference is that the time of plasma ozone treatment in S3 is 5 h, and the rest are the same as in Example 1, obtaining a kind of Cu 2 O / CuO heterojunction catalyst.

[0116] The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for preparing an octahedral Cu 2 O / CuO heterojunction catalyst It is characterized in that It includes the following steps: S1: Add polyvinylpyrrolidone and metal copper salt into water to obtain a mixed solution; S2: Under the condition of water bath, add alkali powder and reducing agent into the mixed solution in sequence for reaction. After the reaction ends, obtain a precipitate; After washing and drying the precipitate, obtain a cuprous oxide precursor; S3: Subject the cuprous oxide precursor to plasma ozone treatment to obtain an octahedral Cu 2 O / CuO heterojunction catalyst; In S2, the mass ratio of the alkali powder to the reducing agent is (1:3)-(3:1); The alkali powder is sodium hydroxide, potassium hydroxide or calcium hydroxide; The reducing agent is ascorbic acid or sodium borohydride; The temperature for the reaction under the water bath condition is 50-80 °C, and the reaction time is 2-6 h In S3, the time for the plasma ozone treatment is 1-5 h.

2. The preparation method of an octahedral Cu 2 O / CuO heterojunction catalyst according to claim 1 It is characterized in that In S1, the metal copper salt is copper chloride, copper nitrate or copper sulfate; The concentration of the metal copper salt in the mixed solution is 0.01-0.1 mmol / mL.

3. A preparation method of an octahedral Cu 2 O / CuO heterojunction catalyst according to claim 1 It is characterized in that In S1, the mass ratio of the metal copper salt to polyvinylpyrrolidone is (1:30)-(30:1).

4. A preparation method of an octahedral Cu 2 O / CuO heterojunction catalyst according to claim 1 It is characterized in that In S1, the molecular weight of the polyvinylpyrrolidone is 8000-360000.

5. An octahedral Cu 2 O / CuO heterojunction catalyst, It is characterized in that Prepared by using the preparation method of an octahedral Cu 2 O / CuO heterojunction catalyst described in any one of claims 1 to 4.

6. Use of an octahedral Cu 2 O / CuO heterojunction catalyst according to claim 5, It is characterized in that The octahedral Cu 2 O / CuO heterojunction catalyst is used in the electrocatalytic carbon dioxide reduction reaction.

7. Use of an octahedral Cu 2 O / CuO heterojunction catalyst according to claim 6 It is characterized in that The octahedral Cu 2 O / CuO heterojunction catalyst for electrocatalytic carbon dioxide reduction reaction generates an ethylene partial current density of 0.5 m~5.7 mA cm -2 .

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