Metal-doped hollow-structure polycrystalline cuprous oxide as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysis, and particularly relates to metal-doped hollow-structure polycrystalline cuprous oxide as well as a preparation method and application thereof. The chemical component of the metal-doped hollow-structure polycrystalline cuprous oxide provided by the invention is polycrystalline cuprous oxide of which crystal lattices are doped with catalytic metal elements, and the metal-doped hollow-structure polycrystalline cuprous oxide has a hollow sphere structure; the atomic ratio of a copper element to a catalytic metal element in the metal-doped hollow-structure polycrystalline cuprous oxide is (20-100): 1. The metal-doped hollow-structure polycrystalline cuprous oxide has high structural stability and conductivity, inhibits hydrogen evolution reaction, and improves the selectivity and yield of CO generated by electrocatalytic carbon dioxide reduction reaction.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic technology, and particularly relates to a metal-doped hollow-structured polycrystalline cuprous oxide and its preparation method and application. Background Art

[0002] In the past few decades, the greenhouse effect and energy shortage have become the two most serious problems and challenges. Although carbon dioxide is the main greenhouse gas, leading to serious global climate change, it is also an easily accessible carbon energy source. Electrochemical carbon dioxide reduction reaction (CO2RR) is considered a promising method for reducing greenhouse gases and a future solution to solve the shortage of fuels and chemical raw materials.

[0003] Copper-based catalyst materials have good structures and are suitable for the carbon dioxide reduction reaction. They are the only catalysts that can convert carbon dioxide into high-value chemical products such as C1 and C2. Among copper-based catalysts, Cu2O, as a typical catalyst, has unique interfacial structures and dynamic reconstruction capabilities, abundant crystal planes and defect active sites, low cost and easily adjustable morphologies, as well as high theoretical selectivity potential, which has attracted extensive research. However, due to the problems of insufficient structural stability of Cu2O, serious competition from the hydrogen evolution reaction (HER), and poor conductivity, the selectivity and yield of the Cu2O catalyst for electrochemically reducing CO2 to CO are insufficient. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a metal-doped hollow-structured polycrystalline cuprous oxide and its preparation method and application. The metal-doped hollow-structured polycrystalline cuprous oxide has high structural stability and conductivity, inhibits the hydrogen evolution reaction, and improves the selectivity and yield of electrochemically reducing carbon dioxide to CO.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a metal-doped hollow-structured polycrystalline cuprous oxide, whose chemical composition is polycrystalline cuprous oxide with a catalytic metal element doped in the lattice, and has a hollow sphere structure;

[0007] The atomic ratio of copper element to catalytic metal element in the metal-doped hollow-structured polycrystalline cuprous oxide is 20 - 100:1.

[0008] Preferably, the catalytic metal element is a rare earth metal element and / or a transition metal element; the rare earth metal element is cerium; the transition metal element includes one or more of indium, zinc, and gallium.

[0009] Preferably, the inner diameter of the metal-doped hollow-structured polycrystalline cuprous oxide is 500 nm to 1.2 μm, and the outer diameter is 2.86 to 4.9 μm.

[0010] The present invention also provides a method for preparing the metal-doped hollow-structured polycrystalline cuprous oxide described in the above technical solution, including the following steps:

[0011] Mix a catalytic metal salt, a copper salt, and a reducing organic alcohol, and perform a solvothermal reaction on the obtained precursor solution to obtain the metal-doped hollow-structured polycrystalline cuprous oxide;

[0012] The molar ratio of copper ions in the copper salt to catalytic metal ions in the catalytic metal salt is 20 to 100:1.

[0013] Preferably, the reducing organic alcohol is ethylene glycol; the molar ratio of the amount of the copper salt to the volume of the reducing organic alcohol is (2 to 6) mmol: 40 mL.

[0014] Preferably, the temperature of the solvothermal reaction is 100 to 160 °C, and the heat preservation time is 8 to 12 h.

[0015] The present invention also provides the use of the metal-doped hollow-structured polycrystalline cuprous oxide described in the above technical solution or the metal-doped hollow-structured polycrystalline cuprous oxide prepared by the preparation method described in the above technical solution as a catalyst in the electrocatalytic carbon dioxide reduction reaction.

[0016] The present invention also provides a modified electrode, including a substrate electrode and a catalyst attached to the surface of the substrate electrode;

[0017] The catalyst is the metal-doped hollow-structured polycrystalline cuprous oxide described in the above technical solution or the metal-doped hollow-structured polycrystalline cuprous oxide prepared by the preparation method described in the above technical solution.

[0018] The present invention also provides a flow-through electrolytic cell, and the cathode working electrode is the modified electrode described in the above technical solution.

[0019] The present invention also provides a method for electrocatalytic carbon dioxide reduction reaction, including the following steps:

[0020] Introduce carbon dioxide on the cathode working electrode side of the flow-through electrolytic cell described in the above technical solution to perform an electrocatalytic carbon dioxide reduction reaction to generate a mixed gas, and the mixed gas includes carbon monoxide and hydrogen.

[0021] The present invention provides a metal-doped hollow-structured polycrystalline cuprous oxide, the chemical composition of which is polycrystalline cuprous oxide doped with a catalytic metal element in the crystal lattice, and has a hollow sphere structure; the atomic ratio of copper element to catalytic metal element in the metal-doped hollow-structured polycrystalline cuprous oxide is 20-100:1. The metal-doped hollow-structured polycrystalline cuprous oxide provided by the present invention incorporates a catalytic metal element into the crystal lattice of polycrystalline cuprous oxide, which can improve the structural stability and electrical conductivity. The metal-doped hollow-structured polycrystalline cuprous oxide exposes the (111) crystal plane, which is more easily activated to form *COOH, thereby generating the intermediate *CO, enhancing the adsorption and desorption of the intermediate *CO on the surface of the metal-doped hollow-structured polycrystalline cuprous oxide, reducing the desorption energy barrier of *CO, thereby improving the electrocatalytic carbon dioxide reduction reaction (CO2RR) performance, inhibiting the hydrogen evolution reaction (HER) competition, promoting the reduction of CO2 to CO, improving the catalytic activity and selectivity of electrocatalytic reduction of CO2 to CO, and increasing the CO yield. The test results of the examples show that the metal-doped hollow-structured polycrystalline cuprous oxide provided by the present invention has a partial current density of -29.2 mA·cm -2 at a low potential of -0.75 V vs. RHE (reversible hydrogen electrode), and simultaneously exhibits a CO selectivity of 80.31%. Compared with Cu2O, the CO production increases from 15.4 μmol / L to 595.7 μmol / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic process flow diagram for preparing the metal-doped hollow-structured polycrystalline cuprous oxide according to the embodiment of the present invention;

[0023] Figure 2 is the Cu of Example 1 60 In1, the Cu of Example 2 20 In1, the Cu of Example 5 100 In1, and the XRD patterns of Cu2O of Comparative Example 1;

[0024] Figure 3 is the Cu of Example 1 60 The XPS spectra of In1 of Example 1 and Cu2O (Pure-Cu2O) of Comparative Example 1;

[0025] Figure 4 is the Cu of Example 1 60 The SEM image of In1;

[0026] Figure 5 is the Cu of Example 1 60 The TEM hollow structure image of In1;

[0027] Figure 6 is the Cu of Example 1 60 The electrocatalytic reduction of carbon dioxide performance diagrams of In1 of Example 1 and Cu2O of Comparative Example 1;

[0028] Figure 7 Cu with different Cu and In element ratios x Performance comparison chart of In1 (x = 0, 20, 40, 60, 80, 100) catalysts;

[0029] Figure 8 Cu of Example 1 60 Stability test result chart of CuIn1 under constant potential;

[0030] Figure 9 Cu of Example 1 60 LSV curve comparison chart of CuIn1 of Example 1 and Cu2O of Comparative Example 1 in CO2-saturated electrolyte and argon-saturated electrolyte. Detailed implementation mode

[0031] The present invention provides a metal-doped hollow-structured polycrystalline cuprous oxide, the chemical composition of which is polycrystalline cuprous oxide doped with a catalytic metal element in the lattice, and has a hollow sphere structure;

[0032] In the metal-doped hollow-structured polycrystalline cuprous oxide, the atomic ratio of copper element to catalytic metal element is 20-100:1.

[0033] Unless otherwise specified, the present invention has no special requirements for the sources of the raw materials used, and commercially available products well-known to those skilled in the art can be used.

[0034] As an implementation mode, the catalytic metal element is a rare earth metal element and / or a transition metal element, and is a transition metal element in specific embodiments; the rare earth metal element is cerium (Ce); the transition metal element includes one or more of indium (In), zinc (Zn) and gallium (Ga), and is indium (In) in specific embodiments.

[0035] As an implementation mode, the inner diameter of the metal-doped hollow-structured polycrystalline cuprous oxide is 500 nm - 1.2 μm, 500 nm - 1 μm in specific embodiments, the outer diameter is 2.86 - 4.9 μm, and 3.88 μm in specific embodiments.

[0036] As an implementation mode, the atomic ratio of copper element to catalytic metal element in the metal-doped hollow-structured polycrystalline cuprous oxide is 20-100:1, and is 20:1, 40:1, 60:1, 80:1 or 100:1 in specific embodiments.

[0037] After doping catalytic metal elements into the cuprous oxide lattice, the present invention can improve the structural stability and electrical conductivity. The metal-doped hollow-structured polycrystalline cuprous oxide exposes the (111) crystal plane, which is more easily activated to form *COOH, thereby generating the intermediate *CO, enhancing the adsorption and desorption of the intermediate *CO on the surface of the metal-doped hollow-structured polycrystalline cuprous oxide, reducing the desorption energy barrier of *CO, thus improving the electrocatalytic carbon dioxide reduction reaction (CO2RR) performance, inhibiting the competition of the hydrogen evolution reaction (HER), promoting the reduction of CO2 to CO, improving the catalytic activity and selectivity for electrocatalytic reduction of CO2 to CO, and increasing the CO yield.

[0038] By regulating the doping amount of the doped catalytic metal element, the present invention prepares metal-doped hollow-structured polycrystalline cuprous oxide with different electrocatalytic reduction performances of CO2 to CO. It is found through testing that when the atomic ratio of Cu and In elements is 60:1, it has the best electrocatalytic reduction performance of CO2 to CO.

[0039] The present invention also provides a preparation method of the metal-doped hollow-structured polycrystalline cuprous oxide described in the above technical solution, including the following steps:

[0040] Mix a catalytic metal salt, a copper salt, and a reducing organic alcohol, and perform a solvothermal reaction on the obtained precursor solution to obtain the metal-doped hollow-structured polycrystalline cuprous oxide.

[0041] As an implementation manner, the catalytic metal salt includes a rare earth metal salt and / or a transition metal salt, which is a transition metal salt in a specific embodiment; the rare earth metal salt is a cerium salt; the cerium salt is one or more of cerium chloride, cerium nitrate, and cerium sulfate, which is cerium chloride in a specific embodiment; the transition metal salt includes one or more of indium salt, zinc salt, and gallium salt, which is indium salt in a specific embodiment; the indium salt is one or more of indium chloride, indium nitrate, and indium sulfate, which is indium chloride in a specific embodiment; the zinc salt is one or more of zinc chloride, zinc nitrate, and zinc sulfate, which is zinc chloride in a specific embodiment; the gallium salt is one or more of gallium chloride, gallium nitrate, and gallium sulfate, which is gallium chloride in a specific embodiment.

[0042] As an implementation manner, the copper salt is one or more of copper nitrate, copper chloride, and copper sulfate, which is copper nitrate in a specific embodiment.

[0043] As an implementation manner, the molar ratio of copper ions in the copper salt to catalytic metal ions in the catalytic metal salt is 20 - 100:1, which is 20:1, 40:1, 60:1, 80:1, or 100:1 in specific embodiments.

[0044] As an implementation manner, the reducing organic alcohol is ethylene glycol; the molar amount of the copper salt and the volume of the reducing organic alcohol are in a ratio of (2-6) mmol: 40 mL, specifically (4-5) mmol: 40 mL in specific embodiments.

[0045] As an implementation manner, the catalytic metal salt, the copper salt and the reducing organic alcohol are mixed as follows: the copper salt and the catalytic metal salt are sequentially added to the reducing organic alcohol and stirred until dissolved; the stirring rate is 1000-1500 rpm, specifically 1200-1400 rpm in specific embodiments; the stirring time is 5-15 min, specifically 10 min in specific embodiments.

[0046] As an implementation manner, the temperature of the solvothermal reaction is 100-160 °C, specifically 120-150 °C in specific embodiments, and the heat preservation time is 8-12 h, specifically 9-11 h in specific embodiments; the heating rate to the solvothermal reaction is 1-5 °C / min, specifically 2-4 °C / min in specific embodiments; the equipment used for the solvothermal reaction is a reaction kettle; the inner liner material of the reaction kettle is polytetrafluoroethylene and the outer shell material is stainless steel; the volume of the solvothermal reaction precursor solution is 60-80% of the volume of the reaction kettle, specifically 80% in specific embodiments.

[0047] Figure 1 This is a schematic flow chart of the method for preparing metal-doped hollow-structured polycrystalline cuprous oxide in the embodiments of the present invention. As Figure 1 shown, copper nitrate and indium chloride are added to ethylene glycol in the present invention, and metal-doped hollow-structured polycrystalline cuprous oxide (Cu x In1) is generated by the solvothermal method.

[0048] During the solvothermal reaction process, the organic alcohol (ethylene glycol) acts as a reducing agent to reduce the copper salt (divalent copper) to Cu2O (monovalent copper); the pure Cu2O material is a solid spherical structure, and the catalytic metal element enters the lattice of Cu2O, promoting the aggregation of the polycrystalline particles of Cu2O, and finally forming metal-doped hollow-structured polycrystalline cuprous oxide with a hollow large sphere structure.

[0049] As an implementation manner, after the solvothermal reaction, it further includes: separating the solid-liquid of the product obtained from the solvothermal reaction, and the obtained solid is washed and dried in sequence; the washing is carried out with ethanol and deionized water in sequence; the number of times of ethanol washing and deionized water washing is independently 2-5 times, specifically 3-4 times in specific embodiments; the drying temperature is 60-100 °C, specifically 70-80 °C in specific embodiments; the drying time is 8-10 h, specifically 9-10 h in specific embodiments; the drying is vacuum drying; the vacuum degree of the vacuum drying is -0.08 to -0.1 MPa, specifically -0.08 to -0.09 MPa in specific embodiments.

[0050] The present invention also provides an application of the metal-doped hollow-structured polycrystalline cuprous oxide described in the above technical solution or the metal-doped hollow-structured polycrystalline cuprous oxide prepared by the preparation method described in the above technical solution as a catalyst in the electrocatalytic carbon dioxide reduction reaction.

[0051] The present invention also provides a modified electrode, including a substrate electrode and a catalyst attached to the surface of the substrate electrode, and the catalyst is the metal-doped hollow-structured polycrystalline cuprous oxide described in the above technical solution or the metal-doped hollow-structured polycrystalline cuprous oxide prepared by the preparation method described in the above technical solution.

[0052] As an embodiment, the substrate electrode is a carbon material; the carbon material is carbon paper; the loading amount of the catalyst on the surface of the substrate electrode is 0.5 - 1.5 mg·cm -2 , and in a specific embodiment, it is 1 mg·cm -2 .

[0053] As an embodiment, the preparation method of the modified electrode is: mixing the catalyst, an organic alcohol solvent, and a perfluorosulfonic acid polymer solution (Nafion solution), coating the obtained dispersion on the surface of the substrate and then drying to obtain the modified electrode; the organic alcohol solvent is isopropyl alcohol; the mixing is: mixing the catalyst and the organic alcohol solvent for the first ultrasonic treatment, and then adding the perfluorosulfonic acid polymer solution for the second ultrasonic treatment to obtain a dispersion; the mass ratio of the catalyst to the volume of the organic alcohol solvent is (5 - 20) mg:5 mL, and in a specific embodiment, it is (10 - 15) mg:5 mL; the mass ratio of the catalyst to the volume of the perfluorosulfonic acid polymer solution is 10 mg:(5 - 20) μL, and in a specific embodiment, it is 10 mg:10 μL; the power of the first ultrasonic treatment and the second ultrasonic treatment is independently 50 - 200 W, and in a specific embodiment, it is 150 W, and the time is independently 10 - 20 min, and in a specific embodiment, it is 10 - 15 min; the coating is spraying; the drying is drying under an infrared lamp; the drying time is 5 - 20 min, and in a specific embodiment, it is 10 - 15 min.

[0054] The present invention also provides a flow-through electrolytic cell, and the cathode working electrode is the modified electrode described in the above technical solution.

[0055] As an embodiment, the flow-through electrolytic cell is a three-electrode system, the counter electrode of the flow-through electrolytic cell is a titanium felt coated with iridium tantalum, and the reference electrode is an Ag / AgCl electrode. The present invention has no special limitation on the size of the cathode working electrode, and the size well-known in the art can be adopted. In the embodiments of the present invention, the size of the cathode working electrode is 1 cm × 1 cm.

[0056] As an embodiment, the flow-through electrolytic cell further includes a proton exchange membrane disposed between the cathode working electrode and the anode counter electrode; the proton exchange membrane is N115 proton exchange membrane; the pore between the cathode working electrode and the proton exchange membrane in the flow-through electrolytic cell serves as the cathode chamber, and the pore between the anode counter electrode and the proton exchange membrane serves as the anode chamber; the cathode chamber is filled with a cathode electrolyte; the anode chamber is filled with an anode electrolyte; the cathode electrolyte is a potassium bicarbonate solution; the concentration of the potassium bicarbonate solution is 0.1 to 1 mol / L, and in a specific embodiment, it is 1 mol / L; the anode electrolyte is a potassium sulfate solution; the concentration of the potassium sulfate solution is 0.1 to 1 mol / L, and in a specific embodiment, it is 1 mol / L; the pore between the cell body of the flow-through electrolytic cell and the cathode working electrode serves as the cathode gas chamber (the side of the cathode chamber away from the anode chamber), and carbon dioxide is introduced from the cathode gas chamber.

[0057] As an embodiment, the flow-through electrolytic cell further includes a cathode electrolytic bottle, an anode electrolytic bottle, a gas-liquid mixing pump, and a peristaltic pump. The anode electrolytic bottle and the cathode electrolytic bottle are respectively connected to the anode chamber and the cathode chamber through different circulation pipelines. The anode electrolyte and the cathode electrolyte are continuously circulated between the anode electrolytic bottle - anode chamber and the cathode electrolytic bottle - cathode chamber through the gas-liquid mixing pump and the peristaltic pump. The side of the cathode chamber away from the anode chamber is connected to a CO2 bottle through a third pipeline, and CO2 gas is continuously introduced into the flow-through electrolytic cell. The cathode gas outlet is linked to an on-line gas chromatograph for real-time product analysis.

[0058] The present invention also provides a method for electrocatalytic carbon dioxide reduction reaction, including the following steps:

[0059] Carbon dioxide is introduced on the cathode working electrode side of the flow-through electrolytic cell described in the above technical solution to carry out an electrocatalytic carbon dioxide reduction reaction to generate a mixed gas, and the mixed gas includes carbon monoxide and hydrogen;

[0060] The cathode working electrode is the electrode described in the above technical solution.

[0061] As an embodiment, the potential of the electrocatalytic carbon dioxide reduction reaction is -0.55 to -1.35 V vs. RHE, and in a specific embodiment, it is -0.75 V vs. RHE, and the current density is -4 to -66 mA·cm -2 , and in a specific embodiment, it is -10 to -29.2 mA·cm -2 , the time is 30 to 60 min, and in a specific embodiment, it is 30 to 40 min; the introduction amount of carbon dioxide is 10 to 30 mL / min, and in a specific embodiment, it is 20 mL / min.

[0062] As an embodiment, the yield of CO is 220.2 to 595.7 μmol·h-1 , specifically 595.7 μmol·h in the specific embodiment -1 ; the selectivity of CO is 63.10 - 80.31%, specifically 76.23 - 80.31% in the specific embodiment.

[0063] As an implementation manner, the yield of H2 is 42.8 - 56.05 μmol·h -1 , specifically 56.05 μmol·h in the specific embodiment -1 ; the selectivity of H2 is 5.73 - 12.14%, specifically 5.73 - 7.48% in the specific embodiment.

[0064] Next, the technical solutions in the present invention will be clearly and completely described in combination with the embodiments in the present invention, but they cannot be understood as limiting the protection scope of the present invention.

[0065] Example 1

[0066] Cu 60 Synthesis of CuIn1: By putting 4 mmol (0.9664 g) of Cu(NO3)2·3H2O and 0.0667 mmol (19.6 mg) of InCl3·3H2O, with the molar ratio of copper salt to indium salt being 60:1, and successively putting them into 40 mL of ethylene glycol, then stirring at 1200 rpm for 10 min to fully dissolve the added drugs. Then transfer 40 mL of the mixed solution of copper salt and indium salt to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave, heat it up at 2 °C / min, and keep the solvothermal reaction at 413 K (140 °C) for 10 h. After the reaction ends and it reaches room temperature, filter by suction, wash the obtained product 3 times each with ethanol and deionized water, and then dry it under vacuum at 80 °C and -0.08 MPa for 10 h to obtain an In-doped hollow structure polycrystalline cuprous oxide material, named Cu 60 In1.

[0067] Example 2

[0068] The difference from Example 1 is that the raw materials used are 4 mmol (0.9664 g) of Cu(NO3)2·3H2O and 0.2 mmol (58.6 mg) of InCl3·3H2O, with the molar ratio of copper salt to indium salt being 20:1, and the rest is the same as in Example 1. The obtained product is named Cu 20 In1.

[0069] Example 3

[0070] The difference from Example 1 is that the raw materials used are 4 mmol (0.9664 g) of Cu(NO3)2·3H2O and 0.1 mmol (29.3 mg) of InCl3·3H2O, and the molar ratio of the copper salt to the indium salt input is 40:1. The rest is the same as in Example 1, and the obtained product is named Cu 40 In1.

[0071] Example 4

[0072] The difference from Example 1 is that the raw materials used are 4 mmol (0.9664 g) of Cu(NO3)2·3H2O and 0.05 mmol (14.6 mg) of InCl3·3H2O, and the molar ratio of the copper salt to the indium salt input is 80:1. The rest is the same as in Example 1, and the obtained product is named Cu 80 In1.

[0073] Example 5

[0074] The difference from Example 1 is that the raw materials used are 4 mmol (0.9664 g) of Cu(NO3)2·3H2O and 0.04 mmol (11.7 mg) of InCl3·3H2O, and the molar ratio of the copper salt to the indium salt input is 100:1. The rest is the same as in Example 1, and the obtained product is named Cu 100 In1.

[0075] Comparative Example 1

[0076] The difference from Example 1 is that no indium salt is added, and only 4 mmol (0.9664 g) of Cu(NO3)2·3H2O is added. The rest is the same as in Example 1, and the obtained product is named Pure-Cu2O.

[0077] Application Example 1

[0078] Preparation of the working electrode (cathode working electrode) of the flow cell: Mix 10 mg of Cu 60 In1 prepared in Example 1 with 5 mL of isopropanol and sonicate for 15 min at 150 W. After waiting for the sonication to be uniform, add 10 μL of perfluorosulfonic acid-based polymer solution (Nafion solution) and sonicate again for 10 min at 150 W until a uniform dispersion is obtained. Subsequently, spray the dispersion evenly on the carbon paper through a spray gun, and the Cu 60 In1 loading is 1 mg·cm -2 , and finally place the carbon paper under an infrared lamp for drying treatment for 10 min and wait for use;

[0079] Steps of electrocatalytic reduction of CO2: The electrocatalytic reduction of CO2 reaction is carried out using a flow-through electrolytic cell, which is a three-electrode system. The counter electrode of the anode is a commercially purchased titanium felt coated with iridium tantalum, the reference electrode is an Ag / AgCl electrode, and the working electrode of the cathode is the above-mentioned flow cell working electrode (1 cm × 1 cm). The proton exchange membrane N115 is placed between the working electrode of the cathode and the counter electrode of the anode. The pore between the working electrode of the cathode and the proton exchange membrane is used as the cathode chamber, and the pore between the counter electrode of the anode and the proton exchange membrane is used as the anode chamber. The cathode chamber is filled with a cathode electrolyte (1 mol / L potassium bicarbonate solution); the anode chamber is filled with an anode electrolyte (1 mol / L potassium sulfate solution). The anode electrolytic cell and the cathode electrolytic cell are respectively connected to the anode chamber and the cathode chamber through different circulation pipelines. The anode electrolyte and the cathode electrolyte are continuously circulated between the anode electrolytic cell - anode chamber and the cathode electrolytic cell - cathode chamber by a gas-liquid mixing pump and a peristaltic pump. The pore between the cell body of the flow-through electrolytic cell and the working electrode of the cathode serves as the cathode gas chamber (on the side of the cathode chamber far from the anode chamber) and is connected to a CO2 bottle through a third pipeline. CO2 gas is continuously introduced into the flow-through electrolytic cell at a rate of 20 mL / min. The potential is -0.75 V vs. RHE, and the current density is -29.2 mA·cm -2 , the reaction time is 30 min, the cathode gas outlet is connected to an on-line gas chromatograph for real-time product analysis. The CO yield is 595.7 μmol·h -1 , the selectivity is 80.31%, and the H2 yield is 56.05 μmol·h -1 , and the selectivity is 7.48%.

[0080] Application Example 2

[0081] The difference from Application Example 1 is that Cu 60 In1 prepared in Example 1 is replaced by Cu 20 In1 prepared in Example 2, and the rest is the same as Application Example 1.

[0082] Application Example 3

[0083] The difference from Application Example 1 is that Cu 60 In1 prepared in Example 1 is replaced by Cu 40 In1 prepared in Example 3, and the rest is the same as Application Example 1.

[0084] Application Example 4

[0085] The difference from Application Example 1 is that Cu 60 In1 prepared in Example 1 is replaced by Cu 80 In1 prepared in Example 4, and the rest is the same as Application Example 1.

[0086] Application Example 5

[0087] The difference from Application Example 1 is that the Cu 60 In1 prepared in Example 1 is replaced with the Cu 100 In1 prepared in Example 5, and the rest is the same as Application Example 1.

[0088] Comparative Application Example 1

[0089] The difference from Application Example 1 is that the Cu 60 In1 prepared in Example 1 is replaced with the Cu2O prepared in Comparative Example 1, and the rest is the same as Application Example 1.

[0090] Performance Test

[0091] (1) Figure 2 For the XRD patterns of the Cu 60 In1 of Example 1, the Cu 20 In1 of Example 2, the Cu 100 In1 of Example 5, and the Cu2O of Comparative Example 1, the X-ray diffraction method was used to study the crystal structures of Pure-Cu2O and Cu x In1 (taking x = 20, 60, 100 as examples). The test process was as follows: Using a Cu-Kα radiation ray source, scanning was carried out in the range of 10 to 80°, and the speed was controlled at 5°`min -1 .

[0092] From Figure 2 the XRD patterns in, the peaks at 29°, 36°, 42°, 61°, 73° and 77° correspond to the (110), (111), (200), (220), (311) and (222) crystal planes of Cu2O. The results show that there is no obvious difference in the crystal structure of Cu2O before and after doping with In element, and both are in agreement with the information of the Cu2O (PDF#05-0667) standard card.

[0093] (2) Figure 3 For the XPS spectra of the Cu 60 In1 of Example 1 and the Cu2O (Pure-Cu2O) of Comparative Example 1, where a is the total XPS spectrum, b is the Cu 2p spectrum, c is the In 3d spectrum, and d is the O1s spectrum. The test process was as follows: Using a K-Alpha type X-ray photoelectron spectrometer from Thermo fisher Scientific Company in the United States for test analysis. When processing the test results, the C1s binding energy of 284.8 eV was selected as the calibration standard to adjust the data.

[0094] In the present invention, X-ray photoelectron spectroscopy (XPS) is used to study the chemical composition and valence states of Cu2O and Cu 60 In1. As Figure 3As shown in a, Cu, In, and O are clearly visible, which is consistent with the results of the EDS spectrum. The binding energies of In 3d, Cu 2p, and O 1s are referenced to the C 1s peak at 284.8 eV. Pure-Cu2O consists of Cu 2p and O 1s, while In-doped Cu2O consists of In 3d, Cu 2p, and O 1s, confirming that the In element has been successfully doped into Cu2O. According to Figure 3 As shown in b, the characteristic peaks of the Cu 2p spectrum of Pure-Cu2O are located at 932.5 eV and 952.5 eV, and the Cu 60 Cu 2p of In1 is located at 932.75 eV and 952.55 eV, which are attributed to Cu + Cu2p1 / 2 and Cu 2p3 / 2, respectively. The other two relatively weak peaks (935.15 eV and 955 eV) and the corresponding satellite peaks are from Cu 2+ .

[0095] Generally speaking, the main components and valence states of the Cu 60 In1 and Cu2O samples are both Cu + , and the presence of trace Cu 2+ may be due to the exposure of Cu2O to air. In Figure 3 As shown in d, the O 1s spectrum of Cu2O can be fitted to two peaks located at 531.95 eV and 530.55 eV. The O 1s spectrum of Cu 60 In1 is located at 531.8 eV and 530.65 eV, which are related to adsorbed oxygen (Oads) and lattice oxygen species (Olatt). An obvious change in the band energy was observed in the O 1s spectrum of the Cu 60 In1 catalyst, and it was found that the binding energy shifted negatively by 0.15 eV, which is due to In doping resulting in the generation of oxygen vacancies (Ov). As Figure 3 shown in the In 3d spectrum in c, the peaks of In 3d3 / 2 and In 3d 5 / 2 of the In element are at 445.1 eV and 452.65 eV, respectively, indicating that the In element has been doped into Cu2O.

[0096] (3) Figure 4 SEM images of Cu 60 In1 of Example 1 are shown. Among them, a is 10 μm, and the inset is the particle size distribution diagram. b is 3 μm, and c is 500 nm. The test conditions of the SEM technique are as follows: the acceleration voltage is 10 kV, and the scanning emission current is 10 μA. Preparation of the test sample: Weigh a small amount of Cu 60 In1 powder and add it to a test tube. Then add a small amount of ethanol for ultrasonic dispersion. Next, pipette a small amount of the completely dispersed solution and drop-coat it on a pre-prepared silicon wafer, and dry it with an infrared lamp. Finally, paste it on the electron microscope sample stage with conductive glue and wait for testing.

[0097] From Figure 4 a - c, it can be seen that: Cu 60 After the doping modification of In element in In1, its surface is composed of many nanoparticles and presents a spherical shape with a larger particle size. The overall particle size is about 3.8 ± 1.02 μm.

[0098] (4) Figure 5 The TEM hollow structure diagram of Cu 60 In1 of Example 1, where a is 1 μm and b is 500 nm. The TEM test was carried out using a FEI Tecnai F20 high - resolution transmission electron microscope produced by FEI Company, USA for the microstructure and lattice fringe characterization of Cu 60 In1.

[0099] From Figure 5 a - b, it can be seen that there are some Cu 60 In1 samples showing cracks. By observing this, it can be proved that the Cu 60 In1 samples exhibit a hollow spherical and layered - wrapped structure. After doping with In element, the Cu 60 In1 samples presenting this structure may provide rich active sites for CO2RR and be beneficial to improving the catalytic activity.

[0100] (5) Figure 6 The electro - catalytic reduction of carbon dioxide performance diagram of Cu 60 In1 of Example 1 and Cu2O of Comparative Example 1, where a is the Faraday efficiency for CO products, H2 and the yields of CO and H2 products, b is the Faraday efficiency of CO at different potentials, and c is the CO formation current density.

[0101] From Figure 6 a, it can be seen that in undoped In Cu2O, under the same conditions (-0.75 V vs. RHE, 1 mol·L -1 KHCO3 solution), its CO2RR performance is poor, with only 3.7% of CO products. While Cu 60 In1 shows excellent CO2 reduction performance, with its FE (Faraday efficiency) of CO reaching 80.3%, a 10 - fold difference compared with Cu2O, and the selectivity of H2 being only 3.96%. This indicates that doped In Cu2O shows priority for CO2RR and significantly inhibits the occurrence of HER.

[0102] From Figure 6 b, it can be seen that Cu 60The selectivity of CO products is far better than that of Cu2O at different potentials and shows a volcano-shaped distribution in a relatively wide potential range. When the bias voltage reaches -0.75V, its selectivity performance for CO products is the best.

[0103] Figure 6 Figure c presents the formation current of CO products for the two catalysts. In a relatively wide potential range, Cu 60 In1 has a higher CO formation current density than pure Cu2O. At the optimal potential of -0.75V, Cu 60 The partial current density of CO for In1 can reach -29.2 mA·cm -2 , which is much greater than the partial current density of CO for Cu2O before doping. The production of CO increases from 15.4 μmol / L to 595.7 μmol / L.

[0104] (6) Figure 7 Figure for the performance comparison of Cu x In1 (x = 0, 20, 40, 60, 80, 100) catalysts with different Cu and In element ratios. Considering that the doping amount of In in the catalyst may affect its carbon dioxide reduction performance, a series of Cu x In1 (x = 0, 20, 40, 60, 80, 100) catalysts with different In contents were prepared and tested for carbon dioxide reduction performance. The Faraday efficiency of all samples was tested in the potential range of -0.35 - 1.35V vs. RHE.

[0105] As Figure 7 shown in a - f, the changes in the Faraday efficiency of CO and H2 products produced by Pure-Cu2O and Cu x In1 catalysts under a certain range of bias voltages are listed respectively. It can be found that when the doping ratio of In to Cu atoms is 60, it shows a significant HER inhibition effect in a CO2 atmosphere. Its FE(CO) increases from 8.32% to 80.31%, while FE(H2) decreases from 60.20% to 7.48%. The results show that although CO2RR and HER are competitive reactions during electrolysis, by doping an appropriate amount of In into pure Cu2O, it affects the selectivity of Cu x In1 catalyst for CO2RR and significantly improves its CO2RR performance.

[0106] (7) Figure 8 Figure for the stability test results of Cu 60 In1 in Example 1 under constant potential.

[0107] As Figure 8 shown, after doping In, Cu 60Long-term potentiostatic electrolysis at -0.75 V vs. RHE showed that the FE of CO could be maintained at about 80% within 5 h, and the current density did not show significant decay.

[0108] (8) Figure 9 Cu of Example 1 60 Comparison diagram of LSV curves of In1 and Cu2O of Comparative Example 1 in CO2-saturated electrolyte and argon-saturated electrolyte.

[0109] As Figure 9 shown, the LSV curves of the two catalysts before and after doping with In element in CO2-saturated electrolyte and Ar-saturated electrolyte were compared. The results showed that the current density in CO2 was significantly higher than that in argon, indicating that the Cu 60 In1 catalyst has higher activity for CO2RR.

[0110] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A metal-doped hollow structure polycrystalline cuprous oxide, characterized in that: The chemical composition is polycrystalline cuprous oxide doped with catalytic metal elements in the crystal lattice, with a hollow sphere structure; The atomic ratio of copper element to catalytic metal element in the metal-doped hollow structure polycrystalline cuprous oxide is 20-100:

1.

2. The metal-doped hollow structure polycrystalline cuprous oxide according to claim 1, characterized in that: The catalytic metal element is a rare earth metal element and / or a transition metal element; the rare earth metal element is cerium; and the transition metal element includes one or more of indium, zinc and gallium.

3. The metal-doped hollow structure polycrystalline cuprous oxide according to claim 1, characterized in that: The metal-doped hollow structure polycrystalline cuprous oxide has an inner diameter of 500nm to 1.2μm and an outer diameter of 2.86 to 4.9μm.

4. The method for preparing the metal-doped hollow structure polycrystalline cuprous oxide according to any one of claims 1 to 3, characterized in that: The following steps are involved: The catalytic metal salt, the copper salt and the reducing organic alcohol are mixed, and the obtained precursor solution is subjected to a solvothermal reaction to obtain the metal-doped hollow structure polycrystalline cuprous oxide; The molar ratio of the copper ions in the copper salt to the catalytic metal ions in the catalytic metal salt is 20 to 100:

1.

5. The preparation method according to claim 4, characterized in that: The reducing organic alcohol is ethylene glycol; the ratio of the amount of the copper salt to the volume of the reducing organic alcohol is (2-6) mmol:40 mL.

6. The preparation method according to claim 4, characterized in that: The temperature of the solvent thermal reaction is 100-160° C., and the insulation time is 8-12 hours.

7. Use of the metal-doped hollow-structure polycrystalline cuprous oxide according to any one of claims 1 to 3 or the metal-doped hollow-structure polycrystalline cuprous oxide prepared by the preparation method according to any one of claims 4 to 6 as a catalyst in an electrocatalytic carbon dioxide reduction reaction.

8. A modified electrode, characterized in that: It includes a substrate electrode and a catalyst attached to the surface of the substrate electrode; The catalyst is the metal-doped hollow structure polycrystalline cuprous oxide as described in any one of claims 1 to 3 or the metal-doped hollow structure polycrystalline cuprous oxide prepared by the preparation method as described in any one of claims 4 to 6.

9. A flow-type electrolytic cell, characterized in that: The cathode working electrode is the modified electrode according to claim 8.

10. A method for electrocatalytic carbon dioxide reduction reaction, characterized in that: The following steps are involved: Carbon dioxide is introduced into the cathode working electrode side of the flow-type electrolytic cell as claimed in claim 9 to carry out an electrocatalytic carbon dioxide reduction reaction to generate a mixed gas comprising carbon monoxide and hydrogen.

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