阅读说明：本技术 铜基复合纳米材料及其制备方法和应用 (Copper-based composite nano material and preparation method and application thereof ) 是由 杨世和 龙霞 蔡荣明 于 2021-08-31 设计创作，主要内容包括：本发明公开了一种铜基复合纳米材料及其制备方法和应用,该铜基复合纳米材料包括卤素修饰的二维纳米铜氧化物和分散在二维铜氧化物上的铜纳米片,铜纳米片具有高能晶面。根据本申请实施例的铜基复合纳米材料,至少具有如下有益效果：本申请所提供的铜基复合纳米材料中卤素的修饰不仅有助于金属暴露晶面的改性,而且有助于在二维纳米铜氧化物上形成具有高能晶面的纳米片,从而使得最终形成的材料具有丰富活性位点,具有在低电位下产乙酸的高度选择性以及各电位下抑制产氢及提高二氧化碳还原的法拉第效率的效果。(The invention discloses a copper-based composite nano material and a preparation method and application thereof. The copper-based composite nanomaterial according to the embodiment of the application has at least the following beneficial effects: the modification of halogen in the copper-based composite nano material provided by the application is not only beneficial to the modification of a metal exposed crystal face, but also beneficial to the formation of a nanosheet with a high-energy crystal face on a two-dimensional nano copper oxide, so that the finally formed material has rich active sites, and has the effects of high selectivity of producing acetic acid at a low potential, inhibition of hydrogen production at each potential and improvement of the Faraday efficiency of carbon dioxide reduction.)

1. The copper-based composite nanomaterial is characterized by comprising a halogen-modified two-dimensional nano copper oxide and copper nanosheets dispersed on the two-dimensional nano copper oxide, wherein the copper nanosheets have high-energy crystal faces.

2. Copper-based composite nanomaterial according to claim 1, characterized in that said high-energy crystal planes comprise (200) and (220) crystal planes;

preferably, the copper-based composite nanomaterial has an acetic acid selectivity of not less than 27% faradaic efficiency at-0.3V vs.

3. The composite nanomaterial according to any one of claims 1 to 2, wherein the two-dimensional nano copper oxide has a lateral dimension of 100 to 200nm and a thickness of 4 to 10nm, and the copper nanoplatelets have a lateral dimension of 20 to 60nm and a thickness of 2 to 10 nm.

4. A method for preparing copper-based composite nanomaterial according to any of claims 1 to 3, characterized by comprising the steps of:

modifying the electrode by hydroxyl copper halide to prepare a precursor electrode;

providing liquid-phase electrolyte and carbon dioxide, enabling the precursor electrode, the liquid-phase electrolyte and the carbon dioxide to form a three-phase contact interface, and carrying out linear scanning voltammetry treatment on the precursor electrode to obtain the copper-based composite nanomaterial loaded on the conductive substrate;

preferably, the preparation method of the hydroxyl copper halide is as follows: taking a copper source, a halogen source and alkali to perform hydrothermal reaction to obtain the hydroxyl copper halide.

5. The production method according to claim 4, characterized in that the linear sweep voltammetry process is started immediately when the precursor electrode is in contact with the liquid-phase electrolyte;

preferably, the scanning range of the linear scanning voltammetry is 0.2-1V vs.RHE, and the scanning speed is 2-8 mV/s;

preferably, the sweep range of the linear sweep voltammetry is 0 to-0.9V vs.

6. The production method according to claim 4, wherein the liquid-phase electrolyte and the carbon dioxide are in a flowing state;

preferably, the liquid-phase electrolyte is an alkaline electrolyte;

preferably, the alkaline electrolyte is 0.1-5 mol/L of strong base;

preferably, the flow rate of the liquid-phase electrolyte is 10-20 mL/min;

preferably, the flow rate of the carbon dioxide is 10-50 sccm.

7. A catalyst comprising the composite nanomaterial of any of claims 1 to 3.

8. An electrode comprising an electrically conductive substrate and the catalyst of claim 7 supported on the electrically conductive substrate.

9. An electrolysis apparatus comprising the electrode of claim 8;

preferably, the electrolysis device comprises an anode, a cathode, a separator and an electrolyte, wherein the cathode is the electrode of claim 8;

preferably, the electrolysis device comprises a working electrode, a counter electrode, a reference electrode, a diaphragm and an electrolyte, and the working electrode is the electrode of claim 8.

10. The method for preparing acetic acid by electrocatalytic reduction of carbon dioxide is characterized by comprising the following steps: contacting carbon dioxide with the electrode of claim 8, and electrocatalytically reacting to form acetic acid.

Technical Field

The application relates to the technical field of nano catalysts, in particular to a copper-based composite nano material and a preparation method and application thereof.

Background

Carbon dioxide reduction (CO)₂RR) refers to the production of a carbon product in a lower valence state by the reduction of carbon dioxide electrically, thermally or photocatalytically. Reaction for electrocatalytic reduction of carbon dioxideIt should generally be carried out in a three-electrode system, the reaction process being as follows: CO 2₂Adsorption to the catalyst surface, electron transfer and protonation, and desorption of the product from the catalyst surface. According to the reports available at present, the catalysts used in the reaction process can be roughly classified into the following types: metal-based catalysts, which can be further classified into metal catalysts, metal oxide (sulfide) catalysts, metal organic framework material catalysts; carbon material catalysts, and other composite catalysts.

Carbon dioxide has different reaction products under different metal-based catalyst conditions. Generally, formic acid is mainly produced under the catalysis of Pb, Hg, Tl, In, Sn, Cd and Bi, carbon monoxide is mainly produced under the catalysis of Au, Ag, Zn, Pd and Ga, and hydrogen is mainly produced under the catalysis of Ni, Fe, Pt and Ti. In contrast, Cu is the only catalyst that can produce a wide variety of products such as hydrocarbons, aldehydes, alcohols, acids, carbon monoxide, and the like. This also makes copper-based catalysts unique in the electrocatalytic reduction of carbon dioxide. In order to make the reduction of carbon dioxide more industrially valuable, copper-based catalysts are generally used for reduction to produce products with high added values such as alcohols and acids. Among them, acetic acid is an important industrial raw material, but it is still difficult to obtain a highly selective acetic acid product by electrocatalytic reduction of carbon dioxide at present. Therefore, it is necessary to provide a catalyst with high CO₂RR Faraday efficiency and high acetic acid selectivity.

Disclosure of Invention

The present application is directed to solving at least one of the problems in the prior art. Therefore, the application provides a copper-based composite nano material which is taken as a catalyst for electrocatalytic reduction of carbon dioxide and shows high CO₂RR faraday efficiency and high acetic acid selectivity.

The application also aims to provide a preparation method of the copper-based composite nano material.

The application also aims to provide application of the copper-based composite nano material.

In a first aspect of the present application, there is provided a copper-based composite nanomaterial comprising a halogen-modified two-dimensional nano copper oxide and copper nanoplatelets dispersed on the two-dimensional copper oxide, the copper nanoplatelets having high-energy crystal planes.

The copper-based composite nanomaterial according to the embodiment of the application has at least the following beneficial effects:

the modification of halogen in the copper-based composite nano material provided by the application is not only beneficial to the modification of the exposed crystal face of copper, but also beneficial to the formation of nanosheets with high-energy crystal faces on two-dimensional nano copper oxide, so that the finally formed material has rich active sites, and has the effects of high selectivity of producing acetic acid at a low potential, inhibition of hydrogen production at each potential and improvement of Faraday efficiency of carbon dioxide reduction.

Wherein the halogen includes fluorine, chlorine and bromine. The high energy crystal face means that at least one parameter of h, k and l in the crystal face index (h k l) of copper is more than 1. Compared with a low-energy crystal face such as (111), the copper of the high-energy crystal face has a richer surface structure, so that the copper-based nano material shows more excellent catalytic performance.

In some embodiments of the present application, the halogen-modified two-dimensional nano-copper oxide is Cu_xOF，0<x<2。

In some embodiments of the present application, the copper nanoplatelets have more than one high energy crystal plane.

In some embodiments of the present application, the high energy crystal planes include (200) and (220) crystal planes.

In some embodiments of the present application, the halogen-modified two-dimensional nanocopper oxide has a lower hardness than the copper nanoplatelets. In some embodiments, the hardness is determined by phase diagram (phase) mode of Atomic Force Microscopy (AFM) to obtain relative values. In some specific embodiments, the hardness of Si is 0, and the larger the phase value, the higher the hardness. Specifically, the phase value of the halogen modified two-dimensional nano copper oxide is 10-30 degrees lower than that of the copper nanosheet, further 15-25 degrees lower, further 20-25 degrees lower, further about 22 degrees lower, and further about 4 degrees lower than that of the copper nanosheet, and the phase value of the Cu nanosheet is about 4 degrees_xOF has a phase value OF about-18. Wherein "About "means a tolerance of. + -. 5%, further. + -. 2% or. + -. 1%. In addition, Cu in the composite_xOF accounts for a large proportion and thus can also be understood as a composite material having a lower hardness than existing low energy lattice plane copper.

In some embodiments of the present application, the copper-based composite nanomaterial has an acetic acid selectivity of not less than 27% faradaic efficiency at a potential of-0.3V vs.

In some embodiments of the present application, the two-dimensional nano copper oxide has a lateral dimension of 100 to 200nm and a thickness of 4 to 10nm, and the copper nanosheet has a lateral dimension of 20 to 60nm and a thickness of 2 to 10 nm.

In a second aspect of the present application, there is provided a method for preparing the above copper-based composite nanomaterial, the method comprising the steps of:

modifying the electrode by hydroxyl copper halide to prepare a precursor electrode;

providing liquid-phase electrolyte and carbon dioxide, enabling the precursor electrode, the liquid-phase electrolyte and the carbon dioxide to form a three-phase contact interface, and carrying out linear scanning voltammetry treatment on the precursor electrode to obtain the copper-based composite nanomaterial loaded on the conductive substrate.

The preparation method of the copper-based composite nanomaterial according to the embodiment of the application has at least the following beneficial effects:

the method provided by the application enables a precursor electrode to be positioned at a three-phase interface and is positioned at CO₂Is carried out in the atmosphere, thereby preparing the high-energy crystal face copper/halogen modified copper oxide (H-Cu/Cu)_xOF). During the preparation process, the halogen not only contributes to the modification of the exposed crystal face of copper, but also contributes to the reduction of CO₂Under RR condition, Cu (I) is protected from being completely reduced to Cu (0), so that two-dimensional copper nanosheets with high-energy crystal faces are formed and dispersed on the halogen-modified two-dimensional nano copper oxide, the finally formed product has abundant active sites and is used for treating CO₂The reduction shows advanced catalytic activity, and the selectivity of producing acetic acid under low potential and the effect of inhibiting hydrogen production and improving Faraday efficiency under each potential are obviously improved.

Wherein the copper hydroxyhalide comprises Cu₂(OH)₃X or CuOHX, wherein X is one of fluorine, chlorine and bromine. The precursor electrode is obtained by compositely modifying a copper hydroxyhalide precursor to the surface of the electrode by adsorption, deposition, polymer compounding and other modes to change the electrode interface area, and the copper hydroxyhalide precursor participates in the subsequent linear cyclic voltammetry scanning process. The substrate material of the electrode is mainly carbon material, including but not limited to graphite and glassy carbon, carbon paper, carbon cloth, etc., and other materials may also use noble metals such as platinum and semiconductors, etc. The liquid electrolyte includes, but is not limited to, liquid electrolytes, such as potassium hydroxide solution and sodium hydroxide solution.

In some embodiments of the present application, copper hydroxyhalides are modified onto electrodes by polymer compounding to make precursor electrodes. The specific process can be that the hydroxyl copper halide and the polymer adhesive are dispersed in a solvent and compounded on the electrode by dipping, dripping, spin coating and the like. In order to facilitate drying after the electrode is combined, the solvent may be selected from low boiling point organic solvents such as methanol, ethanol, isopropanol, methyl ether, ethyl ether, acetone, methyl ethyl ketone, tetrahydrofuran, and the like. Among them, nafion is preferably used as the polymer adhesive, and the polymer has a hydrophilic sulfonic acid group at the end of a hydrophobic chain and has good selectivity to cations.

In some embodiments of the present application, a mixture of copper hydroxyhalide and 5% Nafion in ethanol is taken, and the mixture is compounded on hydrophobic carbon paper or hydrophobic carbon cloth to form a precursor electrode.

In some embodiments of the present application, the loading of the copper hydroxyhalide on the hydrophobic carbon paper is 0.4 to 2mg/cm²。

In some embodiments of the present application, the 5% Nafion in ethanol solution is added in an amount of 1.6 to 8. mu.l.

In some embodiments of the present application, the copper hydroxyhalide is prepared as follows: taking a copper source, a halogen source and alkali to perform hydrothermal reaction to obtain the hydroxyl metal halide.

Wherein, the copper source refers to soluble copper compounds, and specifically includes but is not limited to soluble copper salts, such as copper nitrate. Halogen source refers to soluble halogen salts, and specifically includes but is not limited to soluble fluorine salts, such as potassium fluoride, sodium fluoride; chlorine salts such as potassium chloride, sodium chloride and the like. The base specifically includes, but is not limited to, sodium hydroxide, ammonia, Hexamethylenetetramine (HMT), and the like.

In some embodiments of the present application, the linear sweep voltammetry process is started immediately upon contact of the precursor electrode with the liquid phase electrolyte. The CuOHF precursor slowly changes to Cu (OH) in the electrolyte₂The progress of the preparation process is influenced, and therefore, the linear sweep voltammetry treatment is started immediately when the two are in contact to avoid the reaction process as much as possible.

In some embodiments of the present application, the sweep range of the linear sweep voltammetry is 0.2 to-1V vs. RHE, and the sweep rate is 2 to 8 mV/s.

In some embodiments of the present application, the sweep range of linear sweep voltammetry is from 0 to-0.9V vs.

In some embodiments of the present application, the number of scanning turns is 1-5 turns. According to the difference of the scanning range and the scanning speed, the precursor undergoes in-situ topological transformation after different scanning turns to obtain the copper-based composite nanomaterial.

In some embodiments of the present application, the liquid phase electrolyte and the carbon dioxide are in a flowing state. In order to effectively keep the reaction continuously, the reaction system needs to be kept flowing so that the concentration of reactant molecules is kept constant, and the product molecules can be quickly removed along with the electrolyte, thereby avoiding the problem that the reaction cannot be continuously carried out in the forward direction after the reaction reaches the equilibrium because the product is not removed.

In some embodiments of the present application, the liquid-phase electrolyte is an alkaline electrolyte.

In some embodiments of the present application, the alkaline electrolyte is 0.1 to 5mol/L of a strong base, such as sodium hydroxide, potassium hydroxide, and the like.

In some embodiments of the present application, the flow rate of the liquid-phase electrolyte is 10 to 20 mL/min.

In some embodiments of the present application, the flow rate of carbon dioxide is 10 to 50 sccm.

In a third aspect of the present application, there is provided a catalyst comprising the composite nanomaterial described above.

In a fourth aspect of the present application, there is provided an electrode comprising an electrically conductive substrate and the foregoing catalyst supported on the electrically conductive substrate. The conductive substrate may be a carbon material, including but not limited to graphite and glassy carbon, carbon paper, carbon cloth, etc., and other materials may also be used, such as noble metals, e.g., platinum, semiconductors, etc.

In a fifth aspect of the present application, there is provided an electrolysis apparatus comprising the aforementioned electrode.

In some embodiments of the present application, the electrolysis device comprises an anode, a cathode, a separator, and an electrolyte, the cathode being the aforementioned electrode.

In some embodiments of the present application, the electrolysis device is an electrolysis Flow Cell device (Flow Cell) comprising a cathode compartment, an anode compartment, a gas Flow Cell, a diaphragm, an anode compartment electrolyte Flow rate controller, a cathode compartment electrolyte Flow rate controller, and a CO₂A gas flow rate controller. Wherein, be equipped with negative pole and electrolyte in the cathode chamber, the negative pole is aforementioned electrode, is equipped with positive pole and electrolyte in the anode chamber, and the diaphragm is used for keeping apart electrolyte in the cathode chamber and the electrolyte in the anode chamber. The anode chamber electrolyte flow rate controller and the cathode chamber electrolyte flow rate controller are used for controlling the flow rates of the anolyte in the anode chamber and the catholyte in the cathode chamber respectively.

In some embodiments of the present application, CO₂Gas flow rate controller for mixing CO₂The flow rate of the cathode chamber electrolyte is controlled to be 10-50 sccm, and the flow rate of the cathode electrolyte is controlled to be 10-20 mL/min by the cathode chamber electrolyte flow rate controller.

In some embodiments of the present application, CO₂The flow rate of (2) is 15sccm, and the flow rate of the electrolyte is 15 mL/min.

In some embodiments of the present application, the electrolysis device comprises a working electrode, a counter electrode, a reference electrode, a separator, and an electrolyte, the working electrode being the aforementioned electrode. The counter electrode includes, but is not limited to, carbon material electrodes (e.g., carbon sheet electrode, glassy carbon electrode), metal electrodes (e.g., nickel electrode, platinum electrode), and othersAnd an electrode. Reference electrodes include, but are not limited to, Ag/AgCl electrodes, Hg/HgO electrodes. Electrolytes include, but are not limited to, KOH solution, NaOH solution, KCl solution, NaCl solution, NaHCO₃Solution, KHCO₃Solution, Na₂CO₃Solution, K₂CO₃And (3) solution. The membrane includes but is not limited to proton exchange membrane, ion exchange membrane, and in particular perfluorosulfonic acid proton exchange membrane (such as nafion proton exchange membrane and other modified proton exchange membranes based thereon) and anion exchange membrane.

In some embodiments of the present application, the electrolyte is 0.1 to 1M KOH or NaOH solution.

In some embodiments of the present application, the electrolyte is a 1M KOH or NaOH solution.

In a fifth aspect of the present application, there is provided a process for the preparation of acetic acid by electrocatalytic reduction of carbon dioxide, the process comprising the steps of: carbon dioxide is contacted with the electrode to generate acetic acid through electrocatalytic reaction.

In some embodiments of the present application, carbon dioxide is passed to the electrolysis apparatus described above, the carbon dioxide is contacted with an electrode to cause an electrocatalytic reduction reaction, and the resulting liquid product is collected, from which acetic acid is separated.

According to the preparation method of the copper-based composite nano material provided by the embodiment of the application, the hydroxyl copper halide precursor is positioned at a three-phase interface and is in CO₂Reacting in the atmosphere to prepare the high-energy crystal face copper/fluorine modified copper oxide compound (H-Cu/Cu)_xOF)。H-Cu/Cu_xOF is used as a copper-based composite nanomaterial, wherein the presence OF halogen not only contributes to the modification OF the exposed crystal face OF copper, but also can contribute to CO reduction₂And under the RR condition, Cu (I) is protected from being completely reduced to Cu (0), and two-dimensional nano copper sheets with high-energy crystal faces are formed and dispersed on the fluorine-modified two-dimensional nano copper oxide, so that the catalyst has rich active sites. H-Cu/Cu_xOF to CO₂The reduction shows excellent catalytic activity, and the faradaic efficiency reaches 27 percent when the potential of the produced acetic acid is-0.3V (vs RHE).

CO can be prepared by using the copper-based composite nano material provided by the application₂RR catalyst and CO₂And an RR electrode. Compared with hydrophobic carbon paper and corresponding catalyst which is not modified by fluorine and is converted from copper hydroxide by the same treatment method and has low-energy crystal face copper, the product provided by the embodiment of the application has more obvious selectivity of producing acetic acid at low potential, and has more obvious inhibition of hydrogen production and improvement of CO at each potential₂Effect of RR faraday efficiency.

Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.

Drawings

In FIG. 1, A and B are scanning electron micrographs of the CuOHF precursor at 1 μm and 200nm, respectively.

In FIG. 2, A and B are H-Cu/Cu, respectively_xOF scanning electron micrographs at 200nm and 100nm on a scale.

In FIG. 3A is H-Cu/Cu_xOF transmission electron micrographs at 100nm on the scale, B and C are high resolution lattice fringes at 10nm on the corresponding scale.

FIG. 4 shows Cu (OH)₂、CuOHF、L-Cu、H-Cu/Cu_xAnd the X-ray diffraction pattern OF.

In FIG. 5A is H-Cu/Cu_xOF atomic force microscopy topography, B and C are height maps OF the 1 and 2 positions in a, respectively.

In FIG. 6, A and B are H-Cu/Cu, respectively_xOF is a phase diagram and a phase angle diagram OF an atomic force microscope, and C and D are a phase diagram and a phase angle diagram OF an atomic force microscope OF L-Cu, respectively.

In FIG. 7, A is the precursors CuOHF and H-Cu/Cu_xOF in CO₂X-ray photoelectron spectroscopy of the 1s position of the F element before and after the RR process; b is a precursor Cu (OH)₂CuOHF and H-Cu/Cu_xOF in CO₂X-ray photoelectron spectroscopy of the 1s position of the O element before and after the RR process; c is a precursor Cu (OH)₂L-Cu and H-Cu/Cu_xOF in CO₂X-ray photoelectron spectroscopy of 2p position of Cu element before and after RR process; d is H-Cu/Cu_xX-ray photoelectron energy OF Cu 2p 3/2 position after peak separation OF OFSpectra.

FIG. 8 shows H-Cu/Cu_xElectron paramagnetic resonance spectra OF OF and L-Cu.

Fig. 9 is a schematic of the structure of an electrolytic flow cell used in the carbon dioxide reduction test.

In FIG. 10, A is H-Cu/Cu_xLinear voltammograms OF OF and L-Cu; b is H-Cu/Cu_xOF in CO₂Hydrogen production (HER) and carbon dioxide reduction (CO) at various potentials in the RR process₂RR) current density plot.

In FIG. 11A is H-Cu/Cu_xOF product Faraday efficiency distribution histogram under each potential; b is H-Cu/Cu_xOF and L-Cu in CO₂A Faraday efficiency trend graph of carbon dioxide reduction at each potential in the RR process; c is H-Cu/Cu_xOF and L-Cu in CO₂And (3) a Faraday efficiency trend chart of hydrogen production under each potential in the RR process.

FIG. 12 shows H-Cu/Cu_xAnd (3) comparing the Faraday efficiencies OF different products under the catalysis OF OF and L-Cu under various potentials to obtain a histogram, wherein the product in the step (A) is carbon monoxide, the product in the step (B) is formic acid, the product in the step (C) is ethylene, the product in the step (D) is acetic acid, and the product in the step (E) is ethanol.

Reference numerals: carbon dioxide channel 110, channel inlet 111, channel outlet 112, working electrode 120, diaphragm layer 130, cathode chamber 140, cathode chamber inlet 141, cathode chamber outlet 142, anode chamber 150, anode chamber inlet 151, anode chamber outlet 152, counter electrode 160, reference electrode 170.

Detailed Description

The conception and the resulting technical effects of the present application will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all embodiments, and other embodiments obtained by those skilled in the art without inventive efforts based on the embodiments of the present application belong to the protection scope of the present application.

The following detailed description of embodiments of the present application is provided for the purpose of illustration only and is not intended to be construed as a limitation of the application.

In the description of the present application, the meaning of a plurality is one or more, the meaning of a plurality is two or more, and the above, below, exceeding, etc. are understood as excluding the present number, and the above, below, within, etc. are understood as including the present number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present application, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Example 1

This example provides a high energy lattice copper/fluorine modified copper oxide composite (H-Cu/Cu)_xOF), the preparation method OF the copper-based composite nano-material is as follows:

synthesis of CuOHF precursor

CuOHF is synthesized by a one-step hydrothermal method, and comprises the following specific steps: 0.46g of copper nitrate trihydrate and 0.21g of Hexamethylenetetramine (HMT) were dissolved in 15mL of deionized water, stirred at room temperature for 10 minutes, and then stirred for 15 minutes after the addition of 0.44g of KF with constant stirring. Pouring the mixed solution into a stainless steel-lined polytetrafluoroethylene high-pressure reaction kettle and sealing. Then heated in an oven to 95 ℃ at a rate of 5 ℃/min and held at this temperature for 2 hours. After the heat preservation is finished, the high-pressure autoclave is naturally cooled to the room temperature, the reaction product is centrifuged and washed by deionized water for a plurality of times, and finally washed by ethanol for a plurality of times and dried in a vacuum oven at 60 ℃ for one night. And obtaining a green product, namely the hydroxyl copper fluoride.

2.H-Cu/Cu_xPreparation OF

2mg of CuOHF precursor powder prepared in step 1 and 16. mu.l of 5% Nafion ethanol solution were added to 400. mu.l of ethanol, and after sonication for 2 hours, the mixture was applied to 1cm²The carbon paper is made into a precursor electrode.

The precursor electrode is used as a working electrode, Hg/HgO and a carbon sheet are respectively used as a reference electrode and a counter electrode to form a three-electrode system, a 1M KOH solution with the flow rate of 15mL/min is selected as an electrolyte, and CO is introduced into the three-electrode system at the flow rate of 20sccm₂. Once the working electrode was in contact with the electrolyte, a linear sweep voltammetry sweep (0 to-0.9V (vs. RHE), 5mV/s) was started immediately. After 3 times of scanning, the LSV curve is stable, and the catalyst undergoes in-situ topological transformation to obtain the copper-based nanocomposite H-Cu/Cu_xOF。

Comparative example 1

The comparative example provides a copper-based nanomaterial, and the preparation method of the copper-based nanomaterial comprises the following steps:

1.Cu(OH)₂synthesis of precursors

Cu(OH)₂Synthesized by a chemical coprecipitation method, and the specific process is as follows: 1.21g of copper nitrate trihydrate was dissolved in 15mL of deionized water and then sonicated for 5 minutes, and 5mL of 1M KOH solution was poured into the solution with vigorous stirring. After completion of the reaction, the mixture was transferred to a beaker containing 1L of deionized water to allow it to settle, and then the supernatant was removed. Finally, the product was transferred to a 50mL centrifuge tube, washed several times with deionized water and ethanol, and dried overnight in a vacuum oven at 60 ℃ to give a blue colored Cu (OH)₂。

Preparation of L-Cu

2mg of precursor powder Cu (OH) was added to 400. mu.l of ethanol₂And 16. mu.l of 5% Nafion ethanol solution, sonicated for 2 hours, and the mixture was smeared on 1cm²The carbon paper is made into a precursor electrode.

The precursor electrode is used as a working electrode, Hg/HgO and a carbon sheet are respectively used as a reference electrode and a counter electrode to form a three-electrode system, a 1M KOH solution with the flow rate of 15mL/min is selected as an electrolyte, and three electrodes are simultaneously arranged at the flow rate of 20sccmIntroducing CO into the electrode system₂. Once the working electrode was in contact with the electrolyte, a linear sweep voltammetry sweep (0 to-0.9V (vs. RHE), 5mV/s) was started immediately. After 3 times of scanning, the LSV curve is stable, and the catalyst undergoes in-situ topological transformation to obtain the copper-based nano material L-Cu.

Characterization results

Fig. 1 is a scanning electron microscope photograph of a CuOHF precursor synthesized by a hydrothermal method in step 1 of example 1, wherein scales in a and B are 1 μm and 200nm, respectively, and it can be seen from the figure that the morphology of the CuOHF precursor is a two-dimensional nanostructure.

FIG. 2 shows the H-Cu/Cu finally prepared in example 1_xOF scanning Electron micrograph, scales OF A and B are 200nm and 100nm, respectively, and it can be seen from the figure that H-Cu/Cu obtained by the final preparation_xOF retained a two-dimensional morphology similar to the precursor.

FIG. 3 is H-Cu/Cu_xOF TEM photograph and corresponding high resolution lattice fringes, as can be seen in A OF FIG. 3, H-Cu/Cu_xOF is lamellar morphology; b shows that the copper-based composite nano material has copper with high-energy crystal faces, such as Cu (220) and Cu (200); and oxides of copper, e.g. Cu₂O (111) two lattice structures.

FIG. 4 is the precursor CuOHF and the product H-Cu/Cu in example 1_xOF and the precursor Cu (OH) in comparative example 1₂And the X-ray diffraction pattern of the product L-Cu. As can be seen from the results in FIG. 4, H-Cu/Cu_xOF and L-Cu undergo a material transition compared to the respective precursors. But H-Cu/Cu_xOF has two lattice structures OF copper and copper oxide with high-energy crystal planes (200) and (220), while L-Cu without F modification does not contain high-energy crystal plane copper. The results indicate that F plays a role in the formation of high energy facet copper.

A in FIG. 5 is H-Cu/Cu in example 1_xAnd OF, B and C are height maps at the 1 and 2 arrows in a, respectively. With reference to FIG. 3, H-Cu/Cu_xThe OF composite nano material comprises fluorine modified two-dimensional nano copper oxide (Cu)_xOF, lateral dimension OF about 100 to 200nm, thicknessDegree of about 4 to 10nm), and two-dimensional nano copper sheets (H-Cu, transverse dimension of about 20 to 60nm, thickness of about 2 to 10nm) having high energy crystal faces dispersed on the two-dimensional nano copper oxide.

FIG. 6 is H-Cu/Cu_xOF is a phase diagram (A) and a phase angle diagram (B) OF an atomic force microscope, and L-Cu is a phase diagram (C) and a phase angle diagram (D) OF an atomic force microscope. The results in FIG. 6 show that H-Cu/Cu_xOF is a composite structure OF high energy lattice copper and fluorine-modified copper oxide, while L-Cu OF comparative example 1 has a structure OF Cu (0) alone. In addition, H-Cu and L-Cu have similar hardness since the phase difference is related to the surface hardness, while Cu_xOF is softer in texture than H-Cu and L-Cu. In this case, H-Cu/Cu_xWhen the OF is used as a catalyst, the structure is easier to adjust in the carbon dioxide reduction reaction comprising the steps OF electron transfer and absorption and desorption, and the absorption and desorption process is facilitated, so that the catalyst has a higher catalytic effect.

In FIG. 7, A is the precursors CuOHF and H-Cu/Cu_xOF in CO₂X-ray photoelectron spectroscopy of the 1s position of the F element before and after the RR process shows that the peak of F in H-Cu/CuxOF is much sharper than that of CuOHF precursor, indicating that the electron state of F in H-Cu/CuxOF is very uniform. B is the precursor Cu (OH)₂CuOHF and H-Cu/Cu_xOF in CO₂X-ray photoelectron spectroscopy of the 1s position of O element before and after RR process, as can be seen from the figure, H-Cu/Cu_xOF in which the binding energy OF O is slightly larger than that OF Cu (OH)₂And less than CuOHF, indicating that F has a strong influence on the electrons of O. C is a precursor Cu (OH)₂L-Cu and H-Cu/Cu_xOF in CO₂X-ray photoelectron spectroscopy at the 2p position of Cu element before and after RR process, D is H-Cu/Cu_xThe X-ray photoelectron spectroscopy OF Cu 2p 3/2 position after the peak OF OF, from C, it can be seen that L-Cu shows a peak at about 932.5eV, indicating that it is metallic Cu with a valence OF 0. And H-Cu/Cu_xOF bonding C and D it can be seen that, in addition to Cu (0), there is Cu between Cu (0) and Cu (I)^δ+Peak of (2).

FIG. 8 is H-Cu/Cu_xElectron paramagnetic resonance spectra OF OF and L-Cu, as can be seen from the figure, L-Cu and H-Cu/Cu_xOF is connected in g valueNearly 2.62 to 2.63, indicating L-Cu and H-Cu/Cu_xThe energy difference between the two spin states OF a single electron in OF is small. However, H-Cu/Cu_xOF shows a relatively smaller peak width than that OF L-Cu, indicating that the electron-electron dipolar action is stronger due to the modification by F.

₂Carbon dioxide reduction test (CORR)

The carbon dioxide reduction test was performed using an electrolytic flow cell structure, as shown in fig. 9, which includes a cathode chamber 140, a diaphragm 130, and an anode chamber 150, the cathode chamber 140 and the anode chamber 150 being partitioned by the diaphragm 130, the cathode chamber 140 and the anode chamber 150 being filled with an electrolyte, a working electrode 120 being provided on one side of the cathode chamber 140, a reference electrode 170 being provided in the cathode chamber 140, the reference electrode 170 not blocking the entire cathode chamber 140, and a carbon dioxide passage 110 being provided on one side of the working electrode 120 away from the cathode chamber 140. A counter electrode 160 is provided on the side of the anode chamber 150 remote from the cathode chamber 140. The carbon dioxide channel 110, the working electrode 120, and the cathode chamber 140 may form a carbon dioxide-electrode-electrolyte three-phase interface. The carbon dioxide passage 110 has a passage inlet 111 and a passage outlet 112, and the passage inlet 111 is connected with CO₂Air pump and CO₂A flow rate controller (not shown) and unreacted carbon dioxide and gaseous products produced by the reaction are discharged from the outlet 112 of the passage. The cathode chamber 140 is provided with a cathode chamber inlet 141 and a cathode chamber outlet 142, and the anode chamber 150 is provided with an anode chamber inlet 151 and an anode chamber outlet 152. The electrolyte is introduced into the cathode chamber 140 and the anode chamber 150 through the cathode chamber inlet 141 and the anode chamber inlet 151, respectively, and discharged through the cathode chamber outlet 142 and the anode chamber outlet 152, respectively. The cathode chamber inlet 141 and the anode chamber inlet 151 are also connected to a cathode chamber electrolyte flow rate controller and an anode chamber electrolyte flow rate controller (not shown) respectively for controlling the flow rates of the electrolytes in the cathode chamber 140 and the anode chamber 150. Working electrode 120 is CO₂And the RR working electrode, the counter electrode 160 is a carbon sheet counter electrode, and the reference electrode 170 is an Hg/HgO reference electrode. The working electrode 120, the counter electrode 160 and the reference electrode 170 are connected to an electrochemical workstation (not shown) through external leads. CO 2₂The RR working electrode comprises hydrophobic carbon paper and hydrophobic carbon paper loaded on the hydrophobic carbon paperA catalyst on a support. The membrane layer 130 separates the cathode compartment 140 from the anode compartment 150 using an anion exchange membrane (Fuma FAA-PK-130, Gaossuinion) with a 1M KOH solution. High purity CO during the test₂The working electrode was continuously flowed at a constant flow rate of 20 sccm. CO 2₂The constant potential applied during RR ranges from-0.3V (vs. rhe) to-0.8V (vs. rhe). In addition, a gas chromatograph (GC2014C, SHIMADZU Excellence in Science) equipped with two flame ionization detectors (DFID and SFID) and one Thermal Conductivity Detector (TCD) analyzes the gas product at the channel outlet 112, wherein the hydrogen concentration is determined by the TCD detector, CO and C₂H₄Concentrations were determined from DFID and SFID, respectively. And the liquid product concentration at cathode chamber outlet 142 is selected¹H-NMR spectroscopy (AVANCE-III, 400MHz, Bruker) was performed, and the liquid products were quantitatively analyzed using Dimethylsulfoxide (DMSO) as an internal standard. All tests were performed at room temperature.

CO₂In RR process, carbon dioxide reduction product is used as gaseous product H₂、CO、CH₄、C₂H₄And liquid products HCOOH, CH₃COOH, EtOH (ethanol), n-PrOH (propanol) for example,

faraday current i_total＝{i_H2+i_CO+i_CH4+i_C2H4}_{Gaseous state}+{i_HCOOH+i_CH3COOH+i_EtOH+i_n-PrOH}_{Liquid state}

And the faradaic efficiency FE ═ i of the product a_a/i_totalWherein a is selected from H₂、CO、CH₄、C₂H₄、HCOOH、CH₃COOH、EtOH、n-PrOH。

H-Cu/Cu prepared in example 1 and comparative example 1 were selected_xOF and L-Cu were tested under the same conditions as catalysts on the working electrode. The results are shown in FIG. 10, where A is H-Cu/Cu_xOF and L-Cu, H-Cu/Cu as shown in the graph_xOF has a higher current density at the same potential compared to L-Cu, indicating that it has a higher catalytic activity. B is H-Cu/Cu_xOF in CO₂At each potential in RR processHydrogen production (HER) and carbon dioxide reduction (CO)₂RR), from which CO is seen as the voltage increases₂The larger the difference between the current density of RR and that of HER, the results indicate that H-Cu/Cu_xOF as catalyst prefers to catalyze CO₂And (3) RR. Further, at a potential of-0.3V (vs. RHE), H-Cu/Cu_xThe Faraday current OF the OF catalytic acetic acid production reaches about 4mA/cm²。

In FIG. 11A is H-Cu/Cu_xOF histogram OF the product Faraday efficiency distribution at each potential, it can be seen that at-0.3V (vs. RHE), the Faraday efficiency OF acetic acid reached 27%, and then the Faraday efficiency OF acetic acid gradually decreased as the voltage increased. B is H-Cu/Cu_xOF and L-Cu in CO₂The Faraday efficiency trend chart of carbon dioxide reduction under each potential in RR process shows that H-Cu/CuxOF has better catalytic CO compared with L-Cu₂RR selectivity, and over 70% carbon dioxide reduction selectivity at a potential of-0.7V (vs. RHE); c is H-Cu/CuxOF and L-Cu in CO₂The Faraday efficiency trend chart of hydrogen production under each potential in RR process shows that H-Cu/Cu_xOF has better performance OF inhibiting hydrogen production compared with L-Cu.

FIG. 12 is H-Cu/Cu_xGraph comparing the faradaic efficiency at various potentials for different products under OF catalysis, A represents carbon monoxide, B represents formic acid, C represents ethylene, D represents acetic acid, and E represents ethanol. As can be seen from the results in the figure, example 1 provides H-Cu/Cu_xThe structure OF is advantageous for catalyzing CO₂Conversion to C₂The product, L-Cu, is more prone to catalyzing C₁And (3) obtaining the product. Wherein, at-0.3V (vs. RHE), H-Cu/Cu_xThe Faraday efficiency OF OF acetic acid production reaches 27 percent, while that OF L-Cu acetic acid production is only about 12 percent, and the Faraday efficiency OF example 1 is improved by more than one time compared with that OF the comparative example. The experimental results show that under the same potential condition, especially under the low potential, H-Cu/Cu_xOF C₂The product is higher than L-Cu.

Example 2

This example provides a copper-based composite nanomaterialThe difference from the example 1 is that copper nano-sheets with high-energy crystal faces are dispersed in chlorine-modified two-dimensional nano-copper oxide, and the difference from the example 1 is that equimolar KCl is used to replace KF. The copper-based composite material was examined to have a similar morphology structure as in example 1, and CO was₂RR experiments show that the method has the effects of high selectivity of producing acetic acid at low potential, hydrogen production inhibition at each potential and improvement of Faraday efficiency of carbon dioxide reduction.

Example 3

This example provides a copper-based composite nanomaterial, which is different from example 1 in that copper nanosheets having high-energy crystal planes are dispersed in bromine-modified two-dimensional nano copper oxide, and the preparation method is different from example 1 in that equimolar NaBr is used instead of KF. The copper-based composite material was examined to have a similar morphology structure as in example 1, and CO was₂RR experiments show that the method has the effects of high selectivity of producing acetic acid at low potential, hydrogen production inhibition at each potential and improvement of Faraday efficiency of carbon dioxide reduction.

Example 4

This example provides a copper-based composite nanomaterial, which differs from example 1 in that the electrolyte is 2M NaHCO₃The solution replaced the 1M KOH solution. The copper-based composite material was examined to have a similar morphology structure as in example 1, and CO was₂RR experiments show that the method has the effects of high selectivity of producing acetic acid at low potential, hydrogen production inhibition at each potential and improvement of Faraday efficiency of carbon dioxide reduction.

The present application has been described in detail with reference to the embodiments, but the present application is not limited to the embodiments described above, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present application. Furthermore, the embodiments and features of the embodiments of the present application may be combined with each other without conflict.