阅读说明：本技术 一种具有高指数晶面的铜纳米电极及其制备方法和用途 (Copper nano electrode with high-index crystal face and preparation method and application thereof ) 是由 邝允 韩璐 孙晓明 于 2020-04-08 设计创作，主要内容包括：本发明属于电极材料技术领域,特别涉及一种具有高指数晶面的铜纳米电极、及其制备方法和用途。所述电极包括导电基底以及负载于所述导电基底表面的铜纳米线聚集体；所述铜纳米线长度为10-200μm,长径比大于1000,所述铜纳米线表面具有台阶状的形貌,具有高指数晶面,所述高指数晶面包括但不限于<200>、<220>、<222>、<311>、<310>、<320>、<331>、<400>、<510>、<511>、<533>、<610>、<755>高指数晶面。本发明还公开了上述电极的制备方法和用途。本发明首次制备了高指数晶面的电极材料,用于电化学还原二氧化碳时可以很好的抑制副反应,对高碳产物乙烯、乙醇以及异丙醇有很好的选择性。(The invention belongs to the technical field of electrode materials, and particularly relates to a copper nano electrode with a high-index crystal face, and a preparation method and application thereof. The electrode comprises a conductive substrate and a copper nanowire aggregate loaded on the surface of the conductive substrate; the length of the copper nanowire is 10-200 μm, the length-diameter ratio is more than 1000, the surface of the copper nanowire has a step-shaped appearance and has a high-index crystal face, and the high-index crystal face comprises but is not limited to <200>, <220>, <222>, <311>, <310>, <320>, <331>, <400>, <510>, <511>, <533>, <610>, <755> high-index crystal faces. The invention also discloses a preparation method and application of the electrode. The electrode material with the high-index crystal face is prepared for the first time, can well inhibit side reactions when used for electrochemically reducing carbon dioxide, and has good selectivity on high-carbon products such as ethylene, ethanol and isopropanol.)

1. The copper nano electrode with the high-index crystal face is characterized by comprising a conductive substrate and a copper nanowire aggregate loaded on the surface of the conductive substrate; the copper nanowire has a face centered cubic crystal structure and has high index crystal planes including, but not limited to <200>, <220>, <222>, <311>, <310>, <320>, <331>, <400>, <510>, <511>, <533>, <610>, and <755> crystal planes.

2. The copper nano-electrode according to claim 1, wherein the conductive substrate is selected from one or more of carbon paper, carbon cloth, copper foil, copper foam or titanium foam.

3. The copper nanoelectrode according to claim 1, wherein the copper nanowire has a length of 10-200 μm and an aspect ratio of more than 1000.

4. The copper nanoelectrode of claim 1, wherein the surface of the copper nanowire has a step-like topography.

5. A method for preparing the copper nanoelectrode according to claim 1, comprising the steps of:

(1) adding a copper salt solution into an alkaline solution, uniformly mixing, adding ethylenediamine, then adding a hydrazine solution into the mixed solution, and reacting to obtain a copper nanowire dispersion solution;

(2) and (2) coating the copper nanowire dispersion liquid obtained in the step (1) on a conductive substrate, drying to obtain the conductive substrate coated with the copper nanowires, and treating the conductive substrate for a certain time by adopting a square wave potential method to obtain the copper nanowire electrode.

6. The method according to claim 5, wherein the conductive substrate in step (2) is selected from one or more of copper foil, copper foam, titanium foam, carbon paper, and carbon cloth.

7. The preparation method according to claim 5, wherein the square wave potential treatment method adopts a three-electrode system, the working electrode is the conductive substrate coated with the copper nanowires in the step (2), the reference electrode is a silver-silver chloride electrode, and the counter electrode is a carbon rod, carbon paper or carbon cloth; the processing time of the square wave potential is longer than 5 minutes, the switching frequency of the square wave potential is larger than 2 Hz, the absolute value of the current density of the working electrode at the high potential is lower than that of the current density at the low potential, the high potential of the working electrode is higher than 0.15 volt, and the low potential is lower than 0 volt relative to the standard hydrogen electrode and relative to the standard hydrogen electrode.

8. The method according to claim 5, wherein the electrolyte in the square wave potentiometric treatment process is selected from potassium bicarbonate solution, sodium bicarbonate solution, potassium carbonate solution, sodium carbonate solution, potassium sulfate solution, sodium sulfate solution, potassium chloride solution, potassium bromide solution, sodium bromide solution, and sodium chloride solution.

9. Use of the copper nanoelectrode of claim 1 for electrochemical reduction of carbon dioxide, wherein the copper nanoelectrode can improve the selectivity of high carbon products.

Technical Field

The invention belongs to the technical field of electrode materials, and particularly relates to a copper nano electrode with a high-index crystal face, and a preparation method and application thereof.

Background

In recent years, with the mass exploitation and use of fossil fuels, the content of carbon dioxide in the atmosphere is increased dramatically, and a series of serious environmental problems such as greenhouse effect, global warming and the like are caused. Meanwhile, the problem of energy crisis is increasingly highlighted, and the reduction of the carbon dioxide content in the atmosphere and the search of novel clean energy become important problems. The electrocatalytic carbon dioxide reduction technology converts excessive carbon dioxide in the atmosphere into renewable fuels or value-added chemicals without generating additional pollutants, is an effective means for realizing carbon cycle and solving energy and environmental problems, and thus becomes a hot spot of people.

With the research, the copper-based material has a great application prospect in the electrocatalytic carbon dioxide reduction technology, and can catalyze the carbon dioxide reduction to generate a high-order hydrocarbon product with high commercial value. However, the search for copper-based catalysts with high current density and high product selectivity for carbon dioxide reduction remains a great challenge due to low product selectivity, difficulty in suppressing side reactions (hydrogen evolution reactions), and the like.

The present invention has been made to solve the above problems.

Disclosure of Invention

The invention provides a copper nano electrode with a high-index crystal face, which comprises a conductive substrate and a copper nano wire aggregate loaded on the surface of the conductive substrate; the copper nanowire has a face centered cubic crystal structure and has high index crystal planes including, but not limited to <200>, <220>, <222>, <311>, <310>, <320>, <331>, <400>, <510>, <511>, <533>, <610>, and <755> crystal planes.

Preferably, the conductive substrate is selected from one or more of carbon paper, carbon cloth, copper foil, copper foam or titanium foam.

Preferably, the copper nanowire has a length of 10-200 μm and an aspect ratio of greater than 1000.

Preferably, the surface of the copper nanowire has a step-like morphology. The copper material is essentially face centered cubic.

The lattice plane index is one of constants of the crystal, a plane passing through any three nodes in the space lattice is called a lattice plane, and the lattice plane is characterized by adopting the lattice plane index. The plane index is the reciprocal ratio of the intercept coefficients of a plane on 3 crystal axes, and the 3 integers obtained after conversion to the simplest integer ratio are called the Miller index of the plane. When 4 crystal axes are selected for hexagonal and trigonal crystals, 4 intercept coefficients exist for one crystal plane, and 4 integers obtained from the reciprocal ratio of the two are called the Miller-Blawian index of the crystal plane. The two indices are generally known as the plane indices. The miller index is used herein to represent the plane index.

Whereas the high index crystal planes mean that the spacing of the crystal planes is relatively large with respect to the low index crystal planes.

The high index facets described herein are divided by the miller index, and high index facets provided that one number is greater than or equal to 2. For example, the three fundamental crystal planes <111>, <110>, <100> are low index crystal planes, and the crystal planes <220>, <211>, <311>, <310> are high index crystal planes.

The copper nanowire electrode is a plurality of disordered parallel copper nanowires loaded on the conductive substrate.

Preferably, the conductive substrate is selected from one or more of carbon paper, carbon cloth, copper foil, copper foam or titanium foam.

The second aspect of the present invention provides a method for preparing a copper nano-electrode according to the first aspect, comprising the following steps:

(1) adding a copper salt solution into an alkaline solution, uniformly mixing, adding ethylenediamine, then adding a hydrazine solution into the mixed solution, and reacting to obtain a copper nanowire dispersion solution;

(2) and (2) coating the copper nanowire dispersion liquid obtained in the step (1) on a conductive substrate, drying to obtain the conductive substrate coated with the copper nanowires, and treating the conductive substrate for a certain time by adopting a square wave potential method to obtain the copper nanowire electrode.

Preferably, the conductive substrate in step (2) is one or more selected from copper foil, copper foam, titanium foam, carbon paper, or carbon cloth.

Preferably, the square wave potential treatment method adopts a three-electrode system, the working electrode is the conductive substrate coated with the copper nanowires in the step (2), the reference electrode is a silver-silver chloride electrode, and the counter electrode is a carbon rod, carbon paper or carbon cloth; the processing time of the square wave potential is longer than 5 minutes, the switching frequency of the square wave potential is larger than 2 Hz, the absolute value of the current density of the working electrode at the high potential is lower than that of the current density at the low potential, the high potential of the working electrode is higher than 0.15 volt, and the low potential is lower than 0 volt relative to the standard hydrogen electrode and relative to the standard hydrogen electrode.

Preferably, the electrolyte in the square wave potentiometric treatment process is selected from potassium bicarbonate solution, sodium bicarbonate solution, potassium carbonate solution, sodium carbonate solution, potassium sulfate solution, sodium sulfate solution, potassium chloride solution, potassium bromide solution, sodium bromide solution or sodium chloride solution.

The invention provides a use of the copper nano-electrode of the first aspect for electrochemical reduction of carbon dioxide, which can improve selectivity of high carbon products. In particular, the yield of ethylene products can be improved, and meanwhile, the side reaction hydrogen evolution reaction is well inhibited.

Wherein the high carbon product/higher order hydrocarbon product is ethylene, ethanol and isopropanol.

The technical scheme can be freely combined on the premise of no contradiction.

The invention has the following beneficial effects:

1. the invention prepares the electrode material with high-index crystal face for the first time. The copper nanowire loaded on the conductive substrate has uniform size, the length is about 10-200 mu m, the diameter is about 50-100nm, the length-diameter ratio is more than 1000, the surface of the copper nanowire has a step-shaped appearance, and the copper nanowire is rich in a large number of high-index crystal faces and has a rough surface.

2. The copper nano-electrode material can well inhibit side reactions when used for electrochemically reducing carbon dioxide, and has good selectivity on high-carbon products such as ethylene, ethanol and isopropanol. The standard hydrogen electrode is used as a standard, the faradaic efficiency of the hydrogen is controlled within 30 percent in the range of minus 0.9 volt to minus 1.3 volt; the faradaic efficiency of the high carbon product reaches 60% at minus 1.1 volts, with the faradaic efficiency of the product ethylene reaching 40%.

3. The copper nano electrode material has good catalytic stability in the electrocatalytic carbon dioxide reduction reaction. The catalytic activity and stability of the catalyst can be kept for more than 6 hours continuously at minus 1.1 volts by taking a reversible hydrogen electrode as a standard. And the appearance of the electrode material is not changed greatly, so that the structure of the electrode material is proved to have good stability.

4. The preparation method is simple, the prepared high-index crystal face is relatively stable, the selectivity of the electrocatalytic carbon dioxide reduction reaction is relatively high, and the method is convenient for popularization and industrialization.

Drawings

Fig. 1 is a scanning electron microscope image of the copper nanowire electrode material prepared in example 1.

FIG. 2 is a scanning electron microscope image of the high-index lattice plane copper nanowire electrode material prepared in example 1.

Fig. 3 is an X-ray diffraction pattern of the copper nanowire electrode material before and after the square wave treatment of example 1, wherein fig. 3a is a conductive base material, and fig. 3b is a sample (containing a conductive base material).

Fig. 4a is an electron diffraction pattern of the copper nanowire electrode material obtained after square wave treatment in example 1.

Fig. 4b is an electron diffraction pattern of the copper nanowire electrode material without square wave treatment in example 1.

Fig. 5 is a graph of faraday efficiency and current density of electrochemical reduction of carbon dioxide in potassium chloride solution for the copper nanowire electrode in example 2, fig. 5a and 5b use copper nanowire electrode material after square wave treatment, and fig. 5c and 5d use copper nanowire electrode material before square wave treatment.

FIG. 6 is a graph showing the stability of the copper nanowire electrode in electrochemical reduction of carbon dioxide in a potassium chloride solution in example 2.

Fig. 7 is a scanning electron microscope image of the copper nanowire electrode of example 2 after stability test of electrochemical reduction of carbon dioxide in potassium chloride solution.

FIG. 8 is a scanning electron microscope image of the high-index lattice plane copper nanowire electrode material obtained after square wave treatment for 30 minutes.

FIG. 9 is a scanning electron microscope image of the high-index lattice copper nanowire electrode material obtained after square wave treatment for 60 minutes.

FIG. 10 is a scanning electron microscope image of the high-index lattice plane copper nanowire electrode material obtained after square wave treatment for 120 minutes.

Fig. 11 is a graph of faraday efficiency and current density of different reduction products obtained at different potentials when potassium chloride solution is used as electrolyte in electrochemical reduction of carbon dioxide for the high-index lattice copper nanowire electrode material obtained after square wave treatment for 30 minutes in example 3, 11a is a graph of faraday efficiency of different reduction products, and 11b is a graph of current density.

Fig. 12 is a graph of faraday efficiency and current density of different reduction products obtained at different potentials when potassium chloride solution is used as electrolyte in electrochemical reduction of carbon dioxide in the high-index lattice copper nanowire electrode material obtained after square wave treatment for 60 minutes in example 3, where 12a is a graph of faraday efficiency of different reduction products and 12b is a graph of current density.

Fig. 13 is a graph of faraday efficiency and current density of different reduction products obtained at different potentials when potassium chloride solution is used as electrolyte in electrochemical reduction of carbon dioxide for the high-index lattice copper nanowire electrode material obtained after 120 minutes of square wave treatment in example 3, 13a is a graph of faraday efficiency of different reduction products, and 13b is a graph of current density.

Detailed Description

The present invention will be further described with reference to the following embodiments.