CN110607535B - Electrode, preparation method thereof and electrolysis device - Google Patents
Electrode, preparation method thereof and electrolysis device Download PDFInfo
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- CN110607535B CN110607535B CN201810622469.7A CN201810622469A CN110607535B CN 110607535 B CN110607535 B CN 110607535B CN 201810622469 A CN201810622469 A CN 201810622469A CN 110607535 B CN110607535 B CN 110607535B
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
- C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
- C25B11/031—Porous electrodes
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
- C25B11/093—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one noble metal or noble metal oxide and at least one non-noble metal oxide
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- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/20—Processes
- C25B3/25—Reduction
Abstract
The embodiment of the invention provides an electrode, a preparation method thereof and an electrolysis device, relates to the technical field of electrode materials, and can improve the Faraday efficiency of a target product in a catalytic conversion reaction. The preparation method of the electrode comprises the following steps: carrying out first heat treatment on the foam metal to form a metal oxide nanowire layer on the surface of the foam metal; heating a reaction system consisting of a reducing agent, a strong alkaline solution and the foam metal subjected to the first heat treatment so as to reduce part of the metal oxide nanowires on the surface of the metal oxide nanowire layer into metal sub-oxide nanowires; and immersing the foam metal subjected to the heating treatment into a noble metal compound solution so as to enable the noble metal compound solution to react with the metal sub-oxide nanowires to generate a noble metal simple substance. Is used for preparing the electrode and an electrolytic device comprising the electrode.
Description
Technical Field
The invention relates to the technical field of electrocatalysis, in particular to a preparation method of an electrode, the electrode and an electrolysis device.
Background
The main advantages of the electrocatalytic reduction technology are: no need of consuming chemical reagents, versatility, high energy efficiency, environmental compatibility, easy control, etc. The key component in the electrocatalytic reduction technology, which determines the high or low electrocatalytic activity, is the working electrode, which is the "heart" of the electrochemical catalytic system. Such as in CO2In the electrocatalytic reduction of (2), the electrode material pair increases CO2Catalytic conversion efficiency is of critical importance.
In the existing electrode material, the carbon-based material with a microporous structure has a high specific surface area, but the electrocatalytic performance is not obviously improved; and the carbon-based material has the problems of complicated preparation steps, complex process, harsh preparation conditions, high cost and the like, so that the further application of the carbon-based material in the field of electrocatalysis (especially in the field of carbon dioxide electrocatalysis) is limited. The copper-based material has relatively good electrocatalytic performance, and particularly has the characteristics of low price, easy obtainment, wide working temperature range, mature production process, environmental friendliness and the like, so the copper-based material is mainly adopted when the electrode is manufactured at present.
But the electrocatalytic properties of electrocatalytic materials based on pure copper-based materials are not ideal. In order to improve the electrocatalytic performance of electrocatalytic materials based on copper-based materials, the current research direction for copper-based materials mainly focuses on two aspects:
on one hand, the specific surface area of the copper-based material is increased, and the contact area of the electrode material and the electrolyte in the electrocatalytic reaction is increased, so that the electrocatalytic performance of the copper-based material is improved. On the other hand, the copper-based material is modified by using the noble metal nano-particles. When the electrode is used in electrocatalysis reaction, the electrocatalysis reaction product is adsorbed on the surface of the electrode to cause pollution and passivation of the surface of the electrode, or the physical and chemical changes of the surface of the electrode caused by long-term use can cause the catalytic activity, catalytic reproducibility and stability of the electrode to be greatly reduced, and the pollution and passivation of the surface of the electrode can be effectively reduced by modifying the copper-based material by using the noble metal nano particles, so that the physical and chemical changes of the surface of the electrode are reduced. Meanwhile, the electrocatalytic performance of the electrode can be further improved by the synergistic effect generated by the noble metal nano particles and the copper-based material.
The copper-based material is modified by the noble metal nano-particles, so that the material with a multilayer structure and a high specific surface area can be obtained. However, since such a material does not have self-supporting properties, it is necessary to add an auxiliary material such as a binder or activated carbon in the process of manufacturing an electrode. The preparation method has influence on the specific surface of the formed electrode, reduces the effective contact area of an active material in the electrode and an electrolyte, and also causes the formed electrode material to have larger contact resistance, so that when the electrode obtained by the preparation method in the prior art is applied to an electrocatalytic reaction, the further improvement of the Faraday efficiency of a target product in the catalytic reaction is limited.
Disclosure of Invention
In view of the above, to solve the problems in the prior art and overcome the defects in the prior art, embodiments of the present invention provide an electrode, a preparation method thereof, and an electrolysis apparatus, where the electrode obtained by the preparation method has a self-supporting property and a large specific surface area, and when applied to an electrocatalytic reaction, the faradaic efficiency of a target product in the catalytic reaction can be improved.
In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:
in one aspect, an embodiment of the present invention provides a method for preparing an electrode, where the method includes: carrying out first heat treatment on the foam metal to form a metal oxide nanowire layer on the surface of the foam metal; heating a reaction system consisting of a reducing agent, a strong alkaline solution and the foam metal subjected to the first heat treatment so as to reduce part of the metal oxide nanowires on the surface of the metal oxide nanowire layer into metal sub-oxide nanowires; and immersing the foam metal subjected to the heating treatment into a noble metal compound solution so as to enable the noble metal compound solution to react with the metal sub-oxide nanowires to generate a noble metal simple substance.
Optionally, the preparation method further comprises: and carrying out secondary heat treatment on the foam metal with the formed noble metal simple substance in an inert atmosphere so as to decompose compounds in the compound solution of the noble metal remained on the surface to form the noble metal simple substance.
Optionally, the temperature of the second heat treatment is 700-.
Optionally, the temperature of the first heat treatment is 400-700 ℃, and the time is 0.5-3 h.
Optionally, the temperature of the heating treatment is 160-200 ℃, and the time is 3-12 h.
Optionally, the time for immersing the foam metal subjected to the heat treatment into the noble metal compound solution is 1-6 h.
Optionally, the metal foam comprises: copper foam or nickel foam.
Optionally, the compound solution of noble metal comprises: a gold compound solution or a platinum compound solution.
In another aspect, an embodiment of the present invention further provides an electrode, including: a support layer composed of a foamed metal; the electrode further comprises: a compound nanowire layer of metal and oxygen formed on the surface of the support layer; and the noble metal simple substance is formed on the surface of the compound nanowire layer of the metal and the oxygen.
Optionally, the metal and oxygen compound nanowire layer comprises:
a layer of metal oxide nanowires; or, a metal oxide nanowire layer and a metal sub-oxide nanowire layer formed on the surface of the metal oxide nanowire layer.
Optionally, the metal foam comprises: copper foam or nickel foam.
Optionally, the noble metal simple substance includes: gold or platinum.
In another aspect, the embodiment of the invention further provides an electrolysis device, which includes the above electrode.
Based on this, in the preparation method of the electrode provided in the embodiment of the present invention, the foamed metal is used as a current collector and a support, and a high-temperature pre-oxidation, a hydrothermal reaction (for example, a solvothermal reaction), and a redox reaction are combined to obtain a ternary composite material, where the ternary composite material includes the foamed metal, a metal and oxygen compound nanowire layer formed layer by layer on the foamed metal, and a precious metal simple substance. The foam metal has a certain self-supporting characteristic, so that when the foam metal is applied to an electrocatalytic reaction, a current collector or a support body is not required to be additionally arranged, and the foam metal can be used as the current collector or the support body; in addition, because a large number of holes or pore structures are distributed in the foam metal, the foam metal has a high specific surface area, so that the electron collection and transfer rate in the electrochemical catalysis process can be accelerated, the contact area of an electrode material and electrolyte can be increased, the diffusion rate of the electrolyte can be increased, more active sites can be provided for the electrocatalysis process, and the catalysis efficiency of the electrode can be improved. The metal and oxygen compound nanowire layer naturally grows on the surface of the foam metal by utilizing pre-oxidation reaction, and auxiliary materials such as a binder and the like do not need to be additionally added, so that the larger specific surface area of the foam metal is not influenced. The noble metal simple substance formed on the surface of the composite material can modify the catalytic performance of the foam metal, so that a synergistic effect is generated between the noble metal simple substance and the foam metal, and the Faraday efficiency of the obtained target product of the composite electrode applied to the electrocatalysis reaction is further improved, namely the percentage of an actual product and a theoretical product.
In addition, compared with the existing preparation method, the preparation method of the electrode provided by the embodiment of the invention has the advantages of simple preparation process, shorter flow and lower equipment dependence, and is more suitable for industrial large-scale production.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for manufacturing an electrode according to an embodiment of the present invention;
FIG. 2 is a Scanning Electronic Microscope (SEM) photograph of an electrode according to an embodiment of the present invention;
fig. 3 is an X-ray diffraction (XRD) spectrum of an electrode and a copper foam provided in an embodiment of the present invention;
fig. 4 shows electrocatalytic efficiency at different time points when an electrode according to an embodiment of the present invention is applied to an electrocatalytic reaction.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. It is to be understood that all starting materials for the present invention, without particular limitation as to their source, are either commercially available or may be prepared by conventional methods well known to those skilled in the art, and that the solvents referred to are ionic water unless otherwise specified. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a preparation method of an electrode, as shown in fig. 1, the preparation method comprises the following steps:
s101, carrying out first heat treatment on the foam metal to form a metal oxide nanowire layer on the surface of the foam metal;
s102, heating a reaction system formed by a reducing agent, a strong alkaline solution and foam metal subjected to primary heat treatment to reduce part of the metal oxide nanowires on the surface of the metal oxide nanowire layer into metal sub-oxide nanowires;
s103, immersing the heated foam metal into a noble metal compound solution to enable the noble metal compound solution to react with the metal sub-oxide nanowires to generate a noble metal simple substance.
First, in S101, the metal foam is a characteristic metal material containing foam pores, and has characteristics such as self-supporting property and large specific surface area.
It can be understood that since the above S101 is to form a metal oxide nanowire layer on the surface of the metal foam after the first heat treatment of the metal foam. Therefore, the first heat treatment is performed in an atmosphere including oxygen (air may be exemplified), that is, a high-temperature pre-oxidation treatment is performed on the metal foam.
The principle of the metal oxide nanowire layer formation in S101 is as follows:
under the conditions of high temperature and oxygen, metal ions in the foam metal diffuse to the surface through the grain boundary and then are subjected to the action of high temperature to continue diffusing along the grain boundary between the surface grains of the foam metal, namely, nucleation is carried out at the surface grain boundary, and the metal ions react with the oxygen to generate metal oxide. The metal ions inside continuously diffuse along the grain boundaries between the nucleated crystal grains, so that metal oxides grow into nanowires along the grain boundaries, the nanowires are formed on the surface of the foamed metal in a large amount, a metal oxide nanowire layer is formed, and a first-level composite structure of the foamed metal/metal oxide nanowire layer is formed, which is expressed as M/MO below, wherein M represents a metal element of the foamed metal.
Second, in step S102, the reaction system including the reducing agent, the strongly basic solution, and the metal foam subjected to the first heat treatment is subjected to a heat treatment, and the amount of the solution is required to completely immerse the metal foam.
In the process, the reducing agent is a weak reducing agent, and a part of the metal oxide nanowires on the surface of the foam metal can be reduced in a strong alkaline solution to obtain the metal sub-oxide nanowires, so that a second-stage composite structure of the foam metal/metal oxide nanowire layer/metal sub-oxide nanowires is formed.
The structural example can be expressed as M/MxAnd O, wherein the subscript "x" represents the overall ratio of metal elements to oxygen elements in the metal oxides and metal sub-oxides.
It can be understood that if the metal oxide nanowires are all reduced by the strong reducing agent, the morphology of the metal oxide nanowires on the surface of the metal foam is easily damaged, so that the metal oxide nanowire layer on the surface of the metal foam collapses, and it is difficult to form the above-mentioned composite structure of metal foam/metal oxide nanowire layer/metal sub-oxide nanowires.
Therefore, the metal oxide nanowires are partially reduced to metal sub-oxide nanowires by a weak reducing agent in S102.
Here, the strongly alkaline solution generally means a substance which causes the color of a specific indicator to change (e.g., a purple litmus solution turns blue, a colorless phenolphthalein solution turns red, etc.), and has a pH value of more than 12 in a standard case (concentration of 0.1 mol/L)). The strong base in the strong alkaline solution can be completely ionized in the aqueous solution, and the ionized anions are all hydroxide ions and react with acid to form salt and water.
Thirdly, in S103, the reductive metal sub-oxide and the oxidative noble metal ion in the noble metal compound solution undergo an oxidation-reduction reaction to generate a noble metal simple substance.
It can be understood that when all the metal sub-oxide nanowires react with the noble metal ions, the generated noble metal simple substance is attached to the surface of the metal oxide nanowires, thereby forming a third-level composite structure of the metal foam/metal oxide nanowire layer/noble metal.
The structural example can be expressed as M/MxO/Y, wherein Y represents a noble metal element; in this case, MxO represents only a metal oxide.
When part of the metal sub-oxide nanowires react with the noble metal ions, the generated noble metal simple substances are attached to the surfaces of the metal oxide nanowires and the metal sub-oxide nanowires formed on the surfaces of the metal oxide nanowires, so that another third-level composite structure of a foam metal/metal oxide nanowire layer and the metal sub-oxide nanowires/noble metals is formed.
The structural example can be expressed as M/MxO/Y, wherein Y represents a noble metal element; in this case, MxO represents a metal oxide or a metal sub-oxide.
Based on this, in the preparation method of the electrode provided in the embodiment of the present invention, the foamed metal is used as a current collector and a support, and a high-temperature pre-oxidation, a hydrothermal reaction (for example, a solvothermal reaction), and a redox reaction are combined to obtain a ternary composite material, where the ternary composite material includes the foamed metal, a metal and oxygen compound nanowire layer formed layer by layer on the foamed metal, and a noble metal simple substance, which may be represented as M/M in an examplexAnd O/Y. The foam metal has a certain self-supporting characteristic, so that when the foam metal is applied to an electrocatalytic reaction, a current collector or a support body is not required to be additionally arranged, and the foam metal can be used as the current collector or the support body; moreover, the foam metal has a high content of holes or pore structures distributed thereinThe specific surface area of the electrode can not only accelerate the electron collection and transfer rate in the electrochemical catalysis process, but also improve the contact area of the electrode material and the electrolyte and increase the diffusion rate of the electrolyte, so that more active sites are provided for the electrocatalysis process, and the catalysis efficiency of the electrode can be improved. The metal and oxygen compound nanowire layer naturally grows on the surface of the foam metal by utilizing pre-oxidation reaction, and auxiliary materials such as a binder and the like do not need to be additionally added, so that the larger specific surface area of the foam metal is not influenced. The noble metal simple substance formed on the surface of the composite material can modify the catalytic performance of the foam metal, so that a synergistic effect is generated between the noble metal simple substance and the foam metal, and the Faraday efficiency of the obtained target product of the composite electrode applied to the electrocatalysis reaction is further improved, namely the percentage of an actual product and a theoretical product.
In addition, compared with the existing preparation method, the preparation method of the electrode provided by the embodiment of the invention has the advantages of simple preparation process, shorter flow and lower equipment dependence, and is more suitable for industrial large-scale production.
In order to improve the degree of forming a metal oxide nanowire layer on the surface of the metal foam in S101, before S101, the method for preparing the electrode according to the embodiment of the present invention further includes the following steps:
the metal foam is pre-cleaned to remove surface impurities and oxide layers.
For example, the foam metal can be immersed into a dilute sulfuric acid or dilute hydrochloric acid solution with the concentration of less than 2mol/L to remove impurities and oxide layers on the surface of the foam metal by using the corrosiveness of dilute acid.
Moreover, the pre-cleaning process may also utilize ultrasonic oscillation to assist in cleaning to speed up the cleaning process and/or improve the degree of cleaning. An example of the time of the ultrasonic oscillation may be 5 min.
Further, before S102, the method for preparing the electrode according to the embodiment of the present invention further includes the following steps:
and sequentially cleaning and drying the foam metal/metal oxide nanowire layer obtained in the step S101.
For example, the product may be washed with deionized water and then dried at 60-80 ℃ for 10h to prevent the metal sub-oxide formed by the above-mentioned S101 from being oxidized again, and the drying is performed under vacuum.
Further, considering that the noble metal compound in the noble metal compound solution may not be completely reacted, some noble metal compound may be attached to the surface of the ternary composite material. Therefore, in order to increase the content of the elemental noble metal supported on the surface of the ternary composite material prepared through steps S101 to S103 and increase the utilization rate of the solution of the noble metal compound, after step S103, the preparation method provided by the embodiment of the present invention further includes the following steps:
and carrying out secondary heat treatment on the foam metal with the formed noble metal simple substance in an inert atmosphere so as to decompose compounds in the compound solution of the noble metal remained on the surface to form the noble metal simple substance.
Wherein, the temperature of the second heat treatment is 700-.
The second heat treatment is performed in an inert atmosphere in order to prevent the foamed metal and the noble metal from being oxidized to embrittle the ternary composite material formed and destroy the self-supporting skeleton and the nanowire layer.
The selection of the inert atmosphere can continue to use the related art, and the embodiment of the invention will not be described in detail.
To further illustrate the preparation method provided by the embodiment of the present invention, the reaction conditions such as solution concentration, reaction temperature, reaction time, etc. involved in the above steps are specifically described below:
in the above S101, the temperature of the first heat treatment may be 400-700 ℃ for 0.5-3 h.
In the temperature and reaction time range, on one hand, the obtained material still keeps a self-supporting framework of the foam metal, the material is not embrittled due to complete oxidation of the foam metal, and on the other hand, the formed metal oxide can keep a uniform nanowire shape.
The metal foam may be copper foam or nickel foam. Because the preparation cost of the copper foam is lower than that of the nickel foam, and the conductivity is better, the copper foam is usually selected as a raw material to prepare the electrode.
In the above S102, the temperature of the heating treatment may be, for example, 160-;
the reducing agent can be at least one of glucose, urea, melamine and dicyandiamide, and the concentration is 10-50 mg/ml;
the strongly alkaline solution may be exemplified by a potassium hydroxide solution and/or a sodium hydroxide solution, with a concentration of less than 200 mg/ml.
In the above step S103, the foam metal after the heating treatment is immersed in the noble metal compound solution, so that the noble metal compound solution reacts with the metal sub-oxide nanowire to generate a noble metal simple substance, and since the metal sub-ions have strong reducibility and the noble metal ions have strong oxidizability, the process can be performed at room temperature for 1 to 6 hours.
Here, the "room temperature" is also referred to as normal temperature or ordinary temperature. Generally, room temperature has 3 ranges of definition, namely: firstly, 23 +/-2 ℃; the temperature is 25 +/-5 ℃; and c, performing purification at 20 +/-5 ℃.
The compound solution of the noble metal in S103 may be a gold compound solution or a platinum compound solution, and the concentration may be exemplified by 1 to 25 mmol/L.
Wherein the gold compound solution comprises chloroauric acid solution, AuCl solution and AuCl3At least one of the solutions.
On the basis, the embodiment of the invention also provides an electrode obtained by the preparation method, and the electrode comprises foamed metal; the electrode further comprises: a compound nanowire layer of metal and oxygen formed on the surface of the metal foam; the noble metal simple substance is formed on the surface of the compound nanowire layer of the metal and the oxygen.
Among them, examples of the above-mentioned compound nanowire layer of metal and oxygen may include: a layer of metal oxide nanowires; or, a metal oxide nanowire layer and a metal sub-oxide nanowire layer formed on the surface of the metal oxide nanowire layer.
The foam metal can be foam copper or foam nickel; the simple noble metal can be gold or platinum.
When the foam metal is foam copper (Cu foam) and the noble metal simple substance is gold (Au), the prepared electrode is a composite material formed by three elements of copper, oxygen and gold, and the structure of the three-element composite material is specifically as follows: a compound nanowire layer of copper and oxygen is formed on the surface of the copper foam; gold simple substance is formed on the surface of the nanowire layer.
Here, an example of the compound nanowire layer of copper and oxygen may be a copper oxide nanowire layer, or a copper oxide nanowire layer and a cuprous oxide nanowire layer formed on the surface of the copper oxide nanowire layer.
The ternary composite material can be expressed as Cu foam/CuxO/Au。
On the basis, the embodiment of the invention also provides an electrolysis device which comprises the electrode.
Illustratively, the electrolysis device (e.g., an electrolysis cell) may be of an H-shaped configuration. In the H-shaped electrolytic device, a cation exchange membrane is used as a diaphragm to divide the electrolytic device into a cathode chamber and an anode chamber, carbon dioxide gas can be introduced from the bottom of the solution in the cathode chamber, and the electrolyte is 0.1M sodium bicarbonate aqueous solution.
For further illustration of the present invention, the following will describe in detail a method for preparing an electrode, an electrode and an electrolytic device provided by the present invention by using copper foam as a raw material in combination with specific examples, reagents used in the following examples are commercially available or prepared according to conventional methods well known to those skilled in the art, and the related solutions are ionized water unless otherwise specified, but it should be understood that the examples are performed on the premise of the technical solution of the present invention, and that the detailed embodiments and specific procedures are given only for further illustration of the features and advantages of the present invention, not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
Example 1
Step 1: pre-cleaning the surface of the foam copper to remove surface impurities and an oxide layer;
for example, the copper foam may be immersed in 1M (i.e., 1mol/L) dilute sulfuric acid, sonicated for 5min, and then rinsed with deionized water and dried.
It should be noted here that the copper foam size may be 1.5cm by 3cm in order to produce an electrode of suitable size.
Step 2: placing the foamy copper in a heating device, and carrying out first heat treatment at 550 ℃ for 3 h;
for example, the copper foam may be placed in a tube furnace and heat treated in air communication.
And step 3: adding a glucose solution and a strong base solution into a reaction container, wherein the concentration of the glucose solution is 50mg/ml, and the concentration of the strong base solution is 100mg/ml, uniformly mixing, putting the sample prepared in the step 2 into the solution, and heating to perform hydrothermal reaction on the reaction system, wherein the treatment temperature is 180 ℃, and the treatment time is 3 hours;
for example, glucose, solid potassium hydroxide and 12-18 mL of deionized water can be added into 20mL of polytetrafluoroethylene core to perform hydrothermal reaction on the materials, wherein the concentration of glucose is 50mg/mL, the concentration of a potassium hydroxide solution is 100mg/mL, after uniform mixing, the sample prepared in the step 2 is placed into the solution to be subjected to heating treatment, the treatment temperature is 180 ℃, and the treatment time is 3 hours.
Here, in the hydrothermal reaction, the reaction system is usually filled at 3/4 in the volume of the reaction vessel in order to leave a certain space margin in the sealed reaction vessel (for example, polytetrafluoroethylene core). Therefore, when glucose and solid potassium hydroxide are added, the specific required addition amount can be calculated according to the respective concentrations, and no specific calculation is made here.
And 4, step 4: cleaning and drying the sample prepared in the step 3;
illustratively, the sample prepared in step 3 is washed with deionized water and then dried in an oven at 80 ℃.
And 5: reacting the sample obtained in the step 4 with a chloroauric acid solution for 1h, wherein the concentration of the chloroauric acid solution is 10 mmol/L;
step 6: cleaning the sample obtained in the step 5 by using deionized water, taking out and placing in an oven for drying at 80 ℃;
and 7: and (4) placing the sample obtained in the step (6) in a heating device, and carrying out secondary heat treatment at 900 ℃ for 5 min.
For example, the sample obtained in step 6 may be placed in a tube furnace and subjected to a second heat treatment at 900 ℃ for 5min, so as to prevent the sample from being oxidized and embrittled and breaking the self-supporting structure, and the reaction process needs to be carried out in an inert atmosphere.
The electrode material prepared by the embodiment has high specific surface area and abundant interconnected hierarchical pore structures, so that the electrode material has selectivity and stability in the electrocatalytic conversion process.
The following tests show that the electrode material is in CO2The experiment adopts a three-electrode system, the working electrode is the electrode prepared in example 1, and the reference electrode and the counter electrode respectively adopt a saturated calomel electrode and a platinum wire electrode. Measuring the presence of CO in the electrode material2In the electrocatalytic process, the concentration is 10mA/cm2At current density of (3), CO2The faradaic efficiency of conversion to CO can reach 67%.
Example 2:
step 1: pre-cleaning the surface of the foam copper to remove surface impurities and an oxide layer;
step 2: placing the foamy copper in a heating device, and carrying out first heat treatment at 400 ℃ for 1 h;
and step 3: adding a glucose solution and a strong base solution into a reaction container, wherein the concentration of the glucose solution is 60mg/ml, and the concentration of the strong base solution is 100mg/ml, uniformly mixing, putting the sample prepared in the step 2 into the solution, and heating to perform hydrothermal reaction on the reaction system, wherein the treatment temperature is 160 ℃, and the treatment time is 3 hours;
and 4, step 4: cleaning and drying the sample prepared in the step 3;
and 5: reacting the sample obtained in the step 4 with chloroauric acid for 1h, wherein the concentration of the chloroauric acid is 10 mmol/L;
step 6: washing the sample obtained in the step 5 with deionized water, taking out and placing in an oven for drying at 80 ℃;
and 7: and (4) placing the sample obtained in the step (6) in a heating device, and carrying out second heat treatment at the treatment temperature of 1000 ℃ for 5 min.
The electrode made in this example is in CO2In the electrocatalytic process, the concentration is 10mA/cm2At current density of (3), CO2The faradaic efficiency of conversion to CO can reach 40%.
Example 3
Step 1: pre-cleaning the surface of the foam copper to remove surface impurities and an oxide layer;
step 2: placing the foamy copper in a heating device, and carrying out first heat treatment at the temperature of 700 ℃ for 2 h;
and step 3: adding a glucose solution and a strong base solution into a reaction container, wherein the concentration of the glucose solution is 10mg/ml, and the concentration of the strong base solution is 100mg/ml, uniformly mixing, putting the sample prepared in the step 2 into the solution, and heating to perform hydrothermal reaction on the reaction system, wherein the treatment temperature is 190 ℃ and the treatment time is 2 hours;
and 4, step 4: cleaning and drying the sample prepared in the step 3;
and 5: reacting the sample obtained in the step 4 with chloroauric acid for 1h, wherein the concentration of the chloroauric acid is 25 mmol/L;
step 6: washing the sample obtained in the step 5 with deionized water, taking out and placing in an oven for drying at 80 ℃;
and 7: and (4) placing the sample obtained in the step (6) in a heating device, and carrying out second heat treatment at the treatment temperature of 800 ℃ for 10 min.
The electrode material obtained in this example was in CO2ElectrocatalysisDuring the chemical conversion, the concentration is 10mA/cm2At current density of (3), CO2The faradaic efficiency of conversion to CO can reach 50%.
Taking example 1 as an example, the morphology of the electrode synthesized by the above preparation process is shown in fig. 2, and it can be seen from fig. 2 that the surface of the electrode material has a nanowire layer formed by abundant nanowires, has a high specific surface area, and has a rich and interconnected multilevel pore structure.
Fig. 3 is a comparison of phase (XRD) patterns of copper foam (Cu foam) and the electrode synthesized by example 1, and it can be seen from the comparison of the curves in fig. 3 that the resulting electrode material is a ternary composite material.
The electrocatalytic efficiency of the electrode material prepared in example 1 at different time points is experimentally tested, and a curve as shown in fig. 4 can be obtained, and it can be known that the electrode material can achieve corresponding efficiency at different time points when applied to electrocatalytic reaction.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (7)
1. A method of making an electrode, the method comprising:
carrying out first heat treatment on the foam metal to form a metal oxide nanowire layer on the surface of the foam metal;
heating a reaction system consisting of a reducing agent, a strong alkaline solution and the foam metal subjected to the first heat treatment so as to reduce part of the metal oxide nanowires on the surface of the metal oxide nanowire layer into metal sub-oxide nanowires;
immersing the foam metal subjected to the heating treatment into a noble metal compound solution so as to enable the noble metal compound solution to react with the metal sub-oxide nanowires to generate a noble metal simple substance;
and carrying out secondary heat treatment on the foam metal with the formed noble metal simple substance in an inert atmosphere so as to decompose compounds in the compound solution of the noble metal remained on the surface to form the noble metal simple substance.
2. The method as claimed in claim 1, wherein the second heat treatment is performed at a temperature of 700 ℃ to 1000 ℃ for 5-20 min.
3. The method as claimed in claim 1, wherein the first heat treatment is performed at 400-700 ℃ for 0.5-3 h.
4. The method as claimed in claim 1, wherein the temperature of the heating treatment is 160-200 ℃ and the time is 3-12 h.
5. The method for producing an electrode according to claim 1, wherein the time for immersing the foam metal subjected to the heat treatment in a noble metal compound solution is 1 to 6 hours.
6. The method of claim 1, wherein the metal foam comprises: copper foam or nickel foam.
7. The method for producing an electrode according to claim 1, wherein the noble metal compound solution includes: a gold compound solution or a platinum compound solution.
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