CN113502497B - Electrocatalyst for regulating and controlling performance of low-temperature plasma and preparation method and application thereof - Google Patents

Electrocatalyst for regulating and controlling performance of low-temperature plasma and preparation method and application thereof Download PDF

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CN113502497B
CN113502497B CN202110639166.8A CN202110639166A CN113502497B CN 113502497 B CN113502497 B CN 113502497B CN 202110639166 A CN202110639166 A CN 202110639166A CN 113502497 B CN113502497 B CN 113502497B
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electrocatalyst
temperature plasma
copper
nitrate
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CN113502497A (en
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陈燕
宫志恒
何祖韵
钟文烨
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South China University of Technology SCUT
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    • 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
    • C25B11/052—Electrodes comprising one or more electrocatalytic coatings on a substrate
    • 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
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
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    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
    • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
    • C25B11/065—Carbon
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
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    • 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
    • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
    • C25B11/077—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the compound being a non-noble metal oxide
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Abstract

The invention discloses an electrocatalyst with low-temperature plasma regulation and control performance, and a preparation method and application thereof. The method comprises the following steps: preparing a copper-based catalyst by a liquid phase deposition method, then treating the surface of the copper-based catalyst by using argon, hydrogen, air or oxygen and the like as reaction atmosphere of a plasma chamber through a low-temperature plasma technology, and introducing unsaturated active sites such as oxygen vacancies, hydroxyl functional groups and the like on the surface of the copper-based catalyst. The low-temperature plasma technology is used for regulating and controlling the performance of the catalyst, the process is simple, the energy consumption is low, no additional chemical reagent is needed to be added, the environment is friendly, and the application prospect is good. The preparation and regulation method of the electrocatalyst is applicable to application of directional reduction of the electrocatalytic nitrate into ammonia, and compared with raw materials, the material regulated and controlled by the plasma has higher current density, faraday efficiency and selectivity of ammonia conversion in the nitrate reduction reaction, and shows more excellent electrocatalytic activity and stability.

Description

Electrocatalyst with low-temperature plasma regulation and control performance and preparation method and application thereof
Technical Field
The invention belongs to the technical field of electrocatalysis materials, and particularly relates to an electrocatalyst with low-temperature plasma regulation and control performance, and a preparation method and application thereof.
Background
Nitrogen is an essential element of all earth ecosystems and human social activities, however, imbalance of nitrogen circulation due to increased nitrate nitrogen content in groundwater and other water bodies caused by human activities has constituted a significant environmental problem affecting the balance of human and ecosystems. In order to avoid the hazards of excess nitrate and to achieve artificial sustainable nitrogen cycles, many remediation technologies have been developed, including biological denitrification, physicochemical removal, and electrocatalytic technologies. Biological denitrification is a mature and common technology at present, is limited by microbial growth, is not suitable for various water bodies, can cause organic substance residue and pathogenic bacteria, and can ensure water quality safety after subsequent strict treatment.
The selective degradation of nitrate by using an electrocatalysis technology is considered to be one of the most effective ways for efficiently treating nitrate pollution in underground water and industrial wastewater. In a sense, the electrocatalytic reduction of nitrate is similar to the microbial denitrification, and the nitrate reduction is achieved by electron transfer, and the electrocatalytic technology has many incomparable advantages: 1. and (4) environmental friendliness. Carbon sources and chemical reagents do not need to be additionally added, and no toxic by-products and pathogenic bacteria residues are generated, so that secondary environmental pollution is avoided; 2. high selectivity. Through the selection of current, voltage and electrodes, the high-efficiency selectivity of reaction products can be realized, and nitrate can be selectively reduced into high value-added product ammonia; 3. and (4) economy. The power provided by renewable energy sources (such as solar energy, wind energy and the like) can be effectively utilized, the power cost is reduced, and the operation and maintenance cost is lower; 4. and flexibility and controllability. The electrochemical reduction can be carried out in a small reactor at normal temperature and normal pressure, large-scale equipment is not needed, the occupied area is small, the automation is easy, and the installation and the operation are convenient and flexible. Therefore, the reduction and degradation of the nitrate are realized by utilizing the electrocatalysis technology, the reasonable optimization of nitrogen circulation can be realized while the pollution of the nitrate in the water body is treated, the driving of fossil fuels is reduced, and the sustainable development is promoted.
The electrocatalyst is the key of electrochemical reduction reaction, and the development of a high-performance and high-stability catalyst capable of realizing nitrate degradation and product selectivity regulation is an urgent problem to be solved. Research shows that defect engineering is an effective strategy for regulating the surface interface characteristics and the energy band structure of the transition metal oxide electrocatalyst, and the introduction of defects can promote electron transfer and influence the adsorption/desorption energy of active species in the electrocatalytic reaction, thereby effectively improving the electrocatalytic activity of the catalyst. At present, the electrochemical reduction of nitrate still has the problems of low conversion rate, low current efficiency, strong hydrogen evolution reaction competitiveness, poor selectivity to ammonia, high concentration of a byproduct nitrite and the like (Liu, J.X., richards, D., singh, N).&Goldsmith,B.R.Activity and Selectivity Trends in Electrocatalytic Nitrate Reduction on Transition Metals.ACS Catal.2019,9,7052–7064.；Shih,Y.-J.,Wu,Z.-L.,Lin,C.-Y.,Huang,Y.-H.&Huang,C.-P.Manipulating the crystalline morphology and facet orientation of copper and copper-palladium nanocatalysts supported on stainless steel mesh with the aid of cationic surfactant to improve the electrochemical reduction of nitrate and N 2 selection, appl, camera, b environ, 2020,273, 119053), and reasonable control of the performance of the cathode material is the key to future development.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide an electrocatalyst with low-temperature plasma regulation and control performance, and a preparation method and application thereof.
The invention aims to provide a method for regulating and controlling the performance of an electrocatalyst based on a low-temperature plasma technology.
The invention also aims to provide a preparation method for preparing the copper-based oxide electrocatalyst and the electrode based on the low-temperature plasma technology.
It is a further object of the present invention to provide the use of the above electrocatalyst for electrocatalytic reduction of nitrate.
The purpose of the invention is realized by at least one of the following technical solutions.
The method comprises the steps of preparing the copper-based catalyst by a liquid phase deposition method, then using argon, hydrogen, air or oxygen and the like as discharge gas of a plasma cavity, carrying out surface treatment on the copper-based catalyst by a low-temperature plasma technology, and introducing oxygen defects on the surface of the copper-based catalyst. The electrode is prepared from the material treated by the plasma, and the electrode is applied to the cathode of the nitrate electrocatalytic reduction reaction, so that the electrocatalytic activity, the Faraday efficiency and the stability of the electrode can be effectively improved.
The preparation method of the electrocatalyst with the low-temperature plasma regulation and control performance, provided by the invention, comprises the following steps:
(1) Preparation of copper-based catalysts by liquid phase deposition: adding a copper salt and a surfactant into deionized water, uniformly mixing to obtain a mixed solution, adjusting the pH of the mixed solution to be alkaline, then adding a reducing agent, heating under a stirring state to perform a heating reaction to obtain a copper-based catalyst;
(2) Plasma technology treatment: grinding the copper-based catalyst in the step (1) into powder, uniformly coating the powder on a platform (preferably corundum pieces), transferring the powder into a reactor (a low-temperature plasma chamber), introducing reaction gas, and performing plasma treatment to obtain the electrocatalyst with the low-temperature plasma regulation and control performance.
Further, the copper salt in the step (1) is more than one of copper sulfate, copper nitrate, copper chloride and the like; the surfactant in the step (1) is one of polyethylene glycol, polyvinylpyrrolidone and the like; the reducing agent in the step (1) is more than one of glucose, ascorbic acid, sodium borohydride and the like.
Further, in the step (1), according to the parts by mass,
10-50 parts of copper salt;
0-120 parts of a surfactant;
1000 parts of water;
5-20 parts of a reducing agent.
Further, in the step (1), the pH value of the mixed solution is adjusted to 9.0-12.0;
preferably, in step (1), the pH of the mixed solution may be adjusted by using NaOH solution or KOH solution.
Further, the heating reaction temperature in the step (1) is 20-60 ℃, and the heating reaction time is 30-420min.
Preferably, the temperature of the heating reaction in step (1) is 60 ℃.
Further, the reaction gas in the step (2) is more than one of argon, hydrogen, air, oxygen and the like;
further, in the step (2), after the plasma is introduced into the reactor, the pressure in the reactor is 1-30Pa.
Preferably, before the reaction gas is introduced in step (2), the reactor is evacuated for more than 20 minutes to ensure that no other gas remains.
Further, the radio frequency power of the plasma treatment in the step (2) is 50-450W, the plasma treatment time is 1-100min, and the plasma treatment temperature is 20-60 ℃.
In the step (2), after the plasma treatment, the obtained catalyst is a cuprous oxide catalyst material rich in oxygen vacancies and surface hydroxyls.
The invention provides an electrocatalyst with low-temperature plasma regulation and control performance, which is prepared by the preparation method.
The application of the electrocatalyst with the low-temperature plasma regulation and control performance in the electrocatalysis reduction of nitrate comprises the following steps:
(1) Preparing an electrode material: adding the electrocatalyst with the low-temperature plasma regulation and control performance into a solvent, uniformly dispersing to obtain catalyst ink, and then dripping the catalyst ink on a conductive current collector to obtain an electrode material containing the catalyst;
(2) And (2) carrying out nitrate electrocatalytic reduction reaction by using the electrode material containing the catalyst in the step (1) as a working electrode, platinum as a counter electrode, ag/AgCl as a reference electrode and nitrate-containing solution as electrolyte.
Further, the solvent in the step (1) is a mixture of isopropanol, ultrapure water and a Nifion solution, and the volume ratio of the isopropanol, the ultrapure water and the Nifion solution is 45; the concentration of the Nifion solution is 5 +/-0.5 wt%;
preferably, the concentration of the Nifion solution is 5wt%.
Further, the mass concentration of the electrocatalyst with the low-temperature plasma regulation and control performance in the step (1) in the solvent is 5-50mg/mL.
Further, the conductive current collector in the step (1) is more than one of carbon cloth, carbon paper, nickel foam, copper foam, FTO conductive glass and the like;
further, the uniform dispersion mode in the step (1) is ultrasonic dispersion treatment, and the time of the ultrasonic dispersion treatment is 0.5-3h.
Further, the nitrate radical-containing solution in the step (2) is NaNO 3 Solutions or KNO 3 A solution;
further, the voltage of the electrocatalytic reduction treatment in the step (2) is 0.8-1.5V (relative to a saturated Ag/AgCl electrode), and the time of the electrocatalytic reduction treatment is 0.5-9h.
The low-temperature plasma treatment technology has the advantages of simple process, low energy consumption, no need of adding additional chemical reagents, environmental friendliness, flexible and controllable regulation and control process of the material, strong universality and good application prospect, and is expected to become an important technical means for modifying the surfaces of catalysts and semiconductors.
Compared with the raw materials, after the surface of the treated material is modified and defect-controlled, a large number of oxygen vacancies are introduced on the surface of the material, hydroxyl groups are increased, the hydrophilicity is increased, the surface state concentration is improved, the charge transfer of a catalyst/solution interface is effectively promoted, and the electro-catalyst has higher current density, faraday efficiency and ammonia conversion selectivity aiming at the electro-catalytic reduction reaction of the nitrate, and shows more excellent catalytic activity and stability.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) In the preparation method provided by the invention, the low-temperature plasma technology is used for regulating and controlling the copper-based oxide, the process operation is simple, the preparation period is short, the material cost is low, the energy consumption is low, other chemical reagents are not introduced, and the secondary pollution is avoided.
(2) The preparation method provided by the invention has the advantages of wide application range, realization of large-scale production of used raw materials and conductive current collectors, wide source and low price.
(3) In the preparation method provided by the invention, the oxygen vacancy concentration, hydroxyl group and the like on the surface of the transition metal oxide material can be easily and reasonably regulated and controlled by controlling the reaction gas atmosphere, the plasma radio frequency power and the treatment time through low-temperature plasma treatment.
(4) In the preparation method provided by the invention, the cuprous oxide material regulated and controlled by the low-temperature plasma technology has higher electrochemical reduction activity on the electro-catalytic reduction reaction of nitrate, high Faraday efficiency and high ammonia conversion selectivity, and a hydroxylated amorphous layer is formed on the surface of the cuprous oxide material, so that the cuprous oxide material has better stability.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) image of the copper-based catalyst obtained in step (1) of example 1 before and after low-temperature plasma treatment regulation for 60 min;
FIG. 2 is a High Resolution Transmission Electron Microscope (HRTEM) image of the copper-based catalyst obtained in step (1) of example 1 after being subjected to low temperature plasma treatment for 60 min;
FIG. 3 is an X-ray diffraction (XRD) pattern of the carbon paper supported cuprous oxide catalyst electrode materials Ar-60, ar-40, ar-20 obtained in example 1 and the carbon paper supported cuprous oxide catalyst electrode material Pristine obtained in comparative example 1;
FIG. 4 is an Electron Paramagnetic Resonance (EPR) plot of the carbon paper supported cuprous oxide catalyst electrode material Ar-60 obtained in example 1 and the carbon paper supported cuprous oxide catalyst electrode material Pristine obtained in comparative example 1;
FIG. 5 is the cyclic voltammograms of the carbon paper supported cuprous oxide catalyst electrode materials Ar-60 and Ar-40 obtained in example 1 and the carbon paper supported cuprous oxide catalyst electrode material Prinstine obtained in comparative example 1 for the electroreduction reaction of nitrate;
fig. 6 is a cyclic voltammogram of a hydrogen evolution reaction of the carbon paper supported cuprous oxide catalyst electrode material Ar-60 obtained in example 1;
FIG. 7 is a graph showing the results of the nitrogen species ratios after the nitrate reduction reaction of the carbon paper supported cuprous oxide catalyst electrode materials Ar-60 and Ar-40 obtained in example 1 and the carbon paper supported cuprous oxide catalyst electrode material Pristine obtained in comparative example 1;
FIG. 8 is an electrochemical AC impedance curve of the carbon paper supported cuprous oxide catalyst electrode materials Ar-60, ar-40 obtained in example 1 and the carbon paper supported cuprous oxide catalyst electrode material Pristine obtained in comparative example 1 for nitrate reduction reaction;
FIG. 9 is an X-ray diffraction (XRD) pattern of the carbon paper supported cuprous oxide catalyst electrode materials H-60, H-40, H-20 obtained in example 2 and the carbon paper supported cuprous oxide catalyst electrode material Pristine obtained in comparative example 1.
Detailed Description
The following examples are presented to further illustrate the practice of the invention, but the practice and protection of the invention is not limited thereto. It is noted that the processes described below, if not specifically detailed, are all those that can be realized or understood by those skilled in the art with reference to the prior art. The reagents or apparatus used are not indicated to the manufacturer, and are considered to be conventional products available by commercial purchase.
Example 1
A preparation method of an electrocatalyst with low-temperature plasma regulation and control performance comprises the following steps:
(1) Preparation of cuprous oxide catalyst by liquid phase deposition method: 0.8g of copper salt (CuSO is selected) 4 ) Adding 6g of surfactant (polyethylene glycol or PEG-6000) into 150mL of deionized water, uniformly mixing to obtain a mixed solution, adjusting the pH of the mixed solution to 12.0, adding 0.9g of reducing agent (ascorbic acid), heating under stirring for reaction at 60 ℃ for 6 hours to obtain a copper-based catalyst;
(2) And (3) low-temperature plasma technology treatment: grinding the copper-based catalyst in the step (1) into powder, uniformly coating the powder on a platform (corundum sheet), transferring the powder into a reactor (low-temperature plasma chamber), and introducing argon; and after argon is introduced, performing plasma treatment with the radio frequency power of 180W and the plasma treatment time of 20min, 40min and 60min respectively at the pressure of 20Pa in the low-temperature plasma chamber to obtain the electrocatalyst (copper-based catalyst material rich in oxygen vacancies and surface hydroxyl groups) with the low-temperature plasma regulation and control performance.
(3) Dispersing 10mg of the electrocatalyst with the low-temperature plasma regulation and control performance in 1mL of solvent, and uniformly dispersing by using ultrasonic waves to obtain catalyst ink; the solvent is a mixture of 450 mu L of isopropanol, 450 mu L of ultrapure water and 100 mu L of Nifion solution; the mass percent concentration of the Nifion solution is 5wt%; 80 μ L of the catalyst ink was applied dropwise to carbon paper (1X 1 cm) 2 ) To obtain carbon paper-supported oxyalkyleneThe copper catalyst electrode materials are labeled as Ar-20, ar-40, and Ar-60 (corresponding to plasma treatment times of 20min, 40min, and 60 min).
Comparative example 1
A method of preparing an electrocatalyst, comprising the steps of:
(1) Preparation of cuprous oxide catalyst by liquid phase deposition method: 0.8g of copper salt (CuSO is selected) 4 ) Adding 6g of surfactant (polyethylene glycol or PEG-6000) into 150mL of deionized water, uniformly mixing to obtain a mixed solution, adjusting the pH of the mixed solution to 12.0, adding 0.9g of reducing agent (ascorbic acid), heating under stirring for reaction at 60 ℃ for 6 hours to obtain a copper-based catalyst;
(2) Dispersing 10mg of the copper-based catalyst in 1mL of solvent, and uniformly dispersing by using ultrasonic waves to obtain catalyst ink; the solvent is a mixture of 450 mu L of isopropanol, 450 mu L of ultrapure water and 100 mu L of Nifion solution; the mass percentage concentration of the Nifion solution is 5wt%; 80 μ L of the catalyst ink was applied dropwise to carbon paper (1X 1 cm) 2 ) And finally, obtaining the carbon paper supported cuprous oxide catalyst electrode material, and marking the electrode material as Prinstine.
Example 2
A preparation method of an electrocatalyst with low-temperature hydrogen plasma regulation and control performance comprises the following steps:
(1) Preparation of cuprous oxide catalyst by liquid phase deposition method: 0.8g of copper salt (CuSO is selected) 4 ) Adding 6g of surfactant (polyethylene glycol or PEG-6000) into 150mL of deionized water, uniformly mixing to obtain a mixed solution, adjusting the pH of the mixed solution to 12.0, adding 0.9g of reducing agent (ascorbic acid), heating under stirring for reaction at 60 ℃ for 6 hours to obtain a copper-based catalyst;
(2) And (3) low-temperature plasma technology treatment: and (2) grinding the copper-based catalyst in the step (1) into powder, then uniformly coating the powder on a platform (corundum sheet), transferring the powder into a reactor (low-temperature plasma chamber), and introducing hydrogen. And (3) after introducing hydrogen, performing hydrogen plasma treatment with the radio frequency power of 180W and the plasma treatment time of 20min, 40min and 60min respectively at the pressure of 20Pa in the low-temperature plasma chamber to obtain the electrocatalyst (copper-based catalyst material rich in oxygen vacancies) with the hydrogen plasma regulation and control performance.
(3) Dispersing 10mg of the electrocatalyst with the hydrogen plasma regulation and control performance in 1mL of solvent, and performing ultrasonic dispersion uniformly to obtain catalyst ink; the solvent is a mixture of 450 mu L of isopropanol, 450 mu L of ultrapure water and 100 mu L of Nifion solution; the mass percentage concentration of the Nifion solution is 5wt%; 80 μ L of the catalyst ink was applied to carbon paper (1X 1 cm) 2 ) And obtaining the cuprous oxide catalyst electrode material supported by the carbon paper, wherein the mark is H-20, H-40 and H-60 (the corresponding plasma treatment time is 20min, 40min and 60 min).
The X-ray diffraction (XRD) pattern of the cuprous oxide catalyst treated with hydrogen plasma obtained in example 2 is shown in fig. 9, and the sample treated with hydrogen plasma does not show significant difference in crystal structure.
Example 3
A preparation method of an electrocatalyst for regulating and controlling performance of low-temperature plasma comprises the following steps:
(1) Preparation of cuprous oxide catalyst by liquid phase deposition method: 0.8g of copper salt (CuSO is selected) 4 ) Adding the mixed solution into 150mL of deionized water, uniformly mixing to obtain a mixed solution, adjusting the pH of the mixed solution to 12.0, adding 0.9g of a reducing agent (ascorbic acid) into the mixed solution, heating the mixed solution under stirring for heating reaction at 60 ℃ for 6 hours to obtain a copper-based catalyst;
(2) And (3) low-temperature plasma technology treatment: and (2) grinding the copper-based catalyst in the step (1) into powder, then uniformly coating the powder on a platform (corundum sheet), transferring the powder into a reactor (low-temperature plasma chamber), and introducing argon. And after argon is introduced, performing argon plasma treatment under the pressure of a low-temperature plasma chamber of 20Pa, wherein the radio frequency power of the plasma treatment is 180W, and the plasma treatment time is 20min, so as to obtain the electrocatalyst (copper-based catalyst material rich in oxygen vacancies and surface hydroxyl groups) with the low-temperature plasma regulation and control performance.
(3) Dispersing 10mg of the electrocatalyst with the low-temperature plasma regulation and control performance in 1mL of solvent, and uniformly dispersing by using ultrasonic waves to obtain catalyst ink; the solvent is a mixture of 450 mu L of isopropanol, 450 mu L of ultrapure water and 100 mu L of Nifion solution; the mass percentage concentration of the Nifion solution is 5wt%; 80 μ L of the catalyst ink was applied dropwise to carbon paper (1X 1 cm) 2 ) Thus obtaining the copper-based catalyst electrode material supported by the carbon paper.
Example 4
A preparation method of an electrocatalyst with low-temperature plasma regulation and control performance comprises the following steps:
(1) Preparation of cuprous oxide catalyst by liquid phase deposition method: 0.8g of copper salt (CuSO is selected) 4 ) Adding 3.6g of surfactant (polyvinylpyrrolidone and K-13 are selected) into 150mL of deionized water, uniformly mixing to obtain a mixed solution, adjusting the pH of the mixed solution to 12.0, adding 0.9g of reducing agent (ascorbic acid is selected), heating under a stirring state for heating reaction at the temperature of 60 ℃ for 1 hour, and obtaining the copper-based catalyst;
(2) And (3) low-temperature plasma technical treatment: and (2) grinding the copper-based catalyst in the step (1) into powder, then uniformly coating the powder on a platform (corundum sheet), transferring the powder into a reactor (low-temperature plasma chamber), and introducing argon. And after argon is introduced, performing argon plasma treatment under the pressure of 20Pa in the low-temperature plasma chamber, wherein the radio frequency power of the plasma treatment is 180W, and the plasma treatment time is 60min, so as to obtain the electrocatalyst (copper-based catalyst material rich in oxygen vacancies and surface hydroxyl groups) with the low-temperature plasma regulation and control performance.
(3) Dispersing 10mg of the electrocatalyst with the low-temperature plasma regulation and control performance in 1mL of solvent, and uniformly dispersing by using ultrasonic waves to obtain catalyst ink; the solvent is a mixture of 450 mu L of isopropanol, 450 mu L of ultrapure water and 100 mu L of Nifion solution; the mass percent concentration of the Nifion solution is 5wt%; 80 μ L of the catalyst ink was applied to the carbonPaper (1X 1 cm) 2 ) Thus obtaining the carbon paper supported copper-based catalyst electrode material.
Effect verification
Scanning Electron Microscope (SEM) images of the copper-based catalyst obtained in the step (1) in the example 1 before and after low-temperature plasma treatment is regulated and controlled for 60min are shown in figure 1, the obtained sample is nano-particles with the average particle size of about 100-200 nm, and the sample has no obvious structural difference before and after plasma treatment.
FIG. 2 shows a High Resolution Transmission Electron Microscopy (HRTEM) image of the copper-based catalyst obtained in step (1) in example 1 after being regulated and controlled by low temperature plasma treatment for 60min, wherein the lattice spacing of the obtained sample is 0.246nm, which corresponds to Cu 2 The (111) crystal plane of O.
The X-ray diffraction (XRD) patterns of the carbon-paper-supported cuprous oxide catalyst electrode materials Ar-60, ar-40, ar-20 obtained in example 1 and the carbon-paper-supported cuprous oxide catalyst electrode material Prinstine obtained in comparative example 1 are shown in FIG. 3, the X-ray diffraction (XRD) patterns of the carbon-paper-supported cuprous oxide catalyst electrode materials H-60, H-40, H-20 obtained in example 2 and the carbon-paper-supported cuprous oxide catalyst electrode material Prinstine obtained in comparative example 1 are shown in FIG. 9, and it was found that the patterns of the samples obtained in example and comparative example 1 and Cu were shown in FIG. 9 2 O (PDF NO. 05-0667), no impurities such as Cu and CuO, and no obvious crystal structure change of a sample treated by argon plasma.
The Electron Paramagnetic Resonance (EPR) pattern of the carbon paper supported cuprous oxide catalyst electrode material Ar-60 obtained in example 1 and the carbon paper supported cuprous oxide catalyst electrode material Pristine obtained in comparative example 1 is shown in fig. 4, and the signal intensity (g = 2.003) of the sample obtained in example 1 is significantly increased relative to the sample of comparative example 1, indicating an increase in the oxygen vacancy concentration of the material.
The cuprous oxide catalyst electrode material before and after the adjustment and control of the low-temperature plasma technology is used in the nitrate electrocatalytic reduction reaction. The test conditions were: the experiment adopted CHI660E electrochemical workstation of Shanghai Chenghua, the standard three-electrode system was used as the test system, and the carbon paper supported cuprous oxide catalyst electrode material Ar-60. Ar-40 and the cuprous oxide catalyst electrode material Pristine supported by the carbon paper obtained in the comparative example 1 are respectively used as a working electrode, a platinum net is used as a counter electrode, saturated Ag/AgCl is used as a reference electrode, and 0.5M Na is used 2 SO 4 And 200ppm NaNO 3 The mixed solution is used as an electrolyte, and the cyclic voltammetry curve is tested at room temperature, and the sweep rate is 5mV/s. Fig. 5 shows cyclic voltammograms of the defective cuprous oxide catalyst obtained in example 1 and the comparative example, and the response current of the cuprous oxide catalyst (cuprous oxide catalyst electrode material supported by carbon paper) regulated by plasma provided in the example of the present invention to the nitrate reduction reaction is significantly larger than that of the original untreated cuprous oxide catalyst material in the comparative example 1. Ar-60 provided in example 1 was selected and mixed with 0.5M Na 2 SO 4 The electrolyte was tested as a comparison to the hydrogen evolution reaction and the cyclic voltammogram is shown in FIG. 6.
The proportions of nitrogen-containing species obtained by performing the nitrate electrocatalytic reduction reaction on the carbon paper-supported cuprous oxide catalyst electrode materials Ar-60 and Ar-40 obtained in example 1 and the carbon paper-supported cuprous oxide catalyst electrode material Pristine obtained in comparative example 1 are shown in fig. 7. The conversion rate of the cuprous oxide catalyst regulated and controlled by the plasma to nitrate provided by the embodiment of the invention is obviously higher than that of the original untreated cuprous oxide catalyst material in the comparative example 1, and the proportion and the selectivity of ammonia in the product are obviously improved.
The electrochemical ac impedance curves of the carbon paper supported cuprous oxide catalyst electrode materials Ar-60 and Ar-40 obtained in example 1 and the carbon paper supported cuprous oxide catalyst electrode material Pristine obtained in comparative example 1 for the nitrate reduction reaction are shown in fig. 8. The curve semicircle of the cuprous oxide catalyst regulated and controlled by the plasma provided by the invention is much smaller than that of the original untreated sample, which shows that the interface impedance and the charge transfer resistance are reduced.
As can be seen from fig. 1 to 9, plasma regulation is an effective means for improving the electrocatalytic activity of the nitrate of the copper-based oxide catalyst. The invention adopts the low-temperature plasma technology to regulate and control the plasma defects of the copper-based oxide, and successfully introduces oxygen defects on the surface of the copper oxide. The surface oxygen vacancy concentration of the defect-rich cuprous oxide catalyst regulated and controlled by the plasma is improved, the charge transfer of a catalyst/solution interface is promoted, the excellent nitrate reduction catalytic performance is shown, the nitrate conversion rate is high, and the ammonia selectivity is high. The method has the advantages of simple operation, no need of adding additional chemical reagents, no change of the morphology structure and phase of the copper-based catalyst material, environmental friendliness and capability of becoming a technical means for surface modification in the field of catalysis.
The electrocatalysts with low-temperature plasma regulation performance prepared in other examples also have good nitrate reduction catalytic performance, and can be seen in reference to fig. 1-9.
The above examples are only preferred embodiments of the present invention, which are intended to be illustrative and not limiting, and those skilled in the art should understand that they can make various changes, substitutions and alterations without departing from the spirit and scope of the invention.

Claims (7)

1. A preparation method of an electrocatalyst with low-temperature plasma regulation and control performance is characterized by comprising the following steps:
(1) Adding a copper salt and a surfactant into water, uniformly mixing to obtain a mixed solution, adjusting the pH of the mixed solution to be alkaline, then adding a reducing agent, heating under a stirring state to perform a heating reaction to obtain a copper-based catalyst; the copper salt is more than one of copper sulfate, copper nitrate and copper chloride; the surfactant is one of polyethylene glycol and polyvinylpyrrolidone; the reducing agent is more than one of glucose, ascorbic acid and sodium borohydride;
(2) Grinding the copper-based catalyst in the step (1) into powder, then uniformly coating the powder on a platform, transferring the powder into a reactor, introducing reaction gas, and carrying out plasma treatment to obtain the electrocatalyst with the low-temperature plasma regulation and control performance; the reaction gas is more than one of argon, hydrogen, air and oxygen, and the gas pressure in the reactor is 1-30Pa after the reaction gas is introduced into the reactor; the radio frequency power of the plasma treatment is 50-450W, the plasma treatment time is 1-100min, and the plasma treatment temperature is 20-60 ℃; in the step (2), after the plasma treatment is carried out, the obtained catalyst is a cuprous oxide catalyst material rich in oxygen vacancies and surface hydroxyl groups.
2. The method for preparing the electrocatalyst for regulating and controlling the performance of low-temperature plasma according to claim 1, wherein, in the step (1), in terms of parts by mass,
Figure FDA0003808426490000011
3. the method for preparing the electrocatalyst with low-temperature plasma regulation and control performance according to claim 1, wherein in the step (1), the pH value of the mixed solution is adjusted to 9-12; the heating reaction temperature in the step (1) is 20-60 ℃, and the heating reaction time is 30-420min.
4. An electrocatalyst with low temperature plasma modulating properties prepared by the process of any one of claims 1 to 3.
5. The use of the electrocatalyst for low temperature plasma regulation performance in nitrate electrocatalytic reduction according to claim 4, comprising the steps of:
(1) Adding the electrocatalyst with the low-temperature plasma regulation and control performance into a solvent, uniformly dispersing to obtain catalyst ink, and then dripping the catalyst ink on a conductive current collector to obtain an electrode material containing the catalyst;
(2) And (2) performing an electrocatalytic nitrate reduction reaction by using the electrode material containing the catalyst in the step (1) as a working electrode, platinum as a counter electrode, ag/AgCl as a reference electrode and a nitrate-containing solution as an electrolyte.
6. The application of the electrocatalyst for regulating and controlling the performance of low-temperature plasma in the nitrate electrocatalytic reduction according to claim 5, wherein the solvent in the step (1) is a mixture of isopropanol, ultrapure water and a Nifion solution, and the volume ratio of the isopropanol, the ultrapure water and the Nifion solution is 45; the concentration of the Nifion solution is 5 +/-0.5 wt%; the concentration of the electrocatalyst with the low-temperature plasma regulation and control performance in the solvent is 5-50mg/mL.
7. The application of the electrocatalyst for regulating and controlling the performance of the low-temperature plasma in the electrocatalytic reduction of nitrate according to claim 5, wherein the conductive current collector in the step (1) is one or more of carbon cloth, carbon paper, nickel foam, copper foam and FTO conductive glass; the nitrate radical-containing solution in the step (2) is NaNO 3 Solutions or KNO 3 One or more of a solution; the voltage of the electro-catalytic reduction reaction of the nitrate in the step (2) is 0.8-1.5V, and the time of the electro-catalytic reduction reaction of the nitrate is 0.5-9h.
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