CN116145193B - Copper-based catalyst for electrocatalytic reduction of nitrate radical into ammonia and preparation method thereof - Google Patents

Copper-based catalyst for electrocatalytic reduction of nitrate radical into ammonia and preparation method thereof Download PDF

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CN116145193B
CN116145193B CN202310406064.0A CN202310406064A CN116145193B CN 116145193 B CN116145193 B CN 116145193B CN 202310406064 A CN202310406064 A CN 202310406064A CN 116145193 B CN116145193 B CN 116145193B
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carbon cloth
ammonia
nitrate
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copper
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CN116145193A (en
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王艳琴
刘洋
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Inner Mongolia University
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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
    • 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
    • C25B1/01—Products
    • C25B1/27—Ammonia
    • 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
    • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
    • C25B11/056—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of textile or non-woven fabric
    • 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
    • C25B11/055—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

Abstract

The invention belongs to the field of catalyst preparation, and provides a copper-based catalyst for electrocatalytic reduction of nitrate radical into ammonia and a preparation method thereof, comprising the following steps: (1) pretreatment of carbon cloth: putting the cut carbon cloth into a round bottom flask filled with concentrated nitric acid, putting the flask into an oil bath pot, boiling for 7-9 hours, washing with water, and then soaking in distilled water for standby; (2) preparation of electrodeposition liquid: taking CuSO 4 ·5H 2 O、AgNO 3 Dissolving NaOH in a mixed solvent of ethanol and water, and stirring for 9-11 minutes at room temperature for later use; (3) electrodepositing a metal salt onto the pretreated carbon cloth; (4) sintering a catalyst: heating the electrodeposited carbon cloth to 550 ℃ at a speed of 5 ℃/min, calcining for 2 hours, and cooling to room temperature to obtain Cu loaded on the carbon cloth x O/Ag-CC heterojunction electrode material, denoted as Cu x O/Ag‑CC。

Description

Copper-based catalyst for electrocatalytic reduction of nitrate radical into ammonia and preparation method thereof
Technical Field
The invention belongs to the field of catalyst preparation, and particularly relates to a copper-based catalyst for electrocatalytic reduction of nitrate radical into ammonia and a preparation method thereof.
Background
Ammonia (NH) 3 ) The material is widely applied as a precursor, fuel and energy carrier of chemical fertilizers and various chemicals, and is very important for the development of industry, agriculture and even all human beings. At present, NH is industrially produced 3 Mainly depends on the ancient Haber-Bose process, which requires more severe reaction conditions such as high temperature (300-550 ℃), high pressure (200-350 atm), iron-based catalyst and the like, resulting in large amount of stone fuel consumption and CO 2 And (5) discharging. Therefore, in the background of increasingly depleted fossil energy sources and increasingly serious environmental pollution problems, it is urgent to find new technologies for replacing the haber-bose ammonia production process. In recent years, in various alternative ammonia production methods such as a photocatalytic method, an electrocatalytic method, and a biocatalytic method, an electrocatalytic ammonia production route driven by renewable power of solar energy or wind energy as an energy source has been developed in the past few years. Electrochemical nitrogen reduction (NRR) is one of the electrocatalytic ammonia production pathways that produces NH 3 From N in the electrolyte 2 And H 2 Reaction of O under ambient conditions. However, since NRR has a strong N≡N triple bond energy, N 2 The solubility in water is very low and the competitive Hydrogen Evolution Reaction (HER), NRR activity and selectivity (faraday efficiency (FE)) is low. In additionLow NH 3 The yield is often subjected to environmental NH 3 Trouble and suspicion of contamination, thus, in N 2 NRR, which is a nitrogen source, still faces a great challenge in practical applications.
Nitrate radical (NO) 3 (ii) ions are one of the pollutants widely existing in water bodies worldwide, and are used for replacing and stabilizing N 2 NH generation 3 Is a potential source of nitrogen. The nitrate sources in the surface water and the underground water mainly come from dry and wet sedimentation and sewage irrigation of domestic sewage, garbage, excrement, chemical fertilizers, industrial wastewater and atmospheric nitrogen oxides, and the concentration range is wide and is about 0-2M. It is known to break NO 3 The energy required for the bond to form the oxygen scavenging group is only 204 kJ/mol, much lower than N 2 The energy of the N.ident.N bond (941 kJ/mol). Thus, from the viewpoint of renewable energy and environmental protection, NO will be 3 Conversion to NH 3 Is very preferable, and can simultaneously realize the purposes of ammonia production and wastewater treatment. However, from NO 3 -to NH 3 Comprises an 8-step reaction, the kinetics of which are slow, involving the transfer of 8 e-F (NO 3 ˉ+ 6H 2 O + 8e¯→NH 3 +9OH-in alkaline medium) and relatively more possible reaction intermediates/products (NO 2 、NO 2 ˉ、N 2 O、NO、N 2 、NH 2 OH、NH 2 NH 2 And NH 3 ). Thus, NO is efficiently and highly selectively released 3 Is converted into the target product NH 3 Is the development of a highly active, highly selective catalyst.
Disclosure of Invention
To solve the above problems, the inventors have studied various metal and metal-based electrocatalysts, such as Fe, mo, ti, pd, ni, ag, cu, in which Cu-based NO 3 RR electrocatalyst is due to its excellent NO 3 RR catalytic Activity and NH 3 N selectivity, in addition to metallic silver being a good conductor of electricity, the introduction of silver can increase the electrical conductivity of the catalyst, and the use of carbonaceous materials such as reduced graphene oxide (rGO), carbon cloth and carbon nanoplatelets can not only provide support for the metal-based nanostructures, but also enhance their electrical conductivity and prevent their agglomeration, based onThe invention provides a copper-based catalyst for electrocatalytic reduction of nitrate into ammonia with high catalytic activity, high ammonia yield, high Faraday efficiency, high ammonia selectivity and high conversion rate, and also provides a preparation method thereof, which comprises the following steps:
step (1), pretreatment of carbon cloth:
putting the cut carbon cloth into a round bottom flask filled with concentrated nitric acid, putting the flask into an oil bath pot, boiling for 7-9 hours, washing with water, and then soaking in distilled water for standby;
step (2), preparing electrodeposition liquid:
taking CuSO 4 ·5H 2 O、AgNO 3 Dissolving NaOH in a mixed solvent of ethanol and water, and stirring for 9-11 minutes at room temperature for later use;
step (3), electrodepositing metal salt on the pretreated carbon cloth:
electrodepositing on a CHI 660E electrochemical workstation by adopting a three-electrode system;
sintering the catalyst in the step (4):
placing electrodeposited carbon in a porcelain boat, placing in the center of a tube furnace, introducing argon gas at a flow rate of 190-210 mL/min, introducing air for 14-16min to exhaust air in the tube, heating to 550 ℃ at a speed of 5 ℃/min, calcining for 2h, cooling to room temperature, and obtaining Cu loaded on the carbon cloth x O/Ag-CC heterojunction electrode material, denoted as Cu x O/Ag-CC。
Further, in the step (1), the area of the sheared carbon cloth is 2cm multiplied by 2cm; the amount of concentrated nitric acid is 28-32 mL.
Further, in the step (1), the temperature of the oil bath is 75-85 ℃.
Further, in the step (2), the electrodeposition method is as follows:
s1, transferring the solution in the step (2) into an electrolytic cell to serve as an electrodeposition solution;
s2, clamping the carbon cloth processed in the step (1) into a working electrode clamp, wherein a counter electrode and a reference electrode are respectively Pt sheets and Ag/AgCl, and saturated KCl solution is adopted as a working electrode;
s3, after the electrolytic cell is connected with the workstation, depositing the front and back sides of the carbon cloth for 290-310 seconds respectively by adopting a timing current method, and then placing the carbon cloth into a vacuum drying oven for drying overnight for standby;
further, in step (2), cuSO 4 ·5H 2 The amount of O is 0.31-0.33g, agNO 3 In an amount of 0.16-0.18 g.
Further, in the step (2), the amount of NaOH is 0.29 to 0.31g.
Further, in the step (2), the mixed solvent of ethanol and water is 28-32mL, and the volume ratio of the ethanol to the water is 1:2.
In another aspect, the present invention provides Cu supported on carbon cloth x O/Ag-CC heterojunction electrode material, denoted as Cu x O/Ag-CC。
On the other hand, the copper-based catalyst for electrocatalytic reduction of nitrate radical into ammonia is utilized to synthesize ammonia by electrocatalytic reduction of nitrate radical, and the application voltage is-0.54 to-0.94V.
Further, the electrocatalytic reduction of nitrate to ammonia is performed with a copper-based catalyst that electrocatalytically reduces nitrate to ammonia, with an applied voltage of-0.74V.
Compared with the prior art, the technical scheme of the invention has the following advantages:
1. the invention provides electrocatalytic NO 3 The RR electrode material has good conductivity, the nitrate is reduced into ammonia, which is a multi-electron transfer process, the valence state transition from +5 to-3 is involved, the material is required to have extremely high conductivity, the Cu-based material has certain conductivity, and the electrode material greatly improves the conductivity of the catalyst by introducing Ag with high conductivity, so that the high-efficiency NO is designed 3 RR electrocatalysts provide a reference.
2. The construction strategy of the catalyst is beneficial to exposing more catalytic active sites, and the heterostructure between the Cu component and the Ag component not only accelerates the electron transfer between interfaces, but also can expose more active sites; in addition, the structure of the heterostructure greatly optimizes the electronic structure of the catalyst, and is favorable for the adsorption of the catalyst to the reaction intermediate and the desorption of the product, thereby being more favorable for the electrocatalytic reduction of nitrate to produce ammonia.
3. The invention has the advantages of low concentration of 0.01M NO 3 Electrolytic experiments were carried out in an electrolyte of-0.74. 0.74V (vs. RHE) prepared Cu x The O/Ag-CC heterojunction electrode material can obtain 2.2 mg h -1 cm -2 High NH of (2) 3 Yield, ammonia Faraday efficiency, 67.66% NH 3 Selectivity and 54.69% NO 3 -conversion of N.
4. The invention explores a Cu by constructing a heterogeneous interface x O/Ag-CC heterostructure electrocatalyst and preparation method thereof, and efficient synthesis of NH by nitrate is realized under environmental conditions 3 In this heterostructure electrocatalyst, cu x The synergistic effect of the O and Ag components improves the overall catalytic activity of the catalyst.
5. In NO 3 Cu in RR electrolysis process x The heterogeneous interface between O and Ag can accelerate interface electron transfer, expose more active sites, optimize d band center of the catalyst, and regulate adsorption energy of the catalyst to the reaction intermediate.
Drawings
FIG. 1 is a flow chart of catalyst preparation.
FIGS. 2a, 2b are Cu x O/Ag-CC scanning electron microscope image; FIG. 2c is Cu x O/Ag-CC transmission electron microscopy, the inset in FIG. 2c is Cu x Selected area electron diffraction pattern of O/Ag-CC; FIG. 2d is Cu x High resolution transmission electron microscope image of O/Ag-CC, FIG. 2e is Cu x And an element map of O/Ag-CC, wherein 2f, 2g and 2h are respectively the distribution of three elements Cu, ag and O.
FIG. 3 is Cu x Powder XRD pattern of O/Ag-CC.
FIG. 4 is Cu x Ammonia yield and faraday efficiency plot for electrocatalytic nitrate reduction synthesis of ammonia at 5 different voltages for O/Ag-CC.
FIG. 4a is Cu x Electrochemical LSV graphs of O/Ag-CC at 5 different voltages; FIG. 4b is Cu x O/Ag-CC under 5 different voltagesAmmonia yield and faraday efficiency plot of (2); FIG. 4c is Cu x The O/Ag-CC is subjected to an ammonia selectivity and nitrate conversion chart of electrocatalytic nitrate reduction synthetic ammonia under 5 different voltages; FIG. 4d is a catalyst Cu x O/Ag-CC、Cu x Comparison graphs of four performance parameters of O-CC, ag-CC ammonia yield, faraday efficiency, ammonia selectivity and nitrate conversion.
FIG. 5a is Cu x Ammonia yield and faraday efficiency plot of O/Ag-CC after 5 electrocatalytic nitrate reduction synthesis ammonia cycling experiments; FIG. 5b is Cu x NH after O/Ag-CC is subjected to 5 times of electrocatalytic nitrate radical reduction ammonia synthesis circulation experiments 3 -N-selectivity, NO 2 - -N selectivity and NO 3 - -N conversion.
FIG. 6 is left to right Cu x O/Ag-CC、Cu x O-CC, ag-CC product diagram.
FIG. 7 is a schematic diagram of an electrolytic cell reaction apparatus for electrocatalytic reduction of nitrate to ammonia.
Description of the embodiments
The following description of the embodiments of the present invention will be made clearly and completely, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
A method for preparing a copper-based catalyst for electrocatalytic reduction of nitrate to ammonia, comprising the steps of:
step (1), pretreatment of carbon cloth:
putting the cut carbon cloth into a round bottom flask filled with concentrated nitric acid, putting the flask into an oil bath pot, boiling for 7 hours, washing with water, and then soaking in distilled water for standby;
step (2), preparing electrodeposition liquid:
taking CuSO 4 ·5H 2 O、AgNO 3 And NaOH are dissolved in a mixed solvent of ethanol and water, and stirred for 9 minutes at room temperature for standby.
Step (3), electrodepositing metal salt on the pretreated carbon cloth:
electrodepositing on a CHI 660E electrochemical workstation by adopting a three-electrode system;
sintering the catalyst in the step (4):
placing electrodeposited carbon in a porcelain boat, placing in the center of a tube furnace, introducing argon gas at a flow rate of 190 mL/min, introducing air for 14 min to drain air in the tube, heating to 550 ℃ at a speed of 5 ℃/min, calcining for 2h, cooling to room temperature, and obtaining Cu loaded on the carbon cloth x O/Ag-CC heterojunction electrode material, denoted as Cu x O/Ag-CC。
In the step (1), the area of the sheared carbon cloth is 2cm multiplied by 2cm; the amount of concentrated nitric acid was 28 mL.
In step (1), the temperature of the oil bath was 75 ℃.
In the step (2), the electrodeposition method comprises the following steps:
s1, transferring the solution in the step (2) into an electrolytic cell to serve as an electrodeposition solution;
s2, clamping the carbon cloth processed in the step (1) into a working electrode clamp, wherein a counter electrode and a reference electrode are respectively Pt sheets and Ag/AgCl, and saturated KCl solution is adopted as a working electrode;
s3, after the electrolytic cell is connected with the workstation, depositing the front and back sides of the carbon cloth for 290-310 seconds respectively by adopting a timing current method, and then placing the carbon cloth into a vacuum drying oven for drying overnight for standby;
in step (2), cuSO 4 ·5H 2 The amount of O was 0.31g, agNO 3 Is 0.16. 0.16 g.
In step (2), the amount of NaOH was 0.29 and g.
In the step (2), the mixed solvent of ethanol and water is 28 mL, and the volume ratio of the ethanol to the water is 1:2.
Example 2
A method for preparing a copper-based catalyst for electrocatalytic reduction of nitrate to ammonia, comprising the steps of:
step (1), pretreatment of carbon cloth:
putting the cut carbon cloth into a round bottom flask filled with concentrated nitric acid, putting the flask into an oil bath pot, boiling for 9 hours, washing with water, and then soaking in distilled water for standby;
step (2), preparing electrodeposition liquid:
taking CuSO 4 ·5H 2 O、AgNO 3 And NaOH are dissolved in a mixed solvent of ethanol and water, and stirred at room temperature for 11 minutes for standby.
Step (3), electrodepositing metal salt on the pretreated carbon cloth:
electrodepositing on a CHI 660E electrochemical workstation by adopting a three-electrode system;
sintering the catalyst in the step (4):
placing electrodeposited carbon in a porcelain boat, placing in the center of a tube furnace, introducing argon gas at a flow rate of 210 mL/min, introducing air for 16min to drain air in the tube, heating to 550 ℃ at a speed of 5 ℃/min, calcining for 2h, cooling to room temperature, and obtaining Cu loaded on the carbon cloth x O/Ag-CC heterojunction electrode material, denoted as Cu x O/Ag-CC。
In the step (1), the area of the sheared carbon cloth is 2cm multiplied by 2cm; the amount of concentrated nitric acid was 32 mL.
In step (1), the temperature of the oil bath was 85 ℃.
In the step (2), the electrodeposition method comprises the following steps:
s1, transferring the solution in the step (2) into an electrolytic cell to serve as an electrodeposition solution;
s2, clamping the carbon cloth processed in the step (1) into a working electrode clamp, wherein a counter electrode and a reference electrode are respectively Pt sheets and Ag/AgCl, and saturated KCl solution is adopted as a working electrode;
s3, after the electrolytic cell is connected with the workstation, depositing the front and back sides of the carbon cloth for 290-310 seconds respectively by adopting a timing current method, and then placing the carbon cloth into a vacuum drying oven for drying overnight for standby;
in step (2), cuSO 4 ·5H 2 Amount of O0.33g of AgNO 3 Is 0.18 g.
In the step (2), the amount of NaOH was 0.31g.
In the step (2), the mixed solvent of ethanol and water is 32mL, and the volume ratio of the ethanol to the water is 1:2.
Example 3
A method for preparing a copper-based catalyst for electrocatalytic reduction of nitrate to ammonia, comprising the steps of:
step (1), pretreatment of carbon cloth:
putting the cut carbon cloth into a round bottom flask filled with concentrated nitric acid, putting the flask into an oil bath pot, boiling for 8 hours, washing with water, and then soaking in distilled water for standby;
step (2), preparing electrodeposition liquid:
taking CuSO 4 ·5H 2 O、AgNO 3 And NaOH are dissolved in a mixed solvent of ethanol and water, and stirred for 10 minutes at room temperature for standby.
Step (3), electrodepositing metal salt on the pretreated carbon cloth:
electrodepositing on a CHI 660E electrochemical workstation by adopting a three-electrode system;
sintering the catalyst in the step (4):
placing electrodeposited carbon in a porcelain boat, placing in the center of a tube furnace, introducing argon gas at a flow rate of 200 mL/min, introducing air for 15 min to drain air in the tube, heating to 550 ℃ at a speed of 5 ℃/min, calcining for 2h, cooling to room temperature, and obtaining Cu loaded on the carbon cloth x O/Ag-CC heterojunction electrode material, denoted as Cu x O/Ag-CC。
In the step (1), the area of the sheared carbon cloth is 2cm multiplied by 2cm; the amount of concentrated nitric acid was 30 mL.
In step (1), the temperature of the oil bath was 80 ℃.
In the step (2), the electrodeposition method comprises the following steps:
s1, transferring the solution in the step (2) into an electrolytic cell to serve as an electrodeposition solution;
s2, clamping the carbon cloth processed in the step (1) into a working electrode clamp, wherein a counter electrode and a reference electrode are respectively Pt sheets and Ag/AgCl, and saturated KCl solution is adopted as a working electrode;
s3, after the electrolytic cell is connected with the workstation, depositing the front and back sides of the carbon cloth for 290-310 seconds respectively by adopting a timing current method, and then placing the carbon cloth into a vacuum drying oven for drying overnight for standby;
in step (2), cuSO 4 ·5H 2 The amount of O was 0.32 g, agNO 3 Is 0.17 and g.
In step (2), the amount of NaOH was 0.30 and g.
In the step (2), the mixed solvent of ethanol and water is 30 mL, and the volume ratio of the ethanol to the water is 1:2.
Comparative example 1
This comparative example was the same as example 3 except that carbon was placed in a tube furnace to a temperature of 450 ℃ during the catalyst sintering process, and the specific results are shown in table 1.
Comparative example 2
This comparative example was the same as example 3 except that carbon was placed in a tube furnace to a temperature of 350 c during the catalyst sintering process, and the specific results are shown in table 1.
Comparative example 3
In the preparation of the electrodeposition liquid of the step (2), cuSO 4 ·5H 2 The amount of O was 0.64 and g, and the specific results are shown in Table 1, except that the amount of O was the same as in example 3.
Comparative example 4
AgNO in the preparation of the electrodeposition liquid of the step (2) was removed in this comparative example 3 The same procedure as in example 3 was repeated except that the amount of (2) was 0.34 and g, and the specific results are shown in Table 1.
TABLE 1 catalyst ammonia yield, faraday efficiency Table
Experimental part
Experiment one
Cu obtained in example 3 x XRD characterization of the O/Ag-CC catalyst, as shown in FIG. 3, it can be seen from FIG. 3 that the peak of 2 Theta at 38.12 deg. can be attributed to the Ag (111) crystal face, and the peaks of 2 Theta at 36.42 deg. and 42.30 deg. can be attributed to Cu x The (111) and (200) crystal faces of O, the large package of which the 2 Theta is about 25 degrees is a peak of carbon cloth, and the XRD pattern shows Cu x Both O and Ag grow on carbon cloth.
Experiment two
Cu is added with x The O/Ag-CC was electrocatalytic nitrate reduction to ammonia at 5 different voltages as shown in FIG. 4.
As can be seen from FIG. 4a, the composition contains KNO 3 In the electrolyte of (2), the current density in the LSV curve becomes significantly higher, indicating the catalyst Cu x O/Ag-CC is active for nitrate reduction. Determination of NH by colorimetry using Neschler reagent 4 + Yield, NO determination by colorimetry using Griess reagent 2 - Is determined colorimetrically by using sulfamic acid 3 - As can be seen from FIG. 4b, the ammonia yield gradually increased with increasing potential by testing at five different potentials, and reached a maximum of 85.03% ammonia Faraday efficiency at-0.74 and V, with an ammonia yield of 2.2 mg h -1 cm -2 . FIG. 4c is Cu x The O/Ag-CC is subjected to an ammonia selectivity and nitrate conversion chart of electrocatalytic nitrate reduction synthetic ammonia under 5 different voltages; from the figure we can see that after five different potential tests, at-0.84V, cu x The O/Ag-CC catalyst can obtain 83.12 percent of NH 3 Selectivity and 60.88% of NO 3 -conversion of N. FIG. 4d is a catalyst Cu x O/Ag-CC、Cu x Comparison of four performance parameters of O-CC, ag-CC, faraday efficiency, ammonia selectivity and conversion, as can be seen from the graph, cu x The values of the four parameters of O/Ag-CC are all higher than those of the other two control catalysts.
Experiment three
Cu is added with x The O/Ag-CC is subjected to 5 electrocatalytic nitrate radical reduction ammonia synthesis cycle experiments, and is shown in FIG. 5.
FIG. 5a is Cu x O/Ag-CC Ammonia yield and Faraday efficiency plot after 5 electrocatalytic nitrate reduction synthesis ammonia cycling experiments were performed. FIG. 5b is Cu x NH after O/Ag-CC is subjected to 5 times of electrocatalytic nitrate radical reduction ammonia synthesis circulation experiments 3 -N-selectivity, NO 2 ¯ -N selectivity and NO 3 ¯ -N conversion. NH4 was determined colorimetrically by performing five i-t tests at a potential of-0.74V after testing at five different potentials using Nessler reagent + Concentration, determination of NO by colorimetry using Griess reagent 2 ¯ Is determined colorimetrically by using sulfamic acid 3 - To evaluate the cycling stability of the material, it can be seen from FIG. 5 that after five cycles, cu x The 4 performance parameters of the O/Ag-CC catalyst material all tend to be at a stable level, which can prove that Cu x The O/Ag-CC catalyst material has good cycle stability.
Experiment four
The prepared catalyst is clamped in a working electrode clamp, and is placed in a cathode pool containing 40 mL of 0.1M KOH electrolyte together with a reference electrode, a counter electrode is placed in an anode pool with the same electrolyte, and the counter electrode is respectively in a KNO containing or not containing 0.01M KNO 3 Under the condition of (1) and (5) performing LSV test, wherein the voltage is set to be 0 to-1.1V. And replacing the electrolyte, respectively performing i-t test under the five potentials of-0.54, -0.64, -0.74, -0.84, -0.94 and V for 1h, and after the test is completed, retaining the electrolyte for later use, wherein the test result is shown in table 2, and all the potentials are converted into standard hydrogen electrodes for test in the process.
TABLE 2 i-t test tables for five different potentials
The experiment is carried out on Cu x Cu in O/Ag-CC catalyst x Both the O and Ag components provide catalytically active sites, and the Ag component additionally imparts good electrical conductivity to the overall catalyst.
As can be seen from Table 2, the present invention is applied to electrodepositionThe method prepares Cu x O/Ag-CC electrocatalyst materials exhibiting excellent NO 3 RR performance at optimum applied potential of-0.74. 0.74V at a range of 0.01M NO 3 ¯ In 0.1M KOH, NH 3 The yield is as high as 2.2 mg h -1 ·cm -2 ，NH 3 Faraday efficiency of 85.03%, NH 3 N selectivity of 67.66%, NO 3 N conversion was 54.69%, a study of the preparation of electrocatalytic NO at ambient conditions 3 The electrocatalyst of RR provides a new approach and concept.

Claims (7)

1. A method for preparing a copper-based catalyst for electrocatalytic reduction of nitrate to ammonia, comprising the steps of:
step (1), pretreatment of carbon cloth:
putting the cut carbon cloth into a round bottom flask filled with concentrated nitric acid, putting the flask into an oil bath pot, boiling for 7-9 hours, washing with water, and then soaking in distilled water for standby;
step (2), preparing electrodeposition liquid:
taking CuSO 4 ·5H 2 O、AgNO 3 Dissolving NaOH in a mixed solvent of ethanol and water, and stirring for 9-11 minutes at room temperature for later use; cuSO 4 ·5H 2 The amount of O is 0.31-0.33g, agNO 3 Is in an amount of 0.16-0.18 g; the amount of NaOH is 0.29-0.31g; the mixed solvent of ethanol and water is 28-32mL, and the volume ratio of the ethanol to the water is 1:2;
step (3), electrodepositing metal salt on the pretreated carbon cloth:
electrodepositing on a CHI 660E electrochemical workstation by adopting a three-electrode system;
sintering the catalyst in the step (4):
placing the carbon electrodeposited by a three-electrode system in a porcelain boat, placing in the center of a tube furnace, introducing argon gas with the flow of 190-210 mL/min, introducing air for 14-16min to exhaust air in the tube, heating to 550 ℃ at the speed of 5 ℃/min, calcining for 2h, cooling to room temperature, and obtaining Cu loaded on the carbon cloth x O/Ag-CC heterojunction electrode material, denoted as Cu x O/Ag-CC。
2. The method for preparing a copper-based catalyst for electrocatalytic reduction of nitrate to ammonia according to claim 1, wherein in the step (1), the sheared carbon cloth area is 2cm x 2cm; the amount of concentrated nitric acid is 28-32 mL.
3. The method for preparing a copper-based catalyst for electrocatalytic reduction of nitrate to ammonia according to claim 1, wherein in the step (1), the temperature of the oil bath is 75-85 ℃.
4. The method for preparing a copper-based catalyst for electrocatalytic reduction of nitrate to ammonia according to claim 1, wherein in the step (3), the three-electrode system electrodeposition method comprises:
s1, transferring the solution in the step (2) into an electrolytic cell to serve as an electrodeposition solution;
s2, clamping the carbon cloth processed in the step (1) into a working electrode clamp, wherein a counter electrode and a reference electrode are respectively Pt sheets and Ag/AgCl, and saturated KCl solution is adopted as a working electrode;
and S3, after the electrolytic cell is connected with the workstation, depositing the front and back sides of the carbon cloth for 290-310 seconds respectively by adopting a timing current method, and then placing the carbon cloth into a vacuum drying oven for drying overnight for standby.
5. A copper-based catalyst for electrocatalytic reduction of nitrate to ammonia, prepared according to the method of any one of claims 1-4.
6. The method for synthesizing ammonia by electrocatalytic nitrate radical reduction by using the copper-based catalyst for electrocatalytic nitrate radical reduction as set forth in claim 5, wherein the application voltage is-0.54 to-0.94V.
7. Electrocatalytic nitrate reduction to ammonia is carried out using a copper-based catalyst for electrocatalytic nitrate reduction to ammonia as claimed in claim 6, wherein the applied voltage is-0.74V.
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