Catalytic electrode material and preparation method and application thereof

Abstract

The invention discloses a catalytic electrode material and a preparation method and application thereof, the catalytic electrode material comprises a catalytic electrode base material and a copper nanosheet loaded on the surface of the catalytic electrode base material, and the catalytic electrode base material is selected from a porous copper base material; the catalytic electrode material can be applied to ammonia production through electro-catalysis of nitrate and / or nitrite reduction, or removal of nitrate and / or nitrite in waste water is achieved through electro-catalysis of nitrate and / or nitrite reduction, the copper nanosheets grow on the surface of the porous copper base material in a loaded mode, enough active sites can be exposed, high grain boundary density is achieved, and the catalytic electrode material can be applied to ammonia production through electro-catalysis of nitrate and / or nitrite reduction. The activity of catalyzing electrochemical reduction of nitrate and / or nitrite can be improved, the NH3 Faraday efficiency and the partial current density are improved, and then the ammonia yield or the removal efficiency of nitrate and nitrite can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a catalytic electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the progress of human social production, the wastewater generated in industrial and agricultural production and daily life is also increasing continuously. Among them, most industrial productions involve nitrate pollution. For example, industries such as mechanical manufacturing, coal mining, photovoltaic pickling, papermaking, chemical fertilizers, electronic components, and electroplating use nitric acid or other nitrogen-containing organic compounds during the production process. These nitrogen-containing substances will ultimately be converted into nitrate nitrogen under the action of artificial or natural transformation. Nitrate pollution will have an adverse impact on the ecological environment and the human body. For example, it will lead to too high nitrogen content in water and eutrophication of water bodies; it will induce some water bodies to produce nitrite substances, increase the incidence of methemoglobinemia and cancer, and cause blue baby syndrome, etc. Nitrate is easily soluble in water, and nitrate ions are difficult to react with most cations to form precipitates, resulting in the inability of the conventional chemical precipitation method to effectively treat nitrates in wastewater. At the same time, compared with other forms of nitrogen-containing compounds, nitrates usually have more stable chemical properties. Therefore, the treatment of nitrate nitrogen is a difficult point in wastewater denitrification treatment. Taking the electroplating industry as an example, reagents such as ammonia water and ammonium chloride are used as raw materials, and nitric acid is also used for pickling and stripping during electroplating, resulting in high-concentration nitrate ions in electroplating wastewater. The "Discharge Standard of Pollutants for Electroplating" (GB 21900-2008) stipulates that the total nitrogen in the wastewater of electroplating enterprises shall not be higher than 30mg·L -1 and 20mg·L -1 . Therefore, there is a general need in the electroplating industry to deeply treat wastewater to reduce the total nitrogen content in the wastewater. At present, biological methods and iron powder reduction methods are often used to remove nitrates in industrial wastewater. However, due to the characteristics of electroplating wastewater, such as high salt or high heavy metals, which are unfavorable to microorganisms, it is difficult for biological methods to achieve the expected treatment effect; while the main reduction product of nitrate in the iron powder reduction method is ammonia nitrogen, which needs further treatment, and the iron powder reduction method produces a large amount of sludge, and the disposal of sludge increases the treatment cost. Electrochemical technology converts nitrate nitrogen into nitrogen that can be directly discharged, with advantages such as easy control of reaction by-products, small floor area, and automation control, and has good application prospects in the denitrification treatment of electroplating wastewater. However, at present, the cathode material is mainly noble metal, and the high electrode cost limits the popularization and application of the electrochemical method.

[0003] Electrocatalytic nitrate reduction reaction (NO3RR, i.e., NO3 - +6H2O+8e - →NH3+9OH - ) Under normal temperature and pressure conditions, using renewable electric energy and water resources, NO3 -The conversion of wastewater into high - value - added NH3 provides a promising "zero - carbon emission" solution for the recycling of nitrogen resources. Research shows that NO3RR involves a complex eight - electron - coupled nine - proton transfer process, resulting in slow kinetic rates and high overpotentials. At the same time, the competitive hydrogen evolution reaction reduces the NH3 Faraday efficiency and partial current density. Therefore, the development of high - selectivity and high - yield NO3RR catalytic materials and application systems is of great significance for ammonia production from nitrate - containing wastewater under mild conditions. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a catalytic electrode material, its preparation method and application.

[0005] In a first aspect of the present invention, a catalytic electrode material is provided, which includes a catalytic electrode substrate and copper nanosheets loaded on the surface of the catalytic electrode substrate, and the catalytic electrode substrate is selected from a porous copper substrate.

[0006] According to the catalytic electrode material of the embodiments of the present invention, it has at least the following beneficial effects: This catalytic electrode material uses a porous copper substrate as the catalytic electrode substrate, and copper nanosheets are grown and loaded on the surface of the porous copper substrate. This catalytic electrode material can be applied to electrocatalytic reduction of nitrate and / or nitrite to ammonia, or electrocatalytic reduction of nitrate and / or nitrite to achieve the removal of nitrate and / or nitrite in wastewater. Among them, the growth and loading of copper nanosheets on the surface of the porous copper substrate can expose enough active sites and have a high grain - boundary density, which can improve the activity of electrochemically reducing nitrate and / or nitrite, increase the NH3 Faraday efficiency and partial current density, and thus improve the ammonia production rate or the removal efficiency of nitrate / nitrite.

[0007] In some embodiments of the present invention, the copper nanosheets are vertically loaded on the surface of the catalytic electrode substrate; further, the copper nanosheets are uniformly and vertically loaded on the surface of the catalytic electrode substrate. Among them, the vertical loading of copper nanosheets on the surface of the catalytic electrode substrate can further expose more active sites, make the catalytic electrode material have a higher grain - boundary density, improve the activity of electrochemically reducing nitrate and / or nitrite, and thus improve the ammonia production efficiency or the removal efficiency of nitrate / nitrite.

[0008] In some embodiments of the present invention, the grain - boundary density of the copper nanosheets is 40μm -1 ~200μm -1 , for example, the grain - boundary density of the copper nanosheets on the surface of the catalytic electrode substrate can be 40μm -1 , 45μm -1 , 50μm -1 , 52μm -1 , 55μm-1 , 60 μm -1 , 65 μm -1 , 68 μm -1 , 70 μm -1 , 75 μm -1 , 80 μm -1 , 84 μm -1 , 85 μm -1 , 87 μm -1 , 90 μm -1 , 93 μm -1 , 95 μm -1 , 96 μm -1 , 100 μm -1 , 110 μm -1 , 125 μm -1 , 120 μm -1 , 130 μm -1 , 135 μm -1 , 140 μm -1 , 150 μm -1 , 155 μm -1 , 160 μm -1 , 170 μm -1 , 180 μm -1 , 185 μm -1 , 190 μm -1 , 200 μm -1 any value among the following or the range value between any two of them.

[0009] In some embodiments of the present invention, the thickness of the catalytic electrode material is 0.3 mm to 50 mm. For example, the thickness of the catalytic electrode material can be any value among 0.3 mm, 0.5 mm, 1 mm, 3 mm, 5 mm, 6 mm, 8 mm, 10 mm, 12 mm, 13 mm, 15 mm, 18 mm, 20 mm, 23 mm, 25 mm, 27 mm, 30 mm, 32 mm, 33 mm, 35 mm, 36 mm, 38 mm, 40 mm, 41 mm, 43 mm, 45 mm, 47 mm, 48 mm, 50 mm or the range value between any two of them.

[0010] In some embodiments of the present invention, the area of the catalytic electrode material is 0.1 cm 2 to 100 cm 2 . For example, the area of the catalytic electrode material can be 0.1 cm 2 , 0.5 cm 2 , 1 cm 2 , 3 cm 2 , 5 cm 2 , 6.5 cm 2 , 8 cm2 , 10 cm 2 , 12 cm 2 , 15 cm 2 , 17 cm 2 , 20 cm 2 , 25 cm 2 , 30 cm 2 , 32 cm 2 , 35 cm 2 , 40 cm 2 , 45 cm 2 , 50 cm 2 , 60 cm 2 , 65 cm 2 , 70 cm 2 , 72 cm 2 , 80 cm 2 , 85 cm 2 , 90 cm 2 , 100 cm 2 Any value in the above or a range value between any two of them.

[0011] In some embodiments of the present invention, the porous copper substrate is selected from at least one of copper foam, copper mesh, and copper felt.

[0012] In the second aspect of the present invention, a method for preparing any of the foregoing catalytic electrode materials of the present invention is provided, including:

[0013] S1. Electrochemically oxidize the porous copper substrate in an electrolyte solution at a temperature of 60°C to 80°C to obtain a catalytic electrode precursor with cupric oxide nanosheets grown on its surface;

[0014] S2. Electrochemically reduce the catalytic electrode precursor to obtain a catalytic electrode material.

[0015] According to the method for preparing the catalytic electrode material in the embodiments of the present invention, it has at least the following beneficial effects: The preparation method uses a porous copper substrate to perform electrochemical oxidation treatment in a high-temperature electrolyte solution at 60°C to 80°C to generate cupric oxide nanosheets on the surface of the porous copper substrate, and then performs electrochemical reduction treatment to obtain a catalytic electrode material with copper nanosheets loaded and grown on the surface of the porous copper substrate. The catalytic electrode material prepared by the above method can expose sufficient active sites and have a high grain boundary density, can improve the activity of electrochemically reducing nitrate and / or nitrite, can be applied to electrocatalytic reduction of nitrate and / or nitrite to ammonia, or electrocatalytic reduction of nitrate and / or nitrite to remove nitrate and / or nitrite in wastewater, can improve the NH3 Faraday efficiency and partial current density, and thus can improve the ammonia production rate or the removal efficiency of nitrate / nitrite.

[0016] Among them, during the electrochemically oxidative treatment, the temperature of the electrolyte can be controlled to any value or the range value of any two of 60°C, 62°C, 65°C, 67°C, 68°C, 70°C, 72°C, 74°C, 75°C, 76°C, 78°C, 79°C, 80°C.

[0017] In some embodiments of the present invention, the electrolyte is an alkaline solution; for example, the electrolyte can be at least one of potassium hydroxide solution and sodium hydroxide solution.

[0018] In some embodiments of the present invention, the electrochemically oxidative treatment is carried out by chronopotentiometry for oxidation; the oxidation current density of the electrochemically oxidative treatment is 20 mA·cm -2 ~65 mA·cm -2 , and / or the oxidation time of the electrochemically oxidative treatment is 10 min to 30 min. For example, the oxidation current density can be 20 mA·cm -2 , 23 mA·cm -2 , 25 mA·cm -2 , 26 mA·cm -2 , 28 mA·cm -2 , 30 mA·cm -2 , 32 mA·cm -2 , 35 mA·cm -2 , 38 mA·cm -2 , 40 mA·cm -2 , 43 mA·cm -2 , 45 mA·cm -2 , 47 mA·cm -2 , 50 mA·cm -2 , 54 mA·cm -2 , 55 mA·cm -2 , 57 mA·cm -2 , 60 mA·cm -2 , 62 mA·cm -2 , 63 mA·cm -2 , 65 mA·cm -2 Any value or the range value of any two of them. The oxidation time can be any value or the range value of any two of 10 min, 12 min, 14 min, 15 min, 17 min, 20 min, 23 min, 25 min, 28 min, 30 min.

[0019] In some embodiments of the invention, the electrochemically oxidative treatment is completed by a three-electrode system, specifically with the porous copper substrate as the working electrode, a platinum sheet or graphite as the counter electrode, and mercury / mercuric oxide as the reference electrode.

[0020] In some embodiments of the present invention, the electrochemically reduction treatment satisfies at least one of the following conditions:

[0021] The electrolyte used in the electrochemically reduction treatment is selected from any one of a mixed solution of potassium hydroxide and potassium nitrate, a potassium hydroxide solution, and a sodium hydroxide solution;

[0022] The electrochemically reduction treatment uses any one of linear voltammetry, chronopotentiometry, and chronoamperometry;

[0023] The electrode system used in the electrochemically reduction treatment is a three-electrode system or a two-electrode system.

[0024] In a third aspect of the present invention, there is provided an application of any one of the foregoing catalytic electrode materials of the present invention or a catalytic electrode material prepared by the preparation method of any one of the foregoing catalytic electrode materials of the present invention in electrocatalytic reduction of nitrate and / or nitrite to ammonia, or removal of nitrate and / or nitrite in wastewater.

[0025] In some embodiments of the present invention, the wastewater is wastewater containing nitrate and / or nitrite, including at least one of industrial wastewater, agricultural wastewater, and livestock wastewater.

[0026] In a fourth aspect of the present invention, there is provided a wastewater treatment device, which is configured to at least treat wastewater containing nitrate and / or nitrite; the wastewater treatment device includes an electrolysis device, and the electrolysis device includes an anode, a cathode, and an ion exchange membrane; the ion exchange membrane is clamped between the anode and the cathode for separating the anode and the cathode; the cathode is made of any one of the foregoing catalytic electrode materials of the present invention or a catalytic electrode material prepared by the preparation method of any one of the foregoing catalytic electrode materials of the present invention.

[0027] In the above wastewater treatment device, the cathode is made of the foregoing catalytic electrode material of the present invention or a catalytic electrode material prepared by the preparation method of the catalytic electrode material. This catalytic electrode material can electrocatalytically reduce nitrate and / or nitrite, and has a sufficient number of exposed active sites and a high grain boundary density, which can improve the activity of electrochemically reducing nitrate and / or nitrite. When used for treating wastewater containing nitrate and / or nitrite, it can improve the Faraday efficiency and partial current density of NH3, and thus has a high ammonia production rate or nitrate / nitrite removal efficiency.

[0028] In some embodiments of the present invention, the anode is configured to be in contact with an alkaline solution during the wastewater treatment process, and the cathode is configured to be in contact with the wastewater to be treated during the wastewater treatment process.

[0029] In some embodiments of the present invention, both the anode and the cathode are sheet electrodes.

[0030] In some embodiments of the present invention, the electrolysis device further includes an electrode substrate, which includes a first substrate and a second substrate arranged opposite to each other; the first substrate is attached to the anode, and a first flow channel is formed between the first substrate and the anode; the second substrate is attached to the cathode, and a second flow channel is formed between the second substrate and the cathode. Among them, the first flow channel is generally configured to at least accommodate and transport an alkaline solution, and the alkaline solution includes but is not limited to potassium hydroxide solution and sodium hydroxide solution; the second flow channel is configured to at least accommodate and transport the wastewater to be treated.

[0031] During the sewage treatment process, the alkaline solution is transported into the first flow channel and contacts the anode, while the wastewater is transported into the second flow channel and contacts the cathode. A voltage is applied between the anode and the cathode, and nitrate and / or nitrite in the wastewater in the second flow channel are electrocatalytically reduced by the catalytic electrode material serving as the cathode to produce ammonia.

[0032] In some embodiments of the present invention, the first substrate and the second substrate are conductive substrates.

[0033] In some embodiments of the present invention, the first substrate and the second substrate are insulating substrates.

[0034] In some embodiments of the present invention, the first substrate has a first inlet and a first outlet communicating with the first flow channel; and the electrolysis device further includes a gas-liquid separation device, which is connected to the first outlet.

[0035] In some embodiments of the present invention, the electrolysis device further includes an alkali solution storage container, which is connected to the first inlet.

[0036] In some embodiments of the present invention, there is a liquid reflux component between the gas-liquid separation device and the alkali solution storage container.

[0037] In some embodiments of the present invention, the wastewater treatment device is a wastewater ammonia production device, that is, the wastewater treatment device is configured to treat wastewater to produce ammonia, specifically by electrocatalytically reducing nitrate and / or nitrite in the wastewater to produce ammonia.

[0038] In some embodiments of the present invention, the wastewater treatment device further includes an ammonia recovery device, which is configured to recover ammonia produced by the electrochemical reduction of nitrate and / or nitrite in the wastewater during the wastewater treatment process.

[0039] In some embodiments of the present invention, the ammonia recovery device is connected to the second flow channel and is configured to recover ammonia gas generated by the electrochemical reduction of nitrates and / or nitrites in the wastewater in the second flow channel during the wastewater treatment process. Through the setting of the ammonia recovery device, the wastewater treatment device can realize the preparation and recovery of high-value-added ammonia products.

[0040] In some embodiments of the present invention, the second housing has a second inlet and a second outlet communicating with the second flow channel; and the ammonia recovery device includes a membrane contactor, and the membrane contactor has a liquid inlet, a gas inlet, and a liquid outlet. The gas inlet is connected to the second outlet, the liquid inlet and the gas inlet are provided at the same end of the membrane contactor, and the liquid outlet is provided at the other end of the membrane contactor. Among them, the liquid inlet is configured to be the inlet for the absorption liquid, and the absorption liquid generally can be an acid solution, such as hydrochloric acid solution, etc.

[0041] In some embodiments of the present invention, the membrane contactor has a third channel inside, and the gas inlet, the liquid inlet, and the liquid outlet all communicate with the third channel.

[0042] During the wastewater treatment process, the wastewater enters the second channel through the second inlet, and ammonia gas is generated by electrocatalytic reduction of nitrates and / or nitrites in the wastewater by the cathode catalytic electrode material. The absorption liquid is introduced into the membrane contactor through the liquid inlet, and the ammonia gas enters the membrane contactor through the second outlet and is absorbed by the absorption liquid to achieve ammonia recovery.

[0043] In some embodiments of the present invention, the membrane contactor further has a gas outlet, and the gas outlet and the liquid outlet are provided at the same end of the membrane contact reactor; through the setting of the gas outlet, the unabsorbed ammonia gas is discharged from the membrane contactor.

[0044] Furthermore, the gas inlet of the membrane contactor is provided at the bottom end of the membrane contactor, and the gas outlet can be provided at the top end of the membrane contactor relative to the gas inlet to facilitate the discharge of gas; furthermore, the liquid inlet is provided near the gas inlet at one end of the membrane contactor; the liquid outlet is provided near the gas outlet at the other end of the membrane contactor.

[0045] In some embodiments of the present invention, the wastewater treatment device further includes a pretreatment device, which is configured to perform pretreatment on the wastewater to be treated, and the pretreatment includes at least one of alkalization treatment and filtration treatment. Through the setting of the pretreatment device, the load of subsequent processes can be reduced, the concentration of metal impurity ions in the wastewater can be reduced, the dissolved pH value can be adjusted, the efficiency of the electrochemical reduction reaction in the electrolysis device can be improved, and thus the wastewater treatment efficiency can be improved.

[0046] In some embodiments of the present invention, the pretreatment device is connected to the electrolysis device; further, the pretreatment device communicates with the second channel.

[0047] In some embodiments of the present invention, the pretreatment device includes an alkalization device, and the alkalization device communicates with the second channel.

[0048] In some embodiments of the present invention, the gas outlet of the membrane contactor communicates with the alkalization device, so as to realize the recycling of the unabsorbed ammonia gas in the membrane contactor.

[0049] In some embodiments of the present invention, the pretreatment device further includes a wastewater storage device, and the wastewater storage device is connected to the alkalization device and is configured to store the wastewater to be treated.

[0050] In some embodiments of the present invention, the wastewater treatment device further includes a purified water storage device, and the purified water storage device is connected to the second outlet of the electrolysis device and is configured to accommodate and store the effluent treated by the electrolysis device.

[0051] In some embodiments of the present invention, the wastewater treatment device further includes a power supply device, and the power supply device is configured to at least supply power between the anode and the cathode. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention will be further described below with reference to the drawings and embodiments, wherein:

[0053] Figure 1 It is a schematic diagram of the preparation principle of the catalytic electrode material in Example 1;

[0054] Figure 2 It is a scanning electron microscope image of copper foam in Example 1;

[0055] Figure 3 It is a scanning electron microscope image of copper oxide nanosheets grown on the surface of the catalytic electrode precursor in Example 1;

[0056] Figure 4 It is a scanning electron microscope image of the catalytic electrode material prepared in Example 1;

[0057] Figure 5 It is a high-resolution transmission electron microscope image of the catalytic electrode materials prepared in Example 1 and Comparative Example 1;

[0058] Figure 6 It is a linear sweep voltammetry curve and ammonia production performance diagram of the catalytic electrode materials prepared in Example 1 and Comparative Example 1;

[0059] Figure 7Linear sweep voltammograms of the catalytic electrode material prepared in Example 1 in 1 M KOH solution containing 0.1 M KNO2, 1 M KOH electrolyte containing 0.1 M KNO3, and 1 M KOH electrolyte under a three-electrode system;

[0060] Figure 8 Linear sweep voltammograms of the catalytic electrode materials prepared in Examples 2, 3, and 4;

[0061] Figure 9 Physical photos of the copper foam and the catalytic electrode material with copper oxide nanosheets grown on the surface in Example 5, and physical photos of the copper foam, the catalytic electrode material with copper oxide nanosheets grown on the surface, and the catalytic electrode material with copper nanosheets grown on the surface in Example 6;

[0062] Figure 10 Linear sweep voltammograms of the catalytic electrode material prepared in Example 5 in 1 M KOH electrolyte containing 0.01 - 0.5 M KNO3 under a three-electrode system;

[0063] Figure 11 Schematic structural diagram of the wastewater treatment device in Example 7;

[0064] Figure 12 Linear sweep voltammogram of the wastewater treatment device during operation in Example 7;

[0065] Figure 13 Scanning electron micrograph of the catalytic electrode material prepared in Comparative Example 1;

[0066] Figure 14 Scanning electron micrograph of the catalytic electrode material prepared in Comparative Example 2;

[0067] Figure 15 Linear sweep voltammogram of the catalytic electrode material prepared in Comparative Example 2. Detailed implementation manners

[0068] The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0069] Example 1

[0070] This example presents a preparation method of a catalytic electrode material. Refer to Figure 1 , which includes the following steps:

[0071] S1. Cut a piece of copper foam material with a thickness of 0.5 mm and an area of 1 cm 2 . The scanning electron microscope images of its surface and cross-section are shown in Figure 2 . As shown in Figure 2 , (a) is the scanning electron microscope image of the surface of copper foam, and (b) is the scanning electron microscope image of the cross-section of copper foam. Adopt a three-electrode system. Specifically, use copper foam as the working electrode, a platinum sheet as the counter electrode, a mercury / mercuric oxide electrode as the reference electrode, and a 3M (i.e., mol / L) potassium hydroxide solution at 70 °C as the electrolyte. Perform electrochemical oxidation treatment using chronopotentiometry, and control the oxidation current density to be 50 mA·cm -2 . The oxidation time is 20 min to obtain a catalytic electrode precursor with copper nanosheets grown on its surface; perform scanning electron microscope characterization on the prepared catalytic electrode precursor, and the results are shown in Figure 3 . As shown in Figure 3 , (a) is the scanning electron microscope image of the surface of the catalytic electrode precursor, and (b) is the scanning electron microscope image of the cross-section of the catalytic electrode precursor; as can be seen from Figure 3 , nanosheet arrays grow on the surface of copper foam.

[0072] S2. Adopt a three-electrode system. Specifically, use the catalytic electrode precursor with copper nanosheets grown on its surface prepared in step S1 as the working electrode, a platinum sheet as the counter electrode, a mercury / mercuric oxide electrode as the reference electrode, and a 1M KOH solution containing 0.1M KNO3 as the electrolyte. Use linear voltammetry scanning method to perform electrochemical reduction treatment in the range of 0.2V vs.RHE to -0.2V vs.RHE at a scanning speed of 5 mV / s to prepare a catalytic electrode material.

[0073] Perform scanning electron microscope characterization on the prepared catalytic electrode material, and the obtained results are shown in Figure 4 . As shown in Figure 4 , (a) is the scanning electron microscope image of the surface of the catalytic electrode material, and (b) is the scanning electron microscope image of the cross-section of the catalytic electrode material. As can be seen from Figure 3 and Figure 4 , after electrochemical reduction treatment, the material retains the morphology of the nanosheets. Furthermore, the product catalytic electrode includes a catalytic electrode substrate and copper nanosheets vertically loaded on the surface of the catalytic electrode substrate, and the catalytic electrode substrate is a copper foam substrate.

[0074] In addition, perform high-resolution transmission electron microscope characterization on the prepared catalytic electrode material, and the obtained results are shown in Figure 5 as shown in (a). Abundant grain boundaries can be observed on the surface of the sample, and the grain boundary density is about 90 μm -1 . As shown in Figure 5 (c), that is, copper nanosheets with rich grain boundaries grow on the surface of the catalytic electrode material.

[0075] The above catalytic electrode materials can be used for electrocatalytic reduction of nitrate and / or nitrite, and can further be applied to electrocatalytic reduction of nitrate and / or nitrite to ammonia, or to remove nitrate and / or nitrite in wastewater through electrocatalytic reduction of nitrate and / or nitrite.

[0076] Furthermore, in order to verify their performance, the electrocatalytic nitrate reduction performance and electrocatalytic nitrite reduction performance of the above-prepared catalytic electrode materials were tested respectively. Specifically, a three-electrode system was adopted, with the prepared catalytic electrode material as the working electrode, a platinum sheet as the counter electrode, and a mercury / mercuric oxide electrode as the reference electrode. Their electrochemical performance was tested in 1M KOH solution, 1M KOH solution containing 0.1M KNO2, and 1M KOH solution containing 0.1M KNO3 respectively. The obtained results are as Figure 6 and Figure 7 shown. It was found through testing that after adding 0.1M KNO3 to 1M KOH, at a potential of -0.2V vs. RHE, a maximum current density of -1.4A·cm -2 could be achieved, as shown in (a) of Figure 6 and Figure 7 ; the Faraday efficiency of NH3 of the catalytic electrode material was about 80%, as shown in (b) of Figure 6 ; the maximum ammonia production rate of the catalytic electrode material was about 2.7mmol·h -1 ·cm -2 . And it can be seen from Figure 7 that after adding 0.1M KNO2 to 1M KOH, at a potential of -0.1V vs. RHE, a maximum current density of -0.9A·cm -2 could be achieved, indicating that the catalytic electrode material has the performance of electrocatalytic reduction of nitrate and nitrite to ammonia.

[0077] Example 2

[0078] This example presents a preparation method of a catalytic electrode material. The difference between this example and Example 1 is that: the thickness of the foam copper material cut in step S1 of this example is 0.3mm and the area is 1cm 2 ; and the oxidation current density of the electrochemical oxidation treatment was adjusted from 50mA·cm -2 in Example 1 to 20mA·cm -2 , and the others are the same as in Example 1, and a catalytic electrode material was prepared.

[0079] The catalytic electrode material includes a catalytic electrode substrate and copper nanosheets vertically loaded on the surface of the catalytic electrode substrate, and the catalytic electrode substrate is a foam copper substrate.

[0080] Using a method similar to that in Example 1, the electrocatalytic nitrate reduction performance of the product catalytic electrode material was tested, and the results are as Figure 8 shown. From Figure 8 the test results shown, at a potential of -0.1 V vs. RHE, a maximum current density of -0.93 A·cm -2 can be achieved.

[0081] Example 3

[0082] In this example, a preparation method of a catalytic electrode material is proposed. The difference between this example and Example 1 is that: the thickness of the foam copper material cut in step S1 of this example is 0.3 mm and the area is 1 cm 2 ; and the oxidation current density of the electrochemical oxidation treatment is adjusted from 50 mA·cm -2 in Example 1 to 30 mA·cm -2 , and the others are the same as in Example 1, and the catalytic electrode material is prepared.

[0083] The catalytic electrode material includes a catalytic electrode substrate and copper nanosheets vertically loaded on the surface of the catalytic electrode substrate, and the catalytic electrode substrate is a foam copper substrate.

[0084] Using a method similar to that in Example 1, the electrocatalytic nitrate reduction performance of the product catalytic electrode material was tested, and the results are as Figure 8 shown. From Figure 8 the test results shown, at a potential of -0.1 V vs. RHE, a maximum current density of -1.1 A·cm -2 can be achieved.

[0085] Example 4

[0086] In this example, a preparation method of a catalytic electrode material is proposed. The difference between this example and Example 1 is that: the thickness of the foam copper material cut in step S1 of this example is 0.3 mm and the area is 1 cm 2 ; and the oxidation current density of the electrochemical oxidation treatment is adjusted from 50 mA·cm -2 in Example 1 to 65 mA·cm -2 , and the others are the same as in Example 1, and the catalytic electrode material is prepared.

[0087] The catalytic electrode material includes a catalytic electrode substrate and copper nanosheets vertically loaded on the surface of the catalytic electrode substrate, and the catalytic electrode substrate is a foam copper substrate.

[0088] Using a method similar to that in Example 1, the electrocatalytic nitrate reduction performance of the product catalytic electrode material was tested, and the results are as Figure 8 shown. From Figure 8As can be seen from the test results shown, at a potential of -0.1V vs. RHE, a maximum current density of -0.9 A·cm -2 can be achieved.

[0089] Examples 5 - 6

[0090] Examples 5 - 6 respectively propose a preparation method of a catalytic electrode material. The difference between them and Example 1 is that: in step S1 of Example 5, the thickness of the foam copper material cut is 0.5 mm and the area is 25 cm 2 , and in step S1 of Example 6, the thickness of the foam copper material cut is 0.5 mm and the area is 100 cm 2 . Others are the same as in Example 1, and the catalytic electrode material is prepared. In Example 5, the physical pictures of the foam copper (CF) in step S1 and the copper oxide nanosheets (CuO) loaded on the surface of the foam copper are as shown in Figure 9 Figure (a); in Example 6, the physical pictures of the foam copper (CF) in step S1, the copper oxide nanosheets (CuO) loaded on the surface of the foam copper, and the copper nanosheets (H-Cu) loaded on the surface of the foam copper after electrochemical reduction in step S2 are as shown in Figure 9 Figure (b).

[0091] The catalytic electrode materials prepared in Examples 5 - 6 include a catalytic electrode substrate and copper nanosheets vertically loaded on the surface of the catalytic electrode substrate. The catalytic electrode substrate is a foam copper substrate.

[0092] Using a method similar to that in Example 1, the electrocatalytic nitrate reduction performance of the catalytic electrode material prepared in Example 5 was tested. Specifically, a three-electrode system was used, with the prepared catalytic electrode material as the working electrode, a platinum sheet as the counter electrode, and mercury / mercuric oxide as the reference electrode. Its electrochemical performance was tested in a 1M KOH solution containing potassium nitrate with different concentrations (0.01M, 0.05M, 0.1M, 0.5M), and the obtained results are as shown in Figure 10 . As can be seen from Figure 10 , within a relatively wide range of potassium nitrate concentrations, this catalytic electrode material has the performance of catalytic nitrate reduction to ammonia.

[0093] Example 7

[0094] This example proposes a wastewater treatment device, the structure of which is as shown in Figure 11 , including a pretreatment device 1, an electrolysis device 2, an ammonia recovery device 3, and a power supply device 4.

[0095] Among them, the pretreatment device 1 includes an alkalization device 11 and a filtration device 12. The alkalization device 11 is configured to alkalize the wastewater. The alkalization device 11 is specifically an alkalization adjustment tank. The alkalization device 11 is connected to the filtration device 12, and the filtration device is used to filter and remove solid impurities in the wastewater. In this embodiment, the pretreatment device 1 further includes a first wastewater storage device 13 and a second wastewater storage device 14. The first wastewater storage device 13 is used to store the original wastewater to be treated, and the first wastewater storage device 13 is connected to the alkalization device 11; the second wastewater storage device 14 is used to store the pretreated wastewater. The filtration device 12 is connected to the second wastewater storage device 14, and the second wastewater storage device 14 is connected to the electrolysis device 2 through a first pump 15. During the treatment process, the wastewater to be treated stored in the first wastewater storage device 13 is successively introduced into the alkalization device 11 and the filtration device 12 for alkalization treatment and filtration treatment. After the pretreatment is completed, it is introduced into the second wastewater storage device, and then pumped to the electrolysis device 2 through the first pump 15 for treatment.

[0096] The electrolysis device 2 includes an electrode substrate, an anode 22, a cathode 23, an ion exchange membrane 24, a gas-liquid separation device 25, and an alkali solution storage container 26. Both the anode 22 and the cathode 23 are sheet electrodes. The ion exchange membrane 24 is disposed between the anode 22 and the cathode 23 and is used to separate the anode 22 and the cathode 23. The cathode 23 uses the catalytic electrode material prepared in Example 1. Figure 11 The structure schematic diagram of the catalytic electrode material is shown by indexing the cathode 23 with a circular dotted line frame. The electrode substrate includes a first substrate 211 and a second substrate 212. The first substrate 211 is attached to the anode 22, and a first flow channel is formed between the first substrate 211 and the anode 22. The first substrate 211 has a first inlet and a first outlet communicating with the first flow channel. The alkali solution storage container 26 is connected to the first inlet on the first substrate 211 through a second pump 27, and the first outlet is connected to the gas-liquid separation device 25. There is a liquid reflux component 27 between the gas-liquid separation device 25 and the alkali solution storage container 26. The second substrate 212 is attached to the cathode 23, and a second flow channel is formed between the second substrate 212 and the cathode 23. The second substrate 212 has a second inlet and a second outlet communicating with the second flow channel. The second inlet is connected to the alkalization device 11, and the second outlet is connected to the ammonia recovery device 3.

[0097] In this embodiment, the first substrate 211 and the second substrate 212 are conductive substrates. During use, the power supply device 4 can be electrically connected to the anode 22 through the first substrate 211 and to the cathode 23 through the second substrate 212, and then supply power to the anode 22 and the cathode 23 through the first substrate 211 and the second substrate 212. In other embodiments, the first substrate 211 and the second substrate 212 can also be insulating substrates. During use, the power supply device 4 can be directly connected or connected to the anode 22 and the cathode 23 of the electrolysis device 2 through other conductive components to supply power between the anode 22 and the cathode 23.

[0098] The ammonia recovery device 3 is configured to recover ammonia gas generated by the electrochemical reduction of nitrates and / or nitrites in the wastewater in the electrolysis device 2 during the wastewater treatment process. The ammonia recovery device 3 includes a membrane contactor 31. The membrane contactor 31 has a liquid inlet 311, a gas inlet 312, a liquid outlet 313, and a gas outlet 314. The gas inlet 312 is connected to the second outlet on the second housing 212 and is configured to be a gas inlet for the ammonia gas generated by the electrochemical reduction of nitrates and / or nitrites in the wastewater in the second flow channel during the wastewater treatment process. To improve the treatment efficiency, the liquid inlet 311 and the gas inlet 312 can be provided at the same end of the membrane contactor 31, and the liquid outlet 313 and the gas outlet 314 are provided at the other end of the membrane contactor 31. The liquid inlet 311 is configured to be a gas inlet for the absorbent liquid. During the wastewater treatment process, the absorbent liquid is introduced into the membrane contactor 31 through the liquid inlet 311, and the ammonia gas generated by the electrolysis device 2 enters the membrane contactor 31 and is absorbed by the absorbent liquid to achieve ammonia recovery. The gas outlet 314 of the membrane contactor 31 is communicated with the alkalization device 11, and the ammonia gas not completely absorbed in the membrane contactor 31 flows out from the gas outlet and enters the alkalization device 11. The power supply device 4 can be used to supply power between the anode 22 and the cathode 23 of the electrolysis device 2. In addition, it can also be used to supply power to the first pump 15 and the second pump 27. The power supply device 4 includes a solar cell 41 and a voltage regulator 42. The solar cell 41 is connected to the anode 22 and the cathode 23 of the electrolysis device 2 through the voltage regulator 42.

[0099] To verify the effect of the wastewater treatment device, in order to investigate the electrocatalytic nitrate reduction performance using the catalytic electrode material prepared in Example 1 as the cathode material, the alkalized and diluted electroplating solution is used in the second channel between the cathode 23 and the second substrate 212 of the above wastewater treatment device, and the potassium hydroxide solution stored in the alkali solution storage container is introduced into the first channel between the anode 22 and the first substrate 211. Power is supplied between the anode 22 and the cathode 23 through the power supply device 4 for electrochemical testing, and the obtained results are as Figure 12 shown. As Figure 12 shown in (a) below, a current of 50 A can be achieved at 7 V. After recovery, 18 grams of ammonium chloride solid product can be prepared. The physical object is as Figure 12 shown in (b) below, and its X-ray diffraction pattern is asFigure 12 as shown in (c) below.

[0100] Comparative Example 1

[0101] This comparative example presents a method for preparing a catalytic electrode material, which is different from that of Example 1 in that: in step S2 of this comparative example, hydrogen thermal reduction is used to prepare the catalytic electrode material, different from the electrochemical reduction method in Example 1, and a nano copper material with fewer grain boundaries is prepared.

[0102] Specifically, the method for preparing the catalytic electrode material in this comparative example includes:

[0103] S1. Prepare a catalytic electrode precursor with copper nanosheets grown on its surface according to the same operation as step S1 in Example 1;

[0104] S2. In an argon atmosphere containing 5% hydrogen, heat-treat the catalytic electrode precursor obtained in step S1 in a tube furnace, heat it to 250°C at a heating rate of 5°C·min -1 , keep it at this temperature for 1 h, and cool it in the furnace to obtain the product catalytic electrode material by reduction.

[0105] The prepared catalytic electrode material was characterized by scanning electron microscopy, and the results are as Figure 13 shown. The catalytic electrode material has a porous structure. In addition, it was characterized by high-resolution transmission electron microscopy, as Figure 5 shown in (b) below. A small number of grain boundaries can be observed on the surface of the sample, and the grain boundary density is about 35 μm -1 , as Figure 5 shown in (c) below. The grain boundary density is significantly less than that of the copper nanosheets in the catalytic electrode material of Example 1 prepared by electrochemical reduction.

[0106] Using a method similar to that in Example 1, the electrocatalytic nitrate reduction performance of the product catalytic electrode material was tested, and the obtained results are as Figure 6 shown. From Figure 6 the test results shown, at a potential of -0.2 V vs. RHE, a maximum current density of -0.9 A·cm -2 can be achieved, as Figure 6 shown in (a) below; the NH3 Faraday efficiency of the catalytic electrode material is about 70%, as Figure 6 shown in (b) below; the maximum ammonia production rate of the catalytic electrode material is about 1.6 mmol·h -1 ·cm -2 .

[0107] Comparing Example 1 and Comparative Example 1, it can be seen that the catalytic electrode material with rich grain boundaries prepared by electrochemical reduction has better electrocatalytic nitrate reduction performance for ammonia production than the catalytic electrode material with fewer grain boundaries obtained by hydrogen thermal reduction.

[0108] Comparative Example 2

[0109] This comparative example presents a preparation method of a catalytic electrode material, which is different from that of Example 1 in that: in the electrochemical oxidation treatment process of step S1, the temperature of the electrolyte potassium hydroxide solution is adjusted from 70 °C in Example 1 to 25 °C, and the others are the same as those in Example 1, and the catalytic electrode material is prepared.

[0110] The obtained catalytic electrode material was characterized by scanning electron microscopy, and the results are as Figure 14 shown. It can be seen from Figure 14 that the surface of the catalytic electrode material presents a nanowire morphology. Furthermore, the catalytic electrode material includes a catalytic electrode substrate and copper nanowires loaded on the surface of the catalytic electrode substrate, and the catalytic electrode substrate is specifically a copper foam substrate.

[0111] Using a method similar to that in Example 1, the electrocatalytic nitrate reduction performance of the product catalytic electrode material was tested, and the results are as Figure 15 shown. It can be seen from the test results shown in Figure 15 that at a potential of -0.2 V vs. RHE, the maximum achievable current density is -0.8 A·cm -2 , which is much lower than the current density that can be achieved by the catalytic electrode material with copper nanosheets with rich grain boundaries grown on the surface in Example 1. It can be seen from this that the unique nanosheet structure on the surface of the catalytic electrode material in Example 1 has better electrocatalytic performance.

[0112] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A catalytic electrode material, characterized in that, It includes a catalytic electrode substrate and copper nanosheets loaded on the surface of the catalytic electrode substrate, and the catalytic electrode substrate is selected from porous copper substrates.

2. The catalytic electrode material according to claim 1, wherein The copper nanosheets are vertically loaded on the surface of the catalytic electrode substrate; and / or, the grain boundary density of the copper nanosheets is 40 μm -1 ~200 μm -1 .

3. The catalytic electrode material according to claim 1, characterized in that, The thickness of the catalytic electrode material is 0.3 mm to 50 mm; and / or, the area of the catalytic electrode material is 0.1 cm 2 to 100 cm 2 .

4. The catalytic electrode material according to any one of claims 1 to 3, characterized in that, The porous copper substrate is selected from at least one of copper foam, copper mesh, and copper felt.

5. The preparation method of the catalytic electrode material according to any one of claims 1 to 4, characterized in that, It includes: S1. Electrochemically oxidize the porous copper substrate in an electrolyte solution at a temperature of 60°C to 80°C to obtain a catalytic electrode precursor with cupric oxide nanosheets grown on the surface; S2. Electrochemically reduce the catalytic electrode precursor to obtain a catalytic electrode material.

6. The preparation method of the catalytic electrode material according to claim 5, wherein The electrochemically oxidative treatment is carried out by chronopotentiometry; the oxidative current density of the electrochemically oxidative treatment is 20 mA·cm -2 ~65 mA·cm -2 , and / or the oxidation time is 10 min to 30 min.

7. The preparation method of the catalytic electrode material according to claim 6, characterized in that, The electrolyte solution is an alkaline solution; and / or, the electrochemically oxidation treatment is completed using a three-electrode system. Specifically, the porous copper substrate is used as the working electrode, a platinum sheet or graphite is used as the counter electrode, and mercury / mercuric oxide is used as the reference electrode.

8. The preparation method of the catalytic electrode material according to claim 5, characterized in that, The electrochemically reduction treatment satisfies at least one of the following conditions: The electrolyte solution used for the electrochemically reduction treatment is selected from any one of a mixed solution of potassium hydroxide and potassium nitrate, a potassium hydroxide solution, and a sodium hydroxide solution; The electrochemically reduction treatment uses any one of linear voltammetry scanning method, chronopotentiometry, and chronoamperometry; The electrode system used for the electrochemically reduction treatment is a three-electrode system or a two-electrode system.

9. Application of the catalytic electrode material according to any one of claims 1 to 4 or the catalytic electrode material prepared by the preparation method of the catalytic electrode material according to any one of claims 5 to 8 in electrocatalytic reduction of nitrate and / or nitrite to ammonia, or removal of nitrate and / or nitrite in wastewater.

10. A wastewater treatment device, characterized in that, The wastewater treatment device is configured to at least treat wastewater containing nitrate and / or nitrite; the wastewater treatment device includes an electrolysis device, and the electrolysis device includes an anode, a cathode, and an ion exchange membrane; the ion exchange membrane is sandwiched between the anode and the cathode and is used to separate the anode and the cathode; the cathode uses the catalytic electrode material according to any one of claims 1 to 4 or the catalytic electrode material prepared by the preparation method of the catalytic electrode material according to any one of claims 5 to 8.

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