Carbon quantum dot / layered bimetallic oxide composite electrode and preparation method and application thereof

Abstract

The invention discloses a carbon quantum dot / layered bimetallic oxide composite electrode and a preparation method and application thereof. The Co / Fe element is utilized to modify the layered bimetallic oxide, and meanwhile, the carbon quantum dots are inserted into the layered structure of the bimetallic oxide to prepare the CoFe-LDO / CQDs with excellent conductivity; and then the CoFe-LDO / CQDs are used as an anode material to be combined with the Ti / Ti4O7 electrode by using a sol-gel method, so that the CoFe-LDO / CQDs-Ti / Ti4O7 electrode is prepared. The electrode not only has high oxygen evolution overpotential, good chemical stability and corrosion resistance, but also has ultrahigh electrocatalytic activity and degradation efficiency. Performance testing is carried out on the leachate, under the condition that the current density is 35 mA / cm < 2 >, after degradation is carried out for 5 h, the COD of the leachate is reduced to 52 mg / L from 9800 mg / L, and NH3-N is reduced to 26 mg / L from 4700 mg / L. Therefore, the prepared carbon quantum dot / layered bimetal oxide composite electrode can be used for deeply treating the landfill leachate, and particularly, the degradation capacity of the carbon quantum dot / layered bimetal oxide composite electrode on refractory organic matters is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical wastewater treatment, and in particular to a carbon quantum dot / layered bimetallic oxide composite electrode and a preparation method and application thereof. Background Art

[0002] Leachate is a potent mixture produced during the decomposition of landfill waste when rainfall or other water sources percolate through the waste materials accumulated in the landfill. The composition of this mixture varies widely, but generally includes dissolved organic matter, inorganic components such as salts and metal ions, and a range of exogenous organic compounds. The organic component, measured by biochemical oxygen demand (BOD) and chemical oxygen demand (COD), indicates the potential impact of the leachate on water bodies, while inorganic macro-components such as ammonia, chlorides, sulfates, and heavy metals such as arsenic, cadmium, chromium, lead, and mercury highlight the toxicological properties of the leachate. In addition, exogenous compounds, including pesticides, pharmaceuticals, and industrial chemicals, add to the complexity of the leachate due to their resistance to degradation and potential for bioaccumulation. The environmental impacts of untreated landfill leachate are far-reaching and widespread. It can seep into groundwater and surface waters, contaminating aquatic ecosystems, wildlife, and human health.

[0003] Therefore, exploring suitable materials and methods to treat landfill leachate is of great significance to protecting the environment and promoting the recycling of water resources. In the field of landfill leachate treatment, there are several technologies that are considered to be more effective. Biochemical treatment technology, including aerobic biological treatment and anaerobic biological treatment. Aerobic biological treatment decomposes organic matter by aerobic microorganisms, while anaerobic biological treatment uses anaerobic microorganisms to decompose organic matter under anaerobic conditions. These methods can effectively remove organic pollutants in sewage. Membrane treatment technology, including microfiltration, ultrafiltration, nanofiltration and reverse osmosis, can effectively separate suspended matter, colloids, bacteria and dissolved organic matter in sewage. Reverse osmosis technology can especially provide high-quality effluent, but the cost is relatively high. Advanced oxidation processes, such as electrocatalytic oxidation, ozone, hydrogen peroxide, ultraviolet light, etc., can be used to decompose refractory organic matter and improve the biodegradability of sewage. Among them, electrocatalytic oxidation can effectively reduce pollutants and has low environmental selectivity. In addition, compared with other advanced oxidation technologies, electrochemical oxidation technology is more efficient and consumes less energy. It can utilize chloride salts in wastewater as electrolytes and effectively mineralize and degrade organic matter without using any chemicals. Summary of the invention

[0004] The purpose of the present invention is to solve the problem of the difficulty in treating the refractory organic matter in the landfill leachate in the prior art, and to provide a carbon quantum dot / layered bimetallic oxide composite electrode and its preparation method and application. The present invention provides a method for preparing a shape-stable anode with excellent catalytic performance, high oxygen evolution potential, and high organic matter removal efficiency. The anode can be used to deeply treat the landfill leachate, especially the degradation of refractory organic matter, and maintain stability during operation. At the same time, no additional reagents are required during the treatment process, and there is no secondary pollution, which provides a new green process for the field of wastewater treatment.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: a method for preparing a carbon quantum dot / layered bimetallic oxide composite electrode, comprising the following steps:

[0006] S1, preparing carbon quantum dots (CQDs) by carbonizing grapefruit peel with concentrated acid;

[0007] S2, using a mixed metal salt and the CQDs in S1 to prepare a layered bimetallic oxide CoFe-LDH / CQDs, wherein the metals in the mixed metal salt are iron and cobalt;

[0008] S3, performing two etching pretreatments on the titanium mesh; the two etchings are as follows: the first etching uses a sodium hydroxide solution with a mass fraction of 40%, and the temperature is maintained at 60° C. for etching for 2 hours; the second etching uses an oxalic acid solution with a mass fraction of 60%, and the temperature is maintained at 80° C. for etching for 2 hours;

[0009] S4. Mix isopropanol and concentrated hydrochloric acid in a volume ratio of 8:1 in a beaker, stir evenly, and then add Ti 4 O 7 and CoFe-LDH / CQDs in S2, and continued stirring for 30 min to obtain a sol-gel; the CoFe-LDH / CQDs and Ti 4 O 7 The mass ratio is 0.3~0.5:1.

[0010] S5, take a clean brush and dip the sol-gel in S4 and evenly apply it on the surface of the titanium mesh pretreated in S3, first place it in a 90°C forced air drying oven for 20 minutes, then transfer it to a 500°C muffle furnace and calcine it for 10 minutes, take it out and wait for it to cool to room temperature before applying it again;

[0011] S6, repeat the brushing-drying-calcining process in S5 for 5 times, and then calcine at 500°C for 2h to form, and repeat the calcination and forming process for at least 15 times to finally obtain a carbon quantum dot / layered bimetallic oxide composite electrode CoFe-LDO / CQDs-Ti / Ti 4 O 7 .

[0012] Preferably, in S1, dried fresh grapefruit peel is taken, ground into powder, pure water twice the weight of the grapefruit peel is added, and stirred for 15 minutes; concentrated sulfuric acid four times the weight of the grapefruit peel is added to the mixture of the grapefruit peel powder and water until it is completely carbonized to obtain carbonized grapefruit peel powder.

[0013] Preferably, the carbonized grapefruit peel powder is filtered and washed, and then an appropriate amount of pure water is added. After ultrasonic dispersion for 30 minutes, hydrothermal treatment is performed in an autoclave, and the temperature is controlled at 180°C-200°C. The heating is performed for 5 hours, and then the suspension is naturally cooled to room temperature after the end; the suspension is then centrifuged at a speed of 12000r / min. After centrifugation for 30 minutes, the supernatant is filtered through a 0.25μm cellulose filter membrane, and dialyzed with deionized water for 24 hours, and the deionized water is replaced every 8 hours; finally, CQDs are obtained by evaporating the solvent and drying.

[0014] Preferably, in S2, 100 mL of deionized water and 25 mg of citric acid are added to the flask, 0.1-0.5 g of the CQDs prepared in S1 are added, and then a mixed alkali solution with a molar concentration of ≤0.6 M is slowly added, the pH is adjusted to 9-11 and maintained, and then a mixed metal salt solution with a molar concentration of ≤0.4 M and the mixed alkali solution are added dropwise at the same time. After the solution is added dropwise, the resulting mixture is transferred to a 100 mL reactor and reacted at 90 ° C for 6 hours; after the reaction is completed and the reactor is cooled to room temperature, the reaction product is taken out, repeatedly rinsed with deionized water, and then freeze-dried to obtain the product CoFe-LDH / CQDs.

[0015] Preferably, cobalt nitrate and ferric nitrate are dissolved in 100 mL of deionized water in a molar ratio of 1-3:1 to prepare the mixed metal salt solution; and the same mass of soda ash and baking soda are dissolved in 100 mL of deionized water to prepare the mixed alkali solution.

[0016] Preferably, in S3, a titanium mesh with a pore size of about 0.2 cm is selected for polishing and grinding, and after removing the surface oxide layer, it is ultrasonically cleaned in ethanol and acetone solutions for 15 minutes in sequence, washed with clean water, dried, and then etched twice.

[0017] The present invention also provides a carbon quantum dot / layered bimetallic oxide composite electrode prepared by the above preparation method, wherein the thickness of the active layer on the titanium mesh surface of the composite electrode is ≥0.5 μm.

[0018] The present invention also provides the use of the above carbon quantum dots / layered bimetallic oxide composite electrode in leachate wastewater treatment, using CoFe-LDO / CQDs-Ti / Ti 4 O 7The electrode is used as the anode, and the titanium sheet of the same size is used as the cathode. The landfill leachate is subjected to electrocatalytic degradation in the electrolytic cell; the current density is controlled to be 35mA / cm 2 , continuous degradation time ≤ 6 hours.

[0019] The beneficial effects of the present invention are:

[0020] 1) The present invention uses Co / Fe elements to modify the layered bimetallic oxide, thereby improving the charge transfer rate and catalytic performance of the material; at the same time, carbon quantum dots are inserted into the layered structure of the bimetallic oxide, and the prepared CoFe-LDO / CQDs have both a stable two-dimensional layered structure and excellent conductive properties. On this basis, the present invention further uses the sol-gel method to use CoFe-LDO / CQDs as an anode material and Ti / Ti 4 O 7 Electrode combination to prepare CoFe-LDO / CQDs-Ti / Ti 4 O 7 electrode.

[0021] 2) CoFe-LDO / CQDs-Ti / Ti prepared by the present invention 4 O 7 Electrode, in Ti / Ti 4 O 7 Based on the electrode, the self-prepared CoFe-LDO / CQDs material is doped to overcome the Ti / Ti 4 O 7 The electrode catalytic efficiency is not enough, and the passivation layer may form on the electrode surface, resulting in activity decay. 4 O 7 The electrode has high oxygen evolution overpotential, good chemical stability and corrosion resistance, as well as ultra-high electrocatalytic activity and degradation efficiency. 4 O 7 The anode was tested for performance with a current density of 35 mA / cm 2 In the case of degradation, after 5 hours, the COD of the leachate decreased from 9800 mg / L to 52 mg / L, and NH 3 -N decreased from 4700mg / L to 26mg / L. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments.

[0023] Example 1

[0024] 1. Preparation of carbon quantum dots using grapefruit peel: Take 10g of dried fresh grapefruit peel, cut it into powder, add pure water twice the weight of grapefruit peel, and stir for 15min. Add 4 times the weight of grapefruit peel powder to the mixture of grapefruit peel powder and water. Concentrated sulfuric acid is added to the mixture of grapefruit peel powder and water until it is completely carbonized. After filtering and washing the carbonized grapefruit peel powder, add an appropriate amount of pure water, ultrasonically disperse it for 30min, and then hydrothermally heat it in an autoclave, control the temperature at 185°C, heat it for 5 hours, and naturally cool it to room temperature after the end. Then centrifuge the suspension, control the speed at 12000r / min, and take the supernatant after centrifugation for 30min. The supernatant is passed through a membrane, filtered through a 0.25μm cellulose filter membrane, and dialyzed with deionized water for 24h, and the deionized water is replaced every 8h. Subsequently, CQDs are obtained by evaporating the solvent and placed in a vacuum drying oven for drying.

[0025] 2. Preparation of layered bimetallic oxides combined with carbon quantum dots: Cobalt nitrate and iron nitrate were dissolved in 100 mL of deionized water in a Co / Fe molar ratio of 1:1 to obtain a mixed salt solution of the two, and the molar concentration of the Co / Fe salt was controlled to be 0.4 M. At the same time, the same mass of soda ash and baking soda were dissolved in 100 mL of deionized water to form a mixed alkali solution with a molar concentration of 0.6 M. Then, 100 mL of deionized water and 25 mg of citric acid were added to the flask, and 0.5 g of the prepared CQDs were added. Then, the mixed alkali solution was slowly added thereto, the pH was adjusted to 9-11, and then the mixed salt and mixed alkali solution were added drop by drop at the same time, and the pH of the solution was kept at about 10. After the solution was added, the resulting mixture was transferred to a 100 mL reactor and reacted at 90 ° C for 6 hours. After the reaction was completed and the reactor was cooled to room temperature, the reaction product was taken out, repeatedly rinsed with deionized water, and then freeze-dried to obtain the product CoFe-LDH / CQDs.

[0026] 3. Preparation of CoFe-LDO / CQDs-Ti / Ti 4 O 7 electrode

[0027] (1) A titanium mesh (20*10*0.1 cm) with a pore size of about 0.2 cm was selected for polishing and grinding. After removing the surface oxide layer, it was ultrasonically cleaned in ethanol and acetone solutions for 15 min in turn, rinsed with clean water, and dried for later use.

[0028] (2) Prepare a sodium hydroxide solution with a mass fraction of 40%, heat and stir it to 60° C., immerse the treated and dried titanium mesh in it, maintain the temperature at 60° C. and etch for 2 hours. After etching, wash with clean water and dry it for later use.

[0029] (3) Prepare a 60% oxalic acid solution, heat and stir it to 80° C., immerse the dried titanium mesh in it, maintain the temperature at 80° C. and etch for 2 hours until the surface of the titanium mesh becomes rough and gray, then wash and dry it for later use.

[0030] (4) Preparation of sol-gel: Mix isopropanol and concentrated hydrochloric acid in a volume ratio of 8:1 in a beaker and stir evenly. Then add the prepared CoFe-LDH / CQDs and Ti 4 O 7 , and continued stirring for 30 min. The addition amount relationship is: CoFe-LDH / CQDs and Ti 4 O 7 The mass ratio is 0.5:1.

[0031] (5) Take a clean brush and dip the prepared sol-gel into the treated titanium mesh surface and evenly apply it. First place it in a 90℃ forced air drying oven for 20 minutes, then transfer it to a 500℃ muffle furnace and calcine it for 10 minutes. Take it out and wait for it to cool to room temperature before applying it again.

[0032] (6) Repeat the brushing-drying-calcining process in step (5) for 5 times, and then calcine at 500°C for 2h to sinter and form. This is a calcination and forming process. After repeating the calcination and forming process 18 times, the thickness of the sintered titanium mesh active layer reaches 0.6 μm, and CoFe-LDO / CQDs-Ti / Ti 4 O 7 electrode.

[0033] The CoFe-LDO / CQDs-Ti / Ti prepared in this example 4 O 7 The electrode is used as the anode, and the titanium sheet of the same size is used as the cathode to perform electrocatalytic degradation of the landfill leachate in the electrolytic cell. The current density is controlled to be 35mA / cm 2 , COD and ammonia nitrogen were tested by sampling every 1 hour of degradation, and the continuous degradation time did not exceed 6 hours. The results are shown in Table 1:

[0034] Table 1 COD and ammonia nitrogen detection data

[0035] 0h 1h 2h 3h 4h 5h 6h <![CDATA[COD / (mgL -1 )]]> 9800 8206 6742 5303 3880 2592 1821 <![CDATA[Ammonia nitrogen / (mgL -1 )]]> 4700 4140 3056 1997 1165 638 441

[0036] Example 2

[0037] The preparation method of this embodiment is the same as that of embodiment 1, except that the molar ratio of Co / Fe in this embodiment is 2:1, and CoFe-LDO / CQDs-Ti / Ti is prepared. 4 O 7 electrode.

[0038] The CoFe-LDO / CQDs-Ti / Ti prepared in this example 4 O 7 The electrode is used as the anode, and the titanium sheet of the same size is used as the cathode to perform electrocatalytic degradation of the landfill leachate in the electrolytic cell. The current density is controlled to be 35mA / cm 2 , COD and ammonia nitrogen were tested by sampling every 1 hour of degradation, and the continuous degradation time did not exceed 6 hours. The results are shown in Table 2:

[0039] Table 2 COD and ammonia nitrogen detection data

[0040] 0h 1h 2h 3h 4h 5h 6h <![CDATA[COD / (mgL -1 )]]> 9800 8000 6212 4327 3006 1814 1132 <![CDATA[Ammonia nitrogen / (mgL -1 )]]> 4700 3914 2892 1790 971 414 247

[0041] Example 3

[0042] The preparation method of this embodiment is the same as that of embodiment 1, except that the molar ratio of Co / Fe in this embodiment is 3:1, and CoFe-LDO / CQDs-Ti / Ti is prepared. 4 O 7 electrode.

[0043] The CoFe-LDO / CQDs-Ti / Ti prepared in this example 4 O 7 The electrode is used as the anode, and the titanium sheet of the same size is used as the cathode to perform electrocatalytic degradation of the landfill leachate in the electrolytic cell. The current density is controlled to be 35mA / cm 2 , COD and ammonia nitrogen were tested by sampling every 1 hour of degradation, and the continuous degradation time did not exceed 6 hours. The results are shown in Table 3:

[0044] Table 3 COD and ammonia nitrogen detection data

[0045]

[0046]

[0047] Example 4

[0048] The preparation method of this embodiment is the same as that of embodiment 1, except that the molar ratio of Co / Fe in this embodiment is 3:1, and the addition amount of CQDS is set to 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g, respectively, to prepare 5 CoFe-LDO / CQDs-Ti / Ti 4 O 7 Electrode samples.

[0049] The five CoFe-LDO / CQDs-Ti / Ti prepared in this example are respectively 4 O 7 The electrode sample was used as the anode, and a titanium sheet of the same size was used as the cathode. 1 mol / L H2 SO 4 , the anode current density is set to 2A / cm 2 , the anode was subjected to an enhanced life test until the voltage exceeded 10V, and the effect of the amount of CQDs added on the anode life was observed and recorded. The results are shown in Table 4:

[0050] Table 4 COD and ammonia nitrogen detection data

[0051] CQDs addition amount / g 0.1 0.2 0.3 0.4 0.5 Strengthening life / h 114 267 390 518 587

[0052] Example 5

[0053] The preparation method of this embodiment is the same as that of embodiment 1, except that the molar ratio of Co / Fe in this embodiment is 3:1, the mass ratio of CoFe-LDH / CQDs to Ti4O7 is 0.3:1, and CoFe-LDO / CQDs-Ti / Ti 4 O 7 electrode.

[0054] The CoFe-LDO / CQDs-Ti / Ti prepared in this example 4 O 7 The electrode is used as the anode, and the titanium sheet of the same size is used as the cathode to perform electrocatalytic degradation of the landfill leachate in the electrolytic cell. The current density is controlled to be 35mA / cm 2 , COD and ammonia nitrogen were tested by sampling every 1 hour of degradation, and the continuous degradation time did not exceed 6 hours. The results are shown in Table 5:

[0055] Table 5 COD and ammonia nitrogen detection data

[0056] 0h 1h 2h 3h 4h 5h 6h <![CDATA[COD / (mgL -1 )]]> 9800 7017 5022 2816 827 330 128 <![CDATA[Ammonia nitrogen / (mgL -1 )]]> 4700 3114 2002 925 337 132 96

[0057] Example 6

[0058] The preparation method of this embodiment is the same as that of embodiment 1, except that the molar ratio of Co / Fe in this embodiment is 3:1, and the molar ratio of CoFe-LDH / CQDs to Ti 4 O 7 The mass ratio of is 0.4:1, and CoFe-LDO / CQDs-Ti / Ti is prepared. 4 O 7 electrode.

[0059] The CoFe-LDO / CQDs-Ti / Ti prepared in this example 4 O 7 The electrode is used as the anode, and the titanium sheet of the same size is used as the cathode to perform electrocatalytic degradation of the landfill leachate in the electrolytic cell. The current density is controlled to be 35mA / cm 2, COD and ammonia nitrogen were tested by sampling every 1 hour of degradation, and the continuous degradation time did not exceed 6 hours. The results are shown in Table 6:

[0060] Table 6 COD and ammonia nitrogen test data

[0061] 0h 1h 2h 3h 4h 5h 6h <![CDATA[COD / (mgL -1 )]]> 9800 6817 4691 2266 701 210 84 <![CDATA[Ammonia nitrogen / (mgL -1 )]]> 4700 3009 1882 838 262 111 61

[0062] Example 7

[0063] The preparation method of this embodiment is the same as that of embodiment 1, except that the molar ratio of Co / Fe in this embodiment is 3:1, and CoFe-LDO / CQDs-Ti / Ti is prepared. 4 O 7 electrode.

[0064] The CoFe-LDO / CQDs-Ti / Ti prepared in this example 4 O 7 The electrode is used as the anode, and the titanium sheet of the same size is used as the cathode to perform electrocatalytic degradation of the landfill leachate in the electrolytic cell. The current density is controlled to be 35mA / cm 2 , COD and ammonia nitrogen were tested by sampling every 1 hour of degradation, and the continuous degradation time did not exceed 6 hours. The results are shown in Table 7:

[0065] Table 7 COD and ammonia nitrogen test data

[0066] 0h 1h 2h 3h 4h 5h 6h <![CDATA[COD / (mgL -1 )]]> 9800 6507 4317 1916 410 113 52 <![CDATA[Ammonia nitrogen / (mgL -1 )]]> 4700 2877 1572 581 178 88 26

[0067] The description of the present invention is considered to be illustrative rather than restrictive. Based on the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features according to the disclosed technical content without creative labor, all of which are within the protection scope of the present invention.

Claims

1. A method for preparing a carbon quantum dot / layered bimetallic oxide composite electrode, characterized in that: The following steps are involved: S1, preparing carbon quantum dots (CQDs) by carbonizing grapefruit peel with concentrated acid; S2, using a mixed metal salt and the CQDs in S1 to prepare a layered bimetallic oxide CoFe-LDH / CQDs, wherein the metals in the mixed metal salt are iron and cobalt; S3, performing two etching pretreatments on the titanium mesh; the two etchings are as follows: the first etching uses a sodium hydroxide solution with a mass fraction of 40%, and the temperature is maintained at 60° C. for etching for 2 hours; the second etching uses an oxalic acid solution with a mass fraction of 60%, and the temperature is maintained at 80° C. for etching for 2 hours; S4, take isopropanol: concentrated hydrochloric acid in a volume ratio of 8:1 and mix them in a beaker, stir evenly, then add Ti4O7 and CoFe-LDH / CQDs in S2 into the beaker, continue stirring for 30 minutes, and prepare a sol-gel; the mass ratio of the CoFe-LDH / CQDs to Ti4O7 is 0.3-0.5:

1. S5, take a clean brush and dip the sol-gel in S4 and evenly apply it on the surface of the titanium mesh pretreated in S3, first place it in a 90°C forced air drying oven for 20 minutes, then transfer it to a 500°C muffle furnace and calcine it for 10 minutes, take it out and wait for it to cool to room temperature before applying it again; S6. Repeat the brushing-drying-calcination process in S5 for 5 times, and then calcine at 500°C for 2 hours to form. The calcination and forming process is repeated at least 15 times to finally obtain a carbon quantum dot / layered bimetallic oxide composite electrode CoFe-LDO / CQDs-Ti / Ti4O7.

2. The preparation method according to claim 1, characterized in that: In S1, fresh dried grapefruit peel is taken and ground into powder, and pure water twice the weight of the grapefruit peel is added and stirred for 15 minutes; concentrated sulfuric acid four times the weight of the grapefruit peel is added to the mixture of the grapefruit peel powder and water until it is completely carbonized to obtain carbonized grapefruit peel powder.

3. The preparation method according to claim 2, characterized in that: The carbonized grapefruit peel powder was filtered and washed, and then an appropriate amount of pure water was added. After ultrasonic dispersion for 30 minutes, hydrothermal treatment was performed in an autoclave, and the temperature was controlled at 180°C-200°C. The mixture was heated for 5 hours and then naturally cooled to room temperature. The suspension was then centrifuged at a speed of 12000 r / min. After centrifugation for 30 minutes, the supernatant was filtered through a 0.25 μm cellulose filter membrane and dialyzed with deionized water for 24 hours, with the deionized water replaced every 8 hours. Finally, the CQDs were obtained by evaporating the solvent and dried.

4. The preparation method according to claim 1, characterized in that: In S2, 100 mL of deionized water and 25 mg of citric acid are added to the flask, 0.1-0.5 g of the CQDs prepared in S1 are added, and then a mixed alkali solution with a molar concentration of ≤0.6 M is slowly added, the pH is adjusted to 9-11 and maintained, and then a mixed metal salt solution with a molar concentration of ≤0.4 M and the mixed alkali solution are added dropwise at the same time. After the solution is added dropwise, the resulting mixture is transferred to a 100 mL reactor and reacted at 90° C. for 6 hours; after the reaction is completed and the reactor is cooled to room temperature, the reaction product is taken out, repeatedly rinsed with deionized water, and then freeze-dried to obtain the product CoFe-LDH / CQDs.

5. The preparation method according to claim 4, characterized in that: Cobalt nitrate and ferric nitrate are dissolved in 100 mL of deionized water at a molar ratio of 1-3:1 to prepare the mixed metal salt solution; and the same mass of soda ash and baking soda are dissolved in 100 mL of deionized water to prepare the mixed alkali solution.

6. The preparation method according to claim 1, characterized in that: In S3, a titanium mesh with a pore size of about 0.2 cm is selected for polishing and grinding. After removing the surface oxide layer, it is ultrasonically cleaned in ethanol and acetone solutions for 15 minutes, washed with clean water, dried, and etched twice.

7. The carbon quantum dot / layered bimetallic oxide composite electrode prepared by the preparation method according to claims 1-6, characterized in that: The thickness of the active layer on the titanium mesh surface of the composite electrode is ≥0.5 μm.

8. The use of the carbon quantum dot / layered bimetallic oxide composite electrode in leachate wastewater treatment as claimed in claim 7, characterized in that: Using CoFe-LDO / CQDs-Ti / Ti4O7 electrode as anode and titanium sheet of the same size as cathode, the landfill leachate was electrocatalytically degraded in an electrolytic cell; the current density was controlled at 35 mA / cm 2 , continuous degradation time ≤ 6 hours.

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