A nitrite sensing electrode based on copper oxide / cerium dioxide heterostructure, preparation method and application thereof

Abstract

A nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure, a preparation method and its application belong to the field of electrochemical sensing technology. First, dense and uniform copper nanoparticles are electroplated on a carbon cloth substrate using a constant potential method to obtain a copper-plated carbon cloth; secondly, the copper-plated carbon cloth is immersed in an alkaline oxidizing solution for a certain period of time to obtain a carbon cloth modified with p-type copper oxide nanoflowers; then, n-type cerium dioxide nanosheets are further electrodeposited on the carbon cloth modified with copper oxide nanoflowers using a constant current method; and a p-n heterostructure sensing electrode of cerium dioxide nanosheets / copper oxide nanoflowers / carbon cloth is obtained by high-temperature annealing. The sensing electrode obtained by the present invention is applied as a working electrode to construct an electrochemical sensing platform for detecting the content of nitrite. The nitrite electrochemical sensing electrode prepared by the present invention has excellent detection performance for nitrite, high sensitivity, wide linear range, low detection limit and excellent stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensing, and in particular relates to a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure, a preparation method and applications thereof. Background Art

[0002] Nitrite is a vital component of the nitrogen cycle. With the development of human society, the increasing use of nitrogen fertilizers in agricultural production and the discharge of domestic and industrial wastewater have led to a continuous increase in nitrite content in soil and water. However, high nitrite concentrations can disrupt the balance of aquatic ecosystems, leading to eutrophication and harmful algal blooms, resulting in the death of aquatic plants and animals. Therefore, nitrite concentration is an important indicator for assessing water health and ecosystem balance, and quantitative nitrite detection has a positive impact on ecosystem and environmental protection. In recent years, several mature nitrite detection methods have been developed, such as colorimetry, fluorescence, spectrophotometry, ion chromatography, mass spectrometry, and electrophoresis. However, these methods are limited by the large size of the detection equipment, high cost, complex operation, the need for specialized personnel, and the use of toxic reagents, which have hindered their widespread application. Electrochemical sensing methods, on the other hand, offer advantages such as miniaturization, portability, ease of operation, and rapid response, and hold the promise of on-site detection in various environments and widespread application, thus attracting close attention from researchers.

[0003] The detection performance of electrochemical nitrite sensors is mainly dominated by the capabilities of the sensing electrode. Existing glassy carbon electrodes require the use of additional binders and conductive additives when loading active materials, which will significantly increase the interfacial impedance of the sensing electrode and affect its electron transfer capacity. Moreover, the sensing performance of the sensing electrode is poor, the stability is low, and the parameters such as sensitivity, detection limit, and detection range are difficult to meet the high requirements in practical applications. In addition, due to the inherent strong oxidizing property of nitrite, when it is oxidized by electrochemical methods, it is usually necessary to provide a larger detection potential, which makes the overpotential of nitrite electrochemical sensors high, which is not conducive to popularization and widespread application.

[0004] Carbon cloth (CC), a three-dimensional structure woven from carbon fibers, exhibits excellent mechanical stability, acid and alkali resistance, high orientation, and a large surface area. Therefore, it is suitable for use as a substrate electrode in nitrite sensors, avoiding the increased interfacial impedance of the sensor electrode caused by the use of additional binders and conductive additives. P-type metal oxide semiconductors and n-type metal oxide semiconductors can couple with each other, forming a pn heterostructure at their interface. Electron / hole transfer occurs between the two metal oxides, thereby improving charge transfer efficiency and catalytic activity. Copper oxide (CuO) is a typical p-type semiconductor catalyst with a narrow bandgap (1.2-1.7 eV) and is widely used in electrochemical sensing due to its excellent electrochemical and catalytic properties. However, CuO is typically grown in agglomerated form on a free-standing substrate, which reduces the exposed electrochemically active area and hinders heterojunction formation and the occurrence of redox reactions. Research has shown that by regulating the morphology of CuO, its electrochemical sensing properties can be effectively controlled. As an important rare earth oxide, cerium dioxide (CeO2) is an n-type wide bandgap (2.58-3.20eV) semiconductor with good interface compatibility with other materials, which helps to build a stable and efficient heterojunction structure. In addition, one of the most notable characteristics of cerium dioxide is its high oxygen storage capacity, which is due to its ability to store oxygen in CeO2. 4+ and Ce 3+ Reversible redox transitions can easily occur between the two states. This excellent redox property helps promote charge separation and transfer in the heterojunction and improve the electrocatalytic performance.

[0005] Therefore, in order to meet the requirements of nitrite detection in practical applications, it is of great significance to develop a high-performance nitrite electrochemical sensing electrode based on a heterostructure of p-type copper oxide and n-type ceria. Summary of the Invention

[0006] The purpose of the present invention is to provide a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure, a preparation method and its application. The sensing electrode is based on a three-dimensional cerium dioxide nanosheet / copper oxide nanoflower heterostructure modified carbon cloth to solve the problems of insufficient sensitivity and large overpotential of nitrite electrochemical sensors that are not conducive to practical applications.

[0007] The first aspect of the present invention is to provide a method for preparing a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure, the steps of which are as follows:

[0008] (1) Electroplating copper nanoparticles on carbon cloth: A mixed aqueous solution of copper chloride, sodium citrate, and urea was prepared as an electroplating solution; copper was plated using a constant potential method, and a carbon cloth was used as a working electrode and placed in the electroplating solution. A certain voltage was applied to the carbon cloth for a period of time; after the electroplating was completed, the carbon cloth was rinsed and dried to obtain Cu NPs / CC;

[0009] (2) Alkali-assisted oxidation to obtain copper oxide nanoflowers: prepare a mixed aqueous solution of ammonium persulfate and sodium hydroxide, and soak the Cu NPs / CC obtained in step (1) in it for a period of time; after the alkali-assisted oxidation reaction is completed, rinse and dry to obtain CuO NFs-AO / CC;

[0010] (3) Electrodeposition of cerium dioxide nanosheets: Prepare a mixed aqueous solution of cerium nitrate, ammonium acetate and sodium chloride as an electrodeposition solution; Electrodeposition is performed using a constant current method, and the CuO NFs-AO / CC obtained in step (2) is used as a working electrode and placed in the electrodeposition solution. After heating it to a set temperature, a certain constant current is applied to it for a period of time; After the electrodeposition is completed, rinse it clean and dry it to obtain CeO2 NSs / CuO NFs-AO / CC;

[0011] (4) High-temperature annealing: The CeO2 NSs / CuO NFs-AO / CC obtained in step (3) is placed in a muffle furnace and annealed at a certain temperature for a certain period of time; after the annealing is completed, it is naturally cooled to room temperature to obtain the nitrite electrochemical sensing electrode based on the copper oxide / cerium dioxide heterostructure (CeO2 NSs / CuO NFs / CC).

[0012] Preferably, in the mixed aqueous solution of step (1), the concentration of copper chloride is 5 to 25 mmol / L, the concentration of sodium citrate is 0.05 to 0.20 mol / L, and the concentration of urea is 0.05 to 0.20 mol / L; the voltage of the constant potential is -0.55 to -0.85 V, and the duration is 0.5 to 2 hours;

[0013] Preferably, the concentration of ammonium persulfate in the mixed aqueous solution in step (2) is 0.04-0.08 mol / L, and the concentration of sodium hydroxide is 1.0-1.5 mol / L; the soaking time is 15-120 minutes;

[0014] Preferably, the concentration of cerium nitrate in the mixed aqueous solution in step (3) is 8-12 mmol / L, the concentration of ammonium acetate is 0.05-0.15 mol / L, and the concentration of sodium chloride is 0.02-0.08 mol / L; the set temperature is 40-90° C., the applied current is 0.0005-0.0015 A, and the duration is 10-60 min;

[0015] Preferably, in step (4), the annealing temperature is 350-450° C., and the annealing time is 1.5-3.0 hours.

[0016] The second aspect of the present invention is to provide a nitrite electrochemical sensor electrode based on a copper oxide / cerium dioxide heterostructure prepared by the above preparation method.

[0017] The third aspect of the present invention is to provide an application of a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure in electrochemical detection of nitrite, the steps of which are as follows:

[0018] (1) The CeO2 NSs / CuO NFs / CC nitrite electrochemical sensing electrode prepared by the present invention was used as the working electrode, a platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. A certain concentration of sodium nitrite standard solution was added and electrochemical testing was performed in a phosphate buffer solution with a concentration of 0.1 mol / L and a pH of 7;

[0019] (2) The sensitivity and linearity tests of nitrite were performed using chronoamperometry and cyclic voltammetry, and the relationship between the obtained response current and nitrite concentration was fitted to obtain the linear relationship of the response.

[0020] The beneficial effects of the present invention are:

[0021] 1. This invention develops a unique three-dimensional heterojunction nanocomposite material by synthesizing copper oxide nanoflowers on copper-coated carbon cloth and then growing cerium dioxide nanosheets. The copper oxide nanoflowers promote the growth of cerium dioxide and optimize its morphology. This design solves the common agglomeration problem, provides a larger specific surface area and more active sites. In addition, the pn heterojunction effectively improves carrier mobility, CeO2 3+ The results show that the catalytic activity of the nanostructured carbon nanotubes is significantly improved, and the oxygen vacancy content is increased, thereby enhancing the electrocatalytic activity. It also promotes more efficient carrier separation and interfacial charge transfer, thereby reducing the electron transfer impedance and improving the electron transfer efficiency and electrochemical sensing performance.

[0022] 2. The nitrite sensing electrode based on the copper oxide / cerium dioxide heterostructure of the present invention has excellent detection performance for nitrite, high sensitivity, wide linear range, low detection limit and excellent stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 (a) and Figure 1 (b) is the SEM image of Cu NPs / CC prepared in Example 1 at different magnifications. Figure 1 (c) and Figure 1 (d) is the SEM image of CuO NFs-AO / CC prepared in Example 1 at different magnifications. Figure 1 (e) and Figure 1 (f) is the SEM image of CeO2NSs / CuO NFs / CC prepared in Example 1 at different magnifications.

[0024] Figure 1 (a) and Figure 1 (b) shows that after copper is electroplated on the carbon cloth substrate, copper nanoparticles with a size of approximately 100 nm are densely and uniformly grown on the carbon cloth surface, thereby obtaining Cu NPs / CC. Figure 1 (c) and Figure 1 (d) shows that after alkali-assisted oxidation, the original copper nanoparticles react with (NH4)2S2O8 and NaOH, and the copper nanoparticles are gradually consumed and reconstructed, eventually generating copper oxide with a three-dimensional nanoflower morphology composed of thin nanosheets, which is tightly and evenly loaded on the carbon cloth, thereby obtaining CuONFs-AO / CC. Figure 1 (e) and Figure 1 (f) shows that after further electrodeposition of ceria, CeO2 nanosheet arrays with a thickness of about 40 nm grow vertically on the surface of CuO NFs / CC in a maze-like morphology, thereby obtaining CeO2 NSs / CuO NFs / CC.

[0025] Figure 2 X-ray diffraction (XRD) patterns of carbon cloth (CC) and CeO2 NSs / CuO NFs / CC prepared in Example 1.

[0026] Figure 2 The results showed that the CeO2 NSs / CuO NFs / CC sensing electrode prepared in Example 1 exhibited characteristic peaks belonging to carbon cloth as well as characteristic peaks belonging to copper oxide and cerium dioxide, respectively, proving the successful synthesis of CeO2 NSs / CuO NFs / CC.

[0027] Figure 3 These are the cyclic voltammetry test curves of CeO2 NSs / CuO NFs / CC prepared in Example 1, CeO2NSs / CuO NFs / CC-0.0005A prepared in Example 2, CeO2 NSs / CuO NFs / CC-60min prepared in Example 3, and CeO2 NSs / CuO NFs / CC-60℃ prepared in Example 4 to nitrite.

[0028] Figure 3 The test results show that the sensing electrodes prepared in Examples 1, 2, 3, and 4 all exhibit response characteristics to nitrite, showing obvious oxidation peaks belonging to nitrite at a potential of approximately 0.74 to 0.75 V, and the peak current of the oxidation peak of CeO2 NSs / CuO NFs / CC prepared in Example 1 is the largest.

[0029] Figure 4 (a) is the chronoamperometric test curve of CeO2 NSs / CuO NFs / CC prepared in Example 1 for nitrite in the concentration range of 0.1 to 4000 μM. Figure 4(b) is through Figure 4 (a) The linear equation obtained by fitting different concentrations of nitrite and their corresponding current responses. Figure 4 (c) and Figure 4 (d) Figure 4 (a) and Figure 4 (b) Enlarged view of the marked part.

[0030] Figure 4 The test results of (a) show that when nitrite ions are added, the current intensity first increases sharply, and then gradually stabilizes after reaching the maximum value. The current intensity generally shows a step-like increase. Figure 4 (b) and Figure 4 The results of (d) show that the nitrite concentration range of 0.1 to 4000 μM has a good piecewise linear relationship with the current intensity. In the concentration range of 0.1 to 10 μM, the linear equation is y = 0.01161x + 0.04258 (R 2 =0.997), the corresponding sensitivity is 11610μAmM -1 cm -2 In the concentration range of 10 to 1000 μM, the linear equation is y = 3.581x + 0.183 (R 2 =0.997), the corresponding sensitivity is 3581μAmM -1 cm -2 In the concentration range of 1000-4000 μM, the linear equation is y=1.928x+1.900(R 2 =0.999), the corresponding sensitivity is 1928μAmM -1 cm -2 The parameter y represents the current intensity, and the parameter x represents the nitrite concentration. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the implementation methods of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure, comprising the following steps:

[0034] (1) Electroplating of copper nanoparticles on carbon cloth: A mixed aqueous solution containing 15 mmol / L copper chloride, 0.1 mol / L sodium citrate, and mol / L urea was prepared as the electroplating solution. Copper was plated using a constant potential method. The carbon cloth was used as the working electrode and placed in the electroplating solution. A voltage of -0.7 V was applied to it and the electroplating was continued for 1 hour. After the electroplating was completed, it was rinsed with deionized water and dried at 60°C to obtain Cu NPs / CC.

[0035] (2) Alkali-assisted oxidation to obtain copper oxide nanoflowers: Prepare a mixed aqueous solution containing 0.06 mol / L ammonium persulfate and 1.25 mol / L sodium hydroxide, and soak the Cu NPs / CC obtained in step (1) in it for 1 hour. After the alkali-assisted oxidation process, rinse with deionized water and dry at 60°C to obtain CuO NFs-AO / CC;

[0036] (3) Electrodeposition of cerium dioxide nanosheets: Prepare a mixed aqueous solution containing 10 mmol / L cerium nitrate, 0.1 mol / L ammonium acetate and 0.05 mol / L sodium chloride as the electrodeposition solution. Electrodeposition is performed using a constant current method. The CuO NFs-AO / CC obtained in step (2) is used as a working electrode and placed in the electrodeposition solution. The electrode is heated to 70°C, and a constant current of 0.001A is applied thereto and the electrodeposition is continued for 0.5 hours. After the electrodeposition is completed, rinse with deionized water and dry at 60°C to obtain CeO2 NSs / CuO NFs-AO / CC;

[0037] (4) High temperature annealing: The CeO2 NSs / CuO NFs-AO / CC obtained in step (3) is placed in a muffle furnace and annealed at 400°C for 2 hours. After the annealing is completed, it is naturally cooled to room temperature to obtain the nitrite electrochemical sensing electrode based on the copper oxide / cerium dioxide heterostructure (CeO2 NSs / CuO NFs / CC).

[0038] (5) Nitrite electrochemical test: A phosphate buffer solution with a pH of 7 and a concentration of 0.1 mmol / L was prepared as the electrolyte used in the electrochemical test. The CeO2 NSs / CuO NFs / CC prepared in step (4) was used as the working electrode, the saturated calomel electrode was used as the reference electrode, and the platinum sheet was used as the counter electrode. First, the sensing characteristics of 0.5 mM sodium nitrate were tested using cyclic voltammetry at a potential window of 0.2 to 1.0 V and a scan rate of 50 mV / s. Then, a linear test of sodium nitrite with a concentration range of 0.1 to 4000 μM was performed using chronoamperometry at an applied voltage of 0.74 V. Under the condition of stable stirring of the electrolyte, sodium nitrite standard solution was continuously added to obtain the corresponding response current, and a linear equation of the response current and nitrite concentration was obtained by fitting. The results show that in the cyclic voltammetry sensing test, the oxidation peak current of 0.5 mM nitrite on the CeO2NSs / CuO NFs / CC sensor electrode is 1.43 mA cm -2 In the linear test of the chronoamperometry, the concentration range of nitrite from 0.1 to 4000 μM has a good piecewise linear relationship with the current intensity. In the concentration range of 0.1 to 10 μM, the linear equation is y = 0.01161x + 0.04258 (R 2 =0.997), the corresponding sensitivity is 11610μAmM -1 cm -2 In the concentration range of 10 to 1000 μM, the linear equation is y = 3.581x + 0.183 (R 2 =0.997), the corresponding sensitivity is 3581μA mM -1 cm -2 In the concentration range of 1000-4000 μM, the linear equation is y=1.928x+1.900(R 2 =0.999), the corresponding sensitivity is 1928μA mM -1 cm -2 .

[0039] Example 2:

[0040] (1) The process of electroplating copper nanoparticles on carbon cloth is the same as in Example 1;

[0041] (2) Alkali-assisted oxidation to obtain copper oxide nanoflowers is as in Example 1;

[0042] (3) Electrodeposition of cerium dioxide nanosheets: Prepare a mixed solution containing 10 mmol / L cerium nitrate, 0.1 mol / L ammonium acetate and 0.05 mol / L sodium chloride as the electrodeposition solution. Electrodeposition is performed using a constant current method. The CuO NFs-AO / CC obtained in step (2) is used as a working electrode and placed in the electrodeposition solution. The electrode is heated to 70°C, and a constant current of 0.0005A is applied thereto and the electrodeposition is continued for 0.5 hours. After the electrodeposition is completed, rinse with deionized water and dry at 60°C to obtain CeO2 NSs / CuO NFs-AO / CC-0.0005A;

[0043] (4) High temperature annealing process is the same as in Example 1;

[0044] (5) The electrochemical test process of nitrite was the same as in Example 1. The results showed that in the cyclic voltammetry sensing characteristic test, the oxidation peak current of 0.5 mM nitrite on the CeO2 NSs / CuO NFs-AO / CC-0.0005A sensor electrode was 1.24 mA cm -2 .

[0045] Example 3:

[0046] (1) The process of electroplating copper nanoparticles on carbon cloth is the same as in Example 1;

[0047] (2) Alkali-assisted oxidation to obtain copper oxide nanoflowers is as in Example 1;

[0048] (3) Electrodeposition of cerium dioxide nanosheets: Prepare a mixed solution containing 10 mmol / L cerium nitrate, 0.1 mol / L ammonium acetate and 0.05 mol / L sodium chloride as the electrodeposition solution. Electrodeposition was performed using a constant current method. The CuO NFs-AO / CC obtained in step (2) was used as a working electrode and placed in the electrodeposition solution. The electrode was heated to 70°C, and a constant current of 0.001A was applied thereto and the electrodeposition was continued for 1 hour. After the electrodeposition was completed, the solution was rinsed with deionized water and dried at 60°C to obtain CeO2NSs / CuO NFs-AO / CC-60min;

[0049] (4) High temperature annealing process is the same as in Example 1;

[0050] (5) The electrochemical test process of nitrite was the same as in Example 1. The results showed that in the cyclic voltammetry sensing characteristic test, the oxidation peak current of 0.5 mM nitrite on the CeO2 NSs / CuO NFs-AO / CC-60min sensing electrode was 1.29 mA cm -2 .

[0051] Example 4:

[0052] (1) The process of electroplating copper nanoparticles on carbon cloth is the same as in Example 1;

[0053] (2) Alkali-assisted oxidation to obtain copper oxide nanoflowers is as in Example 1;

[0054] (3) Electrodeposition of cerium dioxide nanosheets: Prepare a mixed solution containing 10 mmol / L cerium nitrate, 0.1 mol / L ammonium acetate and 0.05 mol / L sodium chloride as the electrodeposition solution. Electrodeposition is carried out using a constant current method. The CuO NFs-AO / CC obtained in step (2) is used as a working electrode and placed in the electrodeposition solution. It is heated to 60°C, and a constant current of 0.001A is applied thereto and the electrodeposition is continued for 0.5 hours. After the electrodeposition is completed, rinse with deionized water and dry at 60°C to obtain CeO2 NSs / CuO NFs-AO / CC-60°C;

[0055] (4) High temperature annealing process is the same as in Example 1;

[0056] (5) The electrochemical test process of nitrite was the same as in Example 1. The results showed that in the cyclic voltammetry sensing characteristic test, the oxidation peak current of 0.5 mM nitrite on the CeO2 NSs / CuO NFs-AO / CC-60°C sensing electrode was 1.33 mA cm -2 .

[0057] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure, comprising the following steps: (1) Electroplating copper nanoparticles on carbon cloth: A mixed aqueous solution of copper chloride, sodium citrate, and urea was prepared as an electroplating solution; copper was plated using a constant potential method, and a carbon cloth was used as a working electrode and placed in the electroplating solution. A certain voltage was applied to the carbon cloth for a period of time; after the electroplating was completed, the carbon cloth was rinsed and dried to obtain Cu NPs / CC; (2) Alkali-assisted oxidation to obtain copper oxide nanoflowers: prepare a mixed aqueous solution of ammonium persulfate and sodium hydroxide, and immerse the Cu NPs / CC obtained in step (1) in it. After the alkali-assisted oxidation reaction is completed, the mixture is rinsed and dried to obtain CuO NFs-AO / CC. (3) Electrodeposition of cerium dioxide nanosheets: a mixed aqueous solution of cerium nitrate, ammonium acetate, and sodium chloride was prepared as an electrodeposition solution; Electrodeposition is performed using a constant current method, wherein the CuO NFs-AO / CC obtained in step (2) is used as a working electrode and placed in an electrodeposition solution. After heating it to a set temperature, a constant current is applied thereto for a period of time. After the electrodeposition is completed, the solution is rinsed and dried to obtain CeO2 NSs / CuO NFs-AO / CC. (4) High temperature annealing: placing the CeO2 NSs / CuO NFs-AO / CC obtained in step (3) in a muffle furnace and annealing at a certain temperature for a certain time; after the annealing is completed, naturally cooling to room temperature to obtain the nitrite electrochemical sensing electrode based on the copper oxide / cerium dioxide heterostructure, namely CeO2NSs / CuO NFs / CC.

2. The method for preparing a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure according to claim 1, wherein: In step (1), the concentration of copper chloride in the mixed aqueous solution is 5 to 25 mmol / L, the concentration of sodium citrate is 0.05 to 0.20 mol / L, and the concentration of urea is 0.05 to 0.20 mol / L; the voltage of the constant potential is -0.55 to -0.85 V, and the duration is 0.5 to 2 hours.

3. The method for preparing a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure according to claim 1, wherein: The concentration of ammonium persulfate in the mixed aqueous solution in step (2) is 0.04-0.08 mol / L, and the concentration of sodium hydroxide is 1.0-1.5 mol / L; and the soaking time is 15-120 minutes.

4. The method for preparing a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure according to claim 1, wherein: In step (3), the concentration of cerium nitrate in the mixed aqueous solution is 8-12 mmol / L, the concentration of ammonium acetate is 0.05-0.15 mol / L, and the concentration of sodium chloride is 0.02-0.08 mol / L; the temperature is set at 40-90° C., the applied current is 0.0005-0.0015 A, and the duration is 10-60 min.

5. The method for preparing a nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure according to claim 1, wherein: In step (4), the annealing temperature is 350-450° C., and the annealing time is 1.5-3.0 hours.

6. A nitrite sensing electrode based on a copper oxide / cerium dioxide heterostructure, characterized in that: The method is prepared by any one of claims 1 to 5.

7. Use of the nitrite sensing electrode based on the copper oxide / cerium dioxide heterostructure according to claim 6 in electrochemical detection of nitrite.

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