Preparation method and application of bismuth ferrite / nitrogen oxide carbon modified glassy carbon electrode

Abstract

The embodiment of the application relates to a preparation method and application of a bismuth ferrite / nitrogen oxide carbon oxide modified glassy carbon electrode, and belongs to the technical field of electrochemical analysis. The preparation method of the bismuth ferrite / nitrogen oxide carbon oxide modified glassy carbon electrode comprises the following steps: S1, preparation of bismuth ferrite sol; S2, preparation of nitrogen oxide carbon oxide; S3, preparation of bismuth ferrite / nitrogen oxide carbon oxide; and S4, preparation of the bismuth ferrite / nitrogen oxide carbon oxide modified glassy carbon electrode. The electrode can produce a relatively obvious detection value for a relatively low chloride ion concentration. The electrode belongs to normal pressure technology, and a chemical reaction does not occur in the process of detecting chloride ions, so that the electrode has the advantages of low energy consumption, good tolerance, no secondary pollution, good conductivity, stable structure, low preparation cost, simple preparation method and the like.

Description

Technical Field

[0001] This application relates to the field of electrochemical analysis technology, and in particular to a method for preparing and applying a bismuth ferrite / carbon nitride modified glassy carbon electrode. Background Technology

[0002] With continuous social development and improper human disposal, excessively high chloride ion concentrations in wastewater have become one of the most serious and significant resource and environmental problems in the world today. Large amounts of chloride-containing wastewater discharged into the environment have severely impacted the biosphere. The main sources of chloride-containing wastewater are industrial enterprises such as the textile, food, metallurgical, and petrochemical industries. Chloride ions are the most common anion in wastewater. Excessively high chloride ion concentrations can cause bitter taste in drinking water, soil salinization, pipe corrosion, and hinder plant growth, and harm human health. If the large amounts of chloride ions in this wastewater are not effectively removed and discharged into water bodies, they will cause serious and lasting harm to human health, soil, and the ecological environment. Chloride ions play various physiological roles. Many cells have chloride ion channels, which are mainly responsible for controlling the membrane potential and cell volume of resting cells. Therefore, high chloride ion levels are harmful to the human body. This is mainly manifested in strong irritation of the upper respiratory tract mucosa, leading to acute failure of lung and heart function. Inhaling high concentrations of chlorine gas can cause severe symptoms: difficulty breathing, cyanosis, and heart failure. Patients often die rapidly from respiratory paralysis, usually within minutes to an hour, a phenomenon known as "lightning-like death." Therefore, detecting low concentrations of chloride ions is an urgent issue. Common methods for detecting chloride ions include electron spin resonance, spectrophotometry, chemiluminescence, chromatography, fluorescence, and electrochemical methods. Relatively speaking, electrochemical instruments are cheaper, simpler to operate, and easier to monitor in real time, thus offering advantages in quantitative chloride ion analysis. However, existing detection technologies have insufficient minimum detection limits, are expensive, and complex to operate. Summary of the Invention

[0003] In view of this, the present application provides a method for preparing and applying a bismuth ferrite / carbon nitride modified glassy carbon electrode, which can detect chloride ion concentrations with lower detection limits and can effectively overcome the defects of the prior art.

[0004] The first aspect of this application provides a method for preparing a bismuth ferrite / carbon nitride modified glassy carbon electrode, comprising the following steps:

[0005] S1. Preparation of bismuth ferrite sol: Iron source and bismuth source are dissolved in organic solvent, and chelating agent is added. After heating and stirring, the mixture is cooled to room temperature, the pH value is adjusted to 3.5-4, and after aging, a stable bismuth ferrite sol is obtained.

[0006] S2. Preparation of carbon nitride oxide: Under ice bath conditions, graphitic carbon nitride is dissolved in concentrated sulfuric acid, and potassium permanganate, ultrapure water and hydrogen peroxide solution are added in sequence. After centrifugation, washing and drying, carbon nitride oxide is obtained.

[0007] S3. Preparation of bismuth ferrite / carbon nitride: Carbon nitride was dissolved in ultrapure water, sonicated and then magnetically stirred. Bismuth ferrite sol was added at the same time, and the mixture was magnetically stirred and then sonicated to obtain a bismuth ferrite / carbon nitride mixture.

[0008] S4. Preparation of bismuth ferrite / carbon nitride modified glassy carbon electrode: The bismuth ferrite / carbon nitride mixture is drop-coated onto the glassy carbon electrode and dried in air to obtain the bismuth ferrite / carbon nitride modified glassy carbon electrode.

[0009] Bismuth ferroate (BFO) is currently the only ferromagnetic material that exhibits both ferroelectric and ferromagnetic properties at room temperature, possessing excellent electrical, magnetic, and magnetoelectric properties. As a ferroelectric semiconductor material, BFO exhibits excellent ferroelectric polarization performance and also boasts the advantages of being lead-free and environmentally friendly. Carbon nitride oxide provides numerous oxygen-containing functional groups and increases the specific surface area of ​​the material, offering more active sites for chloride ion determination.

[0010] In some embodiments that may include the above embodiments, the process of step S1 is as follows:

[0011] Analytical grade ferric nitrate (Fe(NO3)3·9H2O) and 10% excess analytical grade bismuth nitrate (Bi(NO3)3·5H2O) were dissolved in ethylene glycol, and acetylacetone was added. The mixture was heated and stirred for 3 hours, then cooled to room temperature. Ethylenediamine was added dropwise to adjust the pH of the solution to 3.5-4, resulting in a precursor sol with a stoichiometric ratio of 1:1 and a concentration of 0.3 mol / L. The precursor sol was aged for 5 days to obtain a stable bismuth ferrite sol.

[0012] In some embodiments that may include the above embodiments, step S2 includes the following steps:

[0013] S201. Take a certain amount of melamine in a crucible and heat it to 550℃ at a rate of 5℃ / min. Calcine it for 3 hours to obtain yellow graphitic carbon nitride.

[0014] S202. Under ice bath conditions, the ground graphitic carbon nitride was slowly added to concentrated sulfuric acid and stirred for 2 hours. The carbon nitride gradually turned white. Ground potassium permanganate was weighed and slowly added, and stirred for another 1 hour to obtain a mixture. The mixture was slowly heated to 30-40℃, and then ultrapure water was slowly added to obtain a suspension. 5% hydrogen peroxide solution was added until the suspension turned milky white. After centrifuging the suspension, the precipitate was washed several times with ultrapure water until the pH was neutral. The precipitate was placed in a room temperature environment and allowed to dry naturally for 24 hours to obtain carbon nitride oxide.

[0015] In some embodiments that may include the above embodiments, the process of step S3 is as follows:

[0016] A certain amount of carbon nitride was ultrasonicated in ultrapure water for 1 hour, and then magnetically stirred for 1 hour. During the stirring process, a certain amount of bismuth ferrite was added in small amounts several times. After the addition was completed, magnetic stirring was performed again for 1 hour. Finally, the solution was ultrasonicated for 3 hours to obtain a bismuth ferrite / carbon nitride mixture with a molar ratio of 1:1.

[0017] In some embodiments that may include the above embodiments, step S4 includes the following steps:

[0018] S401. Grind the glassy carbon electrode sequentially with Al2O3 powder with particle sizes of 1.0μm and 0.5μm. After each grinding, wash it with distilled water and let it air dry in a cool place for later use.

[0019] S402. A bismuth ferrite / carbon nitride mixture with a molar ratio of 1:1 is drop-coated onto a cleaned glassy carbon electrode and dried in air to obtain a bismuth ferrite / carbon nitride modified glassy carbon electrode.

[0020] The second aspect of this application also provides the application of the electrode prepared by the preparation method described above in the electrochemical detection of chloride ions.

[0021] In some embodiments that may include the above embodiments, the step of electrochemical detection of chloride ions includes:

[0022] (1) Prepare chloride ion aqueous solutions of different concentrations using PBS buffer solution;

[0023] (2) A three-electrode system was formed by using a bismuth ferrite / carbon nitride modified glassy carbon electrode as the working electrode, a platinum electrode as the counter electrode, and Ag / AgCl as the reference electrode. The three-electrode system was placed in an aqueous chloride ion solution.

[0024] (3) Differential pulse voltammetry was used to electrochemically detect chloride ions and obtain the peak currents corresponding to different concentrations of chloride ions.

[0025] (4) Plot a standard curve with peak current as the ordinate and concentration as the abscissa;

[0026] (5) Place the three-electrode system in an aqueous chloride solution of unknown depth to obtain the differential pulse voltammetry curve and peak current of the aqueous chloride solution of unknown concentration, and obtain the chloride concentration according to the standard curve.

[0027] In some embodiments that may include the above examples, the concentrations of the chloride ion aqueous solutions of different concentrations are respectively: 1×10 -5 mol / L, 1×10 -6 mol / L, 1×10-7 mol / L, 1×10 -8 mol / L, 1×10 -9 mol / L.

[0028] In some embodiments that may include the above examples, the electrochemical parameters of the differential pulse voltammetry are: a scan potential range of -0.8 to 0 V and a scan rate of -0.2 mV / s.

[0029] It should be noted that this application uses a negative scan. In cyclic voltammetry testing, the voltage window is generally set from negative to positive. Taking the standard electrochemical peaks as an example, the positive scan peaks are the peak potentials and peak currents when the reduced substance in the system undergoes electrochemical oxidation on the working electrode surface. The negative scan peaks are the peak potentials and peak currents when the oxidized substance in the system undergoes electrochemical reduction on the working electrode surface.

[0030] In some embodiments that may include the above examples, the detection limit for chloride ions by differential pulse voltammetry is 1 × 10⁻⁶. -14 mol / L, linear range is 1×10 -14 -6×10 -12 mol / L.

[0031] Compared with the prior art, the embodiments of this application have the following beneficial effects:

[0032] 1. This application provides a method for detecting chloride ion concentrations with lower detection limits. The synthesis method is simple, low-cost, and can be used for large-scale industrial production.

[0033] 2. This application enables the electrode to produce a more obvious detection value for lower chloride ion concentrations. Because it is an atmospheric pressure technology, no chemical reaction occurs during the chloride ion detection process. It has the advantages of low energy consumption, good tolerance, no secondary pollution, good conductivity, stable structure, low preparation cost, and simple preparation method, thus becoming an effective chloride ion detection technology. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 These are IV diagrams of the electrodes in Embodiment 1 and Comparative Examples 1-3 of this application;

[0036] Figure 2 This is a comparison diagram of the bismuth ferrite / carbon nitride modified glassy carbon electrode in Example 1 of this application at different enrichment voltages;

[0037] Figure 3 This is a comparison diagram of different enrichment times of the bismuth ferrite / carbon nitride modified glassy carbon electrode in Example 1 of this application;

[0038] Figure 4 This is a morphology diagram of the bismuth ferrite / carbon nitride composite in Example 1 of this application;

[0039] Figure 5 The linear curve of concentration versus voltage response of the bismuth ferrite / carbon nitride composite material in Example 1 of this application is shown.

[0040] Figure 6 This is the peak current-concentration standard curve of the bismuth ferrite / carbon nitride composite material in Example 1 of this application. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] In the following examples and comparative examples, unless otherwise specified, all raw materials can be obtained by commercial purchase or conventional methods; all reagents used are of analytical grade, and all experimental water is double-distilled water.

[0043] In the embodiments of this application, the analytical instruments are CHI760E electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.), BT125D electronic analytical balance (Mettler-Toledo Instruments Ltd.), and PHS-2F pH meter (Leici-Shanghai Instrument & Electronics Scientific Instruments Co., Ltd.).

[0044] Example 1

[0045] A method for preparing a bismuth ferrite / carbon nitride modified glassy carbon electrode includes the following steps:

[0046] S1. Analytical grade ferric nitrate (Fe(NO3)3·9H2O) and 10% excess analytical grade bismuth nitrate (Bi(NO3)3·5H2O) were dissolved in ethylene glycol, and acetylacetone was added. The mixture was heated and stirred for 3 hours, then cooled to room temperature. Ethylenediamine was added dropwise to adjust the pH of the solution to 3.5-4, resulting in a precursor sol with a stoichiometric ratio of 1:1 and a concentration of 0.3 mol / L. The precursor sol was aged for 5 days to obtain a stable bismuth ferrite sol.

[0047] S2. A certain amount of melamine was placed in a crucible and heated to 550℃ at a rate of 5℃ / min, and calcined for 3 hours to obtain yellow graphitic carbon nitride. Under ice bath conditions, 10g of ground graphitic carbon nitride was slowly added to 50mL of concentrated sulfuric acid and stirred for 2 hours. The carbon nitride gradually turned white. 1.2g of ground potassium permanganate was weighed and slowly added, and stirred for another 1 hour to obtain a mixture. The mixture was slowly heated to 30-40℃, and then 200mL of ultrapure water was slowly added to obtain a suspension. 5% hydrogen peroxide solution was added until the suspension turned milky white. After centrifuging the suspension, the precipitate was washed several times with ultrapure water until the pH was neutral. The precipitate was placed at room temperature and dried naturally for 24 hours to obtain carbon nitride oxide.

[0048] S3. Take a certain amount of carbon nitride and sonicate it in 20 ml of ultrapure water for 1 hour, then stir it magnetically for 1 hour. During the stirring process, add a certain amount of bismuth ferrite in small amounts several times. After the addition is complete, stir it magnetically for 1 hour. Finally, continue to sonicate the solution for 3 hours to obtain a bismuth ferrite / carbon nitride mixture with a molar ratio of 1:1.

[0049] S4. The glassy carbon electrode was successively polished with Al2O3 powder with particle sizes of 1.0 μm and 0.5 μm. After each polishing, it was washed with distilled water and air-dried in a cool place for later use. 12 μL of a bismuth ferrite / carbon nitride mixture with a molar ratio of 1:1 was drop-coated onto the cleaned glassy carbon electrode and dried in air to obtain a bismuth ferrite / carbon nitride modified glassy carbon electrode.

[0050] Example 2

[0051] PBS buffer solution was used to prepare solutions with concentrations of 1×10⁻⁶. -5 mol / L, 1×10 -6 mol / L, 1×10 -7 mol / L, 1×10 -8 mol / L, 1×10 -9 A mol / L aqueous solution of chloride ions;

[0052] The bismuth ferrite / carbon nitride modified glassy carbon electrode prepared in Example 1 was used as the working electrode, the platinum electrode as the counter electrode, and Ag / AgCl as the reference electrode to form a three-electrode system. The three-electrode system was placed in an aqueous chloride ion solution.

[0053] Differential pulse voltammetry was used to electrochemically detect chloride ions. The scanning potential range was -0.8 to 0 V, and the scanning speed was -0.2 mV / s. Peak currents corresponding to different concentrations of chloride ions were obtained.

[0054] Plot a standard curve with peak current as the ordinate and concentration as the abscissa, as shown below. Figure 6 As shown; the detection limit is 1×10⁻⁶. -14 mol / L, linear range is 1×10-14 -6×10 -12 mol / L.

[0055] The three-electrode system was placed in an aqueous chloride ion solution of unknown depth to obtain the differential pulse voltammetry curve and peak current of the aqueous chloride ion solution of unknown concentration. The concentration of chloride ions was then determined based on the standard curve.

[0056] Comparative Example 1

[0057] The bismuth ferrite-modified glassy carbon electrode provided in this comparative example is similar to Example 1, except that it does not contain carbon nitride oxide.

[0058] Comparative Example 2

[0059] The carbon nitride modified glassy carbon electrode provided in this comparative example is similar to Example 1, except that it does not contain bismuth ferrite.

[0060] Comparative Example 3

[0061] The glassy carbon provided in this comparative example is the same as that in Example 1, except that it does not contain carbon nitride oxide and bismuth ferrite.

[0062] Application examples

[0063] Depend on Figure 1 It can be seen that the glassy carbon electrode modified with bismuth ferrite / carbon nitride oxide has the best detection effect.

[0064] Depend on Figure 2 It can be seen that the pulse peak is largest at an enrichment voltage of -0.9V, but the difference between -0.9V and -0.8V is not significant. Therefore, we choose -0.8V as the optimal enrichment voltage. Thus, it can be concluded that the detection effect is best when the enrichment voltage is -0.8V.

[0065] Depend on Figure 3 It can be seen that the pulse peak is largest at an enrichment time of 400s, but the difference between enrichment times of 400s and 350s is not significant. Therefore, we choose 350s as the optimal enrichment time. Thus, it can be concluded that the detection effect is best when the enrichment time is 350s.

[0066] Depend on Figure 4 It is known that the composite material of bismuth ferrite (BFO) and carbon nitride (CNO) forms a scaly structure, and when this composite material is used as a composite material for electrochemical detection, it can exhibit excellent electrochemical performance.

[0067] Depend on Figure 5 It can be seen that up to 2×10 -14 At a concentration of ppm, the detection voltage still maintains a good linear relationship.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a bismuth ferrite / carbon nitride modified glassy carbon electrode, characterized in that, Includes the following steps: S1. Preparation of bismuth ferrite sol: Iron source and bismuth source are dissolved in organic solvent, and chelating agent is added. After heating and stirring, the mixture is cooled to room temperature, the pH value is adjusted to 3.5-4, and after aging, a stable bismuth ferrite sol is obtained. S2. Preparation of carbon nitride oxide: Under ice bath conditions, graphitic carbon nitride is dissolved in concentrated sulfuric acid, and potassium permanganate, ultrapure water and hydrogen peroxide solution are added in sequence. After centrifugation, washing and drying, carbon nitride oxide is obtained. S3. Preparation of bismuth ferrite / carbon nitride: Carbon nitride was dissolved in ultrapure water, sonicated and then magnetically stirred. Bismuth ferrite sol was added at the same time, and the mixture was magnetically stirred and then sonicated to obtain a bismuth ferrite / carbon nitride mixture. S4. Preparation of bismuth ferrite / carbon nitride modified glassy carbon electrode: The bismuth ferrite / carbon nitride mixture is drop-coated onto the glassy carbon electrode and dried in air to obtain the bismuth ferrite / carbon nitride modified glassy carbon electrode.

2. The preparation method according to claim 1, characterized in that, The process of step S1 is as follows: Analytical grade ferric nitrate Fe(NO3)3·9H2O and 10% excess analytical grade bismuth nitrate Bi(NO3)3·5H2O were dissolved in ethylene glycol, and acetylacetone was added. The mixture was heated and stirred for 3 hours, then cooled to room temperature. Ethylenediamine was added dropwise to adjust the pH of the solution to 3.5-4, resulting in a precursor sol with a stoichiometric ratio of 1:1 and a concentration of 0.3 mol / L. The precursor sol was aged for 5 days to obtain a stable bismuth ferrite sol.

3. The preparation method according to claim 1, characterized in that, Step S2 includes the following steps: S201. Take a certain amount of melamine in a crucible and heat it to 550℃ at a rate of 5℃ / min. Calcine it for 3 hours to obtain yellow graphitic carbon nitride. S202. Under ice bath conditions, the ground graphitic carbon nitride was slowly added to concentrated sulfuric acid and stirred for 2 hours. The carbon nitride gradually turned white. Ground potassium permanganate was weighed and slowly added, and stirred for another 1 hour to obtain a mixture. The mixture was slowly heated to 30-40℃, and then ultrapure water was slowly added to obtain a suspension. 5% hydrogen peroxide solution was added until the suspension turned milky white. After centrifuging the suspension, the precipitate was washed several times with ultrapure water until the pH was neutral. The precipitate was placed in a room temperature environment and allowed to dry naturally for 24 hours to obtain carbon nitride oxide.

4. The preparation method according to claim 1, characterized in that, The process of step S3 is as follows: Take a certain amount of carbon nitride and sonicate it in ultrapure water for 1 hour, then stir it magnetically for 1 hour; add a certain amount of bismuth ferrite in small amounts several times during the stirring process, and stir it magnetically for 1 hour after the addition is complete, and finally continue to sonicate the solution for 3 hours. A bismuth ferrite / carbon nitride mixture with a molar ratio of 1:1 was obtained.

5. The preparation method according to claim 4, characterized in that, Step S4 includes the following steps: S401. Grind the glassy carbon electrode sequentially with Al2O3 powder with particle sizes of 1.0μm and 0.5μm. After each grinding, wash it with distilled water and let it air dry in a cool place for later use. S402. A bismuth ferrite / carbon nitride mixture with a molar ratio of 1:1 is drop-coated onto a cleaned glassy carbon electrode and dried in air to obtain a bismuth ferrite / carbon nitride modified glassy carbon electrode.

6. The application of the electrode prepared by the preparation method according to any one of claims 1-5 in the electrochemical detection of chloride ions.

7. The application according to claim 6, characterized in that, The steps for electrochemical detection of chloride ions include: (1) Prepare chloride ion aqueous solutions of different concentrations using PBS buffer solution; (2) A three-electrode system was formed by using a bismuth ferrite / carbon nitride modified glassy carbon electrode as the working electrode, a platinum electrode as the counter electrode, and Ag / AgCl as the reference electrode. The three-electrode system was placed in an aqueous chloride ion solution. (3) Differential pulse voltammetry was used to electrochemically detect chloride ions and obtain the peak currents corresponding to different concentrations of chloride ions. (4) Plot a standard curve with peak current as the ordinate and concentration as the abscissa; (5) Place the three-electrode system in an aqueous chloride solution of unknown depth to obtain the differential pulse voltammetry curve and peak current of the aqueous chloride solution of unknown concentration, and obtain the chloride concentration according to the standard curve.

8. The application according to claim 7, characterized in that, The concentrations of chloride ion aqueous solutions of different concentrations are: 1×10 -5 mol / L, 1×10 -6 mol / L, 1×10 -7 mol / L, 1×10 -8 mol / L, 1×10 -9 mol / L.

9. The application according to claim 7, characterized in that, The electrochemical parameters for differential pulse voltammetry are: scanning potential range of -0.8 to 0 V, and scanning speed of -0.2 mV / s.

10. The application according to claim 7, characterized in that, The detection limit for chloride ions by differential pulse voltammetry is 1 × 10⁻⁶. -14 mol / L, linear range is 1×10 -14 -6×10 -12 mol / L.

Images