CuNP / Nf-GO modified composite electrode and preparation method and application thereof

Abstract

The invention discloses a CuNP / Nf-GO modified composite electrode and a preparation method and application thereof, and belongs to the technical field of electrochemical sensing detection. The CuNP / Nf-GO modified composite electrode comprises an electrode substrate and a CuNP / Nf-GO functional modification layer on the surface of the electrode substrate, and the CuNP / Nf-GO functional modification layer is formed by loading copper nanoparticles on a net structure formed by assembling Nafion and GO. The electrode shows high electrocatalytic oxidation activity and high stability, can electrocatalytically oxidize refractory organic matters, has better sensing response performance on various organic matters in water, can be used for detecting the content of COD (Chemical Oxygen Demand) in the water, and is particularly suitable for the fields of environmental monitoring, water quality condition diagnosis and the like.

Description

Technical Field

[0001] The invention relates to a sensing electrode, in particular to a CuNP / Nf-GO modified composite electrode, and also to a preparation method thereof and application thereof as a sensor in detecting COD content in water, belonging to the technical field of electrochemical sensing detection. Background Art

[0002] Chemical oxygen demand (COD) is an important indicator of organic pollution in surface water and industrial wastewater. It reflects the total amount of organic matter in the water that can be oxidized by strong oxidants. If these organic matter are not effectively treated, they will accumulate in the water, causing water pollution, and will also have a negative impact on water treatment equipment and processes. Therefore, detecting the COD content in the water is of great significance for controlling water quality and ensuring the stable operation of the sewage treatment system.

[0003] At present, the commonly used COD detection standard is the dichromate method, which requires the use of toxic and dangerous reagents, has certain safety hazards, and its detection cycle is long, which is not suitable for sudden emergency detection. So far, there has been no sensor that uses nano copper, Nafion and GO to detect the content of organic pollutants in water. Summary of the invention

[0004] In view of the shortcomings of the prior art, the first object of the present invention is to provide a CuNP / Nf-GO modified composite electrode, which has high conductivity and high electrochemical activity, can electrocatalytically oxidize organic matter in water, has good sensing response performance to various organic matter in water, and can be used for COD content detection in water.

[0005] The second object of the present invention is to provide a method for preparing a CuNP / Nf-GO modified composite electrode, which has simple process, low cost and can be mass-produced.

[0006] The third object of the present invention is to provide an application of a CuNP / Nf-GO modified composite electrode, which is used as a sensor to detect the COD content in water and exhibits high sensitivity.

[0007] In order to achieve the above technical objectives, the present invention provides a CuNP / Nf-GO modified composite electrode, which includes an electrode substrate and a CuNP / Nf-GO functional modification layer on its surface; the CuNP / Nf-GO functional modification layer is composed of copper nanoparticles loaded on a network structure formed by assembling Nafion and GO.

[0008] The CuNP / Nf-GO modified composite electrode of the present invention uses copper nanoparticles and GO as catalytic active materials. The copper nanoparticles can generate active species CuO(OH) after being activated in an alkaline environment, and have excellent redox properties for difficult-to-degrade organic compounds. After the copper nanoparticles are composited with GO, GO is used to greatly improve the loading stability of the copper nanoparticles, and at the same time improve its electrocatalytic activity and conductivity. At the same time, the GO surface has polar groups, which form a mesh-shaped modified coating on the surface of the electrode substrate through bonding and cross-linking with Nafion, which not only protects the screen-printed electrode, but also greatly improves the conductivity of the electrode substrate surface and the adhesion of the electrocatalytic active substance.

[0009] As a preferred solution, the electrode substrate is a screen-printed electrode. Compared with a traditional three-electrode system, a screen-printed electrode is more compact and has a lower cost.

[0010] As a preferred solution, the mass ratio of GO to Nafion is 1:2 to 4. Nafion is used to load nanomaterials onto electrodes, and too low a proportion of naphthol will result in poor material loading stability, but a higher proportion will reduce the detection capability of the electrode.

[0011] The present invention also provides a method for preparing a CuNP / Nf-GO modified composite electrode, which comprises the following steps:

[0012] 1) After the graphene oxide powder is ultrasonically dispersed in water, it is mixed with the Nafion solution to form a Nf-GO solution;

[0013] 2) dropping the Nf-GO solution onto the substrate electrode and drying it to obtain a Nf-GO modified electrode;

[0014] 3) The Nf-GO modified electrode is placed in an electrolyte containing copper sulfate and CTAB for electrochemical deposition to obtain a CuNP / Nf-GO modified composite electrode.

[0015] The preparation process of the CuNP / Nf-GO modified composite electrode of the present invention is as follows: GO and Nafion are assembled in a solution system to form a cross-linking system, so that a network modification coating can be formed on the surface of the electrode substrate, so that GO is well modified on the surface of the electrode substrate by using Nafion, which greatly improves the conductivity and loadability of the electrode surface, and is conducive to the subsequent in-situ loading of copper nanoparticles on the electrode surface. During the electrochemical deposition process, copper ions free in the electrolyte are captured by polar groups on the network structure formed by the assembly of Nafion and GO, and are in-situ grown and deposited on the electrode surface to be converted into copper nanoparticles, thereby forming a CuNP / Nf-GO modified composite electrode.

[0016] As a preferred solution, the concentration of copper sulfate in the electrolyte is 0.2-0.5 mol / L and the concentration of CTAB is 1-3 mmol / L. CTAB, as a cationic surfactant, can induce the generation of copper nanoparticles.

[0017] As a preferred solution, the conditions of the electrochemical deposition are: voltage of -0.8V to -0.6V, time of 100 to 150s. Under the preferred conditions, the generation of copper nanoparticles can be guaranteed. At the same time, the control conditions can generate an appropriate amount of nano copper particles. If the loading amount is too low, the electrocatalytic oxidation activity of the composite electrode will be reduced, while if the loading amount is too high, it is easy to cause the agglomeration of nano copper particles.

[0018] As a preferred solution, the CuNP / Nf-GO modified composite electrode is placed in an alkaline solution for activation treatment.

[0019] As a preferred solution, the activation treatment conditions are: using 0.3-0.8M NaOH solution as the electrolyte, and cycling the potential between 0.2 and 0.6V for more than 15 times. It is further preferred that the number of cycles is 20-30 times. By performing multiple potential cycles in an alkaline solution, CuO(OH) with higher electrocatalytic oxidation activity can be generated on the surface of the copper nanoparticles. If the number of cycles is too low, the content of the active component of the generated CuO(OH) is low.

[0020] As a preferred solution, the graphene oxide powder is ultrasonically dispersed in water to form a concentration of 0.5 to 2 mg / mL -1 GO dispersion.

[0021] As a preferred solution, the Nafion solution is a 5 wt % commercial Nafion solution diluted to 0.3 wt % with anhydrous ethanol.

[0022] The present invention also provides an application of a CuNP / Nf-GO modified composite electrode, which is used as a sensor for detecting the COD content in water.

[0023] Compared with the prior art, the advantages of the technical solution of the present invention are:

[0024] The CuNP / Nf-GO modified composite electrode provided by the present invention has high conductivity and high electrochemical activity, can electrocatalytically oxidize organic matter in water, has good sensing response performance to various organic matter in water, can be used for COD content detection in water, and is widely used in environmental monitoring and water quality diagnosis. It can avoid the use of typical toxic and dangerous reagents in the standard dichromate oxidation method in the prior art, and significantly shortens the detection time.

[0025] The preparation method of the CuNP / Nf-GO modified composite electrode provided by the present invention has simple process and low cost and can be mass-produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The scanning electron microscope images of the electrodes prepared in Example 1 of the present invention, wherein (a) is a bare SPE electrode, (b) is a SPE electrode coated with NF / GO solution, and (c) and (d) are CuNP / Nf-GO / SPE electrodes.

[0027] Figure 2 This is the energy spectrum analysis diagram of CuNP / Nf-GO / SPE prepared in Example 1 of the present invention.

[0028] Figure 3 This is the electrochemical impedance test diagram of CuNP / Nf-GO / SPE prepared in Example 1 of the present invention.

[0029] Figure 4 This is the cyclic voltammetry scan of CuNP / Nf-GO / SPE prepared in Example 1 of the present invention.

[0030] Figure 5 This is the iT side test diagram of the CuNP / Nf-GO / SPE prepared in Example 1 of the present invention.

[0031] Figure 6 Fitting standard curve for kitchen waste fermentation liquid (dilution). DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. In the following embodiments, unless otherwise specified, the raw materials and instruments used are commercially available.

[0033] Example 1

[0034] A method for preparing a composite electrode of the present invention, wherein the composite nanomaterial-modified screen-printed electrode, wherein NF-GO is distributed in a network structure and Cu nanoparticles are loaded on graphene oxide, comprises the following steps:

[0035] (1) Graphene oxide (GO) powder was dispersed in ultrapure water and sonicated for 15 min to prepare a GO stock solution (1.0 mg mL -1 ), the GO stock solution was mixed with an equal volume of Nafion (commercial 5 wt % Nafion solution was diluted to 0.3 wt % with ethanol) to make 0.5 mg L -1 Nf GO solution;

[0036] (2) Wash the unmodified SPE with ethanol and ultrapure water in turn. Then dry it in air at room temperature. Drop 5 μL of Nf-GO solution on the working electrode and dry it at room temperature to obtain the Nf-GO modified SPE electrode;

[0037] (3) Electrodeposition was continued at -0.6 V for 100 seconds in a mixed solution of 0.5 M CuSO4·5H2O and 2 mM CTAB, followed by rinsing the modified SPE with ultrapure water. Finally, the potential was cycled 20 times between 0.2 and 0.6 V in a 0.5 M NaOH solution to adjust the electrode surface activation;

[0038] like Figure 1 Scanning electron microscopy showed that the prepared NF-GO modified screen-printed electrode presented a smooth mesh structure, and after electrochemical deposition, Cu nanoparticles were loaded on the electrode surface in a crystalline form.

[0039] pass Figure 2 The energy spectrum scan of the CuNP / Nf-GO / SPE composite electrode showed that NF-GO and Cu nanoparticles were successfully loaded onto the surface of the screen-printed electrode.

[0040] Figure 3 This is electrochemical impedance spectroscopy (EIS). EIS is a very effective method to study electron transfer resistance (Rct). Rct is equal to the diameter of the semicircle in the figure. Compared with the bare carbon electrode and the Nf-GO modified electrode, a significant decrease in the resistance of the CuNP / Nf-GO modified electrode was observed, indicating the successful loading of the nanomaterials and reflecting the high conductivity and electrochemical activity of the electrode.

[0041] pass Figure 4 As shown in the CV curve, the CuNP / Nf-GO / SPE electrode exhibits two oxidation peaks in a lower potential window, which respectively reflect the two valence state changes of the electroactive Cu nanoparticles. The electrode generates the electroactive substance CuO(OH) at a high potential.

[0042] Figure 5 The iT test shows that the example electrode of the present invention has good sensing response performance to various organic substances.

[0043] Example 2

[0044] The sensor was used to detect the COD of the fermented biogas in the anaerobic fermentation tank and compared with the potassium dichromate method (refer to the national standard for the determination of chemical oxygen demand of urban sewage, potassium dichromate method). The specific steps are as follows:

[0045] 1. Use the sensor to perform IT test on biogas slurry and draw a standard curve for detecting COD.

[0046] 2. Use the sensor to detect the COD concentration of the diluted food waste fermentation liquid and compare it with the potassium dichromate method.

[0047] from Figure 6 It can be seen that the sensor also has good linear response capability for COD in anaerobic fermentation slurry (linear correlation coefficient is 0.99687).

[0048] It can be seen from the following Table 1 that the sensor has a high accuracy in detecting COD in the anaerobic fermentation slurry of kitchen waste.

[0049] Table 1: Comparison of sensors and standard methods

[0050]

[0051] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A CuNP / Nf-GO modified composite electrode, characterized in that: It comprises an electrode substrate and a CuNP / Nf-GO functional modification layer on its surface; the CuNP / Nf-GO functional modification layer is composed of copper nanoparticles loaded on a mesh structure formed by assembling Nafion and GO.

2. The CuNP / Nf-GO modified composite electrode according to claim 1, characterized in that: The electrode substrate is a screen-printed electrode.

3. The CuNP / Nf-GO modified composite electrode according to claim 1, characterized in that: The mass ratio of GO to Nafion is 1:2-4.

4. The method for preparing a CuNP / Nf-GO modified composite electrode according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) After the graphene oxide powder is ultrasonically dispersed in water, it is mixed with the Nafion solution to form a Nf-GO solution; 2) dropping the Nf-GO solution onto the substrate electrode and drying it to obtain a Nf-GO modified electrode; 3) The Nf-GO modified electrode is placed in an electrolyte containing copper sulfate and CTAB for electrochemical deposition to obtain a CuNP / Nf-GO modified composite electrode.

5. The method for preparing a CuNP / Nf-GO modified composite electrode according to claim 4, characterized in that: The copper sulfate concentration in the electrolyte is 0.2-0.5 mol / L and the CTAB concentration is 1-3 mmol / L.

6. The method for preparing a CuNP / Nf-GO modified composite electrode according to claim 4, characterized in that: The conditions of the electrochemical deposition are: voltage of -0.8V to -0.6V, and time of 100 to 150s.

7. The method for preparing a CuNP / Nf-GO modified composite electrode according to any one of claims 4 to 6, characterized in that: The CuNP / Nf-GO modified composite electrode is placed in an alkaline solution for activation treatment.

8. The method for preparing a CuNP / Nf-GO modified composite electrode according to claim 7, characterized in that: The activation treatment conditions are: using 0.3-0.8M NaOH solution as the electrolyte and cycling the potential between 0.2V and 0.6V for more than 15 times.

9. The use of a CuNP / Nf-GO modified composite electrode according to any one of claims 1 to 3, characterized in that: It is used as a sensor to detect the COD content in water.

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