A flexible reference electrode and a preparation method thereof

Abstract

The application belongs to the technical field of electrode preparation, and discloses a flexible reference electrode and a preparation method thereof. Carbon cloth and graphene oxide are used as the substrate of the reference electrode, a silver layer is deposited on the flexible graphene oxide / carbon cloth substrate by using an electrochemical method, a petal-shaped Ag / AgCl reference electrode is prepared by using an electrochemical chlorination method, and a layer of conductive hydrogel is coated on the graphene oxide / carbon cloth Ag / Cl to form an encapsulating film. The conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode prepared by the application has excellent conductivity, stability and ion permeability, and the reference electrode has a long service life, good electrode performance, and can be comparable to commercial electrodes, and can be applied to the efficient detection of ethanol.

Description

Technical Field

[0001] The present invention belongs to the field of electrode preparation technology, and particularly relates to a flexible reference electrode and a preparation method thereof, and more particularly to a preparation method of a conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode. Background Art

[0002] A reference electrode is an electrode used as a reference and comparison when measuring the potential of various electrodes. It should have advantages such as stable electrode potential and good reproducibility, and is an indispensable and important component in electrochemical analysis. Saturated calomel electrode and Ag / AgCl electrode are commonly used reference electrodes in laboratories. They are made of rigid materials and consist of wires, electrode caps, glass tubes, etc. However, they have problems such as insufficient flexibility, fragility, and limited application. Therefore, it is very important to improve the performance of reference electrodes by using different preparation methods or using new materials to prepare reference electrodes. For example, the powder-pressed Ag / AgCl reference electrode needs to go through steps such as pressing and sintering during the preparation process, which will have a certain impact on the porosity, thereby affecting the penetration and diffusion of ions and the performance of the electrode, making it still have a large gap with traditional commercially available reference electrodes. Inkjet printing is a new, contactless, and rapid processing technology. It is also a common method for preparing planar reference electrodes. Nano-sized silver solution is printed on a substrate by inkjet printing. The substrate material is usually hard glass, which has the problem of insufficient softness. The prepared electrodes have low repeatability and poor conductivity, and cannot be compared with traditional commercial electrodes. Summary of the Invention

[0003] To overcome the problems of conventional reference electrodes, such as insufficient flexibility, fragility, and limited applications, the present invention provides a flexible reference electrode and its preparation method, specifically a method for preparing a conductive hydrogel / graphene oxide / carbon cloth Ag / AgCl reference electrode. The preparation method of the present invention can produce a conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode that is flexible, stable, and has a long lifespan, while also possessing an encapsulating membrane with excellent ion permeability.

[0004] The inventive concept of the present invention is to use carbon cloth with a uniform carbon fiber pore size distribution and highly conductive, chemically stable graphene oxide as the substrate for a reference electrode, which has good flexibility and high conductivity. A petal-shaped Ag / AgCl reference electrode is prepared by electrochemically depositing a silver layer on the flexible graphene oxide / carbon cloth substrate and electrochemically chlorinating the silver layer, so that the Ag / AgCl is evenly and evenly distributed on the graphene oxide / carbon cloth substrate. Finally, a layer of conductive hydrogel prepared with a saturated KCl solution is coated on the graphene oxide / carbon cloth Ag / AgCl as an encapsulating film to protect the Ag / AgCl layer from falling off. The electrode prepared by the present invention uses a dual-carbon material as the substrate, greatly improving the conductivity of the electrode substrate, thereby enhancing the stability and service life of the reference electrode. The invention is the first to propose using a conductive hydrogel prepared with a saturated KCl solution as the encapsulating film, which has good ion permeability and can prevent the Ag / AgCl layer from falling off. The present invention is original in terms of the preparation of the electrode material and the encapsulating film.

[0005] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0006] A flexible reference electrode is disclosed. Carbon cloth and graphene oxide are used as the reference electrode substrates. A petal-shaped Ag / AgCl reference electrode is prepared by first electrochemically depositing a silver layer on the flexible graphene oxide / carbon cloth substrate and then using an electrochemical chlorination method. Ag / AgCl is evenly and flatly distributed on the graphene oxide / carbon cloth substrate. Finally, a conductive hydrogel prepared using a saturated KCl solution is coated on the graphene oxide / carbon cloth Ag / AgCl as an encapsulation film.

[0007] The specific preparation method of the flexible reference electrode is as follows:

[0008] S1. Preparation of graphene oxide / carbon cloth flexible substrate:

[0009] (1) Prepare a piece of carbon cloth as a substrate, and ultrasonically clean it in ultrapure water, acetone, and ethanol for 30 minutes to remove surface impurities. Then, soak the carbon cloth in a 0.1M to 0.5M hydrochloric acid solution for 5 hours to 8 hours for acidification modification, and dry it at room temperature for later use.

[0010] (2) Soak the carbon cloth after acidification treatment in step (1) in 1 mg / mL to 5 mg / mL polydimethyl ammonium chloride solution (PDDA) for 30 minutes.

[0011] (3) Finally, a layer of graphene oxide solution is evenly coated on the carbon cloth substrate after the modification treatment in step (2), wherein the concentration of the graphene oxide solution is 1 mg / mL to 5 mg / mL, and the solution is dried at room temperature to obtain a graphene oxide / carbon cloth substrate.

[0012] S2. Preparation of Ag / AgCl layer:

[0013] (1) A three-electrode system was used, with the flexible substrate prepared in step S1 as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum wire as the counter electrode. The substrate was placed in a mixed solution of 0.02M to 0.07M AgNO3 and 0.2M to 0.7M NaNO3, and silver nanoparticles were electrochemically deposited using a chronoamperometry method. The deposition time was 2500s to 3500s, and the deposition potential was -0.4V to -0.8V to prepare an Ag-graphene oxide / carbon cloth electrode.

[0014] (2) A three-electrode system was used, with the Ag-graphene oxide / carbon cloth electrode as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. The three-electrode system was placed in a 0.2M~0.7M HCl solution, and the Ag- / graphene oxide / carbon cloth electrode was chlorinated by electrochemical chlorination. The chlorination time was 2600s~3600s, and the chlorination potential was 100mV~500mV to prepare a graphene oxide / carbon cloth-Ag / AgCl reference electrode.

[0015] S3. Preparation of conductive hydrogel encapsulation film;

[0016] The hydrogel was prepared using a one-step freeze-thaw method. Polyvinyl alcohol (PVA) powder was dissolved at a temperature between 90 and 100°C using glycerol / water as a cosolvent and tannic acid (TA) as a crosslinker. After the PVA was completely dissolved, the dried graphene oxide / carbon cloth / Ag / AgCl electrode was placed in a Petri dish. The PVA solution was evenly poured onto the electrode surface and then incubated at -20°C for 2 hours to obtain a graphene oxide / carbon cloth-Ag / AgCl electrode encapsulated with the PVA hydrogel. This electrode was then immersed in a saturated KCl solution for 16 hours and then dried in a vacuum oven at 20 to 50°C for 2 to 4 hours to obtain a conductive hydrogel / graphene oxide / carbon cloth Ag / AgCl reference electrode.

[0017] Furthermore, the size of the carbon cloth in step S1 is 1.5 cm×4 cm.

[0018] The present invention also seeks to protect the use of the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode prepared by the above preparation method in detecting ethanol solutions. Furthermore, the application uses cyclic voltammetry to detect ethanol.

[0019] The beneficial effects of the present invention compared with the prior art are:

[0020] The present invention is the first to use carbon cloth / graphene oxide as the substrate for the reference electrode. Compared to traditional rigid reference electrodes that cannot be bent, the advantage of the present invention's substrate is that using carbon cloth as the substrate for the reference electrode and coating it with a layer of graphene oxide as a conductive layer can further improve the conductivity, bendability, and stability of the reference electrode. Carbon cloth has a smooth, soft, and thin surface, and graphene oxide has a stable structure and excellent conductivity. However, using them alone still has drawbacks. Given the smooth surface of carbon cloth, graphene oxide directly coated on the carbon cloth surface is unstable and easily falls off. Therefore, the carbon cloth is modified to allow the graphene oxide to adhere more closely to the carbon cloth surface through electrostatic adsorption. The present invention designs carbon cloth and graphene oxide as the substrate for the reference electrode, which can greatly improve the substrate's conductivity and stability.

[0021] To overcome the problems of traditional electrodes being easily broken and the reference solution leaking, the present invention uses a conductive hydrogel as an encapsulating membrane, coating the reference electrode with a layer of conductive hydrogel. The conductive hydrogel's conductive material is saturated with KCl, which ensures both conductivity and charge balance. The conductive hydrogel protects the graphene oxide / carbon cloth Ag / AgCl from falling off and damage, increasing the electrode's stability and service life. Its excellent conductivity and ion permeability ensure rapid ion transport to the electrode surface.

[0022] The Ag / AgCl layer of the present invention is prepared by an electrochemical deposition method and an electrochemical chlorination method. The two methods work together to control the deposition time and deposition potential to control the size and shape of deposited nanoparticles. A unique petal-shaped electrode can be obtained within a deposition potential range of -0.4V to 0.8V, a deposition time range of 2500s to 3500s, and a chlorination potential range of 100mV to 500mV, a deposition time range of 2600s to 3600s. Thus, Ag / AgCl nanoparticles with a unique flower-like shape are prepared and uniformly deposited on a graphene oxide / carbon cloth substrate. Furthermore, the dual-carbon material substrate ensures more stable electron transmission.

[0023] In summary, the electrode provided by the present invention overcomes the defects of existing reference electrodes and has excellent conductivity, stability and ion permeability. In addition, the electrode of the present invention has a long service life and good electrode performance, which is comparable to commercial electrodes and can be used for the efficient detection of ethanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode.

[0025] Figure 2 This is a scanning electron microscope image of the conductive hydrogel / graphene oxide / carbon cloth-Ag electrode.

[0026] Figure 3This is a scanning electron microscope image of the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode.

[0027] Figure 4 This is the XRD pattern of the conductive hydrogel / graphene oxide / carbon cloth Ag electrode.

[0028] Figure 5 This is the XRD pattern of the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode.

[0029] Figure 6 This is the chronopotentiometry curve of the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode.

[0030] Figure 7 This is a bar chart of the storage stability of the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode.

[0031] Figure 8 Comparison of the cyclic voltammetry curves of ethanol catalyzed by the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode and the commercial hard glass reference electrode. DETAILED DESCRIPTION

[0032] The present invention is described in detail below by specific examples, but the scope of protection of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0033] Example 1

[0034] The specific preparation process of the conductive hydrogel / graphene oxide / carbon cloth Ag / AgCl reference electrode of the present invention includes the preparation of the graphene oxide / carbon cloth substrate, the preparation of the Ag / AgCl layer, and the preparation of the conductive hydrogel encapsulating film. The specific steps are as follows:

[0035] S1. Preparation of graphene oxide / carbon cloth substrate;

[0036] Prepare a piece of carbon cloth as the reference electrode substrate. Cut into 1.5 cm x 4 cm pieces, ultrasonically clean the cloth in ultrapure water, acetone, and ethanol for 30 minutes to remove surface impurities. Then, soak the cleaned carbon cloth in a 0.1 M hydrochloric acid solution for 5 hours to acidify it. Remove the cloth, blow dry it with nitrogen, and air dry it at room temperature before use. Soak the acidified carbon cloth in a 1 mg / mL solution of polydimethylammonium chloride (PDDA) for 30 minutes, remove it, blow dry it with nitrogen, and air dry it at room temperature before use. Finally, evenly coat the modified carbon cloth substrate with a 1 mg / mL graphene oxide solution and dry it at room temperature to obtain a graphene oxide / carbon cloth substrate.

[0037] S2. Preparation of Ag / AgCl layer;

[0038] Silver was electrochemically deposited using a three-electrode system using a chronoamperometry method. The graphene oxide / carbon cloth that had been left to stand for one day was used as the working electrode, the saturated calomel electrode was used as the reference electrode, and the platinum wire was used as the counter electrode. The electrolyte used for electrochemical deposition was 0.02M AgNO3 and 0.2M NaNO3, the electrochemical deposition time was 2800s, and the deposition potential was -0.4V. After deposition, it was gently rinsed with ultrapure water and dried at room temperature to obtain a graphene oxide / carbon cloth-Ag electrode. The electrode morphology is shown in FIG. Figure 2 shown.

[0039] The Ag-graphene oxide / carbon cloth electrode was chlorinated by electrochemical chlorination using a three-electrode system. The graphene oxide / carbon cloth-Ag electrode was used as the working electrode, Ag / AgCl was used as the reference electrode, and platinum wire was used as the counter electrode. The electrolyte used for electrochemical chlorination was 0.2M HCl, the electrochemical chlorination time was 3100s, and the chlorination potential was 200mV. The chlorinated electrode was gently rinsed with ultrapure water, dried at room temperature, and allowed to stand for one day to obtain a graphene oxide / carbon cloth-Ag / AgCl reference electrode. The electrode morphology is as follows: Figure 3 shown.

[0040] S3. Preparation of conductive hydrogel encapsulation film;

[0041] 18.0 g of a 1:1 glycerol / water solution was prepared. 2 g of polyvinyl alcohol (PVA) and 3 g of (TA) tannic acid were dissolved in the 18.0 g glycerol / water co-solvent system. The mixture was stirred thoroughly at 90°C until the PVA powder was completely dissolved. The dried graphene oxide / carbon cloth-Ag / AgCl electrode was placed in a Petri dish. The completely dissolved mixed solution was evenly cast onto the electrode surface. The electrode was then incubated at -20°C for 2 hours to obtain a graphene oxide / carbon cloth-Ag / AgCl electrode with a polyvinyl alcohol hydrogel as the encapsulating membrane. The encapsulating membrane was approximately 0.3 mm thick. The electrode was then immersed in a saturated KCl solution for 16 hours and finally dried in a vacuum oven at 30°C for 3 hours to obtain a conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode with excellent ion permeability.

[0042] Example 2

[0043] The open circuit potential stability of the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode was tested within 600s by the open circuit potential method.

[0044] The three-electrode system consists of a glassy carbon electrode as the working electrode, a platinum wire as the counter electrode, and the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl electrode prepared in Example 1 as the reference electrode.

[0045] The open circuit potential method was used to place the three-electrode system in a 2M KCl solution, with the glassy carbon electrode as the working electrode, the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode as the reference electrode, and the platinum wire as the counter electrode. The performance was compared with that of a commercial reference electrode (commercial hard glass electrode). Figure 6 It can be seen that in the open circuit potential measurement within 600s, the open circuit potential of the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode is stable, and the voltage remains basically stable, which is comparable to that of commercial reference electrodes, and can be applied in the field of electrochemical testing.

[0046] Example 3

[0047] The storage stability of the conductive hydrogel / graphene oxide / carbon cloth Ag / AgCl reference electrode was tested after storage for 3 days, 60 days, 120 days and 180 days without nitrogen protection.

[0048] The three-electrode system consists of a glassy carbon electrode as the working electrode, a platinum wire as the counter electrode, and the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl electrode prepared in Example 1 as the reference electrode.

[0049] The self-made reference electrode was stored without nitrogen protection for 3 days, 60 days, 120 days and 180 days, and its storage stability was tested. Figure 7 .Depend on Figure 7 It can be seen that the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode prepared in Example 1 of the present invention is very stable after 2 months of storage, and the ΔE increases slightly after 4 and 6 months of storage. This shows that the conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl reference electrode prepared in Example 1 has excellent storage stability.

[0050] Example 4

[0051] Application of conductive hydrogel / graphene oxide / carbon cloth Ag / AgCl reference electrode for detection of ethanol by cyclic voltammetry.

[0052] The three-electrode system consists of an Au-AgNWs electrode as a working electrode, a platinum wire as a counter electrode, and the conductive hydrogel / graphene oxide / carbon cloth Ag / AgCl electrode prepared in Example 1 as a reference electrode.

[0053] Cyclic voltammetry was used to detect the ions in 10 mM ethanol solution (0.1 M KOH). Figure 8This is a comparison chart of the oxidation peaks of the homemade Ag / AgCl flexible reference electrode and the commercial Ag / AgCl reference electrode in detecting ethanol solution. It can be clearly seen that the oxidation peak current of the homemade Ag / AgCl flexible reference electrode is higher than that of the commercial Ag / AgCl reference electrode (manufacturer: Tianjin Lanlike Chemical Electronics High-Tech Co., Ltd.), which can be used for the efficient detection of ethanol.

[0054] Comparative Example

[0055] At present, electrochemical measurements are no longer limited to laboratories, and the requirements for the performance of the reference electrode itself, such as stability and high selectivity, are becoming increasingly higher. Therefore, the application scope of traditional rigid reference electrodes is greatly limited. With the emergence of various new materials, their status in the medical and health fields is becoming increasingly important. Although the preparation method of the reference electrode has been widely reported, the present invention is very different from the contents disclosed in the patent literature and articles in the prior art in terms of electrode materials, preparation methods, electrode nanostructures and application scenarios. The following table lists the comparison between the present invention and the prior art reference electrode:

[0056] Table 1 Comparison of the present invention and the prior art reference electrodes

[0057]

[0058]

[0059] As can be seen from the contents recorded in the above table, the Ag / AgCl reference electrode prepared with graphene oxide and carbon cloth has not been reported in any previous patents and articles, and the present invention is also very different from previous reports in terms of electrode materials, preparation methods, obtained nanostructures and application scenarios. The present invention uses an electrochemical method to prepare the Ag / AgCl reference electrode, which is low in cost and can also obtain nanoparticles of different deposition amounts and shapes by changing electrochemical parameters. Carbon cloth and graphene oxide are used as substrates, which is conducive to the uniform deposition of the Ag layer. Compared with the traditional reference electrode, the electrode prepared by the preparation method provided by the present invention uses a dual-carbon material as a substrate, which greatly improves the electrical conductivity of the electrode substrate, thereby improving the stability and service life of the reference electrode. For the first time, a conductive hydrogel prepared with a saturated KCl solution is proposed as an encapsulating membrane. The encapsulating membrane has good ion permeability and can prevent the Ag / AgCl layer from falling off. The present invention is original in terms of the preparation of electrode materials and encapsulating membranes.

[0060] The references cited above are as follows:

[0061] [1] Sun Jing, Wang Qingxiang, Shen Guijun, Lang Mingfei. Preparation method and application of Ag / AgCl microelectrode encapsulation membrane based on PDMS[P]. CN108181364B, 2020-05-19.

[0062] [2] Sun Jing, Wang Qingxiang, Shen Guijun, Lang Mingfei. A method for preparing a reusable PDMS-based Ag / AgCl microelectrode and its application [P]. CN108195911A, 2018-06-22.

[0063] [3]Anyszka,R.,Bieliński,DM, Z.et al.Effect of mineral filleradditives on flammability,processing and use of silicone-based ceramifiablecomposites.Polym.Bull.75,1731–1751(2018).

[0064] [4]Rius-Ruiz F Xavier et al.Disposable planar reference electrodebased on carbon nanotubes and polyacrylate membrane.[J].Analytical chemistry, 2011,83(14):5783-8.

[0065] [5] Li Hongxia, Song Yusu, Xiao Haijian. Preparation and performance of sodium bicarbonate modified Ag / AgCl ocean electric field electrode[J]. Acta Armamentarii, 2022, 43(01): 226-232.

[0066] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. Any obvious modifications made by a person skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a flexible reference electrode, characterized in that the steps include: S1: Preparation of graphene oxide / carbon cloth flexible substrate; S2: Preparation of Ag / AgCl layer; A petal-shaped Ag / AgCl reference electrode was prepared on a graphene oxide / carbon cloth flexible substrate by first electrochemically depositing a silver layer and then electrochemically chlorinating the surface. The conditions for the electrochemical deposition of silver layer are as follows: deposition time 2500s~3500s, deposition potential -0.4V~-0.8V, and electrochemical chlorination conditions are as follows: chlorination time 2600s~3600s, chlorination potential 100mV~500mV. S3: Conductive hydrogel was used as an encapsulating membrane to encapsulate the graphene oxide / carbon cloth-Ag / AgCl electrode to prepare a conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl flexible reference electrode; Step S3 is as follows: The hydrogel was prepared by a one-step freeze-thaw method. Glycerol / water (a 1:1 mass ratio of glycerol to water) was used as a co-solvent, and tannic acid was used as a cross-linker. PVA powder was dissolved at a temperature between 90 and 100°C. After the PVA was completely dissolved, a PVA mixed solution was obtained. The dried graphene oxide / carbon cloth-Ag / AgCl electrode was placed in a petri dish, and the PVA mixed solution was evenly poured on the electrode surface. The electrode was then placed at -20°C for 2 h to obtain a graphene oxide / carbon cloth-Ag / AgCl electrode with a polyvinyl alcohol hydrogel as the encapsulating membrane. The electrode was then immersed in a saturated KCl solution for 16 h and then dried in a vacuum oven at 20°C-50°C for 2-4 h to obtain a conductive hydrogel / graphene oxide / carbon cloth-Ag / AgCl flexible reference electrode. The flexible reference electrode is used for detecting ethanol solution.

2. The method for preparing a flexible reference electrode according to claim 1, wherein: The step S1 is specifically as follows: (1) Prepare a piece of carbon cloth as a substrate, place it in ultrapure water, acetone, and ethanol for ultrasonic cleaning for 30 minutes to remove surface impurities, then soak the carbon cloth in a 0.1 M to 0.5 M hydrochloric acid solution for 5 hours to 8 hours for acidification modification, and dry it at room temperature for later use; (2) Soaking the carbon cloth after acidification treatment in step (1) in 1 mg / mL~5 mg / mL polydimethyl ammonium chloride solution for 30 min; (3) Finally, a layer of graphene oxide solution is evenly coated on the carbon cloth substrate after modification in step (2). The concentration of the graphene oxide solution is 1 mg / mL~5 mg / mL, and the solution is dried at room temperature to obtain a graphene oxide / carbon cloth substrate.

3. The method for preparing a flexible reference electrode according to claim 1, wherein: The step S2 is specifically as follows: (1) Using a three-electrode system, the flexible substrate prepared in step S1 was used as the working electrode, a saturated calomel electrode was used as the reference electrode, and a platinum wire was used as the counter electrode. The electrodes were placed in a mixed solution of 0.02M to 0.07M AgNO3 and 0.2M to 0.7M NaNO3, and silver nanoparticles were electrochemically deposited using chronoamperometry to prepare an Ag-graphene oxide / carbon cloth electrode. (2) A three-electrode system was used, with the Ag-graphene oxide / carbon cloth electrode as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. The three-electrode system was placed in a 0.2 M~0.7 M HCl solution, and the Ag-graphene oxide / carbon cloth electrode was chlorinated by electrochemical chlorination to prepare a graphene oxide / carbon cloth-Ag / AgCl reference electrode.

4. A flexible reference electrode, characterized in that The method is prepared according to any one of claims 1 to 3.

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