A kind of Ag / Ag2O electrochemical reference electrode and preparation method thereof

Abstract

The present invention discloses an Ag / Ag2O electrochemical reference electrode and a preparation method thereof. The reference electrode is prepared by immersing a silver substrate covered with a silver oxide coating or an inert conductive substrate coated with a silver and silver oxide mixture coating in an insulating cavity containing a replaceable alkaline solution, and the conductive substrate is led out of the sealed cavity by a wire. The silver substrate covered with the silver oxide coating can be prepared by electrolysis or coating. The reference electrode has non-toxic and environmentally friendly properties and is particularly suitable for reference electrodes in alkaline electrolytes in electrochemical or electroanalysis related fields.

Description

Technical Field

[0001] The invention belongs to the field of electrochemical science and technology, and specifically relates to an Ag / Ag2O electrochemical reference electrode and a preparation method thereof. Background Art

[0002] The invention of the Voltaic pile in 1800 marked the beginning of the development of electrochemistry. Today, electrochemistry permeates all aspects of modern manufacturing, from the manufacture and packaging of integrated circuits, from mobile power supplies in mobile phones to electric vehicles, electrochemistry plays a very important role.

[0003] As an indispensable type of electrode in electrochemical measurements, reference electrodes play a very important role in basic research and applications related to electrochemistry.

[0004] The ideal reference electrode in electrochemistry is the standard hydrogen electrode (SHE), which is defined as the potential of the hydrogen electrode under standard conditions at any temperature is zero, and the potential of any electrode is the potential of the battery composed of the electrode and the standard hydrogen electrode. The above standard state refers to the state where the hydrogen ion activity in the electrolyte of the hydrogen electrode is 1 and the pressure of hydrogen is 100kpa (about one atmosphere), so the temperature coefficient of the standard hydrogen electrode is zero.

[0005] The hydrogen electrode is made by immersing a platinum sheet coated with platinum black into a solution containing hydrogen ions, and passing hydrogen gas to make the platinum black adsorb hydrogen until saturated. In actual use, the hydrogen electrode is not commonly used because a stable high-purity hydrogen flow should pass through the solution, and the platinum sheet in the hydrogen electrode is easily poisoned, making it inconvenient to use and maintain.

[0006] At present, the reference electrodes commonly used in laboratories are mercury-based reference electrodes, mainly calomel electrodes (Hg / Hg2Cl2 electrodes) used in neutral aqueous solutions, Hg / HgO electrodes used in alkaline solutions, and Hg / Hg2SO4 electrodes used to avoid the influence of chloride ions. The above mercury-based reference electrodes have stable potential and good reproducibility, and have been widely used.

[0007] However, mercury is a highly toxic heavy metal element. No matter what form it exists in, it has different degrees of toxicity. Mercury-based reference electrodes are inevitably harmful to the human body and cause serious pollution to the environment during the production, use and disposal of waste electrodes. Therefore, the development and promotion of the use of non-mercury-based reference electrodes has important research significance and application value for the earth's natural environment and human health.

[0008] At present, a relatively mature non-mercury-based reference electrode is the silver-based Ag / AgCl reference electrode for neutral aqueous solution. This electrode is simple to make, non-toxic, and has very good potential reproducibility. It can basically replace the calomel electrode (Hg / Hg2Cl2) reference electrode. At present, many types of battery reactions and chemical production are carried out in an alkaline environment. It is of great significance to manufacture a reference electrode that can replace the Hg / HgO used in toxic alkaline solutions. Summary of the invention

[0009] The invention patent proposes a silver-based Ag / Ag2O electrochemical reference electrode that can be used under alkaline conditions and has stable potential, which is used to replace the more toxic Hg / HgO reference electrode.

[0010] To achieve the above object, the technical solution of the present invention is:

[0011] An Ag / Ag2O electrochemical reference electrode comprises a silver substrate covered with a silver oxide coating, or an inert conductive substrate coated with a silver and silver oxide mixture coating on the surface, one end of the substrate is immersed in an insulating cavity containing an internal filling liquid, and the other end is led out of the insulating cavity by a wire, and a through hole filled with a porous material is arranged at the bottom of the insulating cavity.

[0012] Furthermore, the internal filling liquid is an alkaline solution, specifically but not limited to LiOH solution, NaOH solution, KOH solution, Ca(OH)2 solution, Ba(OH)2 solution, Na2CO3-NaHCO3 buffer solution with a concentration ranging from 0.01 M to its saturated solution concentration.

[0013] Furthermore, the through hole can allow the solution inside the insulating cavity to communicate with the solution outside, wherein the porous material is porous ceramic, porous glass or fiber.

[0014] Furthermore, the lead wires include copper wires, silver wires or the same conductive material as the substrate.

[0015] Furthermore, the material of the insulating cavity shell is glass, with a liquid injection hole left at its upper side end; or plastic, divided into two parts that can be unscrewed and fastened up and down, for injecting and replenishing the internal filling liquid.

[0016] Furthermore, the plastic includes one of polytetrafluoroethylene, polyvinyl chloride, polyethylene, polypropylene, polystyrene, ABS plastic, polyamide, polycarbonate, polyoxymethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, polyetheretherketone and plexiglass.

[0017] The preparation method of the Ag / Ag2O electrochemical reference electrode is as follows: a silver substrate (1-1) covered with a silver oxide coating, or an inert conductive substrate coated with a silver and silver oxide mixture coating, is immersed in an insulating cavity containing an alkaline solution and embedded with a porous material at the lower end, and a lead wire is connected to make it.

[0018] Furthermore, a method for preparing a silver substrate covered with a silver oxide coating is as follows: inserting a silver wire and an inert counter electrode into an alkaline electrolyte, connecting the silver wire to the positive electrode of a DC power supply, and connecting the inert counter electrode to the negative electrode of the power supply, and applying a current density of 0.001 to 10 mA / cm 2 The electrolysis current is 200 to 300 min, and the electrolysis time is 1 to 300 min; wherein the alkaline electrolyte is (but not limited to) LiOH, NaOH, KOH, or Ba(OH)2 solution with a concentration ranging from 0.01 M to its saturated solution concentration.

[0019] Furthermore, another method for preparing a silver substrate covered with a silver oxide coating is as follows: silver oxide particles and a thickener are mixed, an appropriate amount of deionized water is added to prepare a silver oxide slurry, the slurry is coated on the silver substrate, and the slurry is dried. The thickener is (but not limited to) sodium polyacrylate or methyl cellulose.

[0020] Furthermore, the preparation method of the inert conductive substrate coated with a coating of a mixture of silver and silver oxide is as follows: silver particles, silver oxide particles and a thickener are mixed, and then an appropriate amount of deionized water is added to prepare an Ag / Ag2O slurry, which is coated on an inert conductor and dried, wherein the thickener is (but not limited to) sodium polyacrylate or methyl cellulose, and the inert conductive substrate is (but not limited to) platinum wire, carbon rod or titanium rod.

[0021] Furthermore, the alkaline solution contained in the reference electrode is but not limited to LiOH, NaOH, KOH, Ba(OH)2 solution, saturated Ca(OH)2 solution, or Na2CO3-NaHCO3 buffer solution with a concentration of 0.01 M to 6 M.

[0022] Beneficial effects: The Ag / Ag2O electrochemical reference electrode prepared by the present invention is simple, rapid, green and non-toxic, has a stable potential in an alkaline environment, and can replace the Hg / HgO reference electrode during the measurement process. The electrode reaction of the Ag / Ag2O electrode is:

[0023] Ag2O + H2O + 2e - ⇌ 2Ag + 2OH -

[0024] Its standard electrode potential E 0 Ag / Ag2O = 0.342 V ( vs. SHE).

[0025] The electrode reaction of the Hg / HgO reference electrode containing mercury is:

[0026] HgO + H2O + 2e - ⇌ Hg + 2OH -

[0027] Its standard electrode potential E 0 Hg / HgO = 0.098 V ( vs. SHE).

[0028] The standard electrode potential of the Ag / Ag2O reference electrode is 0.244 V higher than that of the Hg / HgO reference electrode.

[0029] E 0 Ag / Ag2O - E 0 Hg / HgO = 0.244 V. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of the Ag / Ag2O electrochemical reference electrode prepared in Example 1;

[0031] Figure 2 Schematic diagram of the structure of the Ag / Ag2O electrochemical reference electrode prepared in Example 2;

[0032] In the figure: 1-1 is Ag wire, 1-2 is Ag / Ag2O substrate, 1-3 and 2-3 are both filled with liquid, 1-4 is a glass insulating cavity, 1-6 and 2-6 are both porous ceramics, 1-7 is a liquid injection hole, 2-1 is a Pt wire, 2-2 is an Ag / Ag2O substrate, 2-4 is an upper polytetrafluoroethylene insulating cavity, 2-5 is a lower polytetrafluoroethylene insulating cavity, and 2-8 is a sealing joint. DETAILED DESCRIPTION

[0033] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0034] Example 1

[0035] like Figure 1As shown, an Ag / Ag2O electrochemical reference electrode includes an Ag wire substrate 1-2 covered with a silver oxide coating, one end of the substrate is immersed in a glass insulating cavity 1-4 containing an internal filling liquid 1-3, and the other end is led out of the glass insulating cavity 1-4 by an Ag wire 1-1, and a through hole filled with porous ceramic 1-6 is provided at the bottom of the glass insulating cavity, and the internal filling liquid 1-3 is a 0.1M NaOH solution, which is injected through an injection hole 1-7 on the upper side of the glass insulating cavity.

[0036] Preparation method of Ag / Ag2O electrochemical reference electrode in this embodiment:

[0037] (1) Connect the Ag wire and Pt wire to the positive and negative electrodes of a DC power supply respectively, and place them in a 0.01M ~ 1.0M LiOH electrolytic solution with a current density of 0.1mA / cm 2 , the power-on time is 10 min, and the Ag / Ag2O substrate is prepared;

[0038] (2) One end of the Ag / Ag2O substrate was immersed in a glass insulating cavity containing 0.1 M NaOH, and the other end was led out of the glass insulating cavity with a Ag wire. The through hole at the bottom of the glass insulating cavity was filled with porous ceramics to make an Ag / Ag2O electrochemical reference electrode.

[0039] Example 2

[0040] The structure of the Ag / Ag2O electrochemical reference electrode in this embodiment is the same as that in Embodiment 1, except that a 0.01M to 1.0M NaOH electrolytic solution is used in the method for preparing the Ag / Ag2O substrate.

[0041] Example 3

[0042] The structure of the Ag / Ag2O electrochemical reference electrode of this embodiment is the same as that of Embodiment 1, except that the internal filling liquid is 0.01M KOH solution, and the method for preparing the Ag / Ag2O substrate adopts 0.01M ~ 1.0 M KOH electrolytic solution.

[0043] Example 4

[0044] The structure of the Ag / Ag2O electrochemical reference electrode in this embodiment is the same as that in Embodiment 1, except that the internal filling liquid is a saturated Ca(OH)2 solution, and a 6M NaOH electrolytic solution is used in the method for preparing the Ag / Ag2O substrate.

[0045] Example 5

[0046] The structure of the Ag / Ag2O electrochemical reference electrode in this embodiment is the same as that in Embodiment 1, except that the internal filling liquid is a saturated Ca(OH)2 solution, and a 0.1 M Ba(OH)2 electrolytic solution is used in the method for preparing the Ag / Ag2O substrate.

[0047] Example 6

[0048] The structure of the Ag / Ag2O electrochemical reference electrode in this embodiment is the same as that in Embodiment 1, except that the internal filling liquid is a saturated Ca(OH)2 solution, and a 0.1 M Ba(OH)2 electrolytic solution is used in the method for preparing the Ag / Ag2O substrate.

[0049] Example 7

[0050] The structure of the Ag / Ag2O electrochemical reference electrode in this embodiment is the same as that in Embodiment 1, except that the internal filling liquid is a 0.5MNa2CO3-0.5M NaHCO3 buffer solution, and the method for preparing the Ag / Ag2O substrate uses a 0.01M ~ 1.0 M NaOH electrolytic solution.

[0051] Example 8

[0052] like Figure 2 As shown, an Ag / Ag2O electrochemical reference electrode comprises a Pt wire substrate 2-2 coated with a silver and silver oxide mixture coating, one end of the substrate is immersed in a polytetrafluoroethylene insulation cavity containing an internal filling liquid 2-3, and the other end is led out of the polytetrafluoroethylene insulation cavity by a Pt wire 2-1, the polytetrafluoroethylene insulation cavity is composed of an upper polytetrafluoroethylene insulation cavity 2-4 and a lower polytetrafluoroethylene insulation cavity 2-5, the upper polytetrafluoroethylene insulation cavity 2-4 and the lower polytetrafluoroethylene insulation cavity 2-5 are connected by a sealing joint 2-8, the bottom of the lower polytetrafluoroethylene insulation cavity 2-5 is provided with a through hole filled with porous ceramic 2-6, the internal filling liquid 2-3 is a 0.1M NaOH solution, and is injected and replenished by unscrewing the sealing joint (2-8) of the upper polytetrafluoroethylene insulation cavity (2-4) and the lower polytetrafluoroethylene insulation cavity (2-5).

[0053] Preparation method of Ag / Ag2O electrochemical reference electrode in this embodiment:

[0054] (1) Using Pt wire as a substrate, 0.5 g of silver oxide particles and 0.5 g of silver particles were mixed, 4 mg of methyl cellulose and 1 mL of deionized water were added to prepare Ag / Ag2O slurry, which was coated on the Pt wire and dried to prepare a Pt wire substrate coated with a mixture of silver and silver oxide;

[0055] (2) One end of a Pt wire substrate coated with a mixture of silver and silver oxide was immersed in a polytetrafluoroethylene insulating cavity containing 0.1 M NaOH, and the other end was led out of the polytetrafluoroethylene insulating cavity by a Pt wire. The through holes at the bottom of the polytetrafluoroethylene insulating cavity were filled with porous ceramics to prepare an Ag / Ag2O electrochemical reference electrode.

[0056] Example 9

[0057] An Ag / Ag2O electrochemical reference electrode comprises an Ag wire substrate 2-2 coated with a silver oxide coating, one end of the substrate is immersed in a polytetrafluoroethylene insulation cavity containing an internal filling liquid 2-3, and the other end is led out of the polytetrafluoroethylene insulation cavity by a Pt wire 2-1, the polytetrafluoroethylene insulation cavity is composed of an upper polytetrafluoroethylene insulation cavity 2-4 and a lower polytetrafluoroethylene insulation cavity 2-5, the upper polytetrafluoroethylene insulation cavity 2-4 and the lower polytetrafluoroethylene insulation cavity 2-5 are connected by a sealing joint 2-8, the bottom of the lower polytetrafluoroethylene insulation cavity 2-5 is provided with a through hole filled with porous ceramics 2-6, the internal filling liquid 2-3 is a 0.1M NaOH solution, and is injected and replenished by unscrewing the sealing joints (2-8) of the upper polytetrafluoroethylene insulation cavity (2-4) and the lower polytetrafluoroethylene insulation cavity (2-5).

[0058] Preparation method of Ag / Ag2O electrochemical reference electrode in this embodiment:

[0059] (1) With Ag wire as the substrate, 1 g of silver oxide particles and 4 mg of sodium polyacrylate were mixed, 1 mL of deionized water was added to prepare Ag2O slurry, which was coated on the Ag wire and dried to prepare an Ag wire substrate coated with a mixture of silver and silver oxide;

[0060] (2) One end of the Ag wire substrate coated with a mixture of silver and silver oxide was immersed in a polytetrafluoroethylene insulating cavity containing 0.1 M NaOH, and the other end was led out of the polytetrafluoroethylene insulating cavity with a Pt wire. The through holes at the bottom of the polytetrafluoroethylene insulating cavity were filled with porous ceramics to prepare a Ag / Ag2O electrochemical reference electrode.

[0061] Example 10

[0062] An Ag / Ag2O electrochemical reference electrode comprises a Pt wire substrate 2-2 coated with a silver and silver oxide mixture coating, one end of the substrate is immersed in a polytetrafluoroethylene insulation cavity containing an internal filling liquid 2-3, and the other end is led out of the polytetrafluoroethylene insulation cavity by a Pt wire 2-1, the polytetrafluoroethylene insulation cavity is composed of an upper polytetrafluoroethylene insulation cavity 2-4 and a lower polytetrafluoroethylene insulation cavity 2-5, the upper polytetrafluoroethylene insulation cavity 2-4 and the lower polytetrafluoroethylene insulation cavity 2-5 are connected by a sealing joint 2-8, the bottom of the lower polytetrafluoroethylene insulation cavity 2-5 is provided with a through hole filled with porous ceramic 2-6, the internal filling liquid 2-3 is a 0.1M NaOH solution, and is injected and replenished by unscrewing the sealing joints (2-8) of the upper polytetrafluoroethylene insulation cavity (2-4) and the lower polytetrafluoroethylene insulation cavity (2-5).

[0063] Preparation method of Ag / Ag2O electrochemical reference electrode in this embodiment:

[0064] (1) Using Pt wire as a substrate, 0.5 g of silver oxide particles and 0.5 g of silver particles were mixed, 4 mg of sodium polyacrylate and 1 mL of deionized water were added to prepare Ag / Ag2O slurry, which was coated on the Pt wire and dried to prepare a Pt wire substrate coated with a mixture of silver and silver oxide;

[0065] (2) One end of a Pt wire substrate coated with a mixture of silver and silver oxide was immersed in a polytetrafluoroethylene insulating cavity containing 0.1 M NaOH, and the other end was led out of the polytetrafluoroethylene insulating cavity by a Pt wire. The through holes at the bottom of the polytetrafluoroethylene insulating cavity were filled with porous ceramics to prepare an Ag / Ag2O electrochemical reference electrode.

[0066] Embodiment 11

[0067] An Ag / Ag2O electrochemical reference electrode comprises a carbon rod substrate 2-2 coated with a silver and silver oxide mixture coating, one end of the substrate is immersed in a polytetrafluoroethylene insulation cavity containing an internal filling liquid 2-3, and the other end is led out of the polytetrafluoroethylene insulation cavity by a Pt wire 2-1, the polytetrafluoroethylene insulation cavity is composed of an upper polytetrafluoroethylene insulation cavity 2-4 and a lower polytetrafluoroethylene insulation cavity 2-5, the upper polytetrafluoroethylene insulation cavity 2-4 and the lower polytetrafluoroethylene insulation cavity 2-5 are connected by a sealing joint 2-8, the bottom of the lower polytetrafluoroethylene insulation cavity 2-5 is provided with a through hole filled with porous ceramic 2-6, the internal filling liquid 2-3 is a 0.1M NaOH solution, and is injected and replenished by unscrewing the sealing joints (2-8) of the upper polytetrafluoroethylene insulation cavity (2-4) and the lower polytetrafluoroethylene insulation cavity (2-5).

[0068] Preparation method of Ag / Ag2O electrochemical reference electrode in this embodiment:

[0069] (1) Using a carbon rod as a substrate, 0.5 g of silver oxide particles and 0.5 g of silver particles were mixed, 4 mg of sodium polyacrylate and 1 mL of deionized water were added to prepare an Ag / Ag2O slurry, which was coated on the carbon rod and dried to prepare a carbon rod substrate coated with a mixture of silver and silver oxide;

[0070] (2) One end of a carbon rod substrate coated with a mixture of silver and silver oxide was immersed in a polytetrafluoroethylene insulating cavity containing 0.1 M NaOH, and the other end was led out of the polytetrafluoroethylene insulating cavity with a Pt wire. The through holes at the bottom of the polytetrafluoroethylene insulating cavity were filled with porous ceramics to prepare an Ag / Ag2O electrochemical reference electrode.

[0071] Embodiment 11

[0072] An Ag / Ag2O electrochemical reference electrode comprises a carbon rod substrate 2-2 coated with a silver and silver oxide mixture coating, one end of the substrate is immersed in a polytetrafluoroethylene insulation cavity containing an internal filling liquid 2-3, and the other end is led out of the polytetrafluoroethylene insulation cavity by a Pt wire 2-1, the polytetrafluoroethylene insulation cavity is composed of an upper polytetrafluoroethylene insulation cavity 2-4 and a lower polytetrafluoroethylene insulation cavity 2-5, the upper polytetrafluoroethylene insulation cavity 2-4 and the lower polytetrafluoroethylene insulation cavity 2-5 are connected by a sealing joint 2-8, the bottom of the lower polytetrafluoroethylene insulation cavity 2-5 is provided with a through hole filled with porous ceramic 2-6, the internal filling liquid 2-3 is a 0.1M NaOH solution, and is injected and replenished by unscrewing the sealing joints (2-8) of the upper polytetrafluoroethylene insulation cavity (2-4) and the lower polytetrafluoroethylene insulation cavity (2-5).

[0073] Preparation method of Ag / Ag2O electrochemical reference electrode in this embodiment:

[0074] (1) Using a carbon rod as a substrate, 0.5 g of silver oxide particles and 0.5 g of silver particles were mixed, 4 mg of methyl cellulose and 1 mL of deionized water were added to prepare an Ag / Ag2O slurry, which was coated on the carbon rod and dried to prepare a carbon rod substrate coated with a mixture of silver and silver oxide;

[0075] (2) One end of a carbon rod substrate coated with a mixture of silver and silver oxide was immersed in a polytetrafluoroethylene insulating cavity containing 0.1 M NaOH, and the other end was led out of the polytetrafluoroethylene insulating cavity with a Pt wire. The through holes at the bottom of the polytetrafluoroethylene insulating cavity were filled with porous ceramics to prepare an Ag / Ag2O electrochemical reference electrode.

[0076] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing an Ag / Ag2O electrochemical reference electrode, characterized in that: A silver substrate covered with a silver oxide coating, or an inert conductive substrate coated with a mixture of silver and silver oxide, is immersed in an insulating cavity filled with an alkaline electrolyte, and the conductive substrate is led out of the insulating cavity with a wire; a through hole filled with a porous material is provided at the bottom of the insulating cavity; The preparation method of the silver substrate covered with the silver oxide coating is to insert a silver wire and an inert counter electrode into an electrolyte, connect the silver wire to the positive electrode of a DC power supply, connect the inert counter electrode to the negative electrode of the power supply, and apply a current density of 0.001 to 10 mA / cm 2 The silver substrate covered with the silver oxide coating is obtained by electrolyzing with an electrolytic current of 1 to 300 min; wherein the electrolyte comprises LiOH, NaOH, KOH or Ca(OH)2 solution; or the silver oxide particles and a thickener are mixed and then added to deionized water to prepare a silver oxide slurry, which is then coated on the silver substrate and dried, wherein the thickener comprises sodium polyacrylate or methyl cellulose; The inert conductive substrate coated with a coating of a mixture of silver and silver oxide is prepared by mixing silver particles, silver oxide particles and the thickener, adding ionized water to prepare a mixed slurry of silver and silver oxide, coating the mixed slurry on an inert conductor, and drying the mixed slurry. The thickener comprises sodium polyacrylate or methyl cellulose, and the inert conductive substrate comprises platinum wire, carbon rod or titanium rod.

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