A ruthenium oxide electrode and its preparation method and application

Abstract

This invention relates to the field of electrochemical sensor technology, and more particularly to a ruthenium oxide electrode, its preparation method, and its applications. The preparation method provided by this invention includes dipping one end of a metal wire in a ruthenium chloride precursor solution and drying it, then inserting it into a mixed powder of lithium carbonate and sodium peroxide for heat treatment to obtain a metal wire with one end coated with a ruthenium oxide film; cleaning the ruthenium oxide film in the metal wire with one end coated with dilute nitric acid; wrapping the non-ruthenium oxide film region of the metal wire with one end coated with ruthenium oxide film with polytetrafluoroethylene heat shrink tubing; and aging to obtain the ruthenium oxide electrode. The ruthenium oxide electrode prepared by this method has the characteristics of being portable, simple to operate, robust and pressure-resistant, capable of in-situ measurement, highly sensitive, and efficient and accurate, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensor technology, and in particular to a ruthenium oxide electrode, its preparation method, and its application. Background Technology

[0002] The pH value of water is one of the important parameters reflecting the aquatic environment, especially for the ocean. Therefore, it is of great significance to develop an all-solid-state pH sensor that is portable, easy to operate, robust and pressure resistant, capable of in-situ measurement, sensitive and efficient.

[0003] The pH value of water can be determined by electrochemical or spectrophotometric methods. Electrochemical methods mainly measure the pH value of water using pH electrodes, often glass pH electrodes, which are fragile and not pressure-resistant. Spectrophotometric methods calculate the pH value by comparing the absorbance values ​​of water with and without added dyes in a specific wavelength range. This method is time-consuming, costly, requires large testing instruments, and involves complex operations. Summary of the Invention

[0004] The purpose of this invention is to provide a ruthenium oxide electrode, its preparation method, and its application. The ruthenium oxide electrode prepared by the method is characterized by being portable, easy to operate, robust and pressure resistant, capable of in-situ measurement, highly sensitive, and efficient and accurate.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a ruthenium oxide electrode, comprising the following steps:

[0007] One end of a metal wire is dipped in a ruthenium chloride precursor solution and dried. Then it is inserted into a mixed powder of lithium carbonate and sodium peroxide and subjected to heat treatment to obtain a metal wire with a ruthenium oxide film coated on one end.

[0008] The ruthenium oxide film in the metal wire with one end covered by a ruthenium oxide film is cleaned with dilute nitric acid. Then, polytetrafluoroethylene heat shrink tubing is wrapped around the non-ruthenium oxide film area in the metal wire with one end covered by a ruthenium oxide film, and the material is aged to obtain the ruthenium oxide electrode.

[0009] Preferably, the metal wire is titanium wire, gold wire, silver wire or copper wire.

[0010] Preferably, when one end of the metal wire is dipped into the ruthenium chloride precursor solution, the length of the dipped end of the metal wire is 1 to 1.5 cm.

[0011] The drying process is performed using a hot air gun; the temperature of the hot air gun is 300–350°C.

[0012] The dipping and drying process is repeated 20 to 100 times.

[0013] Preferably, the metal wire is further subjected to pretreatment before being dipped into the ruthenium chloride precursor solution;

[0014] The pretreatment includes grinding, polishing, and ultrasonic treatment performed sequentially.

[0015] Preferably, the solvent of the ruthenium chloride precursor solution includes glycerol and dilute hydrochloric acid, wherein the concentration of the dilute hydrochloric acid is 0.01 mol / L;

[0016] The volume ratio of glycerol to dilute hydrochloric acid is (1-3):1;

[0017] The concentration of ruthenium chloride in the ruthenium chloride precursor solution is 0.01 mol / L.

[0018] Preferably, the molar ratio of lithium carbonate to sodium peroxide in the mixed powder of lithium carbonate and sodium peroxide is (9-5):(1-5).

[0019] Preferably, the heat treatment temperature is 400-480℃, and the holding time is 5h.

[0020] Preferably, the aging solution used in the aging process has a pH value of 4, the aging temperature is room temperature, and the aging time is 1 to 14 days.

[0021] The present invention also provides a ruthenium oxide electrode prepared by the preparation method described above, comprising a metal wire, a ruthenium oxide film covering one end of the metal wire, and a polytetrafluoroethylene heat shrink tubing covering the non-ruthenium oxide film region of the metal wire.

[0022] The present invention also provides the application of the ruthenium oxide electrode described in the above technical solution in measuring the pH of water.

[0023] This invention provides a method for preparing a ruthenium oxide electrode, comprising the following steps: dipping one end of a metal wire in a ruthenium chloride precursor solution and drying it, then inserting it into a mixed powder of lithium carbonate and sodium peroxide, and performing heat treatment to obtain a metal wire with one end coated with a ruthenium oxide film; cleaning the ruthenium oxide film in the metal wire with one end coated with dilute nitric acid; wrapping the non-ruthenium oxide film area in the metal wire with one end coated with ruthenium oxide film with polytetrafluoroethylene heat shrink tubing, and aging it to obtain the ruthenium oxide electrode. Compared with commercially available glass pH electrodes and spectrophotometry, the ruthenium oxide electrode prepared by this method has advantages such as portability, simple operation, robustness and pressure resistance, in-situ measurement, sensitive response, and high efficiency and accuracy; it also has good Nernst response and high goodness of fit (R0). 2Advantages include (e.g., 0.999). The ruthenium oxide electrode prepared by the method described in this invention is adaptable to pH measurement in complex water bodies, providing rapid and accurate measurements with excellent practical performance. It can be applied to in-situ pH measurement in seawater, and also to pH measurement in other water bodies. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the ruthenium oxide electrode described in this invention;

[0025] Figure 2 This is a SEM image of the ruthenium oxide thin film of the ruthenium oxide electrode described in Example 1;

[0026] Figure 3 The potential response diagrams of the ruthenium oxide electrode described in Example 1 in buffer solutions with pH values ​​of 4, 7, and 10 are shown.

[0027] Figure 4 The linear fitting graphs of the ruthenium oxide electrode described in Example 1 in buffer solutions with pH values ​​of 4, 7, and 10 are shown.

[0028] Figure 5 This is a measurement diagram of the ruthenium oxide electrode described in Example 1 in seawater at Huimin Bridge Wharf in Zhoushan City, Zhejiang Province. Detailed Implementation

[0029] This invention provides a method for preparing a ruthenium oxide electrode, comprising the following steps:

[0030] One end of a metal wire is dipped in a ruthenium chloride precursor solution and dried. Then it is inserted into a mixed powder of lithium carbonate and sodium peroxide and subjected to heat treatment to obtain a metal wire with a ruthenium oxide film coated on one end.

[0031] The ruthenium oxide film in the metal wire with one end covered by a ruthenium oxide film is cleaned with dilute nitric acid. Then, polytetrafluoroethylene heat shrink tubing is wrapped around the non-ruthenium oxide film area in the metal wire with one end covered by a ruthenium oxide film, and the material is aged to obtain the ruthenium oxide electrode.

[0032] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0033] In this invention, the metal wire is preferably titanium wire, gold wire, silver wire or copper wire.

[0034] In this invention, the length of the metal wire is preferably 3 to 7 cm, more preferably 4 to 6 cm; the diameter of the metal wire is preferably 0.1 to 1 mm, more preferably 0.1 to 0.5 mm.

[0035] In this invention, when one end of the metal wire is dipped into the ruthenium chloride precursor solution, the length of the dipped end is preferably 1 to 1.5 cm. This invention does not impose any special limitations on the dipping process; any process well-known to those skilled in the art can be used.

[0036] Before the metal wire is dipped into the ruthenium chloride precursor solution, the present invention preferably includes pretreatment of the metal wire; the pretreatment preferably includes sequential grinding, polishing, and ultrasonic treatment; the ultrasonic treatment preferably includes sequential ultrasonic treatment with dilute nitric acid and ultrasonic treatment with anhydrous ethanol. Before grinding, the present invention preferably cleans the surface of the metal wire with deionized water. In the present invention, the grinding is preferably performed sequentially using 1200-grit, 5000-grit, and 7000-grit sandpaper, with each grinding cycle of 20-100 times followed by ultrasonic cleaning with deionized water for 1-5 minutes. In the present invention, the polishing treatment is preferably performed sequentially using 1μm, 0.3μm, and 0.05μm alumina powder, with each polishing cycle of 20-100 times followed by ultrasonic cleaning with deionized water for 1-5 minutes. In the present invention, the concentration of the dilute nitric acid used in the dilute nitric acid treatment is preferably 0.1-1 mol / L. In this invention, the dilute nitric acid treatment is preferably performed under ultrasonic conditions, and the ultrasonic time is preferably 5 minutes. This invention does not impose any special limitations on the ultrasonic conditions; conditions well-known to those skilled in the art can be used. After the dilute nitric acid treatment, this invention further preferably includes rinsing with deionized water and ultrasonic cleaning with deionized water sequentially. This invention does not impose any special limitations on the rinsing process; a process well-known to those skilled in the art can be used. The ultrasonic cleaning time is preferably 1-5 minutes. In this invention, the anhydrous ethanol treatment is preferably performed under ultrasonic conditions, and the ultrasonic time is preferably 5 minutes. This invention does not impose any special limitations on the ultrasonic conditions; conditions well-known to those skilled in the art can be used. After the anhydrous ethanol treatment, this invention further preferably includes rinsing with deionized water sequentially and ultrasonic cleaning with deionized water. This invention does not impose any special limitations on the rinsing process; a process well-known to those skilled in the art can be used. The ultrasonic cleaning time is preferably 1-5 minutes. After the ultrasonic cleaning with deionized water, this invention further preferably includes drying. The drying method is preferably wiping clean with low-dust wiping paper or a clean soft cloth, air drying naturally, or drying in an oven at 60-80°C.

[0037] In this invention, the solvent of the ruthenium chloride precursor solution preferably includes glycerol and dilute hydrochloric acid, and the concentration of the dilute hydrochloric acid is preferably 0.01 mol / L; the volume ratio of glycerol to dilute hydrochloric acid is preferably (1-3):1, more preferably (1-2):1, and most preferably (1-1.5):1; the solute in the ruthenium chloride precursor solution is preferably hydrated ruthenium chloride; the preparation of the ruthenium chloride precursor solution is preferably by mixing hydrated ruthenium chloride and the solvent; the concentration of ruthenium chloride in the ruthenium chloride precursor solution is preferably 0.01 mol / L; the mixing method is preferably ultrasonic mixing; the ultrasonic time is preferably 30 min; this invention does not impose any special limitations on the ultrasonic conditions, and conditions well known to those skilled in the art can be used.

[0038] In this invention, the drying is preferably performed using a hot air gun; the temperature of the hot air gun is preferably 300-350°C, more preferably 320-350°C, and most preferably 340-350°C; the number of times the dipping and drying are repeated is preferably 20-100 times.

[0039] In this invention, the molar ratio of lithium carbonate to sodium peroxide in the mixed powder of lithium carbonate and sodium peroxide is preferably (9-5):(1-5), more preferably (9-7):(1-3), and most preferably 9:1; the mixed powder of lithium carbonate and sodium peroxide is preferably prepared by mixing lithium carbonate and sodium peroxide; this invention does not impose any special limitations on the mixing process of lithium carbonate and sodium peroxide, and any process well known to those skilled in the art can be used.

[0040] In this invention, the lithium carbonate and sodium peroxide mixed powder is preferably placed in an alumina crucible or a gold crucible, the mixed powder is compacted, one end of a metal wire dipped in ruthenium chloride precursor solution and dried is inserted into the compacted mixed powder, the lid of the alumina crucible or gold crucible is covered, and heat treatment is performed.

[0041] In this invention, the heat treatment temperature is preferably 400-480°C, more preferably 400-450°C; the holding time is preferably 5 hours; the time to heat up to the heat treatment temperature is preferably 3 hours; after the heat treatment is completed, it is preferably cooled to room temperature over 3 hours.

[0042] In this invention, the cleaning process preferably includes cleaning the surface of the metal wire with one end coated with a ruthenium oxide film using a 3 mol / L dilute nitric acid solution to remove crystals, rinsing thoroughly with deionized water, then scraping the non-ruthenium oxide film area of ​​the metal wire with one end coated with a knife, polishing with 1200-grit sandpaper, and finally rinsing thoroughly with deionized water. In this invention, removing the crystals from the surface of the metal wire with one end coated with a ruthenium oxide film facilitates the removal of the metal wire.

[0043] After the cleaning is completed, the present invention preferably includes soaking in dilute nitric acid with a concentration of 1 mol / L for 24 hours, while ensuring that the ruthenium oxide film is completely immersed in dilute nitric acid for acidification treatment and removal of residual impurities.

[0044] After the soaking is completed, the present invention preferably includes rinsing with deionized water, wiping with low-dust wiping paper or a clean soft cloth, air drying naturally or drying in an oven at 60-80°C.

[0045] In this invention, the process of wrapping with polytetrafluoroethylene heat shrink tubing is preferably to wrap the non-ruthenium oxide film area in the metal wire with polytetrafluoroethylene heat shrink tubing, and to shrink the heat shrink tubing with a hot air gun at 300-350°C to achieve complete and tight wrapping.

[0046] In this invention, the pH value of the aging solution used for aging is preferably 4, the aging time is preferably 1 to 14 days, more preferably 4 to 14 days, and most preferably 7 to 14 days. In this invention, the aging process preferably involves immersing the obtained electrode in a buffer solution with a pH value of 4; the buffer solution is preferably a potassium hydrogen phthalate buffer solution.

[0047] This invention also provides a ruthenium oxide electrode prepared by the preparation method described above, comprising a metal wire, a ruthenium oxide film covering one end of the metal wire, and a polytetrafluoroethylene heat shrink tubing (e.g., ruthenium oxide film) covering the non-ruthenium oxide film region of the metal wire. Figure 1 (As shown).

[0048] The present invention also provides the application of the ruthenium oxide electrode described in the above technical solution in measuring the pH of water. The present invention does not impose any special limitations on the method of the application, and any process known to those skilled in the art can be used.

[0049] The following detailed description of the ruthenium oxide electrode, its preparation method, and its application provided by the present invention, with reference to specific embodiments, should not be construed as limiting the scope of protection of the present invention.

[0050] Example 1

[0051] A high-purity titanium wire with a diameter of 0.5 mm and a length of 7 cm was selected. One end of the high-purity titanium wire, 1.5 cm long, was cleaned with deionized water. The wire was then polished sequentially with 1200-grit, 5000-grit, and 7000-grit sandpaper, 20 times each. After each polishing, the wire was ultrasonically cleaned with deionized water for 1 minute. The wire was then polished sequentially with 1 μm, 0.3 μm, and 0.05 μm alumina powder, 20 times each. After each polishing, the wire was ultrasonically cleaned with deionized water for 1 minute. The high-purity titanium wire was then ultrasonically cleaned in 0.01 mol / L dilute nitric acid for 5 minutes. After removal, the wire was rinsed with deionized water and ultrasonically cleaned with deionized water for 1 minute. The high-purity titanium wire was then ultrasonically cleaned in anhydrous ethanol for 5 minutes. After removal, the wire was rinsed with deionized water and ultrasonically cleaned with deionized water for 1 minute. Finally, the wire was wiped clean with low-dust wiping paper to obtain the pretreated high-purity titanium wire.

[0052] Glycerol and 0.01 mol / L dilute hydrochloric acid were mixed evenly at a volume ratio of 1:1. Hydrated ruthenium chloride was then added to the mixed solution to prepare a 0.01 mol / L solution. The mixture was sonicated for 30 min to obtain a ruthenium chloride precursor solution. The pretreated end of the high-purity titanium wire was dipped into the ruthenium chloride precursor solution and dried using a hot air gun at 350°C. This process of dipping and drying was repeated 100 times.

[0053] Lithium carbonate (0.09 mol) and sodium peroxide (0.01 mol) were mixed evenly in a molar ratio of 9:1 and placed in an alumina crucible (10 mL capacity, 3 cm diameter, and 2.7 cm depth). The resulting mixed powder was compacted. The dip end of the high-purity titanium wire was inserted obliquely into the compacted mixed powder along the edge of the alumina crucible, ensuring that the front 1.5 cm of the high-purity titanium wire was completely immersed in the mixed powder. The lid of the alumina crucible was then placed in a muffle furnace for heat treatment. The temperature was raised from room temperature to 400°C for 3 hours, held for 5 hours, and then cooled to room temperature for 3 hours to obtain a high-purity titanium wire coated with a ruthenium oxide film.

[0054] The heat-treated lithium carbonate and sodium peroxide mixture was dissolved in 3 mol / L dilute nitric acid to facilitate the removal of the high-purity titanium wire. The wire was then cleaned with deionized water. The high-purity titanium wire portion outside the ruthenium oxide film was scraped with a knife, then polished with 1200-grit sandpaper, and finally cleaned with deionized water. The wire was then immersed in 1 mol / L dilute nitric acid for 24 hours to ensure that the ruthenium oxide film was completely immersed in the dilute nitric acid for acidification and removal of residual impurities.

[0055] After the acidification treatment is completed, the high-purity titanium wire is cleaned with deionized water and wiped clean with low-dust wiping paper; polytetrafluoroethylene heat shrink tubing is wrapped around the non-ruthenium oxide film area of ​​the high-purity titanium wire, and the polytetrafluoroethylene heat shrink tubing is shrunk to a completely tight wrap using a hot air gun at 350°C.

[0056] Finally, the electrode was placed in a commercially available potassium hydrogen phthalate buffer solution with a pH of 4 to ensure that the ruthenium oxide film was completely immersed in the solution. The electrode was aged for 14 days at room temperature to obtain the ruthenium oxide electrode.

[0057] Figure 2 Here is a SEM image of the ruthenium oxide thin film of the ruthenium oxide electrode, from... Figure 2 It can be seen that the ruthenium oxide film in the ruthenium oxide electrode is dense.

[0058] Figure 3 The diagram shows the potential response of the ruthenium oxide electrode in buffer solutions at pH 4, 7, and 10. Figure 4 The graphs show the linear fit of the ruthenium oxide electrode in buffer solutions at pH 4, 7, and 10, where the reference electrode is a commercially available saturated silver / silver chloride reference electrode. Figures 3-4 It can be seen that the ruthenium oxide electrode has good sensitivity and stability when testing pH, good Nernst response, and a goodness of fit of 0.999.

[0059] Figure 5 The results of seawater measurements using the ruthenium oxide electrode at Huimin Bridge Wharf in Zhoushan City, Zhejiang Province, are shown. The reference electrode is a commercially available saturated silver / silver chloride reference electrode, with a stable voltage of E = 151.5 mV. Figure 4 The obtained E-pH relationship is: E = -59.017pH + 621.35mV, which gives a pH value of 7.97; the pH value measured by the Hach pH measuring instrument (HQ4300, PHC101) is 7.91; the accuracy of the ruthenium oxide electrode in measuring seawater is approximately 99.2%.

[0060] Example 2

[0061] A high-purity titanium wire with a diameter of 0.5 mm and a length of 7 cm was selected. One end of the high-purity titanium wire, 1.5 cm long, was cleaned with deionized water. The wire was then polished sequentially with 1200-grit, 5000-grit, and 7000-grit sandpaper, 20 times each. After each polishing, the wire was ultrasonically cleaned with deionized water for 1 minute. The wire was then polished sequentially with 1 μm, 0.3 μm, and 0.05 μm alumina powder, 20 times each. After each polishing, the wire was ultrasonically cleaned with deionized water for 1 minute. The high-purity titanium wire was then ultrasonically cleaned in 0.01 mol / L dilute nitric acid for 5 minutes. After removal, the wire was rinsed with deionized water and ultrasonically cleaned with deionized water for 1 minute. The high-purity titanium wire was then ultrasonically cleaned in anhydrous ethanol for 5 minutes. After removal, the wire was rinsed with deionized water and ultrasonically cleaned with deionized water for 1 minute. Finally, the wire was wiped clean with low-dust wiping paper to obtain the pretreated high-purity titanium wire.

[0062] Glycerol and 0.01 mol / L dilute hydrochloric acid were mixed evenly at a volume ratio of 1:1. Hydrated ruthenium chloride was then added to the mixed solution to prepare a 0.01 mol / L solution. The mixture was sonicated for 30 min to obtain a ruthenium chloride precursor solution. The pretreated end of the high-purity titanium wire was dipped into the ruthenium chloride precursor solution and dried using a hot air gun at 350°C. This process of dipping and drying was repeated 100 times.

[0063] Lithium carbonate (0.09 mol) and sodium peroxide (0.01 mol) were mixed evenly in a molar ratio of 9:1 and placed in an alumina crucible (10 mL capacity, 3 cm diameter, and 2.7 cm depth). The resulting mixed powder was compacted. The dip end of the high-purity titanium wire was inserted obliquely into the compacted mixed powder along the edge of the alumina crucible, ensuring that the front 1.5 cm of the high-purity titanium wire was completely immersed in the mixed powder. The lid of the alumina crucible was then placed in a muffle furnace for heat treatment. The temperature was raised from room temperature to 480°C for 3 hours, held for 5 hours, and then cooled to room temperature for 3 hours to obtain a high-purity titanium wire coated with a ruthenium oxide film.

[0064] The heat-treated lithium carbonate and sodium peroxide mixture was dissolved in 3 mol / L dilute nitric acid to facilitate the removal of the high-purity titanium wire. The wire was then cleaned with deionized water. The high-purity titanium wire portion outside the ruthenium oxide film was scraped with a knife, then polished with 1200-grit sandpaper, and finally cleaned with deionized water. The wire was then immersed in 1 mol / L dilute nitric acid for 24 hours to ensure that the ruthenium oxide film was completely immersed in the dilute nitric acid for acidification and removal of residual impurities.

[0065] After the acidification treatment is completed, the high-purity titanium wire is cleaned with deionized water and wiped clean with low-dust wiping paper; polytetrafluoroethylene heat shrink tubing is wrapped around the non-ruthenium oxide film area of ​​the high-purity titanium wire, and the polytetrafluoroethylene heat shrink tubing is shrunk to a completely tight wrap using a hot air gun at 350°C.

[0066] Finally, the electrode was placed in a commercially available potassium hydrogen phthalate buffer solution with a pH of 4 to ensure that the ruthenium oxide film was completely immersed in the solution. The electrode was aged for 14 days at room temperature to obtain the ruthenium oxide electrode.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a ruthenium oxide electrode, characterized in that, Includes the following steps: One end of a metal wire is dipped in a ruthenium chloride precursor solution and dried. Then it is inserted into a mixed powder of lithium carbonate and sodium peroxide and subjected to heat treatment to obtain a metal wire with a ruthenium oxide film coated on one end. The ruthenium oxide film in the metal wire with one end covered by a ruthenium oxide film is cleaned with dilute nitric acid. Then, polytetrafluoroethylene heat shrink tubing is wrapped around the non-ruthenium oxide film area in the metal wire with one end covered by a ruthenium oxide film, and the material is aged to obtain the ruthenium oxide electrode.

2. The preparation method according to claim 1, characterized in that, The metal wire is titanium wire, gold wire, silver wire or copper wire.

3. The preparation method according to claim 1, characterized in that, When one end of the metal wire is dipped into the ruthenium chloride precursor solution, the length of the dipped end of the metal wire is 1 to 1.5 cm. The drying process is performed using a hot air gun; the temperature of the hot air gun is 300–350°C. The dipping and drying process is repeated 20 to 100 times.

4. The preparation method according to any one of claims 1 to 3, characterized in that, Before the metal wire is dipped into the ruthenium chloride precursor solution, the process also includes pretreatment of the metal wire. The pretreatment includes grinding, polishing, and ultrasonic treatment performed sequentially.

5. The preparation method according to claim 1, characterized in that, The solvent of the ruthenium chloride precursor solution includes glycerol and dilute hydrochloric acid, wherein the concentration of the dilute hydrochloric acid is 0.01 mol / L; The volume ratio of glycerol to dilute hydrochloric acid is (1-3):1; The concentration of ruthenium chloride in the ruthenium chloride precursor solution is 0.01 mol / L.

6. The preparation method according to claim 1, characterized in that, The molar ratio of lithium carbonate to sodium peroxide in the mixed powder of lithium carbonate and sodium peroxide is (9-5):(1-5).

7. The preparation method according to claim 1, characterized in that, The heat treatment temperature is 400-480℃, and the holding time is 5h.

8. The preparation method according to claim 1, characterized in that, The aging solution used in the aging process has a pH of 4, the aging temperature is room temperature, and the aging time is 1 to 14 days.

9. The ruthenium oxide electrode prepared by the method according to any one of claims 1 to 8, characterized in that, It includes a metal wire, a ruthenium oxide film covering one end of the metal wire, and a polytetrafluoroethylene heat shrink tubing covering the non-ruthenium oxide film area of ​​the metal wire.

10. The application of the ruthenium oxide electrode as described in claim 9 in measuring the pH of water.

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