Preparation method and application of optical fiber-noble metal double-probe ultramicroelectrode

Abstract

This invention discloses a method for fabricating an optical fiber-noble metal dual-probe ultramicroelectrode and its application. The fabrication method includes: drawing a capillary to obtain a first capillary that is hourglass-shaped and symmetrical in the middle; placing a noble metal wire and an optical fiber in the middle of the first capillary; then continuing to draw the first capillary along the middle until the noble metal wire and the optical fiber are fixed to the middle of the first capillary and then breaking it in the middle to obtain a second capillary; injecting a conductive medium into the second capillary; inserting a base metal wire into the second capillary through the opening of the second capillary to contact the conductive medium; sealing the opening with a sealant to obtain a third capillary; detecting whether the third capillary is conductive; and polishing the conductive third capillary to obtain the optical fiber-noble metal dual-probe ultramicroelectrode. This invention is suitable for studying photoelectrocatalytic reactions in extremely small spaces, possessing high spatial resolution and product detection efficiency, and can also avoid the photocorrosion behavior of catalysts caused by large-scale illumination.

Description

Technical Field

[0001] This invention relates to the field of scanning probe fabrication technology, and in particular to a method for fabricating an optical fiber-noble metal dual-probe ultramicroelectrode and its application. Background Technology

[0002] Scanning electrochemical microscopy (SECM) is an electrochemical analytical scanning probe technique with high spatial resolution, widely used to study the surface properties of substrate electrodes and local charge transfer processes. Furthermore, combining ultramicroelectrodes in SECM with optical fibers for localized illumination and scanning of the substrate electrode allows for the study of photoelectrocatalytic reactions, enabling rapid and efficient catalyst screening while avoiding photocorrosion caused by large-scale illumination. SECM resolution is a critical technical indicator, primarily depending on the size, surface shape, and spacing between the substrate and the ultramicroelectrode. The ability to fabricate small, flat ultramicroelectrodes is key to improving SECM resolution. To more effectively approximate the substrate and prevent contact between the ultramicroelectrode tip encapsulation layer and the substrate, the ultramicroelectrode needs to have an extremely fine tip.

[0003] Currently, various combinations of optical fibers and microelectrodes have been reported in the literature. However, these combinations all have their own limitations. For example, when the incident light is perpendicular to the reaction system and irradiates the entire substrate, the microelectrodes will form shadows and disrupt the uniformity of illumination. When the incident light is irradiated on the back of the substrate, it will cause the photogenerated carriers to recombine during long-distance migration, reducing the carrier transfer efficiency. When the incident light is irradiated at an acute angle, it will lead to the injection of carrier aggregation. When a noble metal layer is sputtered on an optical fiber as a microelectrode, the metal layer is easy to peel off, which affects the lifetime of the electrode.

[0004] Therefore, it is necessary to provide a method for fabricating fiber-noble metal dual-probe ultramicroelectrodes. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for fabricating an optical fiber-noble metal dual-probe ultramicroelectrode, the method comprising:

[0006] The capillary tube is drawn to obtain a first capillary tube that is symmetrical and has an hourglass shape in the middle;

[0007] The precious metal wire and the optical fiber are placed in the middle of the first capillary. Then the first capillary is pulled along the middle until the precious metal wire and the optical fiber are fixed in the middle of the first capillary and then broken in the middle to obtain the second capillary.

[0008] A conductive medium is injected into the second capillary, and a base metal wire is inserted from the opening of the second capillary into contact with the conductive medium. The opening is then sealed with a sealant to obtain a third capillary.

[0009] The continuity of the third capillary is detected, and the continuity of the third capillary is polished to obtain the fiber-noble metal dual probe microelectrode.

[0010] Furthermore, the detection of whether the third capillary is conductive includes,

[0011] Use steady-state voltammetry to detect whether the third capillary is conductive;

[0012] If the third capillary is conducting, the electrode size is calculated based on the limiting diffusion current of the oxidation / reduction reaction.

[0013] Furthermore, the conductive medium includes conductive silver paste.

[0014] Furthermore, the sealant includes epoxy resin.

[0015] Furthermore, the capillary includes a borosilicate glass capillary.

[0016] Furthermore, the precious metal wire includes platinum wire or gold wire.

[0017] Furthermore, the base metal wire includes tin-plated copper wire.

[0018] Furthermore, the precious metal wire is cleaned, the cleaning process including...

[0019] The precious metal wire was immersed in Piranha cleaning solution and then ultrasonically washed with ethanol and ultrapure water in sequence.

[0020] The present invention also provides an optical fiber-noble metal dual-probe ultramicroelectrode, which is prepared according to the above-described preparation method.

[0021] This invention also provides applications of the fiber-noble metal dual-probe ultramicroelectrode prepared by the above-described method, the applications including,

[0022] A detection system was constructed using scanning electrochemical microscopy, with an optical fiber-noble metal dual-probe ultramicroelectrode as the first working electrode and a catalyst-supported substrate electrode as the second working electrode.

[0023] Ultraviolet or visible light is introduced into the first working electrode via an optical fiber and irradiated onto the catalyst surface on the second working electrode, inducing a photoelectrocatalytic reaction in the second working electrode.

[0024] The types of products of the photoelectrocatalytic reaction of the second working electrode were analyzed based on the oxidation peak of the first working electrode.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] In the optical fiber-noble metal dual-probe ultramicroelectrode of this invention, during scanning electrochemical microscopy testing, the optical fiber can introduce ultraviolet or visible light emitted from the light source into the semiconductor catalyst loaded on the substrate electrode (under bias) for localized irradiation, inducing photoelectrocatalytic reactions. Simultaneously, the biased ultramicroelectrode can detect electrochemically active products through electrochemical oxidation reactions and identify product types in situ based on oxidation peak potentials. This dual-probe ultramicroelectrode is suitable for studying photoelectrocatalytic reactions in extremely small spaces, possessing high spatial resolution and product detection efficiency, while avoiding photocorrosion of the semiconductor catalyst caused by large-scale illumination.

[0027] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the steps or apparatus pointed out in the description and the drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart of a method for fabricating an optical fiber-noble metal dual-probe ultramicroelectrode according to the present invention is shown;

[0030] Figure 2 The diagram illustrates the present invention using platinum wire and optical fiber as raw materials, and drawing them using a drawing instrument.

[0031] Figure 3 The flowchart of the present invention, which uses platinum wire and optical fiber as raw materials and performs drawing using a drawing instrument, is shown.

[0032] Figure 4a The original capillary diagram of the present invention is shown. Figure 4b A detailed capillary diagram of the present invention is shown. Figure 4c The diagram shows the sealed optical fiber and platinum wire of the present invention. Figure 4d The diagram shows the sealed optical fiber and gold wire of the present invention;

[0033] Figure 5a The electrode terminals of the fiber-noble metal dual-probe ultramicroelectrode are shown. Figure 5b The electrode surface of the fiber-noble metal dual-probe ultramicroelectrode is shown. Figure 5cA schematic diagram of the structure of the fiber-noble metal dual-probe ultramicroelectrode is shown;

[0034] Figure 6 The steady-state voltammetric curve of the third capillary in Embodiment 1 of the present invention is shown;

[0035] Figure 7 The steady-state voltammetric curve of the third capillary in Embodiment 2 of the present invention is shown;

[0036] Figure 8 A schematic diagram of the application of the fiber-noble metal dual-probe ultramicroelectrode in catalyst product analysis in Example 3 is shown;

[0037] Figure 9a This shows a SECM imaging image of the oxidation current of the reduction product collected by the fiber-optic-noble metal dual-probe ultramicroelectrode in Example 3. Figure 9b This shows a SECM imaging image of the photoelectrocatalytic reduction current at the substrate electrode catalyst site collected in Example 3. Figure 9c The cyclic voltammogram of the substrate electrode product detected by the fiber-optic-noble metal dual-probe ultramicroelectrode in Example 3 is shown. Detailed Implementation

[0038] The design concept of this invention includes using a laser drawing instrument to encapsulate optical fibers and noble metal wires in parallel within a capillary to prepare an optical fiber-noble metal dual-probe ultramicroelectrode. Based on a traditional four-electrode testing system, photo-induced photoelectrocatalytic reactions are induced by introducing light onto a substrate electrode (under bias). Simultaneously, after biasing the ultramicroelectrode, electrochemically active substances can be detected through oxidation reactions, and the products of the photoelectrocatalytic reaction can be identified and analyzed in situ through a specific potential.

[0039] like Figure 1 As shown, this invention provides a method for fabricating an optical fiber-noble metal dual-probe ultramicroelectrode, the method comprising the following steps:

[0040] S101. The capillary is drawn to obtain a first capillary that is symmetrical in the middle and has an hourglass shape.

[0041] Specifically, place the capillary tube in the V-groove of the drawing instrument, aligning its center with the condenser lens assembly, and secure the capillary tube using the knobs on both sides of the instrument. Heat the capillary tube for 18-25 seconds to its softening point, at which point the program-set pulling force parameter is 0, until an hourglass shape forms in the center of the capillary. Then move the capillary tube 1-1.5 mm to the right, adjusting the program parameters (heating temperature, filament, speed, or delay) and repeating the drawing process. The heating time is 10-14 seconds. To prevent the glass tube from breaking, do not apply lateral pulling force. This adjustment controls the size and shape of the drawn section.

[0042] Specifically, the capillary includes a borosilicate glass capillary.

[0043] S102. Place the precious metal wire and the optical fiber in the middle of the first capillary, and then continue to pull the first capillary along the middle until the precious metal wire and the optical fiber are fixed to the middle of the first capillary and then broken in the middle to obtain the second capillary.

[0044] Specifically, a certain length of precious metal wire and optical fiber (with stripped protective layer) are placed in the thinning section inside a first capillary tube that is symmetrically shaped like an hourglass. The first capillary tube, also symmetrically shaped like an hourglass, is placed and fixed in the V-groove of the drawing device. Simultaneously, two O-rings are used to secure the drawing device to prevent further thinning and breakage of the capillary tube due to weak tension. The program parameters are set for heating and drawing for 13-17 seconds. The capillary tube is then moved 0.5-0.8 mm to the right, and the drawing operation is repeated. This process seals and fixes the metal wire and optical fiber inside the capillary tube.

[0045] In this invention, the length of the noble metal wire is less than the length of the first capillary, and the noble metal wire and the optical fiber are arranged parallel and symmetrically inside the first capillary.

[0046] Specifically, the precious metal wire includes platinum wire or gold wire. In this invention, the precious metal wire undergoes cleaning, which includes...

[0047] The precious metal wire was immersed in piranha cleaning solution, followed by ultrasonic washing with ethanol and ultrapure water in sequence. The piranha cleaning solution was prepared by mixing H2SO4 and H2O2 in a volume ratio of 3:1. After immersion for 5-20 minutes, the surface of the precious metal wire was rinsed with ultrapure water to remove any remaining piranha cleaning solution. The ultrasonic washing time with ethanol and ultrapure water was 3-8 minutes.

[0048] Figure 2 A schematic diagram is shown showing the drawing process using platinum wire and optical fiber as raw materials and a drawing instrument.

[0049] S103. Inject a conductive medium into the second capillary, connect a base metal wire from the opening of the second capillary to the conductive medium, and seal the opening with a sealant to obtain a third capillary.

[0050] Specifically, the conductive medium includes conductive silver paste, the base metal wire includes tin-plated copper wire, and the sealant includes epoxy resin. Sealing the opening with epoxy resin is to prevent solution from entering during subsequent testing and causing a short circuit in the microelectrode.

[0051] like Figure 3 As shown, steps S101-S103 are divided into five steps.

[0052] Step 1: Draw the capillary tube to obtain the first capillary tube, which is symmetrical and has an hourglass shape in the middle;

[0053] Step 2: Place the precious metal wire and optical fiber parallel and symmetrically inside the first capillary tube;

[0054] Step 3: Continue to pull the first capillary in an hourglass shape along its middle to fix the precious metal wire and optical fiber to the first capillary.

[0055] Step 4: Break the capillary tube obtained in step 3 in the middle to obtain the second capillary tube;

[0056] Step 5: Inject conductive silver paste into the second capillary. Connect a copper wire from the opening of the second capillary to the conductive silver paste, with one end of the copper wire in contact with the conductive silver paste and the other end extending out of the opening of the second capillary. Seal the opening of the second capillary with epoxy resin to obtain the third capillary.

[0057] Figure 4a -d shows an image of a capillary being drawn. Figure 4a The original capillary was shown. Figure 4b The thinned capillary is shown. Figure 4c The sealed optical fiber and platinum wire are shown; Figure 4d The sealed optical fiber and gold wire are shown.

[0058] S104. Detect whether the third capillary is conductive, and polish the conductive third capillary to obtain the fiber-noble metal dual probe microelectrode.

[0059] Specifically, steady-state voltammetry is used to detect whether the third capillary is conductive;

[0060] If the third capillary is conducting, the electrode size is calculated based on the limiting diffusion current of the oxidation / reduction reaction.

[0061] Specifically, steady-state voltammetry was used to detect the conductivity of the third capillary. The detection standard was that the steady-state voltammetry curve of the third capillary exhibited a typical "S" shape at a low scan rate, indicating that the third capillary was conductive. In addition, the steady-state voltammetry curve of the third capillary showed a small double-layer charge-discharge current, indicating that the prepared third capillary had good conductivity. The size of the microelectrode could also be calculated based on the limiting diffusion current of the oxidation / reduction reaction.

[0062] The electrode of the conductive third capillary was polished with coarse sandpaper; then, it was polished with metallographic sandpaper and Al2O3 polishing powder of 0.3μm and 0.05μm in sequence until the surface of the noble metal wire was observed to be bright under a microscope; the polished end of the conductive third capillary was suspended downward in a beaker and sonicated twice for 5 minutes each time to wash away the residual Al2O3 polishing powder, and finally the fiber-noble metal dual probe ultra-micro electrode was obtained.

[0063] Figure 5aImages of the electrode ends of the fiber-noble metal dual-probe microelectrode are shown, revealing that the platinum wire and optical fiber are fixed inside the capillary. Figure 5b An image of the electrode surface of the fiber-noble metal dual-probe microelectrode is shown, which shows that the platinum wire and the fiber have bright surfaces. The fiber has a diameter of 50 μm and the platinum wire has a diameter of 25 μm. Figure 5c A schematic diagram of the fiber-optic-noble metal dual-probe microelectrode is shown. The fiber-optic-noble metal dual-probe microelectrode consists of two ends: one end is the conductor end, which is a tin-plated copper wire (abbreviated as Cu wire in the diagram). One side of the tin-plated copper wire contacts the conductive silver paste inside the capillary, while the other side extends out of the capillary opening, where the tin-plated copper wire is sealed with epoxy resin; the other end is the electrode end, which includes an optical fiber and a platinum wire fixed after the capillary has been refined. In this schematic diagram, each part represents only the structure and position and is not proportional to actual dimensions.

[0064] The present invention also provides an optical fiber-noble metal dual-probe ultramicroelectrode, which is prepared according to the above-described preparation method.

[0065] This invention also provides applications of the fiber-noble metal dual-probe ultramicroelectrode prepared by the above-described method, the applications including,

[0066] A detection system was constructed using scanning electrochemical microscopy, with an optical fiber-noble metal dual-probe ultramicroelectrode as the first working electrode and a catalyst-supported substrate electrode as the second working electrode.

[0067] Ultraviolet or visible light is introduced into the first working electrode via an optical fiber and irradiated onto the catalyst surface on the second working electrode, inducing a photoelectrocatalytic reaction in the second working electrode.

[0068] The types of products of the photoelectrocatalytic reaction of the second working electrode were analyzed based on the oxidation peak of the first working electrode.

[0069] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] Example 1

[0071] A method for fabricating an optical fiber-noble metal dual-probe ultramicroelectrode includes the following steps:

[0072] 1. Cleaning of precious metal wires: Soak platinum wires in freshly prepared piranha cleaning solution (volume ratio: H2SO4:H2O2 = 3:1) for 15 minutes, then rinse the surface of the platinum wires with ultrapure water to remove any remaining piranha cleaning solution, and then ultrasonically clean them with ethanol and ultrapure water in sequence, each time for 5 minutes, to obtain the cleaned platinum wires.

[0073] 2. Capillary Refinement: Place the borosilicate glass capillary in the V-groove of the drawing instrument, aligning its center with the condenser lens assembly, and fix the capillary with the knobs on both sides; set the program parameters of the straightening instrument to heat the center of the borosilicate glass capillary for 20 seconds to soften it, at which point the tension parameter set in the program is 0, until an hourglass shape is formed in the center; then move the borosilicate glass capillary 1.2 mm to the right, adjust the program parameters, and repeat the drawing steps, with the heating time being 12 seconds, to obtain the first capillary that is symmetrical and has an hourglass shape in the center.

[0074] 3. Electrode End Sealing: A certain length of precious metal wire and optical fiber (with stripped protective layer) are placed in the narrowed section inside the first capillary, which is symmetrically shaped like an hourglass. The first capillary, symmetrically shaped like an hourglass, is placed and fixed in the V-groove of the drawing device. Simultaneously, two O-rings are used to secure the drawing device to prevent further thinning and breakage of the first capillary due to weak pulling force. The program parameters are set for heating and drawing for 15 seconds. Then, the glass tube is moved 0.5 mm to the right, and the drawing operation is repeated. This seals and fixes the metal wire and optical fiber inside the first capillary. The first capillary is then broken in the middle to obtain the second capillary; the break point is the electrode end.

[0075] In this embodiment, the drawing device is a Sutter P-2000 laser drawing device. In step 2, the parameters of the drawing device are set as follows: HEAT = 380, FILAMENT = 4, VELOCITY = 15, DELAY = 120, PULL = 0. In step 3, the parameters of the drawing device are set as follows: HEAT = 500, FILAMENT = 4, VELOCITY = 30, DELAY = 0, PULL = 0.

[0076] 4. Sealing the wire end: Inject conductive silver paste into the second capillary, and connect a tin-plated copper wire from the opening of the second capillary to contact the conductive silver paste. One end of the tin-plated copper wire is in contact with the conductive silver paste, and the other end extends out of the opening of the second capillary. Seal the opening of the second capillary with epoxy resin to obtain the third capillary.

[0077] 5. Continuity Detection: A three-electrode detection system was constructed using the third capillary: the working electrode was the third capillary, the reference electrode was a silver / silver chloride electrode, and the counter electrode was a platinum wire with a diameter of 0.5 mm. The electrode of the third capillary was immersed in a methanol mixture of 1 mM ferrocene and 0.05 M KCl. Steady-state voltammetry was performed at a potential of 0.05-0.5 V and a scan rate of 5 mV / s. The steady-state voltammetry curve of the third capillary showed a typical "S" shape, indicating that the third capillary was conducting.

[0078] like Figure 6 As shown, the third capillary obtained in step 5 exhibits a typical "S" shape, indicating that it is conductive, and the electrode size can be calculated based on the limiting diffusion current of the oxidation / reduction reaction.

[0079] 6. Grinding and polishing: Grind the electrode of the conductive third capillary with coarse sandpaper, and then polish it with metallographic sandpaper and 0.3μm and 0.05μm Al2O3 polishing powder in sequence until the surface of the noble metal wire is bright when observed under a microscope; suspend the polished end of the conductive third capillary downward in a beaker and sonicate it twice, 5 minutes each time to wash away the residual Al2O3 polishing powder, and finally obtain the fiber-platinum dual probe ultra-micro electrode.

[0080] Example 2

[0081] The preparation method of an optical fiber-noble metal dual-probe ultramicroelectrode is basically the same as that in Example 1, except that the noble metal wire is gold wire, the potential in the continuity detection step is 0-0.45V, and the parameters of the pulling instrument in step 3 are HEAT (temperature) = 350, FILAMENT (filament) = 4, VELOCITY (speed) = 15, DELAY (delay) = 0, PULL (tension) = 0.

[0082] like Figure 7 As shown, the third capillary in this embodiment exhibits a typical "S" shape, indicating that it is conductive, and the electrode size can be calculated based on the limiting diffusion current of the oxidation / reduction reaction.

[0083] Example 3

[0084] An application of a fiber-optic-noble metal dual-probe ultramicroelectrode includes the following steps.

[0085] 1. Using scanning electrochemical microscopy, a typical four-electrode system was constructed. The fiber-noble metal dual-probe ultramicroelectrode of Example 1 was used as the working electrode 1, the substrate electrode loaded with catalyst was used as the working electrode 2, the counter electrode was a platinum wire with a diameter of 0.5 mm, and the reference electrode was a silver / silver chloride electrode.

[0086] 2. Immerse the working electrode 2 in a CO2-saturated 0.1M KHCO3 solution, and suspend the working electrode 1 20-100μm above the working electrode 2. Scan the working electrode 1 along the XY plane while using an optical fiber to introduce ultraviolet or visible light to irradiate the catalyst material on the working electrode 1. Apply a bias voltage to the working electrode 2. At this time, the working electrode 2 undergoes a photoelectrocatalytic reaction, in which the electrochemically active products diffuse through the CO2-saturated 0.1M KHCO3 solution to the surface of the working electrode 1.

[0087] 3. Based on the oxidation peak potential in the cyclic voltammetry curve of working electrode 1, the types of products of the photoelectrocatalytic reaction carried out by working electrode 2 can be determined.

[0088] For example, Figure 8 A schematic diagram of the application of the fiber-optic-noble metal dual-probe ultramicroelectrode of Example 1 in the analysis of catalytic reaction products is shown. In the diagram, hv represents light, Ox represents oxidation reaction, and Red represents reduction reaction. Ultraviolet light provided by a xenon lamp is irradiated onto the catalyst at the working electrode 2 via an optical fiber, initiating a photoelectrocatalytic reaction. The generated products diffuse onto the surface of the fiber-optic-noble metal dual-probe ultramicroelectrode. Cyclic voltammetry curves are scanned using the ultramicroelectrode. Electrochemically active products are oxidized at specific potentials, exhibiting characteristic peaks on the cyclic voltammetry curves. The types of products can be identified in situ based on these characteristic peaks.

[0089] Figure 9a The diagram shows the SECM imaging of the oxidation current of the reduction products generated by the base electrode in this embodiment diffused onto the surface of the fiber-noble metal dual-probe microelectrode. The potential applied to the microelectrode is 0.4V. The darker the color of the two crescent-shaped parts in the figure, the greater the oxidation current of the reduction products. Figure 9b The figure shows the photoelectrocatalytic reduction current of the catalyst point on the substrate electrode in this embodiment. The potential applied to the substrate electrode is 0V. The part outside the two circles in the figure is the background current of the substrate electrode. The darker the color of the two circles, the greater the photoelectrocatalytic reduction current of the catalyst point. Figure 9c The cyclic voltammogram of the fiber-noble metal dual-probe microelectrode in this embodiment is shown at a potential range of -0.8 to 1.2 V relative to the silver / silver chloride electrode and a scan rate of 1 V / s. The product can be determined to be CO based on the oxidation peak potential.

[0090] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating an optical fiber-noble metal dual-probe ultramicroelectrode, characterized in that, The preparation method includes, The capillary tube is drawn to obtain a first capillary tube that is symmetrical and has an hourglass shape in the middle; The precious metal wire and the optical fiber are placed in the middle of the first capillary. Then the first capillary is pulled along the middle until the precious metal wire and the optical fiber are fixed in the middle of the first capillary and then broken in the middle to obtain the second capillary. A conductive medium is injected into the second capillary, and a base metal wire is inserted from the opening of the second capillary into contact with the conductive medium. The opening is then sealed with a sealant to obtain a third capillary. The continuity of the third capillary is detected, and the continuity of the third capillary is polished to obtain the fiber-noble metal dual probe microelectrode.

2. The preparation method according to claim 1, characterized in that, The detection of whether the third capillary is conductive includes, Use steady-state voltammetry to detect whether the third capillary is conductive; If the third capillary is conducting, the electrode size is calculated based on the limiting diffusion current of the oxidation / reduction reaction.

3. The preparation method according to claim 1, characterized in that, The conductive medium includes conductive silver paste.

4. The preparation method according to claim 1, characterized in that, The sealant includes epoxy resin.

5. The preparation method according to claim 1, characterized in that, The capillary includes a borosilicate glass capillary.

6. The preparation method according to claim 1, characterized in that, The precious metal wire includes platinum wire or gold wire.

7. The preparation method according to claim 1, characterized in that, The base metal wire includes tin-plated copper wire.

8. The preparation method according to any one of claims 1-7, characterized in that, The precious metal wire is cleaned, and the cleaning process includes... The precious metal wire was immersed in Piranha cleaning solution and then ultrasonically washed with ethanol and ultrapure water in sequence.

9. A fiber-optic-noble metal dual-probe ultramicroelectrode, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

10. An application of the fiber-noble metal dual-probe ultramicroelectrode prepared by the method according to any one of claims 1-8, characterized in that, The applications include, A detection system was constructed using scanning electrochemical microscopy, with an optical fiber-noble metal dual-probe ultramicroelectrode as the first working electrode and a catalyst-supported substrate electrode as the second working electrode. Ultraviolet or visible light is introduced into the first working electrode via an optical fiber and irradiated onto the catalyst surface on the second working electrode, inducing a photoelectrocatalytic reaction in the second working electrode. The types of products of the photoelectrocatalytic reaction of the second working electrode were analyzed based on the oxidation peak of the first working electrode.

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