Method for observing single nanobubble in-situ by electrochemistry based on liquid chip and TEM observation

Abstract

The application relates to a kind of liquid chip-based electrochemical in-situ TEM single-nanobubble observation methods. Atomic layer deposition and focused ion beam technology are used to process liquid chip to form single nanometer reaction zone;The processed liquid chip is connected with electrochemical workstation through the transmission electron microscope operating rod of built-in wire and liquid microchannel, and under the driving of external voltage, the controllable generation of single nanobubble is realized;The dynamic evolution process of single nanobubble is observed in real time by transmission electron microscope imaging technology. The application combines electrochemical method and transmission electron microscope technology, which can not only obtain key data in the process of electrochemical reaction in real time, but also intuitively capture the dynamic evolution process of nanobubble, and provides a new method for in-depth study of the microcosmic change of interface in electrochemical reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemical in-situ technology and nanobubble observation, and particularly relates to a method for observing single nanobubble based on a liquid chip and TEM in-situ. BACKGROUND

[0002] In the field of electrochemical research, bubble generation phenomenon is common, including hydrogen production by electrolysis of water, carbon dioxide reduction, electrolysis of aluminum, and chlor-alkali industry and other important processes. In these processes, the bubbles generated on the electrode surface not only reduce the effective active area of the electrocatalyst, but also change the conduction path of the ions in the electrolyte, thereby reducing the reaction efficiency. Therefore, it is of great significance to study the formation of bubbles on the electrode surface and its effect on the reaction efficiency in the electrochemical process. The formation of nanobubbles is a necessary stage in the evolution process of bubbles, which reveals the micro characteristics of the three-phase interface. Therefore, in-depth study of the formation of nanobubbles helps to understand the micro mechanism of bubble evolution behavior, and also provides a theoretical basis for the design of electrode surface structure.

[0003] At present, the imaging research of nanobubbles mainly relies on atomic force microscopy, interference reflection microscopy, single molecule total internal reflection fluorescence microscopy, surface plasmon resonance microscopy and electron microscopy technology. However, the spatial resolution of optical microscopy method is limited, atomic force microscope is easy to disturb the surface morphology of nanobubble, and electron microscope is difficult to control the random generation of nanobubble. Therefore, it is very important to develop an in-situ observation method for nanobubbles. Existing research shows that by adjusting the size of the reaction electrode, single nanobubble can be generated controllably, but it is difficult to obtain its image information. Transmission electron microscopy has nanoscale resolution, but it cannot accurately control the generation of single bubble. The present application innovatively constructs a nanoscale reaction area on a TEM liquid chip (Liquivision-TEM, hereinafter referred to as liquid chip), and realizes the controllable generation and real-time in-situ observation of single nanobubble by combining with an electrochemical workstation, so as to directly capture the evolution dynamics. SUMMARY

[0004] The purpose of the present application is to provide an in-situ observation method for electrochemical single nanobubble, which can accurately control the reaction area to nanoscale level by using atomic layer deposition and focused ion beam technology, so as to ensure the generation of single nanobubble. By adjusting the applied potential, the generation process of nanobubble is controlled, and at the same time, the formation and evolution behavior of nanobubble are observed in real time by using in-situ TEM (transmission electron microscope).

[0005] The present application provides an in-situ observation method for electrochemical single nanobubble, which comprises the following steps:

[0006] An insulating layer is deposited on the electrodes (including working electrodes and counter electrodes) of the liquid chip by atomic layer deposition technology, and the electrodes after the deposition of the insulating layer are micro-nano processed by focused ion beam technology to form a nano reaction zone on the working electrode.

[0007] The liquid chip is assembled into a transmission electron microscope operating rod, the operating rod is provided with a lead wire and a liquid microchannel, an electrochemical workstation is connected, a micro-injection pump is used to inject an electrolyte into the chip, and the electrolyte is immersed in the electrodes of the chip.

[0008] The type and potential of the electrolyte are changed, and in-situ imaging observation of a single nanobubble is realized by using a TEM.

[0009] In the method, the material forming the insulating layer is one or more of aluminum oxide, hafnium oxide, silicon nitride and silicon oxide, and further, the thickness of the insulating layer is 20-50 nm.

[0010] In the method, the micro-nano processing includes etching and depositing a metal layer on the working electrode, and etching the counter electrode, the purpose of etching is to remove part of the insulating layer on the surface of the working electrode and part of the insulating layer on the surface of the counter electrode, the part of the working electrode surface where the insulating layer is removed is covered by the deposited metal layer to form the nano reaction zone, and the metal layer and the working electrode are in contact to form an electrical connection.

[0011] Further, the etching is performed by using an etching ion beam, the etching ion beam is one of helium, neon and gallium ion beams, and the material forming the deposited metal layer is one of platinum and tungsten.

[0012] Further, in order to avoid the influence of the shielding of the electron beam on the imaging of the nanobubble, side etching and deposition are performed on the working electrode to form the nano reaction zone, and the area of the nano reaction zone is 5*10 -15 m 2 - 7*10 -13 m 2 , and the counter electrode is etched to form a micron reaction zone.

[0013] In the method, the voltage for generating the nanobubble is -10 V-10 V.

[0014] In the method, the reactant in the electrolyte is hydrogen peroxide, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, [C n mim][BF4], [C n mim][PF6], [C n mim][NO3] and [C nThe electrolyte contains one or more of the following: [mim][SO4] aqueous solution, wherein n = 4-10, and the supporting electrolyte in the electrolyte (the supporting electrolyte is an electrolyte used to improve the conductivity of the electrolyte, and the supporting electrolyte itself does not participate in the electrochemical reaction) is one or more of potassium chloride and sodium chloride.

[0015] Furthermore, the electrolyte concentration is 0 mM - 1000 mM, and the supporting electrolyte concentration is 10 mM - 50 mM.

[0016] In the method of the present invention, the energy of the electron beam observed by the in-situ TEM is 100kV-300kV.

[0017] Compared with the prior art, the present invention can bring the following beneficial effects:

[0018] By controlling the electrocatalytic reaction within a single nanometer region and observing the dynamic evolution of nanobubbles, interference from other reaction regions can be avoided, thus improving the precision of bubble behavior control at the nanoscale. By observing the formation and evolution of nanobubbles in situ under TEM, the key factors affecting the microscopic evolution of the interface during electrocatalysis can be revealed. This patented method can provide theoretical guidance for bubble regulation and optimization of electrocatalytic performance. Attached Figure Description

[0019] Figure 1(a) is a schematic diagram of the device used for in-situ TEM observation of nanobubbles; Figure 1(b) is an enlarged view of the internal electrodes of the liquid chip shown in Figure 1(a).

[0020] Figure 2 This is a schematic diagram of the fabrication of the working electrode of the in-situ TEM electrochemical liquid chip cell in Example 2.

[0021] Figure 3 These are the nanobubbles observed under in-situ TEM in Examples 1-8, wherein... Figure 3 (1) The nanobubbles observed under in-situ TEM in Example 1. Figure 3 (2) The nanobubbles observed under in-situ TEM in Example 2. Figure 3 (3) The nanobubbles observed under in-situ TEM in Example 3. Figure 3 (4) The nanobubbles observed under in-situ TEM in Example 4. Figure 3 (5) The nanobubbles observed under in-situ TEM in Example 5. Figure 3 (6) Nanobubbles observed under in-situ TEM in Example 6. Figure 3 (7) Nanobubbles observed under in-situ TEM in Example 7. Figure 3 (8) Nanobubbles observed in situ under TEM in Example 8. Detailed Implementation

[0022] In order to more clearly illustrate the method and technology of the present disclosure, the technical solutions of the present application will be described clearly and completely below in conjunction with the embodiments and drawings. The described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the present application.

[0023] The embodiments of the present application all use the device shown in FIG. 1 (a) and FIG. 1 (b) to in-situ observe the electrochemical single nanobubble, and the device mainly comprises an electrochemical workstation 1, a wire 2, a transmission electron microscope operating rod 3, an in-situ electron microscope (not shown in FIG. 1), a working electrode 5 and a deposited metal layer 6. The working electrode 5 and the deposited metal layer 6 are both located inside the transmission electron microscope operating rod 3, and a gas bubble 7 will be generated on the surface of the working electrode 5 during electrolysis. The use method of the device is as follows: the electrochemical workstation 1 is used to provide an external voltage, and the electrical signal is transmitted to the electrode in the transmission electron microscope operating rod 3 through the wire 2; then the electron beam 4 generated by the in-situ electron microscope passes through the sample and interacts with the atoms in the sample, and the generated signal is received and processed by the detection system of the in-situ electron microscope, and finally the structural information of the sample is displayed on the screen.

[0024] Embodiment 1: Imaging of single hydrogen nanobubbles generated by electrolysis of 500 mM H2O2 aqueous solution in a 400 nm reaction zone

[0025] Firstly, an aluminum oxide insulating layer with a thickness of 20 nm is deposited on the substrate of a microfluidic chip by using atomic layer deposition technology. Subsequently, a gallium ion focused ion beam system is used to etch a working electrode area of the microfluidic chip to form a nanometer reaction zone with an exposed area of 5*10 -14 m 2 , and a micrometer reaction zone is etched in the counter electrode area. Then, tungsten is selectively deposited in the etched area using the tungsten ion source to fill the nanometer reaction area and ensure the flatness of the surface. Finally, the microfluidic chip is assembled and connected with an electrochemical test system. A mixed solution containing 500 mM H2O2 as electrolyte and 50 mM potassium chloride as supporting electrolyte is injected into the microchannel of the microfluidic chip by using a precision syringe pump. Under the condition of applying a constant voltage of 5 V, in-situ observation is carried out by using a transmission electron microscope with an acceleration voltage of 100 kV, and the nanobubbles generated in the anode area are observed as shown in Figure 3 (1).

[0026] Embodiment 2: Imaging of single hydrogen nanobubbles generated by electrolysis of 500 mM H2SO4 aqueous solution in a 500 nm reaction zone

[0027] First, a 50 nm thick aluminum oxide insulating layer was deposited on the microfluidic chip substrate using atomic layer deposition technology. Subsequently, a nanometer reaction zone with a diameter of about 500 nm was etched in the working electrode region of the microfluidic chip using a gallium ion focused ion beam system. The exposed area of the nanometer reaction zone formed after deposition was 7 x 10 -13 m 2 A micrometer reaction zone was etched in the counter electrode region. Then, tungsten was selectively deposited in the etched region using the tungsten ion source to fill the nanometer reaction zone and ensure the surface flatness. Finally, the finished microfluidic chip was assembled and connected to an electrochemical test system. A mixed solution containing 500 mM H2SO4 as the electrolyte and 50 mM potassium chloride as the supporting electrolyte was injected into the microchannel of the microfluidic chip by a precision syringe pump. In situ observation was performed using a transmission electron microscope with an acceleration voltage of 100 kV under the condition of applying a constant voltage of -5 V. The nanobubbles generated in the cathode region were observed as shown in Figure 3 (2).

[0028] Example 3: Imaging of single hydrogen nanobubbles generated by electrolysis of 1000 mM HCl aqueous solution in a 50 nm reaction zone

[0029] First, a 50 nm thick aluminum oxide insulating layer was deposited on the microfluidic chip substrate using atomic layer deposition technology. Subsequently, a nanometer reaction zone with a diameter of about 50 nm was etched in the working electrode region of the microfluidic chip using a gallium ion focused ion beam system. The exposed area of the nanometer reaction zone formed after deposition was 5 x 10 -15 m 2 A micrometer reaction zone was etched in the counter electrode region. Then, platinum was selectively deposited in the etched region using the platinum ion source to fill the nanometer reaction zone and ensure the surface flatness. Finally, the finished microfluidic chip was assembled and connected to an electrochemical test system. A mixed solution containing 1000 mM HCl as the electrolyte and 50 mM potassium chloride as the supporting electrolyte was injected into the microchannel of the microfluidic chip by a precision syringe pump. In situ observation was performed using a transmission electron microscope with an acceleration voltage of 300 kV under the condition of applying a constant voltage of -4 V. The nanobubbles generated in the cathode region were observed as shown in Figure 3 (3).

[0030] Example 4: Imaging of single hydrogen nanobubbles generated by electrolysis of 10 mM [Bmim][BF4] aqueous solution in a 300 nm reaction zone

[0031] First, a 30 nm thick aluminum oxide insulating layer was deposited on the microfluidic chip substrate using atomic layer deposition technology. Subsequently, a 300 nm diameter nanoreaction zone was etched on the working electrode region of the microfluidic chip using a gallium ion focused ion beam system. The exposed area of the nanoreaction zone formed after deposition was 2 x 10 -13 m 2 A micrometer reaction zone was etched in the counter electrode region. Then, platinum was selectively deposited in the etched region using the platinum ion source to fill the nanoreaction zone and ensure the surface flatness. Finally, the finished microfluidic chip was assembled and connected to an electrochemical test system. A 10 mM [Bmim] [BF4] solution was injected into the microchannel of the microfluidic chip as the electrolyte by a precision syringe pump. In situ observation was performed using a transmission electron microscope with an acceleration voltage of 100 kV under the condition of applying a constant voltage of -5 V. The nanobubbles generated in the cathode region were observed as shown in Figure 3 (4).

[0032] Example 5: Imaging of single hydrogen nanobubbles generated by electrolysis of a 10 mM [Emim] [BF4] aqueous solution in a 250 nm reaction zone

[0033] First, a 50 nm thick aluminum oxide insulating layer was deposited on the microfluidic chip substrate using atomic layer deposition technology. Subsequently, a 250 nm diameter nanoreaction zone was etched on the working electrode region of the microfluidic chip using a helium ion focused ion beam system. The exposed area of the nanoreaction zone formed after deposition was 1.8 x 10 -13 m 2 A micrometer reaction zone was etched in the counter electrode region. Then, platinum was selectively deposited in the etched region using the platinum ion source to fill the nanoreaction zone and ensure the surface flatness. Finally, the finished microfluidic chip was assembled and connected to an electrochemical test system. A 10 mM [Emim] [BF4] solution was injected into the microchannel of the microfluidic chip as the electrolyte by a precision syringe pump. In situ observation was performed using a transmission electron microscope with an acceleration voltage of 300 kV under the condition of applying a constant voltage of -6 V. The nanobubbles generated in the cathode region were observed as shown in Figure 3 (5).

[0034] Example 6: Imaging of single hydrogen nanobubbles generated by electrolysis of a 10 mM [C 10 mim] [BF4] aqueous solution in a 300 nm reaction zone

[0035] First, a 50 nm thick aluminum oxide insulating layer was deposited on the microfluidic chip substrate using atomic layer deposition technology. Subsequently, a gallium ion focused ion beam system was used to etch a 300 nm diameter nanoreaction zone in the working electrode region of the microfluidic chip. The exposed area of the nanoreaction zone formed after deposition was 2 x 10 -13 m 2 A micrometer reaction zone was etched in the counter electrode region. Then, platinum was selectively deposited in the etched region using the platinum ion source to fill the nanoreaction zone and ensure its surface flatness. Finally, the finished microfluidic chip was assembled and connected to an electrochemical test system. A 10 mM [C 10 mim][BF4] aqueous solution was injected into the microchannel of the microfluidic chip using a precision syringe pump as the electrolyte. In situ observation was performed using a transmission electron microscope with an acceleration voltage of 300 kV under the condition of applying a constant voltage of -2 V. The nanobubbles generated in the cathode region were observed as shown in Figure 3 (6).

[0036] Example 7: Imaging of single hydrogen nanobubbles generated by electrolysis of a 10 mM [Bmim][PF6] aqueous solution in a 400 nm reaction zone

[0037] First, a 50 nm thick hafnium oxide insulating layer was deposited on the microfluidic chip substrate using atomic layer deposition technology. Subsequently, a gallium ion focused ion beam system was used to etch a 400 nm diameter nanoreaction zone in the working electrode region of the microfluidic chip. The exposed area of the nanoreaction zone formed after deposition was 5 x 10 -14 m 2 A micrometer reaction zone was etched in the counter electrode region. Then, platinum was selectively deposited in the etched region using the platinum ion source to fill the nanoreaction zone and ensure its surface flatness. Finally, the finished microfluidic chip was assembled and connected to an electrochemical test system. A 10 mM [Bmim][PF6] aqueous solution was injected into the microchannel of the microfluidic chip using a precision syringe pump as the electrolyte. In situ observation was performed using a transmission electron microscope with an acceleration voltage of 300 kV under the condition of applying a constant voltage of -2 V. The nanobubbles generated in the cathode region were observed as shown in Figure 3 (7).

[0038] Example 8: Imaging of single hydrogen nanobubbles generated by electrolysis of a 10 mM [Bmim][NO3] aqueous solution in a 300 nm reaction zone

[0039] First, a hafnium oxide insulating layer with a thickness of 50 nm was deposited on the microfluidic chip substrate by atomic layer deposition. Subsequently, a gallium ion focused ion beam system was used to etch a working electrode area of the microfluidic chip to a diameter of about 300 nm, and the exposed area of the nano-reaction region formed after deposition was 2×10 -13 m 2 , and a micrometer reaction region was etched in the counter electrode area. Then, platinum was selectively deposited in the etched area using the platinum ion source to fill the nano-reaction region and ensure the surface flatness. Finally, the finished microfluidic chip was assembled and connected to an electrochemical test system. A precision syringe pump was used to inject 10 mM [Bmim][NO3] as the electrolyte into the microchannel of the microfluidic chip. In situ observation was performed using a transmission electron microscope with an acceleration voltage of 100 kV under the condition of applying a constant voltage of -2 V, and the nanobubbles generated in the cathode region were observed as shown in Figure 3 (8).

[0040] Comparative Example 1:

[0041] This comparative example has the same electrolyte and reaction conditions as Example 2. A 50 nm aluminum oxide insulating layer was deposited on the chip reactor, and tungsten was selectively deposited in the etched area using a tungsten ion source, and the electrolyte composition was 500 mM H2SO4 and 50 mM KCl supporting electrolyte, and in situ observation was performed under the condition of applying a constant voltage of -5 V.

[0042] The diameter of the etched reaction area of the working electrode was changed to 10 nm, and the exposed area of the nano-reaction region formed after deposition was 3×10 -16 m 2 , and no single nanobubble was observed under the same conditions.

[0043] The diameter of the etched reaction area of the working electrode was changed to 600 nm, and the exposed area of the nano-reaction region formed after deposition was 1×10 -12 m 2 , and no single nanobubble was observed under the same conditions.

[0044] The diameter of the etched reaction area of the working electrode was changed to 1000 nm, and the exposed area of the nano-reaction region formed after deposition was 3×10 -12 m 2 , and no single nanobubble was observed under the same conditions.

[0045] Comparative Example 2:

[0046] This comparative example uses the same reaction region diameter as Example 4. A microfluidic chip working electrode area was etched to a diameter of about 300 nm, and the exposed area of the nano-reaction region formed after deposition was 2×10-13 m 2 In-situ observation was carried out using a 100 kV transmission electron microscope (TEM) under a constant voltage of -5 V in a 10 mM [Bmim][BF4] electrolyte.

[0047] When the chip substrate is deposited with a 10 nm thick aluminum oxide insulating layer, other conditions remain unchanged, due to the low thickness of the insulating layer, after focused ion beam etching and deposition, a continuous nanoreaction zone cannot be formed, and single nanobubble generation is not observed;

[0048] When the chip substrate is deposited with a 60 nm thick aluminum oxide insulating layer, other conditions remain unchanged, due to the high thickness of the insulating layer, after focused ion beam etching and deposition, the nanoreaction zone is blocked by the insulating layer, and single nanobubble generation is not observed.

[0049] The in-situ TEM electrochemical liquid chip cell for nanobubble observation and the preparation method thereof provided by the embodiment of the application couple electrochemical methods and transmission electron microscopy, real-time monitor the dynamic evolution process of nanobubbles, and make up for the shortcomings of the prior art; in addition, the preparation method of the electrochemical liquid chip cell provided by the embodiment of the application controls the electrochemical reaction at a single nanometer point, and the performance and dynamic evolution process of the material can be accurately identified and analyzed under the in-situ electron microscope, thereby providing a powerful means for the development of new materials in the fields of energy conversion, storage technology, biomedicine and environmental protection.

[0050] Finally, the method of the present application is only a preferred embodiment, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for in-situ electrochemical TEM observation of single nanobubbles based on liquid chips, characterized in that, The method includes the following steps: An insulating layer is deposited on the working electrode and counter electrode of the liquid chip. The material forming the insulating layer is one or more of aluminum oxide, hafnium oxide, silicon nitride, and silicon oxide, and the thickness of the insulating layer is 20 nm-50 nm. The working electrode is etched to remove part of the insulating layer, and then a metal layer is deposited in the etched area to form a nano-reaction region with an area of ​​5 × 10⁻⁶. -15 m 2 - 7×10 -13 m 2 The working electrode is formed by side etching and deposition of a metal layer to form a reaction region with a diameter of 50 nm to 500 nm, and the counter electrode is etched to remove part of the insulating layer to form a micron reaction region; The liquid chip is assembled into the transmission electron microscope (TEM) operating rod, which is connected to an electrochemical workstation. The TEM operating rod is provided with a liquid microchannel, through which electrolyte is injected into the liquid chip until the working electrode and the counter electrode are completely submerged. The electrochemical workstation applies a voltage to excite the generation of a single nanobubble in the nanoreaction region of the working electrode, which is observed in real time using a transmission electron microscope.

2. The method according to claim 1, characterized in that, The etching is performed using an ion beam, which is one or more of helium, neon, and gallium ion beams.

3. The method according to claim 1, characterized in that, The voltage required to generate a single nanobubble is -10 V to 10 V.

4. The method according to claim 1, characterized in that, The electrolyte is one or more of the following aqueous solutions: hydrogen peroxide, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, [Cnmim][BF4], [Cnmim][PF6], [Cnmim][NO3], and [Cnmim][HSO4], wherein n = 4-10 and the concentration is 0 mM-1000 mM; the supporting electrolyte in the electrolyte is one or more of the following: potassium chloride and sodium chloride, with a concentration of 10 mM-50 mM.

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