Membrane electrode surface hydrophilicity and hydrophobicity in-situ detection method

Abstract

The invention discloses a membrane electrode surface hydrophilicity and hydrophobicity in-situ detection method, which comprises the following steps: keeping an electrolyte in a flowing state in an electrolytic tank which comprises a horizontally arranged membrane electrode and a to-be-detected electrode surface of the membrane electrode at the lower part, shooting bubbles generated on the to-be-detected electrode surface by using a camera, controlling the current density and the electrolyte flow velocity, and calculating the hydrophilicity and hydrophobicity of the membrane electrode surface. When the bubbles reach a stable state, the contact angle of the bubbles in the stable state is analyzed through a contact angle measuring instrument; an electrolyte is kept in a non-flowing state in an electrolytic tank, the electrolytic tank comprises a horizontally-arranged membrane electrode, the surface of the to-be-measured electrode of the membrane electrode is located on the upper portion, the low current density is controlled, bubbles are generated on the surface of the to-be-measured electrode, and a metal ring of a surface tension meter slowly moves towards the bubbles and makes contact with the bubbles; upwards and slowly pulling the metal ring to separate the bubbles, testing a critical point of separation of the bubbles and the to-be-tested electrode, and recording the adhesive force of the to-be-tested electrode to the bubbles at the moment. According to the invention, the in-situ test of the hydrophilic-hydrophobic property of the electrode is realized.

Description

Technical Field

[0001] This invention relates to the field of membrane electrode performance analysis, and more specifically, to a method for in-situ detection of hydrophilicity and hydrophobicity on the surface of a membrane electrode. Background Technology

[0002] In electrochemical reactions involving water molecules, the hydrophilicity or hydrophobicity of electrodes significantly impacts energy conversion efficiency, primarily affecting gas-liquid mass transfer efficiency and electrochemical active area. This influence is amplified at high current densities. Therefore, obtaining information on electrode hydrophilicity or hydrophobicity is crucial for the design and development of high-performance electrodes. Voltage and electrolyte significantly influence electrode surface functional groups; however, current hydrophilicity / hydrophobicity testing methods are all performed under non-in-situ conditions, failing to reveal the true changes in electrode surface properties.

[0003] CN 113916726 A discloses a method for testing the contact angle of hydrophilic porous membranes. By analyzing the structure-property relationship between the contact angle and parameters such as air permeability, inlet pressure, surface tension, and roughness ratio of the hydrophilic membrane, linear fitting is performed based on the Young-Laplace equation to obtain hydrophilicity indicators such as the apparent equilibrium contact angle and intrinsic contact angle. However, the above method is only applicable to tests under non-in-situ conditions and does not consider the influence of voltage and electrolyte on the hydrophilicity / hydrophobicity of the electrode. It cannot complete tests during electrochemical reactions and has limited help in analyzing the hydrophilicity / hydrophobicity of the electrode surface under reaction conditions. Therefore, there is a need to develop an in-situ testing method, which would have significant guiding significance for the design of electrodes with high hydrophilicity, high hydrophobicity, or specific hydrophilicity indicators. Summary of the Invention

[0004] To address the aforementioned deficiencies in the prior art, this invention provides an in-situ detection method for the hydrophilicity and hydrophobicity of a membrane electrode surface. This method can test the bubble contact angle and bubble adhesion force on the electrode surface in situ, thereby achieving in-situ testing of the electrode's hydrophilicity and hydrophobicity.

[0005] To achieve the above-mentioned objectives, this invention provides an in-situ method for detecting the hydrophilicity / hydrophobicity of a membrane electrode surface, comprising the following steps:

[0006] 1) In an electrolytic cell, the electrolyte is kept in a flowing state. The electrolytic cell contains a horizontally placed membrane electrode with the surface of the electrode to be tested located below. A camera is used to capture the bubbles generated on the surface of the electrode to be tested. The current density and electrolyte flow rate are controlled. When the bubbles reach a stable state, the contact angle of the bubbles in the stable state is analyzed by a contact angle measuring instrument.

[0007] 2) In the electrolytic cell, the electrolyte is kept in a non-flowing state. The electrolytic cell contains a horizontally placed membrane electrode with the surface of the electrode to be tested on the upper side. A low current density is controlled, and bubbles are generated on the surface of the electrode to be tested. The metal ring of the surface tension meter moves slowly toward the bubble and comes into contact with it. The metal ring is slowly pulled upward to separate the bubble. The critical point at which the bubble separates from the electrode to be tested is tested, and the adhesion force of the electrode to the bubble at this time is recorded.

[0008] 3) The hydrophilicity or hydrophobicity of the electrode under test is evaluated by the bubble contact angle measured in step 1) and the bubble adhesion force measured in step 2).

[0009] Furthermore, in step 1), at least one side of the electrolytic cell is equipped with a transparent shell for a camera on one side of the electrolytic cell to capture bubbles on the surface of the electrode under test.

[0010] Furthermore, in step 1), the top plate of the electrolytic cell is made of acrylic glass, and the materials of other side plates are selected according to the characteristics of the electrochemical reaction. For example, for alkaline water electrolysis to produce hydrogen, nickel-plated stainless steel can be selected, and for proton exchange membrane water electrolysis to produce hydrogen, titanium can be selected.

[0011] Further, in step 1), the contact angle of the bubble in a steady state is analyzed using a contact angle measuring instrument. The analysis method includes: using an optical imaging method with a current density set to 0.1 mA / cm². 2 The contact angle measuring instrument was placed on the side of the electrolytic cell, 10 cm away from the cell, and the contact angle of the bubbles on the electrode surface was measured after the reaction had proceeded for 0.5, 1, 2, 3, 4, 5, 6, 8 and 10 hours respectively. The test ended when the contact angle no longer changed during the test.

[0012] Furthermore, in step 1), the current density is controlled to achieve an observable current density control range of 0.1–0.5 mA / cm² for a single bubble. 2 .

[0013] Furthermore, in step 1), the electrolyte flow rate is controlled to ensure that bubble desorption is not affected by the electrolyte, and the electrolyte flow rate range is 2 to 10 L / min.

[0014] Furthermore, in step 2), the upper part of the electrolytic cell has an open structure, and the electrolyte above the electrode to be tested is in direct contact with the air through the opening.

[0015] Furthermore, in step 2), a low current density is controlled to prevent the active sites that generate bubbles from continuously producing bubbles, thus avoiding automatic bubble desorption. The current density range is 0.1–0.5 mA / cm². 2 .

[0016] Furthermore, in step 2), the metal ring slowly moves towards the bubble through the opening at a speed of 0.01–0.05 mm / s. -1 Preferably, it is 0.02 mm s -1 .

[0017] Further, in step 3), the evaluation method includes: the smaller the contact angle of the bubble, the better the hydrophobicity (or anaerobicity) of the electrode; conversely, the better the hydrophilicity (or anaerobicity) of the electrode. The larger the adhesion force value of the bubble, the better the hydrophobicity (or anaerobicity) of the electrode; conversely, the better the hydrophilicity (or anaerobicity) of the electrode.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] This invention provides an in-situ detection method for the hydrophilicity / hydrophobicity of membrane electrode surfaces, comprising two approaches: bubble contact angle testing and bubble adhesion force testing. The contact angle testing method is based on optical imaging. In an electrolytic cell, the electrolyte is kept in a continuous flow state. A camera captures images of bubbles along the cross-section of the electrode surface. By controlling the reaction current density and electrolyte flow rate, the dynamic changes in the bubble contact angle under the two-electrode system can be observed, and bubbles in a stable state can be obtained. The contact angle of the bubbles in the stable state is then analyzed using a contact angle meter. This invention utilizes a surface tension meter to test the bubble adhesion force on the surface of the electrode under test in an electrolytic cell. Keeping the electrolyte in a non-flowing state in the electrolytic cell avoids the influence of electrolyte flow on the bubble adhesion force test. The electrolyte is in direct contact with air above, and a low current density is controlled to prevent the active sites that generate bubbles from continuously producing bubbles, thus avoiding automatic bubble desorption.

[0020] Conventional methods for testing the hydrophilicity and hydrophobicity of electrodes can only be performed under non-reactive conditions. However, the hydrophilicity and hydrophobicity of the electrode surface can change under the influence of voltage and electrolyte. This invention can test the bubble contact angle and bubble adhesion force on the electrode surface in situ in the electrolytic cell reaction environment. The bubble contact angle and bubble adhesion force are two methods for testing the hydrophilicity and hydrophobicity of electrodes. Combining the two methods can accurately analyze the change law of electrode hydrophilicity and hydrophobicity with voltage during the reaction process.

[0021] In summary, the method of this invention improves upon conventional non-in-situ testing methods, achieving in-situ testing of electrode hydrophilicity and hydrophobicity while maintaining testing accuracy. Furthermore, this invention can monitor the changes in hydrophilicity and hydrophobicity on the electrode surface in real time, and grasp key information such as the coverage of oxyphilic species on the electrode surface, providing insights for the design of electrodes with specific hydrophilicity and hydrophobicity properties.

[0022] Other features and advantages of the present invention will be described in detail through the following specific embodiments. Attached Figure Description

[0023] Figure 1A schematic diagram of the in-situ test model for bubble contact angle provided in this embodiment of the invention.

[0024] Figure 2 A schematic diagram of the in-situ test model for bubble adhesion force provided in this embodiment of the invention. Detailed Implementation

[0025] The following will clearly and completely describe the concept and technical effects of this application in conjunction with embodiments, so as to fully understand the purpose, features and effects of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application.

[0026] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] Conventional methods for testing the hydrophilicity and hydrophobicity of electrodes can only be performed under non-reactive conditions. However, the hydrophilicity and hydrophobicity of electrode surfaces change under the influence of voltage and electrolytes. Current techniques cannot achieve in-situ testing, thus failing to reveal the true changes in electrode surface properties. This often results in directionally designed electrode structures failing to achieve specific objectives. To address these issues, this invention develops an in-situ method for testing the hydrophilicity and hydrophobicity of electrodes. In-situ test data helps guide the design of catalyst active sites, allowing for the design of appropriate hydrophilic group coverage based on the reaction's hydrophilicity and hydrophobicity requirements. Currently available contact angle meters, surface tension meters, and electrochemical reaction cells cannot meet the in-situ testing conditions. Therefore, a complete testing method needs to be developed, including the design of an in-situ electrode hydrophilicity and hydrophobicity testing reaction cell, as well as improvements to the testing procedures for contact angle meters and surface tension meters. Furthermore, bubble contact angle and bubble adhesion force are two methods for testing electrode hydrophilicity and hydrophobicity. Contact angle is an apparent manifestation of adhesion force; using only the bubble contact angle cannot accurately obtain the electrode's hydrophilicity and hydrophobicity. Combining both methods is necessary to accurately analyze the changes in electrode hydrophilicity and hydrophobicity with voltage during the reaction process, providing insights for the design of electrodes with specific hydrophilicity and hydrophobicity.

[0028] Based on this, the present invention provides an in-situ detection method for hydrophilicity / hydrophobicity of membrane electrode surface, comprising the following steps:

[0029] 1) In an electrolytic cell, the electrolyte is kept in a flowing state. The electrolytic cell contains a horizontally placed membrane electrode with the surface of the electrode to be tested located below. A camera is used to capture the bubbles generated on the surface of the electrode to be tested. The current density and electrolyte flow rate are controlled. When the bubbles reach a stable state, the contact angle of the bubbles in the stable state is analyzed by a contact angle measuring instrument.

[0030] 2) In the electrolytic cell, the electrolyte is kept in a non-flowing state. The electrolytic cell contains a horizontally placed membrane electrode with the surface of the electrode to be tested on the upper side. A low current density is controlled, and bubbles are generated on the surface of the electrode to be tested. The metal ring of the surface tension meter moves slowly toward the bubble and comes into contact with it. The metal ring is slowly pulled upward to separate the bubble. The critical point at which the bubble separates from the electrode to be tested is tested, and the adhesion force of the electrode to the bubble at this time is recorded.

[0031] 3) The hydrophilicity or hydrophobicity of the electrode under test is evaluated by the bubble contact angle measured in step 1) and the bubble adhesion force measured in step 2).

[0032] In some embodiments, in step 1), at least one side of the electrolytic cell is made of a transparent shell (e.g., the shell on the side of the electrode to be tested is made of a transparent material) for a camera to capture bubbles on the surface of the electrode to be tested. The camera is set outside the electrolytic cell and captures images of one side of the electrolytic cell. A high-speed camera is preferred.

[0033] For example, the top plate of the electrolytic cell is made of acrylic glass, and the materials of other side plates are selected according to the characteristics of the electrochemical reaction. For example, for alkaline water electrolysis to produce hydrogen, nickel-plated stainless steel can be selected, and for proton exchange membrane water electrolysis to produce hydrogen, titanium can be selected.

[0034] In some embodiments, in step 1), the contact angle of the bubble in a steady state is analyzed using a contact angle measuring instrument. The analysis method includes: employing an optical imaging method with a current density set to 0.1 mA / cm². 2 The contact angle measuring instrument is placed on the side of the electrolytic cell, 10 cm away from the cell. The contact angle of the bubbles on the electrode surface is measured after the reaction has proceeded for 0.5, 1, 2, 3, 4, 5, 6, 8 and 10 hours respectively. If the contact angle no longer changes during the test, the test can be ended.

[0035] In this invention, the hydrophilicity or hydrophobicity of the electrode in the electrochemical reaction involving water molecules has a significant impact on the energy conversion efficiency, mainly including gas-liquid mass transfer efficiency and electrochemical active area. This effect is exacerbated at high current densities. On an electrode with poor hydrophilicity, when the current is too high, a large number of bubbles are generated but cannot detach from the electrode in time, and the electrolyte cannot completely wet the electrode, resulting in a significant reduction in the electrochemical active area, thereby reducing the energy conversion efficiency.

[0036] In some implementations, in step 1), the current density is controlled to achieve an observable current density control range of 0.1–0.5 mA / cm² for a single bubble. 2 .

[0037] In some implementations, in step 1), the electrolyte flow rate is controlled to ensure that bubble desorption is not affected by the electrolyte, and the electrolyte flow rate range is 2 to 10 L / min.

[0038] In some implementations, in step 2), the upper part of the electrolytic cell is an open structure, and the electrolyte above the electrode to be tested is in direct contact with the air through the opening. The purpose is to allow the bubble probe of the surface tension meter to enter the electrolytic cell and contact the bubbles on the electrode surface.

[0039] In some embodiments, in step 2), a low current density is controlled to prevent the active sites that generate bubbles from continuously producing bubbles, thus avoiding automatic bubble desorption. The current density range is 0.1–0.5 mA / cm². 2 .

[0040] In some embodiments, in step 2), the metal ring slowly moves through the opening toward the bubble at a speed of 0.01–0.05 mm / s. -1 The opening is preferably a round hole.

[0041] In some embodiments, step 3) includes the following evaluation method: a smaller contact angle of the bubble indicates better hydrophobicity (or aerophilicity) of the electrode; conversely, a larger contact angle indicates better hydrophilicity (or aerophobicity) of the electrode. A larger bubble adhesion force indicates better hydrophobicity (or aerophilicity) of the electrode, and vice versa.

[0042] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0043] Example 1

[0044] Figure 1This invention illustrates an in-situ bubble contact angle testing model. The top plate of the electrolytic cell is made of acrylic glass to maintain the electrolyte in a flowing state. The electrolytic cell contains a horizontally placed membrane electrode, with the surface of the electrode under test (SUT) located below and the counter electrode on the other side above. A high-speed camera is placed on one side outside the electrolytic cell to capture images of bubbles generated on the surface of the SUT and their dynamic changes. Individual bubbles are observable by controlling the current density, and bubble desorption is unaffected by the electrolyte flow rate, allowing the bubbles to reach a stable state. The contact angle of the bubbles in the stable state is analyzed using a contact angle measuring instrument. The in-situ bubble contact angle testing model is used to measure the hydrogen bubble contact angle of the hydrogen evolution reaction in alkaline water electrolysis. A membrane electrode prepared with Raney nickel, 10% Nafion solution, and Nafion 117 membrane is used as the sample, with 1 mol / L KOH solution as the electrolyte and a current density set to 0.1 mA / cm². 2 The contact angle measuring instrument was placed on the side of the electrolytic cell, 10 cm away from the cell. The bubble contact angle on the electrode surface was measured at 0.5, 1, 2, 3, 4, 5, 6 and 8 hours after the reaction began.

[0045] Figure 2 This invention illustrates an in-situ testing model for bubble adhesion. The electrolytic cell has an open structure at the top, allowing the electrolyte above the electrode under test to directly contact air through an opening (a circular hole with a diameter of 1 cm), maintaining the electrolyte in a non-flowing state. The electrolytic cell contains a horizontally placed membrane electrode, with the electrode under test surface at the top and the counter electrode at the bottom. Bubbles are generated on the surface of the electrode under test. A low current density is controlled to prevent the active sites from continuously generating bubbles, thus avoiding automatic bubble desorption. A metal ring from a surface tension meter is slowly moved towards the bubble through the open circular hole (at a speed of 0.02 mm / s). -1 The metal ring is then slowly pulled upwards to separate the bubble from the electrode, and the critical point of separation between the bubble and the electrode is tested. The adhesion force between the electrode and the bubble at this point is recorded using a surface tension meter; this is the interaction force between the bubble and the electrode when they are about to separate. An in-situ bubble adhesion force testing model was used to measure the hydrogen bubble adhesion force during the hydrogen evolution reaction of alkaline water electrolysis. A membrane electrode prepared with Raney nickel, Nafion solution, and a Nafion membrane was used as the sample. A 1 mol / L KOH solution was used as the electrolyte, and the current density was set to 0.1 mA / cm². 2 The bubble adhesion force on the electrode surface was measured at 0.5, 1, 2, 3, 4, 5, 6 and 8 hours after the reaction started.

[0046] The hydrophilicity / hydrophobicity of the electrode under test was evaluated by measuring the bubble contact angle and bubble adhesion force obtained through the above steps. In this embodiment, both the electrode under test and the counter electrode in the membrane electrode were Raney nickel-Nafion electrodes. The bubble contact angle and bubble adhesion force on the electrode surface were tested for the unreacted electrode and after 0.5, 1, 2, 3, 4, 5, 6, and 8 hours of reaction. The contact angles were 110.5° (unreacted), 110°, 111.3°, 115.3°, 124.5°, 130.5°, 135.7°, 138.5°, and 138.3°, respectively; the bubble adhesion forces were 65.5 μN (unreacted), 65.2 μN, 64.6 μN, 62.3 μN, 57.5 μN, 54.2 μN, 51.5 μN, 50.4 μN, and 50.5 μN, respectively. After reaching a steady state, the bubble contact angle and bubble adhesion force were 138.3° and 50.5 μN, respectively. The hydrophilicity / hydrophobicity evaluation results of the electrode under test are as follows: Based on the above data, it was found that as the electrochemical reaction proceeded, the hydrophilicity of the electrode continuously increased, while the hydrophobicity continuously decreased. After 6 hours of reaction, the contact angle of the electrode was 28° larger than that of the unreacted electrode, and the adhesion force of the electrode was 15 μN smaller than that of the unreacted electrode. This indicates that the contact angle measured by the non-in-situ model cannot reflect the true surface properties of the electrode, making the development of an in-situ contact angle testing method essential. After 6 hours of reaction, the hydrophilicity / hydrophobicity of the electrode no longer changed, indicating that the electrode reached a steady state.

[0047] Comparative Example 1

[0048] In-situ test model of bubble contact angle ( Figure 1 The contact angle of hydrogen bubbles during the hydrogen evolution reaction of alkaline water electrolysis was measured. A membrane electrode prepared with Raney nickel, Nafion solution, and a Nafion membrane was used as the sample. A 1 mol / L KOH solution was used as the electrolyte. No voltage was applied. The contact angle measuring instrument was placed on the side of the electrolytic cell, 10 cm away. The bubble contact angle on the electrode surface was measured at regular intervals. The test results are as follows: the bubble contact angles on the electrode surface at 0, 0.5, 1, 2, 3, 4, 5, 6, and 8 hours were 110.5°, 111.2°, 110°, 112°, 109.5°, 110.2°, 110.8°, and 111.5°, respectively.

[0049] In-situ test model of bubble adhesion force ( Figure 2The adhesion force of hydrogen bubbles during the hydrogen evolution reaction of alkaline water electrolysis was measured. A membrane electrode prepared with Raney nickel, Nafion solution, and a Nafion membrane was used as the sample. A 1 mol / L KOH solution was used as the electrolyte. No voltage was applied, and the bubble adhesion force on the electrode surface was measured at regular intervals. The test results are as follows: the bubble adhesion forces on the electrode surface at 0, 0.5, 1, 2, 3, 4, 5, 6, and 8 h were 65.5 uN, 65.8 uN, 65.0 uN, 64.7 uN, 64.5 uN, 64.8 uN, 65.6 uN, 65.4 uN, and 65.1 uN, respectively.

[0050] The hydrophilicity / hydrophobicity evaluation results of the tested electrode are as follows: Based on the above data, it was found that when only electrolyte is passed through and no voltage is applied, the bubble contact angle and bubble adhesion force on the electrode surface do not change over time. Hydrophilicity / hydrophobicity testing without applying potential falls under the category of in-situ testing and cannot reflect the surface properties of the electrode under actual reaction conditions. In Example 1 above, under the influence of voltage, the hydrophilicity of the Raney nickel-Nafion electrode for the hydrogen evolution reaction significantly increased, while its hydrophobicity significantly decreased. These test results demonstrate that in-situ testing methods help obtain more accurate electrode surface properties, allowing for the targeted design of more efficient electrode structures according to reaction requirements.

[0051] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for in-situ detection of hydrophilic and hydrophobic properties of a membrane electrode surface, characterized by, The method comprises the following steps: 1) In an electrolytic cell, keep the electrolyte in a flowing state, the electrolytic cell contains a horizontally placed membrane electrode, and the electrode surface to be measured of the membrane electrode is located below, use a camera to take pictures of the bubbles generated on the electrode surface to be measured, control the current density and the flow rate of the electrolyte, when the bubbles reach a stable state, analyze the contact angle of the bubbles in the stable state by a contact angle measuring instrument; 2) In an electrolytic cell, keep the electrolyte in a non-flowing state, the electrolytic cell contains a horizontally placed membrane electrode, and the electrode surface to be measured of the membrane electrode is located above, control a lower current density, bubbles are generated on the electrode surface to be measured, a metal ring of a surface tension instrument slowly moves towards the bubbles and contacts the bubbles, slowly pull the metal ring upwards to make the bubbles separate, test the critical point of the separation of the bubbles from the electrode to be measured, and record the adhesion of the bubbles to the electrode to be measured at this time; 3) Evaluate the hydrophobicity or hydrophilicity of the electrode to be measured by the contact angle of the bubbles measured in step 1) and the adhesion of the bubbles measured in step 2).

2. The in situ detection method of claim 1, wherein, In step 1), at least one side of the electrolytic cell is provided with a transparent shell, and a camera on one side of the electrolytic cell is used to take pictures of the bubbles on the electrode surface to be measured.

3. The in situ detection method according to claim 1 or 2, wherein, In step 1), the top plate of the electrolytic cell is made of acrylic glass, and the materials of the other side plates are selected according to the characteristics of the electrochemical reaction, and are stainless steel or metal titanium with nickel plating on the surface.

4. The in-situ detection method of claim 1 or 2, wherein, In step 1), the contact angle of the bubble in a stable state is analyzed by a contact angle measuring instrument, and the analysis method comprises: using an optical imaging method, a current density is set to 0.1 mA / cm 2 The contact angle measuring instrument is placed on the side of the electrolytic cell at a distance of 10 cm from the electrolytic cell, and the contact angles of the bubbles on the electrode surface are measured respectively when the reaction is performed for 0.5, 1, 2, 3, 4, 5, 6, 8 and 10 hours; when the contact angle no longer changes during the test, the test is ended.

5. The method of claim 1, wherein the step of detecting is performed in situ. In step 1), the current density is controlled to achieve a single bubble observable current density control range of 0.1-0.5 mA / cm 2 .

6. The method of claim 1, wherein the step of detecting is performed in situ. In step 1), the flow rate of the electrolyte is controlled to realize that the bubble detachment is not affected by the electrolyte, and the flow rate of the electrolyte ranges from 2 to 10 L / min.

7. The method of claim 1, wherein the step of detecting is performed in situ. In step 2), the upper part of the electrolytic cell is an open structure, and the electrolyte above the electrode to be measured directly contacts the air through an opening.

8. The method of claim 1, wherein the step of detecting is performed in situ. In step 2) a lower current density is controlled, said current density ranging from 0.1 to 0.5 mA / cm 2 .

9. The method of claim 1, wherein the method is performed in situ. In step 2) the metal ring is slowly moved through the aperture towards the bubble at a rate of 0.01 to 0.05 mm s -1 , preferably 0.02 mm"1 s。 10. The method of in situ detection according to any one of claims 1 to 9, wherein, In step 3), the evaluation method comprises: the smaller the contact angle of the bubbles, the better the hydrophobicity or gas affinity of the electrode; the smaller the contact angle of the bubbles, the better the hydrophilicity or gas repellency of the electrode; and / or, the greater the adhesion value of the bubbles, the better the hydrophobicity or gas affinity of the electrode, and the smaller the adhesion value of the bubbles, the better the hydrophilicity or gas repellency of the electrode.

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