Double-cavity gaseous electrode testing device and application

Abstract

The invention belongs to the technical field of new energy electrode testing, and particularly relates to a double-cavity gaseous electrode testing device and application. The double-cavity gaseous electrode testing device is provided with a double-cavity electrolytic tank which is a three-electrode system and comprises a working electrode, a counter electrode and a reference electrode, a breather pipe, the working electrode and the counter electrode are sequentially arranged in a left cavity, deionized water is placed in the left cavity, the breather pipe is immersed in the deionized water but does not make contact with the bottom of the left cavity, and the reference electrode is arranged in the working electrode. The working electrode and the counter electrode are not immersed in the deionized water; the working electrode and the counter electrode are connected through a proton conductor to form a circuit, a reference electrode and an electrolyte solution are arranged in the right cavity, and the other end of the proton conductor in the left cavity is immersed in the electrolyte solution in the right cavity to form a circuit loop with the reference electrode immersed in the electrolyte solution. The contact between the catalyst and the electrolyte solution can be avoided, the influence of anion adsorption in the electrolyte solution is eliminated, and the reaction and structure change on the catalytic interface of the working electrode can be efficiently and accurately obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy electrode testing, and in particular relates to a dual-cavity gas electrode testing device and its application. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) are a clean, efficient energy conversion technology that has attracted significant attention due to their zero-emission characteristics. To reduce costs and promote the commercialization of PEMFCs, researchers are working to reduce the Pt content in the catalyst layer while simultaneously increasing Pt utilization. However, reducing Pt content can lead to more severe Pt surface poisoning by adsorbates such as carbon monoxide, sulfur dioxide, sulfonates, and Pt oxides. On the one hand, gases such as carbon monoxide and sulfur dioxide poison the anode Pt surface primarily due to impure hydrogen. On the other hand, Nafion, a commonly used material in PEMFCs, has side-chain sulfonate anions that adsorb on the cathode Pt catalyst surface. This adsorption not only hinders oxygen transport but also leads to the loss of Pt active sites, causing activation polarization and severely impacting cell performance. Accurately quantifying catalyst activity and the amount of species adsorbed on the Pt interface is crucial for optimizing battery performance and selecting suitable catalytic materials. Currently, the most common indicators of catalyst activity include electrochemically active area, mass-specific activity, and area-specific activity. Pt interface species adsorption primarily focuses on the adsorption of anionic sulfonates. These characterizations currently rely primarily on two technology platforms: the MEA (Mechanical Electrochemical Assembly) and the rotating disk electrode (RDE). The MEA more accurately reflects actual battery operating conditions. However, this testing method requires specialized fuel cell test benches, which not only increases experimental complexity but also significantly increases the time and cost burden of research and development. While the RDE test platform requires minimal catalyst and is simple to operate, it requires an electrolyte solution to conduct protons. Anions in the electrolyte solution can adsorb on the Pt surface, altering the electrode surface properties, promoting hydrogen peroxide production, and impacting the activity of the Pt catalyst. Furthermore, the most commonly used electrolyte is perchlorate, making it difficult to separate the adsorption behavior of perchlorate and sulfonate ions on the electrode surface. This further complicates the accurate measurement of the amount of sulfonate adsorption. This adsorption competition not only affects the adsorption characteristics of sulfonate ions, but may also mask their true behavior in electrochemical reactions, thus posing a challenge to the accuracy and reliability of experimental results.

[0003] In summary, the characterization methods in the existing technologies all have some limitations and disadvantages. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention provides a dual-chamber gas electrode testing device and its application. This device, constructed with a dual-chamber gas electrode, performs working electrode catalytic interface testing. This device eliminates the need for a fuel cell test bench, avoids contact between the catalyst and the electrolyte solution, and eliminates the effects of anion adsorption in the electrolyte solution, efficiently and accurately capturing reactions and structural changes at the working electrode catalytic interface.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: A double-chamber gas electrode testing device is provided, which is provided with a double-chamber electrolytic cell (4) and is a three-electrode system. The three-electrode system includes three electrodes: a working electrode (1), a counter electrode (2), and a reference electrode (3). A vent tube (7), a working electrode, and a counter electrode are sequentially arranged in the left chamber of the double-chamber electrolytic cell. Deionized water is placed in the left chamber. The vent tube is immersed in the deionized water but does not touch the bottom of the left chamber. The working electrode and the counter electrode are not immersed in the deionized water. The working electrode and the counter electrode are connected by a proton conductor (6) to form a circuit. A reference electrode and an electrolyte solution (5) are arranged in the right chamber of the double-chamber electrolytic cell. The other end of the proton conductor in the left chamber is immersed in the electrolyte solution in the right chamber to form a circuit loop with the reference electrode (3) immersed in the electrolyte solution.

[0006] According to the above scheme, the working electrode (1) has a Pt catalytic interface; the working electrode is a Pt electrode or a glassy carbon electrode coated with a Pt nanocatalyst electrode.

[0007] According to the above scheme, the counter electrode (2) is a Pt black electrode, and the reference electrode (3) can be a hydrogen electrode, a silver / silver chloride electrode or a mercury|mercury oxide electrode.

[0008] According to the above solution, the proton conductor provides a path for protons and can be a homogeneous membrane.

[0009] According to the above scheme, the gas passes through the electrolyte via the ventilation tube, and a large flow of humidification bubbles is derived to humidify the working electrode to improve the proton conductivity.

[0010] According to the above scheme, the electrolyte solution can be a perchloric acid solution or a sulfuric acid solution, and its concentration is 0.1-0.5 mol / L.

[0011] A second aspect of the present invention provides a method for characterizing a Pt interface based on the above-mentioned dual-cavity gas electrode testing device, comprising the following steps: (1) Deionized water is placed in the left cavity, and high-purity nitrogen is introduced to remove the air in the deionized water in the left cavity; (2) Construct a three-electrode system and perform CV scanning activation to remove adsorbed impurities on the working electrode surface; (3) Characterize the Pt interface of the working electrode.

[0012] According to the above scheme, the CV scanning activation in step (2) is to scan and activate the working electrode by cyclic scanning voltammetry at a potential scanning rate of 50-200 mV / s.

[0013] According to the above scheme, the test is a CV cyclic sweep voltammetry test, an LSV linear sweep voltammetry test or a charge substitution test.

[0014] According to the above scheme, the CV cyclic scanning voltammetry curve test is as follows: the water in the left cavity where the working electrode is located is saturated with nitrogen, and the working electrode is subjected to a cyclic scanning voltammetry test at a potential scanning rate of 20-50 mV / s at 0-1.2 V to obtain the electrochemical active area and then obtain the roughness.

[0015] According to the above scheme, the LSV linear sweep voltammetry curve test is as follows: under the condition of oxygen saturation in the water in the left cavity where the working electrode is located, a linear sweep voltammetry test is performed on the working electrode at a potential sweep rate of 2 mv / s in the range of 0-1.2V to obtain the half-wave potential, mass specific activity or area specific activity.

[0016] According to the above scheme, the charge substitution test is performed under nitrogen-saturated conditions in the left chamber where the working electrode is located. CO replaces sulfonate groups at a constant potential of 0.54 V. Nitrogen is first introduced, then CO is introduced. The test is continued for a period of time, and the response current is observed until the current stabilizes, indicating completion of the substitution reaction. The current is then integrated over time to obtain the substitution reaction charge. The substitution reaction charge obtained through the charge substitution test is used to determine the degree of sulfonate group coverage. A greater charge indicates greater sulfonate group coverage, indicating a greater loss of active sites on the Pt surface and a greater degree of Pt surface poisoning.

[0017] The beneficial effects of the present invention are: The dual-cavity gas electrode testing device of the present invention can be used to perform quantitative testing of the Pt interface by configuring a three-electrode system without the need for an expensive fuel cell test bench. Generally speaking, since the electrolyte solution is used to provide protons for the surface reaction of the working electrode, the traditional electrolytic cell device places the working electrode and the electrolyte in the same cavity. The anions in the electrolyte solution will be adsorbed on the active surface of the working electrode, resulting in a decrease in the active area of ​​the active working electrode, which is not conducive to obtaining the true activity. The dual-cavity gas electrode device of the present invention utilizes a dual-cavity environment to separate the working electrode from the electrolyte solution, thereby avoiding the influence of anion adsorption in the electrolyte solution. At the same time, the working electrode and the electrolyte are connected by a proton conductor to provide protons for the surface reaction of the working electrode, thereby achieving efficient and accurate acquisition of the reaction and structural changes on the interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the dual-cavity gas electrode testing device of the present invention.

[0019] Figure 2 This is the cyclic sweep voltammetry test diagram of Example 1.

[0020] Figure 3 This is the linear sweep voltammetry test diagram of Example 2 Figure 4 This is a diagram of CO substituted sulfonate in Example 3. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] Example 1 like Figure 1 As shown, a double-chamber gas electrode test device is provided with a double-chamber electrolytic cell (7), which is a three-electrode system. The three-electrode system includes three electrodes: a working electrode (1), a counter electrode (2), and a reference electrode (3). The left chamber of the double-chamber electrolytic cell is sequentially provided with a vent tube (7), a working electrode (1), and a counter electrode (2). The vent tube (7) is immersed in deionized water but does not contact the working electrode (1) and the counter electrode (2). The working electrode (1) and the counter electrode (2) are connected by a proton conductor (6) to form a circuit. The proton conductor provides a path for protons and can be a Nafion membrane. The right chamber of the double-chamber electrolytic cell is provided with a reference electrode (3) and an electrolyte solution (5). The other end of the proton conductor (6) in the left chamber is immersed in the electrolyte solution (5) in the right chamber, forming a circuit loop with the reference electrode (3) immersed in the electrolyte solution (5). Specifically, the working electrode (1) is a Pt electrode, the counter electrode (2) is a Pt black electrode, and the reference electrode (3) is a hydrogen electrode.

[0023] Furthermore, in one embodiment, the vent pipe is provided with an air outlet for maintaining the air pressure balance of the device. The air outlet is closed during air intake.

[0024] All electrochemical tests were performed at room temperature in an electrochemical workstation. Deionized water was placed in the left chamber of a dual-chamber electrolytic cell (4), and 0.1 mol / L perchloric acid solution was placed in the right chamber (5). A hydrogen electrode was used as the reference electrode (3), a platinum black electrode was used as the counter electrode (2), and these electrodes, along with the working electrode (1), formed a three-electrode system.

[0025] Preparation of working electrode: A platinum disk electrode was ultrasonically cleaned in deionized water and isopropanol for 5 minutes each. A sufficient amount of Nafion solution (ionomer) was dripped onto the surface of the Pt disk electrode and dried under light until nearly dry. A homogeneous membrane was then placed over the quick-drying Nafion solution to ensure a connection between the membrane and the platinum disk. After the connection was complete, the platinum disk electrode was dried until the Nafion solution was completely dry and tightly bonded to the homogeneous membrane. After the platinum disk working electrode was prepared, Nafion solution was dripped onto the platinum counter electrode to connect the counter electrode to the homogeneous membrane and then dried. After the working and counter electrodes were connected, they were placed in a clean, deionized water-filled electrolytic cell in the left chamber. The other end of the homogeneous membrane connected to the counter electrode was connected to the perchloric acid solution in the right chamber. The electrode and device were then prepared.

[0026] (1) High-purity nitrogen was introduced for half an hour to remove the air from the deionized water. The prepared electrode was activated by cyclic scanning voltammetry at a scanning rate of 0.05-0.1 V / s in the potential range of 0-1.2 V to remove the adsorbed impurities on the electrode surface.

[0027] (2) Then the cyclic sweep voltammetry test was performed at a scan rate of 0.02 V / s. The test results are shown in Figure 2 , through the formula , where S1 is the integrated area of ​​hydrogen adsorption or desorption on Pt, in A·V; 2.1 is the amount of electricity required for hydrogen adsorption or desorption on an ideal smooth Pt electrode surface, C / m 2 ; v is the scanning speed, unit is V / s; S2 is the geometric area of ​​the Pt disk, unit is m 2 The roughness Rf is 0.907, indicating that the active area obtained by this method is almost consistent with the actual geometric area.

[0028] Example 2: The preparation of the dual-cavity gas electrode testing device and the working electrode is consistent with that in Example 1.

[0029] (1) High-purity nitrogen was introduced for half an hour to remove the air from the deionized water. The prepared electrode was subjected to cyclic scanning voltammetry at a scanning rate of 0.1-0.05 V / s in the potential range of 0-1.2 V to remove the adsorbed impurities on the electrode surface.

[0030] (2) Then, high-purity oxygen was introduced into the deionized water for half an hour to ensure that it was saturated with oxygen. Linear sweep voltammetry was performed at a scan rate of 0.02 V / s. The test results are shown in Figure 3 , first use the formula , where I k@0.9V is the kinetic current at 0.9 V, in mA; I@0.9V is the apparent current at 0.9V, in mA; I @0.4V is the apparent current at 0.4V, in mA, and the kinetic current I at 0.9V is obtained. k@0.9V is 0.004mA, and then using the formula , where SA is the area specific activity, unit A / m 2 Pt ;M Pt is the mass of Pt, in g; I k@0.9V is the kinetic current at 0.9 V, in A; S1 is the electrochemical active area, in m 2 / g Pt The area specific activity SA was 0.225 A / m 2 Pt .

[0031] Example 3: The preparation of the dual-cavity gas electrode testing device and the working electrode is consistent with that in Example 1.

[0032] (1) High-purity nitrogen was introduced for half an hour to remove the air from the deionized water. The prepared electrode was activated by cyclic scanning voltammetry at a scanning rate of 0.1-0.05 V / s in the potential range of 0-1.2 V to remove the adsorbed impurities on the electrode surface.

[0033] (2) High-purity nitrogen was introduced for half an hour to remove the air from the deionized water, and the CO substitution reaction for sulfonate was carried out under nitrogen saturation conditions. The test was carried out at a constant potential of 0.54 V and the time was set to 1000 s. When the program was carried out for 500 s, the nitrogen was stopped and replaced with carbon monoxide gas. The response current was observed until the current stabilized. The substitution reaction was completed. Figure 4 After the experiment, the current was integrated over time to obtain a substitution reaction charge of 13.6 μC. The sulfonate coverage can be determined by the ratio of the substitution reaction charge to the H adsorption or desorption charge on the Pt surface.

[0034] Compared with the experimental results of directly using a single-chamber electrolytic cell with direct contact between the working electrode and the electrolyte, this method avoids the adsorption of other anions on the Pt surface, and can obtain the obvious reaction charge of CO replacing sulfonate, thereby measuring the degree of occupation of the active area of ​​the Pt interface.

[0035] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A dual-cavity gas electrode testing device, characterized in that: A double-chamber electrolytic cell is provided, which is a three-electrode system. The three-electrode system includes three electrodes: a working electrode, a counter electrode, and a reference electrode. A vent tube, a working electrode, and a counter electrode are sequentially arranged in the left chamber of the double-chamber electrolytic cell. Deionized water is placed in the left chamber. The vent tube is immersed in the deionized water but does not touch the bottom of the left chamber. The working electrode and the counter electrode are not immersed in the deionized water. The working electrode and the counter electrode are connected by a proton conductor to form a circuit. A reference electrode and an electrolyte solution are arranged in the right chamber of the double-chamber electrolytic cell. The other end of the proton conductor in the left chamber is immersed in the electrolyte solution in the right chamber, forming a circuit loop with the reference electrode immersed in the electrolyte solution.

2. The dual-cavity gas electrode testing device according to claim 1, characterized in that: The working electrode (1) has a Pt catalytic interface; the working electrode is a Pt electrode or a glassy carbon electrode coated with a Pt nanocatalyst electrode.

3. The dual-cavity gas electrode testing device according to claim 2, characterized in that: The working electrode is a Pt electrode, the counter electrode is a Pt black electrode, and the reference electrode is a hydrogen electrode, a silver / silver chloride electrode, or a mercury|mercury oxide electrode.

4. The dual-cavity gas electrode testing device according to claim 1, characterized in that: The gas passes through the electrolyte via the vent tube, and a large flow of humidification bubbles is derived to humidify the working electrode to improve the proton conductivity.

5. The dual-cavity gas electrode testing device according to claim 1, wherein: The proton conductor provides a path for protons and is a homogeneous membrane; the electrolyte solution is a perchloric acid solution or a sulfuric acid solution, and its concentration is 0.1-0.5 mol / L.

6. A method for characterizing a Pt interface based on the dual-cavity gas electrode testing apparatus of claim 1, comprising the following steps: (1) Deionized water is placed in the left cavity, and high-purity nitrogen is introduced to remove the air in the deionized water in the left cavity; (2) Construct a three-electrode system and perform CV scanning activation to remove adsorbed impurities on the electrode surface; (3) Characterize the Pt interface of the working electrode.

7. The method according to claim 6, characterized in that: The CV scanning activation is: scanning and activating the working electrode by cyclic scanning voltammetry at a potential scanning rate of 50-200 mV / s; the Pt interface characterization is CV cyclic scanning voltammetry curve test, LSV linear scanning voltammetry curve test or charge substitution test.

8. The method according to claim 7, wherein: The CV cyclic scanning voltammetry curve test is as follows: the water in the left cavity where the working electrode is located is saturated with nitrogen, and the working electrode is subjected to a cyclic scanning voltammetry test at a potential scanning rate of 20-50 mV / s at 0-1.2 V to obtain the electrochemical active area and then the roughness.

9. The method according to claim 7, wherein: The LSV linear sweep voltammetry curve test is as follows: under the condition of oxygen saturation in the water in the left cavity where the working electrode is located, a linear sweep voltammetry test is performed on the working electrode at a potential sweep rate of 2mv / s in the range of 0-1.2V to obtain the half-wave potential, mass specific activity or area specific activity.

10. The method according to claim 7, wherein: The charge substitution test is as follows: water in the left cavity where the working electrode is located is saturated with nitrogen, and CO replaces sulfonate at a constant potential of 0.54 V: nitrogen is first passed, then switched to CO, and the test is continued for a period of time. The response current is observed until the current stabilizes and the substitution reaction is completed. The current is integrated with time to obtain the substitution reaction charge.

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